chapter 11 – part 5 the cardiovascular system. vital signs the following measurements are...

Chapter 11 – Part 5The Cardiovascular System

Vital SignsVital Signs

The following measurements are referred to collectively as vital signs in clinical settings: • Arterial pulse• Blood pressure• Respiratory rate• Body temperature

Vital signs are a fairly good indication of the efficiency of a person’s circulatory system

PulsePulse

Pulse – Pressure wave of blood Is created from the

alternating expansion and recoil of an artery that occurs with each beat of the left ventricle

Pressure PointsPressure Points Monitored at pressure

points where pulse is easily palpated Can feel a pulse where an

artery lies close to the body surface

Are called pressure points because these same points are compressed to stop blood flow during hemorrhage

PulsePulse

Normally pulse rate (pressure surges per minute) equals heart rate (beats per minute).

Pulse averages 70-76 beats per minute in a normal resting person.

Pulse is influenced by activity, postural changes, and emotions.

How to Take a PulseHow to Take a Pulse

Place the tips of your first two or three fingers over one of the arteries designated as a pressure point.

Compress the artery firmly as you begin and then immediately ease up on your pressure slightly.

Blood PressureBlood Pressure

Blood Pressure – The pressure the blood exerts against the inner walls of the blood vessels It is the force that keeps blood circulating

continuously even between heartbeats

Any system equipped with a pump that forces fluid through a network of closed tubes operates under pressure.

Understood to mean the pressure within the large systemic arteries near the heart

Blood Pressure GradientBlood Pressure Gradient

Blood flows along a pressure gradient (from high to low) as it makes its circuit. Pressure is highest in the large arteries and

continues to drop throughout the pathway, reaching zero or negative pressure at the venae cavae

The high pressure in these arteries forces the blood to continually move into areas where the pressure is lower.

Comparison of Blood Pressures in Different Comparison of Blood Pressures in Different VesselsVessels

Blood Pressure GradientBlood Pressure Gradient

The pressure differences between arteries and veins are apparent when the vessels are cut: If a vein is cut - the blood flows evenly

from the wound If an artery is cut - rapid spurts of blood

Blood Pressure GradientBlood Pressure Gradient

The continual flow of blood absolutely depends on the stretchiness (elasticity) of the large arteries and their ability to recoil and keep the pressure on the blood. Garden hose example with hard walls:

When the water hose is turned on, the water spurts out under high pressure because the hose walls don’t expand.

When the faucet is suddenly turned off, the flow of water stops because the walls cannot recoil to keep pressure on the water. The pressure drops and the flow of water stops.

Measuring Blood PressureMeasuring Blood Pressure

Two arterial blood pressure measurements are usually made:1. Systolic Pressure – Pressure in

the arteries at the peak of ventricular contraction

2. Diastolic Pressure – Pressure in the arteries when the ventricles are relaxing

• Blood pressures are reported in millimeters of mercury (mm Hg)

Measuring Blood PressureMeasuring Blood Pressure

A blood pressure of 120/80 indicates a: Systolic pressure of 120

mm Hg Diastolic pressure of 80

mm Hg

Measuring Arterial Blood PressureMeasuring Arterial Blood Pressure

Blood Pressure: Effects of FactorsBlood Pressure: Effects of Factors

Arterial blood pressure is directly related to the two following factors. An increase in the following factors causes an increase in blood pressure.

1. Cardiac output (the amount of blood pumped out of the left ventricle per minute)

2. Peripheral resistance

Blood Pressure: Peripheral ResistanceBlood Pressure: Peripheral Resistance

Peripheral Resistance – The amount of friction encountered by the blood as it flows through the blood vessels It is increased by the

constriction, or narrowing, of the blood vessels.

Increased blood volume or thickness (viscosity) increases peripheral resistance.

Blood Pressure: Effects of FactorsBlood Pressure: Effects of Factors

Many factors can alter blood pressure. Some of the factors include: Age Weight Time of day Exercise Body position Emotional state Various drugs

Blood Pressure: Effects of FactorsBlood Pressure: Effects of Factors

1. Neural Factors: Autonomic Nervous System Sympathetic nerves cause vasoconstriction, which

increases blood pressure back to homeostatic levels This hopefully increases venous return so circulation can

continue. During exercise:

There is a general vasoconstriction except in the skeletal muscles.

The vessels of the skeletal muscles dilate to increase the blood flow to the working muscles.

Blood Pressure: Effects of FactorsBlood Pressure: Effects of Factors

2. Renal factors Regulates blood pressure by altering blood volume

As blood volume decreases, blood pressure decreases.

As blood volume increases, blood pressure increases.

Blood Pressure: Effects of FactorsBlood Pressure: Effects of Factors

3. Temperature Heat has a vasodilation effect

Warm compresses are used to speed the circulation into an inflammed area

Cold has a vasoconstricting effect Why cold compresses are

recommended to prevent swelling of a bruised area

Blood Pressure: Effects of FactorsBlood Pressure: Effects of Factors

4. Chemicals Various substances can cause increases or decreases

Nicotine increases blood pressure by causing vasoconstriction

Alcohol causes vasodilation and decreases the blood pressure; often become flushed after drinking alcohol

5. Diet• A diet low in salt, saturated fats, and

cholesterol helps to prevent high blood pressure

Factors Determining Blood PressureFactors Determining Blood Pressure