Glossery Flashcards
adult neurogenesis
The creation of new neurons in the brain of an adult.
amblyopia
Reduced visual acuity that is not caused by optical or retinal impairments.
Asperger’s syndrome
ometimes called high-functioning autism. A syndrome characterized by difficulties in social cognitive processing; usually accompanied by strong language skills.
autism
A disorder arising during childhood, characterized by social withdrawal and perseverative behavior.
behavioral teratology
The study of impairments in behavior that are produced by embryonic or fetal exposure to toxic substances.
binocular deprivation
Depriving both eyes of form vision, as by sealing the eyelids.
caspases
A family of proteins that regulate cell death (apoptosis).
cell adhesion molecule (CAM)
A protein found on the surface of a cell that guides cell migration and/or axonal pathfinding.
cell death or apoptosis
The developmental process during which “surplus” cells die.
cell differentiation
The developmental stage in which cells acquire distinctive characteristics, such as those of
cell migration
The movement of cells from site of origin to final location.
cell-cell interactions
The general process during development in which one cell affects the differentiation of other, usually neighboring, cells.
chemoattractants
Compounds that attract particular classes of growth cones.
chemorepellents
Compounds that repel particular classes of growth cones.
death gene
A gene that is expressed only when a cell becomes committed to natural cell death (apoptosis).
Diablo
A protein released by mitochondria, in response to high calcium levels, that activates apoptosis.
ectoderm
The outer cellular layer of the developing fetus, giving rise to the skin and the nervous system.
embryo
The earliest stage in a developing animal.
fetus
A developing individual after the embryo stage.
filopodia
Very fine, tubular outgrowths from the growth cone.
fragile X syndrome
A condition that is a frequent cause of inherited intellectual disability; produced by a fragile site on the X chromosome that seems prone to breaking because the DNA there is unstable.
growth cone
The growing tip of an axon or a dendrite.
hypoxia
A transient lack of oxygen.
induction
The process by which one set of cells influences the fate of neighboring cells, usually by secreting a chemical factor that changes gene expression in the target cells.
inhibitors of apoptosis proteins (IAPs)
A family of proteins that inhibit caspases and thereby stave off apoptosis.
lamellipodia
Sheetlike extensions of a growth cone.
monocular deprivation
Depriving one eye of light.
multiple sclerosis
terally, “many scars”; a disorder characterized by widespread degeneration of myelin.
nerve growth factor (NGF)
A substance that markedly affects the growth of neurons in spinal ganglia and in the ganglia of the sympathetic nervous system.
neural groove
n the developing embryo, the groove between the neural folds.
neural tube
An embryonic structure with subdivisions that correspond to the future forebrain, midbrain, and hindbrain.
neurogenesis
The mitotic division of nonneuronal cells to produce neurons.
neurotrophic factor
Also called trophic factor. A target-derived chemical that acts as if it “feeds” certain neurons to help them survive.
neurotrophin
A chemical that prevents neurons from dying.
notochord
A midline structure arising early in the embryonic development of vertebrates.
ocular dominance histogram
A graph that portrays the strength of response of a brain neuron to stimuli presented to either the left eye or the right eye.
perseverate
To continue to show a behavior repeatedly
phenylketonuria (PKU)
An inherited disorder of protein metabolism in which the absence of an enzyme leads to a toxic buildup of certain compounds, causing intellectual disability.
process outgrowth
The extensive growth of axons and dendrites.
radial glial cells
Glial cells that form early in development, spanning the width of the emerging cerebral hemispheres, and guide migrating neurons.
regulation
An adaptive response to early injury, as when developing individuals compensate for missing or injured cells.
retrograde degeneration
Destruction of the nerve cell body following injury to its axon.
senile dementia
A neurological disorder of the aged that is characterized by progressive behavioral deterioration, including personality change and profound intellectual decline. It includes, but is not limited to, Alzheimer’s disease.
stem cellsynapse rearrangement
A cell that is undifferentiated and therefore can take on the fate of any cell that a donor organism can produce.
synapse rearrangement
Also called synaptic remodeling. The loss of some synapses and the development of others; a refinement of synaptic connections that is often seen in development.
synaptogenesis
The establishment of synaptic connections as axons and dendrites grow.
ventricular zone
Also called ependymal layer. A region lining the cerebral ventricles that displays mitosis, providing neurons early in development and glial cells throughout life.
zygote
The fertilized egg.
adaptation
The progressive loss of receptor sensitivity as stimulation is maintained.
adequate stimulus
The type of stimulus for which a given sensory organ is particularly adapted.
analgesia
Absence of or reduction in pain.
anterolateral system or spinothalamic system
A somatosensory system that carries most of the pain information from the body to the brain.
capsaicin
A compound synthesized by various plants to deter predators by mimicking the experience of burning.
central modulation of sensory information
The process in which higher brain centers, such as the cortex and thalamus, suppress some sources of sensory information and amplify others.
cingulate cortex
Also called cingulum. A region of medial cerebral cortex that lies dorsal to the corpus callosum.
coding
The rules by which action potentials in a sensory system reflect a physical stimulus.
congenital insensitivity to pain
The condition of being born without the ability to perceive pain.
dermatome
A strip of skin innervated by a particular spinal root.
dermis
he middle layer of skin, between the epidermis and the hypodermis.
dorsal column system
A somatosensory system that delivers most touch stimuli via the dorsal columns of spinal white matter to the brain.
endogenous opioids
A family of peptide transmitters that have been called the body’s own narcotics. The three kinds are enkephalins, endorphins, and dynorphins.
epidermis
The outermost layer of skin, over the dermis.
free nerve ending
An axon that terminates in the skin without any specialized cell associated with it and that detects pain and/or changes in temperature.
generator potential
A local change in the resting potential of a receptor cell that mediates between the impact of stimuli and the initiation of action potentials.
hypodermis
Also called subcutaneous tissue. The innermost layer of skin, under the dermis.
labeled lines
The concept that each nerve input to the brain reports only a particular type of information.
naloxone
A potent antagonist of opiates that is often administered to people who have taken drug overdoses. It binds to receptors for endogenous opioids.
neuropathic pain
Pain caused by damage to peripheral nerves; often difficult to treat.
nociceptor
A receptor that responds to stimuli that produce tissue damage or pose the threat of damage.
Pacinian corpuscle
A skin receptor cell type that detects vibration.
periaqueductal gray
The neuronal body–rich region of the midbrain surrounding the cerebral aqueduct that connects the third and fourth ventricles; involved in pain perception.
polymodal
Involving several sensory modalities.
primary sensory cortex
For a given sensory modality, the region of cortex that receives most of the information about that modality from the thalamus or, in the case of olfaction, directly from the secondary sensory neurons.
primary somatosensory cortex (S1) or somatosensory 1
The gyrus just posterior to the central sulcus where sensory receptors on the body surface are mapped. Primary cortex for receiving touch and pain information, in the parietal lobe.
range fractionation
A hypothesis of stimulus intensity perception stating that a wide range of intensity values can be encoded by a group of cells, each of which is a specialist for a particular range of stimulus intensities.
receptive field
The stimulus region and features that affect the activity of a cell in a sensory system.
receptor cell
A specialized cell that responds to a particular energy or substance in the internal or external environment, and converts this energy into a change in the electrical potential across its membrane.
Ruffini’s ending
A skin receptor cell type that detects stretching of the skin.
secondary sensory cortex or nonprimary sensory cortex
For a given sensory modality, the cortical regions receiving direct projections from primary sensory cortex for that modality.
secondary somatosensory cortex (S2) or somatosensory 2
The region of cortex that receives direct projections from primary somatosensory cortex.
sensory pathway
The chain of neural connections from sensory receptor cells to the cortex.
sensory receptor organ
An organ (such as the eye or ear) specialized to receive particular stimuli.
sensory transduction
The process in which a receptor cell converts the energy in a stimulus into a change in the electrical potential across its membrane.
somatosensory
Referring to body sensation, particularly touch and pain sensation.
specific nerve energies
The doctrine that the receptors and neural channels for the different senses are independent and operate in their own special ways, and can produce only one particular sensation each.
stimulus
A physical event that triggers a sensory response.
synesthesia
A condition in which stimuli in one modality evoke the involuntary experience of an additional sensation in another modality.
thalamus
The brain regions at the top of the brainstem that trade information with the cortex.
threshold
The stimulus intensity that is just adequate to trigger an action potential at the axon hillock.
tonic receptor
A receptor in which the frequency of action potentials declines slowly or not at all as stimulation is maintained.
transient receptor potential 2 (TRP2)
A receptor, found in some free nerve endings, that opens its channel in response to rising temperatures.
transient receptor potential vanilloid type 1 (TRPV1)
Also called vanilloid receptor 1. A receptor that binds capsaicin to transmit the burning sensation from chili peppers and normally detects sudden increases in temperature.
amplitude
The force sound exerts per unit area, usually measured as dynes per square centimeter.
ampulla
An enlarged region of each semicircular canal that contains the receptor cells (hair cells) of the vestibular system.
amusia
A disorder characterized by the inability to discern tunes accurately.
anosmia
The inability to smell.
auditory brainstem implant (ABI)
A type of auditory prosthesis in which implanted microphones directly stimulate the auditory nuclei of the brainstem rather than the cochlea.
basilar membrane
A membrane in the cochlea that contains the principal structures involved in auditory transduction.
binaural
Pertaining to two ears.
Pertaining to two ears.
A hearing impairment that is related to lesions in auditory pathways or centers, including sites in the brainstem, thalamus, or cortex.
cilium
A hairlike extension.
circumvallate papillae
One of three types of small structures on the tongue, located in the back, that contain taste receptors.
cochlea
A snail-shaped structure in the inner ear that contains the primary receptor cells for hearing.
cochlear amplifier
The mechanism by which the cochlea is physically distorted by outer hair cells in order to “tune” the cochlea to be particularly sensitive to some frequencies more than others.
cochlear implant
An electromechanical device that detects sounds and selectively stimulates nerves in different regions of the cochlea via surgically implanted electrodes.
cochlear nuclei
Brainstem nuclei that receive input from auditory hair cells and send output to the superior olivary complex.
conduction deafness
A hearing impairment that is associated with pathology of the external-ear or middle-ear cavities.
cortical deafness
A hearing impairment that is caused by a fault or defect in the cortex.
dendritic knob
A portion of olfactory receptor cells present in the olfactory epithelium.
duplex theory
A theory that we localize sound by combining information about intensity differences and latency differences between the two ears.
external ear
The part of the ear that we readily see (the pinna) and the canal that leads to the eardrum.
frequency
The number of cycles per second in a sound wave; measured in hertz (Hz).
fungiform papillae
One of three types of small structures on the tongue, located in the front, that contain taste receptors.
foliate papillae
One of three types of small structures on the tongue, located along the sides, that contain taste receptors.
glomerulus
A complex arbor of dendrites from a group of olfactory cells.
gustatory system
The taste system.
hair cell
One of the receptor cells for hearing in the cochlea.
hertz (Hz)
Cycles per second, as of an auditory stimulus.
inferior colliculi
Paired gray matter structures of the dorsal midbrain that receive auditory information.
inner ear
The cochlea and vestibular apparatus.
inner hair cell (IHC)
One of the two types of receptor cells for hearing in the cochlea.
intensity differences
Perceived differences in loudness between the two ears, which can be used to localize a sound source.
latency differences
Differences between the two ears in the time of arrival of a sound, which can be employed by the nervous system to localize sound sources.
lateral-line system
A sensory system, found in many kinds of fishes and some amphibians, that informs the animal of water motion in relation to the body surface.
medial geniculate nuclei
Nuclei in the thalamus that receive input from the inferior colliculi and send output to the auditory cortex.
middle ear
The cavity between the tympanic membrane and the cochlea.
mitral cell
A type of cell in the olfactory bulb that conducts smell information from the glomeruli to the rest of the brain.
monaural
Pertaining to one ear.
olfactory bulb
An anterior projection of the brain that terminates in the upper nasal passages and, through small openings in the skull, provides receptors for smell.
olfactory epithelium
A sheet of cells, including olfactory receptors, that lines the dorsal portion of the nasal cavities and adjacent regions, including the septum that separates the left and right nasal cavities.
organ of Corti
A structure in the inner ear that lies on the basilar membrane of the cochlea and contains the hair cells and terminations of the auditory nerve.
ossicles
Three small bones (incus, malleus, and stapes) that transmit sound across the middle ear, from the tympanic membrane to the oval window.
ototoxic
Toxic to the ears, especially the middle or inner ear.
outer hair cell (OHC)
One of the two types of receptor cells for hearing in the cochlea.
oval window
The opening from the middle ear to the inner ear.
papilla
A small bump that projects from the surface of the tongue. Papillae contain most of the taste receptor cells.
pattern coding
Coding of information in sensory systems based on the temporal pattern of action potentials.
pinna
The external part of the ear.
pitch
A dimension of auditory experience in which sounds vary from low to high.
place theory
A theory of frequency discrimination stating that pitch perception depends on the place of maximal displacement of the basilar membrane produced by a sound.
pure tone
A tone with a single frequency of vibration.
round window
A membrane separating the cochlear duct from the middle-ear cavity.
semicircular canal
One of the three fluid-filled tubes in the inner ear that are part of the vestibular system. Each of the tubes, which are at right angles to each other, detects angular acceleration.
sensorineural deafness
A hearing impairment that originates from cochlear or auditory nerve lesions.
spectral filtering
Alteration of the amplitude of some, but not all, frequencies in a sound.
stereocilium
A relatively stiff hair that protrudes from a hair cell in the auditory or vestibular system.
tastant
A substance that can be tasted.
taste bud
A cluster of 50–150 cells that detects tastes. Taste buds are found in papillae.
taste pore
The small aperture through which tastant molecules are able to access the sensory receptors of the taste bud.
tectorial membrane
A membrane that sits atop the organ of Corti in the cochlear duct.
tensor tympani
The muscle attached to the malleus that modulates mechanical linkage to protect the delicate receptor cells of the inner ear from damaging sounds.
tinnitus
A sensation of noises or ringing in the ears.
tip link
A fine, threadlike fiber that runs along and connects the tips of stereocilia.
tonotopic organization
A major organizational feature in auditory systems in which neurons are arranged as an orderly map of stimulus frequency, with cells responsive to high frequencies located at a distance from those responsive to low frequencies.
transduction
The conversion of one form of energy to another.
tuning curve
A graph of the responses of a single auditory nerve fiber or neuron to sounds that vary in frequency and intensity.
tympanic membrane
Also called eardrum. The partition between the external ear and the middle ear.
ultrasound
High-frequency sound; in general, above the threshold for human hearing, at about 20,000 Hz.
umami
One of the five basic tastes (along with salty, sour, sweet, and bitter), probably mediated by amino acids in foods.
volley theory
A theory of frequency discrimination that emphasizes the relation between sound frequency and the firing pattern of nerve cells.
word deafness
The specific inability to hear words, although other sounds can be detected.
accommodation (sight)
The process of focusing by the ciliary muscles and the lens to form a sharp image on the retina.
bipolar cells
A class of interneurons of the retina that receive information from rods and cones and pass the information to retinal ganglion cells.
blind spot
The portion of the visual field from which light falls on the optic disc. Because there are no receptors in this region, light striking it cannot be seen.
ciliary muscle
One of the muscles that controls the shape of the lens inside the eye, focusing an image on the retina.
complex cortical cell
A cell in the visual cortex that responds best to a bar of a particular size and orientation anywhere within a particular area of the visual field.
cones
A class of photoreceptor cells in the retina that are responsible for color vision.
cornea
The transparent outer layer of the eye, whose curvature is fixed. It bends light rays and is primarily responsible for forming the image on the retina.
extraocular muscle
One of the muscles attached to the eyeball that control its position and movements.
fovea
The central portion of the retina, packed with the most photoreceptors and therefore the center of our gaze.
ganglion cells
A class of cells in the retina whose axons form the optic nerve.
horizontal cells
Specialized retinal cells that contact both the receptor cells and the bipolar cells.
three basic dimensions of light perception
hue
brightness
saturation
iris
The circular structure of the eye that provides an opening to form the pupil.
mirror neuron
A neuron that is active both when an individual makes a particular movement and when that individual sees another individual make that same movement.
myopia
Nearsightedness; the inability to focus the retinal image of objects that are far away.
occipital cortex
Also called visual cortex. The cortex of the occipital lobe of the brain.
ocular dominance column
A region of cortex in which one eye or the other provides a greater degree of synaptic input.
ocular dominance slab
A slab of visual cortex, about 0.5 mm wide, in which the neurons of all layers respond preferentially to stimulation of one eye.
opponent-process hypothesis
The theory that color vision depends on systems that produce opposite responses to light of different wavelengths.
opsin
One of the two components of photopigments in the retina.
optic chiasm
The point at which the two optic nerves meet.
optic disc
The region of the retina devoid of receptor cells because ganglion cell axons and blood vessels exit the eyeball there.
optic nerve
Cranial nerve II; the collection of ganglion cell axons that extend from the retina to the optic chiasm.
optic radiation
Axons from the lateral geniculate nucleus that terminate in the primary visual areas of the occipital cortex.
optic tract
The axons of retinal ganglion cells after they have passed the optic chiasm; most terminate in the lateral geniculate nucleus.
orientation column
A column of visual cortex that responds to rod-shaped stimuli of a particular orientation.
photon
A quantum of light energy.
photopic system
A system in the retina that operates at high levels of light, shows sensitivity to color, and involves the cones.
photoreceptor adaptation
The tendency of rods and cones to adjust their light sensitivity to match ambient levels of illumination.
photoreceptors
Neural cells in the retina that respond to light.
primary visual cortex (V1) or striate cortex
Also called area 17. The region of the occipital cortex where most visual information first arrives.
pupil
The aperture, formed by the iris, that allows light to enter the eye.
range fractionation
A hypothesis of stimulus intensity perception stating that a wide range of intensity values can be encoded by a group of cells, each of which is a specialist for a particular range of stimulus intensities.
receptive field
The stimulus region and features that affect the activity of a cell in a sensory system.
refraction
The bending of light rays by a change in the density of a medium, such as the cornea and the lens of the eyes.
retina
The receptive surface inside the eye that contains photoreceptors and other neurons.
retinal
One of the two components of photopigments in the retina.
rhodopsin
The photopigment in rods that responds to light.
rods
A class of light-sensitive receptor cells (photoreceptors) in the retina that are most active at low levels of light.
scotoma
A region of blindness caused by injury to the visual pathway or brain.
visual field
The whole area that you can see without moving your head or eyes.
wavelength
The length between two peaks in a repeated stimulus such as a wave, light, or sound.
acetylcholine (ACh)
A neurotransmitter produced and released by parasympathetic postganglionic neurons, by motoneurons, and by neurons throughout the brain.
act
Also called action pattern. Complex behavior, as distinct from a simple movement.
actin
A protein that, along with myosin, mediates the contraction of muscle fibers.
alpha motoneuron
A motoneuron that controls the main contractile fibers (extrafusal fibers) of a muscle.
amyotrophic lateral sclerosis (ALS)
Also called Lou Gehrig’s disease. A disease in which motoneurons and their target muscles waste away.
antagonist
A muscle that counteracts the effect of another muscle.
apraxia
An impairment in the ability to begin and execute skilled voluntary movements, even though there is no muscle paralysis.
ataxia
An impairment in the direction, extent, and rate of muscular movement; often caused by cerebellar pathology.
autoimmune disorder
A disorder caused when the immune system mistakenly attacks a person’s own body, thereby interfering with normal functioning.
ballistic movement
A rapid muscular movement that is often organized or programmed in the cerebellum.
basal ganglia
A group of forebrain nuclei, including caudate nucleus, globus pallidus, and putamen, found deep within the cerebral hemispheres.
central pattern generator
Neural circuitry that is responsible for generating the rhythmic pattern of a behavior such as walking.
cerebrocerebellum
The lowermost part of the cerebellum, consisting especially of the lateral parts of each cerebellar hemisphere.
closed-loop control mechanism
A control mechanism that provides a flow of information from whatever is being controlled to the device that controls it.
decomposition of movement
Difficulty of movement in which gestures are broken up into individual segments instead of being executed smoothly; a symptom of cerebellar lesions.
dystrophin
A protein that is needed for normal muscle function.
electromyography (EMG)
The electrical recording of muscle activity.
extrafusal fiber
One of the ordinary muscle fibers that lie outside the spindles and provide most of the force for muscle contraction.
extrapyramidal system
A motor system that includes the basal ganglia and some closely related brainstem structures.
fast-twitch muscle fiber
A type of striated muscle that contracts rapidly but fatigues readily.
final common pathway
The information-processing pathway consisting of all the motoneurons in the body. Motoneurons are known by this collective term because they receive and integrate all motor signals from the brain and then direct movement accordingly.
flaccid paralysis
A loss of reflexes below the level of transection of the spinal cord.
gamma motoneuron
Also called gamma efferent. A motor neuron that innervates the contractile tissue in a muscle spindle.
Golgi tendon organ
One of the receptors located in tendons that send impulses to the central nervous system when a muscle contracts.
huntingtin
A protein produced by a gene (called HTT) that, when containing too many trinucleotide repeats, results in Huntington’s disease in a carrier.
Huntington’s disease
Also called Huntington’s chorea. A progressive genetic disorder characterized by abrupt, involuntary movements and profound changes in mental functioning.
ideational apraxia
An impairment in the ability to carry out a sequence of actions, even though each element or step can be done correctly.
ideomotor apraxia
The inability to carry out a simple motor activity in response to a verbal command, even though this same activity is readily performed spontaneously.
innervation ratio
The ratio expressing the number of muscle fibers innervated by a single motor axon.
intrafusal fiber
One of the small muscle fibers that lie within each muscle spindle.
l-dopa
The immediate precursor of the transmitter dopamine.
mirror neuron
A neuron that is active both when an individual makes a particular movement and when an individual sees another individual make that same movement.
motoneuron
Also called motor neuron. A nerve cell in the spinal cord that transmits motor messages from the spinal cord to muscles.
motor plan
Also called motor program. A plan for action in the nervous system.
motor unit
A single motor axon and all the muscle fibers that it innervates.
movement
A brief, unitary activity of a muscle or body part; less complex than an act.
muscle fiber
A collection of large cylindrical cells, making up most of a muscle, that can contract in response to neurotransmitter released from a motoneuron.
muscle spindle
A muscle receptor that lies parallel to a muscle and sends impulses to the central nervous system when the muscle is stretched.
muscular dystrophy (MD)
A disease that leads to degeneration of and functional changes in muscles
myasthenia gravis
A disorder characterized by a profound weakness of skeletal muscles; caused by a loss of acetylcholine receptors.
myosin
A protein that, along with actin, mediates the contraction of muscle fibers.
neuromuscular junction (NMJ)
The region where the motoneuron terminal and the adjoining muscle fiber meet; the point where the nerve transmits its message to the muscle fiber.
nonprimary motor cortex
Frontal lobe regions adjacent to the primary motor cortex that contribute to motor control and modulate the activity of the primary motor cortex.
open-loop control mechanism
A control mechanism in which feedback from the output of the system is not provided to the input control.
paresis
Partial paralysis.
Parkinson’s disease
A degenerative neurological disorder, characterized by tremors at rest, muscular rigidity, and reduction in voluntary movement, that involves dopaminergic neurons of the substantia nigra.
plegia
Paralysis, the loss of the ability to move.
polioviruses
A class of viruses that destroy motoneurons of the spinal cord and brainstem.
premotor cortex
region of nonprimary motor cortex just anterior to the primary motor cortex.
primary motor cortex (M1)
The apparent executive region for the initiation of movement; primarily the precentral gyrus.
primary sensory ending
Also called annulospiral ending. The axon that transmits information from the central portion of a muscle spindle.
proprioception
Body sense; information about the position and movement of the body that is sent to the brain.
pyramidal system or corticospinal system
The motor system that includes neurons within the cerebral cortex and their axons, which form the pyramidal tract.
ramp movement
Also called smooth movement. A slow, sustained motion that is often controlled by the basal ganglia.
red nucleus
A brainstem structure related to motor control.
reflex
A simple, highly stereotyped, and unlearned response to a particular stimulus (e.g., an eye blink in response to a puff of air).
reticular formation
An extensive region of the brainstem (extending from the medulla through the thalamus) that is involved in arousal (waking).
reticulospinal tract
A tract of axons arising from the brainstem reticular formation and descending to the spinal cord to modulate movement.
rubrospinal tract
A tract of axons arising from the red nucleus in the midbrain and innervating neurons of the spinal cord.
secondary sensory ending
Also called flower spray ending. The axon that transmits information from the ends of a muscle spindle.
size principle
The idea that, as increasing numbers of motor neurons are recruited to produce muscle responses of increasing strength, small, low-threshold neurons are recruited first, followed by large, high-threshold neurons.
slow-twitch muscle fiber
A type of striated muscle fiber that contracts slowly but does not fatigue readily.
smooth muscle
A type of muscle fiber, as in the heart, that is controlled by the autonomic nervous system rather than by voluntary control.
spasticity
Markedly increased rigidity in response to forced movement of the limbs.
spinal animal
An animal whose spinal cord has been surgically disconnected from the brain to enable the study of behaviors that do not require brain control.
spinocerebellum
The uppermost part of the cerebellum, consisting mostly of the vermis and anterior lobe.
stretch reflex
The contraction of a muscle in response to stretch of that muscle.
striated muscle
A type of muscle with a striped appearance, generally under voluntary control.
striatum
The caudate nucleus and putamen together.
substantia nigra
A brainstem structure in humans that innervates the basal ganglia and is named for its dark pigmentation.
supplementary motor area (SMA)
A region of nonprimary motor cortex that receives input from the basal ganglia and modulates the activity of the primary motor cortex.
synergist
A muscle that acts together with another muscle.
tendon
Strong tissue that connects muscles to bone.
vestibulocerebellum
The middle portion of the cerebellum, sandwiched between the spinocerebellum and the cerebrocerebellum and consisting of the nodule and the flocculus.
