Homeostasis - The CNS and reflexes 116-120 Flashcards
why is it important to keep the conditions inside your body steady
your cells need the right conditions to function properly including for enzyme action
what are automatic control systems
they regulate your internal environment - both hormonal and nervous
what are the main components of your automatic control systems
3 points
1) cells called receptors
2) coordination centres - brain, spinal cord, pancreas
3) effectors
how do your automatic control systems keep your internal environment stable
2 points
1) using a mechanism called negative feedback
2) when the level of something (water or temp) gets too high or low, negative feedback brings it back to normal
what happens in negative feedback when the level of something (e.g. water or temp) is too high/ low
5 points
1) receptor detects a stimulus level is too high or low
2) the coordination centre receives and processes the info then organises a response
3) effector produces a response which counteracts the change and restores the optimum level
4) the effectors will carry on producing the response for as long as they’re stimulated by the coordination centre
5) this might cause the level to change too much so the receptor detects if the level is too different and negative feedback starts again
what are the different parts of the nervous system
4 points
1) the central nervous system (CNS) includes - brain, spinal cord
2) sensory neurones - carry information as electrical impulses from the receptors to the CNS
3) motor neurones - carry electrical impulses from CNS to effectors
4) effectors - all your muscles and glands that respond to nervous impulses
what are receptors
the cells that detect stimuli
how do muscles and glands respond to a nervous impulse
1) muscles contract
2) glands secrete hormones
how is the response carried out when a bird spots a cat
and draw the path out
5 points
1) when the bird sees the cat the receptors in the bird’s eye are stimulated
2) sensory neurones carry the info from the receptors to the CNS
3) the CNS decides what to do about it
4) the CNS sends info to the muscles in the birds wings (the effectors) along the motor neurone
5) the muscles contract and the bird flies away
6) pg 118 of bio book
what is the connection between two neurones called
a synapse
how are electrical signals carried across a synapse
2 points
1) the nerve signal is transferred by chemicals which diffuse across the gap
2) these chemicals then set off a new electrical signal to the next neurone
draw how are electrical signals carried across a synapse
pg 118 of bio book
what are reflexes
they are rapid, automatic responses to certain stimuli that don’t involve the conscious part of the brain
what is a reflex arc
the passage of information from receptor to effector
explain how a reflex arc goes through the central nervous system
6 points
1) the neurones in reflex arcs go through the spinal cord or an unconscious part of the brain
2) when a stimulus (a bee sting) is detected by receptors, impulses are sent along a sensory neurone to the CNS
3) when an impulse reaches a synapse between the sensory neurone and a relay neurone they trigger chemicals to be released, these cause impulses to be sent along the relay neurone
4) when impulses reach a synapse between a relay neurone and a motor neurone, the same thing happens
5) the impulses then travel along the motor neurone to the effector (in this case a muscle)
6) the muscle then contracts and moves your hand away from the bee
how can reaction time be measured using caffeine
6 points
1) caffeine is a drug that can speed up someones reaction time, the person being tested should sit with their arm resting on the edge of a table
2) hold a ruler vertically between their thumb and forefinger, make sure that the 0 end of the ruler is level with their thumb, then let go without warning
3) the person being tested should try catch the ruler as quickly as they can
4) reaction time is measured by the number where the ruler is caught, the higher the number the slower the reaction time
5) repeat this several times and calculate a mean distance
6) the person being tested should has a caffeinated drink, and after 10 mins should repeat steps 1-5
what are some control variables when measuring reaction time with caffeine
4 points
1) use the same person to catch the ruler each time
2) always use the same hand
3) the ruler should always be dropped from the same height
4) the person being tested shouldn’t have any caffeine before the experiment
how can reaction time be measured using a computer
4 points
1) computer tests can be used to measure reaction time as well - e.g. a person will click the mouse as soon as they see a stimulus on the screen
2) computers can give more precise reaction time because they remove the possibility of human error from the measurement
3) the computer can also give measurements in milliseconds meaning it is more accurate
4) it also removes the possibility the person being tested can predicts when to respond
