Topic 5 - Homeostatis and response Flashcards
Define homeostatis
The maintenance of internal conditions such as water, sugar, temperature and ion levels
Define a stimulus
something that changes in the environment
Define receptor
the thing that detects the change
Define co-ordinator
the part of the body that processes the change
Define effector
what causes the change (muscles or glands)
Define response
what happens to the body
What are the 2 parts of the central nervous system?
- brain
- spinal cord
Define a synapse
A gap between 2 neurones across which chemical signals pass.
What does SRSRMER stand for?
stimulus - receptor - sensory neuron - relay neuron - motor neuron - effector - response
Define a reaction time
the time taken to react to a stimulus
Define the suspensory ligaments (in the eye)
tough fibres that hold the lens in place
Define the iris
muscles that contract or relax to change the shape of the pupil - the coloured part of the eye
Define the sclera
tough protective layer - the white of the eye
Define the retina
layer containing light sensitive cells which send electrical impulses to the brain when stimulated by light
Define the optic nerve
a bundle of nerve fibres that sends electrical impulses to the brain
Define the cornea
transparent area at the front of the eye which allows light into the eye - it refracts light to direct it into the eye
Define ciliary muscles
muscles that contract or relax to change the shape of the lens to focus the light
What does the eye do to focus on a nearby object?
- ciliary muscles contract
- suspensory ligaments slacken
- the lens becomes rounder
What does the eye do to focus on a distant object?
- ciliary muscles relax
- suspensory ligaments tighten
- the lens becomes flatter
What does myopia mean?
short sight - can see near objects clearly and distant objects are blurred - the far point is too close
What does hyperopia mean?
long sight - can see distant objects clearly and close objects are blurred - the near point is too far
Why are people myopic?
their eyeball is longer than usual or their lens is too curved so the focus point is in front of the retina
Why are people hyperopic?
their eyeball is shorter than usual or their lens is too thin/flat so the focus point is behind the retina
What does the convex lens do?
causes the light rays to converge (go together)
What does the concave lens do?
cause the light rays to diverge (go apart)
What type of lens do myopic people need?
concave
What type of lens do hyperopic people need?
convex
What does the eye do in bright light?
- circular muscles contract
- radial muscles relax
- pupil constricts (gets smaller)
What does the eye do in dim light?
- circular muscles relax
- radial muscles contract
- pupil dilates (gets bigger)
What is the role of the cerebral cortex?
it’s responsible for things like consciousness, intelligence, memory and language
What is the role of the medulla?
it controls unconscious activities like breathing and your heartbeat
What is the role of the cerebellum?
it’s responsible for muscle coordination
What are the 3 methods of brain study?
- studying patients with brain damage
- electrically stimulating the brain
- MRI scans
What are radial muscles in the eye?
go from centre to outside - straight lines
What are circular muscles in the eye?
go around the pupil in a circle
Name some treatments for vision defects
- contact lenses/glasses
- laser eye surgery changes the shape of the cornea so it will refract light differently
Describe the 2 body responses when you’re too hot
- sweating - the heat is transferred from the body to liquid and evaporates
- vasodilation - blood vessels widen so they are closer to the surface so more heat is lost through the skin
Describe the 3 body responses when you’re too cold
- shivering - muscles contract which means more respiration which releases energy which releases heat
- goosebumps - little hairs stand up and trap a layer of air for insulation
- vasoconstriction - blood vessels get narrower and further from surface so less heat is lost through skin
What happens in the thermoregulatory centre?
It is the place where temperature is monitored - it receives info from receptors in the skin and triggers the effectors
Why would it be dangerous if all the glucose you absorbed stayed in the blood?
- it would cause water to move out of the cells by osmosis
- the body has to take glucose out of the blood for respiration
Define glucose
it’s sugar used in respiration (to release energy)
Define glycogen
it’s a carbohydrate - it’s a storage system in the liver made out of glucose
Define insulin
a hormone that tells your body to change glucose into glycogen - it’s made in the pancreas
Define glucagon
a hormone that tells your body to change glycogen into glucose - it’s made in the pancreas
What happens when your blood sugar levels are too high?
- insulin is secreted by the pancreas
- the liver converts glucose into glycogen
- levels drop
What happens when your blood sugar levels are too low?
- glucagon is secreted by the pancreas
- the liver converts glycogen into glucose, and releases it into the blood
- levels rise
Name the 6 glands in the endocrine system
- pituitary
- thyroid
- adrenal
- pancreas
- ovaries
- testes
What hormone does the thyroid gland produce?
thyroxine
What hormone do the adrenal glands produce?
adrenaline
What hormone do the testes produce?
testosterone
Which gland is the master gland?
the pituitary gland
What’s the difference between hormones and nerves?
- nerves act quickly for a short amount of time in a specific area
- hormones act slowly for a long time in a more general area
How does type 1 diabetes occur?
the body produces little/ no insulin - this leads to a high blood glucose level
How is type 1 diabetes controlled/ treated?
- regular insulin injections
- regular monitoring of blood sugar levels
How does type 2 diabetes occur?
when the body doesn’t respond to the insulin produced - linked to obesity
How is type 2 diabetes controlled/ treated?
control diet and regular exercise
Name the 3 stages in the kidney
- filtration
- selective reabsorbtion
- excretion
Describe the stages of what happens in your kidney
- excess amino acids are converted to ammonia then to urea
- blood flows into the kidney
- small substances are filtered out of the blood
- useful molecules (all glucose and some mineral ions) are absorbed back into the blood by diffusion and active transport
- blood flows away
- waste substances (urea) continue out of the nephron, into the collecting duct and to the bladder
Describe what your body does when you have too much water in your blood
- there is a lower concentration of solutes in blood
- so less ADH is released by the pituitary gland
- kidney tubule wall becomes less permeable so less water is reabsorbed (more dilute urine)
Describe what your body does when you have too little water in your blood
- there is a higher concentration of solutes in blood
- so more ADH is released by the pituitary gland
- kidney tubule wall becomes more permeable so more water is reabsorbed
Describe how dialysis machines work
- blood is taken from an artery in the arm
- blood flows between partially permeable membranes, surrounded by dialysis fluid - removes waste substances and excess water/ions
- clean blood flows through bubble trap to remove any bubbles
- blood returns to a vein in the arm
Describe the substances in dialysis fluid and their concentrations
- low in salt and urea (so salt and urea diffuse out of the blood to the lower concentration)
- sugar and mineral concentration is same as blood (no movement)
Name some advantages of dialysis
- more readily available than transplant
- no risk of rejection
- no need for immunosuppressant drugs
Name some disadvantages of dialysis
- time consuming
- expensive
- will have to use for the rest of your life
- can cause infections or blood clots
Name some advantages of a kidney transplant
- cheaper than dialysis
- long term solution
- can lead a normal life
Name some disadvantages of a kidney transplant
- risk of rejection (medication doesn’t always work)
- only lasts 9 years
What are the roles of FSH?
- causes egg to mature in follicles
- stimulates ovaries to produce oestrogen
What are the roles of oestrogen?
- builds up the lining of the uterus
- stops FSH being produced
- stimulates production of LH
What are the roles of LH?
- stimulates the release of a mature egg on day 14 (ovulation)
What are the roles of progesterone?
- stops the release of LH
- stops the release of FSH
- maintains the lining of the uterus
Describe the hormones in the menstrual cycle
- FSH released - egg matures and stimulates oestrogen
- oestrogen released - thickens womb lining, turns off FSH and turns on LH
- LH released - causes ovulation
- progesterone released - maintains womb lining, turns off both FSH and LH
Where are the 4 hormones involved in the menstrual cycle produced?
FSH - pituitary gland
oestrogen - ovaries
LH - pituitary gland
progesterone - ovaries
Describe oral contraceptives
pills with oestrogen (to stop FSH production so no eggs can mature) and progesterone (which stops ovaries releasing eggs)
Describe IUDs
a T-shaped device inserted into uterus
- plastic ones release progesterone
- copper ones prevent sperm surviving in the uterus
Describe abstaining
not having intercourse
Describe sterilisation (contraception method)
cutting the fallopian tubes or the sperm duct - permanent
Describe a barrier method
stops the sperm and egg meeting (condoms, diaphragm etc.)
Give some advantages and disadvantages of the contraceptive pill
+ 99% effective
- side effects - headaches, nausea etc.
- doesn’t prevent STDs
Describe hormones given to increase fertility and give some pros and cons
FSH + LH are given to women to stimulate ovulation
+ helps pregnancy
- doesn’t always work
- multiple pregnancies could occur
Describe IVF
- women are given FSH + LH to stimulate several eggs to mature
- eggs are collected and fertilised with sperm in a lab
- fertilised eggs are grown into embryos
- embryos are transferred into woman’s uterus
Give some advantages and disadvantages of IVF
+ helps pregnancy
- success rate is low
- higher risk of multiple births
- emotionally + physically stressful
Describe adrenaline
- released by the adrenal glands
- released in response to stressful/scary situations
- increases the oxygen and glucose supply to cells
- increases heart rate
Describe how negative feedback works in the body
- conditions change from set point
- change detected
- corrective mechanisms activated
- conditions return to set point
- corrective mechanisms switched off
Describe thyroxine
- released by the thyroid gland
- it controls the metabolic rate of your body and is important in growth and development
- it is released in response to TSH - a negative feedback system
What is auxin and what does it do in the roots and in the shoots?
- auxin is a plant hormone that controls growth
- in shoots, it speeds up growth
- in roots, it reduces growth
Define tropism
a plant growing in response to a stimulus - movement towards stimuli is positive tropism and away is negative tropism
Why does a shoot tip grow towards light?
- the auxin moves to the shaded area
- the auxin speeds up growth in the shaded side
- so the plant grows towards the light
Describe how a shoot grows in response to gravity
- auxin is pulled downwards by gravity
- the auxin speeds up growth on the lower side
- this cause shoot to curve upwards
Describe how a root grows in response to gravity
- auxin is pulled downwards by gravity
- the auxin reduces growth on the lower side
- this causes the root to curve downwards
Describe the 3 human uses of auxins
- killing weeds - it disrupts their growth cycle + kills them
- rooting powder - auxins in rooting powder cause cuttings to produce roots rapidly and grow as a plant
- tissue culture - auxin promotes growth so cells can divide and clone
Describe 3 human uses of gibberellin
- ending dormancy - gibberellin alters dormancy so seeds germinate at times of the year they wouldn’t usually
- growing larger fruit - helps seedless varieties grow larger to match the normal types
- induce flowering - plants can flower without their usually required condition - also grows larger flowers
Describe 1 human use of ethene
- fruit can be picked when unripe and ethene (gas) is added to them to ripen on the way to shops
Describe the plant growth responses RPA
- put 10 cress seeds into 3 petri dishes, lined with moist cotton wool
- shine a light on each dish, each going in different directions
- leave them for a week and the shoots will have grown towards the light
