Term | Definition |
the central nervous system | composed of the brain and spinal cord |
the peripheral nervous system | composed of nerves extending to the outlying or peripheral parts of the body |
autonomic nervous system | a subdivision of the peripheral nervous system that consists of structures that regulate the body's autonomic or involuntary functions |
neurons | nerve cells that conduct impulses |
glia | support cells that support neurons by holding them together |
cell body | the main part of the neuron |
dendrites | branching projections that transmit impulses to the neuron cell bodies |
axon | one elongated projection from the cell body that transmits impulses away from the cell body |
sensory neurons | transmit impulses to the spinal cord and brain from all parts of the body. Also called afferent neurons. |
motor neurons | transmit impulses away from the spinal cord and brain to muscle and glandular epithelial tissue. Also called efferent neurons. |
interneurons | conduct impulses from sensory neurons to motor neurons |
myelin | white, fatty substance formed by schwann cells that wrap around some axons outside the CNS |
nodes of Ranvier | indentations between adjacent schwann cells |
neurilemma | the outer cell membrane of a schwann cell; play an important role in the regeneration of cut or injured axons |
glioma | a common type of brain tumor |
astrocytes | star-shaped glia cells that have extensions that attach to blood vessels in the brain |
blood brain barrier | two-layer structure that separates the blood tissue and nervous tissue to protect vital brain tissue from harmful chemicals in the blood |
microglia | smaller than astrocytes; act as microbe-eating scavengers by helping clean up cell damage resulting from injury or disease |
oligodendrocytes | help hold nerve fibers together and produce the fatty myelin sheaths that envelope nerve fibers in the CNS |
schwann cells | glia cells that also form myelin sheaths, but only in the PNS |
nerve | a group of peripheral nerve fibers (axons) bundled together; they usually have a myelin sheath and appear white |
tracts | bundles of axons in the CNS that are myelinated and form the white matter of the brain and spinal cord |
gray matter | brain and spinal cord tissue composed of cell bodies and unmylinated axons |
endoneurium | thin wrapping of fibrous connective tissue surrounding each axon |
fasicles | groups of wrapped axons |
perineurium | thin, fibrous covering of fasicles |
epineurium | tough, fibrous sheath that covers the whole nerve |
action potentials | nerve impulses that travel over routes made of neurons |
reflex arc | the basic type of neuron pathway |
two-neuron arc | pathway that consists of sensory and motor neurons |
three-neuron arc | pathways that consists of sensory, interneurons, and motor neurons |
receptors | the beginnings of dendrites of sensory neurons |
ganglion | a group of nerve cell bodies located in the PNS |
synapse | a space separating the axon ending from the dendrites of another neuron |
effectors | muscles or glands that form a synapse with a motor neuron axon which puts the nerve signals into effect |
reflex | response to nerve conduction over a reflex arc |
nerve impulse | a self-propagating wave of electrical disturbance that travels along the surface of a neuron's plasma membrane; has to be initiated by a stimulus |
synaptic knob | a tiny bulge at the end of a terminal branch of a presynaptic neuron's axon; contain vesicles that contain neurotransmitters |
synaptic cleft | the space between the synaptic knob and the plasma membrane of a postsynaptic neuron where neurotransmitters are released |
neurotransmitters | chemicals by which neurons communicate |
medulla oblongata | the lowest part of the brainstem; contains white and gray matter that form the reticular formation (net-like) |
pons and midbrain | parts of the brainstem that contain white matter with scattered bits of gray matter |
reflex centers | located in the medulla; impulses from these centers control heartbeat, respiration, and blood vessel diameter |
cerebellum | 2nd larges part of the brain; it allows for a huge amount of information processing and plays an essential part in the production of normal movements |
arbor vitae | white matter tracts of the cerebellum that branch into a tree-like patterm |
diencephalon | a small part of the brain located below the cerebellum and above the midbrain. |
3 parts of the diencephalon | hypothalamus, thalamus, and the pineal gland |
hypothalamus | exerts major control over virtually all internal organs; maintains the body's water balance through antidiuretic hormone |
thalamus | dumbell-shaped section of gray matter that produces sensations of pleasantness and unpleasantness |
pineal gland | receives sensory information about the strength of light seen by the eyes and adjust its output with melatonin |
cerebrum | largest, uppermost part of the brain |
gyri | ridges in the cerebrum |
sulci | grooves of the cerebrum |
fissures | deepest sulci |
cerebral cortex | thin layer of gray matter make up of neuron dendrites and cell bodies that forms the surface of the cerebrum |
basal nuclei (basal ganglia) | islands of gray matter in the interior cerebrum that produce automatic movements and posture |
cerebrovascular accident (CVA) | a hemorrhage from or cessation of blood flow through cerebral blood vessels; a stroke |
17"-18" | length of spinal cord if you are of average height |
8 | number of cervical nerve pairs |
12 | number of thoracic nerve pairs |
5 | number of lumbar nerve pairs |
5 | number of sacral nerve pairs |
1 | number of coccygeal nerve pair |
31 | total number of spinal cord nerve pairs |
12 | number of cranial nerve pairs |
ascending tracts | conduct impulses to the brain (sensory) |
descending tracts | conduct impulses away from the brain (motor) |
meninges | tough, fluid-containing membrane surrounding the spinal cord and brain |
dura mater | the tough outer layer covering the brain |
arachnoid mater | middle layer resembling a cobweb; contains CSF |
pia mater | innermost layer covering the spinal cord itself |
dermatomes | skin surface areas that are supplied by a single spinal nerve |
two divisions of the autonomic nervous system | sympathetic and parasympathetic nervous systems |
autonomic neurons | motor neurons that make up the autonomic nervous system |
ganglia | "junction boxes" where axons connect in the autonomic nervous system |
preganglionic neurons | autonomic neurons that conduct impulses between the spinal cord and the ganglion |
postganglionic neurons | the dendrites and cell bodies that connect the synapse from the preganglionic axons |
autonomic or visceral effectors | the tissues to which autonomic neurons conduct impulses (cardiac muscle, smooth muscle, and glandular epithelial tissue) |
sympathetic nervous system | functions as an emergency system; fight or flight response |
parasympathetic nervous system | regulates functions that are autonomic or involuntary in ways that maintain or restore homeostasis |