Endocrine 1

Question 1

define homeostasis

Answer 1

The conceptual framework for the study/understanding of physiology

Question 2

who is Claude Bernard

Answer 2

Father of modern Physiology

concept “our internal environment remains remarkably consistent despite changes in the external milieu”

>provides stable conditions for body cells

Question 3

who is Walter Cannon

Answer 3

Coined the term “homeostasis”

describes the relative stability of the internal environment

Question 4

what does homeostatic control rely on ?

Answer 4

sensor : constant monitoring

integrating centre : to coordinate

response system : to change

Most systems operate in a negatice feedback manner

Question 5

what are the basic components of homeostatic system

Answer 5

Question 6

Basic endocrine dysfunctions

Answer 6

Hyperfunction : too much hormone

Hypofunction : too little hormone

Resistance : too little effect

Question 7

what is an endocrine gland ?

Answer 7

a tissue which releases (secretes) a substance into the bloodstream; this substance then travels via the blood to influence a target cell

Question 8

describe the minkowski experiment

Answer 8

Discovery of Insulin

1. Surgically removed pancreas ⇒ dog develops symptoms of diabetes
2. Implant pieces of pancreas under skin ⇒ prevents symptoms of diabetes

Question 9

What is the banting & best experiment

Answer 9

Discovery of Insulin

1. identified antidiabetic substance in pancreatic extracts
2. injected extracts prevents symptoms of diabetes (prevents elevated blood glucose)

Question 10

Insulin as a hormone

Answer 10

peptide hormone produced by the beta cells of the pancreas

promotes absorption of glucose from blood to sketetal muscle and fat tissue

Inactive stored form = hexamer, zinc ion and histidine residues holding together

active = monomer

Question 11

Kinds of hormones

Answer 11

1. Most are proteins & polypepide
2. steroids (cholesterol derivatives)
3. Amines (catecholamines)
4. Amins (thyroid)

Question 12

levels of hormones effect

Answer 12

autocrine; made by cell and acts on same cell

paracrine; made by cell and acts on neighbouring cell

endocrine; made by cell and passes through bloodstream to another cell

Question 13

mode of secretion for peptides

Answer 13

synthesis : in advance

storage : secretory vesicles

release from cell : exocytosis

transport in blood : dissolved in plasma

half life : short

example : insulin

Question 14

mode of secretion for steroids

Answer 14

synthesis : on demand

storage : N/A

release from cell : diffusion

transport in blood : bound to carrier proteins

half life : long

example : estrogen/androgen

Question 15

mode of secretion for amine (catecholamines)

Answer 15

synthesis : in advance

storage : secretory vesicles

release : exocytosis

transport in blood : dissolved in plasma

half life : short

example : epinepherine/norepinepherine

Question 16

mode of secretion of amines (thyroid)

Answer 16

synthesis : in advance

storage : secretory vesicles

release from cell : diffusion

transport in blood : bound to carrier proteins

half life : long

example : thyroxine (T4)

Question 17

conditions of receptor binding

Answer 17

• very high specificity for a particular hormone, but non-specific binding does occur (eg hormone “overspill”)
• there is a continuous turn-over of the receptor-hormone complex (essential for any signaling system)

Question 18

where are receptors found

Answer 18

receptors for most hormones are found in the plasma membrane of target cells

receptors for steroid and thyroid hormones are inside the target cell; steroid in cytoplasm & thyroid in nucleus

Question 20

Receptor Binding : transmembrane receptors (Overview)

Answer 20

• the hormone binds to the extracellular domain of the receptor and activates one or more cytoplasmic signalling pathways
• many of these pathways involve phosphorylation and enzyme activation
• some of these pathways lead to the DNA/mRNA/protein pathway response
• others just have a local effect in the target cell

Question 21

Adenylate cyclase pathways

Answer 21

1) hormone and receptor bind; G proteins dissociate
2) A-subunit activates AC
3) catalyzes production of cAMP
4) removes regulatory unit from phosphate kinase
5) PK activates other molecules - hormonal response

Question 22

Epinepherine binds what receptor in the adenylate cyclase pathway

Answer 22

beta-adrenergic receptors

Question 23

Phospolipase C-Ca2+ receptor binding

Answer 23

1) hormone + receptor
2) G-proteins dissociate; activates PLC
3) causes breakdown of membrane phopholipid tp IP3
4) IP3 binds endoplasmic reticulum; releases stored Ca2+ into cytoplasm
5) Ca2+ activates other molecules - hormonal response

Question 24

epinepherine binds what receptor in PIPLC

Answer 24

alpha-adrenergic

Question 25

Receptor binding : steroid hormone receptors (Overview)

Answer 25

1) steroid hormone (estrogen/androgen) transported bound to plasma carrier protein - lipophilic so they move across the plasma membrane
2) steroid hormone binds cell cytoplasm receptor
3) translocates to nucleus, binds to DNA (acts as a transcription factor)
4) stimulates gene transcription
5) protein products
6) response

Question 26

Receptor Binding : thyroid receptors

Answer 26

1) thyroxine (T4) + carrier binding protein
2) T4 converted to T3 (biologically active form)
3) T3 uses binding proteins to enter nucleus
4) hormone-receptor comples binds DNA
5) new mRNA
6) protein
7) response

Question 27

what are antagonistic effectors

Answer 27

“push-pull”

the increasing activity of one effector is accompanied by decreasing the activity of an antagonistic effector

Question 28

how are hormones secreted

Answer 28

in response to specific chemical stimuli or in response to nerve stimulation

Question 29

Difference between exocrine and endocrine glands

Answer 29

exocrine glands produce then secrete hormones via a duct whereas endocrine glands do not