1. NOTES: UNIT 6- The Circulatory System part 4 Blood Pressure

2. Remember: Blood vessels form
a closed circuit of
tubes that carry
blood from the
heart to body cells
and back again.
*composed of arteries, arterioles, capillaries, venules, & veins

3. -largest artery = AORTA
VEINS
-carry blood to the
heart
-thinner walls
-are less muscular
than arteries
ARTERIES
-carry blood away
from heart
-largest artery = AORTA
ARTERIOLES
VENULES
CAPILLARIES
-walls are only
1 cell thick

5. BLOOD PRESSURE: Blood pressure is the force blood exerts
against the inner walls of blood vessels.
*force occurs throughout system but “blood pressure” commonly refers to pressure in arteries supplied by branches of the aorta

6. BLOOD PRESSURE:
Arterial blood pressure rises & falls in relation to the cardiac cycle
Contracting ventricles squeeze blood out into the aorta and pulmonary arteries which increases arterial pressure
Ventricular contraction causes the elastic arterial walls to distend
Relaxed ventricles lead to a drop in blood pressure & a recoiling of arterial walls
Felt as a pulse

7. BLOOD PRESSURE:
● SYSTOLIC PRESSURE: pressure produced in the arteries when the ventricles contract; highest pressure
● DIASTOLIC PRESSURE: pressure in the arteries when the ventricles are relaxed

8. BLOOD PRESSURE: Arterial blood pressure depends upon:
> cardiac output (volume of blood pumped from each ventricle in 1 min.) CO= HR x SV (heart rate x stroke volume; L/min)
> blood volume (increase vol. = inc. press.)
> peripheral resistance (friction between the blood & vessel walls; contracting artery walls slows blood & inc. press.)
> blood viscosity (thickness)

9. REGULATION OF BLOOD PRESSURE:
Baroreceptors in the walls of the aorta & carotid arteries sense changes in blood pressure
Changes in pressure causes baroreceptors to send nerve impulses to medulla oblongata
Medulla oblongata sends nerve impulses to S-A node to increase or decrease heart rate

10. VENOUS BLOOD PRESSURE: is much lower…how does blood flow through veins (in some cases, against gravity?)
 skeletal muscle contraction squeezes blood from one segment to the next
 breathing movements change pressure in thoracic and abdominal cavities pulling/pushing blood upward toward the heart
 VALVES prevent blood from flowing backward into a previous segment

11. Using a Sphygmomanometer
Blood Pressure
Using a Sphygmomanometer

12. Arterial Blood Pressure
Blood pressure is measured using an instrument called a sphygmomanometer
Measures the amount of air pressure equal to the blood pressure in an artery
Unit: mm Hg (millimeters of mercury)
original instruments measured how high air pressure could raise a column of mercury in a glass tube

13. What do those Number Mean Anyway?
The blood pressure cuff is wrapped around the upper arm and exerts pressure on the brachial artery
Systolic pressure: force with which blood is pushing against artery walls when the ventricles are contracting
Harder since the left ventricle is contracting
Diastolic pressure: force of the blood when the ventricles are relaxed
Just from the resistance of blood vessels

14. How To Take Blood Pressure
1. Bag is inflated to a pressure above the systolic pressure (do NOT go above 200mmHg!)
flow of blood is stopped and the artery is silent
2. Slowly release the valve letting air out of the bag
there are now 5 phases based on the loudness and quality of the sounds.

15. The Sounds of Korotkoff
The Five Phases
1. A loud, clear tapping (or snapping)
2. Succession of murmurs
3. A loud, thumping sound, similar to phase 1 but less clear.
4. A muffled sound
5. All sounds disappear. (this phase is absent in some people)

16. What You Should Listen For
1. When you hear the first sound Read the pressure gage.
= Systolic Pressure (needle jumps)
2. At the end of the muffled sounds or when there is no longer any sound (Needle smoothes out) Read the pressure gage = Diastolic pressure

17. Chart of Age-Appropriate Blood Pressure Ranges
Systolic
Diastolic
6-9
91-120
53-81
10-12
97-137
58-91
16-18
73-81
Adults
79-87

18. Fluctuations in blood pressure
the time of day Fluctuations occur during waking hours, and are lower during sleep.
physical activity Usually higher during and immediately after exercise, and lower at rest.
emotional moods Feelings (such as fear, anger, or happiness) can affect blood pressure.

19. stress Physical or emotional stress can elevate blood pressure.
age, height, weight, and gender Blood pressure varies for each person.
other illnesses Other illnesses a person may have (such as kidney or heart disease) affect blood pressure.