1. Why did Allen’s heart rate and blood pressure fall in this time of emergency (i.e. at a time when you’d expect just the opposite homeostatic responses)? Allen’s heart rate and blood pressure fell in this time of emergency because during the fall his medulla oblongata was damaged. The medulla oblongata is the relay station between the brain and spinal cord nerve signals. If the damage were extensive enough, Allen would have been declared brain dead. His return to homeostasis four days later indicates the damage to the medulla oblongata was minimal.
2. Upon admission to the hospital, Allen’s breathing was rapid and shallow. Can you explain why?
Allen’s breathing was rapid and shallow because Allen had a 5th cervical vertebra fracture causing damage to the phrenic nerve. The phrenic nerve originates in the C3-C5 vertebra, passes down between the lung and heart to reach the diaphragm and receives sensory information from it. The C5 vertebra fracture can cause damage to the phrenic nerve which will cause difficult, shallow, rapid breathing and even require the use of a ventilator.
3. Why did Allen lose some sensation in his arms and all sensation from the upper trunk down?
Allen lost some sensation in his arms and all sensation from the upper trunk down because C5 vertebra injuries often maintain shoulder and bicep control but no control below this area.
4. Why did Allen have dry skin and a fever upon admission to the hospital? Allen had dry skin and a fever upon admission to the hospital because he sustained spinal cord shock decreasing sympathetic motor neuron stimulation and reduced sweat production causing dry skin. Allen had also lost hypothalamic and sympathetic control which made his body adapt to the environmental temperature he was in thus causing a fever.
5. Based upon the physical exam findings, which vertebral bone do you think was fractured? Give reasons for your answer. The vertebral bone I think was fractured Is the C5 vertebral bone because injury to this area can cause quadriplegia allowing some elbow and shoulder control but no wrist or hand function. C5 injuries often allow the patient to maintain shoulder and bicep control but no control below that. A patient with a C5 injury may still be able to breathe on their own and speak without any trouble.
6. What is the normal pH of the blood? Why was Allen’s blood pH below normal? Allen’s blood pH was below normal because Hemoglobin, protein, and phosphates regulate blood pH. These “buffers” are the first line of defense when the blood pH is suddenly changed. Alan’s blood was suddenly acidotic due to shallow breathing causing an uneven gas exchange. His blood became too acidic due to the presence of too many H+ ions. These “Buffers” either accept or reject H+ ions in order to maintain the pH balance in the blood. In the case of Allen, the buffers were accepting the H+ ions and quickly restoring balance. However, this is a temporary solution because the buffers can become overloaded and no longer be of any use. In order to prevent overload, there is yet another buffer called the hydrogen carbonate ion (HCO?). The following reaction occurs
The amount of carbon dioxide we breathe out depends on how quickly we breathe. Faster breathing means lower levels of carbon dioxide. Normal breathing would mean that the buffer would only work to a certain extent. With more rapid breathing, the buffer can control the amount of the H+ ion returning to the blood. Allen’s blood pH was being controlled by how quickly he expelled his carbon dioxide.
7. What is the primary muscle of respiration? What nerve innervates this muscle?
The primary muscle of respiration is the diaphragm is. The phrenic nerves innervate the diaphragm.
8. Which spinal nerves contribute neurons to the nerve you named in question #7?
The spinal nerves that contribute neurons to the nerve named in question #7 are the cervical plexus and brachial plexus.
9. By four days after the injury, some of Allen’s signs and symptoms had changed. Allen’s arm muscles were still flaccid, yet his leg muscles had become spastic and exhibited exaggerated stretch reflexes. Use your knowledge of motor neural pathways to explain these findings. Some of Allen’s signs and symptoms had changed because his body was attempting to get back into homeostasis. The spinal shock was trying to resolve itself. Allowing damaged lower motor neurons to begin to fire impulses, causing spastic and exaggerated stretch reflexes and urinary incontinence. However, the upper motor neurons had not yet made such progress.
10. Why did Allen suffer from urinary incontinence? Allen suffers from urinary incontinence because the injuries he sustained caused him to suffer from areflexic bladder (urinary incontinence) caused by an autonomic dysfunction. Autonomic dysfunction causes the bladder to lose the ability to contract.