Physiology

Question 1

What does the endocrine system consist of?

Answer 1

Ductless endocrine glands at numerous locations

Question 2

How is specificity of hormone signalling achieved?

Answer 2

Chemically distinct hormones, specific receptors for each hormone, distinct distribution of receptors across target cells

Question 3

What are the major endocrine glands?

Answer 3

Pineal, hypothalamus, pituitar, parathyroid, thyroid, adrenal, pancreas, ovaries in female, placenta in pregnant female, testes in male

Question 4

What are the overall functions of endocrine system?

Answer 4

Regulation of nutrient metabolism, H20/electrolyte balance, RBC production, enabling change to stress, promoting growth +dev, controlling reproduction, controlling and integrating activities of CV and GI system

Question 5

What is autocrine signalling?

Answer 5

Cell secretes hormone or messenger that binds to autocrine receptors on same cell

Question 6

What is paracrine signalling?

Answer 6

Cell secretes hormone or messenger that binds to receptors on nearby cells

Question 7

What is endocrine signalling?

Answer 7

Cells secrete hormone or messenger that travel to target distant cells through bloodstream usually

Question 8

What are the 3 main classes of hormones?

Answer 8

Glycoproteins and peptides, steroids, tyrosine and tryptophan derivatives

Question 9

Describe glycoproteins and peptide hormones

Answer 9

Amino acid chains of varied length. May be simple, can contain disulphide bonds, can be multiple. E.g. oxytocin, insulin

Question 10

Describe steroid hormones

Answer 10

Derived from cholesterol e.g. cortisol, testosterone

Question 11

What are some tyrosine and tryptophan derivative hormones?

Answer 11

Adrenaline, thyroid hormones, melatonin

Question 12

Describe amine synthesis, storage, release and transport

Answer 12

Pre-synthesised, vesicle storage, released in response to stimuli by Ca2+ dependent exocytosis

Question 13

Are amines hydrophilic or hydrophobic?

Answer 13

Hydrophilic

Question 14

How are amines transported in plasma?

Answer 14

Mainly ‘free’

Question 15

Describe peptides and proteins synthesis, storage, release and transport

Answer 15

Pre-synthesised from longer precursor, vesicle storage, released in respose to stimuli by Ca2+ dependent exocytosis

Question 16

Are peptides hydrophilic or hydrophobic?

Answer 16

Hydrophilic

Question 17

How are peptides transported in plasma?

Answer 17

Mainly ‘free’

Question 18

Describe steroid synthesis, storage, release and transport

Answer 18

Synthesised and secreted upon demand. Stimuli increase based on: cellular uptake and availability of cholesterol, rate of conversion of cholesterol to pregnenolone

Question 19

Are steroids hydrophilic or phobic?

Answer 19

Hydrophobic

Question 20

Are steroids transported in plasma as free or bound molecules?

Answer 20

Mainly bound (~90%) to plasma proteins. Only free if biologically active

Question 21

Are steroids and thyroxine soluble or insoluble in plasma?

Answer 21

Relatively insoluble

Question 22

What do hormone carrier proteins do in terms of blood, and kidney filtration?

Answer 22

Increase amount transported in blood, and prevent rapid excretion by preventing filtration at kidney

Question 23

What does albumin do as a carrier protein?

Answer 23

Binds many steroids and thyroxine

Question 24

What does transthyretin do as a carrier protein?

Answer 24

Binds thyroxine and some steroids

Question 25

Are proteins and peptides soluble or insoluble in plasma?

Answer 25

Soluble

Question 26

What do carrier proteins act as in terms of hormone concentration?

Answer 26

A buffer and reservoir helping to maintain constant concentrations of free lipophilic hormone in blood

Question 27

Are free and bound hormones at equilibrium in the blood?

Answer 27

Yes

Question 28

What hormones can cross the capillary wall to activate receptors in target tissues?

Answer 28

Only free hormones

Question 29

What is the primary determinant of plasma concentration of hormones?

Answer 29

Rate of secretion

Question 30

What does negative feedback do in terms of hormone concentration?

Answer 30

Maintains plasma concentration at set level

Question 31

What does tropic mean?

Answer 31

Refers to hormone that acts upon another endocrine gland to regulate its secretion of hormone

Question 32

What is neuroendocrine control in terms of hormonal levels?

Answer 32

Elicits a sudden burst in secretion to meet a specific stimulus

Question 33

What is diurnal rhythm control in terms of hormonal levels?

Answer 33

Secretion rates fluctuate as a function of time- entrained to external cues such as day/night

Question 34

What are the most important routes of hormonal elimination?

Answer 34

Metabolism by liver, excretion by kidney

Question 35

What is the approximate half life of amines?

Answer 35

Seconds

Question 36

What is the approximate half life of proteins and peptides?

Answer 36

Minutes

Question 37

What is the approximate half life of steroids and thyroid hormones?

Answer 37

Hours to days due to binding

Question 38

What are the cell surface receptors?

Answer 38

GPCR, receptor kinases

Question 39

What activates GPCR?

Answer 39

Amines and some proteins/peptides

Question 40

What activates receptor kinases?

Answer 40

Some proteins/peptides

Question 41

What are the intracellular receptors?

Answer 41

Nuclear receptors

Question 42

The ligands of intracellular receptors are lipophilic, what does this allow?

Answer 42

Diffusion across the plasma membrane

Question 43

What activates class 1 nuclear receptors?

Answer 43

Steroid hormones

Question 44

What activates class 2 nuclear receptors?

Answer 44

Mostly by lipids

Question 45

What activates the hybrid class of nuclear receptors?

Answer 45

Thyroid hormone (T3) and other substances (similar in function to class 1)

Question 46

Where are class 1 nuclear receptors located?

Answer 46

In absence of activating ligand mainly located in cytoplasm bound to inhibitory HSP- move to nucleus when activated

Question 47

Where are class 2 nuclear receptors located?

Answer 47

Present in nucleus

Question 48

What does binding of insulin to receptor kinases cause?

Answer 48

Autophosphorylation of intracellular tyrosine residues, and recruitment of multiple adapter proteins, notably IRS1, which are also tyrosine phosphorylated- causes cellular effects

Question 49

What kind of transcription factors are nuclear receptors?

Answer 49

Ligand-gated

Question 50

Are steroid hormones lipophilic or phobic?

Answer 50

Lipophilic

Question 51

What happens to the receptor steroid complex after combining the intracellular receptor with steroid hormones?

Answer 51

Moves to nucleus, forms a dimer and binds to hormone response elements in DNA. Transcription of specific genes is switched on/off to: alter mRNA levels and the rate of synthesis of mediator proteins

Question 52

Describe insulin secretion in pancreatic B cell

Answer 52

Blood glucose elevation> increased diffusion of glutamate into B cell by GLUT2>phosphorylation of glucose by glucokinase>glycolysis of g6p in mito yielding ATP> increased ATP/DP ratio within cells closes ATP-sensitive K+channels causing depolarisation> opening of channels increases intra Ca2+ that triggers insulin secretion

Question 53

What does ATP binding to each of the Kir6.2 subunits in the Katp channel do?

Answer 53

Closes the channel causing depolarisation of the B cell and insulin release (when extracellular glucose high)

Question 54

What does ADP-Mg2+ binding to the SUR1 subunits of the Katp channel do?

Answer 54

Opens the channel maintaining the resting potential of the B cell and inhibits insulin secretion (when extracellular glucose is low)

Question 55

Ingestion of food stimulates the release of what from enteroendocrine cells in the SI?

Answer 55

Glucagon Like Peptide 1 (GLP-1) and Glucose Dependent Insulinotropic Peptide (GIP)

Question 56

From what enteroendocrine cells is GLP-1 released from?

Answer 56

L cells in the ileum

Question 57

From what enteroendocrine cells is GIP released from?

Answer 57

K cells in the jejunum/duodenum

Question 58

What do GLP-1 and GIP enhance from pancreatic B cells?

Answer 58

Increment insulin release (and delay gastric emptying), leading to enhanced glucose uptake/utilisation and decreased blood glucose

Question 59

What does GLP-1 decrease from pancreatic alpha cells?

Answer 59

Glucagon releae, leading to decreased glucose production and decreased blood glucose

Question 60

What are the main nutritional considerations in a T1DM patient?

Answer 60

Consistency and timing of meals and CHO, timing of insulin, monitoring blood glucose regularly

Question 61

What are the main nutritional considerations in a T2DM patient?

Answer 61

Wt loss, smaller meals and snacks, physical activity, monitoring blood glucose and medication (if on insulin)

Question 62

What can be the risks of alcohol in DM patients?

Answer 62

Hypoglycaemia, confusing hypo symptoms, increased risk of some cancers, HT, liver disease. Hidden calories may not be thought about

Question 63

What are the similar features of GPCR's?

Answer 63

7 transmembrane domain, associated G-protein compelx

Question 64

What are some cytokine receptors?

Answer 64

Prolactin receptor, GH receptor

Question 65

What does the ability to accurately measure hormone levels depend on?

Answer 65

Secretion pattern, presence of carrier proteins, interfering agents, stability of hormone (t1/2), absolute concentrations

Question 66

What does a raised TSH indicate about thyroid status?

Answer 66

Hypothyroid

Question 67

What does a suppressed TSH indicate about thyroid status?

Answer 67

Hyperthyroid

Question 68

When might TSH not be a reliable marker of thyroid status?

Answer 68

Pituitary dysfunction (secondary hypothyroidism or TSHoma)

Question 69

What does formal assessment of HPA axis require?

Answer 69

Dynamic testing

Question 70

At what time of day may a cortisol measurement indicate HPA axis function?

Answer 70

9am

Question 71

What does formal assessment of GH axis require?

Answer 71

Dynamic testing

Question 72

What can an IGF-1 measurement indicate?

Answer 72

GH hypersecretion

Question 73

Where is PRL secreted from?

Answer 73

Lactotroph cells of anterior pituitary

Question 74

Under what inhibition is PRL secreted under?

Answer 74

Tonic inhibition by hypothalamic dopamine

Question 75

What are the effects of PRL mediated by?

Answer 75

Prolactin Receptor

Question 76

What are some physiological causes of hyperprolactinaemia?

Answer 76

Pregnancy, lactation, nipple stimulation

Question 77

What are some pathological causes of hyperprolactinaemia?

Answer 77

Prolactinomas/mixed secreting adenomas. hypothalamic and pituitary stalk disorders, medication-dopamine antagonists, others (antidepressants, oestrogens etc), chronic renal failure, ectopic PRL production

Question 78

What is aldosterone regulated by?

Answer 78

RAAS and plasma potassium

Question 79

When is the RAAS system activated?

Answer 79

In response to a decrease in bp

Question 80

What happens when the RAAS system is activated?

Answer 80

Production of AT2 which causes vasoconstriction and aldosterone production to increase bp

Question 81

What is calcium homeostasis based on?

Answer 81

Diet, gut absorption, PTH, vit D

Question 82

What happens when decreased calcium occurs in the body?

Answer 82

Sensed by parathyroid gland, increase in PTH. Acts on kidneys to cause reabsorption of calcium, on bone for resorption and GI system for increased absorption by activating vitD to increase serum calcium levels

Question 83

What is the primary action of 1,25-(OH)2 D3?

Answer 83

To promote gut absorption of calcium by stimulating formation of calcium-binding protein within the intestinal epithelial cells