, Topic 1: Introduction to the Nervous System
❖ Name the parts of a generalised neuron & indicate the input, output and integration areas of
the neuron.
➢ Neurons are the functional cell
of the nervous system that
transmit electrochemical
messages called nerve impulses
or action potentials to other
neurons and effectors (muscles
or glands).
Parts of a neuron:
➢ Cell body (or soma): contains
relatively large nucleus with
a prominent nucleolus and
produces proteins needed for other parts of the neuron. Cluster of cell bodies = ganglia.
➢ Dendrites: [INPUT] highly branched ‘finger-like’ projections that receive information
from other neurons.
➢ Axons: [INTEGRATION] long nerve fibres that are capable of propagating electrical impulses
known as action potential through them from cell body to axon terminal (*Electrical
impulses rarely travel the other way). Cluster of neuron axons = nerves
➢ Axon terminal: [OUTPUT] nerve endings that make synaptic contacts with other neurons
and effector cells, they also contain various kinds of neurotransmitters (chemicals which
convey the message across the synaptic space).
,➢ Myelin sheath: the insulating cover of axons which increases the speed at which electrical
impulses travel along the neuron (*Not all neurons have a myelin sheath, only the ones
that need fast electrical impulses).
➢ A single neuron integrates it many inputs (inhibitory or excitatory) to produce a single
output response (action potential or nerve impulse).
o This allows: large amounts of info to be processed very quickly and acted upon.
List the roles of glial cells in the nervous
Ependymal
system cells
The nervous system also contains specialised
Glial cells which protect and support neurons.
There are four types of neuroglia:
Astrocytes:
o Structural support Neurons
o Formation of scar tissue Transport
Microglial
o of substances between blood cell Capillary
vessels and neurons
Astrocyte
o Communication with one another
and with neurons
e
, o Mop up excess ions and neurotransmitters
o Induce synapse formation.
➢ Oligodendrocytes:
o Form myelin sheaths in the brain and spinal cord (e.g. multiple sclerosis =
myelin sheath deteriorates and signals slower)
o Produce nerve growth factors
➢ Microglia:
o Structural support
o Phagocytosis (immune protection as normal body immune cells don’t get into the CNS).
➢ Ependymal cells:
o Form a porous layer through which substances diffuse between the interstitial fluid
of the brain and spinal cord and the cerebrospinal fluid.
❖ Explain in broad terms, what a membrane potential is, and what is required for it to exist.
➢ All cells have a membrane potential, which is a difference in charge between the inside
and outside of cells.
➢ Only nerve cells and muscle cells can rapidly change their membrane potential as a means
of creating a signal. This means these are excitable cells.
➢ In rest state the inside of nerve cells are negative in respect to the outside of cells.
➢ The voltage arises from differences in concentration of the electrolyte ions K+ and Na+.
➢ Specific sodium channels and potassium channels are intrinsic to the membrane
and selectively close and open to allow the passage of these ions across the
membrane.
➢ At rest, sodium channels are mostly closed and potassium channels open, so potassium
moves down the concentration gradient (out of the cell), making is less negative to the
outside.
➢ This is known as resting membrane potential.
➢ The concentration gradient is maintained by active transport (using ATP) of sodium ions out
of cell and potassium ions in.
➢ Known as the sodium-potassium pump.
❖ Describe how depolarisation and repolarisation are achieved in a neurone.
➢ Depolarisation is what allows neurons to signal, which is the rapid reversal of the
membrane potential from its rest state.
➢ Thus, where the sodium channels are open allowing sodium ions into the cell making it
positive to the outside.
➢ After the signal, repolarisation occurs,
where sodium channels close and
potassium channels open allowing
potassium to move out of cell and stop
sodium moving into cell, creating a
resting membrane potential again
(negative inside).
➢ A “wave” of depolarisation and
repolarisation moves rapidly along the
axon
of neurones and more sodium channels open and close. ➢ This process is known as nerve
❖ Name the parts of a generalised neuron & indicate the input, output and integration areas of
the neuron.
➢ Neurons are the functional cell
of the nervous system that
transmit electrochemical
messages called nerve impulses
or action potentials to other
neurons and effectors (muscles
or glands).
Parts of a neuron:
➢ Cell body (or soma): contains
relatively large nucleus with
a prominent nucleolus and
produces proteins needed for other parts of the neuron. Cluster of cell bodies = ganglia.
➢ Dendrites: [INPUT] highly branched ‘finger-like’ projections that receive information
from other neurons.
➢ Axons: [INTEGRATION] long nerve fibres that are capable of propagating electrical impulses
known as action potential through them from cell body to axon terminal (*Electrical
impulses rarely travel the other way). Cluster of neuron axons = nerves
➢ Axon terminal: [OUTPUT] nerve endings that make synaptic contacts with other neurons
and effector cells, they also contain various kinds of neurotransmitters (chemicals which
convey the message across the synaptic space).
,➢ Myelin sheath: the insulating cover of axons which increases the speed at which electrical
impulses travel along the neuron (*Not all neurons have a myelin sheath, only the ones
that need fast electrical impulses).
➢ A single neuron integrates it many inputs (inhibitory or excitatory) to produce a single
output response (action potential or nerve impulse).
o This allows: large amounts of info to be processed very quickly and acted upon.
List the roles of glial cells in the nervous
Ependymal
system cells
The nervous system also contains specialised
Glial cells which protect and support neurons.
There are four types of neuroglia:
Astrocytes:
o Structural support Neurons
o Formation of scar tissue Transport
Microglial
o of substances between blood cell Capillary
vessels and neurons
Astrocyte
o Communication with one another
and with neurons
e
, o Mop up excess ions and neurotransmitters
o Induce synapse formation.
➢ Oligodendrocytes:
o Form myelin sheaths in the brain and spinal cord (e.g. multiple sclerosis =
myelin sheath deteriorates and signals slower)
o Produce nerve growth factors
➢ Microglia:
o Structural support
o Phagocytosis (immune protection as normal body immune cells don’t get into the CNS).
➢ Ependymal cells:
o Form a porous layer through which substances diffuse between the interstitial fluid
of the brain and spinal cord and the cerebrospinal fluid.
❖ Explain in broad terms, what a membrane potential is, and what is required for it to exist.
➢ All cells have a membrane potential, which is a difference in charge between the inside
and outside of cells.
➢ Only nerve cells and muscle cells can rapidly change their membrane potential as a means
of creating a signal. This means these are excitable cells.
➢ In rest state the inside of nerve cells are negative in respect to the outside of cells.
➢ The voltage arises from differences in concentration of the electrolyte ions K+ and Na+.
➢ Specific sodium channels and potassium channels are intrinsic to the membrane
and selectively close and open to allow the passage of these ions across the
membrane.
➢ At rest, sodium channels are mostly closed and potassium channels open, so potassium
moves down the concentration gradient (out of the cell), making is less negative to the
outside.
➢ This is known as resting membrane potential.
➢ The concentration gradient is maintained by active transport (using ATP) of sodium ions out
of cell and potassium ions in.
➢ Known as the sodium-potassium pump.
❖ Describe how depolarisation and repolarisation are achieved in a neurone.
➢ Depolarisation is what allows neurons to signal, which is the rapid reversal of the
membrane potential from its rest state.
➢ Thus, where the sodium channels are open allowing sodium ions into the cell making it
positive to the outside.
➢ After the signal, repolarisation occurs,
where sodium channels close and
potassium channels open allowing
potassium to move out of cell and stop
sodium moving into cell, creating a
resting membrane potential again
(negative inside).
➢ A “wave” of depolarisation and
repolarisation moves rapidly along the
axon
of neurones and more sodium channels open and close. ➢ This process is known as nerve
