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How many heavy chains are present in a myosin molecule? A) One B) Two C) Three D) Four E) Five
B) Two Explanation: A myosin molecule is composed of two heavy chains that form a complex, which is essential for its function in muscle contraction.
What is the primary function of autonomic neurotransmitters? A) To regulate voluntary muscle movements B) To maintain homeostasis of the body C) To enhance conscious thought processes D) To control sensory perception E) To facilitate digestion only
B) To maintain homeostasis of the body Explanation: Autonomic neurotransmitters play a crucial role in regulating unconscious autonomic functions, which are essential for maintaining homeostasis, such as heart rate and blood pressure.
1/104
p.17
Physiology of Smooth Muscle Contraction

How many heavy chains are present in a myosin molecule?
A) One
B) Two
C) Three
D) Four
E) Five

B) Two
Explanation: A myosin molecule is composed of two heavy chains that form a complex, which is essential for its function in muscle contraction.

p.1
Neurotransmitters and Receptors in ANS

What is the primary function of autonomic neurotransmitters?
A) To regulate voluntary muscle movements
B) To maintain homeostasis of the body
C) To enhance conscious thought processes
D) To control sensory perception
E) To facilitate digestion only

B) To maintain homeostasis of the body
Explanation: Autonomic neurotransmitters play a crucial role in regulating unconscious autonomic functions, which are essential for maintaining homeostasis, such as heart rate and blood pressure.

p.9
Sympathetic Nervous System Anatomy and Function

What is the primary response of the sympathetic nervous system during a 'fight or flight' situation?
A) Decrease in heart rate
B) General activation of the sympathetic nervous system
C) Increase in digestive activity
D) Decrease in blood pressure
E) Increase in sleepiness

B) General activation of the sympathetic nervous system
Explanation: The sympathetic nervous system is generally activated during 'fight or flight' responses, preparing the body to respond to threats by increasing physiological functions such as heart rate and blood pressure.

p.18
Calcium Regulation in Smooth Muscle

What activates Myosin Light Chain Kinase (MLCK)?
A) Decrease in intracellular calcium
B) Calcium-calmodulin complex
C) Phosphatase activity
D) Myosin phosphorylation
E) ATP depletion

B) Calcium-calmodulin complex
Explanation: MLCK is activated by an increase in intracellular calcium levels, which leads to the formation of a calcium-calmodulin complex that activates MLCK, facilitating muscle contraction.

p.17
Calcium Regulation in Smooth Muscle

What enzyme mediates the phosphorylation of myosin light chains?
A) Myosin light chain phosphatase
B) Myosin light chain kinase (MLCK)
C) Protein kinase A
D) Calcium-calmodulin dependent kinase
E) Phospholipase C

B) Myosin light chain kinase (MLCK)
Explanation: MLCK is the enzyme responsible for phosphorylating myosin light chains, which is a critical step in the contraction process of smooth muscle.

p.12
Calcium Regulation in Smooth Muscle

What is the role of calcium ions ([Ca2+]) in smooth muscle contraction?
A) They inhibit contraction
B) They are not involved in contraction
C) They are critical regulators of contraction
D) They only affect skeletal muscle
E) They are stored in T tubules

C) They are critical regulators of contraction
Explanation: Calcium ions ([Ca2+]) play a crucial role in regulating contraction in smooth muscle, similar to their role in skeletal muscle contraction.

p.10
Autonomic Nervous System (ANS) Overview

In the context of the autonomic nervous system, which systems are considered counteracting?
A) Sympathetic and parasympathetic systems
B) Central and peripheral nervous systems
C) Sensory and motor systems
D) Somatic and autonomic systems
E) Endocrine and exocrine systems

A) Sympathetic and parasympathetic systems
Explanation: The sympathetic and parasympathetic systems of the autonomic nervous system are classic examples of counteracting systems, as they have opposing effects on bodily functions.

p.17
Physiology of Smooth Muscle Contraction

What are the main components of thin myofilaments in smooth muscle contraction?
A) Myosin and tropomyosin
B) Actin and tropomyosin
C) Myosin and actin
D) Heavy chains and light chains
E) Myosin light chain and heavy chain

B) Actin and tropomyosin
Explanation: Thin myofilaments in smooth muscle consist primarily of actin and tropomyosin, which play crucial roles in muscle contraction.

p.13
Physiology of Smooth Muscle Contraction

What does the red color represent in the context of smooth muscle contraction?
A) Normally contracted state
B) Fully relaxed then fully contracted
C) Partial tone
D) Resting state
E) Stimulated relaxation

B) Fully relaxed then fully contracted
Explanation: The red color indicates a state where the smooth muscle is fully relaxed and then fully contracted, demonstrating the transition between these two states over time.

p.12
Physiology of Smooth Muscle Contraction

What anchors the thin filaments in smooth muscle cells?
A) Z lines
B) Dense bodies and plasma membrane
C) T tubules
D) Myofibrils
E) Sarcomeres

B) Dense bodies and plasma membrane
Explanation: In smooth muscle, thin filaments are anchored to dense bodies and the plasma membrane, unlike skeletal muscle which has Z lines.

p.18
Mechanisms of Signal Termination in ANS

Which enzyme is responsible for dephosphorylating MLC-P?
A) MLCK
B) Calcium-calmodulin
C) Phosphatase
D) ATPase
E) Kinase

C) Phosphatase
Explanation: Phosphatase is the enzyme responsible for dephosphorylating MLC-P, which is necessary for muscle relaxation and the cessation of contraction.

p.12
Differences Between Multiunit and Single-unit Smooth Muscle

What is a distinguishing feature of smooth muscle regarding its structure?
A) Presence of T tubules
B) Striated fibers
C) Gap junctions connecting cells
D) Presence of Z lines
E) Large myofibrils

C) Gap junctions connecting cells
Explanation: Smooth muscle cells are connected by gap junctions, which facilitate communication and coordinated contraction, a feature not present in skeletal muscle.

p.19
Calcium Regulation in Smooth Muscle

What initiates the contraction of smooth muscle cells?
A) Decrease in calcium levels
B) Binding of calcium to calmodulin
C) Activation of myosin light chain phosphatase
D) Increase in sodium levels
E) Decrease in potassium levels

B) Binding of calcium to calmodulin
Explanation: The contraction of smooth muscle cells is initiated by the increase of calcium levels in the cell, which leads to the binding of calcium to calmodulin, triggering a series of events that result in muscle contraction.

p.22
Physiology of Smooth Muscle Contraction

What is the relationship between cGMP and smooth muscle relaxation?
A) cGMP decreases calcium sensitivity
B) cGMP activates Rho-kinase
C) cGMP inhibits MLCK
D) cGMP induces contraction
E) cGMP has no effect on smooth muscle

A) cGMP decreases calcium sensitivity
Explanation: cGMP, through NO-dependent activation, decreases calcium sensitivity, promoting relaxation of smooth muscle by activating phosphatase.

p.15
Calcium Regulation in Smooth Muscle

What is the role of Ca2+ in the plateau phase of smooth muscle contraction?
A) It inhibits K+ channels
B) It activates K+ channels
C) It blocks Na+ channels
D) It induces hyperpolarization
E) It has no role

B) It activates K+ channels
Explanation: In the plateau phase, Ca2+ activates K+ channels, which is crucial for maintaining the plateau phase of the action potential in smooth muscle cells.

p.18
Physiology of Smooth Muscle Contraction

What is the role of Myosin Light Chain (MLC) in smooth muscle contraction?
A) It inhibits muscle contraction
B) It is phosphorylated by MLCK
C) It is responsible for calcium storage
D) It binds to actin
E) It is a type of calcium channel

B) It is phosphorylated by MLCK
Explanation: Myosin Light Chain (MLC) is phosphorylated by Myosin Light Chain Kinase (MLCK), which is a crucial step in the process of smooth muscle contraction.

p.12
Differences Between Multiunit and Single-unit Smooth Muscle

What is a unique morphological characteristic of smooth muscle cells?
A) Multinucleated cells
B) Striated appearance
C) Presence of Z lines
D) Uninucleated small cells
E) Presence of T tubules

D) Uninucleated small cells
Explanation: Smooth muscle cells are characterized by being uninucleated and small, which distinguishes them from skeletal muscle cells that are typically multinucleated and larger.

p.10
Autonomic Nervous System (ANS) Overview

What does the term 'counteracting systems' refer to in a biological context?
A) Systems that work independently
B) Systems that enhance each other's functions
C) Systems that oppose each other
D) Systems that are identical
E) Systems that are unrelated

C) Systems that oppose each other
Explanation: Counteracting systems refer to biological systems that work against each other to maintain balance or homeostasis, indicating a complex interaction rather than a simple relationship.

p.22
Calcium Regulation in Smooth Muscle

How does Rho-kinase affect calcium sensitivity in smooth muscle?
A) It decreases calcium sensitivity
B) It has no effect on calcium sensitivity
C) It increases calcium sensitivity
D) It completely inhibits calcium use
E) It only affects calcium levels indirectly

C) It increases calcium sensitivity
Explanation: When Rho-kinase is active, it increases calcium sensitivity, meaning less intracellular calcium is needed to induce the same contraction, enhancing the muscle's responsiveness.

p.5
Neurotransmitters and Receptors in ANS

What does the dynamic expression pattern of receptors imply?
A) Receptors are always present in the same quantity
B) Receptor levels can change based on various factors
C) Receptors are only expressed in certain diseases
D) Receptors do not respond to external stimuli
E) Receptors are static and unchanging

B) Receptor levels can change based on various factors
Explanation: The dynamic expression pattern of receptors indicates that their levels can fluctuate in response to different stimuli, including age and hormonal changes.

p.16
Calcium Regulation in Smooth Muscle

Which ion is crucial for the contraction of smooth muscle cells?
A) Na+
B) K+
C) Cl-
D) Ca2+
E) Mg2+

D) Ca2+
Explanation: Calcium (Ca2+) is an important regulator in smooth muscle contraction, as its release into the cytoplasm is essential for initiating the contraction process.

p.8
Sympathetic Nervous System Anatomy and Function

What type of neuron is the adrenal medulla classified as?
A) Sensory neuron
B) Motor neuron
C) Modified postganglionic neuron
D) Preganglionic neuron
E) Interneuron

C) Modified postganglionic neuron
Explanation: The adrenal medulla is classified as a modified postganglionic neuron, which plays a crucial role in the sympathetic nervous system by releasing epinephrine.

p.1
Neurotransmitters and Receptors in ANS

How many synapses are involved in the autonomic nervous system pathway?
A) One
B) Two
C) Three
D) Four
E) Five

B) Two
Explanation: The autonomic nervous system pathway involves two synapses: one between the preganglionic and postganglionic neurons, and the other between the postganglionic neuron and the target cell.

p.20
Mechanisms of Signal Termination in ANS

What is the effect of phosphorylating IP3R on calcium entry into the cell?
A) It increases calcium entry
B) It has no effect on calcium entry
C) It inhibits calcium entry
D) It promotes calcium release from the mitochondria
E) It enhances calcium sensitivity

C) It inhibits calcium entry
Explanation: Phosphorylation of IP3R leads to the inhibition of calcium entry into the cell, which is crucial for inducing relaxation in smooth muscle.

p.13
Physiology of Smooth Muscle Contraction

What does the green color indicate regarding smooth muscle state?
A) Fully relaxed
B) Normally contracted resting state
C) Fully contracted
D) Stimulated relaxation
E) Partial tone

B) Normally contracted resting state
Explanation: The green color represents a normally contracted resting state of smooth muscle, which can relax upon receiving a signal and then contract again.

p.13
Physiology of Smooth Muscle Contraction

What is indicated by the blue color in smooth muscle contraction?
A) Fully relaxed state
B) Normally contracted resting state
C) Partial tone with increasing contraction
D) Fully contracted state
E) Complete relaxation

C) Partial tone with increasing contraction
Explanation: The blue color signifies a normally partial tone in smooth muscle, indicating that there is an ongoing contraction that can be increased, followed by stimulation for relaxation.

p.13
Physiology of Smooth Muscle Contraction

Which of the following is an example of smooth muscle that is normally contracted?
A) Esophagus
B) Urinary bladder
C) Sphincters
D) Airway
E) Blood vessel

C) Sphincters
Explanation: Sphincters are examples of smooth muscle that are normally contracted and can relax upon receiving a signal, demonstrating their role in regulating passage through various bodily openings.

p.22
Calcium Regulation in Smooth Muscle

What happens when Rho-kinase inhibits phosphatase?
A) It decreases contraction strength
B) It increases MLCP activity
C) It enhances MLC phosphorylation
D) It promotes relaxation
E) It reduces calcium sensitivity

C) It enhances MLC phosphorylation
Explanation: When Rho-kinase inhibits phosphatase, it leads to increased phosphorylation of MLC, which contributes to stronger contractions in smooth muscle.

p.4
Neurotransmitters and Receptors in ANS

What is a characteristic feature of neurotransmitter release from postganglionic autonomic axons?
A) 1-1 transmission
B) Varicosity with neurotransmitter vesicles
C) Direct synaptic connection
D) Release only in the central nervous system
E) No modulation by receptors

B) Varicosity with neurotransmitter vesicles
Explanation: Postganglionic autonomic axons typically exhibit varicosities containing neurotransmitter vesicles, allowing for the release of neurotransmitters over a larger area, affecting multiple target cells rather than a single one.

p.6
Neurotransmitters and Receptors in ANS

What is the primary neurotransmitter in both the sympathetic and parasympathetic divisions of the autonomic nervous system?
A) Norepinephrine
B) Serotonin
C) Acetylcholine
D) Dopamine
E) GABA

C) Acetylcholine
Explanation: Acetylcholine is the primary neurotransmitter used in both the sympathetic and parasympathetic divisions of the autonomic nervous system, playing a crucial role in signal transmission.

p.3
Neurotransmitters and Receptors in ANS

Which neurotransmitter is primarily released at the second synapse in the sympathetic nervous system?
A) Acetylcholine (ACh)
B) Norepinephrine (NE)
C) Serotonin
D) GABA
E) Glutamate

B) Norepinephrine (NE)
Explanation: In the sympathetic nervous system, norepinephrine (NE) is primarily released at the second synapse, acting on adrenergic receptors.

p.15
Physiology of Smooth Muscle Contraction

How does TTX affect action potentials in smooth muscle cells?
A) It completely blocks them
B) It enhances them
C) It has no effect
D) It only affects calcium channels
E) It only affects potassium channels

C) It has no effect
Explanation: TTX is a specific inhibitor of voltage-gated sodium channels and does not affect smooth muscle cells because they do not rely on these channels for action potential generation.

p.1
Autonomic Nervous System (ANS) Overview

Which of the following autonomic functions is NOT regulated by the autonomic nervous system?
A) Heart rate
B) Pupillary response
C) Blood pressure
D) Voluntary muscle movement
E) Digestive processes

D) Voluntary muscle movement
Explanation: The autonomic nervous system regulates unconscious functions such as heart rate, blood pressure, and pupillary response, while voluntary muscle movements are controlled by the somatic nervous system.

p.20
Role of cAMP and cGMP in Smooth Muscle Relaxation

How does cAMP induce relaxation in smooth muscle?
A) By increasing calcium sensitivity
B) By inducing phosphorylation of MLCK by PKA
C) By decreasing MLCK activity
D) By activating calcium channels
E) By promoting calcium entry

B) By inducing phosphorylation of MLCK by PKA
Explanation: cAMP induces relaxation by phosphorylating MLCK through PKA, which results in decreased calcium sensitivity and promotes relaxation of smooth muscle.

p.20
Role of cAMP and cGMP in Smooth Muscle Relaxation

What role does cGMP play in smooth muscle relaxation?
A) It activates calcium channels
B) It induces phosphorylation of MLCK
C) It activates phosphatase
D) It increases calcium entry
E) It decreases MLCK activity

C) It activates phosphatase
Explanation: cGMP is involved in smooth muscle relaxation by activating phosphatase, which helps in the dephosphorylation processes that lead to relaxation.

p.20
Differences Between Multiunit and Single-unit Smooth Muscle

What distinguishes multiunit smooth muscle from single-unit smooth muscle?
A) Multiunit smooth muscle has a single innervation
B) Single-unit smooth muscle contracts independently
C) Each smooth muscle cell in multiunit has its own innervation
D) Multiunit smooth muscle is found only in the heart
E) Single-unit smooth muscle has multiple innervations

C) Each smooth muscle cell in multiunit has its own innervation
Explanation: In multiunit smooth muscle, each smooth muscle cell has its own innervation, allowing for more precise control of contraction compared to single-unit smooth muscle, which contracts as a single unit.

p.20
Mechanisms of Signal Termination in ANS

What is the primary mechanism by which phosphorylation of IP3 limits calcium entry into the cell?
A) By increasing MLCK activity
B) By activating calcium channels
C) By inducing relaxation
D) By decreasing calcium sensitivity
E) By promoting calcium release from the sarcoplasmic reticulum

C) By inducing relaxation
Explanation: The phosphorylation of IP3 limits calcium entry into the cell, which induces relaxation in smooth muscle, highlighting the importance of this mechanism in muscle physiology.

p.10
Autonomic Nervous System (ANS) Overview

What is a key outcome of the interaction between counteracting systems?
A) Increased simplicity in function
B) Maintenance of homeostasis
C) Complete independence
D) Elimination of all signals
E) Uniform response to stimuli

B) Maintenance of homeostasis
Explanation: The interaction of counteracting systems is crucial for maintaining homeostasis in the body, as they balance each other's effects to regulate physiological processes.

p.16
Neurotransmitters and Receptors in ANS

What happens when a ligand binds to an α1 adrenergic receptor in smooth muscle?
A) It causes hyperpolarization
B) It activates PLC and leads to calcium signaling
C) It inhibits contraction
D) It decreases membrane potential
E) It prevents calcium release

B) It activates PLC and leads to calcium signaling
Explanation: When a ligand binds to an α1 adrenergic receptor, it activates phospholipase C (PLC), which triggers a signaling cascade that results in calcium release, promoting contraction.

p.3
Neurotransmitters and Receptors in ANS

What type of receptor is found on the postganglionic neuron in the first synapse?
A) Muscarinic acetylcholine receptor (mAChR)
B) Nicotinic acetylcholine receptor (nAChR)
C) Adrenergic receptor
D) Dopaminergic receptor
E) GABA receptor

B) Nicotinic acetylcholine receptor (nAChR)
Explanation: The postganglionic receptor at the first synapse is the nicotinic acetylcholine receptor (nAChR), which is ligand-gated and responds to acetylcholine.

p.1
Neurotransmitters and Receptors in ANS

What is the pathway of signal transmission in the autonomic nervous system?
A) Sensory neuron ⇒ CNS ⇒ Target cell
B) Preganglionic neuron ⇒ Postganglionic neuron ⇒ Target cell
C) Motor neuron ⇒ Target cell
D) CNS ⇒ Target cell
E) Postganglionic neuron ⇒ Preganglionic neuron ⇒ CNS

B) Preganglionic neuron ⇒ Postganglionic neuron ⇒ Target cell
Explanation: The pathway in the autonomic nervous system involves a preganglionic neuron from the CNS that synapses with a postganglionic neuron in a peripheral ganglion, which then connects to the target cell.

p.17
Calcium Regulation in Smooth Muscle

What is the role of myosin light chains in smooth muscle?
A) They bind to actin
B) They provide structural support
C) They are phosphorylated to enable actin-myosin binding
D) They form the thick filament
E) They inhibit muscle contraction

C) They are phosphorylated to enable actin-myosin binding
Explanation: Myosin light chains (MLC) are phosphorylated, which allows for the binding of actin and myosin, facilitating muscle contraction.

p.9
Sympathetic Nervous System Anatomy and Function

In a 'fight or flight' response, what happens to blood vessels in skeletal muscle?
A) They constrict
B) They dilate
C) They remain unchanged
D) They become more permeable
E) They collapse

B) They dilate
Explanation: During a 'fight or flight' response, blood vessels in skeletal muscle dilate due to the action of epinephrine on β2 adrenergic receptors, allowing for increased blood flow and oxygen delivery to muscles.

p.10
Autonomic Nervous System (ANS) Overview

Why is the interaction of counteracting systems considered complex?
A) They operate in isolation
B) They have identical functions
C) They require multiple signals to function
D) They can influence each other in various ways
E) They are always in equilibrium

D) They can influence each other in various ways
Explanation: The complexity arises from the fact that counteracting systems can have multiple interactions and influences, making their regulation and function intricate rather than straightforward.

p.10
Autonomic Nervous System (ANS) Overview

Which of the following best describes a characteristic of counteracting systems?
A) They always work together
B) They are simple and predictable
C) They can create feedback loops
D) They are only found in the nervous system
E) They do not interact with other systems

C) They can create feedback loops
Explanation: Counteracting systems often create feedback loops that can enhance or inhibit their functions, contributing to the complexity of biological regulation.

p.2
Sympathetic Nervous System Anatomy and Function

What is the length of the postganglionic axon in the sympathetic nervous system?
A) Short
B) Long
C) Medium
D) Variable
E) None of the above

B) Long
Explanation: In the sympathetic nervous system, the postganglionic axon is long, extending from the ganglion, which is located close to the spinal cord, to the target organ.

p.14
Physiology of Smooth Muscle Contraction

What is the Bayliss effect?
A) Inhibition of smooth muscle contraction
B) Stretch-induced contraction of smooth muscle
C) Relaxation of blood vessels
D) Decrease in intracellular calcium
E) Increase in heart rate

B) Stretch-induced contraction of smooth muscle
Explanation: The Bayliss effect refers to the phenomenon where stretching of smooth muscle, such as in blood vessels, induces contraction due to the activation of mechanosensitive ion channels.

p.11
Sympathetic Nervous System Anatomy and Function

What is the primary function of the α1 adrenergic receptors in vascular smooth muscle?
A) Inducing vasodilation
B) Inducing vasoconstriction
C) Regulating heart rate
D) Stimulating gland secretion
E) Inhibiting muscle contraction

B) Inducing vasoconstriction
Explanation: The α1 adrenergic receptors in vascular smooth muscle primarily induce vasoconstriction, which is a key function of the sympathetic division in regulating blood flow.

p.4
Neurotransmitters and Receptors in ANS

What is the effect of neurotransmitter release from autonomic nerves on smooth muscle cells?
A) It only inhibits smooth muscle contraction
B) It has no effect on smooth muscle cells
C) It can stimulate or inhibit smooth muscle activity
D) It only stimulates skeletal muscle
E) It only affects cardiac muscle

C) It can stimulate or inhibit smooth muscle activity
Explanation: Autonomic nerves can release neurotransmitters that either stimulate or inhibit the activity of smooth muscle cells, demonstrating the diverse regulatory roles of the autonomic nervous system.

p.8
Sympathetic Nervous System Anatomy and Function

In the sympathetic nervous system, how is the length of the preganglionic neuron characterized?
A) Short
B) Long
C) Variable
D) Non-existent
E) Medium

B) Long
Explanation: In the sympathetic nervous system, the preganglionic neurons are characterized as long, which is a distinctive feature compared to other parts of the autonomic nervous system.

p.12
Physiology of Smooth Muscle Contraction

What is a key similarity between smooth muscle and skeletal muscle?
A) Both are striated
B) Both have uninucleated cells
C) Both involve thin and thick filaments sliding for contraction
D) Both have Z lines
E) Both do not require ATP for contraction

C) Both involve thin and thick filaments sliding for contraction
Explanation: Both smooth and skeletal muscles utilize the sliding filament mechanism involving thin and thick filaments to achieve contraction, despite other differences in their characteristics.

p.13
Differences Between Multiunit and Single-unit Smooth Muscle

How do smooth muscle cells differ across various organs?
A) They are all homogenous
B) They have the same contraction patterns
C) They are not a homogenous population
D) They only exist in the esophagus
E) They are identical in structure and function

C) They are not a homogenous population
Explanation: Smooth muscle cells are not a homogenous population; they exhibit many differences in structure and function depending on the organ they are found in.

p.17
Physiology of Smooth Muscle Contraction

What distinguishes the myosin light chains in smooth muscle from those in skeletal muscle?
A) They are larger in size
B) They have different subunits
C) They are absent in smooth muscle
D) They are more numerous
E) They do not bind to heavy chains

B) They have different subunits
Explanation: The myosin light chains in smooth muscle have different subunits compared to those found in skeletal muscle, which is important for their specific function in smooth muscle contraction.

p.7
Sympathetic Nervous System Anatomy and Function

What type of neurons are found in the adrenal medulla?
A) Sensory neurons
B) Modified, specific postganglionic neurons
C) Preganglionic neurons
D) Interneurons
E) Motor neurons

B) Modified, specific postganglionic neurons
Explanation: The adrenal medulla contains modified postganglionic neurons that have lost their axons, allowing them to release neurotransmitters directly into the bloodstream.

p.14
Mechanisms of Signal Termination in ANS

Which mechanism is NOT involved in increasing intracellular calcium levels in smooth muscle?
A) Depolarization from neighboring cells
B) Neural stimulation
C) Mechanical activation
D) Decreased membrane potential
E) Action potential generation

D) Decreased membrane potential
Explanation: Decreased membrane potential does not contribute to increasing intracellular calcium levels; rather, mechanisms like depolarization, neural stimulation, and mechanical activation are responsible for this increase.

p.16
Mechanisms of Signal Termination in ANS

What is a characteristic of pharmacomechanical activation in smooth muscle?
A) Requires a change in membrane potential
B) Induces contraction without changing membrane potential
C) Only occurs in skeletal muscle
D) Is dependent on external electrical stimulation
E) Involves only mechanical stretching

B) Induces contraction without changing membrane potential
Explanation: Pharmacomechanical activation allows for contraction of smooth muscle cells without a change in membrane potential, highlighting a unique regulatory mechanism.

p.11
Differences Between Multiunit and Single-unit Smooth Muscle

How do the sympathetic and parasympathetic divisions affect salivary glands?
A) Both produce viscous saliva
B) Both produce non-viscous saliva
C) Sympathetic produces viscous, mucinous saliva; parasympathetic produces non-viscous, enzyme-rich saliva
D) Both have no effect on salivary glands
E) Parasympathetic produces viscous saliva; sympathetic produces non-viscous saliva

C) Sympathetic produces viscous, mucinous saliva; parasympathetic produces non-viscous, enzyme-rich saliva
Explanation: The sympathetic division induces the production of viscous, mucinous saliva, while the parasympathetic division promotes the secretion of non-viscous, enzyme-rich saliva, highlighting their differing effects on the same target tissue.

p.3
Neurotransmitters and Receptors in ANS

What neurotransmitter is released by the preganglionic axon in both the parasympathetic and sympathetic systems?
A) Norepinephrine (NE)
B) Serotonin
C) Acetylcholine (ACh)
D) Dopamine
E) GABA

C) Acetylcholine (ACh)
Explanation: The preganglionic axon in both the parasympathetic and sympathetic nervous systems releases acetylcholine (ACh) as its neurotransmitter.

p.3
Neurotransmitters and Receptors in ANS

Which type of receptor is associated with norepinephrine in the sympathetic nervous system?
A) Muscarinic acetylcholine receptor (mAChR)
B) Nicotinic acetylcholine receptor (nAChR)
C) Adrenergic receptor
D) Dopaminergic receptor
E) Serotonin receptor

C) Adrenergic receptor
Explanation: Norepinephrine (NE) acts on adrenergic receptors in the sympathetic nervous system, which include various subtypes such as α and β receptors.

p.8
Sympathetic Nervous System Anatomy and Function

What is the primary source of epinephrine (E) in the body?
A) Adrenal cortex
B) Adrenal medulla
C) Pancreas
D) Thyroid gland
E) Pituitary gland

B) Adrenal medulla
Explanation: Epinephrine (E) is primarily released from the adrenal medulla, which is part of the sympathetic nervous system and functions as a modified postganglionic neuron.

p.9
Neurotransmitters and Receptors in ANS

What effect does norepinephrine (NE) have on α1 adrenergic receptors?
A) Vasodilation
B) Vasoconstriction
C) Increased glucose metabolism
D) Decreased heart rate
E) Increased respiratory rate

B) Vasoconstriction
Explanation: Norepinephrine stimulates α1 adrenergic receptors, leading to vasoconstriction, which increases blood pressure and redirects blood flow to essential organs during stress.

p.15
Calcium Regulation in Smooth Muscle

What is the relationship between membrane potential and force generation in smooth muscle?
A) They are inversely related
B) They are not related
C) They have a direct relationship
D) Membrane potential only affects cardiac muscle
E) Force generation is independent of calcium influx

C) They have a direct relationship
Explanation: In smooth muscle, there is a direct relationship between membrane potential and the generation of force, influenced by calcium mechanisms that play a crucial role in contraction.

p.18
Calcium Regulation in Smooth Muscle

What is the effect of increased intracellular calcium levels on smooth muscle contraction?
A) It decreases contraction
B) It has no effect
C) It activates MLCK
D) It directly phosphorylates MLC
E) It inhibits phosphatase activity

C) It activates MLCK
Explanation: An increase in intracellular calcium levels activates MLCK through the formation of a calcium-calmodulin complex, which is critical for initiating smooth muscle contraction.

p.5
Neurotransmitters and Receptors in ANS

What factors can influence the number of receptors in the body?
A) Only age
B) Only environmental factors
C) Age and hormonal effects
D) Only genetic factors
E) Only diet

C) Age and hormonal effects
Explanation: The number of receptors is tightly regulated and can change based on age and hormonal effects, indicating that both biological and physiological factors play a role in receptor expression.

p.2
Sympathetic Nervous System Anatomy and Function

Which region of the spinal cord do sympathetic nerves originate from?
A) Cranial region
B) Sacral region
C) Thoracic and lumbar region
D) Cervical region
E) Coccygeal region

C) Thoracic and lumbar region
Explanation: Sympathetic nerves originate from the thoracic and lumbar regions of the spinal cord, while the cervical region is not included in the autonomic nervous system.

p.5
Mechanisms of Signal Termination in ANS

What is one method by which the parasympathetic system terminates signals?
A) Reuptake of norepinephrine
B) ACh esterase activity
C) Blocking choline reuptake
D) Simple diffusion of dopamine
E) Increased receptor expression

B) ACh esterase activity
Explanation: In the parasympathetic system, acetylcholine (ACh) is terminated primarily through the action of ACh esterase, which breaks down the neurotransmitter in the synapse.

p.5
Mechanisms of Signal Termination in ANS

How is norepinephrine (NE) terminated in the sympathetic system?
A) By diffusion only
B) By reuptake and degradation in the cytoplasm
C) By blocking receptor sites
D) By increasing receptor expression
E) By ACh esterase activity

B) By reuptake and degradation in the cytoplasm
Explanation: In the sympathetic system, norepinephrine is primarily terminated through reuptake into the presynaptic neuron, where it is then degraded in the cytoplasm.

p.3
Neurotransmitters and Receptors in ANS

What type of synapse occurs between the preganglionic axon and the postganglionic neuron in both the parasympathetic and sympathetic nervous systems?
A) Chemical synapse
B) Electrical synapse
C) Hormonal synapse
D) Neuromuscular junction
E) Reflex synapse

A) Chemical synapse
Explanation: The first synapse between the preganglionic axon and the postganglionic neuron in both the parasympathetic and sympathetic nervous systems is a chemical synapse, where neurotransmitters like acetylcholine (ACh) are released.

p.3
Neurotransmitters and Receptors in ANS

What neurotransmitter is primarily released at the second synapse in the parasympathetic nervous system?
A) Norepinephrine (NE)
B) Acetylcholine (ACh)
C) Dopamine
D) Serotonin
E) Histamine

B) Acetylcholine (ACh)
Explanation: At the second synapse in the parasympathetic nervous system, acetylcholine (ACh) is the primary neurotransmitter released, which acts on muscarinic receptors.

p.15
Neurotransmitters and Receptors in ANS

Which type of calcium channel is primarily involved in smooth muscle action potentials?
A) T-type calcium channel
B) N-type calcium channel
C) L-type voltage-gated calcium channel
D) P-type calcium channel
E) R-type calcium channel

C) L-type voltage-gated calcium channel
Explanation: The L-type voltage-gated calcium channel is specifically involved in the action potentials of smooth muscle cells, differentiating them from neurons that utilize voltage-gated sodium channels.

p.15
Differences Between Multiunit and Single-unit Smooth Muscle

What characterizes the plateau phase in smooth muscle action potentials?
A) It lasts for milliseconds
B) It is a stable membrane potential
C) It lasts for around 10 seconds
D) It is only present in cardiac muscle
E) It is characterized by rapid depolarization

C) It lasts for around 10 seconds
Explanation: The plateau phase in smooth muscle action potentials is characterized by a maintained depolarization that lasts for approximately 10 seconds, which is significantly longer than in other muscle types.

p.18
Mechanisms of Signal Termination in ANS

What happens to phosphorylated Myosin Light Chain (MLC-P)?
A) It remains phosphorylated indefinitely
B) It is dephosphorylated by phosphatase
C) It activates MLCK
D) It binds to calcium
E) It inhibits muscle contraction

B) It is dephosphorylated by phosphatase
Explanation: Phosphorylated Myosin Light Chain (MLC-P) is dephosphorylated by phosphatase, which is essential for muscle relaxation and the termination of contraction.

p.22
Calcium Regulation in Smooth Muscle

What role does Rho-kinase play in smooth muscle contraction?
A) It decreases calcium sensitivity
B) It activates phosphatase
C) It phosphorylates MLC
D) It inhibits MLCK
E) It reduces contraction strength

C) It phosphorylates MLC
Explanation: Rho-kinase activates and phosphorylates myosin light chain (MLC), which contributes to smooth muscle contraction by increasing calcium sensitivity, allowing for contraction with less intracellular calcium.

p.14
Calcium Regulation in Smooth Muscle

What is the primary effect of increased intracellular calcium concentration in smooth muscle cells?
A) Induces relaxation
B) Induces contraction
C) Causes apoptosis
D) Inhibits neurotransmitter release
E) Decreases membrane potential

B) Induces contraction
Explanation: An increase in intracellular calcium concentration is crucial for inducing contraction in smooth muscle cells, which is essential for various physiological functions such as digestion.

p.22
Physiology of Smooth Muscle Contraction

What is the effect of cAMP on smooth muscle relaxation?
A) It decreases MLCK activity
B) It increases calcium sensitivity
C) It induces MLCK phosphorylation
D) It activates Rho-kinase
E) It inhibits phosphatase

C) It induces MLCK phosphorylation
Explanation: cAMP, through β2-adrenergic receptor stimulation, induces MLCK phosphorylation, which decreases calcium sensitivity and promotes relaxation of smooth muscle.

p.11
Neurotransmitters and Receptors in ANS

Which of the following pairs represents counteracting effects mediated by different muscles?
A) Heart rate and blood pressure
B) Pupillary sphincter and pupillary dilator
C) Salivary glands and sweat glands
D) Bronchi and lungs
E) Digestive organs and kidneys

B) Pupillary sphincter and pupillary dilator
Explanation: The pupillary sphincter is regulated by the parasympathetic division, while the pupillary dilator is regulated by the sympathetic division, demonstrating how different muscles can mediate counteracting effects.

p.19
Physiology of Smooth Muscle Contraction

Why is phosphorylation of myosin light chain (MLC) necessary for smooth muscle contraction?
A) It decreases calcium levels
B) It changes the structure of myosin
C) It activates calmodulin
D) It inhibits contraction
E) It binds to actin

B) It changes the structure of myosin
Explanation: Phosphorylation of MLC is necessary because it alters the structure of myosin, which is crucial for the contraction of smooth muscle cells, allowing them to interact effectively with actin.

p.19
Calcium Regulation in Smooth Muscle

What happens to intracellular calcium levels during smooth muscle contraction?
A) They remain constant
B) They increase and then decrease
C) They decrease continuously
D) They only increase
E) They fluctuate randomly

B) They increase and then decrease
Explanation: During smooth muscle contraction, intracellular calcium levels initially increase to trigger contraction and must subsequently decrease to terminate the contraction and allow relaxation.

p.1
Autonomic Nervous System (ANS) Overview

Which of the following is NOT a main division of the autonomic nervous system (ANS)?
A) Parasympathetic
B) Sympathetic
C) Enteric nervous system
D) Central nervous system
E) None of the above

D) Central nervous system
Explanation: The main divisions of the ANS include the parasympathetic, sympathetic, and enteric nervous systems. The central nervous system is not a division of the ANS.

p.9
Neurotransmitters and Receptors in ANS

Which neurotransmitter is more effective at stimulating α1 adrenergic receptors?
A) Acetylcholine
B) Epinephrine
C) Norepinephrine
D) Serotonin
E) Dopamine

C) Norepinephrine
Explanation: Norepinephrine is more effective than epinephrine at stimulating α1 adrenergic receptors, making it crucial for vasoconstriction during sympathetic activation.

p.2
Parasympathetic Nervous System Anatomy and Function

Which cranial nerves are associated with the parasympathetic nervous system?
A) 1, 2, 3, 4
B) 3, 5, 7, 9, 10
C) 3, 7, 9, 10
D) 5, 6, 8, 11
E) 4, 6, 8, 12

C) 3, 7, 9, 10
Explanation: The parasympathetic nervous system is associated with cranial nerves 3, 7, 9, and 10, which play a crucial role in its functions.

p.7
Sympathetic Nervous System Anatomy and Function

What is the role of the adrenal medulla in the autonomic nervous system?
A) It is part of the parasympathetic division
B) It is part of the sympathetic division
C) It has no role in the autonomic nervous system
D) It regulates the somatic nervous system
E) It is responsible for sensory input

B) It is part of the sympathetic division
Explanation: The adrenal medulla is specifically identified as a part of the sympathetic division of the autonomic nervous system, playing a crucial role in the body's stress response.

p.16
Neurotransmitters and Receptors in ANS

What is the primary factor that changes the membrane potential in smooth muscle cells?
A) Temperature changes
B) Ligand binding to receptors
C) Electrical stimulation
D) Mechanical stretching
E) Hormonal fluctuations

B) Ligand binding to receptors
Explanation: Ligand binding to receptors can lead to changes in membrane potential in smooth muscle cells, which is crucial for initiating contraction.

p.16
Physiology of Smooth Muscle Contraction

What phenomenon is associated with the formation of action potentials in smooth muscle cells?
A) Slow waves
B) Rapid depolarization
C) Hyperpolarization
D) Resting potential
E) Refractory period

A) Slow waves
Explanation: Slow waves in smooth muscle cells are associated with the formation of action potentials, which correlate with contractile force.

p.7
Neurotransmitters and Receptors in ANS

What is the enzyme responsible for the production of epinephrine in the adrenal medulla?
A) Acetylcholinesterase
B) N-methyltransferase
C) Choline acetyltransferase
D) Monoamine oxidase
E) Dipeptidyl peptidase

B) N-methyltransferase
Explanation: N-methyltransferase is the enzyme responsible for converting norepinephrine to epinephrine in the adrenal medulla, and its expression is dependent on high levels of steroid hormones.

p.5
Pharmacological Targets in Smooth Muscle

Which therapeutic approach can affect the parasympathetic system?
A) Increasing ACh release
B) Blocking ACh esterase
C) Enhancing choline reuptake
D) Increasing receptor expression
E) Blocking norepinephrine reuptake

B) Blocking ACh esterase
Explanation: One therapeutic approach in the parasympathetic system involves blocking ACh esterase, which would prolong the action of acetylcholine by preventing its breakdown.

p.6
Neurotransmitters and Receptors in ANS

What type of receptor is associated with the fast EPSP generated in the autonomic ganglia?
A) Muscarinic receptor
B) Adrenergic receptor
C) Nicotinic receptor
D) Opioid receptor
E) Serotonin receptor

C) Nicotinic receptor
Explanation: The nicotinic receptor is a ligand-dependent ion channel that generates fast excitatory postsynaptic potentials (EPSPs) in the autonomic ganglia.

p.9
Neurotransmitters and Receptors in ANS

What is the effect of epinephrine on β2 adrenergic receptors?
A) Vasoconstriction
B) Vasodilation
C) Decreased heart rate
D) Increased blood pressure
E) Increased glucose metabolism

B) Vasodilation
Explanation: Epinephrine has a higher affinity for β2 adrenergic receptors, leading to vasodilation, which helps increase blood flow to skeletal muscles during a 'fight or flight' response.

p.2
Parasympathetic Nervous System Anatomy and Function

Where are the ganglia of the parasympathetic nervous system located?
A) Near the spinal cord
B) Close to the target organ
C) In the brainstem
D) In the thoracic region
E) In the lumbar region

B) Close to the target organ
Explanation: The ganglia of the parasympathetic nervous system are located near or within the organ they innervate, allowing for a more localized response.

p.2
Parasympathetic Nervous System Anatomy and Function

What is the length of the preganglionic axon in the parasympathetic nervous system?
A) Short
B) Medium
C) Long
D) Variable
E) None of the above

C) Long
Explanation: In the parasympathetic nervous system, the preganglionic axon is long, as it extends close to the target organ before synapsing.

p.7
Neurotransmitters and Receptors in ANS

Why can adrenal medulla cells only release their transmitter into the bloodstream?
A) They have long axons
B) They have no axons
C) They are sensory cells
D) They are preganglionic neurons
E) They are motor neurons

B) They have no axons
Explanation: The cells in the adrenal medulla are postganglionic neurons that have lost their axons, which prevents them from forming typical synapses and allows them to release their transmitters directly into the bloodstream.

p.14
Physiology of Smooth Muscle Contraction

What role do electrical pacemaker cells (interstitial cells of Cajal) play in smooth muscle?
A) They inhibit contraction
B) They generate constant changes in membrane potential
C) They release neurotransmitters
D) They cause hyperpolarization
E) They are responsible for blood flow regulation

B) They generate constant changes in membrane potential
Explanation: Electrical pacemaker cells, such as interstitial cells of Cajal, generate constant changes in membrane potential, which are propagated via gap junctions and contribute to the rhythmic contractions of smooth muscle.

p.7
Neurotransmitters and Receptors in ANS

What condition is necessary for the formation of epinephrine in the adrenal gland?
A) Low steroid levels
B) High steroid levels
C) High oxygen levels
D) Low temperature
E) High glucose levels

B) High steroid levels
Explanation: The formation of epinephrine in the adrenal gland requires high local concentrations of steroid hormones, which induce the expression of the enzyme N-methyltransferase necessary for this conversion.

p.4
Neurotransmitters and Receptors in ANS

What role do receptors play in the autonomic nervous system?
A) They are not involved in neurotransmission
B) They are only targets for antagonists
C) They are pharmacological targets modulated by agonists and antagonists
D) They only respond to neurotransmitters from the central nervous system
E) They are exclusively found in skeletal muscle

C) They are pharmacological targets modulated by agonists and antagonists
Explanation: Receptors in the autonomic nervous system are efficiently modulated by both agonists and antagonists, making them important pharmacological targets for various therapeutic interventions.

p.6
Mechanisms of Signal Termination in ANS

Which of the following is NOT an input integrated at the level of autonomic ganglia?
A) Different afferents from the periphery
B) Somatic afferents to CNS
C) Interneurons
D) Local reflexes
E) Direct muscle contraction signals

E) Direct muscle contraction signals
Explanation: Direct muscle contraction signals are not integrated at the level of autonomic ganglia. Instead, various inputs such as afferents from the periphery, somatic afferents, interneurons, and local reflexes are integrated.

p.11
Sympathetic Nervous System Anatomy and Function

Which type of regulation is observed in organs regulated only by the sympathetic division?
A) Single regulation by the parasympathetic division
B) Double regulation by both divisions
C) Single regulation by the sympathetic division
D) No regulation at all
E) Regulation by external factors only

C) Single regulation by the sympathetic division
Explanation: Some organs, particularly most vascular smooth muscle, are regulated solely by the sympathetic division, indicating a single regulatory mechanism without influence from the parasympathetic division.

p.11
Parasympathetic Nervous System Anatomy and Function

What is the effect of the sympathetic division on heart rate?
A) Decreases heart rate
B) No effect on heart rate
C) Increases heart rate
D) Irregular heart rate
E) Stabilizes heart rate

C) Increases heart rate
Explanation: The sympathetic division is responsible for increasing heart rate, while the parasympathetic division decreases it, illustrating the counteracting effects of both divisions on the same target cell.

p.19
Physiology of Smooth Muscle Contraction

What is the role of myosin light chain kinase (MLCK) in smooth muscle contraction?
A) It phosphorylates myosin light chain (MLC)
B) It dephosphorylates myosin light chain (MLC)
C) It binds to calmodulin
D) It increases calcium levels
E) It activates sodium channels

A) It phosphorylates myosin light chain (MLC)
Explanation: MLCK is activated by the binding of calcium-calmodulin and is responsible for phosphorylating myosin light chain (MLC), which is crucial for the contraction of smooth muscle cells.

p.14
Physiology of Smooth Muscle Contraction

How does the action potential (AP) in smooth muscle cells differ from that in other cell types?
A) It has a larger amplitude
B) It lasts longer
C) It is generated by sodium channels only
D) It is shorter in duration
E) It does not involve calcium channels

B) It lasts longer
Explanation: The action potential in smooth muscle cells is characterized by a smaller amplitude and a longer duration compared to action potentials in other cell types, involving different ion channels.

p.4
Neurotransmitters and Receptors in ANS

Which receptor is mentioned as an example of a pharmacological target in the autonomic nervous system?
A) α1 adrenergic receptor
B) β1 adrenergic receptor
C) Muscarinic receptor
D) Nicotinic receptor
E) Dopamine receptor

B) β1 adrenergic receptor
Explanation: The β1 adrenergic receptor is specifically mentioned as an example of a receptor that serves as a pharmacological target, highlighting its significance in the modulation of autonomic responses.

p.4
Neurotransmitters and Receptors in ANS

How does the transmission from postganglionic autonomic axons differ from typical synaptic transmission?
A) It is always 1-1
B) It involves multiple varicosities
C) It only affects one target cell
D) It does not involve neurotransmitters
E) It is faster than typical transmission

B) It involves multiple varicosities
Explanation: Unlike typical 1-1 synaptic transmission, postganglionic autonomic axons release neurotransmitters from multiple varicosities, allowing them to influence many target cells simultaneously.

p.6
Parasympathetic Nervous System Anatomy and Function

Where are the autonomic ganglia located in relation to the target cells for the parasympathetic and sympathetic divisions?
A) Para= far from target cell, symp= close to target cell
B) Para= close to target cell, symp= close to CNS/spinal cord
C) Both are far from target cells
D) Both are close to target cells
E) Para= close to CNS, symp= far from CNS

B) Para= close to target cell, symp= close to CNS/spinal cord
Explanation: In the autonomic nervous system, parasympathetic ganglia are located close to the target cells, while sympathetic ganglia are situated close to the central nervous system (CNS) or spinal cord.

p.19
Mechanisms of Signal Termination in ANS

What mechanisms are involved in terminating the calcium signal in smooth muscle cells?
A) Increase in sodium levels
B) Membrane Ca2+-ATPase and Na+/Ca2+ antiporter
C) Decrease in potassium levels
D) Activation of MLCK
E) Increase in intracellular calcium

B) Membrane Ca2+-ATPase and Na+/Ca2+ antiporter
Explanation: To terminate the calcium signal in smooth muscle cells, mechanisms such as the membrane Ca2+-ATPase and Na+/Ca2+ antiporter are activated to decrease intracellular calcium levels, which is essential for muscle relaxation.

p.6
Mechanisms of Signal Termination in ANS

What happens at the level of autonomic ganglia when different inputs are integrated?
A) Only action potentials are generated
B) Only electrotonic potential changes occur
C) Summation of signals occurs, potentially leading to action potentials
D) No integration occurs
E) Only local reflexes are considered

C) Summation of signals occurs, potentially leading to action potentials
Explanation: At the level of autonomic ganglia, various inputs are integrated, leading to the summation of signals. If the summation is sufficient, an action potential may be generated and forwarded.

Study Smarter, Not Harder
Study Smarter, Not Harder