Nervous System Physiology - Advanced

Nervous System Physiology - Advanced

• Action potentials and graded potentials: Action potentials are initiated when graded potentials depolarize the membrane to threshold; they are the sum of several graded potentials. Graded potentials are not propagated over long distances and do not have refractory periods. Action potentials are propagated over long distances and characterized by a refractory period.

• Voltage-gated K+ channels and inactivation: Voltage-gated K+ channels do not require inactivation because their equilibrium potential (-60 mV) is higher than the threshold of the channels. In contrast, voltage-gated Na+ channels do require inactivation, which is a critical component of the refractory period of neurons.

• Refractory period: The refractory period is a result of Na+ channel inactivation, and contributes to unidirectional action potential propagation.

• Action potential sequence: The sequence of events in an action potential is: I - Graded depolarization to threshold, II - Activation of voltage-gated Na+ channels, III - Inactivation of voltage-gated Na+ channels, and IV - Activation of voltage-gated K+ channels. Then, the final step is V - Return to normal permeability.

• Refractory period and action potential initiation: Action potentials cannot be initiated during the refractory period, because voltage-gated Na+ channels are inactivated.

• Myelinated axons and continuous propagation: Continuous propagation does not occur in myelinated axons, because the myelin sheath insulates the axon, preventing the flow of ions across the membrane. Myelinated axons are faster because of saltatory conduction.

• Action potential vs. graded potential distance: Action potentials travel long distances due to propagation through refractory periods, while graded potentials do not propagate as they are not actively propagated and dissipate quickly.

• Action potential duration: The duration of an action potential is determined by the stimulus duration (not its strength).

• Graded potentials and receptors: Various stimuli (like neurotransmitters or sensory receptors) can initiate graded potentials.

• Chemical Synapses: Communication occurs in one direction at a chemical synapse, and it's not always propagated to the next cell. Generally a unidirectional transmission occurs.

• Termination of transmission at cholinergic synapses: transmission at cholinergic synapses is terminated by the breakdown of acetylcholine (ACh) by acetylcholinesterase (AChE).

• Slow postsynaptic receptors: Slow postsynaptic receptors are not always inhibitory, often have multiple responses & are not limited to the CNS. They are often used for neuromuscular transmission.

• Function of summation in neurons: Summation integrates multiple synaptic inputs to determine whether or not an action potential is triggered.

• Effects of alkalosis and acidosis on neural impulse conduction: The changes in H+ ions' concentration alter the potential difference across the neuronal membrane, therefore affecting conduction.

• Acetylcholine receptors and ligands: Atropine acts as an antagonist by binding to muscarinic receptors preventing the activation by acetylcholine. This prevents the receptor activation.

• Selective serotonin reuptake inhibitors (SSRIs): SSRIs act as agonists by prolonging the action of serotonin at synapses.

• Parkinson's disease and treatment: Parkinson's disease is treated with dopamine agonists because of deficient dopamine pathways in the brain.

• Tendons, reflex, and brain regions: Damage to the hypothalamus could impair food intake regulation.

• Rest-and-repose response: Decrease in heart rate, dilation of pupils and secretion of adrenaline are part of the rest-and-repose response.

Test your knowledge on advanced concepts of nervous system physiology, including action potentials and graded potentials. This quiz covers topics such as voltage-gated channels, refractory periods, and the sequence of action potential events. Perfect for those studying neurobiology or physiology at an advanced level.