Neurons and synaptic transmission

What do neurons do

transmit signals electronically and chemically, provides the NS with its primary means of communication

types of neurons

1. Sensory

2. Relay

3. Motor

Sensory neurons

• found in receptor cells in the PNS

• Carry nerve impulses to spinal cord and brain

• Nerve impulses translated into ‘sensations’

• Not all sensory neurons reach the brain, some stop at spinal cord allowing for reflex action

Sensations examples

vision, hearing, taste, touch

relay neurons

• found in between sensory input and motor response

• Found in the brain and spinal cord

• Allow sensory and relay neurons to communicate

Motor neurons

• found in central nervous system (CNS)

• Control muscle movement

• When stimulated, they release neurotransmitters that bind to the receptors on muscles to trigger a response

Parts of a neuron

1. Dendrites

2. Cell body

3. Axon

4. Myelin sheath

5. Axon terminal

Role of dendrites

• receive signals from other neurons or from sensory receptor

• typically connected the cell body which is referred to as the ‘control centre’ of the neuron

Role of cell body

• also known as soma

• Core section of the neuron

• Provides energy to drive activities and contains the nucleus which houses the cells genetic information

Role of axon

• a long slender fibre that carries nerve impulses, in a form of an electrical signal

  • Known as action potential

• Impulse is carried away from the cell body towards the axon terminal

Role of myelin sheath

• insulates the axon so that electrical impulses travel faster along the axon

Role of axon terminal

• connects the neuron to other neurons

• Process called synaptic transmission where chemical messages are passed across the synapse between neurons

Synaptic transmission

1. Information passed down the axon of the neuron as an electrical impulse known as action potential

2. Once the action potential reaches the end of the axon it needs to be transferred to another neuron or tissue, by crossing the synaptic gap

3. At the end of the neuron (axon terminal) are synaptic vesicles which contain neurotransmitters

4. The electrical impulses stimulates the release of the neurotransmitters from the synaptic vesicle

Synaptic transmission pt

5. Neurotransmitters then carry signal across the synaptic gap

6. They bind to receptor sites on postsynaptic cell which then become activated

7. Once the receptors on the post-synaptic neuron have been activated, they either produce excitatory or inhibitory effects on the post-synaptic cell

Excitatory neurotransmitters

make the neighbouring neuron more likely to fire by creating positive charge

Inhibitory neurotransmitters

makes the neighbouring neuron less likely to fire by creating a negative charge