• Coetzee et al p151-166
• Stevens and Lowe p77-98
• Wheater p117-142

1. Neurons are basic structural and functional units of the nervous system.
2. Neuroglia perform a support and nutritive function.

Slide 26:

Spinal Cord

Slide 82:

Spinal Cord

Slide 60:

Cerebellum

Neurons may be subdivided by:

1. Morphology:
   • Unipolar - one process a single axon
   • Bipolar - one axon and one dendrite
   • Multipolar - one axon and numerous dendrites
   • Pseudo-unipolar - an axon and a dendrite is fused for a small distance before splitting

2. Function:
   • Afferent neurons conduct impulses to the CNS
   • Efferent neurons conduct impulses from the CNS
   • Interneurons connect afferent and efferent neurons in the CNS
   • Excitatory neurons stimulate the next neuron
   • Inhibitory neurons suppress the next neuron

3. Length of the axon
   • Golgi type I neurons have a long axon that leaves the CNS
   • Golgi type II neurons have a short axon that does not leave the CNS

• Astrocytes give physical support and are subdivided into:
  • Protoplasmic astrocytes
  • Fibrous astrocytes

• Oligodendroglia form the myelin sheath in the CNS
• Microglia are the macrophages of the CNS
• Ependyma line the ventricles and spinal canal.

The PNS consists of:

1. Receptors that detect the stimulus and turns it into an electrical impulse. Receptors are specialized nerve endings or specialized nerve cells and may be sub classified by:
   • Location – eg muscle spindle inside skeletal muscle, etc
   • Type of sense organ – eg skin, visceral, etc
   • Type of stimulus – eg chemoreceptors, photoreceptors, etc

2. Afferent division, which conducts impulses from the receptors to the CNS.

3. Efferent division which consists of a single motor neuron and conducts impulses away from the CNS and which is subdivided into:
   • Somatic efferent division which supplies the skeletal muscles
   • Autonomic division consisting of two neurons, a preganglionic and a postganglionic neuron. This division supplies the viscera and is further divided into the sympathetic and parasympathetic divisions.

The presynaptic axon ends in a bulb-like structure, the end bulb or "boutons terminaux". There is a space, the synaptic cleft, between the end bulb and the cell membrane or post-synaptic membrane of the postsynaptic neuron. The end bulb contains synaptic vesicles that release neurotransmitters. These can either stimulate or inhibit the postsynaptic neuron.

Slide 32:

Neuromuscular Bundle

The myelin sheath serves as a biological insulation to facilitate impulse conduction. As it consists of consecutive layers of cell membrane, it is rich in phospholipids and cholesterol, which affects its staining characteristics. The junction where two adjacent Schwann cells meet and where the axon is not covered with myelin, is known as the node of Ranvier.

1. Neuron cell bodies
2. Support cells (Schwann cells and satellite cells)
3. Loose connective tissue.

Ganglia are subdivided into:

1. Sensory ganglia
   1. Cranial ganglia – associated with cranial nerves
   2. Spinal ganglia - associated with the dorsal roots of the spinal nerves
2. Autonomic ganglia – may be located inside organs eg wall of GI tract

• Motor neuron disease – spontaneous dying of motor neurons cause skeletal muscle weakness and eventual death
• Multiple sclerosis is an autoimmune disease that attacks the myelin sheath and has a tendency to strike young adults.