Biopsychology - Nerves and synaptic transmission

Question 1

What are the three neurones in the reflex arc?

Answer 1

• Sensory neurones
• Relay neurones
• Motor neurones

Question 2

What is the process of the reflex arc?
[Stimulus   ]
[Receptor  ]
[Sensory    ]
[Synapse   ]
[Relay        ]
[Synapse   ]
[Motor       ]
[Effector    ]
[Response]

Answer 2

• A stimulus is detected by receptors on a sensory neurone
• An electrical signal travels across the neurone to the axon terminal
• It is then converted to a chemical signal to cross the synapse to be detected by the relay neurone which is located in the spine
• The signal is then passed immediately to the motor neurone
• The signal passes the motor neurone and it goes to the effector (Muscle fibre)
• This, then causes the response (the muscle moves out of danger)

Question 3

What is the synapse?

Answer 3

The point where one neuron (presynaptic) can send a chemical message to an adjacent neuron (postsynaptic)

Question 4

How does information travel through the neuron and how does this change when it reaches the synapse?

Answer 4

• Information travels through the neuron as an electrical impulse known as an action potential
• At a synapse the electrical impulse cannot cross from the axon terminal to the adjacent dendrite so the action potential is sent as chemical message

Question 5

What is the process of synaptic transmission?

Answer 5

1) An action potential arrives at the axon terminal
2) This causes the vesicles to merge with the membrane of the presynaptic cell
3) Neurotransmitters are released into the synaptic cleft
4) The neurotransmitters diffuse across the synaptic cleft reaching the postsynaptic cell
5) Receptors on the postsynaptic neurone’s dendrite membrane detects the presence of neurotransmitters. If a threshold potential is met, the action potential can be sent into the post synaptic neurone
6) Summation (the sum of the excitatory and inhibitory neurotransmitters), depolarisation caused from the excitatory neurotransmitters must occur in order for the new electric action potential to be formed in the post synaptic cell, the electrical charge must pass the threshold
7) The new action potential is formed and it travels
down the axon of the post synaptic neurone
8) The neurotransmitters detach from the receptors and return to the presynaptic cell via transport proteins, this process is called reuptake

Question 6

What is an excitatory neurotransmitter?

Answer 6

• A chemical messenger that increases the likelihood of a new AP forming in the post-synaptic cell
• When detected by receptors the electrical charge inside becomes more positive and likely to fire (Depolarisation)

Question 7

What is an inhibitory neurotransmitter?

Answer 7

• A chemical messenger that decreases the likelihood of a new AP forming in the post-synaptic cell
• When detected by receptors the electrical charge inside becomes more negative and less likely to fire (Hyperpolarisation)