Homeostasis and response Flashcards
(49 cards)
Define Homeostasis
- Regulation of internal conditions of a cell/organism (in response to internal/external changes)
- To maintain optimum conditions for function
Why is Homeostasis important?
To main optimum conditions for enzyme action and all cell functions
Give 3 examples of conditions regulated in the human body.
- Blood glucose levels
- Body temperature
- Water levels
Describe how internal conditions and regulated?
- Receptor cells e.g temperature receptor
- detects a stimulus - Coordination centre e.g brain and spinal cord, pancreases
- receive and process information from receptors - Effectors e.g muscles or glands
- Bring about a response to restore optimum levels
Suggest why body temperature should not be allowed to increase very much (2 marks)
- Enzyme becomes denatured at high temperatures
- So they don’t work/cant catalyse reactions
Outline the stages in negative feedback mechanism when blood pressure becomes too high (2 marks)
- Receptors detect that blood pressure is too high and send a signal to the coordination centre
- Coordination centre processes information and organises a response/stimulates and effector
- Effector produces a response to decrease blood pressure
What does the nervous system enable organisms to do?
- react to changes in their surroundings
- coordinate their behaviour
Describe the overall structure of the human nervous system
Central nervous system - brain and spinal cord (billions of interconnected neurones)
Other nerves (bundles of neurones)- run to and from the CNS
Describe how information passes along neurones
As electrical impulses
Define the term synapse
A small gap between 2 neurons
Describe how information passes across a synapse
1 When electrical impulses reaches end neurone 1, a chemical is released
2. Chemical diffuses across a synapse
3. Chemical attaches to neurone 2, triggering another electrical impulses
Describe the steps involved in a nervous system response to a stimulus
- receptor detects a stimulus, initiates an electrical impulse
- sensory neurone processes information from receptors- to the CNS as electrical impulses
- CNS coordinates response of effectors
- Motor neurone passes information from CNS to effectors as electrical impulses
- Effector - muscles contract or glands secrete hormones
What is a reflex action and why are they important?
- Automatic and rapid response as it doesn’t involve the conscious part of the brain
- Importance- protective and help minimise damage to body
Describe how a reflex action occurs via a reflex arc
- Receptor- detects a stimulus initiates as impulse
- Sensory neurone- passes info from receptors to the CNS as impulses
- Relay neurone- in spinal cord/unconscious brain;passes impulses from sensory to motor neurone
- Motor neurone- passes information from CNS to effectors as impulses
- Effector- muscles contract or glands secrete hormones
Adenosine is a chemical made by the body that binds to receptor molecules on relay neurones/ It decreases the number of impulses in relay neurones. Caffeine binds to the same receptor molecules, blocking the receptor so adenosine cannot bind. Suggest by this decreases reaction time.
(2 marks)
- Fewer adenosine molecules can bind to receptors/adenosine has less effect on relay neurone
- So impulses in relay neurone are more frequent
Why does a conscious action take longer than a reflex action (1 mark)
- impulse has to travel to the brain
- pathway is a lot longer/more synapses
A person accidentally touches a hot object, then moves their hand away quickly. Describe how information about the hot object is detected and how the information reaches the muscles in the arm (4 marks)
- temperature receptors in skin and hand detect
- an impulses travels along the sensory neurone
- then travels along the relay neurone and then the motor neurone
- chemical moves/diffuses across the synapse
Describe how reaction time can be measured using the ruler drop test
- Person A holds the ruler just above open hand of person B
- control variable: height ruler dropped from - Ruler dropped without warning and person B catches it
- Record distance where ruler is caught
- control variable: measurements taken from same point e.g top of thumb - Convert distance into time using a standard scale chart
Describe a method to investigate the effect of caffeine of reaction time
- Measure reaction time of a 5 people using the ruler drop test
- additional control variables- use same hand each time, same amount of sleep, previous intake of caffeine that day, age, sex - Repeat for each person 5 times and calculate a mean (remove anomalous readings)
- Gives individuals caffeine and wait 15 mins and repeat step 1-2
- control variable: volume and conc of caffeine
Explain a better method to measure reaction time
- use a computer-click mouse/keyboard as soon as stimulus seen on screen
- time is more precise and accurate e.g as computer timer has a higher resolution
The students measured 10 reaction times for each person rather than 3 reaction times. Explain why (2 marks)
- to increase validity/repeatability to get representative results
- because of variation in results
Explain why the ruler-drop test does not involve a reflex action (2 marks)
- not automatic as it is a voluntary action
- because it involves the conscious part of the brain
Why did students wait 15 mins after drinking coffee before repeating the test (1 mark)
Time for coffee/caffeine to work to be absorbed and to reach the brain
Using a computer program to measure reaction time is likely to be more valid than the method using a dropped ruler. Give 2 reasons why (2 marks)
- No indication beforehand when colour will change/might be able to tell when a person is about to drop the ruler
- measurement of time is more precise
- resolution of a computer timer is higher
