Hypothalamus

Question 1

Where is the hypothalamus position and what does this allow for ?

Answer 1

Middle of the brain surrounding the third ventricle straddling the midline which allows for its vast connectivity so in and out is easy in terms of brain central flow

Very small percentage of neurones

Question 2

What are the functions of the hypothalamus

Answer 2

Homeostasis and survival - makes set points for physiology a parameters which are important - blood pressure and glucose these set points live in the hypothalamus
Psychological aspects which determine behaviour - determines all of what human beings do
Motivated behaviour - observable can’t observe blood pressure control but you can observe sleep - hypothalamus involved in that control

Question 3

3 main things hypothalamus has control of

Answer 3

ANS
Endocrine
Behaviour

Question 4

What ANS functions does it control ?

Answer 4

para and sympathetic outflow which allows changes in things that allow us to maintain homeostasis -> blood pressure -> vasodilation and vasoconstriction

Question 5

What endocrine systems does it control

Answer 5

Anterior pituitary hormones which are released - regulate the body homeostasis - ADH, GH, TSH, FSH, LH

Question 6

How does it control behavioural changes ?

Answer 6

What the organism is doing, info processing and influences motivated behaviour and homeostasis

Question 7

What inputs can the hypothalamus have

Answer 7

Sensory inputs fromjomeststic receptors in the:
Hypothalamus/circumventricular organs
Viscera via brain stem

External
Limbic regions - emotion 
Olfactory regions - smell
Retina - vision and circadian rhythms - supraoptic chiasm in the hypothalamus and detects the changes in light which influence thalamus hence the sleep/wake cycle
Hippocampus - learning and memory

Question 8

Once the hypothalamus has computed this information the integration determines the outputs which are:

Answer 8

Pituitary –> hormones
Brain stem –> ANS and coordination of behaviours
Limbic –> emotion –> coordination of behaviour

Leads to homeostasis and survival

Question 9

What is the emotional influence on the coordination of behaviour

Answer 9

Can influence how bothered you are to change your behaviour, such as inc in temperature how bothered are you to get up and open the window
Your motivation -> emotion can determine whether the behaviour is carried out

Question 10

How is the 3D structure of the hypothalamus described

Answer 10

Anterior posterior axis:
Anterior border - preoptic area close to the optic chiasm which contains the suprachiasmatic nucleus - circadian rhythms
Also the nuclei that is concerned with the set points are are at the very front of the hypothalamus.
Posterior border
Mammillary bodies one in each hemisphere
Difficult to know what they do normally - korsakoff’s alcoholic destruction work back fro their destruction to know their function - cases memory has been drastically effected.

Medial lateral axis
3 zones
1) periventricular zone
- suprachiasmatic nucleus at the top against the 3rd ventricle
- arcuate nucleus - form the cap of the 3rd ventricle
- anterior pituitary regulation- anatomical controversy - function regulation ant pit
2) medial zone
- paraventricular nuclei
Release hormones (post pit) oxytocin
Feeding
Autonomic function
3) lateral zone
- lateral hypothalamic area - feeding
- supraoptic nuclei - release hormones vasopressin/ADH

Question 11

ANS control inputs

Answer 11

Exteroreceptors - outside cold water - ANS active before core body temp drops
Interoreceptors - BP, glucose
Many areas -> massive integrations
Results of computation

Question 12

ANS control - outputs

Answer 12

Paraventricular nucleus key sites of origins of outflow from the hypothalamus
Brain stem nuclei
Origins of preganglionic SNS/PNS
Control PNS and SNS in this way - influence autonomic - control

Evidence- stimulation/lesions of hypothalamus
Electrically stimulate hypothalamus
See changes in BP, respiratory function, vasculature, gut, HR not just reflex based

Question 13

Anterior pituitary is connected directly or indirectly and what cells function this way
And why is to direct/indirect - what makes it this way

Answer 13

Indirectly
Parvocellular neurosecretory cells in the hypothalamus which connect to the anterior pituitary where they release neurotransmitters into the blood capillary bed - neuroendocrine
These hormones are the hypophysiotrophic hormones - releasing hormones - gonadotropin releasing hormone
They then act on the anterior pituitary before the effect of their release acts on the body - such as gonadotropin releasing hormone - release FSH and LH which then act on the reproductive system

Question 14

Posterior pituitary is it connected directly or indirectly to the hypothalamus, what re the cells called which mediate its effect and why is it classed as a direct action

Answer 14

It is a direct connection between the two
The cells are called the magnocellular they release their neurotransmitters into the posterior pitiably capillary bed. What are released - ADH and oxytocin these can then go on to act directly on the body
No intermediate action before the production of any other hormones

Question 15

Behavioural control what is it motivated by

Answer 15

It is motivated by rewards
Complex and varied
In order to perform a task there must be something in it for you as it requires expenditure of energy so requires payback which is the concept of reward
When reward goes wrong - talking drugs

Question 16

Integration of ANS, endocrine, and behavioural function example - food intake
Short term regulation

Answer 16

Hypothalamic input
Mechanoreceptors in the gut
Glucose receptors - hepatic

Hypothalamic receptors
Glucose
Gherkin

Question 17

Integration of ANS, endocrine, and behavioural function example - food intake
Long term regulation

Answer 17

Fat stores produce leptin which acts on the hypothalamus
Causing Decrease in food intake - feeding behaviour which is the behavioural control
ANS is affected which increases the metabolic rate and so the the pituitary hormones which Is endocrine which work to maintain normal body weight.

Question 18

Which nuclei are involved in food intake and the maintenance of body weight

Answer 18

Arcuate nucleus - main detector has a high density of leptin receptors therefore can detect adipose tissue.
Depending on what is sensed high or low leptin the arcuate nucleus then sends projections to the other hypothalamic areas
1) paraventricular nucleus - suppresses eating
This controls the ANS and signal to the pituitary - influence the ant pit
Lesions of this can result in uncontrolled feeding and obesity
2) lateral hypothalamic areas - drive eating
Lesions here can cause starvation, multiple sclerosis lesions here the person doesn’t eat
It’s projections are widespread
- cortex : motivation to search for food

Question 19

Temperature control: can it be changed

Answer 19

Can be changed in fever by the immune system. Adjust the set point to be higher so when already hot cause shivering inc temp further

Question 20

What are the 2 nuclei called which control temperature and what do the do?

Answer 20

Anterior hypothalamic nuclei
- heat dissipation
Posterior hypothalamic nuclei
- heat retention

Question 21

What does the integrated response consists of ?

Answer 21

Autonomic - vasomotor changes in the skin
Endocrine - inc and dec metabolism acclimatise to some degree
Behavioural - shivering, panting, seek warmth/shade

Question 22

What are the anatomical differences in the brain of males and females
What is the integration ?

Answer 22

Called sexual dimorphism
Most difference in the preoptic area don’t know why
ANS - sexual organs
Endocrine - puberty and reproductive cycling
Behavioural - courtship

Question 23

Clinical considerations for the hypothalamus

Answer 23

Brain injury rare due to its position deep in the middle of the brain.
And it is bilateral so damage to one the other can take over
Tumors hard to spot symptoms due to the large amount of areas the hypothalamus controls
And it’s location cannot be operated on