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CEP > WEEK 1 > Flashcards

WEEK 1 Flashcards

1
Q

What are the three main types of cell communication?

A

Autocrine, Paracrine and Endocrine signalling

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2
Q

What is autocrine signalling?

A

Secretory cell=target cell (intracrine=same but acts within same cell rather than binding to cell’s target sites)

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3
Q

What is paracrine signalling?

A

Secretory cell adjacent to target cell

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4
Q

What is endocrine signalling?

A

Substance secreted into general circulation and reaches target cell at a distance

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5
Q

What are the nicotinic effects of ACh?

A

muscle contraction, synaptic transmission (autonomic ganglia, parasympathetic postganglionic, CNS)

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6
Q

What are the receptors that cause nicotinic effects of ACh?

A

nAChRs (ion channels)

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7
Q

What are the muscarinic effects of ACh?

A

bradycardia, salivation, bronchospasm, mydriasis

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8
Q

What are the receptors that cause muscarinic effects of ACh?

A

M1-5 (GPCRs)

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9
Q

How do you measure ligand binding to a receptor?

A

Radioactive binding assay

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10
Q

Describe the process of radioactive binding assay

A

add radioactive ligand to sample containing receptor, wash, measure radioactivity

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11
Q

What is the equation for fraction of occupancy?

A

[Radioactive ligand]/[Receptor(total)]=[L]/[L]+Kd

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12
Q

What is the equilibrium dissociation constant (Kd) and what does it measure?

A

concentration of ligand where 50% of receptors are occupied by ligand=ligand affinity

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13
Q

What are the four main receptor types?

A

Ligand-gated ion channels (ionotropic)-eg. nAChRs
G-protein coupled receptors (metabotropic)-eg. mAChRs
Kinase-linked receptors-eg. cytosine receptors
Nuclear receptors-eg. oestrogen receptor

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14
Q

Process of GPCRs

A

Receptor in plasma membrane is bound by agonist, causes change in receptor conformation, activation, heterotrimeric G protein consistent of alpha, beta and gamma protein reassembles, active G protein receptors interact with G protein bound to plasma membrane by lipid anchors, G protein coupling, alpha, beta and gamma subunits dissociate causing nucleotide exchange-GDP moves off, GTP replaces it, activated G protein subunits regulate effector proteins, beta-gamma dimer formed which activates Ca2+ ion channels, GTP hydrolysis causes inactivation of Galpha protein

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15
Q

What effect does the Gs alpha subunit cause?

A

ATP-(adenylyl cyclase)->cAMP-(cAMP phosphodiesterase (PDE))->AMP

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16
Q

What effect does the Gq alpha subunit cause?

A

Gq->Phospholipase C->diacylglycerol-activates Protein Kinase C by binding of InsP3 to channels on ER surface, causing Ca2+ to move out and cause biological response

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17
Q

Describe the process of hormonal regulation of glycogen metabolism

A

Gs->AC->cAMP->Protein Kinase A
Protein Kinase A causes: Glycogen synthase phosphorylation (inactivation), Phosphorylase kinase phosphorylation (activation) which causes glycogen phosphorylase b to form glycogen phosphorylase a which causes glycogen hydrolysis in the liver

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18
Q

What is the role of Protein kinase?

A

Protein phosphorylation

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19
Q

What is the role of Protein phosphatase?

A

Protein dephosphorylation

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20
Q

TSH receptor signalling in the Thyroid with relation to the cAMP/PKA pathway

A

TSH binds to TSHR, causes Gs alpha subunit to activate adenylyl cyclase which forms cAMP from ATP, which activates Protein Kinase A (PKA), causing transcription of genes that form Tg-1, from which T3 and T4 are formed

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21
Q

What is an autonomous thyroid adenoma (ATA)?

A

benign tumour in the thyroid gland which causes hyperthyroidism-60% of cases due to activating TSHR mutation

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22
Q

What do homozygous muts suffer from and why?

A

Severe congenital hypothyroidism due to inactivating TSHR mutations

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23
Q

What do heterozygous muts suffer from and why?

A

Mild/compensated hypothyroidism due to inactivating TSHR mutations

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24
Q

What is the effect of positive feedback loops?

A

Stimulatory

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25
Q

What is the effect of negative feedback loops?

A

Inhibitory

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26
Q

What is a hormone?

A

A substance secreted directly into the blood by specialised cells which is present in minute concentrations and binds to specific receptors on target cells

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27
Q

What is homeostasis?

A

The maintenance of a constant internal environment

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28
Q

Describe the endocrine feedback loop

A

Stimulus activates Gland A which produces Hormone A, which activates Gland B/target tissue which activates Hormone B which causes action. Hormone B also causes inhibition of Gland A and Hormone A.

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29
Q

What are the two types of hormones?

A

Lipophilic (steroid hormones) and Water-soluble (peptide hormones)

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30
Q

What is a lipophilic (steroid) hormone?

A

A substance able to pass through the phospholipid bilayer and bind to receptors in the target cell

31
Q

What is a water-soluble/hydrophilic (peptide) hormone?

A

A substance unable to pass through the membrane so binds to a receptor on the cell surface and causes conformational change which mediates effects into the cytoplasmic side via secondary messengers

32
Q

How are hormones regulated?

A 
Biosynthesis
Secretion
Circulation/distribution
Peripheral modification
Receptor interaction
Hormone metabolism/excretion
33
Q

What are the basic actions of the thyroid hormones?

A

basal metabolic rate, growth

34
Q

What is the basic action of the parathyroid hormone?

A

Ca2+ regulation

35
Q

What are the basic actions of cortisol?

A

glucose regulation, inflammation

36
Q

What are the basic actions of aldosterone?

A

BP, Na+ regulation

37
Q

What are the basic actions of catecholamines?

A

BP, stress

38
Q

What are the basic actions of oestradiol?

A

Menstruation, femininity

39
Q

What are the basic actions of testosterone?

A

Sexual function, masculinity

40
Q

What are the basic actions of insulin?

A

Glucose regulation

41
Q

What is the basic action of ANP?

A

Na+ regulation

42
Q

What is the basic action of Vitamin D?

A

Ca2+ regulation

43
Q

What is the basic action of ACTH?

A

Adrenal cortex regulation

44
Q

What is the basic action of TSH?

A

Thyroid hormone regulation

45
Q

What are the basic actions of GH?

A

Growth, metabolism regulation

46
Q

What are the basic actions of LH/FSH?

A

Reproductive control

47
Q

What is the basic action of Prolactin?

A

Breast milk production

48
Q

What is the basic action of ADH?

A

Water regulation

49
Q

What is the basic action of Oxytocin?

A

Breast milk expression (lactation)

50
Q

What is the result of binding of an auto-antibody to TSH receptors?

A

stimulation of unregulated hyper-production of thyroid hormones with no negative feedback to pituitary gland to secrete less TSH

51
Q

What is the general management strategy for hormone excess?

A

Remove/block

52
Q

What is the general management strategy for hormone deficiency?

A

Replace

53
Q

What are three types of glands?

A

Endocrine, exocrine and mixed glands

54
Q

What are endocrine glands?

A

Ductless glands that release secretions (hormones) into the blood directly from cells

55
Q

What are exocrine glands?

A

Glands that release their secretions outside the body and may be ducted

56
Q

What are mixed glands?

A

Glands that can act as endocrine and exocrine glands

57
Q

What are the four characteristic differences between the two major regulatory systems of the body (endocrine and nervous systems)?

A

Many hormones vs. few neurotransmitters
Generally slow vs. generally rapid
Generally long-lasting vs. generally short-lived
Widespread-in blood vs. localised-cell to cell

58
Q

What are the different mechanisms of chemical signalling?

A

Neuroendocrine, endocrine, paracrine, autocrine and intracrine.

59
Q

What is feedback?

A

Process by which body senses change and responds to it

60
Q

What is negative feedback?

A

Process by which body senses change and activates mechanism to reduce it (inhibits hormone release in endocrine cascade)

61
Q

What is positive feedback?

A

Process by which body senses change and activates mechanism to amplify it (stimulates hormone release in endocrine cascade)

62
Q

Process of peptide hormone synthesis, packaging and release

A

1 ) mRNA on ribosomes binds AA into peptide chain called preprohormone, chain is directed into the ER lumen by a signal sequence of AA

2) enzymes in the ER chop off signal sequence creating inactive prohormone which passes from the ER through the Golgi complex
3) secretory vesicles containing enzymes and prohormone bud off the golgi and enzymes chop the prohormone into one or more active peptides plus additional peptide fragments
4) secretory vesicles release the contents by exocytosis into the extracellular space
5) hormone moves into circulation for transport to target

63
Q

Where are steroid hormones synthesised?

A

Adrenal gland

64
Q

Describe the storage and transport of steroid hormones

A

Not stored but synthesised in cytosol as required, then diffuse out of the cell and transported as lipoprotein

65
Q

Process of steroid hormone synthesis

A

1) hydrolysis of esters and release of cholesterol from the cell membrane
2) cholesterol to pregnenolone in mitochondria
3) processing of pregnenolone to necessary hormone via cell-specific enzymes in SER
4) egress by diffusion/facilitated diffusion

66
Q

What regulates the movement of cholesterol to mitochondrion?

A

Steroid acute regulatory protein (stAR)

67
Q

What regulates steroid acute regulatory protein (stAR) activity and cholesterol processing?

A

ACTH

68
Q

How is aldosterone formed in the zona glomerulosa but not the other adrenocortical regions?

A

Zona glomerulosa contains cells expressing enzymes leading to aldosterone synthesis which are not present in the other regions

69
Q

What are amine hormones?

A

Thyroid hormones->small, non-polar molecules-therefore hydrophobic and lipophilic

70
Q

What is the difference in the number of iodine atoms in thyoxine/tetraiodothyronine (T4) and triiodothyronine(T3)?

A

T4=4 iodine atoms

T3=3 iodine atoms

71
Q

Which hormones require carrier proteins?

A

Steroid and thyroid hormones

72
Q

What is the effect of hormone carrier proteins?

A

Increase solubility
Increase half-life
Reservoir in blood

73
Q

What are the two types of carrier proteins?

A

Specific binding proteins (eg. thyroid binding globulin (TBG) and cortisol binding globulin (CBG))
Non-specific binding proteins (eg. albumin-loose binding->binds aldosterone)

74
Q

What is the site of action of hormones?

A

Protein/peptide=cell surface receptors

Steroid=intracellular receptors in cytoplasm/nucleus-hormone-receptor complex binds to HRE (hormone response element)

CEP (9 decks)

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