Chapter 38 – Neurons, Synapses, and Signaling: Key Vocabulary

Vocabulary flashcards covering major terms from Chapter 38: Neurons, Synapses, and Signaling.

nerve net

A weblike system of neurons characteristic of radially symmetric animals such as hydras.

nerves

Fibers composed primarily of bundled axons of neurons.

central nervous system (CNS)

Portion of the nervous system where signal integration occurs; in vertebrates, the brain and spinal cord.

peripheral nervous system (PNS)

Sensory and motor neurons that connect to the central nervous system.

glial cells (glia)

Non-neuronal cells that support, regulate, and nourish neurons; insulate axons and remove pathogens and dead cells.

reflexes

Automatic reactions to a stimulus mediated by the spinal cord or lower brain.

gray matter

Regions of dendrites and clustered neuron cell bodies within the CNS.

white matter

Tracts of axons within the CNS.

motor system

Efferent branch of the PNS composed of motor neurons that carry signals to skeletal muscles in response to external stimuli.

autonomic nervous system

Efferent branch of the PNS that regulates the internal environment; includes sympathetic, parasympathetic, and enteric divisions.

enteric nervous system

Network of neurons within the autonomic nervous system that directly and partly independently controls the digestive tract, pancreas, and gallbladder.

sympathetic division

Division of the autonomic nervous system that generally increases energy expenditure and prepares the body for action.

parasympathetic division

Division of the autonomic nervous system that generally enhances activities that conserve and gain energy, such as digestion and reduced heart rate.

brainstem

Collection of structures—the midbrain, pons, and medulla oblongata—functioning in homeostasis, movement coordination, and relaying information to higher brain centers.

midbrain

Part of the brainstem that receives and integrates sensory information and transmits it to the cerebrum.

pons

Portion of the brain that participates in automatic, homeostatic functions, such as regulating the breathing centers in the medulla.

medulla oblongata

Lowest part of the vertebrate brain that controls autonomic, homeostatic functions including breathing, circulation, swallowing, digestion, and vomiting.

hypothalamus

Ventral part of the forebrain that maintains homeostasis and coordinates the endocrine and nervous systems; secretes posterior pituitary hormones and releasing factors for the anterior pituitary.

thalamus

Integrating center of the forebrain that relays sensory input to specific cerebral cortex areas and regulates which information reaches the cortex.

cerebellum

Hindbrain structure that functions in unconscious coordination of movement and balance.

cerebrum

Dorsal forebrain portion composed of two hemispheres; integrating center for memory, learning, emotions, and other complex CNS functions.

biological clock

Internal timekeeper that controls an organism’s biological rhythms, marking time with or without environmental cues.

suprachiasmatic nucleus (SCN)

Group of hypothalamic neurons in mammals that functions as a biological clock.

cerebral cortex

Surface of the cerebrum; largest, most complex part of the mammalian brain containing nerve cell bodies.

lateralization

Segregation of functions between the left and right cerebral hemispheres.

corpus callosum

Thick band of nerve fibers connecting the right and left cerebral hemispheres, enabling them to process information together.

neuronal plasticity

Capacity of the nervous system to change with experience.

short-term memory

Ability to hold information, anticipations, or goals briefly and release them if irrelevant.

long-term memory

Ability to hold, associate, and recall information over a lifetime.

sensory receptor

Organ, cell, or structure that responds to specific external or internal stimuli.

receptor potential

Change in voltage across a receptor cell membrane proportional to stimulus strength.

sensory transduction

Conversion of stimulus energy into a change in membrane potential of a sensory receptor.

perception

Interpretation of sensory system input by the brain.

amplification

Strengthening of stimulus energy during transduction.

sensory adaptation

Tendency of sensory neurons to become less sensitive during repeated stimulation.

mechanoreceptor

Sensory receptor that detects physical deformation such as pressure, stretch, motion, or sound.

electromagnetic receptors

Receptors of electromagnetic energy such as visible light, electricity, or magnetism.

thermoreceptors

Receptors stimulated by heat or cold.

nociceptors

Sensory receptors that respond to noxious or painful stimuli; also called pain receptors.

pain receptors

Sensory receptors that respond to noxious or painful stimuli; also called nociceptors.

chemoreceptors

Sensory receptors that respond to chemical stimuli such as solutes or odorants.

olfaction

Sense of smell.

gustation

Sense of taste.

odorants

Molecules detected by olfactory sensory receptors.

tastants

Chemicals that stimulate sensory receptors in taste buds.

statocysts

Mechanoreceptors in invertebrates that use statoliths to function in equilibrium.

organ of Corti

Actual hearing organ in the vertebrate inner ear’s cochlear duct containing hair cells.

hair cells

Mechanosensory cells that alter nervous output when their hairlike projections are displaced.

outer ear

Region of the ear composed of the auditory canal and, in many birds and mammals, the pinna.

tympanic membrane

Eardrum; membrane between the outer and middle ear.

middle ear

Chamber containing the malleus, incus, and stapes that conveys vibrations from the eardrum to the oval window.

oval window

Membrane-covered opening through which sound waves pass from the middle ear to the inner ear.

inner ear

Region that includes the cochlea and semicircular canals.

cochlea

Complex, coiled organ of hearing that contains the organ of Corti.

round window

Point where vibrations of the stapes create pressure waves in the cochlear fluid.

utricle

Chamber in the vestibule behind the oval window that opens into the semicircular canals and aids balance.

saccule

Chamber in the vestibule behind the oval window that participates in balance.

semicircular canals

Three-part chamber of the inner ear that functions in maintaining equilibrium.

photoreceptors

Electromagnetic receptors that detect visible light.

compound eyes

Multifaceted eyes in insects and crustaceans consisting of many light-detecting focusing ommatidia.

ommatidium

Single facet of an arthropod compound eye.

single-lens eyes

Camera-like eyes found in some jellies, polychaetes, spiders, and many molluscs.

pupil

Opening in the iris that admits light; its size is regulated by iris muscles.

iris

Colored part of the eye formed by the anterior choroid; controls pupil size.

lens

Structure that focuses light onto photoreceptors.

retina

Innermost eye layer containing rods, cones, and neurons; transmits images to the brain via the optic nerve.

rods

Retinal photoreceptors sensitive to low light intensity.

cones

Retinal photoreceptors sensitive to color.

retinal

Light-absorbing pigment in rods and cones.

rhodopsin

Visual pigment of retinal and opsin that changes shape when it absorbs light.

fovea

Area at the retina’s center of focus where cones are highly concentrated.