Homeostasis Flashcards
What is the pathway an impulse takes through the nervous system?
stimulus –> receptors –> sensory neuron –> central nervous system –> motor neuron –> effectors –> response
How are nerve cells adapted to carry electrical impulses around the body?
- They are long to cover more distance
- They end in branches to make connections with other neurons
How does an impulse cross a synapse?
When the impulse reaches the end of a neuron, it triggers the release of neurotransmitters which diffuse across the synapse to the next neuron, creating an impulse
What is a reflex?
A fast, unconscious response to certain stimuli so that we don’t get injured
What is the reflex arc?
stimulus –> receptors –> sensory neuron –> relay neuron –> motor neuron –> effectors –> response
What is affected by the cerebral cortex?
Memory, consciousness, intelligence, language
What is affected by the hypothalamus?
Regulation of body temperature, sends signals to the pituitary gland
What is affected by the cerebellum?
Balance, muscle coordination
What is affected by the medulla?
Unconscious activities - breathing, heartbeat
How does an MRI work?
With magnetic fields and microwaves to produce an image of the brain’s structure
What can you do to see what part of the brain does something?
Stimulate the tissue with an electrical impulse
How does the eye adapt to bright light?
The circular muscle contracts, the radial muscles relax and this causes the pupil to constrict
How does the eye adapt to dim light?
The circular muscles relax, the radial muscles contract and this causes the pupil to dilate
How does the eye focus on a near object?
The ciliary muscles contract, the suspensory ligaments slacken, the lens thickens and strongly refracts the light
How does the eye focus on a distant object?
The ciliary muscles relax, the suspensory ligaments pull tight, the lens thins and weakly refracts the light
What is myopia and how is it fixed?
Short sightedness where the light is focused in front of the retina. It can be fixed with concave glasses
What is hyperopia and how is it fixed?
Long sightedness where the light is focused behind the retina. It can be fixed with convex glasses
Pros and cons of contact lenses
Pros:
- easy to acquire
- no surgery
Cons:
- expensive overtime
- soft lenses have a risk of infection
- sometimes uncomfortable to put in
Pros and cons of laser eye surgery
Pros:
- permanent fix
- less invasive than replacement lens surgery
Cons:
- expensive
- surgery is always risky
Pros and cons of replacement lens surgery
Pros:
- permanent fix
- can fix multiple conditions
Cons:
- expensive
- surgery is always risky
- more invasive surgery
What is a hormone?
Chemical messages made of protein that travel through the blood to a target organ
What hormones are produced in the pituitary gland and what do they do?
ADH - controls water concentration of the blood
FSH - causes an egg to mature in the ovaries
LH - causes an egg to be released
TSH - controls thyroxine levels
What hormones do the ovaries produce and what do they do?
Oestrogen - controls puberty in females and causes the uterus lining to thicken
Progesterone - maintains the lining of the womb during the menstrual cycle
What hormone do the testes produce and what does it do?
Testosterone - controls puberty in males
What hormones does the pancreas produce and what do they do?
Insulin - decreases blood sugar levels
Glucagon - increases blood sugar levels
What hormone does the thyroid produce and what does it do?
Thyroxine - regulates the rate of metabolism/growth
What hormone does the adrenal gland produce and what does it do?
Adrenaline - prepares the body for ‘fight or flight’
Compare the endocrine and nervous system
The endocrine system uses chemical hormones that travel through the blood that are slower acting but with longer lasting effects
The nervous system uses electrical impulses that travel along neurons and are faster acting but with shorter lasting effects
What can happen if body temperature is too low?
Vasoconstriction - blood vessels constrict and less blood flows near the skin’s surface meaning less heat is lots
Shivering - skeletal muscles rapidly contract and relax which releases heat by respiration
Goosebumps - hair on our body rises which traps a layer of heat
What can happen if body temperature is too high?
Vasodilation - blood vessels dilate meaning more blood flows near the skin’s surface so more heat is lost
Sweating - as the sweat evaporates, heat energy is taken away from the skin
Hair on our body lies flat so no heat is trapped
What happens is blood glucose levels are too high?
The pancreas secretes insulin which moves glucose from the blood into liver and muscle cells where it’s stored as glycogen
What happens is blood glucose levels are too low?
The pancreas secretes glucagon which breaks down glycogen in liver and muscle cells into glucose which is released into the blood
What is type 1 diabetes and how can it be controlled?
When insulin is no longer produced. Can be controlled by injecting insulin and having a carbohydrate monitored diet
What is type 2 diabetes and how can it be controlled?
When body cells no longer respond to insulin. Can be controlled by a carbohydrate monitored diet
What is the hormonal process of the menstrual cycle?
1) The pituitary gland releases FSH
2) FSH stimulates egg maturation and oestrogen release from the ovaries
3) Oestrogen causes the uterus lining to thicken
4) Oestrogen inhibits FSH release and stimulates LH release
5) The pituitary gland releases LH
6) LH stimulates ovulation and inhibits oestrogen
7) Progesterone is released from the ovaries to maintain the lining of the uterus
8) The egg is unfertilised - menstruation occurs and the cycle starts again
What are non-hormonal methods of contraception?
Condoms, a diaphragm, spermicides
What are hormonal methods of contraception?
Contraceptive pill, implant, intrauterine device, ring, sterilisation
What is the process of IVF?
1) The mother is given FSH and LH to stimulate the maturation of several eggs
2) The eggs are collected and fertilised by the sperm of the father in a lab
3) The fertilised eggs develop into embryos
4) One or two embryos are implanted into the mother’s uterus
5) The embryo implants into the uterus wall and develops into a foetus
Pros and cons of IVF
Pros:
- allows infertile couples to have a baby
- sperm or egg donors can be used for same sex couples
- surrogates can be used if the mother is unable to become pregnant
Cons:
- it doesn’t always work
- it can lead to complications
- it’s very expensive
What is the process of the kidneys filtering blood?
1) Each kidney contains millions of nephrons which consist of a tubule intertwined with a blood vessel
2) The tubule absorbs anything small from the blood vessel - water, glucose, ions and urea
3) During selective reabsorption, all of the glucose from the tubule is reabsorbed back into the blood as well as some water and ions depending on the blood’s water concentration level at the time
4) All of the urea and remaining water and ions becomes urine and travels to the bladder to be excreted
What happens if the blood’s water concentration level is too low?
The pituitary gland releases ADH which travels to the kidneys and causes more water to be reabsorbed
What happens if the blood’s water concentration level is too high?
The pituitary gland stops the release of ADH and less water is reabsorbed
What are some problems with dialysis?
- Time consuming
- Expensive
- Unpleasant
- Higher risk of infection/blood clots
Pros and cons of a kidney transplant
Pros:
- permanent solution
- not time consuming
- less expensive
Cons:
- chance of rejection
- need to take immunosuppressants
- chance of infection after surgery
- kidney shortage
What happens if thyroxine levels fall?
The pituitary gland releases TSH which increases the amount of thyroxine released
What happens if thyroxine levels rise?
The pituitary gland stops releasing TSH which decreases the amount of thyroxine released
How does adrenaline get the body ready for ‘fight or flight’?
Increasing the amount of oxygen and glucose to the brain and muscles. It does this by increasing the heart rate
What is positive geotropism useful for
Anchorage, absorbing water and ions
What is ethene used for in the food industry?
To control the ripening of fruit during storage and transport
What is auxin used for?
Weed killer, rooting powders and promoting growth in tissue cultures
What are gibberellins used for?
Ending plant dormancy, promoting flowering, increasing fruit size
How does auxin work in the shoots of plants?
Auxin moves to the shaded side of the stem and causes elongation on the shaded side, meaning it grows towards the light
How does auxin work in the roots of plants?
Auxin moves to the side of the root that is closest to the earth’s centre of gravity; it inhibits the growth in roots and so causes the roots to grow downwards
