Neural Homeostasis Pathways (PPT 2-3) [U2/ T1]

Question 1

What is the structure of a typical neuron?

Answer 1

Include:

• cell body/ soma
• dendrites
• axon
• myelin sheath
• myelinated neurons
• unmyelinated neurons
• Schwann cells
• nodes of ranvier
• axon terminals
• synapse

Question 2

What is the function of the cell body/ soma?

Answer 2

• Where genetic material is housed
• Where dendrites connect
• Where organelles are found

Question 3

What is the function of dendrites?

Answer 3

• To receive information

Question 4

What is the function of the axon?

Answer 4

• Long single extension
• Often covered by myelin sheath
• Can be myelinated or unmyelinated

Question 5

What is the function of the myelin sheath?

Answer 5

• Fatty insulator

- Speeds up messages

Question 6

What is the function of Schwann cells?

Answer 6

• These cells make the non-continuous myelin sheath

Question 7

What is the function of the nodes of ranvier?

Answer 7

• To increase the speed of comunication.

Question 8

What is the function of the axon terminals?

Answer 8

• The axon terminates at multiple ends called axon terminals

Question 9

What is the function of the synapse?

Answer 9

• Neurons don’t connect end to end.

- The messages must jump a gap called the synapse.

Question 10

What are the 3 types of neurons?

Answer 10

• Sensory
• Relay/ Interneuron
• Motor

Question 11

What is the function, structure and location of the sensory neuron?

Answer 11

F- Activated by sensory input & send sensoy information to the brain or spinal cord

S- Receptors at the dendritic end and transmit down one axon which is in 2 parts on either side of the soma.

L- Receptors to central neuron system

Question 12

What is the function, structure and location of the interneurons/ relay neurons?

Answer 12

F- Coordinate and integration of responses

S- Multiple dendrites and axons

L- Located within the central nervous system

Question 13

What is the function, structure and location of the motor neuron?

Answer 13

F- Recieve inormation from the central nervous system & send it to the effectors. (Muscle or glands)

S- Project axons outside of CNS directly or indirectly to control muscles.

L- Located in CNS & project their axons outside effectors (Muscle or glands)

Question 14

What are the 3 steps of a stimulus response?

Answer 14

1) Receptor to control centre using the sensory neuon
2) Communication within the control centre using the interneuron/ relay neuron
3) Communication to the effector via a motor neuron

Question 15

What is the action potential?

Answer 15

The rapid changes in electrical charge across the membrane that occur when a neuron is firing.

Question 16

What are the 3 main stages action potentials occur in?

Answer 16

1) Depolarization
2) Repolarization
3) Refractory period

Question 17

What does Depolarization include?

Answer 17

• Refers to a sudden change in the membrane potential, usually from a negative to positive internal charge.
• In response to stimulus or signal, sodium channels open.
• Na ions are more concentrated outside the neruon, the opening of the channels causes a passive influx of sodium into the neruon.

Question 18

What does Repolarization include?

Answer 18

• Refers to the restoration of a membrane potential (restoring a negative internal charge)
• Following an influx of sodium, potassium channels open.
• K ions are more concentrated inside the neruon, opening of the potassium channels causes a passive movement
• The outward movement of potassium causes the membrane potential to return to a more negative internal differential.

Question 19

What does the Refractory period include?

Answer 19

• Actively moving ions to ther orignal positions (more Na outside, more K inside).
• Involves active transport and costs energy
• A Na/ K pump is used.
• Takes both time and energy, creating a lag phase where no action potentials can be sent.

Question 20

What is the sodium potassium pump?

Answer 20

• With the energy from ATP, sodium is pumped out of the cell while potassium is pumped back in.
• 3 sodium ions are moved out in one direction as 2 potassium ions are moved in.
• This restores the resting membrane potential.

Question 21

How are messages moved down the axon?

Answer 21

When Na ions diffuse into the cell, some diffuse sideways making the next region of the axon depolarized.

Question 22

What impacts the speed of transmission?

Answer 22

• Temperature
• Axon diameter
• Myelin sheath
• Voltaged-gaged ion channels are only found at the nodes of ranvier, in between is the myelin sheath. this allows the action potential to jump large distances.

Question 23

What is the all or nothing principal?

Answer 23

• The action potential only occurs if the stimulus is large enough to cause the sodium gates to open in the membrane and allow enough sodium ions to enter the cell to change the membrane potential to a certain threshold level.
• The gates are either open or closed

Question 24

What is the response of the post synaptic neuron

Answer 24

• The response of the post synaptic neuron depends largely on the nature of the cell, its location and the type of neuro transmitter thats being transported.

Question 25

Why do neurons transmit in one direction?

Answer 25

• Although axons can transmit in any direction, they transmit one direction due to the refectory period.