Homeostasis And Hormones

Question 1

What is homeostasis

Answer 1

The tendency towards a relatively stable equilibrium between independent elements

Question 2

Outline the general path/response to an increase in homeostatic stimulus

Answer 2

Increase in stimulus
Receptors detect change
Control centre compares change to set pint and signals effectors
Effectors - organs and/or tissues respond (localised or throughout the body)
Homeostasis restored by decreasing variable

Question 3

Outline the general path/response to an decrease in homeostatic stimulus

Answer 3

Decrease in stimulus
Receptors detect change
Control centre compares change to set pint and signals effectors
Effectors - organs and/or tissues respond (localised or throughout the body)
Homeostasis restored by increasing variable

Question 4

Does homeostasis remain perfectly constant

Answer 4

No. Homeostasis in dynamic. It is generally maintained within “normal” levels, with various bodily responses to return non normal levels to normal

Question 5

Outline the normal range within individuals

Answer 5

each individual will have a normal range within which their levels of a given variable fluctuate

Question 6

Outline the population reference range

Answer 6

The population has a reference range based on the breadth of individual normal ranges within the population

Question 7

How do the population reference and individual ranges compare

Answer 7

The population reference tends to be wider than normal fluctuations within an individual
Each individuals normal range in more narrow than the population range

Question 8

What happens when moving outside the normal range of an individual

Answer 8

Moving outside an individuals normal range may lead to symptoms of a disorder, even when hormone levels are within the population reference range

Question 9

Where do most individuals have a set point

Answer 9

Most individuals have a set pint that is within the population reference range

Question 10

Summarise synaptic transmission

Answer 10

Action potentials in axons and neurotransmitter release at synapse
Targeting achieved using specific wiring
Fastest transmission speed, minimising delays
Good for brief responses

Question 11

Summarise the endocrine system

Answer 11

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

Question 12

Compare the transmission, chemical signals and distribution effects of the endocrine system vs synaptic communication

Answer 12

Endocrine system - transmission through blood stream, chemical signals hormones, distribution effects target cells in distant tissues and organs (must have appropriate receptors
Synaptic communication - transmission across synapses, chemical signals neurotransmitters, distribution effects limited to specific areas, target cells must have appropriate receptors

Question 13

What are the major endocrine glads (covered in hubs 191)
HPTAPP

Answer 13

Hypothalamus
Pituitary gland
Thyroid gland
Adrenal glands
Pancreas
Parathyroid glands

Question 14

What is the function of the hypothalamus

Answer 14

Links the nervous system to the endocrine system and controls the secretions of many endocrine glands

Question 15

Which physiological variables are maintain homeostatically through hormones (in hubs 191)
BGBB

Answer 15

Blood sugar concentration
Growth and repair
Basal metabolic rate
Blood calcium concentration

Question 16

What are hormones

Answer 16

Chemical messengers produced in one location and transported via the bloodstream to a second location (target cells) where they cause response in those cells

Question 17

What is required on/in the cell for the hormon to be able to have an effect

Answer 17

Receptors - proteins that are in the target cell membrane or inside the cell itself

Question 18

Outline the chemical classification, storage, and transport of water soluble hormones

Answer 18

Chemical classification - mostly peptides (75% hormones). Some catecholamines
Storage - made and stored until required (released by exocytosis)
Transport - Travel dissolved in blood

Question 19

Outline the chemical classification, storage, and transport of lipid soluble hormones

Answer 19

Chemical classification - steroids, thyroid hormones
Storage - steroids are made from cholesterol as required (not stored). Thyroid hormones are made in thyroid cells and stored until required
Transport - travel in the blood bound to a carrier protein

Question 20

Where are hormone receptors located for water soluble hormones

Answer 20

Water soluble hormones (peptides, catecholamines) cannot cross cell membrane (lipid bilayer is hydrophobic)
Receptors are located in the target cell plasma membrane

Question 21

Where are the hormone receptors for lipid soluble hormones located

Answer 21

Lipid soluble hormones can diffuse across the cell membrane and into the target cell
Receptors are located in the cytoplasm or nucleus

Question 22

Outline cellular response to water soluble hormone receptor activation

Answer 22

Water soluble hormone binds receptor on cell surface
Hormone binds allowing activation of associated G protein (inside cell)
G protein activates/inhibits second messenger production/reduction
Downstream proteins/pathways are activated or deactivated

Question 23

Outline cellular response to lipid soluble hormone receptor activation

Answer 23

Lipid soluble hormone dissociates form carrier protein
Hormone diffuses across cell membrane
Hormone binds to intracellular receptor
Hormone receptor complex act as a specific transcription factor
Target gene is activated
New mRNA is generated
New protein is generated by translation of mRNA
New protein mediates cell specific responses (slow process)

Question 24

Outline the receptors, mechanism of action, and speed of response for water soluble hormones

Answer 24

Receptors - cell surface
Mechanism of action - through 2nd messengers
Speed of response - milliseconds to minutes

Question 25

Outline the receptors, mechanism of action, and speed of response for lipid soluble hormones

Answer 25

Receptors - intracellular receptors in cytoplasm
Mechanism of action - by altering gene transcription
Speed of response - hours to days

Question 26

Outline positive and negative feed back loops

Answer 26

Negative feedback - reduce change until stimulus is removed or directly inhibit further release
Positive feedback - amplification of change until a desired outcome is achieved

Question 27

What controls amount of hormone in blood

Answer 27

Rate of hormone secretion
Rate of hormone removal from blood

Removal controlled by enzymes in blood or in target cells

Question 28

Outline a negative feedback loop

Answer 28

Deviation occurs, detected by receptor, recognised by control centre
Mechanism is activated to bring variable back to set point
In long term, secretion rates of many hormones are maintain at a fairly constant level by negative feedback