Neurones & The Adaptations Of Neurones:
Neurones are specialised cells that transmit an action potential
from one part of the body to another.
Dendrites are the small extensions of the cell body that create a
large surface area, carrying impulses towards the cell body.
Axons are the single long fibre that carries electrical impulses
away from the cell body.
Adaptations of neurones:
o Long – transmit action potentials over a long distance.
o Sodium-potassium pumps – actively transport sodium out
of the cell and potassium into the cell (uses ATP).
o Gated ion channels – control entry/exit of sodium/
potassium/ calcium ions.
o Organelles in cell body – mitochondria, nucleus,
ribosomes, ER for production of neurotransmitters.
o Myelin sheath – fatty sheath insulates neurone from
other electrical activity (20-30 layers of Schwann cell
membrane).
Myelinated neurones:
o Have Schwann cells wrapped around the axon many
times.
o There are gaps between Schwann cells called nodes of
Ranvier (these occur every 1-3mm in humans).
o Myelination speeds up conduction 100 times by allowing
for long local currents (saltatory conduction) along the
neurone.
o This is where depolarisation only occurs at the, nodes &
so the action potential appears to “jump” from node to
node.
Neurones are specialised cells that transmit an action potential
from one part of the body to another.
Dendrites are the small extensions of the cell body that create a
large surface area, carrying impulses towards the cell body.
Axons are the single long fibre that carries electrical impulses
away from the cell body.
Adaptations of neurones:
o Long – transmit action potentials over a long distance.
o Sodium-potassium pumps – actively transport sodium out
of the cell and potassium into the cell (uses ATP).
o Gated ion channels – control entry/exit of sodium/
potassium/ calcium ions.
o Organelles in cell body – mitochondria, nucleus,
ribosomes, ER for production of neurotransmitters.
o Myelin sheath – fatty sheath insulates neurone from
other electrical activity (20-30 layers of Schwann cell
membrane).
Myelinated neurones:
o Have Schwann cells wrapped around the axon many
times.
o There are gaps between Schwann cells called nodes of
Ranvier (these occur every 1-3mm in humans).
o Myelination speeds up conduction 100 times by allowing
for long local currents (saltatory conduction) along the
neurone.
o This is where depolarisation only occurs at the, nodes &
so the action potential appears to “jump” from node to
node.
