Neuro Lectures

Calcium channels in neurons primarily play a role in neurotransmitter release at the synaptic terminals, which is why they are mainly concentrated at the endings of neurons.

The end-plate potential refers to the depolarization of the post-synaptic cell (muscle) that is always big enough to generate an action potential. It is not a chemical signal released by the pre-synaptic neuron, hyperpolarization of the post-synaptic cell, or initiation of a synapse breakdown process.

The End Plate Potential refers to the change in membrane potential at the neuromuscular junction, leading to muscle action potential and contraction. It is not related to muscle flexibility, electrical synapses, or a decrease in neurotransmitter release.

The correct equation for the reversal potential is given by I EPSP = g EPSP x (Vm - E EPSP). In this equation, I EPSP represents the current, g EPSP is the permeability for that ion, Vm is the resting membrane potential, and E EPSP is the potential generated through stimulus. When Vm is greater than E EPSP, it results in positive current and hyperpolarization. Conversely, when Vm is less than E EPSP, it leads to negative current and depolarization.

The correct answer explains that the reversal potential for Na/K+ channel is halfway between the equilibrium potentials of Na+ and K+, where neither ion is in equilibrium but the current is zero due to the influx of Na+ balancing the efflux of K+.

The correct answer can be found on slide 6-11 of the presentation. The reversal potential of EPP is 0 for the stimulus, meaning that as the membrane potential increases from -65 to more positive but less than 0, there is still depolarization but with reduced effect. Above 0, hyperpolarization occurs and the effect increases as the potential becomes more positive.

When the reversal potential is negative to the membrane potential, hyperpolarization occurs, causing an increase in the membrane potential. The current flows outward or in a positive direction away from the cell.

When the reversal potential is positive to the membrane potential, it leads to depolarization causing the inside of the cell to become more positive.

Reversal potential is equal to equilibrium potential when considering the behavior of one specific ion in a system. When multiple ions are involved or when the temperature is high, the relationship between reversal potential and equilibrium potential can change.

Understanding the dynamics of membrane potentials and depolarization is crucial in comprehending synaptic processes. The correct answer explains how these factors interact as membrane potential changes. The incorrect answers provide misconceptions or inaccuracies related to these concepts.

Myasthenia Gravis is an autoimmune disorder that affects the neuromuscular junctions, causing muscle weakness. The antibodies produced block the acetylcholine receptor, leading to a lack of stimulation for muscle contraction. Destruction of the acetylcholine receptors prevents the binding of acetylcholine to the post-synaptic neuron, resulting in the absence of action potentials.

Myasthenia gravis is an autoimmune disorder affecting the neuromuscular junction. Treatment options aim to improve neuromuscular transmission and manage the autoimmune component of the disease. Cholinesterase inhibitors, immunosuppressants, and thymectomy are commonly used interventions. Antibiotics, antidepressants, and antihistamines are not standard treatments for myasthenia gravis.

Lambert-Eaton Disease is characterized by progressive muscle weakness due to autoimmune destruction of calcium channels, leading to reduced release of ACh from presynaptic cells. Options 1, 2, and 3 are incorrect as they do not align with the known features of this disease.

Lambert-Eaton Disease is most commonly associated with small cell-carcinoma and other malignancies, rather than COPD, Type 1 diabetes, or multiple sclerosis.

Compound action potentials are commonly seen in neurological disorders like Multiple Sclerosis due to demyelination of nerve fibers.

The compound action potentials in normal state have the same and constant magnitude, while in Myasthenia gravis, it is reduced due to fewer acetylcholine receptors. In Lambert-Eaton Syndrome, the magnitude of EPP gradually increases due to calcium accumulation in cells. The incorrect answers provided do not accurately reflect the characteristics of the compound action potentials in the mentioned conditions.

Lambert-Eaton Disorder involves destruction of some of voltage-gated Ca+2 channels, leading to spontaneous release of neurotransmitter which binds to the receptors, resulting in no change in MEPP.

The correct criteria for identifying a transmitter include synthesis by pre-synaptic neuron, presence in pre-synaptic structures, mimicking post-synaptic action, and specific mechanism for termination. Testing involves stimulation, collection of extracellular fluid, assessing post-synaptic response, and verifying appropriate termination mechanisms.

Neurotransmitters can be removed from the synaptic cleft through various mechanisms, including being taken up by glial cells or entering circulation in the blood. Other incorrect options like undergoing spontaneous degradation in the cleft, being reabsorbed by the pre-synaptic neuron, or being converted into energy for the postsynaptic neuron do not accurately represent the processes involved in neurotransmitter clearance.

During a Monosynaptic Reflex (Hoffman), slowly increasing the stimulus intensity from 0 recruits the largest (1A) alpha fibers first, leading to an increase in response amplitude and duration as more motor units are involved. Therefore, the incorrect answers do not align with the actual process of recruitment and response during a Monosynaptic Reflex (Hoffman).

In a monosynaptic reflex, the Hoffman concept states that the M wave occurs first, followed by the H wave. This sequence is crucial in understanding the neural pathways involved in the reflex arc.

The correct approach involves stimulating a nerve and measuring the response in the muscle to observe the Monosynaptic reflex phenomenon.

EMG specifically measures the Hoffman reflex to check nerve damage or de-myelination, providing information on neuron damage and its location.

In a Hoffman reflex, latency remains constant because the distance of travel from one place to another is the same. Therefore, only frequency changes as more end plate potentials are generated with increased recruitment, while latency stays unchanged.

In the typical sequence, M wave occurs before the H reflex in neurophysiology experiments.