Regulation of Blood Flow Chapter 10 Section 10.3

Cardiac Output Cardiac output – the amount of blood pumped from the heart each minute. Two factors affect cardiac output: 1.Stroke Volume 2.Heart Rate

Stroke Volume and Heart Rate Stroke volume – the quantity of blood pumped with each beat of the heart. Heart rate – is the number of times the heart beats per minute. Cardiac output = stroke volume x heart rate

Example of Cardiac Output Cardiac output = 70 mL/beat x 70 beats/min Cardiac output = 4900 mL/min

Blood Pressure Blood Pressure - The pressure that is exerted against the vessel walls when blood passes through them. It can be measured with an instrument called a sphygmomanometer. AKA - a blood pressure cuff

Blood Pressure Cuff Measures blood pressure – usually in arm Recorded in millimeters of mercury (1mmHg = 0.133kPa) Systolic pressureex)120 Diastolic pressure 80

Systolic Pressure The max pressure during ventricular contraction –Pressure increases when the ventricles contract and force blood into the pulmonary arteries and aorta

Diastolic Pressure The lowest pressure between ventricular contraction –Pressure decreases when the ventricles relax

Applying What You Already Know As HR increases (ie. exercise) ventricles push more blood out at one time, so the pressure also increases –Affects systolic pressure

Hypertension Hypertension or high blood pressure is cause by increased resistance to blood flow. Increased resistance to blood flow causes an increase in blood pressure. Resistance can be caused by the build-up of fat in the arteries.

Regulation of Blood Pressure Blood pressure receptors are located in the walls of the aorta and the carotid arteries (on either side of the neck). When high bp is sensed, a nerve impulse is sent to the brain. Sympathetic (stress) nerve impulses are decreased and parasympathetic (relaxed) nerve impulses are increased. This causes the arteries to dilate and decreases blood pressure. **The opposite occurs when low bp is sensed**

Regulation of Body Temperature Thermoregulation – the maintenance of body temperature within the ideal range. To generate heat our bodies increase cellular respiration. To cool our body down our bodies do one of two things: 1.Sweat 2.Dilate blood vessels near the skin

Regulation of Body Temperature - Cooling The evaporation of sweat off of skin cools the skin. The dilation of blood vessels allows more blood to the skin. Because skin has been cooled and is now cooler than the blood, the blood loses heat to the skin. The cooler blood then flows back through the body and cools off the interior organs.

The circulatory system cannot supply warmth, but it can reduce heat loss. Blood vessels constrict and flow to the skin is reduced. Blood flow to the essential organs is increased. This reduces heat loss from the skin. Regulation of Body Temperature - Warming