Neurones

Stimulus

Changes in internal and external environment

Is neuronal or hormonal response quicker?

Neuronal (generally)

Role of neurones

To transmit electrical impulses rapidly around body so the organism can respond to changes in its internal and external environment

What does neurone cytoplasm contain?

• ER and mitochondria (involved in producing neurotransmitters)

Dendrons

• Come from cell body

• Responsible for transmitting electrical impulses towards cell body

Axons

• Singular, elongated nerve fibres

• Transmit impulses away from cell body

Sensory neurones

• Transmit impulses from sensory receptor cell to relay neurone, motor or brain

• 1 dendron, 1 axon, myelin sheath

Relay neurone

• Transmit impulses between neurones

• Many short axons & dendrons

Motor neurones

• Transmit impulses from relay or sensory to effector

• 1 long axons, many short dendrites, myelin sheath

What produces myelinated sheath?

• Schwann cells

  • Produces many layers of plasma membrane

Myelin sheath

• Acts as insulating layer ; is electrical insulator

• Allows conduction of electrical impulse at faster speeds

Node of Ranvier

• Gaps in myelin sheath

• Electrical impulse ‘jumps’ from 1 node to next

  • Allows faster transmission of impulse