1. Nervous Tissue Study Questions
1. What are the three major functions and two major parts of the nervous system?
The three major functions are sensory, integrative, and motor. The two major parts
are the CNS, brain and the spinal cord and the PNS, everything but the brain and
spinal cord
2. Considering the structure of a myelinated neuron define the following terms and
list functions as appropriate:
a. cell body: contains the cytoplasm and nucleus
b. RER (Nissl bodies): rough endoplasmic reticulum.
makes grey matter grey
c. dendrite: nerve fibers or processes that extend from the cell body that conduct
electrical signals toward the cell body
d. axon: nerve fiber or process that extends from the cell body that conducts impulses
away from the cell body
e. axon hillock: cone shape. hillock meaning little hill. connector piece
f. axon terminal: the split ends of the axon
g. trigger zone: where action potential starts.
where the electrical current begins
2. h. cell membrane : surrounds the entire neuron including dendrites, cell body, axon and
synaptic ends.
i. synaptic end bulb: dilated ends of axon terminals with vesicles that contain
neurotransmitters
j. neurotransmitter: a chemical substance that is released at the end of a nerve fiber by the
arrival of a nerve impulse and, by diffusing across the synapse or junction, causes the
transfer of the impulse to another nerve fiber, a muscle fiber, or some other structure
k. myelin: whitish fatty sheath around most axons, cell membrane of axon insulates and
increases speed of conduction
l. node of Ranvier: gaps in the myelin sheath
m. neurolema: outer nucleated cytoplasmic layer of Schwann cell that encloses myelin
sheath
3. List and define three functional classifications of neurons.
Sensory (afferent) neurons- carry sensory information from sensory receptors in
different parts of the body into the CNS
Interneurons- integrative function, mainly located in CNS between sensory and
motor neurons. form the majority of neurons in the body
Motor (efferent) neurons- carry motor information from the CNS to the effector
4. List and define three structural classifications of neurons. Where are they typically
located?
3. Multipolar neuron- several dendrites and one axon extending from the cell body (most
neurons in the CNS)
Bipolar- one dendrite and one axon extending from the cell body. location eye, ear, and
nose.
Unipolar- one process extending from the cell body. location extends from fingers, toes
(skin), to the dorsal root ganglion.
5. Describe the structure, function, and location of the following neuroglial cells:
a. astrocytes
location; CNS
Structure; star shape
function; support, help maintain proper chemical environment, and help maintain and
regulate the blood brain barrier of the brain capillaries.
b. oligodendrocytes
location; CNS
structure: a few branch cell
function: produce myelin around axon
c. microglia
location: CNS
Function: phagocytosis, remove debris, damaged tissue and microbes
Structure:
4. d. ependymal
location: CNS; lines the central canal of the spinal cord and the blood vessels in the brain
called ventricles (choroid plexus)
function: forms and secretes cerebral spinal fluid, from blood plasma
structure: balloon like
e. satellite cells
Function: support, protect and nourish neuron cells.
location: PNS; surrounds neuron cell bodies in ganglia. side of spinal cord, dorsal root
ganglion
Structure: surrounds a neuron body
f. Schwann cells
location: PNS
function: CAN produce myelin around axon. grabs and holds onto a axon
structure: long links with gaps between them
6. How can an axon in the PNS repair itself?
must be an axon that is myelinated. the neuron cell body has to be intact. Some schwann
cells be functional (neurolemma) to form a regeneration tube. Scar tissue doesn't grow
too rapidly (can block the process)
7. Describe and define graded potentials-Both hyperpolarizing and depolarizing.
hyperpolarizing graded potential- the chemical stimulus causes ions to flow through
channels in the cell membrane so that the inside of the cell membrane becomes polarized,
more negative than the resting potential.
5. Depolarizing- a mechanical stimulus causes ions to flow through channels in the cell
membrane, so that the inside of the cell membrane becomes depolarized, less negative
(more positive) than the resting potential.
8. Define and describe the neuron resting membrane potential and the three
different gated ion channels
resting membrane is -70 multivolts (mv): positive charges accumulate close to the outside
surface of neuron in ECF. Negative charges are close to the inside surface in ICF of
neuron cell membrane.
The three different gated ion channels are Voltage, ligand (chemical), and mechanical.
9. Define and describe an action potential using the terms depolarization,
repolarization, Na+ channel, K+ channel.
an action potential has two main phases: depolarization- NA+ rushes in. and
repolarization- K+ flows out (resetting phase).
10. Explain the difference between continuous and saltatory conduction.
continuous conduction occurs in unmyelinated axons, slow, and goes step-by-step.
Saltatory conduction- occurs in myelinated axons, passes from one node of Ranvier to the
next. fast.
11. Describe the structure and function of a chemical synapse in detail.
a chemical synapse- a junction between neurons: the first neuron changes an electrical
current to a chemical signal that will drift to the 2nd neuron, the 2nd neuron will change
the chemical signal back to a electrical signal
12. Describe and define an EPSP and an IPSP in detail.
6. EPSP (excitatory post synaptic potential)- caused by an excitatory neurotransmitter which
depolarizes the postsynaptic neuron, making the inside more positive and generation of a
nerve impulse more likely.
IPSP (inhibitory postsynaptic potential)- caused by an inhibitory neurotransmitter which
hyperpolarizes the postsynaptic neuron, making the inside more negative and generation
of a nerve impulse more difficult.
7. EPSP (excitatory post synaptic potential)- caused by an excitatory neurotransmitter which
depolarizes the postsynaptic neuron, making the inside more positive and generation of a
nerve impulse more likely.
IPSP (inhibitory postsynaptic potential)- caused by an inhibitory neurotransmitter which
hyperpolarizes the postsynaptic neuron, making the inside more negative and generation
of a nerve impulse more difficult.
