Describe how a nerve impulse is transmitted from one neuron to the next
The transmission from one neuron to another is characterized by exchange of electric charge across the membrane of each neuron (Fields, 2014). An unstimulated neuron would be polarised (McCance 2014). In the polarized state, there is difference in the electric charge across the membrane. However, during exchange, a neuron is said to undergo polarization, wherein there is an excess of Na+ (sodium ions) outside and excess of K+ (potassium ions) on the outside (Fields, 2014). Nerve impulse is transmitted through the process of polarization, repolarization, and hyperpolarization (McCance 2014).
Compare the structure and functions of the CNS and PNS.
The nervous system comprises of the central nervous system (CNS) and the peripheral nervous system (PNS). Each having its unique function and structures (McCance 2014). The 2 main components of the CNS are the brain and spinal cord while those of the PNS are the motor and sensory division (McCance 2014). The CNS is the primary command station of the nervous system wherein impulses are exchanged between the brain and spinal cord. However, the network system other than the CNS is the entire PNS which sends messages to different parts of the body. The PNS is more complex and comprises of skin, tissues, muscles, and organs (McCance 2014).
What is the probable diagnosis for this man\'s condition?
The man is most likely suffering from sleep apnoea (sleepiness) or narcolepsy (McCance 2014). It is condition wherein certain parts of the brain are affected that causes uncontrolled sleep (Burgess & Scammell 2012). The man has reported to suffer from daytime sleepiness. He reports to feel weak and fall once he is awake, a key clinical feature of cataplexy among patients with narcolepsy (McCance 2014).
What parts of the person\'s brain could have been affected?
Based on current evidence, researchers suggest that patients with narcolepsy often have a selective loss of neurons in the hypothalamus (McCance 2014). These neurons play a key role in maintaining circadian rhythms and produce orexin/hypocretin neuropeptides (McCance 2014). Some researchers report that the loss of orexin could cause symptoms of sleepiness Researchers observed midbrain T2-hyperintense lesion in a patient with chronic narcolepsy which suggest that the midbrain may also be affected (Renna, et al. 2016).
What sleep state do these symptoms resemble?
Researchers suggest that patients with narcolepsy may not necessarily have disruption in their circadian rhythms or sleep homeostasis (McCance 2014). The symptoms of narcolepsy are associated with REM sleep, when all the muscles of the body are relaxed (Burgess & Scammell 2012). Cataplexy in patients occurs due to the inappropriate activation of the pontine circuits that causes atonia during REM sleep (McCance 2014)
How would an electroencephalogram look like during the sleep condition of this patient?
The EEG findings in most patients would result in drowsy-state, wherein no significant abnormal findings are observed (McCance 2014). During sleep onset REM, most patients had EEG response to stimuli is decreased in such patients (McCance 2014).
What type of treatments (physical or chemical) would you prescribe for the patient?
Based on current evidence, patients with narcolepsy are recommended stimulants such as modafinil or armodafinil, Selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine or venlafaxine, and/or tricyclic antidepressants such as protriptyline, imipramine and clomipramine (McCance 2014).
References
Burgess, C. R., & Scammell, T. E. (2012). Narcolepsy: neural mechanisms of sleepiness and
cataplexy. The Journal of Neuroscience: The Official Journal of the Society for
Neuroscience, 32(36), 12305–12311.
Forrest, M. D. (2014). The sodium-potassium pump is an information processing element in
brain computation. Frontiers in Physiology, 5, 472.
McCance K (2014). Pathophysiology: The Biologic Basis for Disease in Adults and Children.
St Louis, United States. Elsevier - Health Sciences Division.
Renna, R., Koudriavtseva, T., Renna, A., & Renna, S. (2016). Narcolepsy in midbrain
structural lesion. Annals of Indian Academy of Neurology, 19(3), 404–405.
Remahl, S., Angeria, M., Remahl, I. N., Carlstedt, T., & Risling, M. (2010). Observations at
the CNS–PNS Border of Ventral Roots Connected to a Neuroma. Frontiers in Neurology, 1, 136.
