Week 10: Neuro Patho

White matter

Composed of myelinated axons (fatty myelin sheath); found beneath the cortex in the brain and surrounding the gray matter in the spinal cord; functions in communication between gray matter areas and conducting nerve impulses.

Gray matter

Contains neuronal cell bodies, dendrites, unmyelinated axons, glial cells, and synapses; found in the outer layer and deep nuclei of the brain and inner butterfly shaped regions of the spinal cord; functions in processing information, integrating signals, and executing functions.

Frontal lobe

A brain lobe responsible for the production of speech and the motor cortex.

Parietal lobe

A brain lobe responsible for the sensory cortex and sensory association.

Temporal lobe

A brain lobe responsible for auditory association and Wernicke’s area (understanding speech).

Occipital lobe

A brain lobe responsible for visual association.

Three meninges

The protective layers of the brain comprising the Dura, Arachnoid, and Pia mater (which includes CSF that cushions the brain).

Limbic system

A system including the Amygdala, hippocampus, nuclei within the hypothalamus, and the cingulate gyrus (surrounding the corpus callosum); responsible for motion perception and regulation.

Axon

A projection from the cell body that can be short distance ($\text{interneurons}$) or long distance ($\text{projection neurons}$).

Axon terminals

The swelling at the end of an axon containing mitochondria and small transmitter-filled synaptic vesicles; they release transmitters onto the postsynaptic target cell across a narrow synaptic cleft.

Myelin

An insulating membrane that supports the propagation of the action potential.

Synapse

A point of contact between the presynaptic terminal of one neuron axon and the post-synaptic membrane of the target neuron.

Amnesia

Memory loss; one of the 5’s of Alzheimer’s.

Agnosia

Forgetting the purpose of familiar objects in the environment; one of the 5’s of Alzheimer’s.

Apraxia

Forgetting how to perform familiar functions; one of the 5’s of Alzheimer’s.

Apathy

Lack of concern for lost abilities; one of the 5’s of Alzheimer’s.

Aphasia

Lack of sensible speech or being mute; one of the 5’s of Alzheimer’s.

Depolarization

An action potential phase occurring when sodium rushes in and the charge becomes more positive (around $+30\,mV$).

Repolarization

An action potential phase occurring when potassium rushes in, pushing sodium out and returning the charge to negative.

Hyperpolarization

A state where the action potential becomes too negative for a brief time before returning to a resting state.

Ionotropic receptors

Receptors utilized for rapid transmission (e.g., GABA, glutamate, acetylcholine).

Metabotropic receptors

Receptors utilized for slow transmission (e.g., GABA, glutamate, acetylcholine, amines and peptides).

Afferent pathways

Neural pathways going towards the brain.

Efferent pathways

Neural pathways going away from the brain.

Dorsal horn

The posterior region of the spinal cord’s gray matter that processes sensory information including pain, touch, and temperature.

Spinal nerves

Consist of 31 levels: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.

CN I (Olfactory)

The cranial nerve responsible for the sense of smell; not routinely tested.

CN II (Optic)

The cranial nerve responsible for vision.

CN III (Oculomotor)

The cranial nerve responsible for pupillary constriction, eyelid elevation (opening the eye), and most extraocular movements.

CN IV (Trochlear)

The cranial nerve responsible for downward and internal rotation of the eye.

CN V (Trigeminal)

Motor: temporal and masseter muscles (jaw clenching), lateral pterygoids (lateral jaw movement). Sensory: facial sensation.

CN VI (Abducens)

The cranial nerve responsible for lateral deviation of the eye.

CN VII (Facial)

Motor: facial movements (facial expression, closing eye/mouth). Sensory: taste (salty, sweet, sour, bitter) on anterior two-thirds of the tongue and sensation from the ear.

CN VIII (Vestibulocochlear)

The cranial nerve responsible for hearing (cochlear division) and balance (vestibular division).

CN IX (Glossopharyngeal)

Motor: pharynx. Sensory: pharynx and larynx.

CN X (Vagus)

Motor: palate, pharynx, and larynx. Sensory: pharynx and larynx.

CN XI (Spinal accessory)

The cranial nerve responsible for the motor function of the sternocleidomastoid and trapezius.

CN XII (Hypoglossal)

The cranial nerve responsible for the motor function of the tongue.

Tension headaches

The most common type of headache; lasts minutes to days; bilateral with mild to moderate pressure; no nausea/vomiting; associated with photophobia and phonophobia.

Precentral gyrus

The primary motor cortex of the brain.

Postcentral gyrus

The primary sensory cortex of the brain.

Broca's area

The region of the brain responsible for the production of speech.

Wernicke's area

The region of the brain responsible for the understanding of speech.

Basal ganglia

Deeply buried brain structures consisting of the caudate, putamen, and globus pallidus.

Soma

The cell body of a neuron which contains the nucleus and many organelles.

Dendrites

Projections from the neuronal soma that receive synaptic inputs.

Action Potential Duration

The total duration of a neuronal action potential, which is less than $2\,ms$.

Potassium leak channels

Ion channels that create the resting membrane potential (RMP) in a neuron.

Ionotropic receptors

Receptors responsible for rapid signaling and the majority of second-to-second neuronal activity.

Metabotropic receptors

G protein–coupled receptors (GPCRs) that mediate slower, modulatory functions.

Glutamate

The main excitatory neurotransmitter used for rapid sensory and motor control.

GABA

The main inhibitory neurotransmitter in the brain.

Acetylcholine (ACh)

The neurotransmitter used for neuromuscular transmission, parasympathetic visceral control, and central modulatory actions.

Dopamine (DA)

A neurotransmitter involved in motor, endocrine, and motivational control.

Norepinephrine (NE)

A neurotransmitter involved in sympathetic visceral control, central arousal, and stress responses.

Serotonin (5-HT)

A neurotransmitter involved in central food intake regulation, arousal, mood modulation, and pain modulation.

Histamine

The neurotransmitter that initiates the awake state.

AMPA Receptor

$α$-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptor; a glutamate receptor whose activation increases sodium permeability and causes rapid depolarization.

NMDA Receptor

N-methyl-D-aspartate receptor; a glutamate receptor whose activation increases sodium and calcium permeability.

Epilepsy

A disorder characterized by recurrent seizures due to an imbalance of excitation and inhibition.

Raphe nuclei

Distinct brainstem clusters in the midbrain, pons, and medulla where serotonin ($5\text{-HT}$) neurons are found.

Ventral horn

The region of the spinal cord gray matter consisting of motor neuron and interneuron cell bodies.

Lower Motor Neurons

The final common pathway for all voluntary movement; damage causes flaccid weakness.

Upper Motor Neurons

Neurons in the precentral gyrus and neighboring cortical regions that send axons to synapse with lower motor neurons.

Parkinson Disease

A progressive disorder involving muscle rigidity, akinesia, and involuntary tremors, characterized by dopamine deficiency in the basal ganglia.

Myasthenia Gravis

An autoimmune disorder where $ACh$ receptor sites are weakened or destroyed by antibodies, leading to fatigue and muscle weakness.

Seizure Disorder

Recurrent paroxysmal events associated with abnormal electrical discharges of neurons in the midbrain, thalamus, or cerebral cortex.

Migraine without aura

The most common headache type, lasting $4\text{-}72$ hours, typically characterized by unilateral pain and N/V.

Cluster Headache

Debilitating, unilateral 'ice pick' pain occurring for weeks or months, often accompanied by ipsilateral redness and rhinorrhea.

Multiple Sclerosis (MS)

A disease involving progressive demyelination of the white matter, resulting in hard yellow plaques of scar tissue.

Amyotrophic Lateral Sclerosis (ALS)

A progressive neurodegenerative disorder (Lou Gehrig’s disease) causing loss of upper and lower motor neurons and eventual respiratory failure.

Ischemic CVA

A cerebrovascular accident occurring when emboli or plaques obstruct blood vessels, causing ischemia and tissue death.

Hemorrhagic CVA

Acute bleeding in the brain caused by trauma, hypertension, or aneurysm rupture.

Alzheimer's Disease

A progressive degenerative disorder of the cerebral cortex characterized by $ACh$ deficiency and the presence of tau protein neurofibrillary tangles.

Agnosia

Forgetting the purpose of familiar objects in the environment, one of the 5 A’s of dementia.

Apraxia

Forgetting how to perform familiar functions, one of the 5 A’s of dementia.

Neuritic plaques

Dense deposits of beta-amyloid protein found outside the neuron in Alzheimer’s disease.