Neurons and synaptic transmission

Question 1

What are neurons?

Answer 1

Cells that are specialised to carry neural information throughout the body

Question 2

What are three types of neurons?

Answer 2

Sensory
Relay
Motor

Question 3

How do the three types of neuron interact?

Answer 3

Dendrites at one end of the neutron are connected to the cell body (the control centre of the neutron), then impulses is carried along the axon where it terminates at the axon terminal (axons have an insulating layer - the myelin sheath - allows nerve pulses to travel more rapidly along the axon)
Sensory>relay>motor

Question 4

What are sensory neurons?

Answer 4

• Carry nerve impulses from sensory receptors (i.e. eyes, ears, tongue) to the spinal cord and brain
• When they reach the brain, they are translated into sensations of, for example, visual input, heat, pain so that the organism can react appropriately
• Not all sensory info travels to brain, some only reach spinal cord to allow for quick reflex actions

Question 5

What are relay neurons?

Answer 5

Lie between sensory input and motor output and allows for them to communicate
- wholly within brain and spinal cord

Question 6

What are motor neurons?

Answer 6

• Nerve cells that carry messages from CNS to muscles and glands, causing them to take action (like contracting a muscle)
• Cell bodies in CNS but have long axons that form part of PNS
• Motor neurons form synapses with muscles and control their contractions - when stimulated the motor neuron releases neurotransmitters that bind to receptors on the muscle and triggers a response resulting in muscle movement

Question 7

What is the action potential?

Answer 7

Information is passed down the axon of the neuron as an electrical impulse known as action potential. Once the action potential reaches the end of the axon it needs to be transferred to another neuron or tissue.

Question 8

Explain the process of synaptic transmission

Answer 8

1) The electrical signal (action potential) reaches the end of the pre-synaptic neuron
2) As action potential reaches the synaptic vesicles, it causes them to releases their contents through a process called exocytosis, neurotransmitters are released from the pre-synaptic neuron into the synapse.
3) They travel across the synaptic gap to the post-synaptic neuron.
4) Neurotransmitters bind to receptors on the post-synaptic neuron
5) The post-synaptic neuron is either excited or inhibited, potentially firing an action potential
6) Effects terminated at most synapses by a process called re-uptake (stored and made available for later use)

Question 9

What are excitatory neurotransmitters?

Answer 9

They increase the likelihood that an excitatory signal is sent to the postsynaptic cell, which is then more likely to fire

Question 10

What are inhibitory neurotransmitters?

Answer 10

Decrease the likelihood of a neuron firing ‘off switches’