Lecture 3 - Different classes of Neurone

Question 1

What are the four morphological defined regions of a neurone?

Answer 1

1. Cell body
2. Dendrites
3. Axon
4. Presynaptic terminals

Question 2

What is the Soma?

Answer 2

Cell body, the metabolic centre of the cell which contains the nucleus which contains the genes of the cell and the endoplasmic reticulum - an extension of the nucleus where the cell’s proteins are synthesised.

Question 3

What are the two process that a neural cell give rise to?

Answer 3

Several short dendrites and one long tubular axon

Question 4

What are dendrites?

Answer 4

Branched in tree like fashion are the main apparatus for receiving incoming signals from other nerve cells.

Question 5

What are axons?

Answer 5

axon typically extends some distance from cell body and carries action potentials to other neurone. These action potentials are initiated at the initial segment

Question 6

[Bonus Historical Question] When was the first historic tracing and from whom?

Answer 6

1939 by Hodgkin and Huxley

Question 7

What are initial segments and how they provide advantageous traits to neurone

Answer 7

specialised trigger region from which the action potential propagate down the axon without failure or distortion at speeds of 1 to 100 m/s. The amplitude of the A.P remains constant at 100mV

Question 8

Neurones are classified into three large groups what are they?

Answer 8

Unipolar, bipolar, multipolar

Question 9

What are unipolar cells

Answer 9

Single primary process which usually gives rise to many branches. One branch serves as the axon and the others are the receptive surfaces or releasing terminals. . These cells predominate in the nervous systems of invertebrates in vertebrates they occur in the autonomic nervous system.

Question 10

What are Bipolar Neurones

Answer 10

They have an oval soma that gives rise to two distinct processes: dendritic structure that receives signals from periphery of the body and an axon that carries information toward the central nervous system.

Many cells are bipolar including those in the retina and in the olfactory epithelium of the nose.

Question 11

What are pseudo-unipolar cells?

Answer 11

Receptor neurones that convey touch, pressure and pain signals to the spinal cord are variants of the bipolar cells. These cells develop initially as bipolar cells but the two cell processes fuse into a single continuous structure that emerges from a single point in the cell body.

The axon splits into two branches one running to the periphery (sensory receptors) and another to the spinal cord.

Question 12

What are multipolar cells?

Answer 12

They are predominant in the nervous system of vertebrates. They typically have a single axon and many dendritic structures emerging from various points around the cell body.

Vary greatly in shape especially in the length of their axon. Usually extents of branches correlates wit number of synaptic contacts that other neurones make onto them

Question 13

There is an additional class for nerve cells into functional categories, what are they:

Answer 13

sensory neurons, motor neurons, interneurons

Question 14

What are sensory neurones

Answer 14

They carry information from the body’s peripheral sensors into the nervous system for perception and motor coordination.

Some primary sensory neurones are afferent [carried towards the central nervous system].

Question 15

What are motor commands?

Answer 15

Carries commands from the brain or spinal cord to muscles and glands (efferent information).

Question 16

What are interneurons

Answer 16

Most numerous and are subdivided into two classes: relay and local. Relay or projection interneurons have long axons and conveys signals over long distances. From one brain region to another.

Short interneurons have shorter axons because they form connection.

Question 17

Each Functional classification can be subdivided further. For instance…

Answer 17

Sensory System interneurons can be classified according to the type of sensory stimuli to which the respond; initial classification can be broken further into locations, density, and size.

E.g. Ganglion cell interneurons which respond to light are classified into 13 types based on the size of the dendritic tree, branching density and the depth of location in specific layers.