Homeostasis and response

Created by

Hannah Owolabi

Cards (100)

What is homeostasis 
The regulation of the internal conditions of a cell or organism to maintain optimum conditions for functions in response to internal and external changes
Identify 3 ways which the body uses homeostasis to maintain optimal conditions for enzyme action and cell functions
- Control of blood glucose concentration
- Control of body temperature
- Control of water levels
Homeostasis consists of automatic control systems; what is the function of automatic control systems 
They recognise when there is a change from optimal conditions, and so they send a signal to reverse that change, so that the levels go back to normal
What 2 responses do automatic control systems have
- Nervous responses
- Chemical responses
Identify 3 features of an automatic control system
- Receptor cells
- Co-ordination centre
- Effector
What is the function of receptor cells 
Detect changes in the environment (stimulus)
What is a stimulus 
A change in the environment
What is the function of the coordination centre
It receives and processes the information from the receptor cells
Identify 3 examples of coordination centres
- Spinal cord
- The brain
- The pancreas
What is an effector and what is its function
A muscle or a gland which carries out the response to restore the optimum level
Identify 2 methods of cell signalling in an automatic control system
- The nervous system
- The endocrine system
What is the function of the nervous system
The nervous system allows the body to react to its surroundings and coordinate actions in response to to stimuli
What are the 2 components of the nervous system
- Central Nervous System (CNS)
- Peripheral Nervous System (PNS)
What is the central nervous system
The brain and the spinal cord
What is the function of the central nervous system
It receives information from receptors and then coordinates a response
What is the peripheral nervous system 
Nerves that cover the body, which run to and from the central nervous system
What is the function of a neurone/nerve cell
Carries electrical impulses from one point to another
Describe and explain how the nervous system works
1. Receptor cells convert a stimulus into an electrical impulse
2. This electrical impulse travels along cells called sensory neurons to the central nervous system
3. Here, the information is processed and the appropriate response is coordinated, resulting in an electrical impulse being sent along motor neurons to effectors
4. The effectors carry out the response
Identify 2 examples of effectors
- Muscles (contract)
- Glands (releases hormones)
In the nervous system, which part is the coordination centre
The central nervous system
What is a reflex
An automatic response which takes place before you have time to think
What is a reflex action 
A protective response to a stimulus where an impulse travels directly to the spinal cord and sends a message to the brain so that less damage occurs to the body
How is the decision making of a reflex different to decision making of other responses in the nervous system
There is no decision making by the conscious part of the brain, making them automatic and rapid
Why are reflex actions important
They are rapid and automatic, so the body can respond to stimuli quickly, which helps to avoid injuries
What is a reflex arc 
The nerve pathway that underlies our unconscious reflexes, allowing vital responses to take place quickly
Describe the structure of a reflex arc
1. A stimulus is detected by receptors
2. Electrical impulses pass from the receptor along a sensory neurone to the central nervous system
3. At the end of the sensory neurone there is a junction called a synapse, where a chemical is released and diffuses across to a relay neurone in the CNS, where it triggers an electrical impulse
4. The electrical impulse now passes across the relay neurone and reaches another synapse where another chemical is released, triggering an electrical impulse in a motor neurone
5. The electrical impulse passes down the motor neurone to an effector
6. The impulse reaches an effector resulting in the appropriate response
Describe the reflex arc when your finger touches a hot flame
- The stimulus, which is the heat from the flame, is detected by the receptor in the skin
- Electrical impulses pass from the receptor along a sensory neurone to the central nervous system
- The electrical impulse passes through the synapse, where a chemical diffuses across to a relay neurone in the CNS and triggers an electrical impulse
- The electrical impulse passes across the relay neurone and reaches another synapse, where a chemical is released and triggers an electrical impulse in a motor neurone
- The electrical impulse passes down the motor neurone to the effector, which is a muscle
- The response is the muscle contracting and pulling away from the heat
What is a synapse 
The connection between two neurones
How does a nerve signal move across a synapse
The nerve signal is transferred by chemicals which diffuse across the gap, and set off a new electrical signal in the next neurone
Describe the practical which can be used to measure a person's reaction time 
1. Person 1 sits on a chair with good upright posture, and then places the forearm of their dominant arm across the table, with their hand overhanging the edge
2. Person 2 holds a ruler vertically; the 0cm mark should be between person 1's thumb and first finger
3. Person 2 drops the ruler at a random time
4. Person 1 has to catch the ruler with their thumb and first finger as quickly as possible when it drops
5. Person 2 records the measurement on the ruler that is level with the top of person 1's thumb
6. The test is then repeated several times and a mean is calculated; you can convert these results to a reaction time by using a conversion table
7. This is then repeated but with person 1 testing the reaction time of person 2, so person 2 will catch the ruler
What is the independent, dependent, and control variable of the practical to find someone's reaction time 
IV; the person having their reaction time tested
DV; the reaction time
CV; starting distance between the thumb and the first finger, measuring the ruler at the top of the thumb, keep the conditions in the room the same (lighting and level of background noise)
In the experiment of measuring reaction time, what other independent variables could you investigate
- The effect of practise; one person would catch the ruler a large number of times, and then you would look to see if the reaction time changes depending on the number of tries
- Whether the reaction time depends on the hand catching the ruler; you would carry out the test with the dominant hand and then with the non dominant hand of the same person
- Whether certain chemicals affect reaction time, such as caffeine, where you would drink a caffeinated substance 30 minutes before the experiment, then compare this reaction time with their normal reaction time
Identify the 3 different parts of the brain
- Cerebral cortex
- Cerebellum
- Medulla
What are the functions of the cerebral cortex
- Controls language
- Controls memory
- Controls consciousness
Where is the cerebral cortex
It is the outer part of the brain
What are the functions of the cerebellum
- Controls balance
- Co-ordinated movement
Where is the cerebellum
It is the rounded structure towards the back of the brain
What are the functions of the medulla
- Controls heartrate
- Controls breathing rate
Where is the medulla
In the brain stem in front of the cerebellum
Identify 3 reasons why studying the brain/treating brain damage is extremely difficult
- The brain is protected by the skull and so it very tricky to access
- The structures of the brain are extremely complex, so it is difficult to work out exactly which parts of the brain carry out specific functions
- The brain is very delicate and easy to damage