Question

(4pts) For the condition of hypertension, identify 2 possible causes and the predicted effect on cardiac output. How would the body respond to this condition? Be sure to explain your answer in the context of a homeostatic feedback loop, and to identify if reactions are local or reflex control.

4. (2pts) What is the role of blood volume in the long term regulation of arterial pressure?

5. (2pts) In the case of rapid blood loss, do you expect that heart rate to increase or decrease? Why?

Answer 1

HYPERTENSION

A condition in which the force of the blood against the artery walls is too high.Usually hypertension is defined as blood pressure above 140/90, and is considered severe if the pressure is above 180/120.High blood pressure often has no symptoms. Over time, if untreated, it can cause health conditions, such as heart disease and stroke.

There are many possible cause for hypertension like stress,smoking,older age,genetics etc...

In most forms of hypertension, the hypertensive state is maintained by an elevation in blood volume, which in turn increases cardiac output by the Frank-Starling relationship. Vasodilator drugs, which decrease systemic vascular resistance, are commonly used to treat hypertension.

The renin‐angiotensin‐aldosterone system of the kidneys regulates blood volume. In response to rising blood pressure, the juxtaglomerular cells in the kidneys secrete renin into the blood. Angiotensin II constricts blood vessels throughout the body (raising blood pressure by increasing resistance to blood flow).

A negative feedback loop helps regulate blood pressure. An increase in blood pressure is detected by receptors in the blood vessels that sense the resistance of blood flow against the vessel walls. The receptors relay a message to the brain, which in turn sends a message to the effectors, the heart and blood vessels.

ROLE OF BLOOD VOLUME IN THE LONG TERM REGULATION OF ARTERIAL PRESSURE

Increased blood volume increases arterial pressure, renal perfusion, and glomerular filtration rate. This leads to an increase in renal excretion of water and sodium that is termed pressure natriuresis.

RAPID BLOOD LOSS

Generally, a blood loss of <15% of total blood volume leads to only a small increase in heart rate and no significant change in arterial pressure. When blood loss is 15 to 40%, mean arterial and pulse pressures fall, and heart rate increases, with the magnitude of these changes being related to how much blood is lost.Hemorrhagic shock is a clinical syndrome resulting from decreased blood volume (hypovolemia) caused by blood loss, which leads to reduced cardiac output and organ perfusion