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Questions on Nervous: Amy Case Study 2 Assessment Answer

Case Study 2: Nervous

In a local game of netball, Amy got bumped and fell, badly injuring her ankle. She went to see a doctor who informed her that she would require surgery to fix two torn ligaments. The surgery would be performed under a general anaesthetic.

  1. Many anaesthetics work by making it harder for a neuron to reach threshold. Describe, in detail, the four stages of an actional potential (2 marks)
  2. Under a general anaesthetic a patient is largely paralysed. Considering neural pathways, does the ascending or descending pathway control skeletal muscle movement? And what is this tract called? (2 marks)
  3. To ensure that the anaesthetic was working before beginning the surgery, the attending anaesthetist tested Amy for the plantar reflex. What is a reflex, and give an example describing the stimulus, receptor, neural pathway and response (2 marks)
  4. Three days into her recovery, Amy goes back to the hospital with numbness in her injured foot and an inflamed scar. Describe a physiological reason how residual anaesthetic may cause numbness in Amy’s foot (2 marks)
  5. The doctors also believe that Amy’s scar is infected. Name and describe a structural mechanism that protects the central nervous system from infection (2 marks)

Answer

Case study 2: Nervous

1. Many anaesthetics work by making it harder for a neuron to reach threshold. Describe, in detail, the four stages of an actional potential 

Action potential has four stages in neuron transmission are resting potential, re-polarized, depolarization and again to resting potential. In case of resting potential, the potential latent membrane lies inside the inactive cells. Additionally, polarization in the neuron mechanism determines the spatial difference of the nerve cells in the context of structure, function and shape. This cell exerts polarity, which enhances the special function. Depolarization is the stimulus that starts in the cell membrane containing positively charged sodium ions5. Repolarisation is the electric gradient that exerts the threshold in which downswing started in the ionized channels. Back to the resting potential stage means to be refractory phase in which neuron goes back to rest state.

2. Under a general anaesthetic, a patient is largely paralysed. Considering neural pathways, does the ascending or descending pathway control skeletal muscle movement? And what is this tract called?

Yes, the descending or ascending pathway controls skeletal muscle movement in neural pathways. The tract in which the descending motor pathway occurs is known as the lateral corticospinal tract. Ascending pathway activates stimuli by CNS for controlling electrical impulses in the neck and head travel of receptor neuron by sensory pathway. Descending path travels down by electrical impulse between the corticobulbar tract and corticospinal tract via effector that is spinal cord. It forms brainstem at the spinal cord. This function operates in the region of lower medulla which includes decussates and cerebral cortex in the pyramid. Inside medulla oblongata, brain nerves process the descending pathway to the contralateral side.


3. To ensure that the anaesthetic was working before beginning the surgery, the attending anaesthetist tested Amy for the plantar reflex. What is a reflex, and give an example describing the stimulus, receptor, neural pathway and response

The reflex arc acts in five steps motor neuron, sensory receptors, integrating center, sensory neuron and effectors. Primarily sensory receptor respond against the stimulus through producing receptor potential or generator, then as sensory neuron axon conducts the impulses in between receptor to the integration center. Integrating center of CNS relay impulses from sensory to motor neurons and the integration from center to effectors enhances, based on which gland or muscle responds. Moreover, the reflex action is the mechanism that is controlled by the conscious part of the brain to formulate the reflex movements6. Stimulus is the result of reaction, energy or excitement. For example, the baby sees a shining object. Receptor is the chemical structures that receives or transmit signals, for example, β-adrenergic receptor. Neural pathway is the path that connects the nervous system by one another via tract, for example, optic nerve. Response from the nerve cells comes after a specific reaction, for example, ink blotting on paper.

4. Three days into her recovery, Amy goes back to the hospital with numbness in her injured foot and an inflamed scar. Describe a physiological reason how residual anaesthetic may cause numbness in Amy’s foot

Numbness in foot can be caused by residual anesthetic that lasts for long hours or even a day. It can be caused in the person due to the severe pain or cut on the lower part of the leg in which sensory receptors does not work. Moreover, while going through the residual anesthetic process, surgery is done on the foot7. Similarly, visceral and somatic senses can lead to numbness in body occurs that can be experienced temporary in the lower leg. The person suffers from severe pain due to nerve damage for that anesthesia was performed on blocked nerve.

5. The doctors also believe that Amy’s scar is infected. Name and describe a structural mechanism that protects the central nervous system from infection

Spinal cord and brain form central nervous system, which protects the structural mechanism during infection. Moreover, using the mechanical process, the living nerve tissue protects from the physical damages of the brain. Cerebrospinal fluid provides the brain with special structure along with protective chemical environment that helps to protect from buoyancy and shock absorption8. Further, barrier of blood brain helps to protect by impermeable capillaries and semipermeable membranes. Moreover, automatic and somatic peripheral system generates the process for the structural mechanism, which expands the central nervous system to the muscle fiber in vertebra.

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