Histology of Nervous Tissue

Question 1

What are the two types of cells that make up nervous tissue

Answer 1

1) Neurons
2) Supporting cells – PNS gliocytes
CNS gliocytes

Question 2

What is the difference between axons and dendrites?

Answer 2

1. AXONS – usually carry impulses away from cell body. Axons originate
   from the axon hillock.
2. DENDRITES – usually carry impulses towards cell body.

Question 3

What is Nissl substance

Answer 3

Found in the cytoplasm (cell body - soma - and dendrites) of neurons and consists of rER and ribosomes, responsible for protein synth in nerve cells. They stain deeply basophilic due to ribosomal RNA.

Question 4

What is a telonderon?

Answer 4

the terminal branches of an axon, which end in specialized structures called axon terminals or synaptic boutons.

Question 5

What are the characteristics of a telonderon (terminal branch of an axon)?

Answer 5

A. no myelin

B. Cytoplasm resembles perikaryon (no Nissl substance).

C. Synaptic Vesicles – transmitter substance.
1. Clear – Acetylcholine
2. Dense – Norepinephrine

D. Accumulation of filamentous material resembling desmosomes found along membrane
of presynaptic element. May hold synapse together.

Question 6

Name 3 types of synapses

Answer 6

1. AXOSOMATIC – Axon onto another nerve cell body.
2. AXODENDRITIC – Axon onto dendrite of another nerve cell.
3. AXOAXONIC – Axon onto another nerve cell axon.

Question 7

Describe the two types of receptor organs.

Answer 7

A. Encapsulated Nerve Terminal – associated with a capsule formed by
the continuation of the perineural epithelium of the nerve fibre. Two
types:

1. Thinly encapsulated receptor organs.
2. Thickly encapsulated receptor organs.

B. Nonencapsulated Nerve Terminal – not associated with a capsule.
Usually associated with a nonmyelinated (naked) nerve terminal

Question 8

Give 2 examples of thinly encapsulated receptor organs

Answer 8

Bulbous corpuscle (End bulbs of Krause) - mechanoreceptor

Encapsulated Tactile corpuscles (Meissner’s corpuscles)

Question 9

Give 4 examples of thickly encapsulated receptor organs

Answer 9

A. Lamellar (Pacinian) corpuscles
B. Neuromuscular (Muscle) spindles
C. Neurotendinous spindles (Golgi tendon organs)
D. Ruffini’s corpuscle

Question 10

Give 2 examples of nonencapsulated nerve terminals (receptor organs)

Answer 10

A. Free (and diffuse) nerve endings – Detect pain, warmth, cold, and touch.

B. Non-encapsulated tactile corpuscles (Merkel’s cells or disks) – pain

Question 11

List 7 functions of astrocytes

Answer 11

1. Provide structural support
2. Store glycogen and release glucose (energy reserve)
3. Regulate potassium ions in extracellular space
4. Insulate synaptic complexes
5. Modulate synaptic sensitivity (uptake of neurotransmitter molecules)
6. Become phagocytic with injury to CNS
7. Present antigens to T-lymphocytes

Question 12

Name the 2 types of neuroglia/gliocytes/ supporting cells of the PNS

Answer 12

A. Neurolemmocytes (Schwann cells) – responsible for myelin
formation of nerve processes in PNS. Can be stimulated to change into
phagocytes.

B. Ganglionic Gliocytes (Satellite cells) – single layer of supportive
cells around nerve cell bodies in ganglia.

Question 13

Name the two types of nerve fibres

Answer 13

Medullated (Myelinated) fibres
(motor and sensory nerves)

Non-medullated (Non-myelinated) fibres
(post-ganglionic nerves of autonomic system)

Question 14

What are the Nodes of Ranvier?

Answer 14

regular points of discontinuity (gaps) between successive Schwann cells along a myelinated nerve fibre.

Outermost neurolemmocyte cytoplasmic processes enclose the node in the PNS.

In CNS, nodes are not covered by cytoplasmic processes (exposed to extracellular space).

Question 15

what is an internodal segment

Answer 15

area of nerve process covered by Schwann cell sheath.

Question 16

What is a paranode

Answer 16

the internodal region immediately adjacent to a node. Many myelin incisures present in
this area.

Question 17

What are MYELIN INCISURES (Schmidt – Lantermann Clefts)

Answer 17

areas in myelin sheath where Schwann cell
cytoplasm remains during wrapping process.

Question 18

What are ganglia?

Answer 18

collections of nerve cells outside the CNS

Question 19

Give 2 examples of ganglia and where they are found

Answer 19

(a) Spinal ganglia
Found on dorsal roots of spinal nerves / large, pseudo-unipolar neurons /
associated with medullated nerves

(b) Sympathetic ganglia
Found throughout the body / small, multipolar neurons / associated with
non-medullated nerves