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BJU Biology - Ch 23
BJU Biology 4th edition - Chapter 23
| Term | Definition |
|---|---|
| accommodation | The desensitization of sensory receptors after a period of stimulation. |
| action potential | The nerve impulse that results when sodium ions rush into the cytoplasm after stimulation. |
| autonomic nervous system (ANS) | The involuntary portion of the peripheral nervous system. |
| axon | The portion of a neuron that carries impulses away from the cell body. |
| brain | The portion of the central nervous system of vertebrates that is encased in the skull; composed mainly of neurons. |
| cell body | The part of the neuron with the greatest diameter; contains the nucleus and cytoplasmic organelles. |
| central nervous system (CNS) | The part of the nervous system consisting of the brain and spinal cord. |
| cerebral cortex | The gray matter of the cerebrum. |
| cerebrospinal fluid | The fluid that nourishes and protects the brain and spinal cord and that flows between the two inner meninges. |
| cerebellum | A part of the brain; monitors and adjusts body activities involving muscle tone, body posture, and equilibrium. |
| cerebrum | The part of the brain containing major motor and sensory centers; controls voluntary muscle activity; the area of conscious activity. |
| choroid | The thin middle layer of the eyeball; contains blood vessels for nourishing the retina. |
| cochlea | A snail-shaped division of the inner ear that functions in sound perception. |
| cone | One of the cone-shaped receptors in the eye; sensitive to colors. |
| cornea | The transparent anterior portion of the sclera of the eye. |
| dendrite | Part of the neuron that receives nerve impulses and transmits them toward the cell body. |
| dynamic equilibrium | An organism's maintaining a steady, balanced living state by expending energy; the ability of the body to respond automatically to position changes while it is moving. |
| external auditory canal | The canal from the outer ear to the eardrum. |
| hypothalamus | The region of the brain that controls involuntary activities, emotional expressions, appetite for food, and release of certain hormones. |
| interneuron | A neuron located in the central nervous system; transmits an impulse from a sensory neuron to another neuron. |
| iris | The colored portion of the eye. |
| lens | The transparent structure within the eye that focuses light rays on the retina. |
| medulla oblongata | A part of the brain; the relay center between spinal cord and brain; contains several reflex centers. |
| meninges | The protective coverings of the brain and spinal cord. |
| midbrain | The structure between the thalamus and pons that controls body movements and posture as well as vision and hearing reflexes. |
| motor neuron | A neuron that receives impulses from the central nervous system and stimulates muscles or glands. |
| myelin sheath | The white, fatty membrane that protects neurons. |
| neuron | The functional unit of the nervous system; the cell that receives and distributes nerve impulses. |
| neurotransmitter | A chemical that a neuron releases into the synaptic cleft for the purpose of stimulating receptor proteins in the membrane of the next neuron. |
| ossicle | The bones in the middle ear; malleus, incus, stapes. |
| oval window | A membrane-covered opening of the inner ear which receives vibrations transmitted from the ossicles. |
| parasympathetic nervous system | A system of neurons that helps the body return to normal processes after a stressful situation. |
| peripheral nervous system (PNS) | The division of the nervous system containing the nerves that originate in the central nervous system and the sensory organs. |
| pons | A rounded portion of the lower brain that relays information from one side of the brain to the other; contains reflex centers. |
| pupil | The circular opening in the iris of the eye. |
| reflex arc | A series of neurons that produces a single reaction in response to a stimulus. |
| resting potential | The relative charge difference between the inside and the outside of a neuron. |
| retina | The innermost layer of the eyeball; composed of specialized neurons and their fibers. |
| rod | One of the sensory receptors in the eye that is not sensitive to color but can rapidly discern movements and is important in night vision. |
| sclera | The outer layer of the eye; the "white of the eye." |
| semicircular canal | A structure in the inner ear that maintains dynamic equilibrium. |
| sensory neuron | A neuron that carries impulses toward the spinal cord or the brain. |
| sensory receptor | A specialized dendrite of sensory neurons found in sensory organs. |
| spinal cord | The nervous tissue that conducts messages between the brain and the peripheral body parts. |
| static equilibrium | The sense of body position a person has when not moving. |
| sympathetic nervous system | A system of neurons that helps the body adjust to stressful situations. |
| synapse | A space between an axon and a dendrite or between the end of an axon and the body structure it affects. |
| synaptic cleft | The space between the axon terminal and a neuron. |
| thalamus | The brain region that receives general sensations and relays impulses to the parietal lobe. |
| tympanic membrane | A circular membranous structure that serves to transmit sound vibrations to an ear cavity; the eardrum. |
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marchscience
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