10. Hypothalamus

Question 1

homeostasis:

define

Answer 1

• integrated physiological processes to maintain the internal environment of the body w/in narrow physiological range in response to changing environment
• based on theory of milieu interieur (constant internal environment)

Question 2

key fxn of hypothalamus?

Answer 2

to maintain homeostasis, which means “similar position”

Question 3

what allows the hypothalamus to maintain homeostasis?

Answer 3

broad circuitry of inputs/outputs of hypothalamus

• inputs: peripheral sensory information, cortex, limbic areas
• outputs: ANS and Pituitary

Question 4

hypothalamus: general functions

Answer 4

Control:

• BP & electrolyte come
• body temp
• energy metabolism
• reproduction
• emergency responses to stress

Question 5

what is found at the anterior-most aspect of the hypothalamus?

Answer 5

anterior commissure, lamina terminalis, and optic chiasm

Question 6

what is found at the posterior-most aspect of the hypothalamus?

Answer 6

mamillary bodies

Question 7

divisions of hypothalamus, from medial –> lateral

Answer 7

• medially: periventricular zone, and the arcuate nucleus
• then, ventromedial and dorsomedial nuclei
• the lateral zone incl. the supraoptic nucleus

Question 8

hypothalamic nuclei to know, from ANTERIOR –> POSTERIOR

Answer 8

1. preoptic
2. suprachiasmatic
3. paraventricular
4. supraoptic
5. arcuate
6. mamillary

PRom Can Pause Our Adolescent Minds

Question 9

important tracts and other structures to know for hypothalamus

Answer 9

1. column of fornix (tract)
2. anterior pituitary
3. posterior pituitary

Question 10

brief location of hypothalamus in relation to other structures

Answer 10

optic chiasm –> anterior portion

optic tract –> intermediate portion

mamillary bodies –> posterior portion

Question 11

anterior division of hypothalamus:

nuclei and functions

Answer 11

In general: controls behaviors more aligned w/ rest/digest type fxns

• preoptic –> heat loss
• supraoptic & paraventricular –> water balance, milk ejection, uterine contraction
• suprachiasmatic –> circadian rhythm

Other fxns: thirst, sleep, parasympathomimetic

Question 12

intermediate division of hypothalamus:

nuclei and functions

Answer 12

• tuberal and arcuate nuclei –> endocrine activity

Other fxns: satiety, feeding, emotions

Question 13

posterior division of hypothalamus:

nuclei and functions

Answer 13

• mammilary nuclei –> consolidation of memory (pt of Papez circuit)

Other fxns: heat conservation, arousal, aggressive behavior, analgesia, sympathomimetic

Question 14

match key function w/ corresponding hypothalamic nuclei:

heat loss

Answer 14

preoptic nuclei

(anterior division)

Question 15

match key function w/ corresponding hypothalamic nuclei:

water balance, milk ejection, uterine contraction

Answer 15

supraoptic & paraventricular

(anterior division)

Question 16

match key function w/ corresponding hypothalamic nuclei:

circadian rhythm

Answer 16

suprachiasmatic nuclei

(anterior division)

Question 17

match key function w/ corresponding hypothalamic nuclei:

endocrine activity

Answer 17

arcuate and tuberal nuclei

(intermediate division)

Question 18

match key function w/ corresponding hypothalamic nuclei:

consolidation of memory

Answer 18

mammillary nuclei

(posterior division) – part of broader circuitry in the Papez circuit

Question 19

rhythms such as diurnal rhythms (sleep/wake cycle) and hormonal rhythms are controlled by which nucleli?

Answer 19

suprachiasmatic nucleus in anterior hypothalamus;

1. receives visual inputs from the retina –> allows body to synchronize intrinsic pacemaker to the day/night cycle based on light
2. *Synchronizing with wake/sleep cycle is the key function of circadian system

Question 20

where do axons of the optic nerve terminate w/in the brain?

Answer 20

4 nuclei

• lateral geniculate nuclei (LGN) of thalamus
• superior colliculus of midbrain
• pretectum of midbrain
• suprachiasmatic nucleus of hypothalamus

Question 21

functions of the 4 nuclei where the optic nerve terminates?

Answer 21

• LGN –> visual perception
• superior colliculus –> control of eye movements
• pretectum –> control of pupillary light reflex
• suprachiasmatic nucleus –> control of diurnal rhythms and hormonal changes

Question 22

entrainment:

definition

Answer 22

occurs when rhythmic physiological or behavioral events match their period to that of an environmental oscillation

(caused by suprachiasmatic nucleus)

Question 23

association of light and rhythms

Answer 23

1. light –> synchronizes pacemaker-like activity in Suprachiasmatic Nucleus (SCN) –>
2. outputs of SCN –> neural, hormonal, and behavioral outputs

Question 24

leptin:

define

Answer 24

protein produced by fat cells;

if increase in # of fat cells –> more leptin

Question 25

relationship of leptin & feeding

Answer 25

(inc. in fat cells) --\> **increase** in leptin --\> **decrease** in feeding (**inversely** related)

Question 26

what happens if mouse LACKS leptin gene

Answer 26

--\> increase in feeding --\> mouse becomes obese

Question 27

fxn of **arcuate nucleus**

Answer 27

integrates multiple **satiety and hunger signals**

Question 28

2 major **arcuate projections** and respective effects

Answer 28

* **paraventricular nucleus (PVN):** effects on cellular metabolism via regulation of endocrine system and ANS * (TSH and ACTH) * **lateral hypothalamic area (LHA):** effects on feeding behaviors

Question 29

thermoregulation pathway: ## Footnote **inputs to hypothalamus**

Answer 29

* **thermoreceptors in skin** * blood temp monitored by **central thermoreceptors of hypothalamus** Either can detect inc or dec in body temperature

Question 30

heat **loss** response (if body temp is inc) triggered by hypothalamus

Answer 30

* **vasodilation** of surface blood capillaries --\> to inc heat loss by radiation * **increased sweating** * **relaxation of erector pili muscles** --\> hairs lie flat * **dec metabolic rate** * (and behavioral component, like taking off jacket if too hot)

Question 31

heat **conservation** response (if body temp is dec) triggered by hypothalamus

Answer 31

* **vasoconstriction** of surface blood capillaries --\> reduce heat loss by radiation * **reduce sweating** * **contract erector pili muscles --** hairs pulled upright * **shivering** * **increased metabolic rate**

Question 32

regulation of water intake: 2 types of thirst

Answer 32

* **volumetric** thirst \<-- from decreased blood volume (i.e. hemorrhage) * **osmometric** thirst \<-- from dehydration/ hypertonicity (inc. in blood solutes)

Question 33

outputs of hypothalamus from thirst: PVN

Answer 33

* paraventricular nucleus (PVN) in hypothalamus --\> * increases antidiuretic hormone (ADH)/vasopressin * inc water retention; and dec urine production --\> * returns fluid volume to homeostatic levels

Question 34

outputs of hypothalamus from thirst: ## Footnote **lateral hypothalamic area (LHA) of hypothalamus**

Answer 34

* lateral hypothalamic area (LHA) of hypothalamus --\> * directly stimulates thirst and drinking (promote the sensation of thirst to encourage the behavior)

Question 35

hypovolemic thirst: inputs to hypothalamus

Answer 35

* **KIDNEYS** detect reduced blood flow --\> inc renin --\> inc angiotensin ii --\> act on hypothalamus --\> release ADH/vasopressin --\> inc water retention/ dec urine production * **CARDIOVASCULAR SYSTEM** detects reduced BP --\> vasoconstriction to counteract blood loss --\> hypothalamus --\> (same final steps as other)

Question 36

how is hypothalamus related to emotion?

Answer 36

* hypothalamus is connected to **limbic system** structures by the fornix * hypothalamus mediates **autonomic manifestations of emotion**