Exam 4 | Nervous system pt. 1

Question 1

What’s the neuron?

Answer 1

The neuron is the primary cell type found in the central nervous system.

Question 2

What do all neurons exhibit?

Answer 2

Electrical properties meaning that they are capable of propagating electrical signals

Question 3

What’s the cell body?

Answer 3

Sometimes called the soma; it houses the nucleus and other membrane-bound organelles

Question 4

What are dendrites?

Answer 4

They’re spiny projections that receive signals from neighboring neurons and cells

Question 5

What’s an axon?

Answer 5

An axon is a long projection that extends away from the cell body in order to relay electrical signals; it’s relayed in 1 direction

Question 6

What are synaptic terminals?

Answer 6

This is where neurotransmitters are released into an empty space called the synapse

Question 7

Describe unipolar neurons.

Answer 7

They have no dendrites and a single axon; these neurons aren’t too common in the CNS and can be found in the olfactory bulb

Question 8

Describe bipolar neurons.

Answer 8

These nurons have 2 separate axons going in opposite directions; almost exclusively sensory neurons like the retina

Question 9

Describe pseudounipolar neurons.

Answer 9

Similar to unipolar neurons in that they only have a single projection (axon), however, this projection extends in either direction, similar to the morphology of bipolar neurons; lacks a myelin sheath; found in dorsal horns of spinal cord where pseudounipolar somatosensory neurons are located

Question 10

Describe multipolar neurons.

Answer 10

They exhibit all the traditional neuronal cell structures like dendrites, a cell body, an axon and synaptic terminals; the largest in the entire CNS being the pyramidal cells, which get their name from their pyramid-shaped cell body.

Question 11

What’s an interneuron?

Answer 11

Found exclusively in the spinal cord; these neurons often exist at the “intersection” between two sensory neurons, two motor neurons, or one sensory and one motor neuron, in order to help regulate reflexes and other behavioral responses. In addition, these interneurons are almost exclusively inhibitory in their signaling

Question 12

What’s Ohm’s law?

Answer 12

Ohm’s law allows us to understanding how electrical current flows through a neuron (and specifically, how this current propagates down the axon of the neuron).

Question 13

What’s voltage?

Answer 13

It’s an uneven distribution of electrons (charge differences between the extra- and intra- cellular side of the neuron); this creates an electromotive force

Question 14

What is current (I)?

Answer 14

This is the movement of electrons; the movement of cations in the neuron that generates an electrical current; moves in 1 direction

Question 15

What’s resistance?

Answer 15

There’s 2 types:

1) membrane resistance is the difference across neuron cell membrane, and myelination lowers membrane resistance the more myelin an axon has

2) longitudinal resistance is the resistance within the axon, the diameter of the axon correlates to the resistance; the wider the axon, the less longitudinal resistance there is

Question 16

What’s membrane potential?

Answer 16

It is the charge difference across a cell’s membrane.

Question 17

What’s chemical gradient?

Answer 17

It refers to the difference in concentration (quantity) of an ion on either side of the membrane

Question 18

What’s the action potential?

Answer 18

It is a unidirectional communication mechanism that allows neurons to send electrical (and chemical) signals from one cell to the next

Question 19

What are some features of action potentials?

Answer 19

• any cell capable of producing electrical activity can fire an action potential
• the action potential must proceed in one direction
• while most action potentials are considered to be all or nothing, some action potentials are an exception to this, and are referee to as graded potentials

Question 20

In order for a neuron to actually gire an action potential, what must happen?

Answer 20

The threshold potential (-55 mV) must be exceeded

Question 21

When a neuron is not firing an action potential, what stage is it in?

Answer 21

It maintains a resting potential (-70 mV)

Question 22

What are the 3 phases of action potential called?

Answer 22

Depolarization, repolarization, and Hyperpolarization

Question 23

What happens in the depolarization phase?

Answer 23

The threshold potential is reached & sodium voltage-gated channels begin to open

Question 24

What happens in the repolarization phase?

Answer 24

Once sodium ions reach equilibrium, voltage-gated sodium channels close and potassium ions begin to flow out of the cell

Question 25

What happens in the hyperpolarization phase?

Answer 25

There’s a brief period when more potassium ions leave the cell while voltage-gated channels begin to slowly close

Question 26

What pump is used during the hyperpolarization phase?

Answer 26

The sodium-potassium pump

Question 27

What’s the role of the sodium-potassium pump?

Answer 27

It plays a critical role in restoring the resting potential of the neuron; the pump forces 3 sodium ions out the ell and pushes 2 potassium ions into the cell

Question 28

What’s myelin?

Answer 28

It is a lipid-rich sheath that wraps around the insulates of the axon of neurons; most neurons are myelated to some degree

Question 29

What does increased myelination do and how?

Answer 29

It allows for a faster rate of action potential because it creases segmens of the axon in which there are no ion channels; this results in saltatory conduction which allows the action potential to “skip” the myelinated sections of the axon.

Question 30

Where are ion channels present in the axon?

Answer 30

In gaps between myelin sheaths called the nodes of ranvier