Human Nervous System
Reflexes
1) Stimulus received, recognised by receptor
2) Impulse travels along sensory neuron to spinal cord
3) Impulse passes along synapse and travels along relay neuron
4) Impulse passes along synapse and travels along motor neuron
5) Effector brings about response
Stimulus: Touching hot object
Receptor: Pain receptor (nociceptor) in the hand
Coordinator: Spinal cord (usually organs, such as brain, glands or spinal cord)
Effector: Bicep muscles in the arm (usually muscles or glands)
Response: Move hand away
A reflex is an unconscious response to a stimulus. Benefit is speed.
Effectors can be either muscles or glands
Impulses are electrochemical disturbances – they are NOT messages or signals
Synapses and Reflexes
1) Impulse reaches end of sensory neuron
2) Neurotransmitters in the sensory neuron (inside vesicles) release a synapse
3) Neurotransmitters diffuse across the synapse
4) Neurotransmitters bind to receptors on the relay neuron
5) This generates an impulse in the relay neuron
A woman’s hand accidentally touches a hot object. The woman moves her hand away rapidly.
Describe how the woman’s nervous system coordinates the reflex action. (6)
(1) receptor (in skin of finger / hand) detects stimulus
(2) electrical impulses pass along neurones
(3) impulses pass from sensory to relay to motor neurons
(4) synapse between neurones allows neurotransmitters to cross the gap via diffusion
(5) (synapses) in the central nervous system
(6) The effector is a muscle and brings about the muscle contracting to pull the hand away
Exemplar answer: The receptors in the hand detect the stimulus. This forms an electrical impulse
from the receptor which passes along the sensory neurone to the CNS. Neurotransmitters are
released when the impulse arrives at the synapse with the relay neurone from the sensory
neurone, allowing the impulse to pass through the synapse as the chemical diffuses across the
synapse. This occurs again when the impulse reaches the synapse between the relay and motor
, neurone in the arm from the relay neurone, and the impulse passes through the synapse as the
chemical diffuse across. The impulse then reaches the effector, which is a muscle, and causes
the muscle to contract and cause the hand to move rapidly.
Differences between the coordination of the nervous system and endocrine system:
1) Endocrine system is slower
2) Endocrine system is more long-lasting
3) Endocrine system involves the blood while CNS is via neurones
The sensory neurone carries impulses to the CNS. The relay neurone carries impulses within the
CNS. The motor neurone carries impulses from the CNS to the rest of your body.
Effectors: Muscles contract, Glands secrete hormones
The brain
The cerebral cortex is concerned with consciousness, intelligence, memory and language
The cerebellum is concerned with mainly coordinating muscular activity and balance
The medulla is concerned with unconscious activities (basic life processes), such as heart rate
and breathing
The hypothalamus is concerned with homeostasis
The pituitary gland is concerned with producing hormones for growth, reproduction and
metabolism
Learning about the brain can be difficult. There are three ways to learn about the brain from:
brain damage patients, such as from blunt force trauma or strokes; electrical stimulation during
surgery, using electrodes to stimulate different areas and see what effect this has; MRI scans by
showing which areas of the brain are affected by certain changes in behaviour
Traditional MRIs can only be performed if the patient is still. This means that people who struggle
to stay still such as children or those with Parkinson’s disease may not be able to do an MRI. New
MRIs can take images as someone carries out a simple task. This means that they can ask people
to do specific tasks to see which part of the brain is active and compare it with someone without
brain damage to see exactly where the damage is.
Reflexes
1) Stimulus received, recognised by receptor
2) Impulse travels along sensory neuron to spinal cord
3) Impulse passes along synapse and travels along relay neuron
4) Impulse passes along synapse and travels along motor neuron
5) Effector brings about response
Stimulus: Touching hot object
Receptor: Pain receptor (nociceptor) in the hand
Coordinator: Spinal cord (usually organs, such as brain, glands or spinal cord)
Effector: Bicep muscles in the arm (usually muscles or glands)
Response: Move hand away
A reflex is an unconscious response to a stimulus. Benefit is speed.
Effectors can be either muscles or glands
Impulses are electrochemical disturbances – they are NOT messages or signals
Synapses and Reflexes
1) Impulse reaches end of sensory neuron
2) Neurotransmitters in the sensory neuron (inside vesicles) release a synapse
3) Neurotransmitters diffuse across the synapse
4) Neurotransmitters bind to receptors on the relay neuron
5) This generates an impulse in the relay neuron
A woman’s hand accidentally touches a hot object. The woman moves her hand away rapidly.
Describe how the woman’s nervous system coordinates the reflex action. (6)
(1) receptor (in skin of finger / hand) detects stimulus
(2) electrical impulses pass along neurones
(3) impulses pass from sensory to relay to motor neurons
(4) synapse between neurones allows neurotransmitters to cross the gap via diffusion
(5) (synapses) in the central nervous system
(6) The effector is a muscle and brings about the muscle contracting to pull the hand away
Exemplar answer: The receptors in the hand detect the stimulus. This forms an electrical impulse
from the receptor which passes along the sensory neurone to the CNS. Neurotransmitters are
released when the impulse arrives at the synapse with the relay neurone from the sensory
neurone, allowing the impulse to pass through the synapse as the chemical diffuses across the
synapse. This occurs again when the impulse reaches the synapse between the relay and motor
, neurone in the arm from the relay neurone, and the impulse passes through the synapse as the
chemical diffuse across. The impulse then reaches the effector, which is a muscle, and causes
the muscle to contract and cause the hand to move rapidly.
Differences between the coordination of the nervous system and endocrine system:
1) Endocrine system is slower
2) Endocrine system is more long-lasting
3) Endocrine system involves the blood while CNS is via neurones
The sensory neurone carries impulses to the CNS. The relay neurone carries impulses within the
CNS. The motor neurone carries impulses from the CNS to the rest of your body.
Effectors: Muscles contract, Glands secrete hormones
The brain
The cerebral cortex is concerned with consciousness, intelligence, memory and language
The cerebellum is concerned with mainly coordinating muscular activity and balance
The medulla is concerned with unconscious activities (basic life processes), such as heart rate
and breathing
The hypothalamus is concerned with homeostasis
The pituitary gland is concerned with producing hormones for growth, reproduction and
metabolism
Learning about the brain can be difficult. There are three ways to learn about the brain from:
brain damage patients, such as from blunt force trauma or strokes; electrical stimulation during
surgery, using electrodes to stimulate different areas and see what effect this has; MRI scans by
showing which areas of the brain are affected by certain changes in behaviour
Traditional MRIs can only be performed if the patient is still. This means that people who struggle
to stay still such as children or those with Parkinson’s disease may not be able to do an MRI. New
MRIs can take images as someone carries out a simple task. This means that they can ask people
to do specific tasks to see which part of the brain is active and compare it with someone without
brain damage to see exactly where the damage is.
