Summary
NURP 404 Cellulitis Summary
- Course
- NURP 404
- Institution
- Simmons College
This is a comprehensive and detailed summary on Cellulitis for NURP 404.
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NUR404—Advanced Human PathophysiologyClinical Cases for Concept 1: Cell Injury & Cell Death Cases
Case 1.A—Heat Stroke
A 79-year-old woman with mild dementia and a previous cerebrovascular accident was living alone in a small,
poorly ventilated apartment when a home health aide, who visited once a week, found the apartment locked
during a heat wave. The health aide called the police, who forced an entrance and found the patient unresponsive
in her bed. The health aide reported that the patient was taking no medications. The patient was rushed to the
emergency department, where her temperature was 40.9oC. The patient was deeply comatose. Her blood
pressure was not measurable; her heart rate was 160. Her skin was hot and dry; except for obesity, the physical
examination was otherwise unremarkable. Her electrocardiogram revealed sinus tachycardia and diffuse ST and
Twave changes consistent with ischemia. While an intravenous line was being placed, ventricular fibrillation
developed. Despite ice packs, vigorous cardiopulmonary resuscitation, and fluid replacement, she died in the
emergency room.
1. Define negative feedback inhibition: in this process the end product of a metabolic pathway acts on the key
enzyme regulating the entry to the pathway which prevents more of the end product from being produced.
Describe the normal feedback loop for homeostasis: Homeostatic regulation is monitored and adjusted by the
1
receptor (receives info based on the internal environment), the 2command center (receives and processes the
info), and the 3effector (e.g. any muscle, organ, etc. that responds to the command center, opposing or
enhancing the stimulus). This ongoing process continually works to restore and maintain homeostasis.
When a change occurs in an animal’s environment, an adjustment must be made. The receptor senses the
change in the environment, then sends a signal to the control center (in most cases, the brain) which in turn
generates a response that is signaled to an effector. The effector is a muscle (that contracts or relaxes) or a
gland that secretes. Homeostatsis is maintained by negative feedback loops.
Define:
-Integrating center: “control center” (generally a region of the brain called the hypothalamus) receives
information from the sensors and initiates the response to maintain homeostasis.
-Regulated variable: A regulated (sensed) variable is one for which a sensor exists within the system and that is
kept within a limited range by physiological mechanisms. For example, blood pressure and body temperature
are sensed variables.
-Controlled variable: ?
-Afferent system: when communication flows TOWARD the control center from the receptor.
-Efferent system: when information flows FROM the control center to the effector. These two pathways are
part of the homeostatic control system.
-Effectors: an organ or tissue that receives information from the integrating center and acts to bring about the
changes needed to maintain homeostatsis. EX. The kidney, which retains water if the blood pressure is too low.
Given that the patient’s temperature was 40.9oC:
2. Explain what physiological changes take place in response to this elevated temperature. Relate this to
feedback regulation.
Temperature receptors in the skin communicate information to the brain (the control center) which signals
the effectors (blood vessel and sweat glands in the skin). As the internal and external environment of the
body are constantly changing, adjustments must be made continuously to stay at or near a specific value
(the set point).
To regulate body temperature, heat gain and loss are controlled by the autonomic nervous system's
alteration of (a) heat flow from the core to the skin via the blood and (b) sweating. Thermoreceptors in
the skin and body core provide input into the hypothalamic thermoregulatory center where this
information is processed, via a proportional control system, with a resultant signal for heat loss by the
thermoregulatory effector responses of sweating and alterations in skin blood flow. When temperatures
, rise, the body reacts by increasing blood flow to the skin's surface, taking the heat from within the body to
the surface. This means sweat. As the sweat evaporates, the body cools down. When the body cools down
and gets back to its “set point” then the feedback loop is closed.
3. Explain how these changes relate to the information that “her blood pressure was not measurable”? Relate
this to feedback regulation.
To accomplish this regulatory feat requires complex autonomic nervous system control of the heart and
various vascular beds. For example, during heat stress cardiac output increases up to twofold, by increases
in heart rate and an active maintenance of stroke volume via increases in inotropy in the presence of
decreases in cardiac preload. Baroreflexes retain the ability to regulate blood pressure in many, but not all,
heat stress conditions. Central hypovolemia is another cardiovascular challenge brought about by heat
stress, which if added to a subsequent central volumetric stress, such as hemorrhage, can be problematic
and potentially dangerous, as syncope and cardiovascular collapse may ensue. These combined stresses
can compromise blood flow and oxygenation to important tissues such as the brain. It is notable that this
compromised condition can occur at cardiac outputs that are adequate during normothermic conditions
but are inadequate in heat because of the increased systemic vascular conductance associated with
cutaneous vasodilation.
4. Explain why her heart rate is 160? Relate this to feedback regulation.
Bc of thermoregulatory effects of increased blood flow to the skin, there is a decrease of central blood
flow, this signals the heart to increase work by increasing heart rate and contraction of ventricles in order
to pump more blood due to the heart not having as much blood being returned to the heart to maintain a
state of homeostasis; therefore although the blood flow is needed to the skin, the heart now is signals
that there is less blood coming back to the heart therefore the response of the heart due to feedback is to
increase the rate so more blood comes back to the heart faster.
5. During heat stroke, a patient massively vasodilates to dissipate heat. Explain how this vasodilation, along with
dehydration due to fluid losses as a consequence of sweating, can lead to shock.
Shock is a life-threatening condition that occurs when the body is not getting enough blood flow. Lack of
blood flow means the cells and organs do not get enough oxygen and nutrients to function properly.
During this event the patient has lost most of their blood flow to their skin that allows the skin to sweat
and loose heat through evaporation of sweat. The negative effect of this is decrease blood availability
circulating back to the heart and other organs. Also, the blood is made up of mostly water which is leaving
the body as sweat so the patient is hypovolemic. Over time this state will starve the heart and other
organs resulting in shock.
Case 1.B—Myocardial Infarction
Maya Infarc is a forty-seven-year-old lawyer, who presented to the Emergency Department at the Brigham and
Woman’s Hospital with severe chest pain, which had been present for the past hour. She had previously been
evaluated for chest pain, having a one-year history of angina on exertion and a history of high blood pressure.
1. Define:
-Angina: Angina is chest pain or discomfort caused when your heart muscle doesn't get enough oxygen-rich
blood. It may feel like pressure or squeezing in your chest. The discomfort also can occur in your shoulders,
arms, neck, jaw, or back. Angina pain may even feel like indigestion. But, angina is not a disease.
-Infarction: is tissue death (necrosis) due to inadequate blood supply to the affected area. It may be caused by
artery blockages, rupture, mechanical compression, or vasoconstriction. The resulting lesion is referred to as
an infarct.
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