Ch. 34 - Neurons, Epilepsy, Parkinsons's, MS

Pathophysiology Exam 3

What is the basic structural and functional unit of the nervous system?

The neuron

What are the three primary functions of a neuron?

Receive information

Process information

Transmit information

What are the three major types of neurons?

Sensory (afferent)

Motor (efferent)

Interneurons

What is the function of sensory (afferent) neurons?

They carry information from receptors to the central nervous system (brain and spinal cord)

What is the function of motor (efferent) neurons?

They carry signals from the central nervous system to muscles and glands

What is the function of interneurons?

They connect sensory and motor neurons within the CNS and process information

What are the four major parts of a neuron?

Dendrites

Cell body (soma)

Axon

Axon terminals

Which part of the neuron receives incoming signals?

Dendrites

Which part of the neuron contains the nucleus?

Cell body (soma)

Which part of the neuron carries the electrical impulse away from the cell body?

The axon

What is the function of axon terminals?

They release neurotransmitters into the synapse

What is the function of the myelin sheath?

It insulates the axon and speeds the transmission of nerve impulses

Which cells produce myelin in the central nervous system?

Oligodendrocytes

Which cells produce myelin in the peripheral nervous system?

Schwann cells

What are the Nodes of Ranvier?

Gaps in the myelin sheath where action potentials are regenerated, allowing impulses to “jump” rapidly along the axon

What is saltatory conduction?

The rapid jumping of an electrical impulse from one Node of Ranvier to the next, increasing conduction speed

What is a synapse?

The junction between two neurons or between a neuron and an effector cell where communication occurs

What are neurotransmitters?

Chemical messengers that transmit signals across the synapse

What is an action potential?

A rapid electrical impulse that travels along a neuron’s axon

Which ion is primarily responsible for depolarization?

Sodium (Na+)

Which ion is primarily responsible for repolarization?

Potassium (K+)

What is depolarization?

The process in which the inside of the neuron becomes more positive as sodium enters the cell

What is repolarization?

The return of the neuron’s membrane potential toward its resting state as potassium exits the cells

Which neurotransmitter stimulates skeletal muscle contraction?

Acetylcholine (ACh)

Which neurotransmitter is deficient in Parkinson’s disease?

Dopamine

What are dopamine’s primary functions?

Movement

Motivation

Reward

Coordination of voluntary motor activity

Which neurotransmitter primarily regulates mood, appetite, and sleep?

Serotonin

Which neurotransmitter is responsible for the body’s fight-or-flight response?

Norepinephrine

What is the major inhibitory neurotransmitter in the brain?

GABA (gamma-aminobutyric acid)

Why is GABA important?

It decreases neuronal excitability and helps prevent excessive electrical activity, including seizures

What is the primary excitatory neurotransmitter in the central nervous system?

Glutamate

What can excessive glutamate activity cause?

Neuronal overstimulation and injury (excitotoxicity), which can contribute to seizures and stroke related damage

Which neurotransmitter imbalance is commonly associated with seizures?

Too much glutamate or too little GABA

Which neurotransmitter deficiency is associated with Alzheimer’s disease?

Acetylcholine

Which neurotransmitter deficiency is commonly associated with depression?

Serotonin

What is epilepsy?

A chronic neurological disorder characterized by recurrent, unprovoked seizures caused by abnormal electrical activity in the brain

What is a seizure?

A sudden, uncontrolled burst of electrical activity in the brain that temporarily disrupts normal brain function

Does one seizure mean a patient has epilepsy?

No, a diagnosis of epilepsy usually requires two or more unprovoked seizures or one unprovoked seizure with a high risk of recurrence

What is the difference between a provoked and an unprovoked seizure?

Provoked: triggered by a temporary cause (e.g., hypoglycemia, alcohol withdrawal, fever, electrolyte imbalance)

Unprovoked: No immediate reversible cause; more suggestive of epilepsy

What causes a seizure at the cellular level?

Neurons fire excessively and synchronously, creating abnormal electrical discharges in the brain

Which neurotransmitter decreases seizure activity?

GABA (the brain’s primary inhibitory neurotransmitter)

Which neurotransmitter increases neuronal excitation and can contribute to seizures?

Glutamate

Why can a decrease in GABA increase seizure risk?

Without enough inhibition, neurons fire more easily, making uncontrolled electrical activity more likely

What are common causes of epilepsy?

Genetics

Stroke

Brain tumors

Traumatic brain injury

CNS infections (e.g., meningitis, encephalitis)

Developmental disorders

Unknown (idiopathic)

What are common triggers for seizures in people with epilepsy?

Missed medication doses

Sleep deprivation

Stress

Alcohol or drug use/withdrawal

Flashing lights (for some individuals)

Fever or illness

What are the two major categories of seizures?

Focal (partial) and generalized

Where do focal seizures begin?

In one specific area (one hemisphere) of the brain

Where do generalized seizures begin?

In both hemispheres of the brain simultaneously

Can a person remain conscious during a focal seizure?

Yes, some focal seizures occur with preserved awareness, while others impair awareness

Is loss of consciousness common during generalized tonic-clonic seizures?

Yes

What symptoms may occur during a focal seizure?

Muscle twitching

Numbness

Tingling

Visual changes

Strange smells or tastes

Emotional changes

Automatic repetitive movements (automatisms)

What is an aura?

A warning symptom that some people experience before a seizure, often representing the beginning of a focal seizure

Give examples of an aura?

Strange smell

Flashing lights

Deja Vu

Sudden fear

Metallic taste

What are the two phases of a tonic-clonic seizure?

Tonic phase and clonic phase

What happens during the tonic phase?

Muscles become rigid and the patient may cry out or fall due to sudden loss of muscle control

What happens during the clonic phase?

Rhythmic jerking of the arms and legs

What is an absence seizure?

A brief episode of impaired awareness, often lasting only a few seconds, with a blank stare and no postictal confusion

What is a myoclonic seizure?

Sudden, brief muscle jerks involving one or more muscle groups

What is an atonic seizure?

A sudden loss of muscle tone, often causing a person to collapse (“drop attack”)

What is the postictal phase?

The recovery period after a seizure when the brain returns to baseline function

What symptoms are common during the postictal phase?

Confusion

Drowsiness

Fatigue

Headache

Temporary weakness (Todd’s paralysis in some cases)

Why is patient safety especially important during the postictal phase?

Patients may be confused, weak, and at increased risk for falls or injury

What is status epileptics?

A seizure lasting 5 minutes or longer, or repeated seizures without recovery between them

Why is status epilepticus a medical emergency?

It can cause prolonged oxygen deprivation, brain injury, cardiovascular instability, and death if not treated promptly

What is the first-line medication for active status epilepticus?

A benzodiazepine (e.g., lorazepam or diazepam), followed by longer-acting anti seizure medication if needed

What is the primary diagnostic test for epilepsy?

Electroencephalogram (EEG)

What does an EEG measure?

The brain’s electrical activity

Why might an MRI be ordered for someone with seizures?

To identify structural causes such as tumors, strokes, or malformations

Why are blood tests important after a seizure?

To evaluate for reversible causes such as hypoglycemia, electrolyte abnormalities, or infection

What is the nurse’s first priority during a seizure?

Protect the patient from injury while maintaining the airway as much as possible

Should a nurse try to restrain a patient having a seizure?

No, restraining can increase the risk of injury

Should anything be placed in a patient’s mouth during a seizure?

No, do not place any objects or fingers in the patient’s mouth

What position should a patient be placed in after a seizure if possible?

Side-lying (recovery position) to help maintain the airway and reduce aspiration risk

What should the nurse document after a seizure?

Time seizure started and ended

Type of movements observed

Level of consciousness

Any aura or triggers reported

Injuries sustained

Postictal behavior

What is Parkinson’s disease?

A progressive neurodegenerative disorder that primarily affects movement due to the loss of dopamine-producing neurons in the brain

Which area of the brain is primarily affected in Parkinson’s disease?

The substantial nigra of the basal ganglia

Which neurotransmitter is deficient in Parkinson’s disease?

Dopamine

Why does dopamine deficiency cause movement problems?

Dopamine helps coordinate smooth, voluntary movement

Without enough dopamine, movement becomes slow, stiff, and difficult to control

Is Parkinson’s disease curable?

No, it is a progressive disease

Treatments help manage symptoms, but do not stop disease progression

What happens to dopamine-producing neurons in Parkinson’s disease?

They gradually degenerate and die

What effect does dopamine loss have on acetylcholine?

Dopamine normally balances acetylcholine

When dopamine decreases, acetylcholine activity becomes relatively increased, contributing to tremor and rigidity

Why are movements slow in Parkinson’s disease?

The basal ganglia cannot properly initiate and regulate voluntary movement because of dopamine deficiency

What protein commonly accumulates inside neurons in Parkinson’s disease?

Alpha-synuclein, forming Lewy bodies

Lewy bodies are a classic pathological finding in Parkinson’s disease

What is the greatest risk factor for Parkinson’s disease?

Increasing age

Is Parkinson’s disease more common in men or women?

Men

Name two additional risk factors for Parkinson’s disease?

Family history (certain genetic mutations)

Environmental toxin exposure (e.g., some pesticides)

What are the four classic motor symptoms of Parkinson’s disease?

Resting tremor

Bradykinesia

Rigidity

Postural instability

What mnemonic helps remember the four classic Parkinson’s symptoms?

Tremor

Rigidity

Akinesia/Bradykinesia

Postural instability

What is a resting tremor?

A tremor that occurs when muscles are relaxed and decreases with voluntary movement

Which hand movement is commonly described in Parkinson’s disease?

“Pill-rolling” tremor

What is bradykinesia?

Slowness of voluntary movement

What is akinesia?

Difficulty initiating movement or absence of movement

What is rigidity?

Increased muscle tone that causes stiffness and resistance to passive movement

What is “cogwheel rigidity”?

Jerky resistance felt when moving a patient’s limb due to rigidity combined with tremor

Why are Parkinson’s patients at high risk for falls?

Postural instability and impaired balance

Describe typical gait seen in Parkinson’s disease?

Shuffling gait with short, slow steps and decreased arm swing

What is festination?

An involuntary speeding up of steps while walking, making it difficult to stop

What is freezing?

A sudden inability to start or continue walking despite intending to move

Why do Parkinson’s patients often have a masked facial expression?

Reduced facial muscle movement due to bradykinesia

What is micrographia?

Abnormally small handwriting