Hormonal control Flashcards
homeostasis
the maintenance of a stable equilibrium in the conditions inside the body within a narrow limit
three key homeostatic mechanisms
- thermoregulation
- osmoregulation
- control of blood glucose concentration
hormone
a chemical messenger produced by an endocrine gland that travels around the body in the bloodstream
endocrine gland
a group of cells that secrete hormones directly into the bloodstream
endocrine vs nervous system (3)
endocrine - slower, long-term, widespread
nervous - immediate, short-term, localised
what stimulates hormones to be produced? (3)
- other hormones
- nerve impulse
- change in concentration of a specific substance
how do hormones reach target organs?
- hormones are secreted directly into the blood plasma
- hormones diffuse out of blood plasma and bind to specific complementary receptors in the plasma membranes of target cells (binding site)
steroid hormones
- lipid soluble, pass through the phospholipid bilayer
- hormone binds to receptors in the cytoplasm or the nucleus
- hormone-receptor complexes act as transcription factors
- example: oestrogen
non-steroid hormones
- hydrophilic, cannot pass through the phospholipid bilayer
- hormone binds to receptors in the plasma membrane
- triggers a cascade reaction executed by second messengers
- example: adrenaline
first messenger
the hormone secreted by an endocrine gland that signals the target cells
second messenger
the molecule that triggers the effect by causing a cascade reaction (cAMP in the response to adrenaline)
adrenal glands location
above the kidneys
adrenal gland structure and hormones
adrenal cortex - cortisol, corticosterone aldosterone and small amounts of oestrogen and testosterone (hormones are vital to life)
medulla - adrenaline, noradrenaline (non-essential hormones)
cortisol function (1)
primary stress hormone regulates metabolism of glucose, proteins and fats to release usable energy
corticosterone function (2)
- regulate the immune response
- suppress inflammatory reactions
aldosterone function (1)
regulates levels of Na and K salts and the water balance in the blood (to maintain blood volume and pressure)
adrenaline function (2)
- increases heart rate to transport more blood to the brain and muscles
- increase blood glucose concentrations by converting glycogen to glucose in the liver
noradrenaline function (4)
- increases heart rate
- widens pupils
- widens air passages in lungs
- vasoconstriction of blood vessels in non-essential organs (increases blood pressure)
exocrine function of the pancreas
- produce pancreatic juice containing digestive enzymes
- delivered to small intestine
endocrine function of the pancreas
Islets of Langerhan:
- alpha cells secrete glucagon
- beta cells secrete insulin
ABBA pneumonic
ABBA
Alpha
Below (low [glucose], secrete glucagon)
Beta
Above (high [glucose], secrete insulin)
Three ways in which glucose can enter the bloodstream:
- absorption in gut (from carb digestion)
- glycogenolysis (hydrolysis of glycogen)
- gluconeogenesis (convert lipids/lactate/amino acids into glucose)
consequences of low blood glucose concentration
cells don’t have enough glucose for respiration so don’t function properly
consequences of high blood glucose concentration
high blood pressure
(glucose lowers water potential in blood, water moves out of cells and into bloodstream)
