Synapse and transmission of nerve impulse, all or none character of nerve impulse, transmission of excitatory state from nerve to effectors tissue

Neurons

• Structural and functional unit of nervous system
• Neurons initiates and transmits nerve impulse to other cell
• Neurons are present in CNS, PNS and sensory organs
• Neurons consists of Dendrites, cell body, axon

Structure of neuron

Primarily, contains dendrites, cell body and axon.

a. Dendrites

• Numerous, small, wide, fine branched like structure
• Carry impulse towards cell body

b. Cell body

• Core part of neuron
• Give rise to dendrites and axon
• Contain nucleus and other organelles
• Neurofibrils help to pass impulse to and from the cell body

c. Axon

• Single long processes
• Conduct impulse away from cell body
• Communicate with other neurons through synapse.

d. Terminal end

• Terminal part of axon which is neurosecretory in function.

      #note

Myelinated nerve fibre:

• Axon surrounded by nerve fibre
• Sheath are interrupt at regular interval called node of ranvier
• Conduct nerve impulse at high speed

Non myelinated nerve fibre:

• Myelin sheath is absent
• Conduct nerve impulse at slower rate