Nervous coordination and muscles
Neurones and nervous coordination
The two main forms of coordination in animals:
- The nervous system
- The hormonal system
Neurones
Neurones (nerve cells) are specialised cells adapted to rapidly carrying electrochemical
changes called nerve impulses from one part of the body to another.
A mammalian motor neurone is made up of:
- cell body- contains all the usual cell organelles, including a nucleus and large
amounts of rough endoplasmic reticulum; this is associated with the production of
proteins and neurotransmitters.
- Dendrons- extensions of the cell body which subdivide into smaller branched fibres,
called dendrites, that carry nerve impulses towards the cell body.
- Axon- a single long fibre that carries nerve impulses away from the cell body.
- Schwann cells- Surround the axon, protecting it and providing electrical insulation.
They also carry out phagocytosis (the removal of cell debris) and play a part in nerve
regeneration. They wrap themselves around the axon many times, so that layers of
their membranes build up around it.
- Myelin sheath- forms a covering to the Axon and is made up of the membranes of
the Schwann cells. These membranes are rich in a lipid known as myelin.
- nodes of Ranvier- constrictions between adjacent Schwann cells where there is no
myelin sheath.
Types of neurones:
- sensory neurone- transmit nerve impulses from receptor to an intermediate or
motor neurone.
- motor neurone- transmit nerve impulses from an intermediate or relay neurone to
an effector, such as a gland or a muscle.
- Intermediate or relay neurone- transmit impulses between neurones, for example
from sensory to motor neurones.
,
Neurones and nervous coordination
The two main forms of coordination in animals:
- The nervous system
- The hormonal system
Neurones
Neurones (nerve cells) are specialised cells adapted to rapidly carrying electrochemical
changes called nerve impulses from one part of the body to another.
A mammalian motor neurone is made up of:
- cell body- contains all the usual cell organelles, including a nucleus and large
amounts of rough endoplasmic reticulum; this is associated with the production of
proteins and neurotransmitters.
- Dendrons- extensions of the cell body which subdivide into smaller branched fibres,
called dendrites, that carry nerve impulses towards the cell body.
- Axon- a single long fibre that carries nerve impulses away from the cell body.
- Schwann cells- Surround the axon, protecting it and providing electrical insulation.
They also carry out phagocytosis (the removal of cell debris) and play a part in nerve
regeneration. They wrap themselves around the axon many times, so that layers of
their membranes build up around it.
- Myelin sheath- forms a covering to the Axon and is made up of the membranes of
the Schwann cells. These membranes are rich in a lipid known as myelin.
- nodes of Ranvier- constrictions between adjacent Schwann cells where there is no
myelin sheath.
Types of neurones:
- sensory neurone- transmit nerve impulses from receptor to an intermediate or
motor neurone.
- motor neurone- transmit nerve impulses from an intermediate or relay neurone to
an effector, such as a gland or a muscle.
- Intermediate or relay neurone- transmit impulses between neurones, for example
from sensory to motor neurones.
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