Thalamus and Hypothalamus (Neuro)

Question 1

What can the diencephalon be divided into?

Answer 1

Thalamus
Subthalamus
Hypothalamus

Question 2

Draw diagrams and structures of the thalamus and hypothalamus

Answer 2

See diagrams

Question 3

Describe the orientation of the thalamus in the brain?

Answer 3

Sits ventral (underneath) to the lateral ventricles and is divided by the 3rd ventricle. Organised into nuclei

Question 4

What is the function of the thalamus?

Answer 4

Relay site for numerous inputs/outputs - Key relay centre to cortical sensory areas. So it is regulating how much sensory information is sent to the somatosensory cortex.
Involved in almost all sensory systems (except olfactory)
Enhances or restricts signals - prevents sensory overload

Question 5

Draw the somatosensory pathway

Answer 5

See diagram and lecture

Dorsal column pathway –> Ventral Posterior Lateral Nucleus

Question 6

What is the intralaminar nuclei?

Answer 6

These nuclei project to various medial temporal lobe structures (amygdala, hippocampus and basal ganglia)
See notes/slides

Mostly glutamatergic neurons (i.e. excitatory)

Question 7

What are the amygdala, hippocampus and basal ganglia involved in?

Answer 7

Amygdala = emotions, fear, anxiety
Hippocampus = memory
Basal ganglia = movement

Question 8

What is the loss of intralaminar nuclei associated with?

Answer 8

Progressive supranuclear palsy and Parkinson’s disease

PSP is a rare brain disorder that causes problems with walking and balance.

Question 9

Glutamatergic neurones vs GABAergic neurones

Answer 9

Glutamatergic = excitatory
GABAergic = inhibitory

Question 10

What is the reticular nucleus

Answer 10

Forms the outer covering of the thalamus and connects thalamic nuclei. Modulate thalamic activity - Influences flow of information through the other nuclei to the cortex
mainly GABAergic – inhibitory
Unlike other nuclei, no distal connections just intrathalamic connections.

Question 11

What is the reticular formation?

Answer 11

A set of interconnected pathways in the brainstem. It sends ascending projections to forebrain nuclei. The ascending projections is the Ascending reticular activating system ARAS

Question 12

What is the ARAS?

Answer 12

It is crucial for consciousness and arousal - increased activity in the ARAS = increased wakefulness
The ARAS are inputs to both the reticular nucleus and intralaminar nucleus. RAS emanates from the brainstem and projects upwards towards the cerebral cortex via the thalamus.

Question 13

What does damage to the ARAS cause?

Answer 13

Coma or even death - Remember the ARAS is part of the reticular formation

Vegetative state is different from coma. Vegetative state would more likely be damage to the cerebral cortex

Question 14

Describe the orientation of the hypothalamus

Answer 14

See diagram - divided into two by the 3rd ventricle and is a collection of individual nuclei with distinct functions
Largely ipsilateral (same side) connections with other nuclei

Question 15

What are the functions of the hypothalamus?

Answer 15

4Fs - Fighting, Fleeing, Feeding and Fucking

Direct connections with autonomic nervous system - the Paraventricular nucleus projects directly to the pre-autonomic neurones in the spinal cord.
Parvocellular neurones - (very long connections into the spinal cords into the Intermedial Lateral column (contain sympathetic pre-ganglionic neurones))

Paraventricular nucleus also projects to the posterior pituitary. (Magnocellular) Connections with the endocrine system - hypothalamic-pituitary axis (see notes for which nuclei and how it works) magnocellular neurones (go to the posterior pituitary)

PVN involved in the control of feeding behaviour

Question 16

What is the suprachiasmatic nucleus?

Answer 16

See diagram/notes. Internal body clock. The activity of the SCN goes through a cycle where it increases during the day and decreases at night. It is controlled through retinal ganglion cells that connect to the SCN via the retino-hypothalamic tract. It is sensitive to blue light. The SCN in turn connects to the PVN which connects to the spinal cord which connects to the Pineal gland that secretes melatonin. Melatonin = sleep tired hormone