neurons and synapse

What are the 2 primary cell types?

Neuronal cells and glial cells

Which cells are responsible for impulse conduction?

Neuronal cells

Which cells are able to divide if damaged?

Glial cells

Which cells are support cells and not able to conduct impulses? "nerve glue"

Glial cells

What comprises a motor unit?

Nerve + muscle (motor neuron that innervates muscle fibers)

What is like the plug for the motor unit?

Terminal Boutons

Where are purkinje cells found?

cerebellum

Where are pyramidal cells found?

Cerebral cortex, hippocampus, neocortex

Where are amacrine cells found?

they’re interneurons found in the inner nuclear layer of the retina

Where are unipolar neurons found?

dorsal root ganglia

Which glial cell types are found in the CNS?

oligodendrocytes and astrocytes

What is the function of astrocytes?

suppress repair after neuronal injury, from the blood brain barrier

What is the function of oligodendrocytes?

responsible for myelination, increase nerve conduction

Which glial cell types are found in the PNS?

Schwann cells

What is the function of Schwann cells?

(similar function as oligodendrocytes) - responsible for myelination and increase nerve conduction

What comprises peripheral nerve structure?

Endoneurium, Perineurium, and Epineurium

What are the types of nerve injuries that can occur?

Neuropraxia, Axonotmesis, Neurotmesis, Avulsion

Describe neuropraxia.

Prognosis?

Compression of a peripheral nerve

Good prognosis - few hours to a few months long

Describe Axonotmesis.

Prognosis?

Axon disrupted, but surrounding nerve sheath intact.

Transection or crush injuries

Fair prognosis (can fix itself or may not)

Describe Neurotmesis.

Prognosis?

Complete Nerve transection, nerve slices completely at the axon

Poor prognosis

Describe Avulsion.

Prognosis?

Nerve tearing.

Poor prognosis

At what phase of action potential do the voltage gated Na+ channels open with great Na+ influx?

Depolarization

At what phase of action potential do the Na+ voltage gated channels close, the K+ voltage gated channels open with an influx of K+?

Repolarization/ Refractory Period

At what phase of action potential do the K+ voltage gated channels close, where equilibrium is reached?

Afterpotential/ Hyperpolarization

Excitatory presynaptic potentials are associated with the opening of _______ ion channels. This is known as __________

Na+ (sodium)

Depolarization

Inhibitory presynaptic potentials are associated with the opening of _______ ion channels. This is known as __________

Cl-

Hyperpolarization

What is the term for when an impulse from one excitatory fiber causes a stimulus that depolarizes the membrane, but is not of large enough magnitude to produce an action potential in the cells?

Sub Threshold Depolarization

What is the term for when a series of impulses in one excitatory fiber produce all together a "suprathreshold" depolarization that triggers an AP? (a stimulus of constant intensity is repeated)

Temporal Summation

What is the term for when impulses in 2 excitatory fibers cause two synaptic depolarizations, that together reach firing threshold and trigger an action potential? (recruiting more functional units for cell of interest)

Spatial Summation

Can excitatory and inhibitory signals cancel one another out?

Yes

If a neuron only receives excitatory impulses, AP will be generated.

If a neuron receives as many inhibitory signals as excitatory, the inhibition cancels out excitation

What are the Nodes of Ranvier?

Gaps in myelin sheath along the axon, where jumps from node to node occur

Define Saltatory conduction

Rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of Ranvier to another (skipping from node to node), skipping the myelin-sheathed regions of membrane.

This increases the conduction velocity of action potentials without needing to increase the diameter of an axon.

Is decrement faster in an unmyelinated or myelinated sheath?

Unmyelinated axons

Demyelinating diseases are also ___________ diseases

Autoimmune

Demyelinating disease defined

Autoimmune disease where the immune system attacks the myelin sheath, leading to de-myelination

What problems are associated with demyelinating diseases?

Muscle weakness
Coordination problems
Fatigue
Vision problems
Numbness
Paralysis

Name some examples of demyelinating diseases that were discussed in lecture

MS (Multiple Sclerosis)
Guillain-Barre Syndrome

What are "Dawson's Fingers"?

Lesions or plaques in the brain matter that resemble fingers, caused by MS

What is demyelination?

when the myelin sheaths surrounding the axon is damaged but still intacted