The Cerebral Hemispheres

Question 1

What are the basal nuclei?

Answer 1

Discrete collection of neuronal cell bodies

Question 2

Where is are the gyri?

Answer 2

Immediately in front of the central sulcus (precentral gyrus) and one behind in the parietal lobe (post central gyrus)

Cingulate gyrus is on medial surface of cerebral hemispheres are is found round the corpus callosum

The frontal and temporal lobe is further divided onto superior, middle and inferior gyri

Transverse temporal gyri - enters temporal lobe via insula

Question 3

Describe the basic fucntion of each area of the brain

Answer 3

Posteior is sensory and anterior (frontal lobe) is motor
• Parietal lobe - general sensory (pain, touch, vibration etc)
• Occipital lobe - special sensory (vision)
• Temporal lobe - special sensory (hearing and smell)

Medial potions (limbic system) - storage and retrieval of processed information

Question 4

What is the precentral gyrus (area 4) responsible for?

Answer 4

Primary motor cortex:
Somatotopic representation of contralateral half of body (motor homunculus) - takes care of muscles on opposite side of the body

Question 5

What is the prefrontal cortex (area 6,8) responsible for?

Answer 5

Cognitive function of higher order - intellect, judgement, prediction and planning

The prefrontal cortex forms the pattern in which the muscles have to work

Question 6

What is the function of the inferior frontal gyrus (area 44, 45)?

Answer 6

Broca’s area of motor speech:
Puts patterns of sentences and words which will send signals to the primary motor complex to innervate muscle of speech (i.e. tongue, lips, palate) to form a pattern so that words come out in the right order.

Question 7

What is the motor and sensory homunculus?

Answer 7

Somatotopic representation - specific neuron in these regions will go to these specific muscles

Question 8

What part of the body is represented by the lateral motor and sensory homunculus?

Answer 8

The tongue

Question 9

What part of the body is represented by the medial motor and sensory homunculus?

Answer 9

Genitals and toes

Question 10

Describe how the homunculus represents muscles

Answer 10

The region in the brain specific for a muscle is NOT directional proportional for the size of the area that it’s going to

I.e. hand is so small but has larger region in the brain that a limb, as there are a lot finer movement in the hands.

Question 11

What is the function of the post-central gyrus (area 3, 1, 2)?

Answer 11

Primary sensory area:

Receives general sensations from the contralateral half of the body –> sensory homunculus

Question 12

What are the three gyri in the parietal lobe?

Answer 12

• Primary sensory area
• Superior parietal lobule
• Inferior parietal lobule

Question 13

What is the function of the superior parietal lobule?

Answer 13

Association area - interpretation of general sensory information (sensory association area) and conscious awareness of contralateral half of body

Question 14

What is the function of the inferior parietal lobule?

Answer 14

Interface between somatosensory cortex and visual and auditory association areas. In dominant hemisphere, contributes to language functions.

Question 15

What is the superior temporal gyrus (areas 41,42)?

Answer 15

Primary auditory cortex

Question 16

What are the different gyri in the temporal lobe?

Answer 16

• Superior temporal gyrus
• Auditory association areas
• Inferior surface of lobe

Question 17

What is the function of the auditory association areas (wernicke’s area)?

Answer 17

In dominant hemisphere it is the wernicke’s area.

Understanding of spoken word and has connections with other language areas – it is unilateral and important for understanding speech.

Question 18

What fibres do the inferior surface on the temporal lobe receive?

Answer 18

Fibres of olfactory tract – conscious appreciation of smell

Question 19

What are the gyri in the occipital lobe?

Answer 19

Primary visual cortex (area 17) and visual association cortex (areas 18, 19)

Question 20

Where is the location of the primary visual cortex (area 17) of the occipital lobe?

Answer 20

On the medial surface, either side of the calcimine sulcus.

Question 21

What is the function of the visual association cortex (areas 18, 19) of the occipital lobe?

Answer 21

It is the rest of the occipital lobe, and interprets visual images

Question 22

What is the limbic lobe (functional area)?

Answer 22

The medial surface of the cerebral hemisphere has area which together form a functional limbic lobe involved in memory and emotional aspects of behaviour.

Question 23

What does the limbic lobe (functional area) contain?

Answer 23

It includes the cingulate gyrus, the hippocampus (medial aspect of temporal lobe), parahippocampal gyrus, and the amygdala (subcortical grey matter close to temporal pole)

Question 24

What are the two language areas and what occurs if there is damage to these areas?

Answer 24

• Broca’s area - motor speech
• Wernicke’s area - association area necessary for recognition of spoken word and found in DOMINANT hemisphere (sensory area of speech)

Aphasia –> problem with speech

Question 25

What causes Broca’s aphasia?

Answer 25

Damage to the frontal lobe

Question 26

What occurs in Broca’s aphasia?

Answer 26

Understands speech and processes what is said and knows what to reply as most of frontal lobe is fine, but as Broca’s area is damaged they can’t form sentences

Weakness/paralysis of one side on body as Broca’s area is close to motor area

Question 27

What causes Wernicke’s aphasia?

Answer 27

Damage to the temporal lobe

Question 28

What occurs in Wernicke’s aphasia?

Answer 28

• Fluent speech, with new meaningless words and can’t understand speech not are they aware of any mistakes
• No paralysis

Question 29

What are the three types of myelinated axon fibres which are bundled into tracts?

Answer 29

• Comissural fibres
• Association fibres
• Projection fibres

Question 30

What structures do commissural fibres connect?

Answer 30

The two hemispheres via corpus callosum

Question 31

What structures do association fibres connect?

Answer 31

One part of the cortex with the other one within one hemisphere

Question 32

What structures do projection fibres connect?

Answer 32

Run between the cerebral cortex and various subcortical centres. They pass through the corona radiate and the internal capsule.

Question 33

What does the internal capsule contain?

Answer 33

It is made up of projection fibres passing to and from the cerebral cortex

All sensory and motor neurones from opposite side of body pass through it and then radiates out to the different lobes of the brain.

Question 34

What is the blood supply to the internal capsule?

Answer 34

Middle cerebral artery

Question 35

What are basal ganglia?

Answer 35

They are subcortical nuclei which are discrete collections of neural cell bodies that sit at the base of the cerebral hemisphere

Question 36

What does the basal ganglia consist of?

Answer 36

Made up of the caudate nucleus, putamen and globes pallidus

Substantial nigra in midbrain functionally part of them through not anatomically

Question 37

What dies the globus pallidus and putamen form?

Answer 37

Lentiform nucleus

Question 38

Describe the anatomical structure of the IC, basal ganglia and thalamus

Answer 38

• Caudate nucleus lies in the wall of the lateral ventricle
• The thalamus (diencephalon) lies beside the third ventricle
• Lateral to the caudate and thalamus lies the internal capsules
• Lateral to the internal capsule is the lentiform nucelus

Question 39

What is the importance of the base ganglia?

Answer 39

Important to get over inertia of movement – nuclei from it feeds it to increase impulse from or can decrease.

1. The caudate nucleus and the putamen are the ‘input regions’ receiving input from the motor cortex, premotor cortex, and from thalamus
2. They are in turn connected to the output regions – the globus pallidus and the substantia nigra
3. The globus pallidus then projects primarily to the thalamus (which intron send fibres to motor area of cortex

Question 40

What is the major function of the basal ganglia?

Answer 40

Help regulate initiation and termination of movements.
• Referred to as ‘extrapyramidal system’ because they play a role in controlling motor systems
• Pathology: parkinson’s, chorea, athetosis