Neuro-Ch 3/4

What makes up the CNS

What makes up the CNS

brain and spinal cord

What makes up the PNS

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

Neurons are the ___________ of the nervous system

functional unit

What is the function of neuron dendrites

receive electrical signals

What is neuron soma and its job

body of neurons- responsible for the health of the neuron

What is the job of neuron axons

longest part of the neuron- carries signal

What is the function of neuron myelin sheaths

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

What is the function of neuron axon terminals

make synaptic connections with another cell of effector cell

In the brain, fiber types can be classified based on

where they go

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

commissural fibers

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

associative fibers- arcuate or U shaped fibers

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

projection fibers

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

projection fibers

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

neurons

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

neuroglial cells

What are examples of neuroglial cells

astrocytes oligodendrocytes microglia

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

ependyma

Glial cells support what

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

What role do microglia cells play

phagocytic/ scavenger

What are the 3 main types of macroglia

astrocytes oligodendrocytes ependymal cells

What is the function of astrocytes

metabolic support- scaffold for growing axons and BBB

What is the function of oligodendrocytes

make myeline (1 can myelinate dozens of axons)

What is the function of ependymal cells

produce CSF in the ventricles

Schwann cells make myelin in what nervous system

PNS

Oligodendrocytes make myelin in what nervous system

CNS

Astrocytes as always attached to what

blood vessels

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

unipolar, bipolar, multipolar, and pseudounipolar

Unipolar neurons have no dendrites and are found where

in glands for secretion and smooth muscle

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)

Most of the neurons in the body are

multipolar

pseudounipolar neurons are typically found where

ANS, some cranial nerves

PNS nerves can be classified as

motor, sensory, mixed, autonomic

Nuclei are housed where

CNS- grey matter of the brain

Ganglia are housed where

PNS- plexuses

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

What is the role of epineurium

surrounds, protects and enhances gliding between fasiculi

What is the role of perineurium

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

What is the role of endoneurium

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

Nerves are regularly _______ and _______ during movement

compressed and elongated

Decreasing the diameter of intrinsic blood vessels does what

increases intraneural pressure decreases blood flow within the nerve

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

numb feeling

50-70mmHg blood flow ceases resulting in

permanent myelin and axon damage

peripheral nerves are surrounded by_______ making them vulnerable to microtrauma

bone, fascia, and muscle

Compression commonly occurs in locations where nerves pass through what

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

Compression injuries result in what

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

What is carpal tunnel syndrome

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

Carpal tunnel syndrome results in

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

Radial nerve mononeuropathy results in

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

Nerve injuries are generally characterized by

demyelination or axonal loss

What is a crush injury

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

What is a stretch injury

significant traction placed on the nerve usually during higher velocity trauma

What are transection injuries

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

What are the two classifications of nerve injuries

Seddon Sunderland

What is neuropraxia

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

Neuropraxia is characterized by

transient weakness/paresthesia complete recovery expected

What is axonotmesis

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

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

1-2 nodes of ranvier

Axonotmesis is characterized by

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

What is neurotmesis

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

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

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

What are the positive prognostic factors for neurotmesis

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

UMN testing for neurovascular entrapment will show what

hyperreflexia, hyporeflexia, spasticity, hypotonia

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

Why is electrical stimulation not appropriate for denervated muscle

could further damage sensation

Why does axon regeneration not occur in the CNS

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

Why is repair limited in the CNS

no schwann cells astrocytes

Only the _____ can repair itself (nerve part)

axon

How fast does a peripheral nerve grow

1mm/day

Neurons have a resting potential that varies between

-40mV and -90mV

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

amplitude

What occurs during an action potential

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

Neurotransmitters can do what two things

excite inhibit

What is the synapse processing

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

What is temporal summation

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

What is spatial summation

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

What is EPSP

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

What is IPSP

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

Where do you measure post-synaptic potentials

axon hillock

Acetylcholine is excitatory, it helps with

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

Epinephrine/norepinephrine are excitatory, they help with

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

Dopamine is excitatory and inhibitory, it helps with

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

Serotonin is excitatory and inhibitory, it helps with

body temperature, sleep, mood, appetite, pain

Neurons that use ACh as a transmitter are called

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

Widespread loss of cholinergic neurons is associated with

Alzheimer's disease

ACh is located in the post synaptic membrane of what

neuromuscular junction of straited muscles visceral motor system

glutamate is an excitatory neurotransmitter that effects what

learning and memory Site of action- brain

Glycine is an inhibitory neurotransmitter in

spinal cord low amounts lead to increased spasticity

GABA is an inhibitory neurotransmitter that effects what

sedation, antianxiety, antiseizure, sleep induction low amounts lead to seizures, spasticity, anxiety

Where is GABA site of action

entire CNS

Where is dopamine located in the brain

substantia nigra

Many drugs that affect dopamine synapses also affect what

noradrenergic synapses (norepi/epi)

preganglionic sympathetic neurons are called what

cholinergic- use ACh to facilitate nerve transmission

Postganglionic sympathetic neurons are called what

andrenergic- secrete norepi as their neurotransmitter

pre and postganglionic neurons are called

cholinergic- secrete ACh as their neurotransmitter

The nervous system develops from part of the ectoderm called the

neural plate

The neural plate forms the

neural tube- walls= CNS, cavity=ventricular system

What produces the CSF

choroid plexus- ependymal cells

There are two ends of the neural tube (neuropores) that need to close at precisely the right time to prevent what

anencephaly spina bifida

What is myelomeningocele

cord and nerves develop outside of the body- spina bifida

What is meningocele

meninges and CSF outside the body, doesn't affect neuro- spina bifida