The Cerebrum

Question 1

What are the 4 constituent parts of the cerebrum?

Answer 1

The telencephalon (cerebral hemispheres), the basal gangila, the olfactory bulb and limbic system

Question 2

What is the name of the structure that divides the 2 hemispheres? What structure joins them together?

Answer 2

The longitudinal fissure.

The corpus collosum - white matter commisural fibres.

Question 3

What is the cerebral cortex?

Answer 3

The outer 1.5-5mm of the cerebrum that is convoluted to increase the surface area. It is located superiorly to the brainstem and cerebellum.

Question 4

What is the difference between a gyrus and a sulcus?

Answer 4

Gyrus is the ‘hill’ or the ridge

Sulcus is the ‘valley’ or groove

Question 5

Where is the central sulcus?

Answer 5

Seperates the frontal and parietal lobes.

Question 6

Where is the lateral sulcus?

Answer 6

Seperates the frontal, parietal and temporal lobes.

Question 7

Where is the posterior sulcus?

Answer 7

Seperates the parietal and occipital lobes.

Question 8

What are commisural fibres?

Answer 8

They connect the 2 hemispheres together e.g. the corpus collosum.

Question 9

What are association fibres?

Answer 9

They connect areas within the same hemispheres.

Question 10

What are projection fibres?

Answer 10

They connect the brain to different levels of the spinal cord e.g. the CST.

Question 11

What is the internal capsule?

Answer 11

A subcortical structure containing white matter projection fibres

Question 12

What is the amydala?

Answer 12

A almond shaped structures deep in the temporal lobe that process memory, decisions and emotional reactions.

Question 13

What is the hippocampus?

Answer 13

A sea-horse shaped structure in the temporal lobe that processes memory and spatial navigation.

Question 14

Name the motor planning areas

Answer 14

Pre-mc
Supplementary mc
pre-frontal area

Question 15

What is the role of the supplementary motor cortex? Where is it located?

Answer 15

Initiates and plans movements that are bimanual in a sequence/order.
Located superiorly to the pre-mc

Question 16

What is the role of the pre motor cortex? Where is it located?

Answer 16

Controls trunk/girdle muscles
Pre-positions the body for movement.
Located inferior to the supplementary mc.

Question 17

What is the role of the pre - frontal area? Where is it located?

Answer 17

Instigates the decision to move. Located anterior of the brain.

Question 18

What is the role of the primary motor cortex? Where is it located?

Answer 18

Responsible for contralateral voluntary movement of skeletal muscle fibres.

Question 19

What is the main pathway that relays motor information? What other structures does it work with for movement?

Answer 19

The corticospinal tract.

• This works with the basal ganglia to plan/initiate movement
• It also works with the cerebellum to

Question 20

Describe the stages of this tract.

Answer 20

control/coordinate movement.
The command to move comes from the primary motor cortex in the pre-central gyrus of the frontal lobe. This command occurs after communication with the other areas of the motor cortex such as the supplementary cortex via association fibres.
The impulse travels from the primary motor cortex down via the corona radiate as the decussation of pyramids, passing through the internal capsule and the brain stem to reach the medulla. Here, 90% of fibres cross to the other side of the medulla as internal arcuate fibres. The remaining 10% do not cross at the medulla. The 90% travel down the lateral corticospinal tract to the anterior horn cell as their target cell in the ventral horn of the spinal cord. Before this occurs, they summate at an inter neurone. The 10% of fibres descend from the medulla via the anterior corticospinal tract and reach the level of the spinal cord and cross, targeting the anterior horn cell. Here they synapse.
The alpha motor neurone conveys this impulse to the skeletal muscle fibres (namely the extrafusal fibres of the muscle spindle) via a neuromuscular junction = movement.

Question 21

Describe the cortico-bulbar tract

Answer 21

This relays information from non-occulomotor cranial nerves from the brainstem to the cerebral cortex.

Question 22

Describe the spinocerebellar tract

Answer 22

This conveys unconscious proprioception and is unilateral. It targets the spinocerebellum.