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
How do you convert from Celsius to Fahrenheit?
2x - 10% + 32
What is partial pressure of oxygen at sea level? what is acceptable minimum? acceptable maximum of carbon dioxide?
160; 148; 3.8
What causes grey out? white out? black out? red out?
orthostatic hypotension (+G); hypoxia (+G), LOC (+G); -G-LOC
What does vascular remodeling mean?
angiogenesis
Why does core body temperature drop at altitude?
prolonged hypoxia decreases basal metabolic rate
What is cohort effect?
Different cohort have different environmental experiences (confounding for cross-sectional design)
What is selective mortality?
Individuals with risk factors for diseases that cause death at a relatively young age are underrepresented in older age groups (confounder for cross-sectional design)
What are examples of age-associated diseases?
Coronary artery disease, stroke, many cancers, type 2 diabetes, osteoarthritis, osteoporosis, cataracts, Alzheimer’s, and Parkinson disease
What are reactive oxidative species?
Hydrogen peroxide, hydroxyl radical, and superoxide anion radical, and nitric oxide (unpaired electron in the outer orbital)
Chain reaction that continues until two free radicals meet to create a product with a covalent bond
Damage proteins, lipids, and DNA
Why are ROS important for the body?
destruction of bacteria through NADPH oxidase and myeloperoxidase
What are antioxidant defenses?
SODs (produces hydrogen peroxide and oxygen), catalase (produces water and oxygen), and glutathione peroxidase (produces water and oxidized glutathione)
vitamin C and E
What is the oxidative stress theory?
an imbalance between the production and removal of ROS is the major cause of aging.
What is glycation and glycoxidation?
Nonezymatic reactions between the carbonyl groups of reducing of reducing sugars (glucose) and the amino groups of macromolecules (proteins and DNA) to form advanced glycation end products (AGEs)
Level of glycemia is a major factor in glycation, and periods of hyperglycemia are probably the reason glycation is enhance d in patients with diabetes.
What happens to DNA damage and mitochondrial DNA with age?
Accumulated DNA damage interferes with DNA replication and transcription, thereby impairing the ability of cells to function (decreased DNA repair)
Damage to mtDNA reduces ability of the mitochondria to generate ATP, and this decreased production of ATP results in loss of cell function (no histones)
Which proteins are susceptible to damage during aging?
elastin and collagen
How does lipid fluidity change with age?
stiffens (increase in cholesterol content and lipid oxidation)
What are telomeres?
Elements at the end of linear chromosomes and are composed of repeated specific DNA sequences and associated proteins (shorten in somatic cells following cell division)
cancer cells are rich in telomerase (resistant)
What is necrosis?
A cellular response to severe trauma that is manifested by uncontrolled breakdown of cellular structure, cell lysis, and an inflammatory response (cell swelling and loss of membrane integrity)
Describe apoptosis.
Requires ATP, gene driven, and is characterized by preservation of organelles, maintenance of membrane integrity, absence of inflammation, cell shrinkage, and fragmentation of the cell into multiple membrane-enclosed apoptotic bodies
What are the three types of apoptosis?
extrinsic, intrinsic, and DNA-damage (p53-mediated; p21)
Where does fat accumulate in aging individuals?
Accumulation of fat around the abdominal viscera and in abdominal subcutaneous tissue (decrease in extremities and face)
What is the result of photoaging?
(sun exposure) causes wrinkles Aging also reduces the number and function of sweat glands as well as the production of sebum by sebaceous glands
What happens to skin and musculoskeletal system with aging?
Aging thins the skin and causes the musculoskeletal system to become weak, brittle, and stiff
Define sarcopenia.
a steady loss in skeletal muscle mass, occurs with aging
Loss of number and atrophy of muscle fibers
Progressive loss of motor neurons innervating type 2 motor units, which are recruited less frequently
decrement in fine motor control
Starting in middle age, resorption exceeds formation, thus leading to a progressive loss in bone mass.
What are effects on CNS of aging?
Most sensory systems exhibit some deterioration with age (touch, spatial, vibrational, thermoregulation, hearing (particularly high frequency; loss of hair cells, nerve cells, or blood supply), vision (power of accommodation, reduced number of cones, decreased pupillary light response, and decreased sensitivity of rods), taste, and smell
slowing of reaction time (central processing)
How does aging affect cardiovascular and pulmonary systems?
Aging decreases the distensibility of the arteries (elevates systolic pressure, slightly decreases diastolic pressure, and thus widens pulse pressure)
Thickening of the left ventricular wall (hypertrophy)
The strength and endurance of the respiratory muscles decrease with age, primarily because of atrophy of type Iia muscle fibers
Lung volumes decrease with age (increased tendency for atelectasis because degeneration of collagen and elastin support structure); increased dead space
How does kidney function change with age?
The kidneys do not respond as effectively to changes in sodium load, do not dilute or concentrate urine as effectively, and also have a somewhat impaired ability to excrete potassium, phosphate, and acid.
The capacity and compliance of the urinary bladder decrease with advancing age, and the number of uninhibited contractions increases, thus making it more difficult to postpone voiding (residual volume increases)
How does liver function change with age?
Liver mass and hepatic blood flow, as well as the clearance of certain drugs, decreases significantly; delay in hepatic regeneration
What endocrine changes are consistent with aging?
Total energy expenditure decreases with age, primarily because of decreases in physical activity
Insulin resistance increases with age (increased adiposity; increased LDL)
Decreased growth hormone and IGF-1
DHEA decreases
PTH INCREASES
T/F: Caloric restriction slows aging?
T; hormesis
What is biological age?
senescence
What happens to skin and musculoskeletal system with aging?
Aging thins the skin and causes the musculoskeletal system to become weak, brittle, and stiff
Decreased melanocytes reduces photoprotection, hair grays
decreased Langerhan’s cells
Are there biomarkers for aging?
No
How is the response to exercise change with aging?
maximal oxygen uptake decreases; heart cannot increase heart rate as much; increased stroke volume
T/F: Caloric restriction slows aging?
T; hormesis and decreased insulin signaling
What is a mechanism associated with hormesis?
Heat shock proteins are upregulated by stress and act as chaperone proteins for misfolded proteins
According to the Gompertz curve, the age of lowest probability of death is?
between 5 and 10 years of age
