Clin med- Neuro phys gpardi

Which neuroglial cells will develop the myelin sheaths?

Oligodendrocytes in CNS

Schwann cell in PNS

What are the primary functions of astrocytes?

CNS glial cell

REGULATOR- in and out of cell (ions, NTs, substrates)

contributes to BBB (blood brain barrier)

Glutamate regulator

What is the primary function of microglial cells?

Scavenger functions (phagocytosis)

What are the primary characteristics of Guillain-Barre syndrome?

DEMYELINATION- Slowed nerve conduction, Autoimmune (virus/infection is similar to protein in myelin)

Early complaints of feeling ill

Starts in lower limb and moves up

Symmetric extremity weakness with limited muscle atrophy

Quick progression (relative)

What are the primary characteristics of Bell's Palsy?

Herpes simplex virus/trauma

Degenerating myelin of LMN of facial nerve

Unilateral Facial Nerve deficits on entire affected side (upper and lower)

What are the primary characteristics of MS?

Autoimmune → demyelination

Sensory/Motor/Psychological deficits

Optic Neuritis

Episodic (relapse/remit)

Muscle weakness/parathesias

What are the primary characteristics of Huntington Disease

Mutation to glial cells (astrocytes and microglial cells) → interrupts scavenging and regulation

Disrupts the balance of glutamate (excitoxicity/apoptosis of striatal cells rendering striatum null → decreased GABA release) and GABA within the basal ganglia → HYPERKINETIC outcome

Cognition and mood disturbances

What are the primary channels needed to maintain resting membrane potential

Leak channels (Passive)

Na/K pump (Active)

Which channels (in general) will enable an action potential to propagate?

Voltage gated channels

At resting membrane potential, where is most of the sodium?

Outside the cell

At resting membrane potential, where is most of the potassium?

Inside the cell

Following a threshold potential, what channels open to enable depolarization?

Na VCG open and NA rushes IN

Leak channels stay open

Na/K pump stays active

What enables repolarization of cells?

Na VCG shut

K VGC open and K floods out of cell

In simple terms, if the potassium VCG suffers from a mutation, what general clinical characteristic may occur in muscle?

K stays in the cell → Na/K keeps pumping K in → No ability to trigger an action potential as in constant state of repolarization (-); periodic paralysis

Which channels need to open to enable the movement of Neurotransmitter vesicles to reach presynaptic membrane

Ca VCG

What happens in the presynaptic terminal of the neuromuscular junction once calcium is released?

Ca allows the movement of the ACh vesicles to move to the presynaptic membrane for exocytosis into the synaptic cleft

What are the primary characteristics of Lambert-Eaton?

Autoimmune disorder of the CaVCG

Slows release of Ca= slows release of ACH into synaptic cleft

How to distinguish Lambert Eaton from Myasthenia Gravis?

LE: Weak at first but then increase strength if continue activity

MG: Weakness improves when rest; gives time for ACH to find an active ACH-R

At the post-synaptic end of the neuromuscular junction, receptors will have two primary characteristics- what are they?

Ligand Gated or G-protein

Which receptors are Direct/Fast/Ionotropic?

Ligand Gated

Which receptors are Indirect/Slow/Metabotropic?

G Protein

What are the primary Ionotropic/Metabotropic receptors specific to ACH (the primary NT of the NMJ)?

Ionotropic - Nicotinic

Metabotropic- Muscarinic

What is a receptor related disorder that leads to muscular weakness (and a million of other things); what leads to this disorder?

Myesthenia Gravis

Autoimmune disorder targets the ACH-R on the post-synaptic terminal thus ACH has no where to go → muscle weakness

What is ptosis

Drooping eyelids (facial muscle weakness)

What is diplopia

Double vision (eye muscle weakness)

What is dysphagia

Weakness in pharyngeal muscles (swallowing)

What is dyasarthia

Altered speech

Why use an anti-cholinesterase to treat myasthenia gravis?

Decreases the catabolism of ACH in the synaptic cleft → allows more time for ACh to find a receptor

What are the primary neurotransmitters of movement?

GABA- Inhibitory

Glutamate - Stimulatory

Dopamine - both (dependent on receptor)

What are the primary structures of the Basal Ganglia?

Motor Cortex

Striatum

Globus Pallidus (int/ext; med/lat)

Substantia Nigra (compacta/reticularis)

Subthalamus

Thalamus

What are the aspects of the Basal Ganglia that will secrete GABA as its primary NT?

Striatum

Globus Pallidus (both)

What are the aspects of the Basal Ganglia that secrete Glutamate?

Motor Cortex

Subthalamus (indirect pathway)

Thalamus

Dopamine, in terms of the basal ganglia, will be released by what structure—AND directly affect what structure?

Substantia Nigra Pars Compacta- affects the striatum

Which dopamine receptor will stimulate the striatum to stimulate the direct pathway?

D1 (causes more release of GABA from the Striatum)

Which dopamine receptor will inhibit the striatum to inhibit the indirect pathway?

D2 (causes less GABA release from the striatum)

What is the function of the direct pathway

movement

What is the function of the indirect pathway

Inhibit Competing/Unwanted movement

What is the primary physiological flaw in Parkinson's Disease

Degeneration of nerve cells in the Substantia Nigra → decreased levels of DOPA → Indirect pathway becomes more influential than direct pathways

Is Parkinson's a hypokinetic or hyperkinetic disorder?

HYPOKINETIC

Where will the afferent neurons enter the Spinal Cord (what part of the spinal cord)?

Dorsal horn of the gray matter- different nuclei for different stimuli

After entering into job-specific nuclei in the DH of gray matter, typically the message will then move where??

Ascending tracts of the white matter → thalamus → sensory cortex (generally speaking)

Upon leaving the motor cortex, how does the motor message reach the effector?

Descending tracts of the white matter → Ventral Horn (specific for limb, flexor/extensor) → effector via efferent neuron

Which type of afferent neuron will be responsible for Joint and tendon sensation; proprioceptions/reflexes for posture-movement- coordination of movement?

Special somatic afferent

Which type of afferent neuron will be responsible for messages from areas of pressure/pain in skin

General somatic afferent

Which type of afferent neuron will be responsible for messages of smell and taste

Special visceral afferent

Which type of afferent neuron will be responsible for innervating viscera and communicating visceral sensations (distention, pressure, etc)

General visceral afferent

Which type of efferent neuron will be responsible for sympathetic/parasympathetic visceral innervation?

General visceral efferent

Which type of efferent neuron will innervate skeletal muscles and lower motor neurons (controlled by Upper Motor Neurons)

General somatic efferent

What is the ascending tract of pain and temperature?

Lateral Spinothalamic Tract- decussation in white matter

What is the ascending tract of vibration, discriminative touch?

Dorsal column medial lemniscus- decussation in medulla

What descending tract sends motor messages of Fine, Skilled Voluntary Movements?

Lateral Corticospinal Tract- decussation in medulla (pyramidal)

What are reflexes?

involuntary motor responses to stimulus at peripheral receptors

Name the type of reflex that initiates movements to protect us

Withdrawal reflex

Name the type of reflex that enable coordinated movement

Spinal Reflex/Stretch Reflex- one stimulatory and one inhibitory (ex: knee reflex- stimulate quad while inhibiting the hamstrings)

What are the steps of the knee-jerk stretch reflex

Stimulus (stretch) → Muscle Spindles-R stimulate an afferent neuron → Afferent sends AP to spinal cord (dorsal horn) → Synapse with Efferent neuron → Efferent to effector (muscle) → Reflex muscle contraction to act against the initial stretch → Knee Extension

What is the function of alpha motor neurons?

Muscle Contraction

What is the function of gamma motor neurons?

Muscle Spindles (reflex)

Which structure will wake the brain up (alertness)?

Reticular formation (Reticular Activating System)

Which structure acts as the primary cardio/resp center?

Medulla

What are the 2 primary arteries that help feed brain circulation

Vertebral Artery and Internal Carotid Artery

Which branch of the Circle of Willis will supply the temporal lobe (generally speaking)?

Middle Cerebral A

Which branch will supply the frontal to the parietal lobes (generally speaking)?

Anterior Cerebral A

Which artery will supply the occipital and lower temporal lobe structures?

Posterior Cerebral A

Within the circle of willis, where is the highest risk for aneurysm?

Anterior communicating A

What is the primary function of blood-brain/CSF brain barriers?

Regulation of ions, electrolytes, waste, neurotransmitters

Work via tight junctions, astrocytes, macrophages

*MS may be a result of immune markers crossing a leaking BBB and they start attacking the myelin sheath*

What aspect of the brain will enable coordination of movement; balancing wanted/and unwanted movements?

Basal Ganglia

What aspect of the brain will be the home plate for the descending tracts to start their journey to the spinal cord

Motor Cortex

What aspect of the brain will enable balance, learning of motor skills, and timing of movements?

Cerebellum

What is ataxia?

Lack of fine control of voluntary movements

What is monoplegia?

Affecting strength on one limb on one side of the body

What is tetraplegia?

Affecting strength of all limbs on both sides

What is hemiplegia?

Affecting strength of one side, both limbs

What is paraplegia?

Affecting strength either upper or lower bilaterally

Define Paresis

Muscular weakness/partial paralysis

What is the term for increased muscle size without accompanying strength increase?

Pseudohypertrophy (caused by fat deposition in muscular dystrophy)

What does flaccidity refer to?

Absent tone (floppy)

What motor neuron starts in the motor cortex and descends to the ventral horn of the spinal cord (or nuclei of CN)?

UMN- stays within the CNS

What motor neuron starts at CN nuclei or ventral horn of spinal cord and runs to effectors?

LMN- starts in the CNS and leaves

What are characteristics of UMN lesions?

Turn everything UP- spastic, slight muscle loss (no atrophy), positive Babinski, absence of fasciculations, strong tone (spastic paralysis), increased DTRs, clonus

Conditions: stroke, MS, cerebral palsy, spinal cord or brain damage

What are characteristics of LMN lesions?

Turn everything DOWN- fasciculations, flaccid paralysis, loss of muscle tone and strength, areflexia (decreased DTRs), neg Babinski

Conditions: GBS, botulism, Bell palsy, Cauda equina

Hyperreflexia will result from which type of motor neuron lesion?

UMN

Hypotonia will result from which type of motor neuron lesion?

LMN

Atrophy typically results from which type of motor neuron lesion?

LMN

Ischemia to the motor cortex will lead to what injury characteristic (think Lateral Corticospinal Tract)

UMN lesion- weakness, hypereflexia, hypertonia, contralateral TO THE LESION

Compression to the Ventral Root will lead to what injury characteristic (think Lateral Corticospinal Tract)

LMN- weakness, hyporeflexia, hypotonia, atrophy, ipsilateral TO THE LESION

What is special/different about the Facial Nuclei that enables the differences in UMN/LMN lesion outcomes?

Facial Nuclei has two halves- the Upper aspect is Bilateral, the lower aspect is contralateral

Name 3 influences on the LMN

Spinal reflex, Corticospinal Tract (and other motor tracts), Descending inhibitory tract from collateral innervations

True or false: the UMN is specific to the descending tract while LMN are general

True- this means multiple descending tracts can synapse with LMNs (If there is a lesion to an UMN of one tract, other tracts can still synapse with LMNs)

How are sensory neurons organized?

First order: from periphery to Dorsal Horn (with some exceptions)

Second order: from dorsal horn to thalamus

Third order: from thalamus to sensory cortex

Sensory fiber types for Muscle Spindle, GTO; Proprioception?

A-alpha

Tract- Dorsal Column Medial Lemiscus Tract

Sensory fiber type for Proprioception, pressure, touch, vibration?

A-beta

Tract- Dorsal Column Medial Lemiscus Tract

Sensory fiber types for pain, temperature?

A-delta and C fibers

Tract: spinothalamic tract

State the specificity theory

Specific receptors = specific messages

State the pattern theory

somatic sensations occur by a specific and particular pattern of neural firing

the spatial and temporal profile of firing of the peripheral nerves encode the stimulus type and intensity

State the gated theory

pain signals can be sent up to the brain to be processed to accentuate the possible perceived pain, or attenuate it at the spinal cord itself

'gate' is the mechanism where pain signals can be let through or restricted

What do C fibers release at the synapse in the substantia gelatinosa?

Substance P (slow stimulatory) then decussate and ascend on spinothalamic tract

What do A delta fibers release at the substantia gelatinosa?

Glutamate (fast stimulatory) then decussates and ascends on spinothalamic tract

What tract will pressure receptors stimulate?

Dorsal column medial lemniscus tract

Cuneatus (upper body sensory), Gracilis (lower body sensory), decussates in the medulla

How does the dorsal column medial lemniscus tract contribute to pain modulation?

Collateral interneurons from the DCML secrete GABA at the substantia gelatinosa to decrease pain perception

How do we modulate pain?

As pain messages reach the sensory cortex and tell our brain to recognize pain- descending inhibitory messages (via NT serotonin) are being sent to the dorsal horn to modulate pain