Exam Study Notes

Neuron Firing and Neurotransmitters

Excitatory messages: Increase the likelihood of a neuron firing.
Local depolarization: Makes a neuron more likely to fire.
- Involves neurotransmitters.
Neurotransmitters: Assist in the local potential phase, promoting neuron firing.
Potential: The most potential for change exists at a negative value.
Hyperpolarization: Shifts to a negative value, creating the greatest membrane potential.
- Greatest membrane potential occurs at negative 70.

Electrolytes: Crucial for electrical charges.
- Sodium influx, potassium efflux.
Hyponatremia: Electrolyte dilution due to excessive water intake.
- Can impair muscular contraction and brain function.
Electrolyte replenishment: Necessary during fluid replacement (e.g., with IVs containing sodium and potassium).
Proper Function: Signals from the nervous and muscular systems require electrolytes.

Action potential: Not created in the soma (cell body).
Trigger zone: Located near the brainstem-axon junction.
- The site of action potential generation.
- Action potential then travels down the nerve.
Plasma membrane: Regulates charge with gated channels.
- Fluctuations occur until gates open for electrolyte influx.

Local action potential: Increases until the threshold is met.
Threshold: Required for an electrical message to be sent.
- All-or-nothing principle.
Resting membrane potential: Negative 70.
Threshold number: Required for action to take place.
Sodium ions: Facilitate depolarization.
Positive feedback: Occurs during spike at number three in the diagram.

Depolarization: Leads to action.
Cycle: Resting potential → action → return to baseline.
Threshold: The body allows more potassium exchange to generate charge.
Positive 35: The point where repolarization back to resting state is needed.

Refractory period: A recovery phase where the neuron cannot immediately refire.
Absolute refractory: Nothing will cause it to refire.
Recovery: Recovery is needed before the neuron can fire again.

Synapse: Electrical activity in the postsynaptic area.
Neurotransmitters: Cross over to cause muscle contraction.
Dendrites: Receive information and connect to the soma, leading to the trigger zone.
Electrical conversion: Electrical signals convert to chemical signals for communication with other cells.
Reservoir: Maintain a rotating reserve to ensure continuous messaging.
Pre-synaptic neuron: Where neurotransmitters are produced.
- Stimulation caused by their production.
- Must bind to specific receptors.

True reflex: Predictable motion response.
- Caused by pain or deformation (e.g., patellar tendon).
Reflex Components: Need a signal to occur.
- Quick, automatic motion.
- Stereotyped and predictable.

Signals: Arise from skin, muscles, or tendons.
Somatic receptors: Detect pain.
Afferent fibers: Communicate with the dorsal horn of the brain stem or spinal cord.
Muscle spindles: Important for reflexes.
Muscle compensation to avoid pressure on pain points.
Compensations can cause improper motion, different injury.
Relearning takes more time than learning.

Efferent: Away from the nervous system.
Muscle spindle engagement: Due to stretch receptors.
Proprioceptors: Maintain balance, monitoring the situation and providing feedback.
Equilibrium: Stabilizing that joint.

Location: Two finger widths below the patella.
Process: Quick reflex loop; monosynaptic.
Troubleshooting: If the reflex is difficult to elicit, create tension elsewhere (e.g., pull against fingers).
Withdrawal reaction