Endocrine System: Endocrine Signalling

Question 1

How do hormones communicate locally? (3)

Answer 1

gap junctions (direct cytoplasmic connection)
contact-dependent signals (interaction between membranes)
autocrine and paracrine signals (signal molecules act on secretory cell)

Question 2

What is autocrine?

Answer 2

when the cell acts on itself

Question 3

What is paracrine?

Answer 3

when the cell acts on nearby cells

Question 4

How do neurohormones move from neuron to response?

Answer 4

neuron (action potential) to neurotransmitter to blood to cell with receptor to response

Question 5

Why is endocrine system important?

Answer 5

metabolism regulation
responding to stress
regulating growth and development
controlling wake/sleep, temp, reproduction

Question 6

Parts of the endocrine system from head to toe (17)

Answer 6

pineal gland, hypothalamus, pituitary gland, thyroid, parathyroid, thymus, heart, liver, stomach and intestines, adrenal glands, pancreas, kidney, testes, ovaries, adipose tissue, skin

Question 7

Does an endocrine gland have a duct? What does it do? What is an example?

Answer 7

ductless
release hormones into surrounding fluid
adrenal gland

Question 8

Does an exocrine gland have a duct? What does it do? What is an example?

Answer 8

ducts
substances (non-hormonal) travel along surface
salivary glands
some organs have both types, eg. stomach and pancreas

Question 9

Three forms of signaling

Answer 9

autocrine
paracrine
endocrine (hormones diffuse into blood stream)

Question 10

3 main types of hormones + example of each

Answer 10

peptides and proteins (insulin)
steroids (progesterone)
amines (noradrenaline)

Question 11

How do the types of hormones differ? (3)

Answer 11

how they are made, stored, released and transported
how long they stay active
how they produce effects

Question 12

What are peptide/protein hormones? How are they made? Where are they stored? How long do they last? How are they transported?

Answer 12

amino acid chains of different length
many synthesized as preprohormone then modified into prohormone in Golgi body
short half-life
lipophobic/hydrophilic (transported in blood but cannot cross plasma membrane)

Question 13

What are steroids? When are they made? How long do they last? How are they transported? What do they do?

Answer 13

derived from cholesterol
made as needed in gonads, adrenal glands and
placenta
bound to carrier proteins in blood (increases half life)
lipophilic (cross plasma membrane to receptors in cytoplasm or nucleus
activates transcription of target genes

Question 14

What are amines? How are they made? What are the two types?

Answer 14

amino acids with modified groups
small size
derived from tyrosine (usually)
catecholamines and thyroid hormones

Question 15

Where do catecholamines come from? Are they lipophobic or lipophilic? What do they bind to? What do they do? How long do they last?

Answer 15

tyrosine derived
lipophobic (hydrophilic)
cell surface receptors
activates signal transduction cascades 
half-life short (like peptides)

Question 16

Where do thyroid hormones come from? Are they lipophobic or lipophilic? What do they bind to? What do they do? How long do they last?

Answer 16

iodinated tyrosine derived
lipophilic (hydrophobic)
intracellular receptors
activates genes
half-life few days (like steroids)

Question 17

What is a half-life?

Answer 17

time taken for concentration of substance to reach 50%

Question 18

How are hormones removed from plasma?

Answer 18

liver and kidneys remove

Question 19

What determines the size of a hormone response? (4)

Answer 19

amount
affinity (between hormone and receptor)
number of receptors
functionality of components downstream (of receptor)

Question 20

What is up-regulation and down-regulation?

Answer 20

up: target cells form more receptors in response
down: target cells lose receptors in response

Question 21

Where can receptors be located?

Answer 21

on surface of membrane
in cytoplasm
in nucleus

Question 22

How is hormone secretion regulated? And an example of each? (2)

Answer 22

negative feedback (maintaining homeostasis by responding to stimuli, maintaining appropriate levels of most hormones)
positive feedback (reinforcing stimulus, oxytocin release during childbirth)

Question 23

What three factors influence levels of hormone in plasma?

Answer 23

rate of secretion (regulated - most important)
rate of binding (to carrier proteins)
rate of metabolism (activation/degradation)

Question 24

What are the four types of cell surface receptors?

Answer 24

receptor channel
receptor enzyme
G protein-coupled receptor
integrin

Question 25

How does the receptor channel work?

Answer 25

ligand binds to open or close channel

Question 26

How does the enzyme receptor work?

Answer 26

ligand binds to receptor enzyme and activates intracellular enzyme (amplifier enzyme) which turns on second messengers and causes response

Question 27

How does the G protein-coupled receptor work?

Answer 27

ligand binds to G protein-coupled receptor and opens ion channel or alters enzyme activity

Question 28

How does the integrin enzyme work?

Answer 28

ligand binds to integrin and alters the cytoskeleton as it is connected via anchor protein

Question 29

The response to a hormone depends on…

Answer 29

receptor type as the same hormone can cause different responses, eg. noradrenaline can cause vasoconstriction and vasodilation

Question 30

Lipophilic hormones (** and **) act primarily on _______ receptors

Answer 30

steroid and thyroid
intracellular receptors (membrane, cytoplasm, nucleus)