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PHPY 301 > Lec 25 > Flashcards

Lec 25 Flashcards

1
Q

Neurohypophysis

A

posterior pituitary; release of hormones from the terminals in the posterior pituitary is determined by the electrical activity generated by their cell bodies in the hypothalamus.

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2
Q

Vasopressin

A

antidiuretic hormone ; primary hormone regulating water balance in the body; produced in the supraoptic nucleus

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3
Q

Osmolality

A

total concentration of solute molecules dissolved in solution and is expressed as milliosmoles per KG of H20.

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4
Q

2 types of Neurosecretory neurons

A

paraventricular and supraoptic nucleus

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5
Q

changes in osmolality

A

will cause rapid changes in cell volume & activate regulatory mechanisms in most cells to limit the extent of volume change

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6
Q

Regulatory volume decrease

A

When the extracellular solution is hypotonic causing an increase in cell size. Transport systems for solute exit are activated and water follows out of the cell.

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7
Q

Regulatory Volume Increase

A

when the extracellular solution is hypertonic causing a decrease in cell volume and size. Transport systems for solute entery are activated and water follows solute into the cell.

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8
Q

Set point osmolality for mammals

A

300 mOsmol kg

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9
Q

Aestivating Desert Frogs

A

A really high set point osmolality of around 650 mOsmol kg. Spend the summer in dormancy

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10
Q

Sharks

A

set point osmolality is equal to ocean sea water. near 1100 mOsmol kg

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11
Q

Homeostatic responses to Hypertonicity: Sodium balance

A

Increased Natriuresis, decreased Na Appetite

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12
Q

Homeostatic responses to Hypertonicity: water balance

A

Increased Thirst, increased Vasopressin

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13
Q

Homeostatic responses to Hypotonicity: water balance

A

Decreased thirst, decreased Vasopressin

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14
Q

Homeostatic responses to Hypertonicity: Conscious mechanisms

A

increased Thirst, Decreased Na appetite

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15
Q

Homeostatic responses to Hypertonicity: Unconscious mechanisms

A

Increased Vasopressin, Increased Natriuresis

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16
Q

Homeostatic responses to Hypotonicity: Sodium balance

A

decreased Natriuresis, Increased Na appetite

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17
Q

Homeostatic responses to Hypotonicity: Conscious mechanisms

A

(not proven) Increased Na appetite, decreased thirst

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18
Q

Homeostatic responses to Hypotonicity: unconscious mechanisms

A

(not proven) decreased Natriuresis, decreased Vasopressin

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19
Q

What would happen as a result of removing someone’s posterior pituitary in regard to vasopressin? (After raising their plasma osmolality)

A

increased urination. With no vasopressin there is no water retention.

20
Q

osmotic threshold

A

below this level there is no vasopressin and the kidney gets rid of H20

21
Q

Vasopressin concentration change as a function of osmolality

A

Increase osmolality = increase in vasopressin

22
Q

Magnocellular neurosecretory cells (MNC)

A

responsible for the release of both vasopressin and oxytocin

23
Q

Osmolality vs Firing rate of MNC

A

as Osmolality increases so does firing rate of MNC. (linear positive relationship)
where y = 0 , x= osmotic threshold

24
Q

Mammalian posterior Pituitary hormones

A

Vasopressin oxytocin

25
Q

Arginine Vasopressin

A

3 = PHE, 8 = ARG ; present in humans

26
Q

Lysine Vasopressin

A

3 = PHE, 8= LYS; present in pigs

27
Q

Oxytocin; Structure

A

3 = ILE, 8 = LEU

28
Q

Arginine Vasotocin

A

3=ILE, 8= ARG; present in non-mammalian invertebrate (birds etc.) a combo of Arg-vasopressin & oxytocin

29
Q

Hormones that are nonapeptides

A

Vasopressin and oxytocin

30
Q

preproneurophysin

A

a larger peptide that synthesizes vasopressin; transported down the MNC axons in the pituitary stalk to be released from terminals in the posterior pituitary.

31
Q

Osmoreceptors

A

located in the organum vasculosum laminae terminalis (OVLT) and subfornical organ (SFO) , two areas that breech the BBB.

32
Q

Volume contraction (graph)

A

Plasma AVP vs Plasma mOsm shift left of set point and increased slope

33
Q

Volume expansion (graph)

A

Plasma AVP vs Plasma mOsm shift right of set point and dampened slope

34
Q

Euvolemia

A

(normal) Plasma AVP and osmolality increase positively after the set point.

35
Q

Baroreceptors: changes in volume

A

Changes in plasma volume can increase the firing rate of MNC and release more vasopressin or less

36
Q

2 inputs affecting MNC firing

A
  1. Baroreceptor input (changes in plasma volume)

2. Osmoreceptors (OVLT & SFO) [as well as intrinsic sensitivity of MNC)

37
Q

circumventricular organs

A 
leaky regions of the BBB.  Excitatory inputs in the brain:
Pineal gland
Subfornical Organ
OVLT
Median eminence
Area postrema
Posterior pituitary

not protected by the BBB - easier to sense changes- increased sensitivity

38
Q

Transcytosis

A

intercellular cleft passage - due to Fenestra, Interendothelial clefts (holes) : leaky

39
Q

Brain capillary

A

are not leaky and have reduced transcytosis due to thick basal lamina and tight junctions; only allows passage diffusion of O2, H2O, CO2 and lipid solubles.

40
Q

MNC: detection of volume

A

MNCs detection of external plasma osmolality depends on osmotically-evoked change in cell volume. They lack the mechanisms for compensatory changes in cell volume that other cells possess (increased/decreased volume regulation)

41
Q

TRPV1: changes in osmolality (mechanosensitive)

A

osmosensitivity depends on the presence of a stretch inactivated non selective channel that opens with the increase in osmolality and causes depolarization and an increase likelihood of cell firing.

42
Q

Osmosensitive Cells lacking..

A

cells like MNCs lack normal volume regulatory mechanisms to detect changes.

43
Q

Hypotonicity detection:

A

No signal or AP due to stretch. (reduced resting potential making them less likely to fire)

44
Q

Set point detection:

A

normal rate of fire medium stretch

45
Q

Hypertonicity detection

A

rapid ap firing as a result of reduced stretch. (increased resting potential and making them more likely to fire) = release of vasopressin

46
Q

TRPV1: thermosensitiity

A

anticipatory vasopressin release - as temperature increases and sweating happens vasopressin is released.

PHPY 301 (23 decks)

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