PHYSIOLOGICAL STRUCTURE OF NEURONS

Question 1

What do neurons all have in common?

Answer 1

• cell bodies, dendrites, and an axon

Question 2

What does a neuron’s cell body contain?

Answer 2

• membranous packets of chromatophilic substance (Nssl bodies), that consist of mainly rough endoplasmic reticulum - are scattered through out the cell body
• Cytoplasmic inclusion in neurons inclue glycogen, lipids and pigments such as melanin

Question 3

What are the general characteristics of dendrites?

Answer 3

• typically highly branched and provide receptive surfaces with which processes from other neurons communicate
• generally, neurons receive input thru the dendrites and the cell body, and send output in the form of an impulse conducted away from the cell body, down the axon

Question 4

What are the general characteristics of axons?

Answer 4

• a neuron only has one axon
• arises from a cone-shaped thickening called the axon hillock
• axons may give off branches called “collaterals”
• has a specialized ending called an “axon terminal”
• most axons are bundled together in the PNS, and are called “nerves,” in the CNS they are called “tracts.”

Question 5

What are the characteristics of an axon terminal?

Answer 5

• ends as a synaptic knob close to the receptive surface of another cell, separated only by a space called the synaptic cleft

Question 6

What are the general characteristics of Schwann cells?

Answer 6

• are located in the PNS
• are neuroglia cells
• encase large axons of PNS in lipid-rich sheaths
• these sheaths are composed of myelin which consists of lipids and proteins

Question 7

What is the neurolemma?

Answer 7

• outside portion of the myelin sheath that contains most of the cytoplasm and the nuclei of the Schwann cells

Question 8

Where does the white matter within the brain and spinal cord get its color from?

Answer 8

• groups of myelinated axons that appear white

Question 9

In the CNS, what type of neuroglia cell produces myelin?

Answer 9

• oligodendrocytes

Question 10

What is gray matter?

Answer 10

• unmyelinated axons and neuron cell bodies

Question 11

What are the 3 classifications of neurons?

Answer 11

• multipolar
• bipolar
• unipolar

Question 12

What are the general characteristics of a multipolar neuron?

Answer 12

• has many processes arising from its cell body
• only one is an axon; the rest are dendrites
• most neurons in the CNS are this type
• some are associated with the autonomic nervous system, and others are found in specialized parts of the eyes

Question 13

What are the general characteristics of bipolar neurons?

Answer 13

• has only two processes, one arising from either end
• processes are similar in structure, one is an axon and the other is a dendrite
• found in specialized parts of the eyes, nose and ears (sensory receptors)

Question 14

What are the general characteristics of unipolar neurons?

Answer 14

• has a single process extending from cell body
• this process divides into two branches, which really function as a single axon
• one branch (peripheral process) has dendrites
• the other branch (central process) enters the brain or spinal cord
• the cell bodies of most unipolar neurons are found in ganglia

Question 15

What are the functional characteristics of sensory neurons?

Answer 15

• conducts impulses from receptors in peripheral body parts into the brain or spinal cord
• most unipolar, some bipolar, some multipolar

Question 16

What are the general characteristics of an interneuron?

Answer 16

• relays info between neurons in the brain and spinal cord (CNS)
• multipolar

Question 17

What are the general characteristics of a motor neuron?

Answer 17

• conducts impulses from the brain or spinal cord out to the effectors - muscles or glands

Question 18

What are the characteristics of oligodendrocytes?

Answer 18

• resemble astrocytes but are smaller and have fewer processes.
• form in rows along axons (nerve fibers), and myelinated these axons in the CNS
• can myelinate many axons, however do not form neurilemma

Question 19

What are the characteristics of microglia cells?

Answer 19

• are small cells and have fewer processes than other types of neuroglia
• are scattered throughout the CNS, where they help support neurons and phagocytize bacterial cells and cellular debris

Question 20

What are the characteristics of ependyma cells?

Answer 20

• cuboidal or columnar cells in shape and may have cilia
• form the inner lining of the central canal that extends downward thru the spinal cord
• form one-cell-thick epithelial-like membrane that covers the inside of spaces in the brain called “ventricles”
• gap junctions join ependymal cells, allowing free exchange between cells
• allows substances to diffuse freely between the interstitial fluid of the brain tissues and the fluid in the ventricles

Question 21

What are the neuroglia cells of the CNS?

Answer 21

• microglia
• astrocytes
• oligendendrocytes
• ependymal

Question 22

what are the neuroglia of the PNS?

Answer 22

• Schwann cells

- Satellite cells

Question 23

What are the characteristics of satellite cells?

Answer 23

• provide nutritional support and help regulate the concentrations of ions around Enron cell bodies within ganglia

Question 24

What is the flow of info in the nervous system?

Answer 24

• sensory input flows from sensory receptors to the brain, or spinal cord for integrating and processing followed by motor output of (effectors) the elicit a response