Thalamus and hypothalamus

Question 1

Describe the organisation of the thalamus?

Answer 1

Sits ventral to the lateral ventricles
Thalamus divided in two by 3rd ventricle
Organised into discrete nuclei

Question 2

What is a nucleus in neuroanatomy terms?

Answer 2

Neurons with similar functions and connections

Question 3

What is the function of the thalamus?

Answer 3

Key relay centre to cortical sensory areas
Involved in almost all sensory systems (except olfactory)
Enhances or restricts signals

Question 4

What is the intralaminar nucleus?

Answer 4

Project to various medial temporal lobe structures (e.g. amygdala, hippocampus and basal ganglia)
Amygdala = emotions, fear, anxiety
Hippocampus = memory
Basal ganglia = movement
Mostly glutamatergic neurons (i.e. excitatory)
Loss of neurons in this region associated with progressive supranuclear palsy and Parkinson’s disease

Question 5

What is the reticular nucleus?

Answer 5

Forms the outer covering of the thalamus
Majority of neurons are GABAergic (e.g. inhibitory)
Unlike other thalamic nuclei, they don’t connect with distal regions, but with other thalamic nuclei
Receive inputs from collaterals of their axons from thalamic nuclei
Therefore, reticular nucleus acts to modulate thalamic activity (negative feedback)

Question 6

What is the reticular formation?

Answer 6

Set of interconnected pathways in the brainstem
Send ascending projections to forebrain nuclei
Ascending reticular activating system (ARAS)
Involved in consciousness and arousal
Degrees of wakefulness depend on ARAS activity (increased activity = increased wakefulness)
Both intralaminar and reticular nucleus receive inputs from ARAS

Question 7

Describe organisation of the hypothalamus?

Answer 7

Divided into two by 3rd ventricle
Collection of individual nuclei with distinct functions
Largely ipsilateral connections with other nuclei

Question 8

What is the function of the hypothalamus?

Answer 8

Involved in 4 F’s

Question 9

What two things does the hypothalamus have a connection with?

Answer 9

Direct connections to pre-ganglionic neurones in the spinal cord.
Connections with endocrine system e.g. pituitary.

Question 10

What is one thing the paraventricular nucleus is involved in?

Answer 10

Involved in feeding…stimulation of paraventricular neurones results in feeding. Lesions result in hyperphagia and weight gain.

Question 11

What is the suprachiasmatic nucleus involved in?

Answer 11

Involved in coordination of the sleep wake cycle. Lesions cause disrupted sleeping pattern.