Exercise and shock Flashcards
- What is the definition of Shock?
Inadequacy of blood flow which results in inadequate delivery of oxygen and nutrients throughout the body to the extent that the tissues are damaged
- What are the compensatory mechanisms that are active in hemorrhagic shock?
- Baroreceptor Reflexes
- Chemoreceptor Reflexes
- Cerebral Ischemic Response
- Reabsorption of Tissue Fluids
- Endogenous Vasoconstrictor Substances
- Renal Salt and Water Conservation
- In shock where is vasoconstriction most prominent?
- Cutaneous vascular bed
- Skeletal muscle vascular bed
- Splanchnic vascular bed
- Blood flow is preferentially redistributed to which body organs in shock states?
Blood flow through the heart and brain is maintained essentially at normal levels as long as the arterial pressure does not fall below about 70 mm Hg.
- Approximately how much fluid can be reabsorbed at the capillary level to help maintain blood volume?
1 L of fluid/hour
- What are the decompensatory mechanisms that occur in progressive shock?
- Cardiac depression
- vasomotor failure
- acidosis
- blood clotting abnormalities
- reticulo-endothelial system
- CNS depression
- Cellular deterioration
- reduced organ perfusion from stimulation of inflammatory process, clotting
- What are the positive feedback decompensatory mechanisms that are triggered by severe hypotension?
The shock itself leads to more shock! That is, the inadequate blood flow causes the body tissues to begin deteriorating, including the heart and circulatory system. This deterioration causes an even greater decrease in cardiac output, and a vicious cycle ensues, with progressively increasing circulatory shock, less adequate tissue perfusion, more shock, and so forth until death. It is with this late stage of circulatory shock that we are especially concerned, because appropriate physiological treatment can often reverse the rapid slide to death.
- What occurs at the cellular level that leads to irreversible shock?
Depletion of cellular high-energy phosphate reserves
- How much can muscle blood flow be increased during extreme exercise in the well-trained athlete?
50 -80 ml/min/100 g of muscle (or 6-7 times)
blood flow increases to 15-20% above resting
- How does muscle contraction augment venous return?
Contracting muscles help pump blood though the system along with one way valves in veins
- What happens to blood flow in muscle tissues during exercise?
- Blood flow may increase 15-20 times above resting level
- Decreased oxygen in muscle greatly enhances flow
(intermittent blood flow during muscle contraction)
- How does capillary recruitment help delivery oxygen to muscle tissues during exercise?
• During rest, some muscle capillaries have little or no flowing blood. During strenuous exercise, all the capillaries open. This opening of dormant capillaries diminishes the distance that oxygen and other nutrients must diffuse from the capillaries to the contracting muscle fibers
- Increase surface area for diffusion
- Shorten the distance for diffusion
- What factors facilitate oxygen unloading from hemoglobin to the tissues during exercise?
- Contracting muscle avidly extracts oxygen from the blood
- A rightward shift reduces affinity of O2 to HGB
- Reduced pH
- Lactic acid
- Increased pCO2
- What factors enhance blood flow at the tissue level?
Dilation of the resistance vessels d/t reduced oxygen tension in the tissues and release of vasodilators (adenosine, lactic acid, potassium), all which increase BF
- What are the beta-2 effects of epinephrine on skeletal muscle?
Vasodilating effects
accept more blood and offload more oxygen
- Does cardiac output increase or decrease during exercise?
Increase, correlated with increased HR
- How is the change in cardiac output correlated to heart rate changes during exercise?
- CO increased in proportion to degree of exercise
* Increase CO with exercise correlates with an increase in HR
- Does mean arterial pressure increase or decrease during exercise?
- Rises tremendously at the onset of heavy exercise
- Sympathetic stimulation that contracts the veins and other capacitative parts of the circulation
- Tensing of the abdominal and other skeletal muscles of the body compresses many of the internal vessels
- What effect does the change in mean arterial pressure have on muscle blood flow? Why?
MAP rises even though there is a reduction in SVR in the body musculature
Vasoconstriction in inactive tissues is important for maintaining normal or increased BP during exercise. This provided a higher perfusion pressure which results in greater blood flow through active tissues
- What effect does the sympathetic nervous system have in the kidneys, splanchnic beds, and inactive muscle during heavy exercise?
diverts blood away from these areas
- What factors enhance venous return during exercise?
- Sympathetically-mediated constriction of the capacitance vessels
- Decreased systemic vascular resistance in the muscles
- Contracting muscles help pump blood in the veins back to the heart
- Deeper, more frequent respirations decrease intra-thoracic pressure and enhance flow of venous blood to the heart
