Nervous System- Histology

Front 1

What are the two anatomical divisions of the nervous system?

Back 1

-CNS-brain and spinal cord
-PNS- peripheral nerves and ganglia

Front 2

What are the two functional divisions of the nervous system?

Back 2

-Afferent neurons (from periphery to the brain)
-Efferent neurons (out going into: going out of brain)
>somatic (voluntary)
> autonomic (involuntary)

Front 3

What are the two types of cells in the nervous system?

Back 3

-neurons (nerve cells)- conduct electrical impulses

- Glial cells support, nurture, and protect neurons

Front 4

What are the three types of neurons?

Back 4

Bipolar neurons
multipolar neurons
pseudounipolar neurons

Front 5

What are bipolar neurons comprised of?

Back 5

-single axon and single dendrite
-located in sense organs

Front 6

What are multipolar neurons?

Back 6

-single axon and multiple dendrites
-most common type

Front 7

What are pseudounipolar neurons?

Back 7

-Single process extends from cell body and branches into an axon and dendrite
-Originate embryologically as bipolar cells whose axon and dendrite later fuse into a single process
-located in spinal and cranial ganglia

Front 8

What is the function of dendrites?

Back 8

-Receive stimuli from sensory cells, axons, or other neurons
-Convert these signals into small electrical impulses which are transmitted to soma
-Often have arborized terminals which permit a neuron to receive very large number of stimuli

Front 9

What are the components of the Neuronal Cell Body?

Back 9

-Nucleus: large, with dispersed chromatin and large nucleolus

-Nissil bodies: polyribosomes and rER; they abundant in larger neurons

-Neurofilaments
Intermediate filaments
Part of cytoskeleton

-Microtubules: 24 nm in diameter and moves organelles within cell

-Axon hillock: Lacks rER and ribosomes; Contains many microtubules and neurofilaments

Front 10

What is the function of axons?

Back 10

conduct impulses away from the soma to the axon terminals

Front 11

Important facts about axons

Back 11

While dendrites taper, axons retain a constant diameter along their course. Diameter is proportional with size of cell body. Length is highly variable.

Axons may branch

Cytoplasm = axoplasm (devoid of rER)

Plasma membrane = axolemma

Terminate in axon terminals from which impulses are passed to another neuron or other type of cell

Front 12

What is the myelin sheath produced by?

Back 12

-Oligodendrocytes in the -CNS
-Schwann cells in the PNS


Individual axon enveloped by a myelin sheath = nerve fiber

Front 13

T/F: Axons are onloy myelinated.

Back 13

F. They may be myelinated or unmyelinated

Front 14

What are two disorder of myelin?

Back 14

- Multiple sclerosis

-Guilain-Barre syndrome

Front 15

What is the functional classification of peripheral nerves?

Back 15

-Many nerve fibers are surrounded by connective tissue sheaths
-Functional classification
>Sensory nerves
>Motor nerves
>Mixed nerves

Front 16

How are peripheral nerves organized

Back 16

Peripheral nerves are organized in bundles surrounded and separated by connective tissue much like those of skeletal muscle: endoneurium (around single nerve fibers or axons), perineurium (dense epitheloid tissue around several fibers, forming a fascicle), and epineurium (around several fascicles, forming a nerve).

Front 17

What is a perineurium?

Back 17

-Layer of dense connective tissue that surrounds each bundle (fascicle) of nerve fibers
-Inner surface consists of flattened epithelioid cells joined by tight junctions (barrier function)

Front 18

What is a epineurium?

Back 18

-Fibrous dense connective tissue that forms the external coat of nerves

Front 19

What is a endoneurium?

Back 19

-Thin layer of loose connective tissue surrounding individual nerve fibers

Front 20

What does White Matter contain?

Back 20

Contains mostly myelinated but also some unmyelinated nerve fibers

Front 21

What are two specialized receptors?

Back 21

Meissner's corpuscles and Pacinian corpuscles

Front 22

What is Meissner's corpuscles responsible for?

Back 22

-fine touch

-encapsulated receptors in dermis (skin)

-Connective Tissue capsule enveloping nerve terminal and its Schwann cell

Front 23

What is Pacinian corpuscles
responsible for?

Back 23

-pressure, touch, vibration


-Encapsulated receptor in dermis, joints, and mesenteries

-Multilayered capsule of fibroblasts, collagen, and fluid, surrounding a nerve terminal

Front 24

What is the muscle spindle and what is its function?

Back 24

-Sensory organ within skeletal muscle

-Function: Stretch receptor

-8-10 modified skeletal muscle fibers (intrafusal fibers) with central nuclei, all surrounded by CT capsule

Front 25

Is the death to the cell body irreversible?

Back 25

Yes. Death to the cell body is irreversible, but damaged axons can regenerate.