Paper 2: Topic 5 Homeostasis & response - Nervous system (LV) Flashcards
Why do single-celled organisms not need a nervous system?
They can respond to changes in their environment easily and directly
Why does a multi-cellular organism need a nervous system?
- So that they can react to changes in their environment AND control and regulate changes in the different part of the body
- The nervous system allows cells to communicate with each other so a controlled response occurs
- A nervous system ensures co-ordinated behaviour
What structures are the main parts of the central nervous system?
What is the peripheral nervous system?
The CNS is made up of the
- Brain
- Spinal cord
The peripheral nervous system is made up of all the other nerves in the body that lead into and out of the of the spinal cord.
Describe how the central nervous system is connected to the other parts of the body?
Sensory and motor neurones in the peripheral nervous system
Define the term receptor
A cell that detects a stimulus (change in the environment)
AND
that can generate/produce a nerve impulse
State 4 different types of receptor
- Sound receptors
- Light receptors (photoreceptors)
- Chemical receptors (chemoreceptors)
- Pressure receptors
Define the term effector
A muscle or gland that responds to nerve impulses and causes a response
State how muscles respond to nerve impulses
They contract
HINT: do NOT write they “contract AND RELAX” - the impulse only causes them to contract
State how glands respond to nerve impulses
Glands produce and secrete a hormone into the plasma
State the function of the central nervous system
To receive and process information from the receptors AND
to co-ordinate the response
Write the pathway of a nerve impulse from stimulus to response (reflex arc)
Stimulus → receptor -→ sensory neurone → central nervous system → motor neurone → effector → response
Remember in a reflex action the brain is not involved
Explain why not all multi-cellular organisms have a nervous system
Only large, multi-cellular organisms have a nevous system
Small multi-cellular organsims e.g. jelly fish rely on reflex reponses
State the function of a neurone
To transmit a nerve impulse
Define the term ‘synapse’
A junction between two neurones
HINT: do NOT say “a gap” this is incorrect
Describe how a nerve impulse is transmitted across a synapse
- Neurotransmitters are released into the synapse from the synaptic knob
- The neurotransmitters diffuse across the synapse
- The neurotransmitters bind to receptors on the membrane of the next neurone
- And this then triggers the nerve impulse in the next neurone
Define the term neurotransmitter
A specialised chemical that is released from the end of the axon of one neurone that can diffuse across a synapse to trigger a nerve impulse in the next neurone
Neurotransmitters are chemical messengers
Explain the purpose of reflex actions
To prevent damage or harm to the organism.
They are rapid, they always results in the same response and they are involuntary.
State 5 examples of relex actions
- Blinking
- Coughing
- Sneezing
- Vomiting
- Knee-jerk
Describe a reflex arc
Hint: 6 main stages
- A change in the environment occurs (a stimulus)
- A receptor cell detects the stimulus
- A nerve impulse is sent along the sensory neurone to the CNS
- The nerve impulse is passed through the relay neurone in the CNS (NOT the brain)
- The nerve impulse is sent along a motor neurone to the effector
- The effector brings about a response (either a muscle contracts or a gland secretes a hormone)
What is the role (function) of a sensory neurone?
To transmit a nerve impulse from the receptor to the relay neurone
What is the role/function of a relay neurone?
To transmit a nerve impulse from the sensory neurone to the motor neurone
What is the role/function of a motor neruone?
To transmit a nerve impulse from the relay neurone to the effector
Explain the advantage of using reflex actions
- Quicker response time i.e. rapid response
- Which reduces damage and harm to the organism
Define a reflex action
Hint:
This is a similar question to “state the charcateristics of a reflex action”
A rapid, automatic response that does not involve the conscious part of the brain
Characteristics of a reflex action:
- rapid / fast
- involuntary response i.e. subconcious
State which 2 parts of the CNS a reflex arc may pass through
The spinal cord
OR
An unconscious part of the brain
Define the term reaction time
The time it takes to respond to a stimulus
State 4 factors that can affect the reaction time
- Age
- Alcohol
- Biological sex (do not say ‘gender’ as this is inappropriate in this context)
- Drugs e.g. caffeine
Describe the effect caffeine has a person’s reaction time
- Speeds the reaction time up
- i.e. time to respond to a stimulus decreases
- hence caffeine is a stimulant
Describe the effect alcohol has a person’s reaction time
- Slows down the reaction time
- i.e. time to respond to a stimulus increases
- hence alcohol is a depressant
Describe how a person’s reaction time can be measured
- Use the dropping a ruler technique
OR
- Use a computer programme
An investigation studying the effect of gender on reaction time is carried out using the dropped ruler technique.
State 4 factors that should be controlled to make the investigation valid
- Only use participants of the same age
- Ensure no participants have consumed any caffeinated drinks prior to the test
- Make sure all the participants use their dominant hand
- Make sure the ruler is dropped from the same height each time
State two advantage of using a computer programme rather than the dropped ruler technique to determine a person’s reaction time
- A computer programme will give reactions times to a greater level of precision (as they remove human error)
- A computer programme will give more accurate reaction times (they can record in milliseconds)
- The participant is unable to ‘predict’ the test using a computer programme (when using the ruler technique participants can try to predict when the ruler is going to be dropped)
State 2 safety issues that should be considered if you are investigating the effect of caffeine on reaction times
- Check the participants on not taking any medication that may be affected by caffeine
- Advise participants to not consume any more caffeine after the test as high levels of caffeine can cause side effects e.g. heart palpitations, sweats
Describe the structure of the brain
A mass of billions of interconnected neurones
Describe the function of the brain
To control complex behaviour
State the 3 main regions of the brain
- Cerebellum
- Cerebral cortex
- Medulla oblongata
Describe the location and role/function of the cerebral cortex
- This is the outer part of the brain
- It is located at the front of the brain
- It controls consciousness, memory , intelligence and language
Describe the location and role/function of the cerebellum
- It is located at the back of the brain
- It is responsible for muscle co-ordination
Describe the role/function of the medulla oblongata
- It is located at the base of the brain at the top of the spinal cord
- It is controls unconscious activities e.g. breathing, heart rate
What is the name given to scientists who study the brain?
Neuroscientists
State 3 methods neuroscientists have used to study the brain
- Studying patients with brain damage
- Electronically stimulating the brain
- MRI scans
Describe how neuroscientists have studied patients with brain damage to make discoveries about brain function
By studying which part of the brain is damaged in different patients scientists can study the effect different types of damage has on their behaviour etc