Section 2

Question 1

What are neurons?

Answer 1

Cells that are excitable and can generate and transmit rapid electrical signals to other neurons

Question 2

Describe neuron structure.

Answer 2

Neurons are the structural units of the nervous system. Neurons allow for communication within and between the CNS and PNS.

All neurons have similar structures:
- Cell body
- Cytoplasmic processes (dendrites, axons)

Question 3

What are dendrites?

Answer 3

• They receive neuronal signal from other neurons and transfer those signals to the cell body

Question 4

What is the cell body of a neuron?

Answer 4

• Also called ‘soma’
• Houses the nucleus and other organelles
• Functions to transfer electrical signals from the dendrites to the axon

Question 5

What is the axon?

Answer 5

• There is only one axon per neuron
• Carries signals away from the cell body to the axon terminals, where the signal is then transferred to other neurons or organs.

Question 6

How many axons is there per neuron?

a) 0
b) 1
c) 2
d) 3

Answer 6

1

Question 7

What is the direction of a nerve impulse?

Answer 7

Neurons allow organs within the body to communicate with one another through the rapid transduction of electrical signals known as nerve impulses. It is important to note that a nerve impulse is unidirectional - only occurring in one direction.

**Signals travel from the dendrites to the cell body through the axons to reach dendrites of adjacent neurons or target organs. Signals DO NOT travel in the opposite direction.

Question 8

What are pseudounipolar neurons?

Answer 8

• (unipolar)
• have one cellular process that splits into a dendrite and an axon
• general sensory nerves are an example

Question 9

What are bipolar neurons?

Answer 9

• have one dendrite and one axon that extend directly from the cell body
• have two distinct cellular processes
• are only found in special senses, like sight and hearing

Question 10

What are multipolar neurons?

Answer 10

• have multiple dendrites and one axon, summing to three or more cellular processes
• the number of dendrites is variable
• most common type of neurons
• motor neurons are an example

Question 11

What are supporting cells?

Answer 11

• Known as neuroglia or glia
• they function to protect and support neurons, and aid in sending signals between neurons to improve communication
• unlike neurons, these cells do not generate or transmit nerve impulses
  *glia means glue, so neuroglia are like glue that holds it all together

Question 12

What are the four supporting cell types in the CNS?

Answer 12

Astrocytes, microglia, ependymal, and oligodendrocytes.

Question 13

What are astrocytes?

Answer 13

• large star shaped cells
• communicate with neurons and blood vessels to maintain the integrity of the neural tissue
• the most abundant of the glial cells in the CNS

Question 14

What are microglia?

Answer 14

• small glial cells
• perform many protective functions in the CNS
• able to phagocytose, or engulf and destroy pathogens, and eliminate waste products from other cells
• the least common type of supporting cells

Question 15

What are ependymal cells?

Answer 15

• cuboidal in shape and line cavities of the brain and spinal cord
• assist in the production, circulation, and monitoring of the cerebrospinal fluid (CSF)

Question 16

What are oligodendrocytes?

Answer 16

• wrap around axions in the CNS to forms myelin sheath
• a single cell can myelinate up to 60 axons
• oligodendrocytes have many processes that extend to myelinate axons

Question 17

Describe the importance myelination.

Answer 17

• an important part of some neuroglia is to myelinate (wrap myelin around) parts of an axon
• myelin is composed mainly of fat and appears white
• it insulates the axon and increases speed at which electrical signals can travel down the axon

Question 18

What are unmyelinated regions known as?

Answer 18

• nodes of Ranvier (neurofibril nodes)
• they are small regions of axons that are unmyelinated between adjacent regions of myelination

Question 19

What are the supporting cells of the PNS?

Answer 19

• the Schwann cell
• equivalent to oligodendrocytes in that they form the myelin sheath around nerve fibres (axons) in the PNS
• a single Schwann cell can only myelinate a portion of one axon, as they do not have processes like oligodendrocytes

Question 20

Compare and contrast the Schwann cell and oligodendrocytes.

Answer 20

• the Schwann cell is the equivalent to oligodendrocytes in that they form the myelin sheath around nerve fibres (axons) in the PNS
• a single Schwann cell can only myelinate a portion of one axon, as they do not have processes like oligodendrocytes

Question 21

Compare and contrast the structure and function of dendrites and axons in a neuron.

Answer 21

Both dendrites and axons are capable of transmitting electrical signals to other structures for communication.

A neuron may have one or more dendrites, but can only have one axon.

Dendrites and axons also differ in that dendrites receive signals from other neurons, whereas axons send signals to other neurons.

Question 22

Which two cell types are responsible for myelinating axons?

• Astrocytes
• Microglia
• Schwann cells
• Ependymal cells
• Oligodendrocytes

Answer 22

Schwann cells and oligodendrocytes