p.17
Smooth Muscle Physiology
What are the components of thin myofilaments in smooth muscle contraction?
Thin myofilaments consist of SMC actin and tropomyosin.
p.4
Pharmacological Targets in Autonomic Regulation
Can you give an example of a receptor that is a pharmacological target?
An example is the β1 adrenergic receptor.
p.20
Mechanisms of Smooth Muscle Relaxation
What is the role of cGMP in smooth muscle physiology?
cGMP activates phosphatase.
p.11
Parasympathetic and Sympathetic Divisions
What organs are regulated only by the sympathetic division?
Most vascular smooth muscle, which induces vasoconstriction via α1 adrenergic receptors, is regulated only by the sympathetic division.
p.12
Smooth Muscle Physiology
What are the similarities between smooth muscle and skeletal muscle?
Both have thin and thick filaments that slide over each other for contraction, require ATP for muscle contraction, and have intracellular calcium ([Ca2+]) as a critical regulator of contraction.
p.5
Mechanisms of Signal Termination
How can the signal from neurotransmitters be eliminated?
Through mechanisms such as enzyme action, reuptake, and diffusion.
p.5
Mechanisms of Signal Termination
What is the role of ACh esterase in the parasympathetic system?
ACh esterase helps in the termination of the signal by breaking down acetylcholine.
p.12
Smooth Muscle Physiology
Do smooth muscle cells have T tubules?
No, smooth muscle cells do not have T tubules, but they do have sarcoplasmic reticulum (SR), which varies in importance among different smooth muscle cells.
p.4
Neurotransmitters and Receptors in ANS
What is typical about transmitter release from postganglionic autonomic axons?
It involves varicosities with neurotransmitter vesicles, allowing one axon to affect many target cells rather than a 1-1 transmission.
p.9
Neurotransmitters and Receptors in ANS
How does epinephrine compare to norepinephrine in terms of β2 adrenergic receptors?
Epinephrine (E) has a higher affinity for β2 adrenergic receptors and is more effective than norepinephrine (NE) in causing vasodilation.
p.15
Calcium Regulation in Smooth Muscle Contraction
What type of channel is involved in the plateau phase of smooth muscle action potentials?
L-type voltage-gated calcium channel.
p.15
Neurotransmitters and Receptors in ANS
How do calcium-channel inhibitors affect action potentials in smooth muscle cells?
They can block action potentials, but smooth muscle cells are not sensitive to TTX, which blocks voltage-gated sodium channels.
p.15
Smooth Muscle Physiology
What is the time scale for the plateau phase of action potentials in smooth muscle?
The plateau phase lasts around 10 seconds.
p.22
Role of Myosin Light Chain in Smooth Muscle Contraction
What phosphorylates myosin light chain (MLC)?
MLC is phosphorylated by MLCK.
p.22
Mechanisms of Smooth Muscle Relaxation
What dephosphorylates MLC-P?
MLC-P is dephosphorylated by phosphatase.
p.20
Calcium Regulation in Smooth Muscle Contraction
What is the effect of phosphorylation of IP3R on calcium entry into the cell?
It inhibits calcium entry into the cell.
p.16
Mechanisms of Smooth Muscle Relaxation
What is pharmacomechanical activation in smooth muscle?
Pharmacomechanical activation refers to changes in contraction or relaxation of smooth muscle cells without a change in membrane potential, often through ligand binding to receptors.
p.19
Calcium Regulation in Smooth Muscle Contraction
What is the role of Rho-kinase in calcium-independent contraction?
Rho-kinase activates and phosphorylates myosin light chain (MLC), increasing calcium sensitivity and allowing for the same contraction with less intracellular calcium.
p.16
Mechanisms of Smooth Muscle Relaxation
What is the mechanism of electromechanical activation in smooth muscle?
Electromechanical activation involves depolarization from neighboring cells or ligand-dependent mechanisms that lead to contraction.
p.16
Neurotransmitters and Receptors in ANS
What happens when a ligand binds to a receptor in smooth muscle?
Ligand binding to a membrane receptor can activate intracellular signaling pathways, leading to calcium release and contraction of smooth muscle cells.
p.6
Neurotransmitters and Receptors in ANS
What type of receptor is involved in the autonomic ganglia?
Nicotinic receptor, which is a ligand-dependent ion channel that generates fast EPSP.
p.8
Parasympathetic and Sympathetic Divisions
What is the role of E in the sympathetic system?
E is only released from the adrenal medulla, which is a modified postganglionic neuron in the sympathetic system.
p.5
Neurotransmitters and Receptors in ANS
What factors can change the number of receptors in the body?
Age and hormonal effects can change the number of receptors.
p.16
Smooth Muscle Physiology
What are slow waves in smooth muscle cells?
Slow waves are changes in membrane potential that can lead to action potential formation and subsequent contractile force in smooth muscle cells.
p.12
Smooth Muscle Physiology
What is the role of dense bodies in smooth muscle?
Dense bodies serve as anchor points for thin filaments and are connected to the plasma membrane, facilitating contraction.
p.16
Calcium Regulation in Smooth Muscle Contraction
What role does calcium play in smooth muscle contraction?
Calcium is an important regulator in smooth muscle contraction, as its release into the cytoplasm is crucial for the contraction process.
p.6
Neurotransmitters and Receptors in ANS
What is the effect of inhibiting the NE transporter in the sympathetic synapse?
It changes the activity of the synapse by inhibiting norepinephrine (NE) uptake.
p.6
Parasympathetic and Sympathetic Divisions
Where are the autonomic ganglia located for the parasympathetic and sympathetic divisions?
Parasympathetic ganglia are close to the target cell, while sympathetic ganglia are close to the CNS/spinal cord.
p.18
Mechanisms of Signal Termination
How is the calcium signal terminated in smooth muscle cells?
The intracellular calcium level decreases through mechanisms such as membrane Ca2+ -ATP-ase, membrane Na+/Ca2+ antiporter, and SR - Ca2+ -ATP-ase.
p.19
Mechanisms of Smooth Muscle Relaxation
What is the effect of cGMP on smooth muscle contraction?
cGMP activates phosphatase, which leads to relaxation of smooth muscle.
p.21
Differences Between Multiunit and Single-unit Smooth Muscle
What are the characteristics of single-unit smooth muscle?
Single-unit smooth muscle is more common, has gap junctions between cells, exhibits spontaneous contractions and basal activity, and neural signals only modulate the activity.
p.22
Calcium Regulation in Smooth Muscle Contraction
How is MLCK activated?
MLCK can be activated by an increase in intracellular calcium levels, forming a calcium-calmodulin complex that activates MLCK.
p.4
Pharmacological Targets in Autonomic Regulation
Why are receptors considered pharmacological targets in the autonomic nervous system?
Receptor activity can be efficiently modulated by agonists and antagonists, making them important for pharmacological interventions.
p.14
Calcium Regulation in Smooth Muscle Contraction
What are the mechanisms that increase intracellular calcium levels in smooth muscle?
1. Depolarization from neighboring cells via gap junctions, 2. Neural stimulation leading to transmitter release, 3. Mechanical activation through mechanosensitive channels.
p.5
Mechanisms of Signal Termination
What are the mechanisms for signal termination in the sympathetic system?
NE reuptake leading to degradation in the cytoplasm and diffusion of transmitters.
p.5
Pharmacological Targets in Autonomic Regulation
What therapeutic approaches can be used in the parasympathetic system?
Blocking transmitter release (ACh), blocking choline reuptake, and blocking ACh esterase.
p.14
Neurotransmitters and Receptors in ANS
Which ion channels are involved in the depolarization and repolarization phases of smooth muscle action potentials?
The depolarization phase involves L-type voltage-gated Ca2+ channels, while the repolarization phase involves voltage-gated late K+ channels.
p.15
Calcium Regulation in Smooth Muscle Contraction
What is the significance of calcium mechanisms in smooth muscle action potentials?
Calcium mechanisms are important for both the formation and maintenance of action potentials.
p.19
Calcium Regulation in Smooth Muscle Contraction
How does cAMP affect calcium sensitivity?
cAMP induces MLCK phosphorylation, which decreases calcium sensitivity.
p.10
Autonomic Nervous System (ANS) Overview
What is the relationship between the two systems in the autonomic nervous system?
The two systems are counteracting, making the regulation of the autonomic nervous system not simple.
p.9
Parasympathetic and Sympathetic Divisions
What is the primary response of the sympathetic nervous system during a 'fight or flight' situation?
General activation of the sympathetic nervous system leads to increased blood pressure, heart rate, and dilation of pupils, among other effects.
p.14
Calcium Regulation in Smooth Muscle Contraction
What is the role of intracellular calcium concentration in smooth muscle contraction?
An increase in intracellular calcium concentration is important to induce contraction of smooth muscle cells.
p.17
Smooth Muscle Physiology
What is the structure of thick myofilaments in smooth muscle?
Thick myofilaments are composed of myosin, which includes two heavy chains and two light chains that bind to each heavy chain.
p.14
Mechanisms of Smooth Muscle Relaxation
What is the Bayliss effect?
The Bayliss effect refers to the contraction induced by mechanical changes, such as vessel stretching due to increased pressure, which opens mechanosensitive ion channels.
p.14
Smooth Muscle Physiology
How does the action potential in smooth muscle cells differ from that in other cell types?
The action potential in smooth muscle cells has a much smaller amplitude, lasts longer, and involves different ion channels.
p.18
Calcium Regulation in Smooth Muscle Contraction
What happens when calcium levels increase in a smooth muscle cell?
Calcium binds to calmodulin, changing its conformation and allowing it to bind to MLCK, which activates MLC and induces phosphorylation of MLC, leading to contraction.
p.20
Parasympathetic and Sympathetic Divisions
What is the neural control of contraction in multiunit smooth muscle?
Each cell is independently controlled by neural signals.
p.6
Autonomic Nervous System (ANS) Overview
What types of inputs are integrated at the level of autonomic ganglia?
Different afferents from the periphery, somatic afferents to the CNS, interneurons, further signals from the CNS, and local reflexes.
p.3
Neurotransmitters and Receptors in ANS
What type of receptor is found on the postganglionic neuron?
The postganglionic receptor is a nicotinic acetylcholine receptor (nAChR), which is ligand-gated.
p.21
Smooth Muscle Physiology
How does smooth muscle contraction compare to skeletal muscle contraction in terms of ATP usage?
Smooth muscle contraction requires much less ATP compared to skeletal muscle contraction.
p.9
Neurotransmitters and Receptors in ANS
What role do α1 adrenergic receptors play in the sympathetic nervous system response?
α1 adrenergic receptors are stimulated, leading to vasoconstriction in blood vessels of skeletal muscle.
p.11
Parasympathetic and Sympathetic Divisions
What is an example of counteracting effects mediated by different target cells?
The pupillary sphincter is regulated by the parasympathetic division, while the pupillary dilator is regulated by the sympathetic division.
p.12
Smooth Muscle Physiology
What is the morphology of smooth muscle cells?
Smooth muscle cells are uninucleated, small, not striated, lack Z lines, and have thin filaments anchored to dense bodies and the plasma membrane.
p.20
Role of Myosin Light Chain in Smooth Muscle Contraction
How does cAMP affect MLCK?
cAMP induces phosphorylation of MLCK by PKA, resulting in decreased calcium sensitivity.
p.2
Parasympathetic and Sympathetic Divisions
What are the cranial nerves associated with the parasympathetic nervous system?
Cranial nerves 3, 7, 9, and 10.
p.2
Parasympathetic and Sympathetic Divisions
Where are the ganglia located in the parasympathetic nervous system?
Near or within the organ, very close to the target cell.
p.2
Parasympathetic and Sympathetic Divisions
What is the length of the preganglionic axon in the parasympathetic nervous system?
Long, as it is close to the organ.
p.7
Neurotransmitters and Receptors in ANS
What is the relationship between norepinephrine and epinephrine in the adrenal medulla?
Norepinephrine is converted to epinephrine by the enzyme N-methyltransferase.
p.3
Neurotransmitters and Receptors in ANS
What is the first synapse in the autonomic nervous system?
The first synapse is between the preganglionic axon and the postganglionic neuron.
p.21
Smooth Muscle Physiology
What is the actin-myosin cycle like in smooth muscle?
The actin-myosin cycle in smooth muscle is slow, involving actin-myosin cross bridges.
p.4
Neurotransmitters and Receptors in ANS
How do autonomic nerves interact with smooth muscle cells?
Autonomic nerves release neurotransmitters from varicosities, which can affect multiple smooth muscle cells.
p.13
Smooth Muscle Physiology
What does the red color represent in the context of smooth muscle contraction and relaxation?
Red indicates a state of being fully relaxed and then fully contracted, with a return to complete relaxation after some time.
p.11
Parasympathetic and Sympathetic Divisions
How do the sympathetic and parasympathetic divisions affect salivary gland secretion?
The parasympathetic division induces non-viscous, enzyme-rich saliva, while the sympathetic division induces viscous, mucinous saliva.
p.1
Neurotransmitters and Receptors in ANS
What functions do autonomic neurotransmitters help regulate?
They help regulate functions such as heart rate, pupillary response, and blood pressure.
p.1
Parasympathetic and Sympathetic Divisions
What is the pathway of signal transmission in the ANS?
The pathway involves a preganglionic neuron from the CNS, which synapses with a postganglionic neuron in a peripheral ganglion, leading to the target cell.
p.13
Smooth Muscle Physiology
Can you give examples of organs associated with the different states of smooth muscle?
Examples include the esophagus and urinary bladder for fully relaxed and contracted states, sphincters for normally contracted states, and smooth muscle in airways and blood vessels for partial tone.
p.17
Role of Myosin Light Chain in Smooth Muscle Contraction
What distinguishes the myosin light chain in smooth muscle from that in skeletal muscle?
The myosin light chain in smooth muscle has different subunits than those found in skeletal muscle.
p.19
Mechanisms of Smooth Muscle Relaxation
What are the two important mechanisms for relaxation of smooth muscle?
cAMP (via β2-adrenergic receptor stimulation) and cGMP (NO-dependent activation) are crucial for smooth muscle relaxation.
p.8
Parasympathetic and Sympathetic Divisions
What is the characteristic of preganglionic neurons in the sympathetic system?
In the sympathetic system, the preganglionic neurons are long.
p.9
Neurotransmitters and Receptors in ANS
Which neurotransmitter is more effective for α1 adrenergic receptors?
Norepinephrine (NE) is more effective than epinephrine (E) for α1 adrenergic receptors.
p.1
Autonomic Nervous System (ANS) Overview
What are the main divisions of the Autonomic Nervous System (ANS)?
The main divisions of the ANS are the Parasympathetic, Sympathetic, and Enteric nervous system.
p.13
Smooth Muscle Physiology
How do smooth muscle cells differ across various organs?
Smooth muscle cells are not a homogenous population; there are many differences between smooth muscle cells in different organs.
p.17
Role of Myosin Light Chain in Smooth Muscle Contraction
What is the role of myosin light chain (MLC) in smooth muscle contraction?
MLC, when phosphorylated, allows for the binding of actin and myosin.
p.17
Pharmacological Targets in Autonomic Regulation
What enzyme mediates the phosphorylation of myosin light chain?
The phosphorylation of myosin light chain is mediated by MLCK (myosin light chain kinase).
p.1
Parasympathetic and Sympathetic Divisions
How many synapses are involved in the ANS pathway?
There are two synapses involved: one between the preganglionic and postganglionic neurons, and the other at the target cell.
p.18
Role of Myosin Light Chain in Smooth Muscle Contraction
Why is MLC phosphorylation crucial for smooth muscle contraction?
Phosphorylated MLC changes the structure connected to the heavy chains, which is essential for the contraction of smooth muscle cells.
p.7
Pharmacological Targets in Autonomic Regulation
What is required for the expression of the enzyme N-methyltransferase?
The expression of N-methyltransferase is dependent on high levels of steroid hormones.
p.3
Neurotransmitters and Receptors in ANS
What are the types of receptors for acetylcholine in effector cells?
The receptors for acetylcholine in effector cells are muscarinic acetylcholine receptors (mAChR), which include M1, M2, M3, M4, and M5.
p.22
Role of Myosin Light Chain in Smooth Muscle Contraction
What is the result of MLC phosphorylation?
MLC-P is the phosphorylated form of myosin light chain.
p.5
Neurotransmitters and Receptors in ANS
What does the expression pattern of receptors indicate?
The expression pattern is dynamic and can lead to tissue-specific cellular responses.
p.1
Neurotransmitters and Receptors in ANS
What is the role of autonomic neurotransmitters?
Autonomic neurotransmitters regulate unconscious autonomic functions, which are important for maintaining homeostasis in the body.
p.7
Parasympathetic and Sympathetic Divisions
What is the adrenal medulla a part of?
The adrenal medulla is part of the sympathetic division.
p.7
Parasympathetic and Sympathetic Divisions
What type of neurons are found in the adrenal medulla?
The adrenal medulla contains modified, specific postganglionic neurons.
p.17
Smooth Muscle Physiology
How many heavy chains are present in myosin for smooth muscle?
There are two heavy chains in myosin for smooth muscle.
p.7
Neurotransmitters and Receptors in ANS
How do postganglionic neurons in the adrenal medulla release their transmitter?
They release their transmitter directly into the bloodstream.
p.2
Parasympathetic and Sympathetic Divisions
Where are the ganglia located in the sympathetic nervous system?
Close to the spinal cord, in pre/paravertebral ganglia.
p.3
Neurotransmitters and Receptors in ANS
What are the adrenergic receptors associated with norepinephrine?
The adrenergic receptors associated with norepinephrine are α1, α2, β1, β2, and β3.
p.8
Parasympathetic and Sympathetic Divisions
What type of neuron is the adrenal medulla considered in the sympathetic system?
The adrenal medulla is considered a modified postganglionic neuron.
p.11
Parasympathetic and Sympathetic Divisions
How do the sympathetic and parasympathetic divisions affect heart rate?
The sympathetic division increases heart rate, while the parasympathetic division decreases it.
p.16
Smooth Muscle Physiology
How are action potentials correlated with contraction in smooth muscle?
Many action potentials are correlated with contraction, indicating that the frequency of action potentials can influence the strength of contraction.
p.13
Smooth Muscle Physiology
What does the green color signify regarding smooth muscle state?
Green indicates a normally contracted resting state, where the muscle can relax upon receiving a signal and then contract again.
p.13
Smooth Muscle Physiology
What does the blue color represent in terms of smooth muscle tone?
Blue represents a normally partial tone, where there is an increase in contraction followed by stimulation for relaxation.
p.19
Calcium Regulation in Smooth Muscle Contraction
How does Rho-kinase affect MLCK activity?
Rho-kinase has an additive effect with MLCK, enhancing contraction by increasing calcium sensitivity.
p.19
Calcium Regulation in Smooth Muscle Contraction
What happens when Rho-kinase is active?
Less intracellular calcium is needed to induce the same contraction due to increased calcium sensitivity.
p.2
Parasympathetic and Sympathetic Divisions
From which regions do sympathetic nerves originate?
From the thoracic and lumbar regions of the spinal cord.
p.3
Neurotransmitters and Receptors in ANS
What neurotransmitter is released by the preganglionic axon in both parasympathetic and sympathetic divisions?
Acetylcholine (ACh) is released by the preganglionic axon.
p.20
Mechanisms of Smooth Muscle Relaxation
What happens when IP3 is phosphorylated?
It limits calcium entry into the cell, inducing relaxation.
p.7
Parasympathetic and Sympathetic Divisions
What happens to the axons of postganglionic neurons in the adrenal medulla?
The postganglionic neurons in the adrenal medulla lose their axons.
p.7
Pharmacological Targets in Autonomic Regulation
What does the adrenal gland produce that affects the formation of epinephrine?
The adrenal gland produces high levels of steroids, which are necessary for the formation of epinephrine.
p.12
Smooth Muscle Physiology
How are thin and thick filaments connected in smooth muscle?
Thin and thick filaments in smooth muscle are connected to each other through gap junctions between adjacent cells.
p.20
Differences Between Multiunit and Single-unit Smooth Muscle
What characterizes multiunit smooth muscle?
Each smooth muscle cell has its own innervation.
p.3
Neurotransmitters and Receptors in ANS
What neurotransmitter is primarily used at the second synapse in the parasympathetic division?
Acetylcholine (ACh) is primarily used at the second synapse in the parasympathetic division.
p.15
Differences Between Multiunit and Single-unit Smooth Muscle
What is the relationship between membrane potential and force generation in smooth muscle?
There are different relationships between membrane potential and force generation in different types of smooth muscle.
p.19
Mechanisms of Smooth Muscle Relaxation
What is the effect of Rho-kinase on phosphatase function?
Rho-kinase inhibits the function of phosphatase, leading to increased phosphorylation of MLC and stronger contractions.
p.6
Mechanisms of Signal Termination
What happens to the electrotonic potential at the autonomic ganglia before an action potential is generated?
Only electrotonic potential changes at first, followed by summation of all signals, leading to an action potential if the threshold is reached.
p.3
Neurotransmitters and Receptors in ANS
What neurotransmitter is primarily used at the second synapse in the sympathetic division?
Norepinephrine (NE) is primarily used at the second synapse in the sympathetic division.
