Homeostasis

Question 1

What is homeostasis?

Answer 1

The optimal conditions for a species which is maintained however there are levels within which can fluctuate

Question 2

What is synaptic intracellular communication?

Answer 2

Action potentials in axons and neurotransmitter release at synapse
- Targeting achieved by specific wiring
- Fastest transmission speed, to minimise response delays

Question 3

What is endocrine intracellular communication?

Answer 3

Hormones are released into the blood
- Targeting by presence of specific receptors on target cells
- Relatively slow, but long lasting action
- Good for widespread and sustained responses

Question 4

What does the endocrine system consist of?

Answer 4

Endocrine gland cells that secrete hormones which are carried in the bloodstream to the target cells upon which they act

Question 5

What are the major endocrine glands?

Answer 5

Hypothalamus, pituitary gland, thyroid gland, adrenal glands, pancreas, parathyroid glands

Question 6

What links the endocrine and nervous system

Answer 6

The hypothalamus links the endocrine system to the nervous system and controls the secretion of any endocrine glands

Question 7

What are hormones?

Answer 7

Messengers produced in one location and transported via the bloodstream to a second location where they cause a response in those cells

Question 8

What is a specific receptor?

Answer 8

A hormone that can only affect cells with specific receptors for that hormone. Each receptor is a protein. It can be in the target cell membrane or inside the target cell

Question 9

Chemical classification of water soluble hormones

Answer 9

Mostly peptides (75% of hormones)

Question 10

Chemical classification of lipid soluble hormones

Answer 10

Steroids and thyroid hormones

Question 11

Storage of water soluble hormones

Answer 11

Made and stored until required, released by exocytosis

Question 12

Storage of lipid soluble hormones

Answer 12

Steroids are made from cholesterol as required (not stored)
Thyroid hormones are made in thyroid cells and stored until required (this storage is unusual for lipid-soluble hormones)

Question 13

Transport of water soluble hormones

Answer 13

Travel dissolved in the blood

Question 14

Transport of lipid soluble hormones

Answer 14

Travel in the blood bound to a carrier protein

Question 15

Where are the hormone receptors located?

Answer 15

Water soluble hormones: cannot cross cell membrane, receptors are located on the target cell/plasma membrane
Lipid soluble hormones: can diffuse across the cell membrane into the target cell, receptors are located in cytoplasm or nucleus

Question 16

Cellular response to receptor activation: water soluble hormones

Answer 16

Water soluble hormone binds to cell surface receptor
Hormone binding allows activation of associated of G-protein
G-protein activates/inhibits second messenger production/reduction
Downstream proteins/pathways are activated or deactivated

Question 17

Lipid soluble hormones: steroid and thyroid hormones through a membrane

Answer 17

Lipid soluble hormone dissociates from carrier protein -> hormone diffuses across membrane and binds to intracellular receptor which acts as a specific transcription factor -> target gene is activated and new mRNA is generated -> new protein is generated by translation of mRNA

Question 18

Water soluble hormone receptors

Answer 18

Cell surface

Question 19

Where are water soluble hormones mechanisms of action

Answer 19

Through 2nd messengers

Question 20

How long is water soluble hormones speed of response?

Answer 20

Milliseconds to minutes

Question 21

Where are lipid soluble hormones mechanisms of action?

Answer 21

Intracellular receptors in cytoplasm or nucleus

Question 22

How long is the speed of response for lipid soluble hormones?

Answer 22

Hours to days

Question 23

What is negative feedback?

Answer 23

Process of reducing a change until stimulus is removed or directly inhibiting further release of a hormone

Question 24

What is positive feedback?

Answer 24

Amplification of change until a desire outcome is achieved

Question 25

What does the amount of hormone in blood depend on?

Answer 25

Amount of hormone in blood depends on rate of hormone secretion and rate of removal from blood

Question 26

Why does blood - glucose concentration need to be controlled?

Answer 26

If too high for too long diabetes develops, if too low hypoglycaemia occurs.
The brain must be supplied with glucose at all times as glucose is the only fuel that the brain uses

Question 27

What is the fed state when referring to metabolic states?

Answer 27

Cellular uptake of nutrients and anabolic metabolism (synthesis of glycogen, protein and fat)

Question 28

What is the fasting state when referring to metabolic states?

Answer 28

Mobilisation of nutrients and catabolic metabolism (breakdown of glycogen, protein and fat)

Question 29

What does insulin and glucagon do?

Answer 29

Increases fuel storage
Peptide hormone that has membrane receptors in or on target cells

Question 30

An increase in blood glucose concentration stimulates what…

Answer 30

Pancreatic islet beta cells to secrete insulin

Question 31

Insulin stimulates what?

Answer 31

Muscle and adipose cells: increase in glucose uptake
Liver cells: glucose output stops increases net glucose uptake, glycogen’s and fat synthesis

Question 32

Muscle, adipose and liver cells decrease what?

Answer 32

Blood glucose concentration which inhibits for increases blood glucose concentration

Question 33

Muscle and adipose cells increase what?

Answer 33

Amino acid uptake, glycogen and protein synthesis
Fat synthesis

Question 34

A decrease in blood glucose concentration results in what

Answer 34

Stimulation of pancreatic islet alpha cells secrete glucagon

Question 35

Glucagon stimulates what in liver cells?

Answer 35

Increase in breakdown of glycogen
Increase in glucose synthesis
Increase ketone synthesis