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FNS 3: H+H

Neuro Lecture 3: Hypothalamus + Homeostasis

QuestionAnswer
In the classic view of HT & energy balance, the LH was thought to be the (what?) center feeding center
In the classic view of HT & energy balance, stimulation of the LH was thought to do what? elicit feeding
In the classic view of HT & energy balance, lesions of the LH were thought to do what? reduce feeding
In the classic view of HT & energy balance, the VMH was thought to be the (what?) center satiety center
In the classic view of HT & energy balance, stimulation of the VMH was thought to do what? reduce feeding
In the classic view of HT & energy balance, lesions of the VMH were thought to do what? increase feeding
In certain case studies (Reeves & Plum 1969), what were the effects described to accompany VMH lesions? hyperphagia, rage, and dementia
How is the revised/current view of the HT & energy balance different than the classic view? the current view is that both the LH and VMH play roles in feeding/metabolism- more important long term for body weight regulation than feeding
What is the new (named) hypothesis of HT & energy balance? Set Point Hypothesis- the HT encodes a set point for body weight and defends against deviations by regulating food intake and/or caloric expenditure
What are 3 examples of peripheral hormones that regulate feeding? Where are they secreted from? ghrelin (from gut), insulin (from pancreas), and leptin (from adipose)
When is ghrelin secreted? to initiate feeding
When is insulin secreted? to terminate feeding
When/why is leptin secreted? for long-term energy balance
What does orexigenic mean? promotes food intake
Which neuropeptide systems do leptin activate? Inhibit? Activates anorexigenic neuropeptide systems and inhibits orexigenic neuropeptide systems
In the fat mice example, which neuropeptide was deficient/dysfunctional? leptin
What was the population of O’Rahilly’s pediatric study? What were the results? obese, leptin-deficient kids that responded well to leptin therapy
Does dry mouth play a large or small role in the physiological basis of thirst? small
What are the two factors that must be balanced in fluid homeostasis? fluid intake and “sodium appetite”
What was one fluid injection technique that stimulated drinking in animals? hypertonic saline was injected into the rostral HT
Where are baroreceptors that facilitate autonomic responses for fluid homeostasis? aortic arch, venous return, and lungs
Which structure of the HT is known as the hypothalamic ‘sensor’? What is it sensitive to? OVLT (organum vasculosum of the lamina terminalis)- osmosensitive
Which structure of the HT is known as the hypothalamic ‘effector’? Where does it ‘effect’? supraoptic nucleus (SON)- magnocellular vasopressin and oxytocin neurons project to posterior pituitary
What do OVLT neurons regulate? activity of magnocellular neurosecretory cells in the supraoptic and paraventricular nuclei
What is another name for vasopressin (VP)? ADH
What is diuresis? urine production
What is natriuresis? sodium excretion
What do VP and oxytocin do? modulate diuresis and natriuresis
What is VP’s effect on antidiuresis (anti-urine production)? decreases urine production
What is oxytocin’s effect on natriuresis (Na excretion)? increases it
In a hypotonic state, what are the effects on thirst, vasopressin, oxytocin, and salt appetite? decrease thirst, VP, OT; increase salt intake
In a hypertonic state, what are the effects on thirst, vasopressin, oxytocin, and salt appetite? increase thirst, VP, OT; decrease salt intake
What are the major target organs for the release of ADH in fluid homeostasis? kidneys (water resorption), vessels (vasoconstriction/dilation for BP) and thirst (behavioral respsonse)
Precise detection of small changes in body temperature and ability to enact appropriate regulatory mechanisms to deal with challenges is a function of which structure? the hypothalamus
Which area contains the temperature reduction center? anterior hypothalamus
At what point do changes in blood temperature activate thermosensitive neurons to activate behavioral cooling systems? (how big of a change in temperature) less than 1 degree
Which area contains the heat conservation center? posterior hypothalamus
Name the type of molecules that increase the body temperature “set-point” to induce a fever (and other sick behaviors like sleep, less appetite)? pro-inflammatory cytokines (eg interleukins)
Where do cytokines access the brain? What type of organ is it? the OVLT (organum vasculosum of the lamina terminalis)- it’s a circumventricular organ
Once cytokines access the brain (OVLT), what molecules are sent to the hypothalamus? How are they catalyzed? prostoglandins (PGE-2) are catalyzed by cyclooxygenase
Once prostoglandins are formed, how is the temperature set point centrally regulated? PGE-2 acts on the anterior hypothalamus/preoptic area to increase the temperature set point
Which part of the hypothalamus is important for stress responses? anterior pituitary
What is the prototypical stress hormone? Where is it secreted from and what structure regulates its secretion? cortisol release from the adrenal glands is regulated by the hypothalamus
What is the system that mediates stress interactions between brain and periphery? HPA axis (hypothalamic-pituitary- adrenal axis)
What structure can stimulate the HPA axis? amygdala
What type of receptors are common in the hippocampus? glucocorticoid receptors
How does cortisol affect hippocampus function (memory formation) acutely? Chronically? facilitates acutely, “deleterious” chronically
What did Rush (1996) find about cortisol? they found non-suppression of cortisol in 27% of major depression subjects and 43% in bipolar individuals
What are some signs/symptoms of hypothalamus damage? thermal dysregulation, eating/metabolic changes, sleep disturbances- they depend on the location/extent of damage
What is the condition of widespread damage of the hypothalamus called? hypothalamic syndrome
Name 4 common causes of HT damage 1)infections along cranial cavity floor, 2) fractures of skull base, 3) Thiamine (B1) deficiency, 4) Pituitary tumors
What is Korsakoff’s disease associated with? alcoholism, memory disturbances (confabulations)- HT degeneration
What are pituitary tumors often associated with? visual disturbances (tunnel vision- bitemporal hemianopsia) and endocrine abnormalities
What is the cause of Cushing’s syndrome? pituitary tumor cells secrete high levels of ACTH
What are some symptoms of Cushing’s syndrome? abdominal obesity, diabetes, HBP, muscle weakness, fatigue, mood swings, decreased libido, menstrual disturbances in women, osteoporosis, ankle edema, excessive thirst, compromised immunity
Created by: mbyess