Chapter 4: The Nervous System

Question 1

____ are specialized cells capable of transmitting electrical impulses then translating those electrical impulses into chemical signals.

Answer 1

Neurons

Question 2

Structure of a Neuron

Answer 2

Question 3

The nucleus of a neuron is found in the ____, also called the ____.

Answer 3

Cell Body

Soma

Question 4

Dendrites

Answer 4

Recieve incoming messages from the other cells.

Question 5

Axon Hillock

Answer 5

Determins if the action potential will be excited of inhibted.

Ex: If the signal is excitatory enough then it will release an action potential.

Question 6

Axons carry neural signals ___ from the somas. Dendrites carry neural signals ____ the soma.

Answer 6

Away

Toward

Question 7

Myelin

Answer 7

White fatty membrane that covers the axons of neurons.

Question 8

Myelin Sheath

Answer 8

Maintains the electrical signal within one neuron. Speeds it up.

Question 9

Myelin is produced by ____ in the central nervous system and ____ in the peropheral nervous system.

Answer 9

Oligodendrocytes

Schwann Cells

Question 10

Nodes of Ranvier

Answer 10

Small breaks in the myelin sheath that are critical for rapid signal conduction.

Question 11

Nerve Terminal

Answer 11

Structure is enlarged and flattened to maximize transmission of the signal to the next neuron and ensure the proper release of neurotransmitters.

Question 12

What is the collection of cell bodies called in the CNS? In the PNS?

Answer 12

CNS = Nucleus (Nuclei)

PNS = Ganglion (Ganglia)

Question 13

Which two types of glial cells, if not properly functioning, will make an individual most susceptible to a CNS infection?

Answer 13

• Astrocytes: nourish neurons and form the blood-brain-barrier, which helps protect the brain from foreign pathogens gaining entrance.
• Microglia: injest and break downwaste products and pathogens.
• Disruption of either of the mechanisms would increase susceptibility to a CNS infection.

Question 14

Guillain-Barre syndrome (GBS) is an autoimmune disease that causes demyelination in the peripheral nervous system. What type of glial cell is being target in the GBS?

Answer 14

Oligodendrocytes produce myelin in the central nervous system while Schwann cells produce myelin in the peripheral nervous system. Since GBS causes demyelination in the PNS, it can be inferred that Schwann Cells are targeted for immune destruction.

Question 15

Glial Cells (Neuroglia)

Answer 15

Responsible for supporting neurons by nourishment, protection, and getting rid of dead neurons.

Question 16

5 types of Glial cells and what they do.

Answer 16

1. Astrocytes: Nourish neurons and form the blood brain barrier, which controls the transmission of solutes from the blodstream into nervous tissue.
2. Ependymal: lines the centricles of the brain and produce cerebrospinal fluid, which physically supports the brain and serves as a shock absorber.
3. Microglia: Phagocytic cells that ingest and break down waste products and pathogens in the CNS.
4. Oligodendrocytes: produce myelin around axons in the CNS.
5. Schwann Cells: produce myeline around the axons in the PNS.

Question 17

Action Potential Generation

Answer 17

Question 18

What neural structure initiates the action potential?

Answer 18

The Axon Hillock

Question 19

• What entity maintains the reting membrane potential?
• What is the approximate voltage of the resting membrane potential?

Answer 19

• The resting membrane potential is maintained by the Na⁺/K⁺ ATPase.
• -70mV

Question 20

Define

• Temporal Summation
• Spatial Summation

Answer 20

• The integration of multiple signals close to each other in time.
• The integration of multiple signals close to each other in space.

Question 21

During the action potential, which ion channel opens first? How is this ion channel regulated? What effect does the opening of this channel have on the polarization of the cell?

• Ion channel:
• Regulation:
• Effect on polarization:

Answer 21

• Ion channel:
  
  • The sodium channel opens first (around -50mV).
• Regulation:
  
  • It is regulated by inactivation, which occurs around +35mV
• Effect on polarization:
  
  • Inactivation can only be reverse by repolarizing the cell. The opening of the potassium channel causes depolarizing.

Question 22

During the action potential, which ion channel opens second? How is this ion channel regulated? What effect does the opening of this channel have on the polarization of the cell?

• Ion channel:
• Regulation:
• Effect on polarization:

Answer 22

• Ion channel:
  
  • The potassium channel opens up second at approximately +35 mV.
• Regulation:
  
  • It is regulated by closing at low potentials (slightly below -70mV).
• Effect on polarization:
  
  • The opening of the potassium channel causes repolarization and, eventually, hyperpolarization.

Question 23

What is the difference between the absolute and relative refractory period?

• Absolute Refractory Period
• Relative Refractory Period

Answer 23

• Absolute Period
  
  • During the absolute refractory period, the cell is unable to fire an action potential regardless of the intensity of a stimulus.
• Refractory Period
  
  • During the relative refractory period, the cell can fire an action potential only with a stimulus that is stronger than normal.

Question 24

What ion is primarily responsible for the fusion of neurotransmitter-containing vesicles with the nerve terminal membrane?

Answer 24

Calcium is responsible for fusion of neurotransmitter vesicles with the nerve terminal membrane.

Question 25

What are the three main methods by which a neurotransmitter can be stopped?

Answer 25

1. Enzymatic degradation
2. Reuptake
3. Diffusion

Question 26

Resting membrane potential

(Definition)

Answer 26

The net electric potential difference that exist across the cell membrane, created by the movement of moelcules across the membrane.

Question 27

Potassium leak channels

Answer 27

Allows the slow leak of K+ out of the cell. As K+ continually leaks out of the cell, the cell loses a small amount of positive charge, leaving behind a small amount of negative charge and making the outside of the cell slightly positively charged.

Question 28

What is the equilibrium potential of potassium?

Answer 28

-90mV. The negative sign because potassium is moving out of the cell.

Question 29

Sodium leak channels

Answer 29

The slow leak of sodium into the cell causes a build-up of electric potential.

Question 30

What is the equilibrium potential of sodium?

Answer 30

60mV, it is positive because sodium is moving into the cell.

Question 31

K+ movement pulls the cell potential towards ____, while sodium’s movement pulls the cell potential the opposite way, towards ____. But, neither ion ever “wins” the tug of war. instead, a balance od these two effects is reached at around ____ for the average nerve cell.

Answer 31

• -90mV
• +60mV
• -70mV (resting membrane potential)

Question 32

Na⁺/K⁺ ATPase

Answer 32

• Continually pumps sodium and potassium back to where they started: K+ into the cell and sodium out of the cell, to maintain their respective gradients.

Question 33

Depolarization

Answer 33

excitatory inputs that causes the membrane potential to raise from its resting potential.

Question 34

Hyperpolarization

Answer 34

Inhibitory inputs the cause lowering of th membrane potential from its resting potential

Question 35

Impulse Propagation

Answer 35

Movement of an action potential down an axon, resulting in neurotransmitter release at the synaptic bouton and transmission of the impulse to the target neuron or organ.

Question 36

Saltatory Conduction

Answer 36

Process by which an electrical signal jumps across the Nodes of Ranvier to travel down the axon.

Question 37

• Presynaptic Neuron
• Postsynaptic Neuron

Answer 37

• Presynaptic Neuron
  
  • The neuron before the synaptic cleft
• Postsynaptic Neuron
  
  • The neuron after the synaptic cleft.

Question 38

If a neuron signals to a gland or muscle, rather than another neuron, the postsynaptic cleft is teram as an ______.

Answer 38

Effector