The Nervous System Part 1- Neurons and Supporting Cells

Question 1

What is the basic structural and functional unit of the nervous system?

Answer 1

Neurons

Question 2

What are Supporting cells?

Answer 2

Supporting cells, also called glial cells and neuroglia cells, help aid the function of neurons. Unlike neurons glial cells can divide by mitosis.

Question 3

Brain tumors in adults are usually composed of what type of cells?

Answer 3

Glial cells, because unlike neurons glial cells can divide via mitosis.

Question 4

Where is the nutritional center of a neuron?

Answer 4

The cell body, it is where macromolecules are produced.

Question 5

Where are Nissl bodies found in neurons?

Answer 5

Cell body and larger dendrites.

Question 6

What are Nissl Bodies?

Answer 6

Nissl bodies are composed of large stacks of rough endoplasmic reticulum that are needed for the synthesis of membrane proteins. Seen as dark staining granules under the microscope.

Question 7

Cell bodies within the CNS are frequently clustered into groups called what?

Answer 7

Nuclei

Question 8

Cell bodies within the PNS are frequently clustered into groups called what?

Answer 8

Ganglia

Question 9

Dendrites provide a receptive area that transmit graded electrochemical impulses where?

Answer 9

Towards the cell body.

Question 10

Axons conduct impulses called what? and where?

Answer 10

Conduct action potentials away from the cell body.

Question 11

Axon Hillock

Answer 11

The origin of the axon near the cell body, it is an expanded region.

Question 12

What is the region called where the first action potentials are generated? What is it by?

Answer 12

Axon Initial Segment, it is adjacent to the Axon hillock.

Question 13

Towards the ends of axons they can produce up to 200 or more branches that are called..?

Answer 13

Axon Collaterals. This allows a single CNS axon to synapse with as many as 30,000-60,000 other neurons.

Question 14

Two ways neurons can be classified is by their ___ or ___.

Answer 14

Function or Structure.

Question 15

Functional classification of neurons is based on the direction in which they conduct impulses, what are the three types?

Answer 15

Sensory (Afferent) Neurons: Conduct impulses from sensory receptors INTO the CNS.
Motor (Efferent) Neurons: Conduct impulses OUT of the CNS to effector organs (muscles or glands).
Association Neurons (Interneurons): Located entirely within in the CNS, serve as the associative, or integrative, functions of the nervous system.

Question 16

What are the subdivisions of Efferent Neurons?

Answer 16

Somatic- Reflexes and voluntary control of skeletal muscles.
Autonomic- Involuntary control of smooth muscle, cardiac muscle, and glands.
Autonomic can further be divided into Sympathetic (typically speeds things up) and Parasympathetic (typically slows things down)

Question 17

What are the structural classifications of neurons?

Answer 17

Pseudounipolar
Bipolar
MultiPolar
See pg 32 in Notes for examples.

Question 18

What neurons are pseudounipolar? Anatomically how are pseudounipolar neurons described, functionally?

Answer 18

Sensory neurons are pseudounipolar.
Anatomically- process conducting impulses toward the cell body can be considered a dendrite and the part that conducts impulses away from the cell body can be considered an axon.
Functionally- the branched process behave as a single long axon that continuously conducts action potentials. Only the small projections at the receptive end of the process function as typical dendrites, conducting electrical impulses rather than action potentials.

Question 19

What do Dendrites conduct?

Answer 19

Electrical Impulses (like EPSPs and IPSPs)

Question 20

What do axons conduct?

Answer 20

Action Potentials

Question 21

Where are bipolar neurons found?

Answer 21

Bipolar Neurons are found in the retina of the eye.

Question 22

What neuron structurally is the most common? What is an example of this type?

Answer 22

Multipolar Neurons are most common, motor neurons are a good example of multipolar structure.

Question 23

What is a bundle of axons in the PNS called?

Answer 23

A Nerve

Question 24

What is a bundle of axons in the CNS called?

Answer 24

A Tract

Question 25

What is meant by a mixed nerve?

Answer 25

Nerves that are composed of both motor and sensory fibers.

Question 26

What types of cranial nerves contain only sensory fibers?

Answer 26

Nerves that serve the special senses of sight, hearing, taste, and smell.

Question 27

What are the two types of neuroglial cells in the PNS?

Answer 27

Schwann Cells (Neurolemmocytes)
Satellite Cells (Ganglionic Gliocytes)

Question 28

What are the four type of neuroglial cells in the CNS?

Answer 28

Oligodendrocytes
Microglia Cells
Astrocytes
Ependymal Cells

Question 29

What do ganglionic gliocytes do?

Answer 29

They support neuron cell bodies within the ganglia of the PNS. “Regulate” (also called satellite cells)

Question 30

Where tissue are microglia cells derived from?

Answer 30

Hematopoietic Tissue. They are derived from cells that were produced in the embryonic yolk sac and migrated into the developing neural tube. This classifies them as myeloid cells (related to cells derived from bone marrow) but they differ from macrophages in the meninges.

Question 31

Infection, trauma, or any altered state can lead to _________ _________, in which the cells become amoeboid in shape and are transformed into phagocytic, motile cells.

Answer 31

Microglial Activation

Question 32

How do Microglia cells sense the site of an infection or damage?

Answer 32

Their plasma membrane contains receptors for ATP, the ATP is released from damaged cells allowing the microglial cell to migrate toward it and proliferate by cell division.

Question 33

Over active microglia cells may release what? What effect might that have?

Answer 33

May release free radicals that contribute to neurodegenerative diseases.

Question 34

The following are characteristics of what type of cells?

• Kill exogenous pathogens
• Remove damaged dendrites, axon terminals, myelin, and other debris within the CNS.
• Release anti-inflammatory chemicals.

Answer 34

Microglia Cells

Question 35

Where is the neurilemma found?

Answer 35

Neurilemma AKA Sheath of Schwann is found around all axons of the PNS. Found in both myelinated and unmyelinated axons. (it is the outer layer)

Question 36

Axons that are smaller than 2 micrometers in diameter are usually?

Answer 36

Unmyelinated.

Question 37

Axons that are _______ conduct impulses more rapidly.

Answer 37

Myelinated.

Question 38

What determines the number of times a schwann cell will wrap itself around an axon?

Answer 38

The number of layers in the myelin sheath is great for thicker than for thinner axons. So the thickness determines it.

Question 39

Which myelin forming cell produces extensions, like tentacles of an octopus, that form myelin sheaths around several axons?

Answer 39

Oligodendrocytes in the CNS.

Question 40

What is responsible for white matter in the central nervous system?

Answer 40

The myelin sheath give CNS tissue a white color, so areas that contain a high concentration of myelinated axons are called “white matter”. Unmyelinated regions are called “gray matter”.

Question 41

Where is white matter in the spinal cord vs the brain?

Answer 41

Spinal Cord- White matter is on the outside (gray inside)

Brain- White matter is on the inside and Gray matter is on the Outside.