Nerve Cell A&P Pt.1 Flashcards
What is an individual nerve cell called?
A neuron.
What is a bundle of axons in the spinal cord called?
A tract.
What is a bundle of axons in the periphery called?
A nerve.
What is a group of nerve cell bodies in the CNS called?
A nuclei.
What is a group of nerve cell bodies in the PNS called?
A ganglia.
What does the neuron cell body contain?
A nucleus and organelles.
What is the main function of the neuron cell body?
To produce neurotransmitters.
What are dendrites?
The receptor regions of the neuron cell body that receives and transmits messages.
How do dendrites receive signals?
From multiple local potential charges generated by other synaptic connections of terminal buttons.
What are telodendria?
Fine twig-like terminal branches of the neuron.
How many synaptic junctions does each nerve cell have at maximum?
10,000.
Where is the axon hillock located?
Between the axon and cell body.
What is the function of the axon hillock?
It controls the movement of the action potential to the axon, deciding whether or not the nerve will fire.
What is the function of the initial segment of the axon?
It is where the propagation of the AP is generated that moves down the axon.
How does the propagation of the initial segment occur?
Hypopolarization of the region allows for quicker achievement of action potential.
What is the axonal process?
The transmission of the action potential to nerve endings.
Is the axonal process unidirectional or bidirectional?
Unidirectional.
What is the terminal end, synaptic knob, terminal buttons?
The region where the AP causes the release of synaptic neurotransmitters to dendrites or cell body of other neuron or tissue.
What is the synapse?
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.
What is myelin composed of?
Proteins and lipids.
What does myelin surround?
The nerve cell axon.
What is the function of myelin?
To act as an insulator.
Are all nerve cells myelinated?
Despite some nerves cells being classified as unmyelinated, all nerve cells have myelin. It is the amount of myelin they have that counts.
How does the myelin sheath form around the nerve cell axon?
- Schwann cell membranes envelope the axon.
- Schwann cells rotate many times around the axon.
- Multiple layers of Schwann cell membrane (contains sphingomyelin) is laid down.
What is sphingomyelin an excellent insulator against?
Electricity.
How does the presence of sphingomyelin impact the membrane?
It decreases ion flow through the membrane.
What are nodes of Ranvier?
Small (2-3 um in length), uninsulated areas between the Schwann cells.
What is the function of the nodes of Ranvier?
To allow for the exchange of ion through the axon membrane and saltatory conduction.
What rate is an AP conducted through a myelinated axon?
Rapidly.
What rate is an AP conducted through an unmyelinated axon?
Slowly.
Where are unmyelinated axons found in the PNS?
- Autonomic visceral nerves.
- Senses.
*These need to be slowed down.
What is saltatory conduction?
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.
How much faster does the AP move down the axon?
5-50 fold.
What does the electrical current conduct through during saltatory conduction?
The ECF.
How does saltatory conduction conserve energy?
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.
What is demyelination?
The loss or destruction of the myelin sheath around the axon.
What disease is associated with progressive demyelination of the CNS neurons?
Multiple sclerosis (MS).
How many people worldwide are affected by MS?
2 million.
What age range is MS normally diagnosed in?
20-40.
Which sex is 2x more likely to be affected by MS: Females or Males?
Females.
What type of disease in MS?
An autoimmune disease.
What happens during MS?
Multiple regions of myelin sheath deteriorate to sclerosis or hardened plaques.
What does the formation of plaques cause?
The short circuiting of the propagation of nerve impulses.
What is the cause of MS?
Genetic and environmental exposure.
What group is affected by Tay-Sachs disease?
Eastern European Jewish (Ashkenazi Jew).
What is the inheritance pattern of Tay Sachs?
Autosomal Recessive.
What enzyme are those with Tay Sachs lacking?
The lysosomal enzyme Hex A.
What is the function of Hex A?
To breakdown the membrane glycolipid ganglioside G_M2.
What happens when excessive ganglioside accumulation occurs?
Nerve cell function is decreased.
What are the signs of Tay Sachs?
- Seizures.
- Muscle Rigidity.
- Blindness.
- Dementia.
- Incoordination.
What is the life expectancy of someone with Tay Sachs disease?
Death before age 5.
What is hypomyelinogenesis?
Decreased or absent myelination.
What is dysmyelination?
Abnormal myelination.
What is Wallerian degeneration?
The gradual breakdown and disappearance of the axon and its supporting cells distal to the injury.
What is the best way to care for an animal with a degenerative condition?
Supportive care.
What method can be used for early detection of degenerative conditions?
Genetic testing.
What are the signs of shaking pup syndrome?
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.
What causes shaking pup syndrome?
Hypomyelination.
What is the treatment for shaking pup syndrome?
No treatment, but most recover by 1-1.5 years of age with only a lifelong, mild hindlimb tremor.
