Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

SMP - MNE Exam 1 > Lecture 6: Posterior Pituitary > Flashcards

Lecture 6: Posterior Pituitary Flashcards

1
Q

What is the main type of neurons in the post pit? Describe them.

A

Magnocellular neurons: large and contain sulfur (through cysteine)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

From what 2 hypo nuclei do the magnocellular neurons of the post pit originate from?

A
  1. Paraventricular

2. Supraoptic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe the characteristics of the magnocellular neurons of the post pit.

A

Slow and high affinity: meaning they release hormones slowly but a very slight stimulus will cause them to release hormones because these are released in small quantities in the whole blood stream so concentrations are very small

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the 2 neurohormones released by the magnocellular neurons of the post pit?

A
  1. Oxytocin

2. Vasopressin (ADH)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the role of oxytocin?

A

Uterus and mammary glands contraction of smooth muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the role of ADH?

A

Reabsorption of water in kidney tubules to decrease plasma osmolality and concentrate urine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What kind of hormones are oxytocin and vasopressin? Therefore, where are they secreted?

A

Nonapeptides (9 AAs): hydrophilic so secreted directly into blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How closely related are oxytocin and vasopressin? 3 arguments.

A
  1. Share 7 out of 9 AAs (differ at 3rd and 8th positions)
  2. Arise from same progenitor: vasotocin
  3. Located on same chromosome and inverted (probably evolved through gene duplication)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What protects oxytocin and vasopressin from degradation by enzymes? Why is this important?

A
  • Carboxy end protected by AMIDATION: amide group left over from peptide bond cleavage to glycine that is not recognized as the carboxy-end by enzymes
  • Amino end protected by DISULFIDE BOND: forms a cyclic structure

Important because we have very low concentrations in the blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are 5 kinds of enzymes that degrade peptides?

A
  1. Proteases
  2. Exonucleases
  3. Amino-peptidases
  4. Carboxy-peptidases
  5. Endopeptidases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are both oxytocin and vasopressin synthesized as? Why?

A

Inactive precursors that are later cleaved

Purpose: to have the carboxy-end protected from enzyme degradation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the 3 vasopressin receptors?

A
  1. Vasopressin V2
  2. Vasopressin V1a
  3. Vasopressin V1b
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Where is Vasopressin V2 located? How does it work?

A

Location: kidney (distal and collecting tubules)

Allows for vasopressin to function as ADH to reabsorb water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What does ADH stand for?

A

Anti-diuretic hormone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Where is Vasopressin V1a located? How does it work?

A

Location: vasculature of CNS, smooth muscle, and liver
Acts as a vasoconstrictor:
1. PLC-beta degrades membrane phospholipids into DAG and IP3
2a. DAG stimulates PKC to stimulate contraction
2b. IP3 travels to ER to release calcium to stimulate contraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Where is vasopressin V1b located? How does it work?

A

Location: corticotrophs of ant pit

Works with CRH to release ACTH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Which neurohormone is the dominant regulator of ACTH?

A

CRH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Where are oxytocin receptors located? 2 locations

A
  1. Uterus: myometrium

2. Mammary glands: myoepithelium (smooth muscle)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the role of osmoreceptor afferent magnocellular neurons?

A

Regulate vasopressin secretion by post pit when plasma osmolality increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are the 2 types of magnocellular neurons?

A
  1. Osmoreceptor afferent

2. Non-osmoreceptor afferent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the role of non-osmoreceptor afferent magnocellular neurons?

A

Baroreceptors/volume receptors in carotid and aortic circulation to inhibit vasopressin secretion when BP or BV is too high

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How do the osmoreceptor afferent magnocellular neurons detect high blood osmolality? How sensitive are they?

A

When body is hyperosmolar the fenestrations of hypo let solute go through, this shrinks the cells that have fenestrations and activates the magnocellular neurons
VERY sensitive: respond to changes in osmolality of less than 1%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How would you characterize the osmotic regulation of vasopressin secretion?

A

Linear: increases as osmolality increases AT ANY BP!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How is urine osmolality affected by an increase in vasopressin secretion?

A

Increase in urine osmolality

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is the osmotic threshold?

A

The plasma osmolality threshold before vasopressin secretion = 280 mosm/kg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Equation to calculate vasopressin plasma concentration?

A

[AVP]p = 0.3 x (Posm - 280)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is the plasma osmolality of a normally hydrated person?

A

287 mosm/kg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is the plasma concentration of vasopressin of a normally hydrated person?

A

2.0 pg/mL

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is the urine osmolality of a normally hydrated person?

A

500 mosm/kg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Does duration of urination change with body size?

A

NOPE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What % increase in TBW causes maximal dilution of plasma vasopressin concentration and urine osmolality?

A

2%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What % decrease in TBW causes maximal concentration of urine osmolality? What is max concentration of urine?

A

2%

Max Uos > 1000 mosm/kg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What is the plasma concentration of vasopressin at maximal antidiuresis? Can it increase beyond that?

A

5 pg/mL

Yes, but this will have no effect on reabsorption of water in kidney

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What happens to increase TBW once maximal antidiuresis has been reached?

A

THIRST!

35
Q

How does drinking water affect vasopressin secretion? How? When? Purpose?

A

It inhibits it BEFORE CHANGES IN FLUID VOLUME OR OSMOLALITY by cold-sensitive oropharyngeal receptors being activated
Purpose: to ensure we are not overhydrated

36
Q

How does increasing BP influence the linear curve of vasopressin concentration vs plasma osmolality? Explain what this means.

A

The slope decreases making the osmotic threshold greater => this makes it more difficult for vasopressin to regulate plasma osmolality at high BP

37
Q

What is the relationship between vasopressin concentration and mean arterial pressure (MAP)?

A

Exponential

38
Q

What is the most powerful regulator of vasopressin concentration?

A

Hemorrhage aka BP

39
Q

What is the most important regulator of vasopressin concentration?

A

Osmotic regulation

40
Q

Describe the 8 steps that happens when vasopressin binds the V2 receptors?

A
  1. Vasopressin binds V2 on basolateral membrane
  2. Gas activation
  3. Adenylyl cyclase activation
  4. cAMP synthesis
  5. Protein kinase A activation
  6. Phosphorylation of vesicles in cytoplasm that contain aquaporins (AQP-2)
  7. Insertion of aquaporins into apical membrane to reabsorb water
  8. Water pumped back into the cell and then interstitial space via the AQP3 and 4 aquaporins of the basolateral membrane
41
Q

What kind of transport happens through aquaporins?

A

Facilitated diffusion

42
Q

What are the 8 ways in which the body regulates fluid electrolytes and BV?

A
  1. RAA system
  2. Adrenergic NS
  3. Vasopressin
  4. Atrial netriuretic hormone (ANP)
  5. Kinins
  6. Endothelins
  7. Prostaglandins
  8. Nitric oxide system
43
Q

What is diabetes insipidus characterized by?

A

Low BV and large dilute urine volume

44
Q

What are the 4 types of diabetes insipidus? What is the treatment for all of them?

A
  1. Central = neurogenic = hypothalamis
  2. Nephrogenic
  3. Dipsogenic
  4. Gestational

Treatment: long-lasting vasopressin agonist (snorted)

45
Q

What is central/neurogenic diabetes insipidus due to? Overall and 6 causes?

A

Inability to synthesize or secrete active vasopressin:

  1. Metastatic tumor
  2. Idiopathic
  3. Histiocytosis (immune related)
  4. Severe whiplash that severes the pituitary stalk
  5. Genetic
  6. Anatomical defect
46
Q

What is nephrogenic diabetes insipidus due to?

A

Inability of kidney to detect vasopressin: usually V2 or aquaporin receptor (AQP2) mutation

47
Q

What is dipsogenic diabetes insipidus associated with?

A

Excessive water drinking linked to psychiatric disorders: schizophrenia with over consumption of water

48
Q

What is gestational diabetes insipidus due to?

A

Placenta secretes vasopressinase that degrades vasopressin

49
Q

What is the effect of oxytocin on men?

A

Pair-bonding, fidelity and trust

50
Q

What is the suckling pathway of oxytocin production?

A

Infant sucks on boob stimulates reflex loop that synapses at spinal cord with hypo neurons which stimulates oxytocin secretion causing milk ejection

51
Q

What is the visual stimulus pathway of oxytocin production?

A

Woman sees, hears, or smells a crying baby it will stimulates oxytocin secretion causing milk ejection

52
Q

Where is milk ejected after oxytocin secretion?

A

Lumen of mammary gland

53
Q

How is uterine contraction stimulated during labor?

A

Increase in expression of oxytocin receptors in the myometrium

54
Q

How is uterus stretching stimulated during labor? 4 steps

A
  1. PLA2 and PLC are activated (PLC normal pathway)
  2. PLA2 produces arachidonic acid
  3. Arachidonic acid stimulates prostaglandin production: PGE2 and PGF2alpha
  4. Prostaglandins soften uterus
55
Q

What is atosiban? What has been figured out about it?

A

Oxytocin antagonist that is ineffective at delaying labor because oxytocin only plays a minor role

56
Q

What is adoptive breastfeeding?

A

The stimulation of breast enlargement and milk ejection without labor

57
Q

What is tocolysis?

A

The delaying or inhibition of labor during the birth process

58
Q

Why has pair-bonding become evolutionarily adaptive?

A

Because with pair-bonding you have a longer life-span, more intimacy (inversely correlated with negative psychological states, such as depressed mood, and positively correlated with immune function and cardiovascular health), and more paternal involvement leading to improved well-being of children

59
Q

What is the effect of vasopressin and oxytocin when secreted centrally in the brain?

A

Important for pair-bonding

60
Q

How do prairie and montane voles differ? Why?

A

Prairie voles share nests, take care of children, have monogamous relationships and montane voles do not, this is because prairie voles have more V1a receptors

61
Q

What part of the human V1a receptor is associated with fidelity and pair-bonding? What does a specific allele lead to?

A

The RS3 region

Allele: decreased likelyhood of marriage, happy relationships, and happy partner

62
Q

How does [AVP]p increase when there is a 2% TBW decrease?

A

Increases: x2

63
Q

Describe the sensitivity of the ADH and oxytocin receptors?

A

VERY sensitive because concentration in the blood is so low

64
Q

What enzyme cleaves the amide group protecting the carboxy end of oxytocin and vasopressin?

A

A signal peptidase in the ER

65
Q

What type is the V2 vasopressin receptor?

A

G alpha S protein coupled receptor: adenylyl cyclase activation

66
Q

What does stimulation of the V1a receptors cause? Inhibition?

A

Gq stimulation: Activation of phospholipase C

Gi inhibition: Activation of adenylyl cyclase

67
Q

What does stimulation of the oxytocin receptors cause?

A

Gq receptors:

  1. Activation of phospholipase C
  2. PLC degrades membrane phospholipids into DAG and IP3
    3a. DAG stimulates PKC to stimulate contraction
    3b. IP3 travels to ER to release calcium to stimulate contraction
68
Q

What are the 2 most important fenestrations for the osmoreceptor afferent magnocellular neurons of the hypothalamus?

A
  1. OVLT

2. SFO

69
Q

What is the plasma concentration of vasopressin prior to osmotic threshold being reached?

A

~0.5 pg/mL

70
Q

What does a 0.3 difference in Pavp cause? What does this mean?

A

A 3 L difference in urine volume over 24 hours with half the osmolality!
Very small changes in Pavp have huge consequences

71
Q

What is the osmotic threshold of thirst osmoreceptors? How does this compare to the osmotic threshold of vasopressin secretion? Why?

A

285-290 mosm/kg (higher than the vasopressin osmotic threshold)

Because our body can handle small changes in osmolarity, we have a whole system for that, might as well use it.

72
Q

What is a volitional control or incentive behavior? What is an example?

A

Cognitive process by which an individual decides on a particular course of action
Drinking or putting on a sweater when I’m cold

73
Q

What types of people do not feel thirst as much?

A

Old people

74
Q

Why do we prefer to drink cold water?

A

Because our oropharyngeal receptor will be better satisfied and thirst will be better satisfied

75
Q

What does volemia mean?

A

Tension

76
Q

What are the 2 parts of the kidney collecting duct that contain V2 receptors?

A
  1. Cortical collecting duct

2. Inner medullary collecting duct

77
Q

What regulates oxytocin secretion? 3 factors

A
  1. Osmotic regulation
  2. Suckling at nipple
  3. Sex
  4. Hearing/seeing/smelling a crying baby
78
Q

Which is the strongest oxytocin secretion regulator?

A

The first cry of a baby

79
Q

Why don’t increases in oxytocin induce labor?

A

Because it’s the increase in the number of receptors that really causes labor

80
Q

What is the only difference between the mammary and uterine oxytocin receptors?

A

In uterus PLA2 is also activated, in mammary glands only PLC beta is

81
Q

What drugs can be used to help adoptive breastfeeding? How does each work?

A
  1. Domperidone/Metoclopramide/Sulpiride/Chloropromazne: blocks pituitary dopamine receptors
  2. TRH: directly stimulates lactotrophs (PRL)
82
Q

What 3 things is pair-bonding characterized by?

A
  1. Partner preference
  2. Mate-guarding
  3. Bi-parental care of young
83
Q

What does parturition mean?

A

Labor

SMP - MNE Exam 1 (25 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions