Coordination and Response 2

What is homeostasis?

the control of internal environment to maintain their internal conditions within narrow limits,

e.g blood glucose concentration, water content of the blood, body temperature

how do hormones travel around the body?

by the blood plasma

what are hormones?

chemical messengers

what are the differences between the nervous system and the endocrine system?

• nervous system has electrical impulses where’s the endocrine system has chemical messengers called hormones

• nervous system travel by neurones endocrine system travels by the blood plasma

• the nervous system is much faster than the endocrine system

• the response to the nervous system is short lived compared to longer lasting endocrine system

• nervous system only affects affectors (muscles or glands) endocrine system only affects ones that have specific receptors

when is adrenaline secreted?

during stressful moments electrical impulses are sent from the brain to adrenal glands which respond by secreting adrenaline to bloodstream

what does muscle require?

energy in the form of ATP so you would need to respire more to supply this

how does liver increase supply of oxygen and glucose to produce more ATP for muscle contraction?

• adrenaline binds to receptors in liver which causes the breakdown of insoluble glycogen to soluble glucose, which diffuses into blood so blood glucose levels rise

how do bronchioles increase level of oxygen so more ATP for muscle contractions?

• adrenaline binds to receptors in muscle cells lining bronchioles which relax causing bronchioles to dilate which means more oxygen is available to muscles

how does heart increase oxygen and glucose levels for more ATP for muscle contractions?

• adrenaline binds to receptors in heart which makes heart muscle contract more frequently and with more force

• this increases the rate of blood flow and blood pressure so more glucose and oxygenate delivered to muscles faster for respiration

how do blood vessels increase oxygen and glucose levels for more ATP for muscle contraction?

• adrenaline binds to receptors in wall of blood vessels supplying muscle cells

• this causes the vessel to dilate increasing blood flow to muscles this is known as vasodilation

• adrenaline also causes some other blood vessels to constrict and narrow known as vasoconstriction diverting blood away from parts of body which are not essential for fight or flight

• this increases blood flow to muscles so more oxygen and glucose for respiration

what is the role of ADH?

makes the walls of the collecting duct more permeable to water so more water is reabsorbed into the blood by osmosis

what would happen to cells if there is too much glucose in the blood?

• water potential of blood will be lowered

• water moves from higher water potential in cells to lower in blood through osmosis

• causing the cells to crenate and shrivel which can damage cells

what happens if too little glucose in the blood?

the water potential of blood will be higher so water moves out of blood by osmosis to cells. this causes cells to lyse. there is also not enough glucose for cells to respire

which hormone is secreted if blood glucose levels are higher than normal?

insulin secreted by the pancreas

which hormone is secreted if blood glucose levels are lower than normal?

glucagon secreted by the pancreas

what happens when blood glucose levels are high?

• pancreas detects this and secretes insulin into the blood

• insulin travels in blood plasma and binds to receptors on its target cells in the liver

• liver cells take up glucose from the blood and store it as insoluble glycogen

• blood glucose levels fall

what happens when blood glucose levels are too low?

• pancreas detects this and secretes glucagon

• glucagon travels in blood plasma and binds to receptors on its target cells in liver

• liver breaks down the stored glycogen to glucose

• glucose diffuses into the blood and levels rise

why do people get type 1 diabetes?

the pancreas cannot produce enough insulin so excess glucose is not stored as glycogen in the liver and muscles and instead remains in the blood. this can be controlled by using insulin injections

why do people get type 2 diabetes?

target cells no longer respond to insulin. people with type 2 need to make lifestyle changes like exercising and controlling intake of carbohydrates

what happens if water content of blood falls below a certain level?

• osmoreceptors in the hypothalamus detects that the water potential of the blood is too low

• they stimulates the pituitary gland to secrete more ADH into blood

• this travels in blood plasma and binds to receptors in collecting duct

• this causes the collecting duct of the nephrons to become more permeable to water so more water is reabsorbed from collecting duct into blood

• the kidneys produce a smaller volume of more concentrated urine

what happens if the water content of the blood rises above a certain level?

• osmoreceptors in the hypothalamus detects water potential is too high

• they stimulates the pituitary the pituitary gland to secrete less ADH into the blood

• so collecting ducts of the nephrons become less permeable to water so less water is reabsorbed into the blood

• the kidneys produce a larger volume of less concentrated urine

what happens if body temperature is too high?

vasodilation occurs:

• during vasodilation the muscle relaxes causing the arterioles wich supply the capillaries near the surface if our skin to dilate

• this allows more blood to flow through the capillaries at the surface of the skin

• so more heat lost by radiation

sweat glands secrete more sweat:

• sweat contains water and salts. when water evaporates it transfers energy from our body to environment, cooling you down

body hairs lie flat:

• erector muscles in the skin relax causing body hairs to lie flat against skin

what happens when body temperature is too low?

Vasoconstriction occurs:

• muscle in the arterie wall contracts causing the arterioles wich supply the capillaries near the surface of our skin to constrict

• this means less blood can flow through the capillaries at the surface of the skin so less heat lost by radiation

Body hairs stand on end:

• erector muscles relax causing hairs to stand on end this hairs traps layer of air which acts as an insulator to prevent heat loss

Shivering:

• shivering means muscles contract automatically and muscles need ATP from respiration to contract, and respiration is exothermic so more heat energy is released

how are animals adapted in relation to heat loss?

• smaller animals have a larger surface area to volume ration so lose heat more rapidly which is good for desert climates

• in cold climates animals have compact shapes with small ears to keep their surface area to a minimum

• kangaroos lick their arms until fur is soaking wet and as water evaporates it helps them increase heat loss

how does surface area to volume ratio affect heat loss?

the large the ratio the more heat loss