excretion; co-ordination and response Flashcards
what are the kidneys main roles
1) remove urea
2) adjust ion levels in blood
3) adjust the water content in blood
describe the structure of the urinary system
renal vein and renal artery connect to kidney; ureter joins kidney with bladder; sphincter muscle then urethra.
describe the structure of a nephron
glomerulus; bowmans capsule; proximal convoluted tubule; loop of henle; distal convoluted tubule; collecting duct.
describe ultrafiltration in the Bowman’s capsule
1) blood from the renal artery flows through the glomerulus (a bundle of capillaries at the start of the nephron
2) a high pressure is built up which squeezes water, urea, ions and glucose out of the blood.
3) the basement membrane is like a filter so stops big molecules like protein and blood cells from being squeezed out
what makes up the glomerular filtrate
urea, water, glucose, ions.
why is glucose reabsorbed in the proximal convoluted tubule
glucose is needed for respiration so it is absorbed by active transport.
describe the role of ADH in regulating the water content of the blood
1) water loss
2) brain detects water loss
3) pituitary gland releases more ADH
4) ADH makes the collecting ducts of the nephrons MORE permeable so more water is reabsorbed into blood
(same in reverse for water gain).
define homeostasis
the maintenance of a constant internal environment.
what does a co-ordinated response require
stimulus, receptor, effector
what is the role of auxin in the phototrophic response of stems
when a shoot is exposed to light, the auxin goes to the dark side. auxin makes the shaded side grow faster so the plant bends towards the light
what are the differences between the nervous and endocrine systems
1) Nerves= very fast messages; hormones = slower messages
2) nerves act for a very short time; hormones for longer
3) nerves act on a very precise area; hormones act in a more general way
what is the central nervous system
the brain and the spine (it is linked to sense organs by nerves
describe how responses to stimuli happen
1) the receptors detect stimuli
2) the sense organ sends electrical impulses along nerves in and out of the central nervous system
3) the effector brings about a response
what is the role of neurotransmitters at synapses
the neurotransmitter transfers the nerve signal by diffusing across the gap and then setting off a new electric signal in the next neurone
describe a simple reflex arc
- stimulus (eg hot object) detected by receptor; impulse sent along a sensory neurone to the CNS.
- the sensory neurone passes the message to the relay neurone . -the relay neurone relays the impulse to a motor neurone.
- the impulse travels along the motor neurone to the effector
- the muscle contracts and pulls hand away from the candle