homeostasis Flashcards
what is homeostasis
is the regulation of the internal conditions of a cells organism to maintain optimum conditions for function in response to internal and external changes
what does homeostasis control in the human body
- blood glucose concentration
- body temperature
-water levels
what features do all automatic control system have
receptors , co-ordinatino centres , effectors, response
what are receptor cells
cells that detect stimuli ( changes in the environment)
what is the coordination centre
recieve and process information from receptors
what are examples of coordination centres
brain , spinal cord , pancreas
what are effectors
bring about the response which restores optimum levels
what are examples of effectors
muscles , glands
what is a key role about the Nervous system
enables humans to react to their surroundings and coordinate their behaviours eg reflex arc
describe the process that the neurones take from receptors to the response in the nervous system
receptors detect the stimulus and send electrical impulses down neurones to the central nervous system. The central nervous system coordinates the response of effectors, which may be muscles contracting or glands secreting chemicals
describe the process of what happens when you touch a hot objects
- the receptors detect the stimulus - the stimulus is the heat and the receptors are the skin cells
- Electrical impulses pass from the receptors along a sensory neuron. At the end of the sensory neuron, there is a junction ( synapse), a chemical is released, and the chemical diffuses across to the relay neuron in the central nervous system, where an electrical impulse is triggered.
- the electrical impulse passes across the relay neuron and reaches another synapse where a chemical will be released. the chemical triggers and electrical impulses in a motor neurone
- the electrical impulse travels down the motor neuron to the effector, the muscle. the muscle contracts and pulls the hand away from the heat - pulling the hand away is the response
why are reflex actions important
- they are automatic and rapid; they do not involve the conscious part of the brain.
REQUIRED PRACTICAL - plan and carry out an investigation into the effect of a factor on human reaction time.
two people are required - person A and person B ( person B measures reaction time of person A )
-person A sits on the stool with a good upright posture
-person A places the forearm of their dominant arm across the table with their hand overhanging the edge
-person B holds the ruler vertically
- the 0 cm mark should be between person A thumb and first finger
-person B tells person A to prepare to catch
-person B drops the ruler at a random time
-person A needs to catch the ruler as quickly as they can
-person B records the measurement that is level with the top of person As thumb
-person A will take a short rest and then continue with experiment to calculate mean
- at the end person A and person B swap places - this allows us to see if two people have different reaction times
what is the independent variable of the reaction time experiment
- the person having their reaction time tested
other independent variables that may be tested are:
effect of practice - one person catches the ruler loads of times - and then sees if the reaction time changes with number of tries
OR
if reaction time depends on the hand catching the ruler eg the dominant hand vs the weaker hand
OR
if certain chemicals affect the reaction time eg drinking caffeine which lowers reaction time
what is the dependent variable of the reaction time experiment
the reaction time
what is the control variable of the reaction time experiment
-starting distance between thumb and first finger needs to be constant
-keep conditions in the room same eg lighting and background noise
- always measure at the top of the thumb
what are three parts of the brain and their functions
cerebral cortex - highly folded outer part of brain- functions : language , memory , consciousness
cerebellum - controls balance and coordinates movement
medulla - controls heart and breathing rate
what are the three ways that scientists use to investigate the brain
- scientists look at patients who have suffered from brain damage- by looking to see where the damage has taken place they can link that part of the brain to its function
- scientists also electrically stimulate different brain parts and look at the effects on the person’s behaviour- which can narrow their specific regions. to their functions
- use MRI scanning to look at which parts of the brain are most active during different activities
what are the difficulties of investigating brain function
- the brain is protected by the skull so hard to access
- structures of the brain are complex so it is hard to work out exactly which parts carry out specific functions
-brain is delicate and easily damaged
what type of organ is the eye
a sense organ containing receptors sensitive to light intensity and colour
what is the job of the cornea
start the focussing of the light rays
describe the process how we detect light
- light rays pass through the transparent front of the eye ( the cornea )
- the light rays pass through the pupil in the centre of the iris
- the light rays pass through the lens
- the light rays are now focussed onto the back of the eye (retina)
-the receptor cells in the retina know send electrical impulses down the optic nerve to the brain
what is the job of the lens
to focus the light rays onto the back of the eye
what is a key feature of the lens
can change shape - allowing us to focus on distant or near objects
what is accommodation
process of changing the shape of the lens to focus on near or distant objects.
what features do the retina have
receptor cells for light - the receptor cells help us detect light intensity and light colour
what is the sclera
the white, tough outer layer of the eye - protects the eye
what are the suspensory ligament s
