Neurones+synaptic transmission+excitation and inhibition

Question 1

Neurones

Answer 1

-Neurones are nerve cells that transmit chemical and electrical signals throughout the nervous system

Question 2

Sensory neurones function and direction

Answer 2

-Carries information from sensory receptors (e.g the skin, the eyes) to the central nervous system
-From the PNS to the CNS

Question 3

Sensory neurones structure and purpose of structure

Answer 3

-Long dendrites- to colect signals from receptors
-Short axon- messages only have to reach the spinal cord or the brain
-Cell body is outside of the CNS and outside of the axon

Question 4

Relay neurones function and direction

Answer 4

-Relay neurones connect the sensory neurone to the motor neurone
-Always found in the CNS

Question 5

Relay neurones structure and purpose of structure

Answer 5

-Short dendrites- recieves signals from the sensory neurone
-Short axon- transmits signals to the motor neurone
-Cell body is located in the middle of the neurone

Question 6

Motor neurones function and direction

Answer 6

-Motor neurones carry information from the central nervous system to effectors (e.g muscles)
-CNS to the body (effectors)

Question 7

Motor neurones structure and purpose of structure

Answer 7

–Motor neurons have a short dendrite - as it receives information from the sensory neuron
-Motor neurons also have a long axon- as they transmit their signal to effectors
-Motor neurones have a cell body at one end of the axon, in the CNS

Question 8

Synaptic transmission

Answer 8

-Synaptic transmission is the process by which neurons communicate with each other through chemical messages across the synapse

Question 9

Process of synaptic transmission

Answer 9

1. Electrical impulse (action potential) travels down the length of the neuron
2. When the impulse reaches the axon terminal, it triggers the release of neurotransmitters
3. Neurotransmitters are stored in vesicles in the pre-synaptic terminal
4. The vesicles move towards the edge of the pre-synaptic cell (towards the membrane) and release the neurotransmitters into the synaptic cleft via exocytosis
5. The neurotransmitters diffuse across the synaptic cleft and bind to complementary receptors on the post-synaptic membrane
6. The chemical message will be converted to an electrical impulse (generated an action potential) if the threshold potential is reached
7. The neurotransmitters that are still left in the synaptic cleft are reabsorbed into the pre-synaptic neuron via reuptake or enzymes in the synapse break the neurotransmitters down to prevent further stimulation of the post synaptic membrane

Question 10

Excitatory neurotransmitters

Answer 10

-Excitatory neurotransmitters (e.g adrenaline) increase the likelihood of the post synaptic neurone firing an impulse
-They cause a positive charge in the neurone (depolarisation), bringing it closer to the threshold potential

Question 11

Inhibitory neurotransmitters

Answer 11

-Inhibitory neurotransmitters reduce the likelihood of the postsynaptic neurone firing an impulse
-They cause a negative charge (hyperpolarisation) in the neuron, making it more difficult to reach the threshold potential
-For example: GABA; which slows down the central nervous system, providing a general sense of relaxation