Physiological Homeostasis Flashcards
What is homeostasis?
Dynamic maintenance of physiological variables within a predictable range
What is required for the proper functioning of cells?
Correct O2, pH, [CO2], osmolarity, volume of bodily fluids, [glucose]
What are the parts of a homeostatic system?
Sensor Afferent pathway Integrating centre Efferent pathway Effector
Where are neuronal integrating centres located?
Brainstem and midbrain; hypothalamus, pons + medulla
How does the sympathetic nervous system affect HR and BP?
Via noradrenaline, HR increased, BP increased with vasoconstriction
How does the parasympathetic nervous system affect HR and BP?
Via ACh, HR decreased, BP decreased with vasodilation
How do endocrine control systems work?
Endocrine glands/tissues secrete hormones, once released into blood stream they act on distal targets by binding to specific receptors.
What are the endocrine organs?
Hypothalamus Pituitary gland Thyroid/Parathyroid glands Adrenal cortex + medulla Pancreas Gonads
What endocrine organs are involved in metabolic control?
Pituitary gland and thyroid/parathyroid gland
What are the neuroendocrine organs?
Posterior lobe of pituitary gland and hypothalamus
What are the types of hormones?
Peptides
Polypeptides
Glycoproteins
Steroid hormones (derivatives of cholesterol)
Give examples of peptide hormones
ADH
Oxytocin
Give examples of polypeptide hormones
Growth hormone
Insulin
Give examples of glycoprotein hormones
Lutenizing hormone
Follicle stimulating hormone
Thyroid stimulating hormone
What hormones are derivatives of tyrosine
Adrenaline/noradrenaline (epinephrine/norepinephrine)
Thyroxine
Give some examples of steroid hormones produced in adrenal cortex - which intermediate are they formed from?
Glucocorticoids
Mineralocortacoids
from pregnenalone (from cholesterol)
Give some examples of steroid hormones produced in testes - which intermediate are they formed from?
Androgens (such as testosterone) from pregnanolone (from cholesterol)
Give some examples of steroid hormones produced in ovaries - which intermediate are they formed from?
Progesterone + estrogens from pregnanolone (from cholesterol)
How does the type of hormone affect the type of receptor, its location and its mechanism of action?
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
How is blood flow managed homeostatically via a negative feedback system?
Muscles working, increased pCO2, lactic acid, sensed by arterioles supplying muscle, arterioles dilate, increased O2 uptake and CO2 removal
How is blood volume managed homeostatically via a negative feedback system?
increased plasma vol, macula densa senses increased renal filtration, juxtaglomerular cells secrete less renin (decreased production of ATII), less aldosterone, decreases plasma vol
Give examples of feed forward mechanisms
Anticipation of food
Fight/flight
Where is positive feedback important?
In childbirth
