Question

A tuning fork is placed against the forehead of a patient. The sound is loudest in the left ear. What can you determine about the patient’s hearing? What is happening in the left ear and the right ear? Begin your Internet search with the National Institute of Deafness and Other Communication Disorders website. Also, search for deafness, hearing, and cochlea.

Be detailed in your explanation and support your answer with facts from your textbook, research, and articles from scholarly journals. In addition, remember to add references in APA format to your posts to avoid plagiarism. Review of APA format: http://bit.ly/33oeRJj

Phenytoin (sodium channel blocker) and ethosuximide (calcium channel blocker) are anti-seizure drugs that stop seizures from happening. These drugs work by inhibiting electrical impulses (action potentials) from occurring.

Explain the importance of sodium and calcium channels on a neuron and the reasons why action potentials do not occur when these channels are inhibited. Be sure to include the phases of an action potential, the channels involved, and the importance of an action potential.

Answer 1

This test is called the weber test.

It is a bedside test to determine the cause of hearing loss ( conductive vs sensorineural)

Intepretation - The interpretation of this examination depends upon whether the patient complains of hearing loss in the left ear. This raises two possibilities

1. The patient complains there is reduced hearing the left ear
2. The patient complains there is reduced hearing int he right ear

let us see both the situations

• The patient complains there is reduced hearing the left ear ( therefore the left ear is the affected ear)

As the patient complains he hears better in the affected ear - it means that the patient has conductive hearing loss in the affected ear

Reason - due to conductive hearing loss, there is no air conduction of sound to the cochlea. There is only bone conduction. This ear is masked as a result sound wave cannot reach via air conduction

• The patient complains there is a reduced hearing in the right ear

As the normal ear hears better - this is suggestive of sensorineural hearing loss in the affected ear

Answer 2

The action potential is the rapid rise and fall of resting membrane potential in response to a stimulus

The resting membrane potential fo a neuron is -55 mV to - 75 mV. This is because

• due to the activity of Na-K ATPase pump on the neuronal cell membrane
• This removes Na+ out of the cell and Moves K + into the cell.

On exposure to stimuli, action potential results. it has the following phases

Depolarization

1. After exposure to electrical stimulus, there is opening of the voltage-gated Na+ channels
2. This leads to an influx of Na+ ion
3. This increases the membrane from negative to positive
4. Once the membrane potential reaches a threshold, more and more Na+ channels open
5. This continues until all Na+ channels are open.

Repolarization

1. When all the Na+ channels open, there is a change in membrane potential from negative to positive.
2. This leads to inhibition of the Na+ channels.
3. The K+ channels now open
4. The move the intracellular K+ out of the cell.
5. The makes the membrane potential negative

Hyperpolarization

1. This expulsion of K+ continues even after the neuron membrane potential has reached resting membrane potential
2. This is called hyperpolarization

This is the role of Na in action potential in a nerve

Calcium plays an important role in is Action potential transmission across a synapse.

1. When an action potential reached the axons of the presynaptic nerves, there is opening up of Voltage-gated - calcium channels
2. Calcium enters the axon terminal
3. It causes the neurotransmitter containing vesicles to release the neurotransmitter into the synaptic cleft.
4. This neurotransmitter binds to the postsynaptic receptors. ( present on the dendrite of the postsynaptic neuron)
5. This stimulates an action potential in the post-synaptic neurons.