Homeostasis and Response Flashcards
What is homeostasis
maintaining a stable environment inside your body by regulation of hormone and water levels and more
What happens in a negative feedback loop
Receptor detects a stimulus - level is too high/low
The coordination receives and processes the information then organises a response
effector produces a response which counteracts the change and restores the optimal level
What are the parts that make up the nervous system
CNS
sensory neurones
motor neurones
effectors
What are receptors
cells that detect stimuli
what are effectors
things that respond to nervous impulses and bring about change
What is the order of a response
Stimulus
Receptor
Sensory neurone
CNS
Motor neurone
Effector
Response
what is a synapse
connection between neurones
how do signals pass from nerve to nerve
diffuse across the synapse
new electrical signal in the next neurone
how do reflexes prevent injury
rapid and automatic responses that bypass the conscious part of the brain to prevent damage
what happens on a reflex arc
stimulus
receptor
sensory neurone
relay neurone in cns
motor neurone
effector
response
what does the cerebral cortex do
responsible for consciousness, intelligence, memory and language
what does the medulla do
unconscious activities such as breathing
what does the cerebellum do
muscle coordination, movement and balance
How can scientists study the brain
studying patients with brain damage - can help with treatment and mapping
electrically stimulating the brain - can see which parts are responsible for which bits
MRI scans - can help with seeing which bits are active doing certain things
what are some potential issues with messing with the brain
can cause difficulties such as speech problems
what is the sclera
tough supporting wall of the eye
what is the cornea
the transparent outer layer found at the front of the eye
refracts light into the eye
what is the iris
contains muscles that allow it to control the diameter of the pupil therefore controls how much light enters the eye
what is the lens
focuses the light onto the retina which contains receptor cells sensitive to light and colour
its shape is controlled by the suspensory ligaments and the cilliary muscles
how does the eye change to focus on near objects
ciliary muscles contract
slackens suspensory ligaments
lens becomes more curved
increases the amount that it refracts light
how does the eye change to focus on far objects
ciliary musles relax
pulls suspensory ligaments tight
lens is less curved
refracts light by a smaller amount
what happens when someone has hyperopia
where the image is focused behind the retina
therefore a convex lens is used to correct it and refract the light onto the retina bringing the rays closer together
what happens when someone has myopia
the image is formed in front of the retina
therefore a concave lens is used to spread the rays out
some treatments for vision defects
contact lenses
laser eye surgery - changes shape of cornea
replacement lens surgery - replaces lens
how does the body control temperature
thermoregulatory centre in brain
receptors detect
thermoregulatory centre acts as a control centre
triggers effectors
response counteracts change
what happens when you are too hot
sweat - sweat evaporates from the skin
vasodilation - more blood flows and more energy lost to the surroundings
what happens when you are too cold
hairs stand up - insulating layer of air
no sweat
vasoconstriction - blood vessels constrict to minimise loss on surface
shiver - respiration to transfer some energy to heat the body
what are hormones
chemical molecules that are released directly into the blood but only affect particular cells in particular organs
examples of glands and their functions
pituitary gland - ‘master gland’ - produces hormones that regulate body conditions eg ADH
thyroid - thyroxine which controls metabolism, heart rate and temp
adrenal gland - adrenaline which triggers flight or fight
pancreas - insulin for blood glucose levels
ovaries - oestrogen which is needed in the menstrual cycle
testes - testosterone which controls sperm production
difference between nerves and hormones
nerves:
fast
short operating time
precise area
hormones:
slower
act for a long time
more general area
what is glycogen
what glucose is stored as
what happens if blood glucose level is too high
detected by receptors
insulin secreted by pancreas
insulin makes liver turn glucose into glycogen for storage
moves into muscle and liver cells
what happens if blood glucose level is too low
receptors detect
glucagon is secreted by the pancreas
glucagon makes liver turn glycogen into glucose
moves out of muscle and liver cells into blood
what is type 1 diabetes
where a person’s pancreas produces little to no insulin
they require shots of insulin
what is type 2 diabetes
where a person has become resistant to their own insulin
can be controlled naturally
what things do the kidneys do
filter urea out of the blood
re-absorb the right amount of ions to maintain a healthy balance
re-absorb the right amount of water to maintain a healthy balance
what hormone controls water levels
ADH
what happens if your kidneys don’t work properly
waste substances build up and eventually results in death
treatment for kidney failure
dialysis
kidney transplant
what are the downsides to a kidney transplant
they can be rejected
long waiting lists
how does dialysis work
regular process
partially permeable membrane surrounded by dialysis fluid to replicate kidneys
fluid has same concentration of ions and glucose as healthy blood
only waste substances diffuse across the barrier
long process and can cause blot clots or infections
What do hormones do at puberty
Promote sexual characteristics such as facial hair in men and breasts in women
What are the 4 stages of the menstrual cycle
Menstruation
Uterus lining starts to build up again
Egg develops and is released from the ovary at day 14
The wall is then maintained from days 14-28
What are the 4 hormones involved in the menstrual cycle
1) FSH
produced in pituitary gland
causes an egg to mature in a follicle
stimulates the production of oestrogen
2) Oestrogen
produced in the ovaries
causes the lining of the uterus to grow
stimulates the release of LH and inhibits the release of FSH
3) LH
produced by the pituitary gland
stimulates the release of an egg
4) Progesterone
Produced in the ovaries
Maintains the lining of the uterus
Inhibits the release of LH and FSH
How can hormones be used to reduce fertility
Oestrogen and progesterone
Inhibits egg production and development (oestrogen)
Progesterone reduces fertility by producing more of the thick mucus which prevents any sperm getting through and reaching an egg
Other forms of contraception
Condoms
Spermicides
Diaphragm
Sterilisation
Timing sex
Abstinence
How can hormones be used to increase fertility
FSH and LH can be given to stimulate ovulation
However at times it doesn’t always work and can lead to pregnancies with multiple children
How does IVF work
Collecting eggs from a woman’s uterus
Can be injected with sperm
Grown into embryos
Transferred back into the uterus
FSH and LH are given before egg collection
However it can be expensive and can lead to ectopic pregnancies
Why are some people against IVF
It can destroy potential human life
Could lead to people choosing preferred characteristics
Which hormone stimulates the release of thyroxine
TSH
Examples of 2 hormones that are controlled by a negative feedback loop
Adrenaline
Thyroxine
What is auxin
A plant hormone that controls growth near the tips of shoots and roots
Controls growth in response to light and gravity
What is phototropism
When the shoot is exposed to light
Auxin accumulates on the shady side
The shaded side grows faster and the shoot bends towards the light
What is gravitropism
Where the shoots grow away from gravity and the roots grow towards gravity
In the roots the auxin is on the bottom
In the roots the auxin is on the bottom
What is auxin used for commercially
Killing weeds - disrupt the normal growth patterns which soon kills them
Growing from cuttings with rooting powder - grows rapidly
Growing cells in tissue culture - used as a growth medium
What is gibberellin and what is it used for
Stimulates seed germination
Used for:
Controlling dormancy
Induce flowering
Growing larger fruit
What is ethene and what is it used for
Stimulates fruit ripening by stimulating enzymes that cause the fruit to ripen
Used for:
Speed up ripening