Nerve Cell A&P Pt.1

Question 1

What is an individual nerve cell called?

Answer 1

A neuron.

Question 2

What is a bundle of axons in the spinal cord called?

Answer 2

A tract.

Question 3

What is a bundle of axons in the periphery called?

Answer 3

A nerve.

Question 4

What is a group of nerve cell bodies in the CNS called?

Answer 4

A nuclei.

Question 5

What is a group of nerve cell bodies in the PNS called?

Answer 5

A ganglia.

Question 6

What does the neuron cell body contain?

Answer 6

A nucleus and organelles.

Question 7

What is the main function of the neuron cell body?

Answer 7

To produce neurotransmitters.

Question 8

What are dendrites?

Answer 8

The receptor regions of the neuron cell body that receives and transmits messages.

Question 9

How do dendrites receive signals?

Answer 9

From multiple local potential charges generated by other synaptic connections of terminal buttons.

Question 10

What are telodendria?

Answer 10

Fine twig-like terminal branches of the neuron.

Question 11

How many synaptic junctions does each nerve cell have at maximum?

Answer 11

10,000.

Question 12

Where is the axon hillock located?

Answer 12

Between the axon and cell body.

Question 13

What is the function of the axon hillock?

Answer 13

It controls the movement of the action potential to the axon, deciding whether or not the nerve will fire.

Question 14

What is the function of the initial segment of the axon?

Answer 14

It is where the propagation of the AP is generated that moves down the axon.

Question 15

How does the propagation of the initial segment occur?

Answer 15

Hypopolarization of the region allows for quicker achievement of action potential.

Question 16

What is the axonal process?

Answer 16

The transmission of the action potential to nerve endings.

Question 17

Is the axonal process unidirectional or bidirectional?

Answer 17

Unidirectional.

Question 18

What is the terminal end, synaptic knob, terminal buttons?

Answer 18

The region where the AP causes the release of synaptic neurotransmitters to dendrites or cell body of other neuron or tissue.

Question 19

What is the synapse?

Answer 19

The region where the terminal end of the neuron releases neurotransmitters to another nerve or tissue. Is in between the terminal end and the receiving neuron or tissue.

Question 20

What is myelin composed of?

Answer 20

Proteins and lipids.

Question 21

What does myelin surround?

Answer 21

The nerve cell axon.

Question 22

What is the function of myelin?

Answer 22

To act as an insulator.

Question 23

Are all nerve cells myelinated?

Answer 23

Despite some nerves cells being classified as unmyelinated, all nerve cells have myelin. It is the amount of myelin they have that counts.

Question 24

How does the myelin sheath form around the nerve cell axon?

Answer 24

1. Schwann cell membranes envelope the axon.
2. Schwann cells rotate many times around the axon.
3. Multiple layers of Schwann cell membrane (contains sphingomyelin) is laid down.

Question 25

What is sphingomyelin an excellent insulator against?

Answer 25

Electricity.

Question 26

How does the presence of sphingomyelin impact the membrane?

Answer 26

It decreases ion flow through the membrane.

Question 27

What are nodes of Ranvier?

Answer 27

Small (2-3 um in length), uninsulated areas between the Schwann cells.

Question 28

What is the function of the nodes of Ranvier?

Answer 28

To allow for the exchange of ion through the axon membrane and saltatory conduction.

Question 29

What rate is an AP conducted through a myelinated axon?

Answer 29

Rapidly.

Question 30

What rate is an AP conducted through an unmyelinated axon?

Answer 30

Slowly.

Question 31

Where are unmyelinated axons found in the PNS?

Answer 31

1. Autonomic visceral nerves. 2. Senses. *These need to be slowed down.

Question 32

What is saltatory conduction?

Answer 32

When the AP conducts from node of Ranvier to node of Ranvier, allowing the AP to move down the cell in a more rapid fashion.

Question 33

How much faster does the AP move down the axon?

Answer 33

5-50 fold.

Question 34

What does the electrical current conduct through during saltatory conduction?

Answer 34

The ECF.

Question 35

How does saltatory conduction conserve energy?

Answer 35

Only the nodes of Ranvier need to depolarize, leading to less loss of ions and less metabolism for re-establishing Na+ and K+ concentration gradients.

Question 36

What is demyelination?

Answer 36

The loss or destruction of the myelin sheath around the axon.

Question 37

What disease is associated with progressive demyelination of the CNS neurons?

Answer 37

Multiple sclerosis (MS).

Question 38

How many people worldwide are affected by MS?

Answer 38

2 million.

Question 39

What age range is MS normally diagnosed in?

Answer 39

20-40.

Question 40

Which sex is 2x more likely to be affected by MS: Females or Males?

Answer 40

Females.

Question 41

What type of disease in MS?

Answer 41

An autoimmune disease.

Question 42

What happens during MS?

Answer 42

Multiple regions of myelin sheath deteriorate to sclerosis or hardened plaques.

Question 43

What does the formation of plaques cause?

Answer 43

The short circuiting of the propagation of nerve impulses.

Question 44

What is the cause of MS?

Answer 44

Genetic and environmental exposure.

Question 45

What group is affected by Tay-Sachs disease?

Answer 45

Eastern European Jewish (Ashkenazi Jew).

Question 46

What is the inheritance pattern of Tay Sachs?

Answer 46

Autosomal Recessive.

Question 47

What enzyme are those with Tay Sachs lacking?

Answer 47

The lysosomal enzyme Hex A.

Question 48

What is the function of Hex A?

Answer 48

To breakdown the membrane glycolipid ganglioside G_M2.

Question 49

What happens when excessive ganglioside accumulation occurs?

Answer 49

Nerve cell function is decreased.

Question 50

What are the signs of Tay Sachs?

Answer 50

1. Seizures. 2. Muscle Rigidity. 3. Blindness. 4. Dementia. 5. Incoordination.

Question 51

What is the life expectancy of someone with Tay Sachs disease?

Answer 51

Death before age 5.

Question 52

What is hypomyelinogenesis?

Answer 52

Decreased or absent myelination.

Question 53

What is dysmyelination?

Answer 53

Abnormal myelination.

Question 54

What is Wallerian degeneration?

Answer 54

The gradual breakdown and disappearance of the axon and its supporting cells distal to the injury.

Question 55

What is the best way to care for an animal with a degenerative condition?

Answer 55

Supportive care.

Question 56

What method can be used for early detection of degenerative conditions?

Answer 56

Genetic testing.

Question 57

What are the signs of shaking pup syndrome?

Answer 57

Apparent, diffuse, coarse tremors that make the puppy bounce up and down rhythmically when they stand or walk. *More severe in pelvic limbs than thoracic limbs.

Question 58

What causes shaking pup syndrome?

Answer 58

Hypomyelination.

Question 59

What is the treatment for shaking pup syndrome?

Answer 59

No treatment, but most recover by 1-1.5 years of age with only a lifelong, mild hindlimb tremor.