Patho exam 2

neurotransmitter

Chemical messenger that transmits signals across synapses between neurons and other cells. Ex: Acetylcholine

Reflex

Bypasses the brain entirely; a stimulus activates a sensory receptor, the sensory neuron carries the signal to the spinal cord, inside the spinal cord the signal synapses directly onto a motor neuron, motor neuron carries the signal out to the muscle

Pyramidal Tract

Direct route single-relay pathway, brainstem and down, crosses over to the other side at the medullary pyramids (decussation)

Extrapyramidal System

Indirect route multi-relay pathway, travels through cerebellum, what makes movements smooth and controlled, Ex: Parkinson’s disease and Huntington disease

Synaptic cleft

How the signal crosses from one neuron to the next; essential for directional, regulated communication between neurons or between neurons and muscles/glands/etc.

Depolarization

opens voltage gated calcium channels, and Ca2+ flows into the terminal

Acetylcholine

Neurotransmitter at every neuromuscular junction and also active in CNS circuits for memory and arousal; Type: Excitatory; Ex: Myasthenia gravis (destorys receptor site)—antibodies block the ACh receptor itself

Dopamine

Excitatory neurotransmitter coordinates smooth purposeful movement; Ex: Parkinson’s disease—loss of dopamine-producing neurons in the substantia nigra

GABA

Inhibitory neurotransmitter; brain’s main “brake”; Ex: insufficient GABA activity is linked to seizure activity

Glutamate

Excitatory neurotransmitter responsible for being brain’s “gas pedal”—the primary excitatory transmitter in the CNS; excess glutamate release contributes to neuronal injury after stroke or trauma (excitotoxicity)

Norepinephrine

Excitatory; vasoconstrictor; drives alertness, arousal, and the fight or flight response; involved in mood regulations—a target of several psychiatric meds

Serotonin

Inhibitory; regulates mood, sleep-wake cycles, and appetite; low activity linked to depression—target of antidepressant meds

Blood brain barrier (BBB)

tightly joined capillary cells that control what can pass from blood into brain tissue; protects brain from toxins, pathogens, and some meds; when damaged by stroke, trauma, etc. the barrier becomes leaky letting things get through barrier

Myelin sheath

insulates axon forcing electrical signal to jump from node to node (saltatory conduction) which makes conduction fast

Demyelination

Ex: multiple sclerosis; strips just the sheath not the axon itself; signal conduction is slowed or blocked, but remyelination is possible early in the disease

The Axon

the actual wire that carries the signal to the destination; usually more permanent and severe damage; Ex: chronic/ progressive MS, ALS

Multiple Sclerosis (MS)

an autoimmune demyelination process; targets CNS (upper motor lesion) immune system mistakenly attacks myelin sheath; relapsing-remitting cycle

symptoms: vision changes, weakness, FOOT DROP, fatigue, coordination problems; give corticosteroids and manage symptoms

Guillan-Barre syndrome

an autoimmune attack on peripheral myelin; molecular mimicry—antibodies made against infectious agent cross react with peripheral nerve myelin

the immune system strips myelin from peripheral nerve;

symptoms start from bottom to top of body (symmetric and ascending weakness) FLACCID weakness; can progress to involve the respiratory muscles—WATCH FOR BREATHING PROBLEMS

Myasthenia gravis

an autoimmune disorder that attacks the neuromuscular junction specifically— attack acetylcholine receptors at NMJ; muscle weakness that worsens with activity and improves with rest AND affects eye and facial muscles first (facial and eye DROOPING)

Parkinson’s disease

a dopamine supply problem occurring in the lower motor— neurotransmitter is not being made here; progressive loss of dopamine producing neurons in deep brain structure—SUBSTANTIA NIGRA

Signs: resting tremor, rigidity, bradykinesia, postural instability

ALS

the one disease that attacks both central and peripheral motor neurons at once; the motor neuron ITSELF is dying in both the upper and lower pathway

pt is aware of their health decline—eye movement, cognition, bowel/bladder control, etc. stay intact; signature findings: spasticity, hyperreflexia, Babinski (UMN) muscle wasting, fasciculations, and weakness (LMN)

Autonomic Dysreflexia

most dangerous vascular complication; only with injury AT T6 or ABOVE; symptoms: sudden/severe hypertension

Decorticate

arms flex IN toward the core

Decerebrate

arms AND legs rigidly extended; WORSE than decorticate

CCP formula

CCP = MAP - ICP

Ischemic stroke

caused by blood clot/blocked blood vessel; 85% of strokes are this kind; time sensitive clot-dissolving therapy (tPA) may be good option; MUST get a head CT to rule out bleeding before giving any clot-dissolving meds

Hemorrhagic stroke

caused by a blood vessel rupturing and bleeding out directly into or around brain; 15% of strokes (rare and usually worse); clot dissolving therapy is a contraindicator—would worsen the bleeding

The core infarct: inside an ischemic stroke

near total loss of blood flow; ATP depletion cascade; this happens within minutes and is essentially irreversible almost immediately

The Ischemic Penumbra: ischemic stroke

surrounds core; blood flow is reduced but not completely cut off; cells here are dysfunctional and “electrically silent’ but still metabolically alive; can recover if blood flow is restored in time

Expressive Aphasia

Broka’s area; can understand but can not produce speech

Receptive Aphasia

Wernick’s area; can speak but does not understand speech

Seizures

a symptom not a diagnosis on its own; results from abnormal, excessive, synchronized electrical activity among brain neurons

too little inhibitory GABA OR too much excitatory Glutamate

Focal seizures start in one specific area and may or may not spread

Generalized seizures involve both hemispheres of the brain from the onset

Tonic-clonic seizure

“Classic” seizure—stiffening of limbs and jerking motion

Absence seizure

A brief lapse in awareness often with blank staring—easily mistaken for daydreaming

Myoclonic seizure

Sudden, brief muscular jerks, often in one limb or one muscle group; WITHOUT loss of consciousness

Atonic seizure

Sudden loss of muscle tone—”fall attacks”

Kernig’s signs

pt supine with hip flexed 90 degrees—knee can not fully extend

extending the knee in this position stretches the inflamed meninges further

Brudzinski’s sign

passive flexion of the neck causes flexion of both knees

flexing the neck stretches the inflamed meninges along the spinal cord, the body flexes the legs to shorten and relieve that stretch

Glioma brain tumor

arise from glial (support) cells

Glioblastoma, the most dangerous and aggressive primary brain tumor

Meningioma brain tumor

arise from the meninges, usually slow growing and often benign

Pituitary adenomas

can cause hormonal effects in addition to local pressure symptoms