HBS Quiz 1 Quarter 3

STEPS:

  1. The resting membrane potential of a neuron is usually -70 mV

  2. A stimulus is applied to the cell, causing the membrane potential to rise. 

  3. After stimulation, the neuron reaches the threshold membrane potential (around -55 mV)

  4. When threshold is reached, a large number of sodium (Na+) channels open, allowing positively charged sodium ions into the cell. This causes depolarization of the neuron as the membrane potential rises to 0 and then becomes positive. 

  5. The action potential reaches its peak. Sodium channels close and potassium (K+) channels open, which allows potassium to flow out of the cell. 

  6. With potassium channels open, the relative voltage inside the cell falls in repolarization, and the neuron’s membrane potential drops back toward resting potential. 

  7. The open potassium channels cause the neuron to overshoot resting potential, and the cell becomes hyperpolarized, meaning the membrane potential has dropped below its resting potential. 

  8. The potassium channels close and the sodium-potassium pump allows the membrane to return to resting membrane potential, ready to be activated again. 

Key neurotransmitters

Acetylcholine: involved in muscle contraction, learning, and memory

Dopamine: plays a role in pleasure, motivation, mood, attention, memory, and movement

Gamma-aminobutyric acid (GABA): primary inhibitory neurotransmitter of CNS, GABA is essential for signal regulation and normal brain function

Glutamate: primary excitatory neurotransmitter in the brain, present in more than 90% of all brain synapses

Epinephrine and norepinephrine: excitatory neurotransmitters that play a role in fight-or-flight responses, to increase arousal, and attention

Serotonin: involved in regulation of mood and sleep, aids in digestion

Mechanisms:

Agonist: drug or substance that binds to receptor and causes same action as the substance that normally binds to receptor/ binds to synaptic receptor and increase effect of neurotransmitter (activates receptor to max. effect) (morphine)

Antagonist: substance that stops the action or effect of another/ binds to synaptic receptor, but they decrease effect of neurotransmitter (caffeine)

Inverse agonist: induces a response that’s different from an agonist (only for receptors that are always active, inverse agonist comes to stop the effect)/ binds with constitutively active receptors, and stabilize and reduce activity (diphenhydramine) 

Reuptake inhibitor: substance that increases the levels of neurotransmitters in the brain by preventing their reabsorptions/ blocking reuptake of neurotransmitters from synaptic cleft into nerve terminal (cocaine-on-the-daily)

Reaction:  thoughtful response to external stimuli in which the brain processes the nerve impulse before reacting

Reflex: automatic response to a stimulus that doesn't reach level of consciousness