Regulation of Blood Flow Chapter 10 Section 10

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 m. L/beat x 70 beats/min Cardiac output = 4900 m. L/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 (1 mm. Hg = 0. 133 k. Pa) • Systolic pressure Diastolic pressure ex) 120 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.

Regulation of Body Temperature - Warming • 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.