Thalamus And Hypothalamus

Question 1

Summarise the structure of the thalamus

Answer 1

The thalamus is on either side of the 3rd ventricles and just beneath the lateral ventricles with the hypothalamus below it.

The thalamus is a collection of individual nuclei with separate function, has ipsilateral connections with the forebrain, the nuclei have separate functions but are interconnected.

Question 2

State the function and importance of the thalamus

Answer 2

Relay site for inputs and outputs, its a key relay centre for the cortisol sensory areas and involved in almost all sensory system (except olfactory)

Also has a modulating role in enhancing and restricting signals.

Somatosensory pathway: skin > peripheral sensory neuron > primary sensory neuron > secondary sensory neuron (cross over at thalamus) > through gracile nucleus > primary somatosensory cortex in parietal lobe = central gyrus sulcus.

Question 3

Describe the role of the intralaminar nuclei of the thalamus and its significance if lost

Answer 3

Project to the medial temporal lobe (1. Amygdala (emotions), 2. Hippocampus (memory), 3. Basal ganglia (movement)).

Mostly glutanergic synapses and thus excitatory.

If loss: progressive supranucelar palsy (PSP) which causes problems with walking and also Parkinson’s

Question 4

Describe the role of the reticular nuclei and its importance

Answer 4

Forms the outer covering of the thalamus, doesn’t connect with the distal regions of other thalamus nuclei (takes input and therefore only modulatory).

Set of interconnected pathways in the Brainstem - sends ascending projections to forebrain nuclei (RAAS) - involved in consciousness and arousal.

Increase in RAAS = increase in wakefulness

Thalamic stroke - emotional disturbances

Question 5

What is the structure of the hypothalamus

Answer 5

Divided into two by the 3rd ventricle, collection of individual nuclei with distinct functions (largely ipsilateral)

Has 4 functions: feeding, fighting, fleeing and mating

Question 6

What are the functions of the thalamus

Answer 6

1. Direct connections with autonomic nervous system = neurones in hypothalamic paraventricular nucleus with direct connections to pre-autonomic neurones in spinal cord.
2. Connections with endocrine systems Eg hypothalamic pituitary
3. Control of behaviour eg feeding

Question 7

Describe the role of the paraventricular nucleus

Answer 7

1. Sends projections to the Autonomic nervous system and posterior pituitary gland.
2. Involved in feeding
3. Controls circadian rhythm
4. Pleasure centre - reinforces good behaviour