Physiological Homeostasis

Question 1

What is homeostasis?

Answer 1

Dynamic maintenance of physiological variables within a predictable range

Question 2

What is required for the proper functioning of cells?

Answer 2

Correct O2, pH, [CO2], osmolarity, volume of bodily fluids, [glucose]

Question 3

What are the parts of a homeostatic system?

Answer 3

Sensor
Afferent pathway
Integrating centre
Efferent pathway
Effector

Question 4

Where are neuronal integrating centres located?

Answer 4

Brainstem and midbrain; hypothalamus, pons + medulla

Question 5

How does the sympathetic nervous system affect HR and BP?

Answer 5

Via noradrenaline, HR increased, BP increased with vasoconstriction

Question 6

How does the parasympathetic nervous system affect HR and BP?

Answer 6

Via ACh, HR decreased, BP decreased with vasodilation

Question 7

How do endocrine control systems work?

Answer 7

Endocrine glands/tissues secrete hormones, once released into blood stream they act on distal targets by binding to specific receptors.

Question 8

What are the endocrine organs?

Answer 8

Hypothalamus
Pituitary gland
Thyroid/Parathyroid glands
Adrenal cortex + medulla
Pancreas
Gonads

Question 9

What endocrine organs are involved in metabolic control?

Answer 9

Pituitary gland and thyroid/parathyroid gland

Question 10

What are the neuroendocrine organs?

Answer 10

Posterior lobe of pituitary gland and hypothalamus

Question 11

What are the types of hormones?

Answer 11

Peptides
Polypeptides
Glycoproteins
Steroid hormones (derivatives of cholesterol)

Question 12

Give examples of peptide hormones

Answer 12

ADH

Oxytocin

Question 13

Give examples of polypeptide hormones

Answer 13

Growth hormone

Insulin

Question 14

Give examples of glycoprotein hormones

Answer 14

Lutenizing hormone
Follicle stimulating hormone
Thyroid stimulating hormone

Question 15

What hormones are derivatives of tyrosine

Answer 15

Adrenaline/noradrenaline (epinephrine/norepinephrine)

Thyroxine

Question 16

Give some examples of steroid hormones produced in adrenal cortex - which intermediate are they formed from?

Answer 16

Glucocorticoids
Mineralocortacoids
from pregnenalone (from cholesterol)

Question 17

Give some examples of steroid hormones produced in testes - which intermediate are they formed from?

Answer 17

Androgens (such as testosterone)
from pregnanolone (from cholesterol)

Question 18

Give some examples of steroid hormones produced in ovaries - which intermediate are they formed from?

Answer 18

Progesterone + estrogens
from pregnanolone (from cholesterol)

Question 19

How does the type of hormone affect the type of receptor, its location and its mechanism of action?

Answer 19

Hydrophilic hormones (peptides, proteins, glycoproteins + catecholamines) influence receptors on the plasma membrane (usually GPCRs) with a mechanism of action being via secondary messengers
Hydrophobic hormones (steroids and thyroid hormones) influence intracellular receptors, with a mechanism of action altering gene transcription

Question 20

How is blood flow managed homeostatically via a negative feedback system?

Answer 20

Muscles working, increased pCO2, lactic acid, sensed by arterioles supplying muscle, arterioles dilate, increased O2 uptake and CO2 removal

Question 21

How is blood volume managed homeostatically via a negative feedback system?

Answer 21

increased plasma vol, macula densa senses increased renal filtration, juxtaglomerular cells secrete less renin (decreased production of ATII), less aldosterone, decreases plasma vol

Question 22

Give examples of feed forward mechanisms

Answer 22

Anticipation of food

Fight/flight

Question 23

Where is positive feedback important?

Answer 23

In childbirth