Thalamus and Hypothalamus

Question 1

What structures make up the diencephalon?

Answer 1

• Thalamus
• Subthalamus - what is that?
• Hypothalamus

Question 2

Where is the thalamus found within the brain - saggital?

Answer 2

• In the middle of the brain
• Just under the posterior half of the corpus callosum

Question 3

Where is the thalamus found within the brain - coronal?

Answer 3

• Sits ventral to the lateral ventricles
• Divided into two by the 3rd ventricle
• Organised into discrete (separate) nuclei

NOTE: In neuroanatomy, nuclei are clusters of neurons (groups of cell bodies) with a similar functions and connections

Question 4

Describe the connections of the thalamus with the forebrain.

Answer 4

Each half of the thalamus has ipsilateral connections with the forebrain

Question 5

What is the main function of the thalamus?

Answer 5

• Relay site for numerous inputs and outputs within the CNS
• Relays signals to cortical areas
• Key relay centre to sensory cortical areas
  
  • Involved in almost all sensory systems
    
    • EXCEPT olfactory
• Modulates signals - enhances or restricts signals

NOTE: Main in bold

Question 6

Describe how thalamic nuclei are named.

Answer 6

They are named based on their location within the thalamus

Question 7

What is the classification of thalamic nuclei based on and what are the four different classes?

Answer 7

The classification is based on the connections of the thalamic nuclei with the cortex SPECIFIC – connected to primary cortical areas ASSOCIATION – connected to association cortex INTRALAMINAR – connected to ALL cortical areas RETICULAR – not connected to the cortex

Question 8

Which nuclei connect with the motor cortex (primary, premotorand supplementary)?

Answer 8

Ventral lateral Ventral anterior

Question 9

Which nuclei relay sensory information from different parts of the body?

Answer 9

Head – Ventral posteromedial Below the neck – Ventral posterolateral

Question 10

Which nucleus is connected to the primary visual cortex?

Answer 10

Lateral geniculate nucleus

Question 11

Which nucleus is connected to the primary auditory cortex?

Answer 11

Medial geniculate nucleus

Question 12

The association cortex can be divided into three areas based on thalamic function. What are these three areas?

Answer 12

Prefrontal Cortex Parieto-tempero-occipital Cortex Cingulate Cortex

Question 13

What do the anterior, lateral dorsal and dorsomedial nuclei connect with?

Answer 13

Prefrontal and Cingulate Cortex

Question 14

What do the lateral posterior and pulvinar nucleus connect with?

Answer 14

Prefrontal and Parieto-tempero-occipital Cortex

Question 15

What important system are the intralaminar and reticular nuclei a part of?

Answer 15

Reticular activating system – involved in maintaining consciousness

Question 16

Describe how the reticular nuclei affect cortical activity.

Answer 16

The reticular nuclei don’t have any direct connections with the cortex but they do have widespread intrathalamic connections with all other thalamic nuclei so it can influence the flow of information from the othernuclei to the cortex

Question 17

What is the core of grey matter that runs through the brainstem and is involved in the reticular activating system?

Answer 17

Reticular formation

Question 18

How do the intralaminar nuclei modulate the activity of the cortex?

Answer 18

The reticular formation projects up to the thalamus to the intralaminar nuclei and the intralaminar nuclei, because of their diffuse cortical projections, can modulate the activity of the cortex

Question 19

What is thalamic syndrome?

Answer 19

Syndrome that develops after thalamic stroke The symptoms depend on which part of the thalamus has been affected

Question 20

What three main changes occur in thalamic syndrome?

Answer 20

CHANGE IN SENSATION – reduced, exaggerated, altered PAIN – central, non-localised (not easily treated because normal analgesics have no effect – may need to use opioids or anti-convulsants/anti-depressants) EMOTIONAL DISTURBANCE – the nuclei that transmit information to and from the association cortex are associated with the limbic system

Question 21

Describe the location and structure of the hypothalamus.

Answer 21

The hypothalamus is just below the thalamus and is divided by the 3rd ventricle It also has ipsilateral connections with the forebrain

Question 22

How is the hypothalamus involved in maintaining homeostasis?

Answer 22

It coordinates these different mechanisms to maintain homeostasis:  Autonomic nervous system  Endocrine system  Behaviour

Question 23

State some forebrain structures that the hypothalamus has very close connections with

Answer 23

Olfactory system Limbic system

Question 24

List some structures of the limbic system.

Answer 24

Hippocampus Amygdala Cingulate Cortex Septal Nuclei

Question 25

What does the behavioural control exerted by the hypothalamus include?

Answer 25

Eating and drinking Expression of emotion Sexual behaviour Circadian rhythm Memory

Question 26

Which nucleus is involved in the circadian rhythm?

Answer 26

Subrachiasmatic nucleus

Question 27

How is our behaviour directed towards homeostatic goals?

Answer 27

There is a pleasure centre within the limbic system, which, whenever you’ve achieved homeostasis (e.g. eating food when you’re hungry), the activity of the pleasure centre increases

Question 28

What are the presenting symptoms of hypothalamic tumour?

Answer 28

Polydipsia Polyuria Absent menses

Question 29

What are some later symptoms of hypothalamic tumour?

Answer 29

Labile emotions, rage Inappropriate sexual behaviour Memory lapses Temperature fluctuation Thyroid, adrenal cortex and gonadal function decreases Hyperphagia