Neuro 6: Thalamus and hypothalamus

Question 1

List the 3 parts of the diencephalon

Answer 1

Thalamus, hypothalamus and subthalamus

Question 2

What intersects the thalamus

Answer 2

3rd ventricle

Question 3

Locate the thalamus

Answer 3

Ventral to the lateral ventricle

Question 4

Which 2 thalamic neurons associated with the resticular activating system

Answer 4

RETICULAR nucleus (all around the outside of the thalamus)… does not project to cortex, provides negative feedback to the thalamus

and

INTRALAMINAR… projects to all other areas of cortex including medial temporal lobe structures (amygdala, hippocampus and basal ganglia)

Question 5

State the function of the thalamus

Answer 5

Key relay centre to cortical sensory areas

Involved in almost all sensory systems (not olfactory)

Enhance or restricts signals

Question 6

Which sense does not travel through the thalamus

Answer 6

Olfactory

Question 7

The thalamus only enhances signals t/f

Answer 7

F it can restrict too

Question 8

Which thalamic nucleus is responsible for transmitting fine touch

Answer 8

Ventral posterior lateral nucleus

Question 9

What are intalaminar nuclei

Give the functions of the areas it projects to

Answer 9

Thalamic nucleus: Project to MEDIAL temporal lobe structures like amygdala, hippocampus and basal ganglia

Amygdala= fear, emotions, anxiety

Hippocampus= memory and learning

Basal ganglia= movement

Question 10

What type of neurons exist in the intralaminar neuclei

Answer 10

Glutamaterigic

Loss of intralaminar nucleus neurons asociated with parkinsons and supranuclear palsy (=rare brain disorder causing problems with walking and balance)

Question 11

What nucleus forms the outer covering of the thalamus +

what type of neurons here

Answer 11

Reticular nucleus (thalamic)- doesn’t connect with distal regions, but instead all other thalamic nuclei

GABAergic (compared to glutamatergic in intralaminar)

Question 12

Function of reticular nucleus

Answer 12

Mostly inhibitory on thalamic nuclei

Question 13

Where do reticular nuclei receive inputs from

Answer 13

receives sensory information from thalamic neurons via COLLATERALS of their axons

Modulates thalamic activity -ve feedback depending on this input

Question 14

Where is the reticular formation found and what is it involved in

Answer 14

Area of grey matter in brainstem, set of interconnected pathways

Send ascending projections to forebrain nuclei via ascending reticular activating system (ARAS)

Conscioussness and arousal. Degree of wakefullness dependent on ARAS (increased activity of ARAS –> increased wakefullness)

Intralaminar and reticular nuclei receive input from ARAS

Question 15

What is ascending reticular activating system

Answer 15

Consciousness and arousal- degrees of wakefullness proportional to activity of ARAS Intralaminar and reticular nucleus receive input from the ARAS

Question 16

How can the RAS increase activity in the cortex

Answer 16

DIRECT: can increase stimulation of intralaminar nuclei, so this directly increases activity of cortical areas

INDIRECT: can cause the reticular nucleus to increase activity of thalamic nuclei (by depressing the reticular nuclei), which would then lead to increase in cortical activity too

the greater the level of activity coming through the reticular formation into the thalamus, the more activated and stimulated the cortex becomes

Question 17

Hypothalamus has 4 functions

Answer 17

Feeding, mating, fleeing and fighting

• Connections with autonomic NS (PVN neurons project to pre-autonomic neurons in spinal cord)
• Endocrine connections
• Behaviour control (feeding behaviour)

Question 18

How does hypothalamus perform the four functions

Answer 18

Hypothalamic nuclei such as PARAVENTRICULAR NUCLEI:

Send projections to ANS and to posterior pituitary gland

Can impact on CVS function and renal function within ANS

https://en.wikipedia.org/wiki/Paraventricular_nucleus_of_hypothalamus#Neurons

Magnocellular release oxytocin and vasopressin

Parvocellular travel dwon to the spinal cord and also release hormones into the hypophysial system to influence ant. pituitary function

Question 19

State other function of hypothalamus,

Answer 19

Role in feeding as it has many receptors for hormones produced in the gut…. also to do with PARAVENTRICULAR NUCLEUS

Question 20

State the 3 types of paraventricular

Answer 20

Parvocellular neurosecretory neurons

magnocellular neuronsecretory neurons

centrally projecting neurons (another type of parvocellular)

Question 21

Where do the centrally projecting parvocellular neurons travel

Answer 21

Travel down the spinal cord and synapse onto preganglionic sympathetic nerves–> changing heart rate, constriction, renal etc

Question 22

Function of magnocellular neurons

Answer 22

Extend to post. pit to stimulate vasopressin or oxytocin release which then impact on water reabsorption (ADH) and uterine contraction (uterine)

Question 23

Effect of activating and inhibiting PVN on food,

Answer 23

Activating leads to fullness and inhibition leads to feeding

Question 24

What is the suprachiasmatic

Answer 24

Involved in sleep/wake cycles, reponsive to light.

Light sensitive retinal ganglion cells are connected to hypothalamic suprachiasmatic nuclei, particularly blue light (which activate the suprachiasmatic nuclei)

Question 25

How does suprachiasmatic nucleus influence sleep and wake cycles

Answer 25

SC nuclei neurons synapse with paraventricular nuclei which travel down to the spinal cord, impact on the intermediolateral column then up the cervical spinal cord, synapse on the superior cervical ganglion and then travel to the pineal gland which regulates melatonin release

Question 26

What would lesions of the SCN cause

Answer 26

Sleep disturbances, which is a symptom of schizophrenia

Question 27

What do the following control: Amygdala Basal Ganglia Hippocampus

Answer 27

A: fear, emotion, anxiety BG: movement HC: memory

Question 28

Loss of neurons from the intralaminar nuclei are associated with what problems

Answer 28

Parkinson's and progressive supranuclear palsy (PSP) | THINK- it goes to BG so going to affect movement e.g. like in parkinsons

Question 29

T/F hypothalamus usually has contralateral connections with other nuclei

Answer 29

F: mostly ipsilateral

Question 30

``` Outline the area of cortex associated with each of the following specific thalamic nuclei: Ventral lateral Ventral anterior Ventroposterolateral Ventroposteromedial Laterial geniculate Medial geniculate ```

Answer 30

Ventral lateral and ventral anterior - motor cortices (primary, premotor and supplemetnary) Ventroposterolateral- somatosensory (body) (you know it's lateral cos the body goes more lateral than the head!) Ventroposteromedial- somatosensory (head)… so receives fibers from the solitary tract and trigeminal nerve to the post central gyrus Laterial geniculate- visual (thin L for Light) Medial geniculate- auditory (think M for Music)

Question 31

State the different types of thalamic nuclei

Answer 31

Speicifc- going to primary cortical areas Association- connected to association cortex Reticular- not connected to cortex, connected to other thalamic nuclei Intralaminar- connected to all cortical areas

Question 32

Outline the type of association cortex linked to the following thalamic nuclei: Anterior, lateral dorsal and dorsomedial Lateral posterior and pulvinar

Answer 32

Anterior, lateral dorsal and dorsomedial: Mamillary bodies (ant), hypothalamus (lat dorsal) and cingulate and prefrontal Lateral posterior and pulvinar: parieto-temporo-occipital and prefrontal

Question 33

Examples of hypothalamic structural damage

Answer 33

Craniopharyngioma, other tumours (glioma, meningioma etc), sarcoidosis and langerhans cell histiocytosis

Question 34

T/f hypothalamus has largely ipsilateral connections with other nuclei

Answer 34

T

Question 35

Which area of the cortex is the hypothalamus associated with

Answer 35

Olfactor system and limbic system

Question 36

How does hypothalamus control behaviour

Answer 36

We already said it contros 4 Fs using paraventricular nucleus etc. ``` Behavioural control includes; Eating and drinking Expression of emotion Sexual behaviour Circadian rhythm Memory ``` Hypothalamus and limbic system have a motivational process.. there is a pleasure centre in the limbic system... i.e. eating when you are hungry achieves pleasure... reinforces benefical behaviour. Goes wrong in addiction

Question 37

Hypothalamic tumour presenting symptoms

Answer 37

Polydipsia, plyuria, absent menses

Question 38

Other thing sthan hypothalamic tumour can lead to

Answer 38

Laile emotions, inapproproaute sexual behaviour, memory lapse, temp fluctaution, thryoid/adrenal/gonadal dysfunction, hyperphagia

Question 39

Where do association nuclei of the thalamus (i.e. those which relate to association cortex) get their major input from

Answer 39

From the cortex. E.g. pulvinar, the largest association nucleus, receives information from the superior colliculus and also the association cortex. is receives afferent projections from the superior colliculus as well as from the association cortex. It projects to secondary visual areas and to association areas in the parietotemporal region. This contributes to visual perception and eye movements