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Endocrinology > Physiology > Flashcards

Physiology Flashcards

1
Q

Message transmission: Synaptic

A

across synaptic cleft

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2
Q

Is synaptic local or general?

A

Local

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3
Q

The specificity of synaptic depends on?

A

anatomic location and receptors

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4
Q

Message Transmission: Paracrine & Autocrine

A

By diffusion in interstitial fluid

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5
Q

Is Paracrine & Autocrine local or general?

A

locally diffuse

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6
Q

The specificity of Paracrine & Autocrine depends on?

A

receptors

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7
Q

Message transmission: Endocrine

A

by circulating body fluids

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8
Q

Is Endocrine local or general?

A

general

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9
Q

The specificity of Endocrine depends on?

A

receptors

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10
Q

Message transmission: neuro-endocrine

A

by circulating body fluids

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11
Q

Is neuro-endocrine local or general?

A

general

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12
Q

The specificity of neuro-endocrine depends on?

A

receptors

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13
Q

What are the 2 major control systems?

A

1) Endocrine

2) Nervous System

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14
Q

Hormone

A

“to set in motion, to excite”

  • a chemical substance released in small quantities from certain glands (endocrine) that travels through the circulatory system to elicit a typical physiological response in other cells and tissues, called target cells/tissues
  • includes “neurohormones”
  • NOT CO2, intracellular messengers like cyclic AMP
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15
Q

3 general categories of hormones?

A

1) Steroids & Steroid-Like
2) Amino acid derivatives (catecholamines & thyroid hormones)
3) Peptides & Proteins

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16
Q

Where are steroids & steroid-like hormones from?

A

cholesterol

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17
Q

Where are Amino acid derivative hormones from?

A

tyrosine

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18
Q

Androgens

A

“steroids”

  • testosterone
  • dihydrotestosterone
  • weaker androgens (androstenedione, DHEA, DHEA-S)
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19
Q

Ductless glands

A

-secret into ECF (into blood)

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20
Q

Estrogens

A

“steroids”

  • estradiol-17beta (E2)
  • weaker estrogens (estrone, estriol)
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21
Q

Progestagens

A

“steroids”

-progesterone

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22
Q

Mineralocorticoids

A

“steroids”

  • aldosterone
  • deoxycorticosterone
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23
Q

Glucocorticoids

A

“steroids”

cortisol

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24
Q

“steroid like” Vitamin D

A

“steroids”

-cholecalciferol & its derivatives

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25
Q

Catecholamines

A

“amino acid derivatives”

  • norepinephrine
  • epinephrine
  • dopamine (DA, PIH)
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26
Q

Thyroid Hormones

A

“amino acid derivatives”

  • thyroxine (T4)
  • tri-iodothyronine (T3)
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27
Q

Hormones using intracellular receptors?

A

-steroids (TH)

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28
Q

Hormones using surface receptors?

A

-cachacolomines, proteins, peptides

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29
Q

Functions of second messengers?

A

1) amplify signals (from 1 to 1,000,000 molecules)

2) disperse signals (to many places in cell)

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30
Q

Permissiveness

A
  • an increase in response to the hormone

ex: thyroid hormone increase response of fat cells to epinephrine

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31
Q

Transport of hormones in blood

A
  1. free (unbound) hormone in plasma (H)
  2. Bound to large proteins (hormone binding proteins, “BP”, hormone binding globulins “BG”)
  3. “total” hormone conc. in plasma = free + bound
  4. Active form of hormone
    - on target cells
    - on feedback sensors
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32
Q

How to measure hormone?

A

-usually by competitive binding assays (radioimmunoassays, readireceptor assays, measure ability to bind to an antibody or to a “receptor” not always biological activity)

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33
Q

Circadian Diurnal Rhythm

A

-one major secretory period/day

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34
Q

Circadian Ultradian Rhythm

A
  • multiple times a day

- pulsatile secretion (a type of ultradian rhythm)

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35
Q

The 3 ways that blood levels of a hormone can be altered?

A

1) increase/decrease secretion rate
2) increase/decrease conc. of plasma hormone binding protein for that particular hormone
3) increase/decrease degradation rate (clearance)

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36
Q

Causes of endocrine disease?

A
  • over/underproduction of a hormone
  • alterations in receptors (# or affinity)
  • post-receptor events in target cells
  • altered metabolism of the hormone
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37
Q

Synthesis of Peptides/Proteins & Catecholamines

A

nearly continuous, mild regulation

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38
Q

Storage of Peptides/Proteins & Catecholamines

A

granules

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39
Q

Secretion of Peptides/Proteins & Catecholamines

A

regulated (& taken from these stores)

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40
Q

Transport of Peptides/Proteins & Catecholamines

A

mostly free

41
Q

Half lives of Peptides/Proteins/Catecholamines

A

Peptides: few minutes
Proteins: minutes
Catecholamines: few minutes in plasma

42
Q

Do Peptides/Proteins/Catecholamines need to be activated?

A

no

43
Q

Receptor binding of Peptides/Proteins?

A

surface (on plasma membrane)

44
Q

Actions on cells of Peptides/Proteins?
Mechanism?
Rapidity?
Duration?

A
  • second messangers
  • fast (sec/min); some slower (few hours)
  • brief (few min); some longer
45
Q

Degradation of Peptides/Proteins?

A

much( to AA in kid, liver, target tissues)

46
Q

Excretion of Peptides/Proteins?

A

little, some exceptions

47
Q

Receptor binding of Catecholamines?

A

Surface (alpha, beta)

48
Q

Actions on cells of Catecholamines?
Mechanism?
Rapidity?
Duration??

A
  • second messanger
  • fast (sec)
  • brief (min)
49
Q

Degradation of Catecholamines?

A

much by MAO, COMT

50
Q

Excretion of Catecholamines?

A

VMA, Metanephrine, & nor-metanephrine

51
Q

Synthesis of Steroid Hormones?

A

little, until stim; regulated

52
Q

Storage of Steroid Hormones?

A

little

53
Q

Secretion of Steroid Hormones?

A

as synthesized

54
Q

Transport of Steroid Hormones?

A

mostly bound,

half life: hours-days

55
Q

Activation of Steroid Hormones?

Degradation of Steroid Hormones?

A
  • testosterone to DHT; vit D to 1,25(OH)2

- liver, elsewhere

56
Q

Actions of Steroid Hormones on cells:
Mechanism
Rapidity
Duration

A
  • gene activation
  • slow (hr)
  • lone (hr-day)
57
Q

Excretion of Steroid Hormones?

A

urine (mainly)

58
Q

Thyroid hormones?

A

synthesis: partially - precursor (thyroglobulin)
storage: in precursor form (thyroglobulin)
secretion: slow, ~continuous
transport: mostly bound >99%
T1/2 days 6-T4 1-T3
activated: thyroxine (T4) to T3
binding to receptors: nuclear
mechanism: gene activation
rapidity: slow (hr)
duration: long (days)
degradation: liver, products recycled
excretion: very little (enterohepatic circulation)

59
Q

Positive Feedback

A

endocrine system’s response to a stimulus reinforces that stimulus

60
Q

Negative Feedback

A

endocrine system’s response to a stimulus is to reduce (negate, oppose, minimize) that stimulus

61
Q

Pituitary

A
  • at base of brain in bony pocket (sella turcica)
  • connects to bottom of brain by stalk of tissue (the infundibulum) containing nerves and special veins (long portal veins)
  • anterior
  • posterior
62
Q

Hypothalamus

A
  • has many regulatory functions, including control over many endocrine glands and their hormones
    1) various nuclei-clusters of nerve cell bodies that synthesize on of the hypothalamic releasing hormones that regulate secretion of hormones from the anterior pituitary gland, tow posterior pituitary gland hormones (ADH/OT)
    2) bottom portion = median eminence, axon terminals of neurons containing the hypothalamic releasing hormones that regulate the anterior pituitary gland, these RHs are secreted into first capillaries of a portal system.
63
Q

Posterior Pituitary

Neurohypophysis

A

axoplasmic flow through center of axon

-takes a week

64
Q

Hypothalamo-pituitary portal system

A

from hypothalamus to the anterior pituitary

65
Q

Hormones from posterior pituitary?

A
  • oxytocin (OT)

- vasopressin (VP; ADH; antidiuretic hormone)

66
Q

Neural Extension of Hypothalamus

A

1) Nerve axons come mainly from 2 nuclei in hypothalamus: supraoptic nucleus (SON) and paraventricular nucleus (PVN)
2) Axons terminate near capillaries in the posterior pituitary: store and release their hormones here

67
Q

Pars nervosa of posterior lobe: structure

A
  • neurosecretory nerve fibers from PV & SON (hypothalamohypophyseal T)
  • associated cells - pituicytes
68
Q

Pars nervosa of posterior lobe: Function

A

release 2 hormones

OT & VP

69
Q

Oxytocin

A
  • stimulates contraction of smooth muscles in pregnant uterus
  • contraction of myoepithelial cells in mammary gland
70
Q

Vasopressin

A
  • regulates retention of water (increase water channels in walls of kidney), increase water reabsorption
  • increase contraction of arterial smooth muscle; increase blood pressure
71
Q

Structure, Synthesis, Secretion of ADH & OT

A
  • nonapeptides with S-S bridge
  • synthesized as much larger molecules
  • stored in granules with (neurophysins I & II)
  • secreted-when action potentials reach nerve terminals, analogous to neurotransmitter release, secreted together with their respective neurophysins
72
Q

Control of Secretion: Oxytocin

A
  • dilation of cervix

- suckling

73
Q

Control of Secretion: ADH

A

-decrease ECF plasma volume, acts via volume receptors
decrease PV by 5-10% for ADH secretion
-increase osmolarity, very sensitive, increase osm 1-2% to increase ADH)
location of osmoreceptors: hypothalamus

74
Q

Effect of stalk section on nerve tracts to posterior pituitary?

A

1) pee a lot
2) drank lots of water
- then capillaries grew in and problem was fixed
- transient diabetes incipideous

75
Q

Intermediate Lobe of Pituitary

A

-may secrete MSH

76
Q

Pituitary blood supply

A

-hypophyseal portal veins

77
Q

Anterior Lobe of Hormones

A

-GH
-PRL
-ACTH
-FSH
-LH
-TSH
“trophic hormones” except prolactin

78
Q

Chemical nature/cell type of anterior lope hormones?

A
  • peptide: ACTH-is a split from pro-opiomelanocortin (POMC)
  • 39 amino acids; straight chain
  • COOH terminal has most of antigenic activity
  • only 20 needed for biological activity
  • ACTH1-24
  • alpha-MSH structure is located within the ACTH molecule
  • varied cell staining
79
Q

MSH activity

A

Melanocyte Stimulating Hormone

  • melanophores in skin in granules (amphibians)
  • synthesis of melanin in humans, darkens skin
  • structure of MSH lies within ACTH molecule, so excess ACTH causes hyperpigmentation
80
Q

Glycoproteins Hormone

A

TSH, FSH, LH
cell staining: basophils; occupy (15-20% pituitary volume)
Subunit structure: dimers of alpha and beta
alpha subunit is very similar in al three

81
Q

What subunit do you measure in a test assay?

A

beta

82
Q

Proteins

A 
GH, PRL
cell staining: acidophils
% volume of pituitary: 75%
somatotrophs-50% volume
lactotrophs-15-25%
83
Q

Somatotrophs

A
  • increase by T3

- decrease by somatostatin, exogenous GH Rx

84
Q

Lactotrophs

A
  • increase in pregnancy (estrogen effect)

- have increase blood flow

85
Q

Anatomy of Thyroid Gland

A
  • located in anterior neck
  • shape like a bow tie
  • left branch, right branch, isthmus
  • seen & palpated during regular exam
  • utilizes trace element iodine
  • generates hormones thyroxine & triiodothyronine & calcintonin
86
Q

Key steps in Thyroid Hormone Synthesis

A

1) Iodine uptake by Na+/I+ symporter
2) Thyroglobulin synthesis and release into follicular lumen
3) Iodination of tyrosine residues in thyroglobulin
4) Endocytosis of iodinated thyroglobulin into follicular cells
5) Generation and secretion of T3 & T4
6) Iodide recycling

87
Q

What decreases uptake of I- in step 1 of Thyroid Hormone synthesis.=?

A

ClO4-
TcO4-
SCN

88
Q

Thyroglobulin

A
  • large protein with few tyrosine residues
  • packed into secretory vesicles and released into apical lumen
  • inside surface of vesicle is thyroid peroxidase and thyroglobulin is on the outside
89
Q

Ratio of T4 to T3 release?

A

90% T4

10% T3

90
Q

Are T3 and T4 bound?

A

T4 - 99.98% bound

T3 - 99.5% bound

91
Q

What changes TBG of thyroid hormone?

A

Increase - hepatitis, pregnancy, heroin abuse
Decrease - steroid use
***the total amount of bound T4 & T3 stay the same

92
Q

Deiodinase Enzymes: Type 1

5’/3’

A

T4 to T3

  • responsible for all free T3
  • in Liver, Kidney, Tyroid
  • falls in starvation
93
Q

Deiodinase Enzymens: Type 2

5’/3’

A

T4 to T3

  • in Pituitary, CNS, Placenta
  • does NOT fall in starvation
94
Q

Effect of Thyroid Hormone on: Basal Metabolic Rate

A

Hyperthyroid: increase
Hypothyroid: decrease

95
Q

Effect of Thyroid Hormone on: Carbohydrate Metabolism

A

Hyperthyroid: increase
Hypothyroid: decrease
when blood glucose does not change

96
Q

Effect of Thyroid Hormone on: Protein Metabolism

A

Hyperthyroid: increase (increase muscle wasting)
Hypothyroid: decrease

97
Q

Effect of Thyroid Hormone on: Lipid Metabolism

A

Hyperthyroid: increase (decrease serum cholesterol)
Hypothyroid: decrease (increase serum cholesterol)

98
Q

Effect of Thyroid Hormone on: Thermogenesis

A

Hyperthyroid: increase
Hypothyroid: decrease

99
Q

How does TSH increase thyroid hormone secretion?

A

1) Increase activity of NIS
2) Stimulates the iodination of thyroglobulin in the follicular lumen
3) Stimulates conjugation of iodinated tyrosines to generate T4 & T3
4) Increases endocytosis of iodinated thyroglobulin into follicular cells
5) Stimulates proteolysis of iodinated thyroglobulin in lysondosomes
6) Increases secretion of T4 & T3 into circulation
7) Exerts growth factor effects on thyroid cells, increasing size & #

Endocrinology (15 decks)

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