Neuro Exam 2

5 main cranial nerves to know, number, name and function (under the page of the slide)

1. 5 (Trigeminal nerve): Intake of solid food because the nerve innervates the muscles of the jaw, hence the ability to chew. Also helps move the larynx up/forward, aka out of the way.

2. 7 (Facial nerve): Facial expressions, but also important for taste, speech sounds, and to retract and contract lips. People who have damage have to worry about anterior loss out of the mouth (aka no labial closure when sipping water)

3. 9 (Glossopharyngeal nerve): taste on the posterior part of the tongue, sensation in the oral cavity of the mouth, pharynx… people with impaired nerves will, a lot of the time, try to swallow far too big bites because they have no sensation of how much is in there, eg., risk of choking/aspiration … controls pharyngeal sensation

4. 10 (Vagus nerve): Controls laryngeal sensation,

5. 12 (Hypoglossal nerve): strictly a motor nerve; only excites action (doesn’t process sensory info); controls movement of the tongue for speech and the oral phase of swallowing

If you encountered a patient in the possible who had a sacrificed facial nerve, what might you see?

What nerves would be important for speech sounds?

Facial nerve

PNS: Spinal Nerves

8 cervical pairs

12 thoracic

…. more to add

Upper motor neurons

originate in the brain or brainstem

Control the lower motor neurons

• initiate a signal that eventually turns the movement, but not what actually carries the movement out

• more so in control of involuntary stuff, posture, muscle tone

Lower motor neurons

When we have an efferent (motor pathway), this excites the movement through spinal and cranial nerves … directly transmits the signal to the muscle that allows us to carry out any function

7 steps

1. Motor cortex, frontal lobe starts

2. Goes to the internal capsule

3. Gets to the brainstem, internal capsule, brainstem, medullary pyramids

4. Motor cortex

5. point of decussation

6. spinal cord

7. lower motor neuron

Next set of slides: Neuron and Glial Cells

Glial Cells and neuroglia are synonymous

Support and protect the nerve cell’s role in communication

(Think of them as the nervous system’s support group)

Framework for how neurons function, remove debris/death, myelin sheath and CSF production

Processes = tentacles (synonymous)

neurons

basic functional unit of central nervous system

Made up of axons and dendrites

6 types of glial cells, where they are, and their basic function

just study the graphic; we will need to know more than basic functions

Slide 4

Glial cells: Astrocytes

Caretaker of the cell (nurse)

• Shaped like a star, provides structure and support

• In the CNS

• Offers metabolic support and responds when the nervous system is injured

• Attaches to and interact with neurons, blood vessels, or the pia mater in the meninges

• Contributes to maintaining the blood-brain barrier

• Satellite cell (PNS) = Astrocyte (CNS); for the purpose of the class, just know which one is on which side

What is the blood brain barrier BBB

Why we feel alcohol, nicotine, and caffeine, but the toxins aren’t allowed through

Filter out significantly harmful things so they don’t get to the brain

Allows medications to work for us

Glial Cells: Oligodendrocytes (CNS)

• On the CNS side

• Much fewer than astrocytes

• Few processes extend from the cell body

• Wraps the neuron's axon in myelin (outside wire). Inside is the neuron's axon - important for the charge of the signal that will be passed

• Covers multiple axon segments of the same axon

How we are able to quickly go from chewing to swallowing - myelination of the axons

Myelin vs Myelin sheath

Myelin is the actual substance that wraps around the axon

The myelin sheath is the process that helps wrap the axons around the …

Shwann Cells (PNS)

• Single cell surrounds one neuron axon segment

Don’t worry about the sizing measurement slides

Multiple Sclerosis (MS): Demyelination Disorders

CNS

• Body marks myelin as an “enemy” (autoimmune disease)

• Destroys myelin → scar tissue

MS is the ATTACKER of Myelin which in turn makes very difficult nerve signals

• Somatic and autonomic impairments

• Types: eventually progressive

• Clinically Isolated Syndrome (CIS)→ first episode

• Relapsing-remitting MS

• Primary progressive

• Secondary progressive

Know that the body attacks myelin, and when the body demyelinates, it can impair function and slow down everyday processes that were used to being faster, sharper, holistically, and globally.

Guillian-Barre Syndrome: Demyelinating Disorders

PNS
Autoimmune response may follow respiratory or digestive tract infection, but not always

• Somatic and autonomic (BP, heart rhythm) - know this and autoimmune response

• Sudden onset of tingling in lower extremities or weakness → progresses to upper extremities and organs

• Life-threatening; severity and recovery vary

• Cause not known; linked to viruses (influenza, Epstein-Barr, COVID-19), hepatitis, HIV, trauma, Hodgkin lymphoma, rarely flu or childhood vaccinations

• Plasma exchange (plasmapheresis) & high-dose immunoglobulin treatment help

If the disease makes it up to your throat, it can complicate breathing and become life-threatening

Moreso likely to be asked about MS on exam

Mylein - brick myelin sheath - brick wall

Glial Cells: Microglia

• On CNS side

• smallest glial cells

• Engulfing and removing debris, using phagocytosis (like Pac-Man)

• act like macrophages (white blood cells in other parts of body)

Glial Cells: Ependymal Cells

• On CNS side

• Assists with filtering blood to make CSF by pulling water and other molecules from capillary blood vessels in the choroid plexus of the ventricles (not on exam)

• Know it assists with making cerebrospinal fluid, which is important with shock absorption, and know that single-layer, tightly compact cells look like epithelial cells (skin), has cilial later that move CSF through the ventricles

Microgilia Functions

see phagocytosis … idk come back to slide 12

Study slide 13 for functions of glial cells and separation by CNS and PNS, you will be tested on all of it

Slide 14 - Neurons … 3 types

1. Sensory neuron - senses pain, pressure, touch, temperature, etc. , PNS

2. Motor neuron - moving, CNS

3. Interneuron (Receives information to integrate and send information); basically bridges the gap between sensory and motor neurons

A neuron is how the body communicates

Neuron Structure

Cell body = soma … reason for the cell structure

○ Maintains neuron structure

○ Nucleus within the cell body→ control center

● Axon (1 per nucleus) important for transmitting signals to other neurons, aka the line aka communication signal is passed on

○ Outgoing signal

○ Electrical signal conduction → action potential

● Dendrites (many, can be thousands per neuron)

○ Incoming signals

● Axon Terminals: end of the line

○ Neurotransmitter location… carries across neurons, aka synapses (vital for communication of nerve signals)

aka know a neurotransmitter: a chemical messenger released by a neuron that go to synapses, released to other neurons or muscles

● Node of Ranvier: myelin sheath gap, every 1 mm aka wipeout balls

○ Thought to increase signal transmission speed; the nodes are checkpoints for action

Where are neurons in the CNS?

Function (Know this)

• White Matter: myelinated axons (myelination is white in color)

• Gray Matter: nerve cell bodies, dendrites, glial cells, axon terminals

Location (Not as important for exam)

• Brain: thin layer of gray matter on surface and found in small clusters; white matter deeper in cortex

• Spinal Cord: gray matter in the H-shaped center, white matter surrounds

Neural Messaging by Conduction

1. A stimulus that starts everything that impacts the neuron membrane in some way

2. Dendrites and cell body of a neuron receive multiple, even 100s of stimuli In some instances, if the stimulus is excitatory or inhibitory (they cancel each other out)

3. If the stimulus is strong enough, it evokes gated channels opening and ion movement - depolarization

4. Rare that a single piece of single stimulus is enough for action potential

How does a signal flow within a neuron (KNOW THESE TERMS): be able to label and talk about the process

Conduction

Resting potential = -70 mV

Depolarization

Repolarization

Refractory

Conduction

process of how a neuron body communicates with its axon terminals

● Electrical signal traveling down an axon = action potential

Resting Potential

neuron is polarized, ion channels (protein structure in membrane) are closed, has minimal

exchange of Na+ and K+

Depolarization

● When the resting potential of -70 mV becomes more positive (+)

● About +30 mV evokes action potential (1/1000 of a second; millisecond)

● Approximately -55 mV opens sodium (Na+) voltage-gated ion channels

● Na+ rushes into the sodium voltage-gated channel, making the intracellular more positive

● The sodium channels close (prefers to be more negatively charged

Repolarization

● Occurs by K+ channel opening to flow out, which restores the intracellular to its resting potential level of -70 mV.

The “comeback”

Refractory Period

In repolarization, it undershoots and becomes too negative (below -70 mV). During this brief

period, it cannot fire another action potential.

Sodium-Potassium Pump Functions

1. Maintaining the sodium-to-potassium gradient

2. Cells need energy provided by sodium influx

Sodium-Potassium Pump Non-gated Channels

• Extracellular Na+ enters cell

● Intracellular K+ leaves cell

Sodium-Potassium Pump Na+-K+ Pump: ratio : 3 to 2 —- slide 23

• Drives out 3 Na+ ions and takes in 2 K+ ions (voltage-gated channel)

● Keeping intracellular polarity with more negative charge

Action Potential Generation — know first paragraph for slide 25

Think of the sodium-potassium pump as a source of energy for the cell, but also maintains under capacity (store person that is the bumper-balancing store lol)

At rest: The inside of the neuron is negative -70mV

The resting state of the neuron is maintained by the voltage gated ion channels: closes off sodium and keeps the potassium ions in

At the threshold of -55 they start to open and at 3 to 2 ratio the potasium sodium is out and in and then depolarization starts when voltage of the neuron is less negative and to positive -55 and then the big spike +30