Homeostatis and Hypothalamus 3

Question 1

What was the research that Cannon and Bard were doing?

Answer 1

They researched with “decerebrated” ( to surgically disconnect the cerebrum from lower brain area) cats.

Question 2

What happened when the cortex was disconnected but the hypothalamus was intact?

Answer 2

able to sustain homeostais
able to land on feet
displayed “sham rage” (threat posture, hissing,)
Reactions were stereotyped and not at specific targets.

Question 3

What happened when the hypothalamus was partially severed?

Answer 3

Sham rage partially displayed
Usually able to sustain homeostasis

Question 4

What happened when hypothalamus was disconnected from brain stem?

Answer 4

No longer showed sham rage
difficult to keep the animal alive

Question 5

What did this research experiment conclude on?

Answer 5

demonstrated that many complex functions are regulated automatically without input from higher brain areas.

Question 6

What regulates stress hormone in the hypothalamus?

Answer 6

The paraventricular nucleus (PVN)
controls both sympathetic activation and HPA axis.

Question 7

autonomic functions of the paraventricular nucleus (PVN)

Answer 7

dorsal and ventral projections from PVN.
projects to brain stem and spinal cord
regulates sympathetic and

Question 8

endocrine functions of the paraventricular nucleus (PVN)

Answer 8

medial and lateral projections from PVN.
connects to pituitary
regulates the HPA axis.

Question 9

What is cortisol used to maintain?

Answer 9

energy use
energy stores
cardiovascular functioning
Cortisol isn’t only for stress but increases to maintain stress responses.

Question 10

How is cortisol regulated?

Answer 10

Regulated by multiple feedback systems
when cortisol levels get high, less cortisol is produced
Important regulate because too much cortisol can have negative effects.

Question 11

How does cortisol travel in negative feedback loops?

Answer 11

Cortisol can pass through blood brain barrier
PVN detects cortisol with decreases CRF–> pituitary gland detects cortisol which decreases ACTH release.

Question 12

What does the amygdala do for HPA activity?

Answer 12

Increases it.

Question 13

What does the hippocampus do for HPA activity?

Answer 13

It can both decrease and increase HPA activity. BUT plays a major in role DECREASING HPA activity.

Question 14

What happens when people have smaller hippocamupses?

Answer 14

less ability to inhibit HPA activation. They are more vulerable to developing PTSD after trauma.

Question 15

Beta-endorphins.

Answer 15

An endogenous opioid
When the HPA axis is active, CRH from hypothalamus stimulates release of ACTH from pituitary. CRH also stimulates release of beta-endorphins.

Question 16

Normal cortisol regulation

Answer 16

Cortisol is part of regular metabolism.
Circadian rhythm for cortisol productin
regulated by the sleep-wake cycle, influenced by hours of “daylight”

Question 17

How does cortisol play a permissive and productive role

Answer 17

“Permissive”- normal levels of cortisol lets things happen.
Maintain regularly scheduled progress
“Productive”- high levels of cortisol makes things happen
“shift focuses to emergency tasks”
Certain metabolic functions get prioritized over others.

Question 18

Circadian Rhythm of cortisol regulation?

Answer 18

Superchiasmatic nucleus (SCN) of hypothalamus. Receives visual info from thalamus. Day-night cycles detected form light exposure. SCN regulates daily activity of PVN. Relays info to PVN (feed- forward)

Question 19

When does cortisol peak?

Answer 19

It peaks in the morning right as when you wake up.

Question 20

When does it start decreasing?

Answer 20

Throughout the day and drops lowest when we sleep. drops cortisol helps you fall asleep.

Question 21

Negative feedback loops with cortisol at the pituitary.

Answer 21

At the pituitary the detection of cortisol reduces ACTH

Question 22

Negative feedback loops with cortisol at the hypothalamus.

Answer 22

Detection of cortisol in cerebrospinal fluid (third ventricle)
reduces activity of the medial PVN

Question 23

What does the paraventricular nucleus of hypothalamus do?

Answer 23

Gets input form SCN.
Adjusts set point for cortisol throughout the day
uses negative feedback to maintain cortisol levels

Question 24

Cortisol during stress?

Answer 24

stress decreases negative feedback loop. Increased cortisol should decrease production of CRF in the hypothalamus.

Question 25

What are the two pathways of CRF neurons in PVN of hypothalamus.

Answer 25

Parvocelluar neurons of the PVN (CRF neurons) and Magnocellular neurons on the PVN (CRF-AVP neurons)

Question 26

Parovoceullar neurons

Answer 26

smaller neurons in the paraventricular nucleus control normal levels of cortisol secretion
release CRF into pituitary –> pituitary releases ACTH
easily regulated by negative feedback loops

Question 27

Magnocellular Neurons

Answer 27

Bigger neurons in the paraventricular nucleus
release CRF and Vassopression (AVP)
connections to pituitary to release ACTH
connections to brainstem (aminergic nuclei)
triggered by sympathetic activation
not easily regulated by negative feed back loops

Question 28

What is a minor stressor?

Answer 28

A typical, short term stressor
Sympathetic activation of the HPA
SAM signals HPA
if stress is short-term, sympathetic turns off quickly
HPA regulation returns to “normal” circadian cycle
HPA return takes longer than SAM return to baseline

Question 29

What is a major stressor?

Answer 29

Extreme or extended stressor
SAM and HPA may remain simultaneously active for extended time
effects of both are intensified
increase activation of CRF feedback system throughout brain
increased activation of Magnoceulllar (CRF-AVP) neurons of the PVN
PVN less responsive to negative feedback
more ACTH is released
HPA activity becomes less responsive to negative feedback