Nervous System
Structure and functions
Cell body
- The centre of the neurone, with a nucleus, cytoplasm
and organelles such as mitochondria
Dendrite
- Nerve fibres, like branches, which transmit nerve
impulses to the cell body; most neurons have several
dendrites
Axon
- A long single nerve fibre, which transmits nerve
impulses away from the cell body; neurones generally
only have one axon
Synapse
- The point where one neurone meets another, a
chemical messenger fills the gap between one
neurone and the next, and enables the impulse to be
transmitted
Neurilemma
- A fine, delicate membrane which surrounds the myelin
sheath and helps regenerate nerve cells; only found in
peripheral nerves and not in the brain or spinal cord
Nodes of Ranvier
- These are gaps in the myelin sheath along the nerve,
they speed up the passage of nerve impulses along the
fibre
End feet/axon terminals
- The ends of the fibrils (tiny fibres) that make the axon are expanded, they pass on the axon impulse
to the dendrites of the next neurone
Myelin sheath
- Made of a white, fatty substance, this sheath covers the axon
Motor neurone
- Carry impulses from the brain or spinal cord to muscles or glands which then act on the
information/instruction, producing movement or a secretion
Sensory nerve
- Carry impulses from all parts of the body to the brain
Mixed nerve
- Carry both motor and sensory nerve fibres, only found in the spinal cord (spinal nerves) and the
brain (cranial)
White matter
- On the inside of the brain and the outside of the spinal cord, made of bundles of myelinated nerve
fibres
Grey matter
- On the outside of the brain and inside of the spinal cord, made of cell bodies and unmyelinated
axons and dendrites
Central Nervous System
Brain
- Consists of several thousand nerve cells and processes lying within the skull, it co-ordinates the
nerve stimuli received and effect the correct response.
- Surrounded by three membranes
1. Dura mater: outer layer protective fibrous connective tissue sheath
Structure and functions
Cell body
- The centre of the neurone, with a nucleus, cytoplasm
and organelles such as mitochondria
Dendrite
- Nerve fibres, like branches, which transmit nerve
impulses to the cell body; most neurons have several
dendrites
Axon
- A long single nerve fibre, which transmits nerve
impulses away from the cell body; neurones generally
only have one axon
Synapse
- The point where one neurone meets another, a
chemical messenger fills the gap between one
neurone and the next, and enables the impulse to be
transmitted
Neurilemma
- A fine, delicate membrane which surrounds the myelin
sheath and helps regenerate nerve cells; only found in
peripheral nerves and not in the brain or spinal cord
Nodes of Ranvier
- These are gaps in the myelin sheath along the nerve,
they speed up the passage of nerve impulses along the
fibre
End feet/axon terminals
- The ends of the fibrils (tiny fibres) that make the axon are expanded, they pass on the axon impulse
to the dendrites of the next neurone
Myelin sheath
- Made of a white, fatty substance, this sheath covers the axon
Motor neurone
- Carry impulses from the brain or spinal cord to muscles or glands which then act on the
information/instruction, producing movement or a secretion
Sensory nerve
- Carry impulses from all parts of the body to the brain
Mixed nerve
- Carry both motor and sensory nerve fibres, only found in the spinal cord (spinal nerves) and the
brain (cranial)
White matter
- On the inside of the brain and the outside of the spinal cord, made of bundles of myelinated nerve
fibres
Grey matter
- On the outside of the brain and inside of the spinal cord, made of cell bodies and unmyelinated
axons and dendrites
Central Nervous System
Brain
- Consists of several thousand nerve cells and processes lying within the skull, it co-ordinates the
nerve stimuli received and effect the correct response.
- Surrounded by three membranes
1. Dura mater: outer layer protective fibrous connective tissue sheath
