A&P: Misc

what is metabolism?

the process by which cells use oxygen to turn nutrients into chemical energy

• cells prefer oxygen [aerobic metabolism] because it provides the cells with 15x as much ATP as without oxygen [anaerobic metabolism]

what is aerobic metabolism? what are the waste products?

process that uses oxygen

• waste products are carbon dioxide and water

what is anaerobic metabolism?

process utilized any time available oxygen is limited to portions of the body

• very limited amounts of energy are released, so the body must quickly correct the oxygen deficiency or risk cellular death

• anaerobic metabolism can be supported in most cells for only 1-3 minutes

how long do the cells of the brain and heart survive without oxygen?

the cells of the brain and the heart are so specialized that they are unable to survive without constant supplies of oxygen → without oxygen, they die in 4-6 minutes

what is lactic acid?

a by-product that causes muscle burning during anaerobic exercise

what is pH?

the measure of acidity or alkalinity in a solution

• high in pH [>7.0] = alkaline

• low in pH [<7.0] = acidic

• neither acidic nor alkaline [pH 7.0] = neutral

what is normal human pH?

7.35 - 7.45 → cells want to exist in a near neutral environment

how does pH affect the blood?

• carbon dioxide is transported by combining with water to create carbonic acid, which is ACIDIC, which is more soluble in the plasma

• plasma also contains sodium bicarbonate, which is ALKALINE, and helps buffer or neutralize the acidic waste products of cells

if blood is acidic, respiratory centers in brainstem increase breathing to remove carbon dioxide → too much carbon dioxide removed [hyperventilation], body becomes too alkaline

what is ventilation? what is respiration?

ventilation is the movement of air between lungs and environment

respiration is the process of gas exchange

what is respiratory compromise? what does it result in?

the inability of the body to move gas effectively

• results in:

  • decreased level of oxygen in the body [hypoxia]

  • elevated level of carbon dioxide in the body [hypercarbia]

  • both hypoxia and hypercarbia

what are factors that impair ventilation?

blocked airways from:

• food

• foreign bodies [food or broken teeth]

• swelling in the airway

• trauma to the mouth or neck

• swallowing blood or vomitus

• tongue [MOST COMMON]

neuromuscular disease that interferes with the ability of the brain to send signals to the diaphragm

trauma that injures the phrenic nerve/damage to the brain stem

what can ventilation be affected by?

• any condition that results in loss of consciousness

• obstructed airways

• other factors such as drug overdose, trauma to chest wall, and allergic reactions

what are factors that impair respiration?

• change in atmosphere → air breathed in is 21% oxygen, air exhaled is 16% oxygen

• there is less oxygen in the alveoli to diffuse into the blood that passes by the lungs

• high altitudes = gas pressure changes → LOW atmospheric pressure can impair oxygen movement into the blood

• fluid in the alveoli

• clogged blood vessel brining blood back to the lungs will also affect the amount of gas that diffuses into and out of the blood

what is a fraction of inspired oxygen [FiO2]?

a way to express the amount of oxygen in the air

• oxygen = 21% of ambient room air, so FiO2 is .21

• oxygen from a nonrebreathing mask at 15 L/min is 90%, so FiO2 is 0.9

what is ventilation/perfusion mismatch [V’/Q’ ratio]?

describes how much gas is being moved effectively [ventilation] through the lungs and how much blood is flowing around the alveoli where gas exchange [perfusion] occurs

• mismatch occurs when one of the variables is abnormal

how does pulmonary embolism and pulmonary edema serve as examples of ventilation/perfusion mismatch?

• pulmonary embolism [blood clot from large vein clogs a branch of the pulmonary arteries, preventing blood flow to alveoli in the lungs] → part of circulating blood does not receive air → gas is not exchanged → Q [perfusion] is abnormal

• pulmonary edema [gas can’t move effectively through alveoli into lung due to fluid buildup] → blood passing through lung doesn’t get air exchange → no ventilation occurring in that portion of the lung → V [ventilation] is abnormal

what are the effects of respiratory compromise?

• oxygen levels fall and carbon dioxide levels rise → brain detects increase in carbon dioxide → brain increases its respiratory rate to get rid of excess carbon dioxide

• if carbon dioxide levels fail to return to normal, blood becomes more acidic → blood oxygen levels will begin to fall, causing brain to issue further commands to breathe

• decreased oxygen levels force cells into anaerobic metabolism → too much acid created, the pH of the blood drops → pH becomes too low, and cells die

what is systemic hypoperfusion?

also known as shock, this is condition where organs and tissues receive an inadequate supply of blood and oxygen [poor perfusion]

• can occur dur to inadequacy of CENTRAL or PERIPHERAL circulation

what 3 things is oxygen delivery directly related to?

• hemoglobin concentration: conc of blood cells within the blood

• oxygen saturation: amount of oxygen being carried by the blood

• cardiac output: pumping ability of the heart

what is hypovolemic shock? what causes it?

shock resulting from lack of blood volume → inadequate blood volume = inability to deliver sufficient oxygen and nutrients to body

• causes:

  • trauma [blood loss]

  • severe vomiting/diarrhea [substantial loss of water leads to decreased circulating blood volume]

what is cardiogenic shock? what causes it?

shock associated with impaired heart function → compromised heart function prevents wastes and nutrients from moving around the body effectively

• causes:

  • weakened heart muscles [due to myocardial infarction or other conditions]

  • very fast or very slow heart rate [can prevent blood from moving effectively, dropping blood pressure, and diminishing perfusion]

what is obstructive shock? what causes it?

shock resulting from blocked blood flow back to or through the heart

• causes:

  • severe lung collapse [tension pneumothorax, pushes on vena cava and prevents it from returning blood to the heart]

  • accumulation of fluid in sac surrounding the heart [prevents heart from filling]

  • large blood clot in pulmonary artery [pulmonary embolus, prevents right ventricle from pumping blood out of the heart into the lungs]

what is anaphylactic shock? what causes it?

shock resulting from severe allergic reaction

• causes:

  • severe allergic reaction [blood vessels dilate, blood pressure drops, perfusion decreases]

what causes septic shock? what causes it?

shock resulting from severe infection

• causes:

  • severe infection [blood vessels dilate and decreased blood pressure results, leading to dysfunction in multiple organ systems and death]

what is neurogenic shock? what causes it?

shock resulting from an injury to the nervous system

• causes:

  • high spinal cord injury [blood vessels below level of injury dilate, blood pressure drops, and perfusion decreases]

what are the effects of shock on the body?

inadequate perfusion [level of oxygen delivered to tissue falls] causes the cells to engage in anaerobic metabolism → baroreceptors detect decreased BP → epinephrine and norepinephrine are released → heart rate increases and blood vessels constrict

what is a compensatory mechanism for hypovolemic shock? why doesn’t this work in other forms of shock?

movement of interstitial fluid outside of the cells and blood vessels into the capillaries → helps restore some fluid volume so the heart has enough liquid to pump

in other forms, like septic and anaphylactic, the capillaries leak → intravascular volume moves into the interstitial space → loss of vascular fluid means there is less blood returning to the heart to pump

what is the problem with alteration of cellular metabolism?

impairment of cellular metabolism results in the inability to properly use oxygen and glucose at the cellular level

• anaerobic metabolism serves as a temporary backup system so cells can function at low energy levels for a short time, but there are drawbacks:

  • use of fats as alternate fuel supply = buildup of lactic acid = metabolic acidosis

  • more energy required than when glucose is used for fuel

  • decreased ability for the blood to carry oxygen to the cells → decreased functioning of oxygen within the cell

what occurs after cell death?

cell death is followed by necrosis → cell membrane becomes abnormally permeable, leading to an influx of electrolytes and fluids → cell and its components [organelles] swell and are ultimately destroyed