Topic 5 - homeostasis and response Flashcards
what is homeostasis
the regulation of conditions inside your body and cells to maintain a stable internal environment in response to changes in both internal and external conditions .
to maintain optimum conditions for biological functions
what three things need to be regulated in your body
body temperature
blood glucose level
water content
what are the two automatic control systems
nervous system
hormonal /chemical system
what three parts make the automatic control systems
receptors
coordination centres
effectors
what is negative feedback
automatic control systems keep your internal environment stable using a mechanism called negative feedback .
when the level of something gets too high or low your body uses negative feedback to bring it back to normal
exaplin how the auromatic control system works when a stimulus level is too high or low
high :
receptor cells detect a stimulus level is too high
the coordination centre revieves and processes the infornmation then organises a response
effector produces a response which counteracts the change and restores optimum level
the level decreases
low:
receptor detects a stimulus level is too low
the coordination centre recieves and processes the infornmation then organises a response
effector produces a response which counteracts the change and restores the optimum level - the level increases
In vertebrates, what does the Central nervous system consist of
brain and spinal cord
what are sensory neurones
neurons that carry infornmation as electrical impulses from the receptors to the Central nervous system
what are motor neurones
the neurones that carry electrical impulses from the CNS to the effectors
what are effectors
all your muscles and glands that respond to nervous impulses
what are receptors
the cells that detect stimuli
there are many different types such as tast receptors on tongue and sound receptors on ear
how do the two effectors respond in different ways
muscles co tract
glands secrete hormones
what is the CNS and explain how it works when a small bird is eating some seed and a cat approaches it
The CNS is a coordination centre - it recieves infornmations from the receptors and then coordinates a response. the respons is carried out by the efectors .
example .
a small bird is eating some seeds
it spots a cat (this is the stimulus )
the receptors in the birds eye are stimulated. sensory neurones carry the infornmation from the receptors to the CNS .
The CNS decides what to do about it .
the CNS sends infornmation to the muscles in the bird’s wings (effectors ) along the motor neurones . the muscles contract and the bird flies away to safety.
what are synapses and how do they work
the connection between two neurones is called a synapse .
the nerve signal is transferred by chemicals which diffuse across the gap.
these chemicals then set off a new electrical signal in the next neurone.
what are reflexes
rapid, automatic responses to certain stimuli that don’t involve the conscious part of the brain.
give examples of how reflexes can prevent you from getting injured
if someone shone a bright light at your eyes, your pupils automatically get smaller so less light enters your eyes.
if you get a shock. your body releases adrenaline hormone auromatically.
what is the passage of infornmation in a reflex called
reflex arc
describe what happens in terms of reflexes when a bee stings someone.
- when a stimuluse (the bee sting) is detected by receptors, impulses are sent along a sensory neurone to a relay neurone in the CNS (spinal cord)
- when the impulses reach a synapse between the sensory neurone and relay neurone, they trigger chemicals to be released .these chemicals cause impulses to be sent along the relay neurone.
- when the impulses reacg a synapse between the relay neurone and a motor neurone , the smae thing happens/ chemicals are released and cause impulses to be sent along the motor neurone.
- the impulses then travel along the motor neurone to the effector (muscle in this case )
- the muscle then contracts and moves your hand away from the bee.
describe how you would carry out an investigation to measure reaction time
- person 1 sits on a stool with good upright posture , they then place the forearm of their dominant arm on a table with their hand over the edge.
- person 2 holds a ruler vertically with the 0 mark between persone 1’s thumb and forefinger
- person two drops the ruler at a random time
- person one has to catch it as quickly as possible
- record the measurement on the ruler that is equal to the top of person 1’s thumb
- repeat and calculate the mean
- test with different people
independant variable - people measured
dependant variable -reaction time
control - starting distance between thumb and forefinger, measurement, conditions in room
repeat with different inddependant variables
e.g. non dominant hand , caffeine intake ( give set volume of caffeine e.g. coke and wait half an hour then start experiment - compare with no caffeine )
how can reaction time be measured using a computer and what are the benefits of this ?
simple computer tests can also be used .
e.g. person has to click the mouse as soon as they see a stimulus on the screen
computers give a more precise rection time becasue they remove the posibility of human error.
as they can record in milliseconds it can give a more accurate result.
using computers removes the possibility that the person can predict when to respond
what is the cerebral cortex
the outer wrinklybit
responsible for things like consciousness . intelligence , memory and language
what does the hypothalamus do
regulates body temperature
sends signals to the pituitary gland
what does the medulla do
controls unconscious activities
breathing
heartbeat
what does the cerebellum do
responsible for muscle contraction
what different methods do scientists use to study the brain
study patients with brain cancer
if a small part of the brain has been damaged , the effect this has on the patient can tell you a lot about what the damaged part of the brain does.
electrically stimulating the brain
the brain can be electrically stimulated by pushing a tiny electrode into the tissue and giving it a small zap of electricity. By observing what stimulating different parts of the brain does , it is possible to get an idea of what those parts do .
MRI scans
a magnetic resonance imaging scanner is a bag tube like machine that can produce a very detailed picture of the brains structure .
scientists use it to find out what areas of the brain are active when people are doing things like listening to music or trying to recall a memory .
what are the advantages and disadvantages of studying the brain
knowledge of how the brain works has led to the development of treatments for disorders of the nervous system . for example , electrical stimulation of the brain can help to reduce muscle tremors caused by nervous system disorderss such as parkinson’s disease
the investifation of brain function and any treatment of thje brain dammage or disease is difficult.
also carries risks such as physical dammage to brain or increased problems with brain function e.g. difficulty with speech
what are each of these parts of the eye
sclera
cornea
iris
lens
retina
ciliary muscles
suspensory ligaments
optic nerve
sclera - tough , rupporting wall of the eye
cornea - transparent outer layer found at the front of the eye it refracts (bends ) light into the eye.
iris - contains muscles that allow it to control the diameter of the pupil and therefore how much light enters the eyes
lens - focuses the light onto the retina
retina - contains receptor cells sensitive to light intensity and colour
ciliary muscles and suspensory ligaments - controll the shape of the lens
optic nerve - carries impulses from the receptors on the retina to the brain
what happends when light receptors in the eye detect a very bright light .
a reflex is triggered that makes the pupil smaller .
the circular muscles in the iris contract and the radial muscles relax .
this reduces the amount of light that can enter the eye.
