14.1 Mammalian Nervous System (Cambridge (CIE) O Level Biology): Flashcards
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Define neurone.
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Define neurone.
A nerve cell that carries electrical nerve impulses.
Define nerve.
A bundle of neurones.
What two structures make up the central nervous system (CNS)?
The brain and the spinal cord.
What does the peripheral nervous system (PNS) consist of?
All of the nerves in the body, outside the brain and spinal cord.
In what form is information carried through the nervous system?
As nerve impulses — electrical signals that pass along neurones.
What are the two main roles of the mammalian nervous system?
The nervous system:
helps us make sense of and respond to our surroundings
coordinates and regulates body functions
The central nervous system is made up of the brain and the .
The central nervous system is made up of the brain and the spinal cord.
A bundle of neurones is known as a .
A bundle of neurones is known as a nerve.
True or False?
The nervous system carries information as electrical impulses.
True.
Nerve impulses are electrical signals that travel along neurones.
True or False?
The brain and spinal cord make up the peripheral nervous system.
False.
The brain and spinal cord make up the central nervous system; the peripheral nervous system is all the other nerves.
Define axon.
The long fibre of a neurone that carries the nerve impulse.
Define dendrites.
Extensions from a neurone's cell body that connect to many other neurones.
What is the function of a sensory neurone?
It carries impulses from sense organs to the CNS.
What is the function of a relay neurone?
Found inside the CNS, it connects sensory and motor neurones.
What is the function of a motor neurone?
It carries impulses from the CNS to effectors (muscles or glands).
Why is the axon insulated by a fatty sheath with uninsulated nodes?
So the impulse jumps from one node to the next, speeding up transmission.
What are the three main types of neurone?
The three types of neurone are:
sensory
relay
motor
neurones carry impulses from sense organs to the CNS.
Sensory neurones carry impulses from sense organs to the CNS.
Motor neurones carry impulses from the CNS to such as muscles or glands.
Motor neurones carry impulses from the CNS to effectors such as muscles or glands.
True or False?
Relay neurones connect sensory and motor neurones.
True.
Relay neurones are found inside the CNS and link sensory neurones to motor neurones.
True or False?
Motor neurones carry impulses towards the central nervous system.
False.
Motor neurones carry impulses away from the CNS, to effectors such as muscles and glands.
Define reflex action.
An automatic, rapid response to a stimulus that does not involve the brain as coordinator.
Define reflex arc.
The pathway of neurones (sensory, relay and motor) that carries an impulse in a reflex action.
Why is a reflex action faster than a voluntary response?
Because it does not involve the brain as the coordinator.
What is the benefit of a reflex action being rapid and automatic?
It helps to minimise damage to the body.
What are the parts of a reflex arc, in order?
A reflex arc runs:
stimulus
receptor
sensory neurone
relay neurone
motor neurone
effector
response
How does a voluntary response differ from a reflex response?
A voluntary response involves a conscious decision and starts with the brain, whereas a reflex does not involve the brain as coordinator.
In a reflex arc, which neurone carries the impulse to the effector?
The motor neurone.
In a reflex arc, the sensory neurone carries the impulse to the , where the relay neurone is found.
In a reflex arc, the sensory neurone carries the impulse to the spinal cord, where the relay neurone is found.
An effector in a reflex arc is either a or a gland.
An effector in a reflex arc is either a muscle or a gland.
True or False?
A reflex action involves the brain making a conscious decision.
False.
A reflex action does not involve the brain as coordinator; it is automatic and you are only aware of it afterwards.
True or False?
Reflex actions help protect the body from harm.
True.
They are rapid and automatic, which minimises damage to the body.
Define synapse.
The junction (gap) between two neurones.
Define neurotransmitter.
A chemical messenger that diffuses across the synaptic gap to pass an impulse between neurones.
What are the three main parts of a synapse?
A synapse consists of:
the synaptic cleft (gap)
the presynaptic knob, containing vesicles of neurotransmitter
the postsynaptic membrane, with receptor proteins
Where in the synapse are neurotransmitter molecules stored?
In vesicles in the presynaptic knob.
How is a nerve impulse passed across a synapse?
Neurotransmitters are released from vesicles, diffuse across the gap and bind to receptors on the postsynaptic membrane, stimulating the next neurone.
Why are neurotransmitters destroyed after they have acted?
To prevent continued stimulation of the second neurone, which would send repeated impulses.
Why do impulses travel in only one direction at a synapse?
Only the presynaptic neurone releases neurotransmitters and only the postsynaptic membrane has receptors.
Neurotransmitters across the synaptic gap and bind to receptors on the postsynaptic membrane.
Neurotransmitters diffuse across the synaptic gap and bind to receptors on the postsynaptic membrane.
The postsynaptic membrane contains that neurotransmitters bind to.
The postsynaptic membrane contains receptor proteins that neurotransmitters bind to.
True or False?
At a synapse, neurones are directly joined with no gap between them.
False.
Neurones never touch; there is a small gap (the synaptic cleft) that neurotransmitters diffuse across.
True or False?
Synapses ensure that nerve impulses travel in only one direction.
True.
Only the presynaptic neurone releases neurotransmitters, so impulses can pass only one way.
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