Homeostasis and response (2) Flashcards
Describe the function of each part of the eye:
sclera-
iris-
lens-
ciliary muscles-
suspensory ligaments-
optic nerve-
retina-
radial muscles-
circular muscles-
sclera- tough supporting wall of the eye
iris- contracts to control pupil diameter
lens- focuses light on the retina
ciliary muscles- control lens thickness
suspensory ligaments- control lens thickness
optic nerve- carries impulses to the brain
retina- contains light-sensitive receptor cells at the back of the eye
radial muscles- connect pupil to iris
circular muscles- orientated around the pupil
how does the eye accommodate to a brighter environment compared to a dimmer environment
more light- pupil made smaller by circular muscles contracting and radial muscles relaxing
less light- pupil made wider by the reverse
What are myopia and hyperopia and how are they corrected
hyperopia (long-sightedness) - can’t see near objects as the lens doesn’t refract light enough so images are focused behind retina
Fixed with convex lenses
myopia (short-sightedness) - can’t see distant objects as the lens refracts light too much so images are focused before the retina
Fixed with concave lenses
positives and negatives of: contact lenses, laser eye surgery, replacement lens surgery
contact lenses are cheap, non-obstructive and discrete but need to be replaced daily and can become infected
laser eye surgery is a permanent fix but is expensive and a risk as its a new procedure
replacement lens surgery is a permanent fix but is expensive and a risk as its a new procedure and only fixes long-sightedness
how do the eyes accommodate to near and distant objects
near- lens made fatter/more curved by ciliary muscles contracting and suspensory ligaments slackening which refracts light more
distant- lens made thinner/less curved by ciliary muscles relaxing and suspensory ligaments tightening to refract light less
How does the body adapt to temperature being too hot or cold
too hot-
-sweat transfers heat to the surroundings
-blood vessels dilate (vasodilation) so blood flows closer to the surface and thermal energy is lost to the surroundings
-hairs lay flat to prevent insulation of heat,
-no shivering
too cold-
-hairs stand on end
-no sweat
-shivering causes muscles to rapidly contract which requires energy from respiration which releases thermal energy
-blood vessels constrict to minimise energy loss (vasoconstriction)
describe the reflex arc and the function of synapses
receptor- sensory neuron- relay neuron (in the spinal cord) - motor neuron- effector
synapses are the connections between two neurons. The signal is transferred by neurotransmitter chemicals that diffuse across the gap
differences between nerves and hormones
nerves- fast acting, act for a short time, target a precise area, electrical
hormones- slower acting, act for a long period of time, target a general area, chemicals in the bloodstream
The endocrine system:
pituitary gland-
thyroid-
adrenal-
pancreas-
ovaries/testes-
pituitary gland- master gland, lots of hormones (fsh, lh etc)
thyroid- produces thyroxine which controls BMR, heart rate and temperature
adrenal- adrenaline for fight or flight response
pancreas- secretes insulin which controls blood glucose levels
ovaries/testes- produces reproductive hormones and controls puberty
How is blood glucose regulated
Too high after eating- pancreas detects and secretes insulin, excess glucose converted into glycogen for storage in fat liver and muscle cells
Too low after not eating or exercising- pancreas detects and secretes glucagon which converts stored glycogen into glucose for use
compare the cause effects and treatment of type one and two diabetes
1- .caused by genetics
. body can’t produce enough insulin
.treated with insulin injections
2- .caused by poor lifestyle
. caused by cells being resistant to insulin after consistently high glucose levels
. treated by improving lifestyle
how is thyroxine regulated
too low- The hypothalamus detects and releases TSH from the pituitary gland which leads to increased thyroxine secretion from the thyroid gland
too high- The hypothalamus detects and inhibits TSH from the pituitary gland which leads to decreased thyroxine secretion from the thyroid gland
what does adrenaline do for the body
Adrenaline causes blood and oxygen to be drawn to muscles and the brain for sharper decision-making and preparing the body to fight or flee.
It draws blood away from areas like the stomach which is why you feel ‘butterflies’
How do the kidneys filter blood
- blood enters the organ
- all substances (water, ions, glucose) are filtered into the kidney
- all of the glucose and most ions are reabsorbed
- the necessary volume of water is reabsorbed by the tubules
- excess water and waste products like ions and urea are removed from the bladder
- This is known as selective reabsorption
how is water reabsorption controlled
water concentration too low- hypothalamus detects, the pituitary gland secretes more ADH, kidney tubules become more permeable, less water is lost in urine and more is reabsorbed into the blood
water concentration too high- hypothalamus detects, the pituitary gland secretes less ADH, kidney tubules become less permeable, more water is lost in urine and less is reabsorbed into the blood
how is ammonia then urea produced and removed
Excess amino acids are broken down into fats and carbohydrates in the liver by deamination.
Ammonia is a toxic waste product of this
Ammonia is broken down into urea in the liver, then removed in urine
solutions to kidney failure
Dialysis machine-
.blood flows through an external machine between two partially permeable membranes filled with dialysis fluid
.which flows in the opposite direction to the blood to maintain a concentration gradient
.Waste products diffuse out and the correct amount of useful substances are added back into the blood
Transplant- a donor organ of similar genetics replaces the faulty one
positives and negatives of kidney dialysis and transplant
Dialysis:
Positives- buys time before transplant
no risk of rejection, no surgery
Negatives- time-consuming, non-permanent, expensive, risk of blood clots and infections
Transplant:
Positives- permanent fix, no risk of infection or blood clots
Negatives- risk of rejection, long waiting list
Cerebral cortex-
Medulla-
Cerebellum-
Spinal Chord-
Cerebral cortex- Responsible for consciousness, intelligence, memory and language
Medulla- controls unconscious activity
Cerebellum- responsible for muscle coordination
Spinal Chord- connects the brain to the rest of the nervous system
How can the brain be studied
studying patients with brain damage- if a small area is damaged, the effect on the patient can tell us what that part of the brain controls
electrically stimulating brain- pushing a small electrode into the brain tissue and slightly electrifying it can cause the brain to carry out that function
MRI scans- Magnetic Resonance Imaging creates a detailed, live image of the brain, and scientists can observe what parts are active during different tasks
FSH-
LH-
Oestrogen-
Progesterone
FSH- produced in the pituitary gland
causes egg in the ovary to develop
LH- produced in the pituitary gland, stimulates egg release on day 14
Oestrogen- produced in ovaries
causes the uterus lining to thicken
stimulates the release of LH and inhibits FSH
Progesterone- produced in the ovaries by the remains of the follicle after ovulation
It maintains the uterus lining
When progesterone levels fall, the lining breaks down and menstruation occurs
It inhibits the release of LH and FSH
Menstrual cycle:
day 1-5
day 5-14
day 14
day14-28
day 1-5: FSH produced by the pituitary gland, eggs start to grow in the ovaries
day 5-14: Oestrogen is produced by the ovaries which inhibits FSH and starts the buildup of the uterus lining, stimulating LH production
day 14: LH is produced by the pituitary gland, causing ovulation
day 14-28: Progesterone produced by empty egg follicle in the ovaries, maintains the uterus lining incase the egg is fertilised
If it isn’t, progesterone levels fall so lining breaks down and menstruation occurs
Describe the ruler drop test RP and a computer reaction time test
Ruler:
The person needs to be sat down with their arm resting on the table
hold a ruler vertically between the top of their thumb and forefinger
let go randomly
use a conversion chart to turn the ruler distance into a reaction time
drink a caffeinated drink, wait ten minutes then repeat
Computer:
click the mouse as fast as possible when prompted
far more accurate (higher resolution) and reliable as there is no chance of human error
removes the ability to predict the ruler drop
Controlling fertility:
Pill-
IUD-
Barrier methods-
Spermicide-
Sterilisation-
Natural method-
Pill- Contains oestrogen (prevents ovulation by inhibiting FSH) and progesterone ( produces thick mucus that stops gamete fusion)
IUD- t-shaped device in the uterus that kills sperm on contact
Barrier methods- condoms and diaphragms (also prevent STIs)
Spermicide- a substance that kills sperm
Sterilisation- a permanent procedure, either cutting fallopian tubes or sperm duct
Natural method- not having sex when an egg is in the uterus
