Nervous System

Question 1

Neurons

Answer 1

Neurons are highly polarized, terminally differentiated cells with a soma (cell body) and neurites (dendrites- info towards cell body or axons- away from cell body).

In the soma and the dendrites one can identify irregularly shaped masses of basophilic material (Nissl granules)

Question 2

Central nervous system

Answer 2

The CNS is made up by the brain and the spinal cord.
The brain is covered by meninges which are organised in: Dura mater, Arachnoid mater and Pia mater. Between the Arachnoid mater and the Pia mater is located the Subarachnoid space which contains a large number of blood vessels.

Question 3

Peripheral nervous system

Answer 3

Components of the PNS are nerve endings, peripheral nerves, plexuses and peripheral ganglia.

Sensory nerve endings can be either unencapsulated (‘free’ nerve endings) or encapsulated:

• Unencapsulated nerve endings consist of the terminal branches of sensory nerve fibres lying free in the innervated tissue and mediate thermal and painful sensations.
• Encapsulated nerve endings are surrounded by structural specialisation of nonneuronal tissue. The combination of a nerve and its encapsulation is also referred to as corpuscle. Examples of encapsulated nerve endings are the Paccinian corpuscle, the Meissner’s corpuscle and the muscle spindle.

Question 4

plexus

Answer 4

A plexus is a structure in which fibres within spinal and cranial nerves are redistributed without synapses to form other peripheral nerves. Examples are the Auerbach’s (myenteric) and Meissner’s plexus.

Question 5

Autonomic nervous system

Answer 5

• made up of sympathetic and parasympathetic
  division
  -Ganglia are clusters of neuronal cell bodies located outside the CNS
  -Glial cells are non-conductive cells in the nervous system with diverse structural, protective and nutritive roles. Glial cells outnumber neurons 10:1.
  -They can be classified in Oligodendrocytes / Schwann cells, Astrocytes, Microglia and Ependymal cells

Question 6

Astrocytes

Answer 6

help to maintain homeostasis and are instrumental in building the blood brain barrier.

Question 7

Oligodendrocytes and Schwann cells

Answer 7

support nerve conduction in the CNS and PNS

respectively by forming a myelin sheath that wraps around the axons.

Question 8

Microglia

Answer 8

originate from blood monocytes and are the smallest glial cell type. They act as phagocytes and remove CNS debris and constitute the brain’s immune system.

Question 9

Ependymal cells

Answer 9

remnants of embryonic neuroepithelium. They form a closely packed cuboidal or columnar epithelium lining the ventricles of the brain and the spinal canal of the spinal cord. The luminal surface is directly in contact with the cerebrospinal fluid (CSF).