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Physiology I > Endocrinology S1 > Flashcards

Endocrinology S1 Flashcards

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1
Q

Homeostasis

A

A dynamic steady state of maintaining a constant internal environment despite changing conditions

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2
Q

Negative feedback

A

Initial stimulus occurs and initiates a response that decreases the stimulus. Stabilizing effect

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3
Q

Positive feedback

A

Stimulus starts a response that further stimulates it. Must be turned off by an outside factor and is reinforcing.

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4
Q

Gap junctions

A

Local communication. Holes connecting neighbouring cells for free-passage of small ions and molecules

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5
Q

Contact-dependent control

A

Membrane proteins binding to membrane proteins of another cell. Local communication

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6
Q

Autocrine control

A

Molecules move through interstitial fluid to communicate with cells a short distance away. Local communication

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7
Q

Long-distance communication

A

Occurs in the endocrine system or nervous system (neurohormones)

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8
Q

Simple reflexes

A

Reflexes mediated by either the nervous system or endocrine system

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9
Q

Complex reflexes

A

Reflexes mediated by both system and go through several integrating system

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10
Q

Differences between neural and endocrine reflexes

A

Have different specificity, nature of the signal, speed, duration of action, coding for stimulus intensity

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11
Q

Exocrine glands

A

Secrete chemicals into an external environment

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12
Q

Endocrine glands

A

Secrete chemicals directly into the bloodstream

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13
Q

Primary endocrine organs

A

Main function is releasing hormones

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14
Q

Secondary endocrine organs

A

Have a primary function and release hormones in addition to the primary function

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15
Q

Hydrophilic hormone characteristics

A

Water-soluble, dissolve in blood, can’t cross the plasma membrane, not lipid-soluble

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16
Q

Hydrophobic hormone characteristics

A

Not water-soluble, can’t dissolve in plasma (have carrier-protein), lipid-soluble, cross plasma membrane by diffusion

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17
Q

Hydrophilic hormone examples

A

Peptide hormones, protein hormones, catecholamines

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18
Q

Hydrophobic hormone examples

A

Steroids and thyroid hormones

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19
Q

Protein/peptide hormones

A

3+ hydrophilic AAs made in advance and stores in vesicles before release to bind to membrane receptors. Short half-life

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20
Q

Preprohormones

A

Can contain many copies of the same hormone or more than one type. Cleaving separates them

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21
Q

Steroid hormones

A

Made from cholesterol and made on demand. Long half life

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22
Q

Amine hormones

A

Made from tryptophan or tyrosine and behave based on synthesis

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23
Q

Tryptophan derivatives

A

Behave like peptides or steroids. Ex, melatonin

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24
Q

Tyrsosine derivatives

A

Catecholamines behave like peptides and thyroid hormones behave like steroids

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25
Hypothalamus function
Sends hormones to the anterior pituitary to secrete its own hormone
26
Anterior pituitary vs posterior pituitary
Only the anterior pituitary can synthesize and release its own hormones
27
Synergistic effects
Caused by multiple hormones that act together for greater effect
28
Permissive effects
One hormone enhances the target organ's response to a second hormone (both are required)
29
Agtagonisitic effect
One hormone opposes actions of another
30
How is hormone secretion regulated?
Endocrine cells send signals to hypothalamus and anterior pituitary which also sends signals to hypothalamus to stop secretion. Negative feedback
31
Properties of receptors
High affinity, saturable, specific, reversible
32
Intracellular receptors
Bind lipid soluble hormones and can be in the cytosol or nucleus to alter gene transcription
33
Hormone response element
Hormone receptor complex binds to response element DNA sequence to elicit response
34
G Protein-coupled receptors
Large multisubunit-protein membrane-spanning proteins. Use lipids as second messengers to open ion channels and alter enzyme activity in the cytoplasm
35
Gs mechanism
1) signal molecule binds GPCR to activate Gs 2) G protein activates adenylyl cyclase to convert ATP > cAMP 3) cAMP activates protein kinase A 4) PKA phosphorylates proteins, leading to a cellular response
36
Gq mechanism
Activates phospholipase C to convert membrane phospholipids into diglyercol so IP3 can diffuse into the cytoplasm and release Ca++
37
Gi mechanism
Targets adenylyl cyclase and inactivates it
38
Off switch membrane receptors
Receptors can be endocytosed by a clatherin-coated pit, trapping receptors. Triggered by a ligand
39
How is Ca+ stored in bone?
In crystals called hydroxyapatite (have calcium and phosphate)
40
Osteoblasts
Bone forming cells
41
Osteoclasts
Break down bone, multi-nucleated by fusion of multiple cells
42
Osteocytes
Previously osteoblasts that are surrounded by bone matrix and maintain bone nearby
43
Osteoclast mechanism
Secrete HCl and proteases to break down bone and release Ca++ into the blood
44
How do osteoblasts and osteoclasts interact?
Osteoclast precursors communicate with osteoblasts through RANK receptor on the precursor and RANKL on the osteoblasts. Both coming together creates mature osteoclast
45
Osteoprotegerin
Osteoblasts secrete OPG to block RANKL/RANK interaction by binding to RANKL which reduces osteoclast activity
46
Parathyroid hormone
Released by cells on the back of the thyroid gland to increase plasma Ca++ when low
47
Parathyroid sensing
Have a Gq coupled receptor that inhibits PTH synthesis when calcium is bound
48
PTH mechanism
1) On bone, it increases cAMP > increases RANKL and decrease OPG > stimulates osteoclast activation 2) In kidneys, PTH increases Ca++ reabsorption at distal tubule, increases calcitriol
49
Calcitriol (vitamin D3)
Targets intestine, bone, and kidney to increase plasma calcium through reabsorption and mobilization from bone
50
Calcitriol formation
Skin has precursors that become inactive vitamin D3 when hit by UV > become another precursor in liver > PTH creates active form in kidneys
51
Calcitriol signalling
Lipophilic hormone that binds vitamin D to form a heterodimer to enter the nucleus and bind vitamin D response element that eventually creates calcium channels
52
Blood phosphate regulation
1) PTH increases phosphate release from bone and decreases reabsorption in kidney 2) Calcitriol increases phosphate absorption and reabsorptiomn
53
Calcitriol vs PTH
Calcitriol wants to make bone, PTH wants to increase blood Ca++
54
Calcitonin
Peptide hormone secreted from C cells of thyroid to reduce osteoclast activity
55
Nephrons
Excretes waste, regulates blood volume, controls electrolytes, blood pH and vitamin D (via PTH)
56
Nephron function at sections
Water is reabsorbed in loop of Henle > ions reabsorbed before distal tubule > variable water/solute reabsorption in cortex medulla
57
Vasopressin
Synthesized in hypothalamus, secreted from posterior pituitary to increase water reabsorption in the kidneys by regulating permeability (increases it)
58
Vasopressin regulation
If there is high plasma osmolarity, vasopressin (ADH) is released by osmoreceptors. Low blood pressure detected in the heart also stimulates the release
59
Vasopressin mechanism
Inserts water pores into the distal convoluted tubule and collecting duct of cell membranes in nephrons. Aquaporin water pores inserted into the apical membrane
60
Aldosterone
Steroid synthesized in the adrenal cortex to regulate sodium through Na+ reabsorption and K+ secretion
61
Aldosterone regulation
Stimulated by high K+ concentration in plasma and angiotension II via blood pressure. Inhibited by high Na+ in ECF
62
Aldosteron mechanism
Acts in the distal tubule and collecting duct to initiate the synthesis of protein channels and pumps for increase Na+ reabsorption and K+ secretion
63
Renal Juxtaglomerular Cells
Secrete renin to go into the liver to cleave angiotensinogen to create angiotension
64
Angiotension II
Created from cleavage of angiotension I in the lungs and acts on hypothalamus to stimulate aldosterone secretion
65
Natriuertic peptids
Peptides that act as hormones to stimulate water to be released from the body
66
ANP
Secreted by atria and neurons to decrease Na+ and water reabsoption and increases K_+reabsorption
67
BNP
Secreted by ventricles and neurons
68
CNP
Secreted by brain, pituitary, vessels and kidneys
69
Adrenal Medulla
Neuroendocrine tissue that produces and secretes catecholamine and is stimulated by the SNS (short-term stress)
70
Adrenal cortex structure
Surrounds adrenal medulla and is surrounded by a capsule 1) zona glomerulosa secretes aldosterone 2) zona fasciculata secretes glucocorticoids 3) zona reticularis secretes sex hormones
71
Zona ___ hormone formation
All are synthesized by cholesterol
72
Androgens (sex hormones) formation
DHEA > androstenedione > testosterone > DHT OR from androstenedione > estrone w/ aromatase enzyme > estradiol OR testosterone > estradiol w/ aromatase
73
Cortisol
Main gluccorticoid and is secreted following a diurnal rhythm to mediate long-term stress
74
Cortisol release
CRH released by hypothalamus > corticotropic cells stimulate anterior pituitary > ACTH send to adrenal cortex > cortisol secreted
75
Cortisol regulation
Excess cortisol sent to hypothalamus and anterior pituitary through negative feedback to turn off ACTH and CRH
76
Addison's disease
Excess secretion of adrenal steroids which causes hypotension and hypoglycemia
77
Cushing's syndrome
Cortisol excess causing hyperglycemia, muscle protein breakdown, lipolysis, etc
78
Cortisol roles
1) promotes gluconeogensis 2) breakdown of skeletal muscle protein for AA 3) enhances lipolysis 4) suppresses immune system
79
Anabolic processes
Occurs in a fed state and promotes glycogenesis, lipogenesis
80
Catabolic processes
Occurs in a fasted state and promotes glycogenolysis, lipolysis
81
Gluconeogensis
Creates of glucose from non-carbohydrate substrates. Occurs in a fasted state but is anabolic
82
Insulin
Anabolic peptide that binds to tyrosine kinase receptor to reduce blood glucose by promoting formation of glycogen, fat and protein
83
Insulin mechanism
Triggers GLUT4 receptors in the liver to increase glucose in the cell and out of the blood stream
84
Hexokinase
Activated by insulin to phosphorylate free glucose into glucose 6-phosphate to keep intracellular glucose low
85
Insulin release
Beta-cells in the pancreas detect glucose in the blood and increase ATP to block K+ channels, preventing K+ from leaving the cell > causing a depolarization > releasing Ca++ to trigger insulin release
86
Incretin effect
Gastrointestinal hormones cause an increase in insulin when glucose is in the small intestine
87
Gluagon-like peptide 1
Stimulated by nutrients and parasympathetic activity to increase insulin and decrease glucagon
88
Gastric inhibitory peptide
Stimulated by glucose and fatty acids to increase insulin
89
Glucagon
Increases glycogenolysis, gluconeogensis and ketogensis to prevent hypoglycemia by causes GLUT2 to transport glucose into blood
90
Cortisol and glucagon
Cortisol is catabolic and helps glucagon build up glucose by glycogenolysis
91
Glucagon mechanism
Alpha cells secrete glucagon in response to low glucose, SNS, amino acids to increase blood glucose
92
Sulfonylureas
Close K+ channels to treat type 2 diabetes, allowing Ca++ to enter cell, releasing insulin

Physiology I (6 decks)

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