anatomy ch 7 list 1

nervous system

the master controlling and communicating system of the body

sensory input

the information gathered from stimuli

integration

process that interprets sensory input and decides what should be done

motor output

a response that activates muscles or glands after sensory information is processed

central nervous system (CNS)

the brain and the spinal cord; integrating and command centers of the nervous system

peripheral nervous system (PNS)

the nerves that extend from the brain and spinal cord; carry impulses to and from the spinal cord

sensory/afferent division

nerves that convey impulses to the central nervous system from the sensory receptors in the body

motor/efferent division

nerves that carry impulses from the central nervous system to muscles and glands

somatic nervous system

allows conscious control of skeletal muscles

autonomic nervous system

regulates events in the body that are automatic like smooth or cardiac muscles and glands

neuroglia

groups of supporting cells in the CNS

astrocytes

abundant, star-shaped glial cells that brace neurons and connect them to capillaries; protect the neurons from harmful substances in the blood and control the chemical environment of the brain

microglia

spiderlike phagocytes that dispose of debris

ependymal

glial cells that line the central cavities of the brain and spinal cord; help circulate cerebrospinal fluid

oligodendrocytes

glial cells that wrap flat extensions around nerve fibers, creating myelin sheaths

schwann cells

cells that form myelin sheaths of nerve fibers in the PNS

satellite cells

protective, cushioning cells in the PNS

neurons/nerve cells

highly specialized cells that transmit messages from one part of the body to another

cell body

the metabollic center of the neuron

nissl substance

the rough endoplasmic reticulum of neurons

neurofibrils

intermediate filaments that help maintain the cell’s shape

dendrites

neuron processes that carry incoming signals towards the cell body

axon

single neuron process that generate nerve impulses and carry them away from the cell body

axon hillock

conelike region of the cell body of a neuron from which the axon arises

axon terminal

ends of the branches of axons; each end contains hundreds of tiny membranous sacs, which contain neurotransmitters

neurotransmitters

chemicals released by neurons that stimulate or inhibit other neurons to produce a response

synaptic cleft

small gap that separates neurons

synapse

functional junction between two neurons

myelin

waxy, fatty material that protects and insulates neurons and increases the rate of nerve impulses

myelin sheath

wrapping that encloses the length of an axon; speeds up nerve impulses

neurolemma

part of the Schwann cell that is external to the myelin sheath; “neuron husk”

nodes of ranvier

gaps or indentations between Schwann cells forming the myelin sheath at regular intervals

multiple sclerosis

autoimmune disease in which the myelin sheaths of neurons are destroyed and converted into hardened sheaths (scleroses); this causes nerve impulses to short circuit

nuclei

clusters of cell bodies in the CNS

ganglia

clusters of cell bodies in the PNS

white matter

area of the brain that consists of dense collections of myelinated fibers

grey matter

area of the brain that consists of unmyelinated fibers and cell bodies

sensory/afferent neurons

neurons that carry impulses from sensory receptors to the brain; the cell bodies are always found in ganglion outside of the CNS

proprioceptors

receptor located in a muscle or tendon; concerned with locomotion, posture, and muscle tone

motor/efferent neurons

neurons that carry impulses from the CNS to viscera, muscles, and glands

interneurons

neurons that connect motor and sensory neurons in neural pathways

multipolar neuron

a neuron that has several processes extending from the cell body; most common structural type; all motor and association neurons

bipolar neuron

a neuron that has two processes extending from the cell body; sensory processing receptors

unipolar neuron

a neuron that has a single process extending from the cell body which branches into central and peripheral processes that both function as axons; the peripheral process has dendrites at its end

tract

a collection of nerve fibers in the CNS that have the same origin, termination, and function

polarization

when a neuron is inactive; fewer positive ions (Na⁺) are outside of the cell than are inside (K⁺); the inside of the cell is negative

depolarization

a process where a stimulus causes the membrane of a neuron to become permeable to allow Na⁺ ions to enter the neuron, changing the polarity of the normally negative neuron

graded potential

when the inside of a neuron is more positive but not positive enough to trigger action potential

action potential

a long-distance signal that a neuron sends after the change in polarity from depolarization meets the neuron’s threshold

repolarization

the process almost immediately after action potential is sent, where the neuron’s plasma membrane becomes permeable to K⁺ ions and allows the charge of the neuron to be reset to negative

reflex

rapid, predictable, and involuntary responses to stimuli

somatic reflex

all reflexes that stimulate skeletal muscle cells

autonomic reflexes

regulate the activities of smooth and cardiac muscles and glands