KA 1: Divisions of the nervous system and parts of the brain (a) CNS Central Nervous System (f) Localisation of brain functions The Nervous System (b) PNS Peripheral Nervous System (e) Cerebral Cortex (c) Medulla and Cerebellum (d) Limbic System

By the end of this section you will be able to ….. Describe the localisation of the 3 functions parts of the cerebral cortex State that the brain has two hemispheres. Describe the function of the two hemispheres and how those two hemispheres communicate with each other Describe how brain injury can occur and how we can monitor this

Do you remember the 3 functions of the cerbral coretx? The functions of the cerebral cortex include: Receiving sensory information Coordinating voluntary movement Making decisions in the light of experience. Each of these functions has a specific area in the brain…

Coordinating voluntary muscle movements Receiving sensory information Making decisions New diagram to be added from pg 213 of textbook

Localisation of brain functions The cerebral cortex contains 3 types of functional areas which performs its own distinct function: Sensory: receives information from receptors e.g. touch receptors in skin Association: analyses and interprets information and ‘makes decisions’. Motor: receives information from the association areas and ‘carries out orders’ by sending motor impulses to the appropriate effectors (e.g. muscles).

This is only found on the left hemisphere of the brain. New diagram to be added from pg 213 of textbook This is only found on the left hemisphere of the brain.

Two Hemispheres The cerebrum is divided into two cerebral hemispheres (left & right). The left hemisphere deals with information from the right visual field and controls the right side of the body. The reverse is true for the right hemisphere.

How does information get from one side to the other?

Corpus Callosum The corpus callosum is a large nerve bundle which connects the two hemispheres. This allows fast communication between hemispheres allowing the brain to act as a whole.

Monitoring Healthy Brain Activity

What do you think would happen if the corpus callosum was damaged? ‘Split Brain’

‘Split Brain’ Patients During operations to relieve intractable epilepsy a patients corpus callosum is cut and the two hemispheres cannot communicate. This can result in the patient having a ‘split brain’.

‘Split Brain’ Patients https://www.youtube.com/watch?v=ZMLzP1VCANo (4:35)

‘Split Brain’ Patients This is because only the left hemisphere contains the motor speech area and it processes what the right side see’s. It is as if the patient has not seen the word ‘key’ but really it is because the right hemisphere cannot communicate with the left hemisphere. A patient is asked to focus on the black dot in the centre and tell us what word they see he will say ‘spoon’.

‘Split Brain’ Patients He is now asked to use his left hand and pick up the object that matches the word he see’s. As his left hand is controlled by his right hemisphere the patient will pick up what the left visual field see’s. Since no information passes between the hemispheres they actually pick up the key!

Brain Injury Accidents, tumours, lesions and disease can injure certain areas of the brain as well.

Frontal lobe damage can cause a person to go from mild-mannered and dependable to ill-tempered and unreliable. Extensive damage by lesions to the speech motor area of the brain can result in people being unable to articulate words despite understanding them.

Electroencephalograms (EEGs) Excited EEGs record the cerebrums electrical activity over 20-30 mins. Densely packed spikes mean a higher level of electrical activity, EEGs are not precise as they cannot tell us which are of the brain is the problem. They are used to diagnose comas and brain death. Relaxed Drowsy Asleep Deep sleep

Functional magnetic resonance imaging, fMRI scans locate the area of the brain being used by changes in blood flow to that area. https://www.youtube.com/watch?v=0uSYLy9itgg

Positron-emission tomography, PET scans can locate areas of the brain with high metabolic activity (increased demand for glucose and oxygen) using a harmless isotope.