Nervous system 2

Question 1

What is the Nervous System?

Answer 1

A network of billions of neurons and even more neuroglia that is organised into 2 main divisions.

Question 2

What are the 2 main divisions of the Nervous System and where they operate?

Answer 2

Central Nervous System (CNS)
- brain
- spinal cord
Peripheral Nervous System (PNS)
- nerves
- ganglia
- enteric plexuses
- sensory receptors outside the CNS

Question 3

What are the 3 parts of the Peripheral Nervous System?

Answer 3

Somatic Nervous System (SNS)
Autonomic Nervous System (ANS)
Enteric Nervous System (ENS)

Question 4

What is the Autonomic Nervous system? What are its 2 main divisions?

Answer 4

• part of the PNS that conveys output to smooth muscle, cardiac muscle and glands
• automatic control, involuntary actions due to stimulus

Sympathetic Nervous System:
- fight or flight response
Parasympathetic Nervous System:
- rest and digest response

Question 5

What is the Somatic Nervous System?

Answer 5

• a control that we exert
• part of the PNS that conveys output to the skeletal muscles

Question 6

What is the Enteric Nervous System? What is an example?

Answer 6

• a large division of the PNS that can control GI behavior independently of the CNS input.
  EXAMPLE:
  The second brain of the enteric nervous system is the reason we get butterflies in our stomach or need to use the restroom more frequently when we are nervous or stressed.

Question 7

What is an action potential?

Answer 7

• an electrical signal that propagates alone the membrane of a neuron or muscle fiber
• a rapid change in membrane potential that involves a depolarisation followed by a repolarization.

Question 8

What are the steps involved in an action potential taking place?

Answer 8

1. a stimulus causes a rapid change in the membrane potential, resulting in reaching the threshold potential of -55mV
2. depolarisation occurs due to the influx of sodium ions into the cell, resulting in a more positive membrane potential of about +40mV
3. an action potential is fired when the membrane potential reaches +40mV. Repolarisation occurs as potassium ions leave the cell and the membrane potential becomes negative again.
4. hyperpolarisation is the result of the efflux of potassium ions, whereby the membrane potential becomes more negative (around -90mV)
5. resting state is reached when the membrane potential returns to the resting voltage of -70mV. This is achieved by the movement of potassium and sodium ions in and out of the cell.