Topic 8 THE NOTES
8.1 Know the structure and function of sensory, relay and motor neurones including the role of Schwann cells and myelination.
Describe the organisation of the nervous system and Describe the structure and role of different types of
Describe the structure and purpose of myelination.
role of the nervous system neurones in a reflex response
neurone role structure
Sensory ● Nerve impulse • long myelinated dendrons and
generated by axons
sensory cells • The cell body is located away from
the main axon
• dendrites, dendron, cell body and
● Pass impulses
part of axon are located outside
towards the CNS the CNS
• terminal branches are located
within the CNS
Relay ● Receive impulses • Contain many short dendrons,
from sensory each with many dendrites
neurones • Contain a single short axon, with
many terminal branches
• Located entirely within the CNS
● Pass impulses to
the effector neurone
Effector ● Receive impulses • Sometimes also called motor
from the CNS neurones
• The cell body at one end of the
neurone within CNS
● Pass impulses to • One very long axon with many
the effector organs to terminal branches
generate the
• Synapsing with the effector
response
• Axon and terminal branches
outside of CNS
Describe the role of the nervous system • The myelin sheath is specialised cells
called Schwann cells
• The nervous system can be thought of as physical
connection between distant organs/cells that need to • That are wrapped around axons to speed
communicate quickly to make a response
• They allow communication between sensors (PNS), up nerve impulses
control centres and effectors (PNS)
• Communication occurs by nerve impulses that travel
• Because they provide electrical insulation
the length of long specialised cells called neurones • Sensory and motor neurones are
• Impulses pass from sensory, to relay to motor
neurones, finally to effectors, in order to make myelinated
response
• Impulses are transmitted from neurone to the next
• Because they are long, and impulses are
across structures called synapses required to travel faster
•
, 8.2 i) Understand how the nervous systems of organisms can cause effectors to respond to a stimulus. ii) Understand how the pupil dilates and contracts.
Describe the role of the nervous system in
Describe the pupil response to high light intensity Describe the pupil response to low light intensity
making responses to stimuli
• An internal or environmental stimulus is detected by
sensory cells/organs
• A nerve impulse is generated in the sensory neurone
• The nerve impulse moves towards the central nervous
o system (brain and spinal cord)
• The impulse then passes on to an effector neurone
• The effector neurone stimulates the effector
cells/organ
• A response is made by the stimulated effector
Give examples of responses using the nervous system • Light is detected by photoreceptor cells in
• Low intensity light is detected by
• Thermoregulation/ temperature homeostasis the retina
photoreceptor cells in the retina
• Control of heart rate in response to exercise • This causes high frequency of impulses to
• This causes low frequency of impulses to
• Control of breathing rate and depth in response to travel along the sensory neurones in optic
travel along the sensory neurones in optic
exercise nerve..
•
nerve..
Pupil reflex • To relay neurones in the coordinating centre
• To relay neurones in the coordinating centre
in the midbrain (CNS)
in the midbrain (CNS)
• Which cause impulses to pass along the
• Which cause impulses to pass along the
parasympathetic neurones
sympathetic neurones
• These impulses are transmitted to motor
• These impulses are transmitted to motor
neurones
neurones
• Which results in the circular muscles in the
• Which results in the radial muscles in the
iris to contract, (radial muscles relax)
iris to contract, dilating pupils, allowing
• constricting pupils, allowing less light into the
more light into the eye.
eye.
8.1 Know the structure and function of sensory, relay and motor neurones including the role of Schwann cells and myelination.
Describe the organisation of the nervous system and Describe the structure and role of different types of
Describe the structure and purpose of myelination.
role of the nervous system neurones in a reflex response
neurone role structure
Sensory ● Nerve impulse • long myelinated dendrons and
generated by axons
sensory cells • The cell body is located away from
the main axon
• dendrites, dendron, cell body and
● Pass impulses
part of axon are located outside
towards the CNS the CNS
• terminal branches are located
within the CNS
Relay ● Receive impulses • Contain many short dendrons,
from sensory each with many dendrites
neurones • Contain a single short axon, with
many terminal branches
• Located entirely within the CNS
● Pass impulses to
the effector neurone
Effector ● Receive impulses • Sometimes also called motor
from the CNS neurones
• The cell body at one end of the
neurone within CNS
● Pass impulses to • One very long axon with many
the effector organs to terminal branches
generate the
• Synapsing with the effector
response
• Axon and terminal branches
outside of CNS
Describe the role of the nervous system • The myelin sheath is specialised cells
called Schwann cells
• The nervous system can be thought of as physical
connection between distant organs/cells that need to • That are wrapped around axons to speed
communicate quickly to make a response
• They allow communication between sensors (PNS), up nerve impulses
control centres and effectors (PNS)
• Communication occurs by nerve impulses that travel
• Because they provide electrical insulation
the length of long specialised cells called neurones • Sensory and motor neurones are
• Impulses pass from sensory, to relay to motor
neurones, finally to effectors, in order to make myelinated
response
• Impulses are transmitted from neurone to the next
• Because they are long, and impulses are
across structures called synapses required to travel faster
•
, 8.2 i) Understand how the nervous systems of organisms can cause effectors to respond to a stimulus. ii) Understand how the pupil dilates and contracts.
Describe the role of the nervous system in
Describe the pupil response to high light intensity Describe the pupil response to low light intensity
making responses to stimuli
• An internal or environmental stimulus is detected by
sensory cells/organs
• A nerve impulse is generated in the sensory neurone
• The nerve impulse moves towards the central nervous
o system (brain and spinal cord)
• The impulse then passes on to an effector neurone
• The effector neurone stimulates the effector
cells/organ
• A response is made by the stimulated effector
Give examples of responses using the nervous system • Light is detected by photoreceptor cells in
• Low intensity light is detected by
• Thermoregulation/ temperature homeostasis the retina
photoreceptor cells in the retina
• Control of heart rate in response to exercise • This causes high frequency of impulses to
• This causes low frequency of impulses to
• Control of breathing rate and depth in response to travel along the sensory neurones in optic
travel along the sensory neurones in optic
exercise nerve..
•
nerve..
Pupil reflex • To relay neurones in the coordinating centre
• To relay neurones in the coordinating centre
in the midbrain (CNS)
in the midbrain (CNS)
• Which cause impulses to pass along the
• Which cause impulses to pass along the
parasympathetic neurones
sympathetic neurones
• These impulses are transmitted to motor
• These impulses are transmitted to motor
neurones
neurones
• Which results in the circular muscles in the
• Which results in the radial muscles in the
iris to contract, (radial muscles relax)
iris to contract, dilating pupils, allowing
• constricting pupils, allowing less light into the
more light into the eye.
eye.
