U2L3: Peripheral Nervous System and Neurons

Question 1

What two systems make up the Peripheral Nervous System?

Answer 1

The Autonomic system and the Somatic system.

Question 2

What is the Somatic system?

Answer 2

Usually voluntary contractions of skeletal muscles (except shivering, reflexes etc.)

Question 3

What is the Autonomic system and what 2 things is it divided into?

Answer 3

Controls mainly involuntary processes: digestion, sweat secretion, circulation of blood, smooth muscle contractions
Divided further into sympathetic & parasympathetic
Sympathetic: dominates in situations involving danger, stress, excitement, physical activity to increase heartbeat, raise bp, induce sweating, dilate pupils
Parasympathetic: dominates during quiet, low-stress situations to conserve energy so heartbeat is slowed, bp is lowered etc.

Question 4

What is a Neuron?

Answer 4

A nerve cell capable of conducting nerve impulses

Question 5

What do the Dendrites do?

Answer 5

They receive electrical stimulation from other neurons

Question 6

What does the Axon do?

Answer 6

It carries nerve impulse away from cell body

Question 7

What do the axon terminals do?

Answer 7

they transmit electrical stimulation to other neurons

Question 8

What are Sensory Neurons?

Answer 8

E.g. Those in skin
they receive sensory information & transmit the information (as a nerve impulse) to the CNS (brain & spinal cord)

Question 9

What are Motor Neurons?

Answer 9

Take information from CNS to effectors (e.g. Muscles, glands, other organs)

Question 10

What are Interneurons?

Answer 10

Link sensory & motor neurons

Question 11

What do Oligodendrocytes do (kind of non-neural cell)

Answer 11

they form the myelin sheaths of axons in CNS

Question 12

What do Schwann cells do?

Answer 12

They form a myelin sheath around each axon in PNS

Question 13

What is the Myelin Sheath (composition, function)?

Answer 13

Composed of 80% lipid + 20% protein Protects the axon and helps speed up the conduction of nerve impulses

Question 14

How are nerve signals transmitted?

Answer 14

Neurons connect to one another and transmit signals or impulses via electrical and chemical messengers

Question 15

What is Membrane potential?

Answer 15

Animal cells have a specific charge across the plasma membrane; -ve on inside and +ve on outside
Charge separation produces voltage (electrical potential diff) across membrane potential and the cell must expend ENERGY to keep this charge.
The inside of the neuron is negatively charged relative to the outside

Question 16

What is the Na-K pump?

Answer 16

Na-K pump is responsible for maintaining the charge across the membrane (ATP is used for this process)
Naturally Na+ is in high concentration outside and K+ in high concentration inside
The pump will work against the [C] gradient by pumping out 3 Na+ while pumping in 2 K+
This causes the inside of the cell to become less positive and eventually more -ve

Question 17

What is Action Potential?

Answer 17

Large stimulus reaches neuron cell and changes the membrane voltage. This causes a “domino” effect down the neuron where the electrical charge moves down the axon jumping from node to node. When the electrical charge reaches the axon terminals, chemicals called neurotransmitters are released to the next neuron, which initiates the action potential and so on…