List the components of the central nervous system
Brain and spinal cord
List the components of the peripheral nervous system
Sensory receptors, peripheral nerves and their ganglia, and efferent
motor endings.
Define sensory (afferent) neuron
Brings information to the CNS.
Define motor (efferent) neuron
Takes information from CNS to the receptors.
Define effector
Causes a response to the change.
What are the general functions of neuroglial cells?
To support neurons in the PNS and CNS.
What is the structure, location, and function of astrocytes?
Largest cell with an elongated nucleus; located in gray and white
matter; regulates interstitial fluid and helps form blood-brain barrier
What is the structure, location, and function of oligodendrocytes?
Small cell with small nucleus; located around axons; en-sheaths and
myelinates axons in CNS.
What is the structure, location, and function of microglia?
Small cell with small, enlongated nucleus; located in brain and
spinal cord; acts in defense and immune-related functions.
What is the structure, location, and function of ependymal cells?
Cuboidal cell with round nucleus; lines cavities in the CNS; helps
make and circulate CSF
What is the structure, location, and function of schwann cells?
Slender cell with a large nucleus; surrounds axons; myelinates axons
What is the structure, location, and function of satellite cells?
Squamous-shaped cell with large nucleus; surrounds neuron; supports
nerve cell bodies in ganglia metabolic and physical support.
Define nerve cell body
main part of nerve
Define nissl body
Chromatophilic substance that fills the nerve. It is also called the
rough endoplasmic reticulum.
Define axon hillock
cone-shaped area of a nerve cell body that lacks nissl bodies and
gives rise to the axon
Define dendrite
neuron process that carries am impulse to the nerve cell body
Define axon
neuron process that carries an impulse away from the nerve cell body
Define axoplasm
Special name for cytoplasm of an axon
Define axolemma
Plasma membrane of an axon
Define axon collateral
Side branches along the length of an axon
Define myelin sheath
Structure formed by fused layers of schwann cell plasma membrane
Define sheath of schwann
Structure that occurs outside of the myelin sheath
Define node of ranvier
Interruption in the myelin sheath; also called the myelin sheath gap
Describe the unipolar neuron
One axon that branches from nerve cell body; in embryos and retina
Describe the bipolar neuron
Two axons branch from the nerve cell body; located in retina and
inner ear
Describe the pseudounipolar neuron
Two processes branch from the nerve cell body; dorsal root ganglion
Describe the multipolar neuron
One axon branches from nerve cell body and has lots of dendrites on
NCB; most common type in CNS
Define resting membrane potential
Difference in charge on either side of the plasma membrane
Why does a RMP occur?
It is due to the unequal concentrations of ions (K+ and Na+) inside
and outside of cell
How do you maintain the RMP?
Sodium-potassium pump
Define excitability
Ability to respond to a stimulus
Define action potential
A depolarization event that is conducted along the membrane of a
muscle cell or fiber
Define depolarization
Decreases membrane potential; the inside becomes less negative than
the resting potential
Define hyperpolarization
Increases membrane potential; the inside becomes more negative than
the resting potential
Define refractory period
Time when a neuron cannot generate a second action potential.
Define absolute refractory period
Time when a second AP cannot be generated
Define relative refractory period
Time when a second AP can be generated but only with a very strong stimulus.
Define all-or-none principle of impulse conduction
When a stimulus is strong enough to generate an action potential, the
impulse is conducted along the entire nerve at a constant speed and
maximal strength.
Define threshold stimulus
Opening and closing of channels in the membrane
Define subthreshold stimulus
May initiate a stimulus
Describe the structure, conduction speed, and location of A fibers
Myelinated, large fibers; fast conduction speed; sensory neurons from
the skin, skeletal muscles and joints.
Describe the structure, conduction speed, and location of B fibers
Myelinated, medium fibers; medium rate of speed; located in smaller
somatic sensory fibers from the skin and visceral sensory fibers and
visceral motor fibers
Describe the structure, conduction speed, and location of C fibers
Unmyelinated, small fibers; slow conduction speed; located in smaller
somatic sensory fibers from the skin, visceral sensory fibers and
visceral motor fibers
Define neuromuscular junction
Neuron to muscle cell
Define neuroglandular junction
Neuron to gland
Define synapse
Neuron to neuron
Describe the physiology of an EPSP
Makes the postsynaptic membrane potential less negative. Acts to
change sodium ion and potassium ion permeability.
Describe the physiology of an IPSP
Moves the membrane potential away from threshold. Acts to increase
potassium and chloride ion permeability.
Describe the sites of release, general actions and mechanisms of
inactivation for acetylcholine.
Released at some neuroglandular junctions, some neuromuscular
junctions and some synapses; binds to postsynaptic receptors;
inactivated by acetylcholinesterase.
Describe the sites of release, general actions and mechanisms of
inactivation for norepinephrine.
Released at some neuroglandular junctions, some neuormuscular
junctions and some synapses; binds to postsnyaptic receptors;
inactivated by MAO or COMT.
Define cholinergic effect
Nerve fiber that releases ACh
Define adrenergic effect
Nerve fiber that releases NE
Define white matter
Lacks cell bodies
Define gray matter
Nerve cell bodies are present
Define nerve
Bundle of nerve fibers in the PNS
Define ganglion
Aggregation of nerve cell bodies outside the CNS
Define tract
Bundle of axons in the CNS
Define ascending tract
Conduct impulses to higher levels in the CNS
Define descending tract
Conduct impulses from the brain to the spinal cord
Define horn
Main areas of gray matter in the spinal cord
Define Column
Arrangement of white matter in the spinal cord
Define endoneurium
Delicate connective tissue surrounding an individual nerve fiber
Define perineurium
Connective tissue that surrounds a fascicle of nerve fibers
Define fascicle
A bundle of nerve fibers within a peripheral nerve
Define epineurium
Dense, fibrous connective tissue that covers an entire nerve and
encloses all fascicles.