Components of the nervous system (Chapter 1)

Question 1

What are the major components of the nervous system?

Answer 1

PNS: spinal and cranial nerves, receptor cells (non-neuronal)
CNS: spinal cord, brainstem, cerebellum, cerebrum (hemispheres; diencephalon)

Question 2

What are the major cell types in the CNS?

Answer 2

Neurons
Glia
Macroglia (oligodendrocytes, astrocytes)
Microglia
Ependymal cells

Question 3

What are the major cell types in the PNS?

Answer 3

Neuronal cell bodies (sensory neurons, autonomic ganglia)
Parts of neurons: motor neuron axons, autonomic neuron axons, spinal and cranial nerves, sensory neuron peripheral processes)
Glial cells (Schwann cells)

Question 4

What are the four major functions of a neuron?

Answer 4

Input, integration, conduction, and output.

Question 5

What part of the neuron collects information from other neurons (input function)?

Answer 5

Dendrites

Question 6

What part of the neuron integrates electrical signals?

Answer 6

Soma (axon hillock)

Question 7

What part of the neuron conduct information across distances?

Answer 7

Axons

Question 8

What part of the neuron transmits electrical and chemical information to other neurons?

Answer 8

Synapses

Question 9

Draw and label the structure of a typical neuron.

Answer 9

Identify: Soma (perikaryon), dendrite, axon, axon hillock, axon terminal, synapse, nodes of Ranvier, internodes

Question 10

What are the 3 different types of neurons? Draw and label.

Answer 10

Multipolar (single axon, multiple dendrites from soma)
Bipolar (single axon, single dendrite)
Unipolar (“pseudo-unipolar”; begin as bipolar but expand asymmetrically during development)

Question 11

Dorsal root ganglia = info from _______
Ventral root ganglia = info to _______
Autonomic ganglia = info to _______

Answer 11

Dorsal root ganglia = info from sensory receptors
Ventral root ganglia = info to skeletal muscle (efferent motor info)
Autonomic ganglia = info to viscera

Question 12

What are Nissl bodies and where are they found?

Answer 12

Nissl bodies are free ribosome clusters bound to endoplasmic reticulum. They tend to clump together when stained. They are found in soma dendrites but not axons or axon hillock.

Question 13

What are the three types of filamentous protein polymers involved in cytoskeletal structure and axon transportation?

Answer 13

Microtubules, neurofilaments, microfilaments

Question 14

Active transport occurs when…

Answer 14

Active transport occurs when the distance to be traveled is too far for diffusion to be effective.

Question 15

Active transport can occur in both anterograde and retrograde directions. What determines the direction in which it occurs?

Answer 15

Tubulin is polarized: +

Question 16

Fast active transport can occur in both anterograde and retrograde directions. What determines the direction in which it occurs?

Answer 16

Microtubules run along the axon as cytoskeletal “tracks”.
Microtubules are made of tubulin.
Tubulin is structurally polarized.
Axonal microtubules are oriented with + ends away from cell body and toward axon terminals.
Dendritic microtubules can be oriented in either direction.

Question 17

What is the mechanism of fast axonal transport?

Answer 17

ATPases kinesin (anterograde) and dynein (retrograde) bind components to form “bridges” that allow organelles to “walk” along the microtubules.

Question 18

What are the differences between fast and slow axonal transport?

Answer 18

Fast: Uses microtubules and ATPases kinesin and dynein. In both anterograde and retrograde directions. Used for mitochondria, lysosomes, and vesicles of neurotransmitters. Up to 400mm/day.

Slow: Mechanism unknown. Anterograde direction only. Used for soluble proteins (cytoskeletal proteins and enzymes).

Question 19

Name the potential sites/types of synaptic contacts.

Answer 19

Axodendritic
Axosomatic
Dendodendritic
Axoaxonic (AA1: at axon terminal)
Axoaxonic (AA2: at initial segment where axon is connected to dendrite)

Question 20

List the roles of glial cells.

Answer 20

Insulation
Structural support
Removal of debris
Regulate extracellular ionic concentrations
Guides neuron and axon migration
(Possible nutritive function)?

Question 21

What are the two major classes of glia?

What types of cells are included in those classes?

Answer 21

Macroglia: astrocytes, oligodendroglia, ependymal cells, Schwann cells (PNS)
Microglia: various phagocytic cells

Question 22

What type of glial cells guide and support migrating axons during development?

Answer 22

Radial astrocytes

Question 23

What type of glial cells make up the BBB?

Answer 23

Astrocytes

Question 24

What type(s) of glial cells are involved in myelination?

Answer 24

Oligodendroglia (CNS, extend multiple “feet” to wrap multiple cells), Schwann cells (PNS, single process)

Question 25

Describe the effects of demyelination in MS.

Answer 25

MS is an autoimmune disease that attacks and damages oligodendroglia in the CNS.
In MS, oligodendroglia die unevenly, leading to irregular patches where myelination is lost. This disrupts the timing of signals along the axon, leading to disorganization of the signal. Over time, gliotic scars occur (astrocytes take up the space where the lesions are).