Medical Physiology Block 8 Week 2 Flashcards
Describe voluntary feedback-control mechanisms.
The sensory input involved in involuntary physiological feedback-control can also give rise to a conscious level, and if perceived as discomfort, can motivate us to take voluntary actions that make the surroundings more comfortable
Relate Environmental Temperatures to the Body’s Temperature and the effects seen with increasing/decreasing environmental temperatures
At an environmental temperature of 26-27 degrees Celsius and a relative humidity of 50%, a naked person is in a neutral thermal environment, feeling comfortable and being within the zone of vasomotor regulation of body temperature.
At 46 degrees Celsius, the heat is unbearable, and heat stroke is imminent- the body heats rapidly, and the loss of extracellular fluid to sweat may lead to circulatory collapse and death
At temperatures of 19-20 degrees Celsius, we feel cold, vasoconstriction occurs in the hands and feet, and muscles; may be painful
The partial pressure of gases inside the body depend on what? water vapor?
barometric pressure
temperature (in the body it is about 37 degrees Celsius)
What happens to lungs following immersion in water (breath-holding dive)?
compression
What is shallow water blackout?
Shallow water blackout is a loss of consciousness caused by cerebral hypoxia towards the end of a breath-hold dive in water typically shallower than five meters, when the swimmer does not necessarily experience an urgent need to breathe and has no other obvious medical condition that might have caused it.
What happens to lungs following immersion in water (breath-holding dive)? How do divers prevent this phenomenon?
compression; breathe compressed air (positive pressure breathing?)
What is narcosis?
Because of its high lipid solubility, nitrogen dissolves readily in adipocytes and in membrane lipids
resembles alcohol intoxication and gas anesthetics
Why is too much oxygen toxic?
damages the airway epithelium and smooth muscle and causes bronchiolar and alveolar membrane inflammation and, ultimately, pulmonary edema, atelectasis, fibrin formation, and lung consolidation (in addition to seizures and coma)
ROS
What happens to lungs following immersion in water (breath-holding dive)? How do divers prevent this phenomenon?
compression; breathe compressed air (positive pressure breathing?; helium)
Why is helium used in compressed air for divers?
Has only of a fraction of narcotizing effect of nitrogen (dissolves in the tissue to a less extent; lower density lowering effective airway resistance; less complications with decompression)
When mixed with some oxygen, it can prevent oxygen toxicity.
What is decompression sickness? How is it treated?
To allow enough time for the dissolved nitrogen to move from tissues to blood to alveoli, a diver must rise the surface slowly
Local formation of bubble in tissue (+ emboli)
type 1: niggles and bends
type 2: CNS and pulmonary edema
hyperbaric chamber
How does oxygen saturation of hemoglobin change at 3000 meters?
The oxygen saturation of hemoglobin in arterial blood decreases relatively little at altitudes up to 3000 meters.
How does the body compensate for hypoxemia at high altitude?
tachycardia (enhances oxygen delivery) and hyperventilation
stimulates peripheral chemoreceptors
How does the body compensate for hypoxemia at high altitude?
tachycardia (enhances oxygen delivery) and hyperventilation
stimulates peripheral chemoreceptors
How does the body acclimatize to high altitude?
During acclimatization, the pH of the CSF decreases, an effect that counteracts the respiratory alkalosis induced by the increase in ventilation and thus offsets the inhibition of central chemoreceptors
kidneys secrete bicarbonate (osmotic diuresis and alkaline urine)
What are long term adaptations to altitude?
hyperventilation and raised cardiac output cannot be sustained;
Renal hypoxia and norepinephrine stimulation the production and release of EPO from fibroblast-like cells in the kidney; EPO is a growth factor that stimulates production of proerythroblasts in bone marrow and also promotes accelerated development of RBCs from their progenitor cells
Rise in the blood volume of pulmonary capillaries and associated increase in capillary surface area available for diffusion; increase in depth of inspiration; right ventricular hypertrophy raises pulmonary arterial pressure and increases perfusion to the upper, well-ventilated regions of the lungs
Hypoxia promotes expression of oxidative enzymes in the mitochondria and thereby enhances the tissues’ ability to extract oxygen from the blood.
What is decompression sickness? How is it treated?
To allow enough time for the dissolved nitrogen to move from tissues to blood to alveoli, a diver must rise the surface slowly
Local formation of bubble in tissue (+ emboli)
type 1: niggles and bends
type 2: CNS, pulmonary, and circulatory abnormalities
hyperbaric chamber
What is acute or chronic mountain sickness?
drowsiness, fatigue, headache, nausea, and a gradual decline in cognition (reduced oxygen delivery to the brain); may result in cerebral edema through dilation of cerebral arterioles
Acute mountain sickness: headache, fatigue, dizziness, dyspnea, sleep disturbance, peripheral edema, nausea, and vomiting (may last up to 3-5 days); cerebral and pulmonary edema from hypoxia)
Chronic mountain sickness: overproduction of RBCs (polycythemia): exaggerated response (increased blood viscosity, thrombi, and congestive heart failure)
What is the effect of G-forces on the body?
G forces propel the body’s tissues in the direction opposite that of acceleration (compress soft tissue against underlying bone or pull tissues away from overlying structural elements (bone and stroma)
G forces tend to shift the blood volume away from the direction of acceleration
What are changes associated with weightlessness?
The cephalad shift of blood volume (away from the capacitance vessels of the legs) expands the central blood volume, increases cardiac preload, and increases the filtration of plasma water into the interstitium of the facial region
increased stretch of the right atrium causes release of ANP; stimulation of low-pressure baroreceptors inhibits the secretion of arginine vasopressin from the posterior pituitary (these two events increase excretion of salt and water by the kidneys)
no change in arterial pressure and cardiac output
Describe motion sickness during space flight.
Altered stimulation of the vestibular system in the absence of normal gravitational forces (resolve within 96 hours)
What physiological alterations occur with space flight?
reduction in body water content, plasma and RBC volume, total body nitrogen stores, muscle mass, and total body calcium and phosphate (bone loss is continuous)
What are complications with returning to Earth?
Reductions in cardiac preload, orthostatic tolerance, and exercise capacity
What is the consequence of hypothermia?
cardiac fibrillation
