6. Thalamus and Hypoothalamus

Question 1

Where is the thalamus found within the brain?

Answer 1

It is right in the middle the brain just under the posterior half of the corpus callosum

Question 2

What separates the two halves of the thalamus?

Answer 2

3rd ventricle
Some people have a bridge connecting the two halves
(Its called vestigeal structure)

Question 3

Describe the connections of the thalamus with the forebrain.

Answer 3

Each half of the thalamus has ipsilateral connections with the forebrain

Question 4

3 components of diencephalon

Answer 4

Thalamus, subthalamus and hypothalamus

Question 5

What is the main function of the thalamus?

Answer 5

[[[It is a relay centre between the cerebral cortex and the rest of the CNS, to cortical sensory areas]]]
Enhances and restricts signals
Connection is reciprocal
Integration and modification of information as it goes through thalamus
nucleus for every functional system in NS but not for olfaction

Question 6

What is the only function that is not represented within the thalamus?

Answer 6

olfaction

Question 7

Describe how thalamic nuclei are named.

Answer 7

They are named based on their location within the thalamus

Question 8

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

Answer 8

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 9

Describe somatosensory pathway

Answer 9

Vibration/propioception/light touch TO dorsal root ganglion TO posterior dorsal columns TO primary sensory neuron TO gracile nucleus seen in medulla and sensory decussation (cuneate nucleus maybe) TO thalamus VPLN via secondary sensory neurone TO primary somatosensory cortex via tertiary neuron.

Question 10

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

Answer 10

Ventral lateral

Ventral anterior

Question 11

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

Answer 11

Head – Ventral posteromedial

Below the neck – Ventral posterolateral

Question 12

Which nucleus is connected to the primary visual cortex?

Answer 12

Lateral geniculate nucleus

Question 13

Which nucleus is connected to the primary auditory cortex?

Answer 13

Medial geniculate nucleus

Question 14

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

Answer 14

Prefrontal Cortex
Parieto-tempero-occipital Cortex
Cingulate Cortex

Question 15

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

Answer 15

Prefrontal and Cingulate Cortex

Question 16

What do the lateral posterior and pulvinar nucleus connect with?

Answer 16

Prefrontal and Parieto-tempero-occipital Cortex

Question 17

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

Answer 17

Reticular activating system – involved in maintaining consciousness

Question 18

Describe intralaminar nuclei

Answer 18

Project to various medial temporal lobe structures (e.g. amygdala-emotion, hippocampus-memory and basal ganglia-movement)
Mostly glutamergic (excitatory)
Loss of neurons in this region associated with supranuclear palsy(problem walking and balance) and Parkinsons

Question 19

Describe how the reticular nuclei affect cortical activity.

Answer 19

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 other nuclei to the cortex

Question 20

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

Answer 20

Reticular formation

Question 21

What forms outer covering of thalamus?

Answer 21

Reticular nucleus

Question 22

What is the reticular formation?

Answer 22

Set of interconnected pathways in the brain stem, ascending projections to forebrain nuclei- aRAS
consciousness and arousal
Intralaminar and reticular nucleus receives input from aRAS

Question 23

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

Answer 23

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 24

What is thalamic syndrome?

NOT IN PP

Answer 24

Syndrome that develops after thalamic stroke

The symptoms depend on which part of the thalamus has been affected

Question 25

What three main changes occur in thalamic syndrome? NOT IN PP

Answer 25

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 26

Describe the location and structure of the hypothalamus and its involvement in homeostasis

Answer 26

The hypothalamus is just below the thalamus and is divided by the 3rd ventricle It also has ipsilateral connections with the forebrain It coordinates these different mechanisms to maintain homeostasis: • Autonomic nervous system • Endocrine system • Behaviour

Question 27

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

Answer 27

Olfactory system | Limbic system

Question 28

List some structures of the limbic system.

Answer 28

Hippocampus Amygdala Cingulate Cortex Septal Nuclei

Question 29

What does the behavioural control exerted by the hypothalamus include?

Answer 29

4Fs fight, flee, feeding, mating ``` Eating and drinking Expression of emotion Sexual behaviour Circadian rhythm Memory ```

Question 30

Which nucleus is involved in the circadian rhythm?

Answer 30

SuPrachiasmatic nucleus

Question 31

Discuss the paraventricular nucleus

Answer 31

Shape of a balloon just when you start blowing it, furthest away from optic chiasm Sends projections to ANS and neurohypophysosis(magnocellular and parvocellular nuclei for oxytocin and ADH) and feeding behaviour

Question 32

What are effects of lesions of SuPrachiasmatic nucleus

Answer 32

disturbance of sleep pattern

Question 33

Hypothalamic tumour EARLY and LATE symptoms

Answer 33

EARLY Polydipsia, polyuria, absent menses LATE labile motions, rage, inappropriate sexual behaviour, memory lapses, temp fluctuation, thyroid, adrenal cortex and gonadal function decrease, hyperphagia

Question 34

How is our behaviour directed towards homeostatic goals?

Answer 34

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