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Endocrine System > Endocrine Physiology > Flashcards

Endocrine Physiology Flashcards

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1
Q

What is the endocrine system?

A

A system that controls function via the secretion of hormones which are carried in the blood to target organs

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2
Q

What is endocrine and exocrine?

A

Endocrine- ductless
Exocrine- ducted

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3
Q

What is autocrine and paracrine?

A

Autocrine- cells secrete chemicals that bind to receptors on same cell
Paracrine- chemicals diffuse in ECF to affect neighbouring cells

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4
Q

What are the 3 types of endocrine hormone?

A

Peptide hormones
Amine hormones
Steroid hormones

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5
Q

What are examples of peptide hormones?

A

TRH
FHS
Insulin

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6
Q

How are peptide hormones synthesised?

A
  1. Preprohormone formed by amino acids
  2. Enzymes in the ER form inactive prohormone
  3. Prohormone passes from ER through golgi apparatus
  4. Secretory vesicles containing enzymes and prohormone bud off golgi
  5. Enzymes chop prohormone into active peptides and peptide fragments
  6. Vesicles release contents by exocytosis
  7. Hormone moves into circulation
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7
Q

What is C-peptide?

A

Inactive fragment cleaved from prohormone

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8
Q

What is the clinical relevance of C-peptide?

A

Levels of c peptide measured to indicate endogenous insulin production

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9
Q

Which 2 amino acids are amine hormones derived from?

A

Tyrosine
Tryptophan (melatonin)

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10
Q

Which hormones have a similar action to peptide homrones?

A

Catecholamines (hydrophilic)

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11
Q

Which hormones have a similar action to steroid hormones?

A

Thyroid hormones (lipophilic)

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12
Q

What are steroid hormones derived from?

A

Cholesterol

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13
Q

What is the action of steroid hormones?

A

Translation produces new proteins for cell processes

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14
Q

What is the adenohypophysis?

A

Anterior pituitary

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15
Q

How is the anterior pituitary connected to the hypothalamus?

A

Hypothalamic-hypophyseal capillary portal system

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16
Q

What is the neurohypophysis?

A

Posterior pituitary

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17
Q

How is the posterior pituitary connected to the hypothalamus?

A

Continuation of hypothalamus axons and nerve terminals

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18
Q

What separates the anterior and posterior pituitary?

A

Pars intermedia

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19
Q

What are non tropic hormones?

A

Hypothalamus to posterior pituitary to blood
- Vasopressin (ADH)
- Oxytocin

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20
Q

What are tropic hormones?

A

Hypothalamus to anterior pituitary. Govern release of AP hormones
- TRH
- CRH
- GHRH
- GHIH
- GnRH
- PRH
- PIH (dopamine)

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21
Q

What does TRH control?

A

TSH
Prolactin

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22
Q

What does CRH control?

A

ACTH

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23
Q

What does GHRH and GHIH control?

A

GH

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24
Q

What does GnRH control?

A

FH and LH

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25
What does PRH and PIH (dopamine) control?
Prolactin
26
What is the glucostatic theory?
Food intake is determined by blood glucose
27
What is the lipostatic theory?
Food intake is determined by fat stores
28
What is an absorptive state?
Anabolic phase after eating
29
What is a post-absorptive state?
aka fasting state Catabolic phase between meals
30
What is normal range for [BG]?
4.2-6.3mM (5mM)
31
What are the anabolic actions of insulin?
Lowers [BG]: - Glycogenesis - Lipogenesis - Protein synthesis - Glucose oxidation
32
What are the catabolic actions of glucagon?
Raises [BG]: - Glycogenolysis - Gluconeogenesis - Ketogenesis
33
What do a cells produce?
Glucagon
34
What do B cells produce?
Insulin
35
What do d cells produce?
Somatostatin (GHIH)
36
What do PP cells produce?
Pancreatic polypeptide
37
What is the mechanism of insulin secretion?
1. Glucose enters B cell through GLUT transporter 2. This increases [ATP] by CAC 3. increased ATP causes K-ATP channel to close 4. K+ levels rise, depolarising the cell 5. Calcium channels open 6. Triggers vesicle exocytosis
38
What is the mechanism of insulin action?
1. Insulin binds to tyrosine kinase receptors on muscle and adipose tissue 2. Stimulates mobilization of GLUT4 transporters to cell membrane 3. Glucose enters the cell
39
What tissues are insulin depndent?
Muscle Adipose
40
How does the liver use insulin?
Not insulin dependent GLUT2 transporters Presence of insulin enhances glucose uptake into hepatocytes by creating a conc. gradient
41
What stimuli increases insulin release?
High [BG] Increased [AA] Increased glucagon Increased [gastrin, secretin, CCK] Vagal nerve activity (Parasympathetic)
42
What hormones form part of the glucose counter-regulatory control system?
Glucagon Epinephrine Cortisol Growth Hormone
43
What stimuli increases glucagon release?
Low [BG] High [AA]- prevents hypoglycaemia from insulin release Sympathetic innervation Cortisol and stress
44
What is the action of somatostatin?
Inhibit activity in GI tract Suppresses release of both insulin and glucagon (paracrine)
45
What is the effect of exercise on [BG]?
Entry of glucose into skeletal muscle is increased despite insulin absence - GLUT4 transporters migrate without insulin being present
46
What 3 factors affect growth?
Genetics Nutrition Hormone
47
What are the 2 periods of rapid growth?
Infancy- TH, insulin, GH Puberty- androgens, GH
48
When does GH becomes significant?
Around 10 months
49
What is the effects of TH on GH?
Permissive effect Low TH will cause reduced GH action
50
What is growth hormone?
aka Somatotropin Anabolic hormone
51
What neurohomrones control GH release?
GHIH (somatostatin) GHRH
52
What are the actions of GH?
Growth of long bones - Intermediate is IGF-1 Regulation of metabolism - Anti-insulin effect - Increases BG
53
What receptors does GH act on?
Tyrosine kinase receptors Phosphorylates intracellular targets
54
What is IGF-1?
Insulin like Growth factor, aka Somatomedin C Stimulates glucose uptake in muscle and in bone Released by liver in response to GH
55
What stimuli increases GHRH secretion?
Reduced energy supply (fasting, exercise, hypoglycaemia) Increased amino acids Physical stress and illness Delta sleep Sex homrones
56
What stimuli increases GHIH secretion?
Glucose Free fatty acids Ageing Cortisol
57
What conditions are caused by hypersecretion of GH?
Gigantism Acromegaly
58
What conditions are caused by hyposecretion of GH?
Deficiency of GHRH (hypothalamus) Deficiency of GHIH (pituitary) Precocious puberty Hypothyroid dwarfism
59
What are the 2 thyroid hormones?
T3- triiodothyronine T4- thyroxine
60
What are the 2 thyroid gland cell types?
C cells- secrete calcitonin Follicular cells- support TH synthesis
61
How are THS synthesised?
1. Thyroglobulin made in follicular cells and secreted into colloid with enzymes (thyroxidases) 2. Iodide enters follicular cells via symporter with NA+ 3. Follicular cells concentrate iodide and transport it to colloid via pendrin transporter 4. Thyroxidases oxidase iodide to iodine 5. Iodine combines with tyrosine residues on thyroglobulin to form thyroid hormones 6. TSH stimulates endocytosis of enzymes and thyroglobulin back into follicular cell 7. Proteolytic enzymes cut thyroglobulin to release T3 and T4 8. T3 and T4 pass into plasma and bind to thyroxine binding globulin
62
What thyroid hormone is more physiologically active?
T3 as receptors have a higher affinity T4 is deiodinated to T3 by deiodinase enzymes in plasma
63
Which hormones regulate TH release?
TRH (thyrotropin releasing hormone) from hypothalamus TSH (thyroid stimulating hormone) from AP
64
What is the action of TH?
Increases metabolic rate and promotes thermogenesis Increases gluconeogenesis Increases proteolysis Increases lipolysis Stimulates GH expression (growth) Brain development in utero
65
What does the adrenal medulla release?
Secretes catecholamines: - Epinephrine - Norepinephrine
66
What does the adrenal cortex release?
Secretes steroid hormones: 1. Zona gomerulosa- aldosterone 2. Zona fasciculata- cortisol 3. Zona reticularis- testosterone
67
Which enzyme is important in aldosterone and cortisol synthesis?
21- hydroxylase Lack causes adrenal hyperplasia
68
Which hormones control cortisol release?
CRH from hypothalamus ACTH from AP
69
What is the action of cortisol?
Glucocorticoid: increases BG - Gluconeogenesis - Proteolysis - Lipolysis - Decreases insulin sensitivity
70
What is the action of aldosterone?
Increases Na+ reabsorption (and water) Increases K+ excretion Secretion is controlled by RAAS Therefore effects blood volume and BP
71
What are the roles of calcium in the body?
Signalling Blood clotting Apoptosis Skeletal strength Membrane excitability
72
What is the effect of hypocalcaemia on neurones?
Increases Na+ permeability leading to hyperexcitation
73
What is the effect of hypercalcemia on neurones?
Decreases Na+ permeability leading to reduced excitability
74
What is the calcium distribution in the body?
99% bone 0.9% intracellular 0.1% ECF
75
Describe calcium in the ECF
Ca2+ plasma is 2.4 mM 40% protein bound 10% complexes to an anion 50% free (1.2mM)
76
What hormones increase calcium?
PTH- parathyroid hormone Calcitriol- active form of vitamin D - aka 1,25- dihydroxycholecalciferol
77
What hormone decreases calcium?
Calcitonin- released from C cells of thyroid gland
78
What is the action of PTH?
Increases [Ca2+] - Increases bone reabsorption - Increases kidney reabsorption of calcium - Increases renal excretion of phosphate so calcium is not deposited back in bone - Stimulates calcitriol release
79
What is the action of calcitriol?
Increases [Ca2+] - Increases intestinal absorption of calcium
80
Which hormone stimulates calcitriol in lactating women?
Prolactin - Increased demand for Ca2+ for milk production in lactation
81
What is the action of calcitonin?
Decreases [Ca2+] - Decreases bone reabsorption - Increases renal excretion of calcium

Endocrine System (13 decks)

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