The cochlea is a spiral-shaped organ in the inner ear that converts sound vibrations into electrochemical signals through the movement of hair cells.
Voluntary movements are actions that are consciously controlled by the nervous system, involving the activation of muscles to produce movement.
Flexors are muscles that bend a joint, bringing the bones closer together.
The primary visual cortex is a thin sheet of neural tissue located in the occipital lobe that processes visual information received from the thalamus and preserves the retina's visual map.
Strabismus is a condition where the eyes are not properly aligned, leading to a loss of depth perception and difficulty in fusing images from both eyes.
The optic nerve carries electrical signals from the retina to other parts of the brain for further processing and interpretation of visual information.
Hair cells are sensory cells located on the basilar membrane of the cochlea that convert mechanical sound vibrations into electrical signals for the auditory nerve.
Taste buds are sensory organs located on the tongue that contain taste receptor cells, responsible for detecting different taste qualities.
Center-surround antagonism is a mechanism in the visual system that maximizes the perception of contrast by having ganglion cells respond strongly to light in the center of their receptive field while being inhibited by light in the surrounding area.
Antagonists are muscles that oppose or inhibit movement, relaxing when agonists contract.
The fovea is a small area in the center of the retina densely packed with cones, allowing for sharp vision and the resolution of fine details.
Two-point discrimination is the minimum distance between two points on the skin that a person can identify as distinct stimuli rather than a single one.
Neurogenesis refers to the process by which new neurons are generated; in the case of olfactory neurons, they are continually replaced throughout life.
The dorsal stream is involved in processing spatial relationships and motion ('Where'), while the ventral stream is responsible for object recognition and conscious visual experiences ('What').
Nociceptors are special sensory fibers that respond to stimuli that can cause tissue damage, signaling both the sensory and emotional components of pain.
Rods are responsible for vision in low light conditions, while cones are responsible for color vision and detail in well-lit conditions.
Inhibitory interneurons are neurons located within the spinal cord that, when activated by a sensory stimulus, send impulses to inhibit the motor neurons supplying the antagonist flexor muscle.
Wernicke’s area is a region in the left auditory cortex responsible for understanding and producing speech; damage to this area can impair language comprehension.
Olfaction is the sense of smell, which involves the detection of odor molecules by specialized olfactory cells in the nasal cavity.
Agonists are muscles that promote movement by contracting, allowing for actions such as throwing or lifting.
A motor unit is a functional unit consisting of an alpha motor neuron and all the muscle fibers it controls, linking the central nervous system to skeletal muscles.
The peripheral nervous system consists of nerves and ganglia, transmitting messages from the brain to control muscles and internal organs.
The somatosensory system is responsible for all touch sensations, including light touch, pressure, vibration, temperature, texture, itch, and pain.
Neuropathic pain is a state of hypersensitivity to pain caused by a malfunctioning nervous system rather than by an injury, often seen in conditions like diabetic neuropathy.
Endorphins are opioids produced by the body that act to relieve pain by intercepting pain signals ascending in the spinal cord and brainstem.
Sensory nerve fibers, such as A-delta and C fibers, transmit pain and itch messages to the spinal cord and brain, with A-delta fibers conveying sharp pain and C fibers conveying dull pain.
The flexion withdrawal reflex is a protective reflex that occurs when pain receptors in the skin send a message to the spinal cord, leading to the immediate lifting (flexion) of a leg upon encountering a sharp object.
Gamma motor neurons are a separate set of motor neurons that adjust the sensitivity of muscle spindles by keeping them taut, allowing for accurate detection of muscle stretch.
Neuromuscular junctions are sites where neurons communicate with muscles, allowing for the transmission of signals that result in muscle contraction.
The retina contains three types of neurons—photoreceptors, interneurons, and ganglion cells—that process visual information before sending it to the brain.
The basilar membrane runs along the cochlea and is tuned to different frequencies, playing a crucial role in the transduction of sound waves into electrical signals.
Reciprocal inhibition is the process by which the activation of motor neurons controlling one muscle (the extensor) simultaneously inhibits the motor neurons controlling the antagonist muscle (the flexor), allowing for coordinated movement.
Muscle spindles are specialized sensory receptors located within muscles that provide information about changes in muscle length or stretch, helping the brain adjust motor control.
The receptive field of a ganglion cell is the specific area on the retina that, when light hits it, activates the cell; it is inhibited when light hits the surrounding area.
Taste and smell are separate senses, but they work together to create the perception of flavor; when one is impaired, such as during a cold, the overall taste experience is diminished.
Transduction is the process by which sense organs convert stimuli such as light waves or food molecules into electrical signals.
Hair cells are specialized receptor cells in the cochlea that transduce pressure waves into electrical signals, allowing sound information to be sent to the brain.
The receptive field is the portion of visual space that provides input to a single ganglion cell, influencing its response to visual stimuli.
Macular degeneration is a condition that leads to the death or degeneration of photoreceptors in the macula, resulting in a leading cause of blindness in older adults.
The emotional component of pain makes the experience unpleasant and distressing, influencing how pain is perceived and managed.
The thalamus acts as the brain's relay station for incoming sensory information, including sound, before sending it to the auditory cortex.
The knee jerk reflex is a stretch reflex that occurs when a physician strikes the tendon below the knee, causing a slight stretch of the knee extensor muscle, which is sensed by muscle spindles and results in muscle contraction.
The optic chiasm is a crossover junction where nerve fibers from both eyes converge, allowing visual information from the left side of the retinas to continue to the left side of the brain and vice versa.
Binocular vision is the ability to perceive depth or three dimensions using two eyes, which see an object from slightly different angles.
The two types of photoreceptors are rods, which are sensitive to dim light, and cones, which detect fine detail and color.
Prostaglandins enhance the sensitivity of receptors to tissue damage, making pain feel more intense and contributing to conditions like allodynia.
The sensitivity of different body regions to tactile stimuli depends on the number of touch receptors per unit area and the distance between them, with more densely packed areas being more sensitive.
The crossed extension reflex is a reaction that occurs simultaneously with the flexion withdrawal reflex, where the extensors of the opposite leg are activated to maintain balance when one leg is lifted.
Skeletal muscles are muscles that attach to the skeleton and span joints, enabling movement by either flexing or extending the joints they span.
Extensors are muscles that straighten a joint, increasing the angle between the bones.
Co-contraction is when agonists and their opposing antagonists contract simultaneously to stabilize or control a movement.
The central nervous system consists of the brain and spinal cord, directing coordinated actions of muscles for movement.
The periaqueductal gray matter activates descending pathways that modulate pain and send messages to networks that release endorphins, helping to regulate and reduce pain.
