Neuron Biology

Question 1

What are the 4 basic elements in the structure of a neuron?

Answer 1

• Dendrite - recieves signals
• Soma - processes information
• Axon - transmits between neurons
• Synapse - point of connection between neurons.

Question 2

Describe the structure and function of the Dendrite? (3)

Answer 2

1. Tree like structure that gathers input from surrounding neurons.
2. Mushroom shaped spines cover the dendrite and recieve input from other axons.
3. Recieved signals travel to the SOMA.

Question 3

Describe the structure and function of the Soma? (2)

Answer 3

1. Soma houses the DNA of the neuron.
2. Accumulates signals from dendrites and causes the nueron to fire down the axon if they exceed a threshold. This occurs in the axon hilock.

Question 4

Describe the structure and function of an Axon?

Answer 4

1. An axon is a tube-like nerve fiber that carries signals to the axon terminals.
2. Axons coated in myelin are protected and their signals travel faster.

Question 5

What are the three classes of neuron?

Answer 5

• Sensory Nuerons
• Motor Neurons
• Relay Neurons

Question 6

What is the role of sensory neurons?

Answer 6

Tell the brain what is happening outside the body.

Question 7

What is the role of Motor Neurons?

Answer 7

Allow the brain to control muscles

Question 8

What are the role of relay neurons?

Answer 8

Allow sensory and motor neurons to communicate.

Question 9

What are the main parts of the CNS?

Answer 9

The brain and spinal cord.

Question 10

What is the cell membrane of an Axon?

Answer 10

The cell membrane of an axon is a double layer of lipids which sperates the inside of the cell with the outside.

Question 11

What is the membrane potential?

Answer 11

Ions on either side of the membrane are unequally distributed causing a potential.

Question 12

What is the resting potential?

Answer 12

The potential across the membranes which do not cause the neuron to fire. Typically (-70mV)

Question 13

What are the membrane channels?

Answer 13

Allow ions to travel from one side of the membrane to another

Question 14

What are leaky channels?

Answer 14

Always open and allow sodium and pottasium ions through.

Question 15

What are voltage gated channels?

Answer 15

Only open when the voltage is high enough. Normally closed at resting potential.

Question 16

Why is resting potential -70mV instead of 0?

Answer 16

• There are more pottasium ions in the cell which allows pottassium ions to travel through the pottasium leaky channels easier.
• There is a sodium potassium pump which uses energy to move three sodium ions for ever 2 pottasium ions.

Question 17

What is an action potential?

Answer 17

The change in potential which travels across the neuron. Occurs at -55mV.

Question 18

What is the All-or-None law?

Answer 18

Subthreshold stimulus will cause no excitation. Superthreshold stimus will cause full excitation.

Question 19

What is polarisation?

Answer 19

If the outside of the membrane is positive and the inside is negative.

Question 20

What is HyperPolarisation?

Answer 20

If the membrane potential is more negative than resting.

Question 21

what is depolarisation?

Answer 21

if the membrane potential is more positive than resting.

Question 22

What are the 6 steps of action potential?

Answer 22

1. Initially at resting potential, volted gated channels are closed.
2. Stimuli causes some volted gated channels to open.
3. Sodium channels open, causes sodium to rush into the cell causing depolarisation as voltage exceeds 30mv.
4. Voltage gated sodium channels close.
5. Pottassium channels open, causing repolarisation to occur as pottasium leaves the cell.
6. Sodium and pottassium pump restore the resting potential.

Question 23

What is a synapse?

Answer 23

Junction between nerve/muscle cells.

Question 24

Describe Synaptic transmission?

Answer 24

1. When the presynaptic neuron is exicted by an action potential.
2. Vesicles in the axon terminals release neurotransmiiters into the synaptic cleft.
3. Some neurotransmitters will bind to receptors in the postsynaptic cell causing some effect. (some nuero transmitters are excitory or inhibitory.)

Question 25

Describe the types of synaptic connections?

Answer 25

1. Axodendritic - axon terminal links to dendrite
2. Axosomatic - axon terminal links to the soma.
3. Axoaxonal - axon terminal links to axon.
4. Dendrodendrititc - Dendrite links to dentrite.