Neuro-Ch 3/4

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What makes up the CNS

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What makes up the CNS

brain and spinal cord

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What makes up the PNS

cranial nerves, spinal nerves, sensory organs (eyes, tongue, nose)

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Neurons are the ___________ of the nervous system

functional unit

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What is the function of neuron dendrites

receive electrical signals

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What is neuron soma and its job

body of neurons- responsible for the health of the neuron

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What is the job of neuron axons

longest part of the neuron- carries signal

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What is the function of neuron myelin sheaths

layer of fat that wraps axon, protects and speeds up signal

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What is the function of neuron axon terminals

make synaptic connections with another cell of effector cell

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In the brain, fiber types can be classified based on

where they go

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What fibers pass from one hemisphere to the other via the corpus callosum

commissural fibers

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What fibers pass from one lobe to another lobe in the same hemisphere

associative fibers- arcuate or U shaped fibers

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What fibers descend from the cerebral hemispheres to other areas of the CNS (mostly in internal capsule)

projection fibers

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After passing through the upper part of the brain stem, these fibers fan out and extend to the cerebral cortex

projection fibers

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What cells in the nervous system are capable of transmitting an impulse

neurons

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What cells in the nervous system are NOT capable of transmitting an impulse

neuroglial cells

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What are examples of neuroglial cells

astrocytes oligodendrocytes microglia

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What is an example of non-neuroglial cells that are not capable of transmitting an impulse

ependyma

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Glial cells support what

neuronal function- there are 10 for every neuron in the brain

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What role do microglia cells play

phagocytic/ scavenger

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What are the 3 main types of macroglia

astrocytes oligodendrocytes ependymal cells

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What is the function of astrocytes

metabolic support- scaffold for growing axons and BBB

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What is the function of oligodendrocytes

make myeline (1 can myelinate dozens of axons)

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What is the function of ependymal cells

produce CSF in the ventricles

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Schwann cells make myelin in what nervous system

PNS

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Oligodendrocytes make myelin in what nervous system

CNS

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Astrocytes as always attached to what

blood vessels

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Neurons are named based on the number of axons- what are the four main types of neurons

unipolar, bipolar, multipolar, and pseudounipolar

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Unipolar neurons have no dendrites and are found where

in glands for secretion and smooth muscle

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Bipolar neurons process like a dendrite and bring information into the cell body down the axon- they are found where

retina, somatic sensory (smell, touch)

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Most of the neurons in the body are

multipolar

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pseudounipolar neurons are typically found where

ANS, some cranial nerves

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PNS nerves can be classified as

motor, sensory, mixed, autonomic

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Nuclei are housed where

CNS- grey matter of the brain

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Ganglia are housed where

PNS- plexuses

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Connective tissue has three layers that are interconnected and contain free nerve endings that can be a source of pain- what are the layers

epineurium perineurium endoneurium

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What is the role of epineurium

surrounds, protects and enhances gliding between fasiculi

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What is the role of perineurium

pressurized container that surrounds the individual fascicles- selective barrier to diffusion, controls movement of fluid and ions

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What is the role of endoneurium

surrounds each nerve fiber and maintains fluid pressure (pressure increases with compression)

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Nerves are regularly _______ and _______ during movement

compressed and elongated

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Decreasing the diameter of intrinsic blood vessels does what

increases intraneural pressure decreases blood flow within the nerve

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20-30mmHg adversely affects intraneural blood flow resulting in a

numb feeling

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50-70mmHg blood flow ceases resulting in

permanent myelin and axon damage

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peripheral nerves are surrounded by_______ making them vulnerable to microtrauma

bone, fascia, and muscle

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Compression commonly occurs in locations where nerves pass through what

narrow anatomical openings (osseous tunnels, fibro-osseous tunnels, soft tissue tunnels)

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Compression injuries result in what

increased intraneural pressure, decreased blood flow, and increased neural ischemia

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What is carpal tunnel syndrome

compression of the median nerve between the carpal ligament and other tunnel tissues

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Carpal tunnel syndrome results in

pain, burning, paresthesia- digits 1-3 and forearm weakness/atrophy of thenar eminence

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Radial nerve mononeuropathy results in

transient paresthesia, numbness, wrist drop (C6), decreased finger extension

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Nerve injuries are generally characterized by

demyelination or axonal loss

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What is a crush injury

acute traumatic nerve compression from a blunt object that does not result in nerve transection

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What is a stretch injury

significant traction placed on the nerve usually during higher velocity trauma

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What are transection injuries

lacerations due to fractures or knife, gunshot, or shard wounds

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What are the two classifications of nerve injuries

Seddon Sunderland

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What is neuropraxia

focal demyelination without damage to the axon or connective tissue mild nerve compression/traction, compression of blood vessels

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Neuropraxia is characterized by

transient weakness/paresthesia complete recovery expected

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What is axonotmesis

demyelination and axon damage due to stretch, crush, or contusion injury

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Wallerian Degeneration occurs with axonotmesis both proximal and distal to at least

1-2 nodes of ranvier

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Axonotmesis is characterized by

motor, sensory, or automatic dysfunction connective tissue intact regeneration may occur at 1mm/day

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What is neurotmesis

complete transection of a peripheral nerve due to trauma resulting in sensory and motor deficits

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Schwann cells and endoneurial tubes can remain viable for how long post injury

18-24 months- surgery needed regrowth occurs at 1mm/day

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What are the positive prognostic factors for neurotmesis

young age, distal nerve injury, end to end repair, early repair

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UMN testing for neurovascular entrapment will show what

hyperreflexia, hyporeflexia, spasticity, hypotonia

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Functional recovery post peripheral nerve injury is often suboptimal as patients with peripheral nerve injuries experience.

increased risk of long term disability decreased functional capacity

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Why is electrical stimulation not appropriate for denervated muscle

could further damage sensation

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Why does axon regeneration not occur in the CNS

limited by inhibitory influences of glial cells- glial scar debris not cleared away quickly

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Why is repair limited in the CNS

no schwann cells astrocytes

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Only the _____ can repair itself (nerve part)

axon

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How fast does a peripheral nerve grow

1mm/day

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Neurons have a resting potential that varies between

-40mV and -90mV

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A stronger stimulus gives rise to more APs but what is always the same

amplitude

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What occurs during an action potential

stimulus applied, Na goes in changing membrane potential, Na channels close, K channels open (repolarization)

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Neurotransmitters can do what two things

excite inhibit

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What is the synapse processing

AP, Ca channels open, ACh released diffuse across synaptic cleft binds to postsynaptic membrane

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What is temporal summation

several impulses from one neuron over time single neuron generates AP- less efficient

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What is spatial summation

sensory summation involving adding stimulus from various spatially separated neurons multiple neurons generate AP

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What is EPSP

excitatory post synaptic potential- exciting environment, easy to fire AP Na channels open glutamate

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What is IPSP

inhibitory post synaptic potential- low potential of firing AP chloride channels open GABA

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Where do you measure post-synaptic potentials

axon hillock

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Acetylcholine is excitatory, it helps with

muscle contraction, cortical neuroplasticity, hormone secretion, short term memory, learning

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Epinephrine/norepinephrine are excitatory, they help with

fight/flight: blood vessel constriction, increased HR, attentiveness, emotions, sleeping

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Dopamine is excitatory and inhibitory, it helps with

movement and posture control, mood, cognition, working memory, reward/reinforcement

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Serotonin is excitatory and inhibitory, it helps with

body temperature, sleep, mood, appetite, pain

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Neurons that use ACh as a transmitter are called

cholinergic neurons- arousal, sleep wake cycle, learning and memory

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Widespread loss of cholinergic neurons is associated with

Alzheimer's disease

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