C Lecture 1: Introduction to the Human Brain

Question 1

What are the different types of neurons?

Answer 1

(a) Bipolar neurone - a neurone with two projections arising from the cell body - a dendrite and an axon each with further projections. These are found mainly in organs that deal with sensation e.g. eye, nose etc.
(b) Pseudo-unipolar - only have one projection coming from the cell body. However immediately as it arises, it splits into two. They allow for information to bypass the cell body i.e. from the dendrites and into the axon. These are also found in organs that deal with special sensation.

(c) Multipolar neurons have multiple projections form the cell body and one axon. These are the most numerous type of neurone. Mainly motor neurones are multipolar.

Question 2

What is the relationship between axon diameter and the speed of transmission?

Answer 2

The diameter of an axon is proportional to how fast information is transmitted. The larger the diameter, the faster the transmission. Vertebrates neurones’ have a small diameter, to get around these we therefore have myelin.

Question 3

What is the function of myelin?

Answer 3

An axon is covered in myelin sheath - an insulating substance that allows for faster conduction.

Question 4

What are the anatomical sub-divisions of the CNS?

Answer 4

7

• Cerebral hemispheres
• Diencephalon
• Midbrain
• Medulla Oblongata
• Pons
• Cerebellum
• Spinal Cord

Question 5

What are gyri and sulci?

Answer 5

Gyri are folds and the Sulci are grooves. Both fo which are seen on the cerebral cortex.

Question 6

What is the corpus callosum?

Answer 6

The corpus callosum links both hemispheres. White matter is a collection of axons of neurons.

Question 7

What are the 4 lobes of the brain? What fissures separate them?

Answer 7

• Frontal Lobe
• Occipital Lobe
• Temporal Lobe
• Parietal Lobe

The central lobe separates the frontal and parietal love. The lateral tissue divides the frontal lobe and partial lobes superiorly from the temporal lobe inferiorly. The parieto-occiptal lobe operates the parietal lobe from the occipital lobe.

Question 8

What is the longitudinal fissure?

Answer 8

Also known as the superior saggital fissure. This separates the two hemispheres.

Question 9

What is the difference between grey and white matter?

Answer 9

The surface of the hemisphere is composed of grey matter - grey matter is neural cell body. There is also deep collections of grey matter in the brain basal ganglia and other structures).

Question 10

What is Lissencephaly?

Answer 10

Lissencephaly - smooth brain. In embryology, our brains start off smooth, lacking folds and grooves. Due to genetics some babies do not acquire this pattern of sulci and gyri and are born with lissencephaly. They have motor and sensory problems and retardation is able to survive. The folding allows us to increase the SA of our brain so we can perform higher functions. This is why they are not found in animals without such functions.

Question 11

What is the significance of the pre-central gyrus and the post-central gyrus?

Answer 11

Anterior to the central sulcus is the precentral gyri - this is a ridge of grey matter. Posterior to the central sulcus is the post-central gyrus. These have special functions. The pre-central gyrus functions as the motor cortex - it initiates motor control. The post-central gyrus functions as the primary sensory cortex - receives sensory function.