Nerve Impulses and Neurological Disorders

Practice flashcards covering the mechanics of nerve impulses, synaptic transmission, and associated neurological disorders like MS, Parkinson's, and Alzheimer's.

What is a nerve impulse?

A nerve impulse is an electrical signal traveling along a neuron that facilitates thinking, movement, memory, emotion, and sensation.

What is the status of a neuron during resting potential?

When a neuron is not transmitting signals, it has an electrical charge of approximately $-70\,mV$. There is more sodium ($Na^+$) outside and more potassium ($K^+$) inside, maintained by the sodium-potassium pump.

What is the sequence of events during an action potential?

1. Stimulus, 2. Sodium channels open, 3. Sodium enters, 4. Depolarization, 5. Potassium exits, 6. Repolarization, 7. Resting state restored.

What does the all-or-none principle state?

Action potentials either occur completely or not at all; there are no partial nerve impulses.

What is saltatory conduction and what are its advantages?

In myelinated neurons, the impulse jumps between Nodes of Ranvier. This process is faster, more efficient, and conserves energy.

What is the difference between a presynaptic neuron and a postsynaptic neuron?

The presynaptic neuron is where the signal is initiated and neurotransmitters are released, while the postsynaptic neuron is the one that receives the signal.

How wide is the synaptic cleft and how does it compare to a human hair?

The synaptic cleft is a space less than $40\,nm$ wide, which is significantly smaller than a human hair, which is about $75,000\,nm$.

What three processes allow neurotransmitters to be cleared from the synaptic cleft?

Neurotransmitters are cleared via diffusion (drifting away), reuptake (taken back into the presynaptic neuron), or enzymatic breakdown within the synapse.

Which neurotransmitter is linked to muscle movement and memory, and what happens when there is too little of it?

Acetylcholine; too little is associated with memory impairment.

What are the characteristics of an electrical synapse compared to a chemical synapse?

Electrical synapses involve a direct flow of ions through gap junctions, are very fast, and usually bidirectional. Chemical synapses use neurotransmitters across a synaptic cleft, are slightly slower, and are usually one-way.

What occurs biologically in Multiple Sclerosis (MS)?

The immune system mistakenly attacks the protective covering around nerve fibers called myelin, slowing or blocking messages between the brain and body.

In Parkinson's disease, where does the damage mainly occur and what chemical is affected?

The damage mainly occurs in a brain area called the Substantia Nigra, where dopamine-producing cells die off.

What are the two hallmark pathological features of Alzheimer's disease found in the brain?

Sticky clumps called amyloid plaques and twisted fibers called neurofibrillary tangles.

What is the difference between generalized and focal seizures in epilepsy?

Generalized seizures affect the entire brain and can cause loss of consciousness or muscle spasms, while focal seizures originate in one part of the brain and may cause strange sensations or movements without necessarily affecting awareness.

What is the cause and primary symptom pattern of Myasthenia Gravis?

It is an autoimmune disease where the immune system attacks the connection between nerves and muscles. Muscle weakness typically gets worse with activity and improves after rest.

What are the roles of glial cells according to the lecture summary?

Glial cells support, nourish, protect, and insulate neurons.