homeostasis and response Flashcards
what is homeostasis
regulation of conditions in the body
to maintain stable internal environment in response to internal and external conditions
what is an example of homeostasis
being in a hot desert or snow but keeping ourselves 37 degrees
what does our bodies automatic control system do
recognises change from optimal conditions and reverse the change
what are the parts of automatic control systems
receptors
coordination centres
effectors
what do receptors do
detect change
what are some coordination centres and what do they do
brain and spinal cord
-they interpret change and decide what needs to be done
what are some effectors and what do they do
muscles that contract or glands that secrete hormones
-carry out change
what are the roles of the nervous and endocrine system
to send signals between effectors ,coordination centres and receptors
describe the features of the nervous system
-very fast and precise
electrical impulses through nerves
what is an example of the use of the nervous system
responds quickly eg when we touch sharp objects
what is the role of the endocrine system
secreting hormones which only affect specific cells with specific receptors through (bloodstream)
what are the features of the endocrine system
-slow
-long lasting
-more generalised
what is negative feedback
when level of something in a body is too high or low and is regulated
what is an example of the 1st stage of negative feedback
cold outside detected by receptors(eg in skin)
what is the 2nd stage of negative feedback
nervous system sends impulses to coordination centre
what is the 3rd stage of negative feedback
coordination centre sends more signals to effectors which carry out useful responses (eg shivering)
what is the last stage of negative feedback
the useful response will return us to normal(eg shivering increase body temp back to normal)
what can homeostasis control in humans
-blood glucose conc
-body temp
-water levels
-blood Ph
Why does the body need to maintain optimal conditions?
For optimal enzyme action and cell function
how do our bodies communicate to coordinate behaviour and respond to our surroundings
nervous and endocrine system
what are neurons adapted to do
carry elec impulses from 1 point to another
what are the adaptations of neurons(nerve cells)
long
thin
lots of branched connections allowing them to pass messages to other nerve cells
what is a synapse
connection between the cells that allows nerve cells to communicate
how is an electrical impulse communicated between cells
elec impulse hits end of a cell releasing chemicals that diffuse across the synapse
these then trigger another elec impulse
what is the central nervous system
made up of brain and spinal cord where thinking occurs
what does the central nervous system do
takes in sensory info ,decides what needs to be done , then sends orders to the rest of the body
how does the central nervous system receive info about what is happening in the body
through sensory neurones which carry info from receptors to cns
what does our cns do when it decides what to do w info from sensory neurones
sends impulses back via motor neurones to effectors
what is a reflec arc
nerve pathway that underlies unconscious reflexes
what is an example of our reflex arc responding
when we move hand away from hot pan
when we blink when eye is touched
what are pros of reflex arc
rapid
automatic
journey in reflex arc
stimuli
receptor cells
sensory neurones
cns
relay neurone
motor neurone
effector
What is a reflex?
An automatic response to a stimulus
what are some more examples of reflexes
Blinking when you get dust in your eye
Sneezing
what is the brain made of and responsible for
billions of interconnected nerve cells
and responsible for complex behaviours/holding memories
what are examples of complex behaviours
running
choosing what to wear
running
reading
what makes the important decision in the cns
the brain
what is big wrinkly part of the brain all over the top
cerebral cortex
what is the cerebral cortex responsible for
-consciousness
-intelligence
-memory
-language
-senses
what are hemispheres
the 2 halves of the cerebral cortex
what does each hemisphere control
left hemisphere-controls muscles on right of body
right hemisphere-controls muscles on left
what is the smaller section at the back of the brain
the cerebellum
what is the cerebellum responsible for
balance and muscle coordination
eg walk without falling over
what is in the centre of the brain
hypothalamus
what does our hypothalamus do
-regulate things like body temp
-send signals to pituitary gland
where is the brain stem and what does it contain
at the bottom linking brain to spinal cord containing medulla
what is the role of the medulla
-controlling our unconscious activities
eg breathing/heart beating
what is the 1st way we study brain and example
-via people with brain damage to learn which parts do what
eg:someone gets stroke/1 part of brain is damaged/person cant hear anymore/part of brain may be responsible for hearing
what is the 2nd way we can study the brain
-by elec stimulating diff parts of brain using electrode
eg:zapping back of the brain causing vision to go funny
what is the final way we can study brain damage
-scanning brain
eg via ct scans
pet scans
mri scans
what do each scan of the brain do
ct scans find out areas of brain that are damaged
pet/mri -underlying activity
eg-music generating patterns in brain
what can go wrong with the brain making it hard to treat
-tumours
-trauma
-mental health problems
-infection
what is 1 reason why treating the brain is so difficult
-difficult to physically fix as it is encased within skull and surrounding brain tissue is fragile
what is another reason treating the brain is so difficult
so complex so hard to treat with drugs and chemicals
what is the cross section of the brain
A view into the inside of something made by cutting through it.
how does the eye respond to changes in light intensity
iris reflex
what is the cornea
where light hits eye
adaptations of cornea
transparent-allow light through
-no blood vessels
how does cornea get oxygen
it diffuses into it via outside air
why do we need the cornea
causes all light to refract that passes into it
what is iris and what does it do
coloured part of eye
controls size of pupil
what is pupil
gap in middle of iris that allows light to pass through to lens
what is the job of the lens
changes shape to control strength that it refracts light to focus it on retina
what makes up retina
2 receptor cells called cone and rod cells
describe a cone cell
-sensitive to colour of light so we can see colour
-dont work well in low light
describe a rod cell
-more sensitive to light
-only allow us to see in black and white
why cant you see colours in dark
only rod cells are working
what is the fovea
the spot on retina lens focuses light on with only cone cells
-helps us see most clearly
what does the optic nerve do
takes impulses from receptor cells to brain
what can damage retina
-bright light conditions
what is the iris reflex for bright light
pupil size decreases in bright light so less light enters damaging retina
-constriction
what is the iris reflex low light
pupil largens in low light so more light gets in and you can see in dark
-dilated
what 2 muscles allow iris reflex to happen
circular muscles
radial muscles
how do muscles make pupil constrict
circular contract
radial relax
how do muscles make pupil dilate
circular- relax
radial-contract
Which two stimuli are the receptor cells of the eye sensitive to?
Light intensity
Colour
What is the purpose of the iris reflex?
To ensure the optimum amount of light enters the eye
what is accomodation
reflex that changes refractive power of lens so you can see near and far
what 2 muscles control the shape of the lens
ciliary muscles
suspensory ligaments-connects lens to ciliary
why does light refract through cornea
so it focuses on fovea
what makes a lens refract more strongly
more curved
short and fat
when an object is nearby what happens to lens ciliary and suspensory
ciliary contracts and suspensory slacken so lens converts back into fatter natural shape
what changes in the lens when an object is far and near
lens doesnt need to do as much
what happens to lens suspensory and ciliary when object is far
ciliary relaxes
suspensory-tighten
lens-stretches
What cant suspensory ligaments do
contract and relax as they arent muscles
what causes longsightedness
when lens cant refract enough
what causes shortsightedness
lens refract lights too much
describe what happens in long sighted ness
image is focused behind fovea so it is blurry
how can long sightedness be fixed
glasses with convex lenses for extra refractive power
describe short-sightedness
lens refracts light from distant objects focuses and forms image before retina making object blurry
how to fix shortsightedness
glasses with concave lenses as they refract light outwards to counter overrefraction
medical name for long/short sightedness
long-hyperopia
short-myopia
