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
describe the structure and function of the eye as a receptor
1) cornea refracts light into the eye
2) iris controls the diameter of the pupil
4) the lens focuses the light on the retina
5) the optic nerve carries impulses from the receptors to the brain
describe the iris reflex
1) bright light: circular muscles contract, radial muscles relax. Pupil gets smaller
2) dim light: circular muscles relax, radial muscles contract. Pupil gets bigger
explain how the eye focuses on near and distant objects
1) near:
ciliary muscles contract, suspensory ligaments slacken.
the lens gets more rounded to refract light more
2) distant:
ciliary muscles relax, suspensory ligaments tighten.
the lens gets more flat to refract light less
describe the role of the skin in temperature regulation
1) sweating: water evaporates, transferring energy from the body to the environment
2) vasodilation: blood vessels close to the surface widen, allowing more blood to flow near the surface, so more heat is lost to surroundings
3) vasoconstriction: opposite of vasodilation
4) hair erector muscles: contract making hairs stand up; traps an insulating layer of air.
what is the source, role and effect of adrenaline
source: adrenal glands
role: readies the body for flight or fight response
effect: increases heart rate, blood flow and blood sugar level
what is the source, role and effect of insulin
source: pancreas
role: control blood sugar level
effect: stimulates liver to turn glucose into glycogen
what is the source, role and effect of testosterone
source: testes
role: main male sex hormone
effect: promotes male secondary sex characteristics
what is the source, role and effect of progesterone
source: ovaries
role: supports pregnancy
effect: maintains lining of uterus
what is the source, role and effect of oestrogen
source: ovaries
role: main female sex hormone
effect: controls the menstrual cycle + promotes female secondary characteristics
ADH
source: pituitary gland
role: controls water content
effect: increases the permeability of the kidney tubules to water
FSH
source: pituitary gland
role: female sex hormone
effect: causes an egg to mature in the ovary + stimulates the ovaries to produce oestrogen
LH
source: pituitary gland
role: female sex hormone
effect: stimulates the release of an egg from an ovary
insulin
source: pancreas
role: control blood sugar levels
effect: stimulates the liver to convert glucose to insoluble glycogen, lowering blood sugar levels
glucagon
source: pancreas
role: control blood sugar levels
effect: stimulates the liver to convert insoluble glycogen to glucose, raising blood sugar levels
conjunctivia
lubricates and protects the eyes surface
sclera
the tough outer layer that protects the eye
cornea
refracts light into the eye. The cornea is transparent and has no blood vessels so oxygen diffuses in and out from the outer surface
iris
controls the diameter of the pupil and therefore how much light enters the eye
lens
focuses the light onto the retina
retina
light sensitive part covered in light receptors (rods-sensitive to to light and cones-sensitive to colour)
fovea
highest concentration of cone cells
optic nerve
carries impulses from receptors to the brain
