Thalamus and Hypothalamus

Question 1

What is the diencephalon made up of?

Answer 1

Thalamus and Hypothalamus (and subthalamus)

Question 2

Where is the Thalamus located?

Answer 2

• towards the back of the brain
• near the midline
• just beneath lateral ventricles
• divided in the middle by 3rd ventricle
• above hypothalamus
• associated with midbrain

Question 3

Which part of the thalamus deals with touch/proprioception?

Answer 3

ventral posterior lateral nucleus

Question 4

What are the functions of the Thalamus?

Answer 4

• Relay centre of the brain
• involved in almost all sensory systems (except olfactory)
• enhances or restricts signals

Question 5

What are the functions of the hypothalamus?

Answer 5

• Collection of individual nuclei with distinct functions
• largely ipsilateral connections with other nuclei
• involved in 4Fs (fighting, fleeing, feeding, mating)
• direct connections with the ANS
• connections with the endocrine system (hypothalamic pituitary axis)
• control of behaviour (e.g. feeding behaviour)

Question 6

In neuroanatomy, what are nuclei?

Answer 6

Clusters of neurons with a similar functions and connections.

Question 7

Where does the thalamus lie in relation to the ventricles?

Answer 7

• Sits ventral to the lateral ventricles

- Thalamus divided in two by 3rd ventricle

Question 8

Intralaminar nuclei

Answer 8

• Project to various medial temporal lobe structures (e.g. amygdala, hippocampus and basal ganglia)
• mostly glutamatergic neurones (excitatory)
• Loss of neurones in this region associated with progressive supranuclear palsy* and Parkinson’s disease

Question 9

What is the amygdala responsible for?

Answer 9

fear, anxiety, emotions

Question 10

What is the hippocampus responsible for?

Answer 10

Memories

Question 11

What are the basal ganglia responsible for?

Answer 11

Movement

Question 12

Progressive supranuclear palsy

Answer 12

PSP

-> rare brain disorder causing problems with walking and balance

Question 13

Reticular Nucleus

Answer 13

• forms outer covering of the thalamus
• majority of neurones are GABAergic (inhibitory)
• don’t connect with distal regions, but with other thalamic nuclei (unlike other thalamic nuclei)
• Receive inputs from collaterals of their axons from thalamic nuclei
• acts to modulate thalamic activity (negative feedback)

Question 14

Reticular formation

Answer 14

• Set of interconnected peathways in the brainstem,
  
  • send ascending projections to forebrain nuclei (ARAS)
• involved in consciousness and arousal
• Both intralaminar and reticular nucleus receive inputs from ARAS

Question 15

What is the ARAS responsible for?

Answer 15

ascending reticular activating system
-> concousness and arousal

degree of wakefulness depends on the level of ARAS activity

Question 16

Hypothalamus and ANS

Answer 16

Neurons in hypothalamic paraventricular nucleus with direct projections to pre-autonomic neurons in spinal cord

-> hypothalamus has direct connections with the ANS

Question 17

Paraventricular nucleus in the hypothalamus function

Answer 17

• Sends projections to autonomic nervous system and posterior pituitary gland
• also involved in feeding behavior

Question 18

What is the function of the suprachiasmatic nucleus?

Answer 18

• responsible for controlling the circadian rhythm
• tiny region of the brain in the hypothalamus, located right above the options chasm
• lesions of SCN cause sleep disruptions

Question 19

Name the association nuclei of the thalamus

Answer 19

• lateral dorsal nucleus
• dorsomedial nucleus
• posterior lateral nucleus and the pulvinar (belong to a single nuclear complex)

Question 20

Which sensory system is the thalamus not involved in?

Answer 20

Olfactory

Question 21

What part of the thalamus is important in the somatosensory pathway?

Answer 21

ventral posterior lateral nucleus

Question 22

What is the function of the intralaminar nuclei?

Answer 22

Project to various medial temporal lobe structures (e.g. amygdala, hippocampus and basal ganglia + reticular formation)

Can be regarded as a rostral continuation of the reticular formation of the midbrain. Project widely into the cerebral cortex.

Play a role in the function and regulation of the basal ganglia, arousal, cognitive functions, and relaying of nociceptive information to the cerebral cortex.

• Amygdala = emotions, fear, anxiety
• Hippocampus = memory
• Basal ganglia = movement
• reticular formation: arousal

Mostly glutamatergic neurons (i.e. excitatory)
Loss of neurons in this region associated with progressive supranuclear palsy* and Parkinson’s disease

Question 23

PSP

Answer 23

progressive supra nuclear palsy

-> rare brain disorder causing problems with walking and balance.

Question 24

Summarise the relationship between intralaminar nuclei, reticular nucleus and the reticular formation

Answer 24

• The Intralaminar nuclei receive inputs from the Reticular Formation of the brainstem and project diffusely to all cortical areas.
• The reticular nucleus also receives inputs from the reticular formation but projects to the other thalamic nuclei only, regulating the flow of information through these to the cortex.
• Thus the reticular formation, intralaminar and reticular nuclei form the Reticular Activating System, which controls the level of arousal of the brain by modulating the level of activity of the cerebral cortex.

Question 25

Where is the hypothalamus?

Answer 25

• below the thalamus
• divided into 2 by the 3rd ventricle
• collection of individual nuclei with distinct functions
• largely ipsilateral connections with other nuclei
• involved in the 4 Fs (fighting, fleeing, feeding and mating)

Question 26

Hypothalamus and the endocrine system

Answer 26

Connections with endocrine systems

E.g. hypothalamic-pituitary axis

Question 27

Hypothalamus and control of behaviour

Answer 27

• e.g. feeding behaviour (Paraventricular nucleus)

Question 28

Where are the different components of RAS located?

Answer 28

• reticular formation is in the brainstem

- intralaminar and intralaminar nuclei are in the thalamus