Chapter 4 The Nervous System

Question 1

What is an Axon?

Answer 1

An axon is the long fiber-like portion of a neuron; its purpose is to transmit an electrical signal

Question 2

What is the axon hillock

Answer 2

The axon hillock is the decision-maker of whether the signal is transmitted through the axon. It sums the signals that the soma receives

Question 3

Dendrite

Answer 3

The dendrite is the portion of a neuron that receives signals from pre-synaptic neurons

Question 4

Myelin sheath

Answer 4

Myelin is an excellent insulator and surrounds the axon to ensure that the electrical signal is not lost

Question 5

What is the soma?

Answer 5

The soma is the cell body, where the nucleus resides

Question 6

Synaptic bouton

Answer 6

This is the terminal of the axon where neurotransmitter release occurs

Question 7

Multiple neurons can be bundled together to form a…

Answer 7

Nerve

Question 8

Multiple bundles of neurons in the peripheral nervous system is called what?

Answer 8

Tract

Question 9

Which neural structure initiates an action potential?

Answer 9

The axon hillock

Question 10

What’s the difference between temporal and spatial summation?

Answer 10

Temporal summation is time-sensitive and relies on multiple signals transmitted/received in a short duration of time. Spatial summation relies on the location and sheer number of signals received

Question 11

During an action potential, which ion channel opens first?

Answer 11

Once the threshold is hit(around -55mV), the voltage-gated sodium ion channel is opened. Because there is a high concentration of sodium outside of the cell, the sodium rushes into the cell. This causes a change in the electric potential, about +35mV.

Question 12

What happens when an electric potential of +35 mV is reached?

Answer 12

The voltage-gated potassium ion channel is opened. Because there is a high concentration of potassium inside the cell, potassium rushes out, resorting the polarization but causes a bit too much polarization, around -90mV.

Question 13

During the hyperpolarization period, what is happening to restore the resting potential?

Answer 13

ATP-dependent pumps respective ions back to their original gradient locations: sodium outside of the cell and potassium inside the cell.

Question 14

During hyperpolarization period electrical signals are unable to be transduced. What are the two forms of this?

Answer 14

The refractory period; absolute and relative. Absolute is unable to be stimulated no matter what level of electric potential is reached whereas relative requires an unusually high potential to be reached.

Question 15

What are the three methods of which a neurotransmitter can be broken down?

Answer 15

1. By enzymes (breaking the chemical down)
2. By reuptake of the chemical (by the presynpatic neuron)
3. By diffusion(if the chemical is gaseous)