Chapter 30

Question 1

Hemodynamics

Answer 1

Refers to the numerous mechanisms that influence the dynamics of the circulation of blood
Essential for health and survival
Circulation control mechanisms must:

Maintain circulation
Vary the volume and distribution of blood circulated

Question 2

Primary principle of circulation

Answer 2

Blood moves, or flows, due to a pressure gradient along its pathway, according to the following principles:

A fluid doesn’t flow when the pressure is the same throughout the system
A fluid flows only when its pressure is higher in one area than in another, and it flows from its higher pressure area to its lower pressure area

Blood flow between any two points in the circulatory system can always be predicted by the pressure gradient

Question 3

Arterial blood pressure (BP)

Answer 3

BP is the push or force of blood in the blood vessels
Must be highest in arteries, lowest in veins to allow for proper circulation of blood
Arterial BP is directly proportional to arterial blood volume

Question 4

Main factors determine arterial BP (2)

Answer 4

Cardias output

Peripheral resistance

Question 5

Cardiac output

Answer 5

The amount of blood that flows out of a ventricle of the heat per unit time

Question 6

Resting CO2 from the left ventricle

Answer 6

5000ml/min

Question 7

Co2 influenses

Answer 7

The flow rate to various organs of the body

Question 8

Cardio output is determined by

Answer 8

The volume of blood pumped out of a ventricle by each beat= stroke volume (SV) and by heart rate (HR)

Question 9

The great the SV the greater the

Answer 9

CO

Question 10

CO=

Answer 10

SV x HR

Question 11

Anything that changes either HR or SV will to to impact

Answer 11

CO

Question 12

Factors affecting Stroke volume (SV)

Answer 12

Strength of myocardial contractions

• Recall length-tension relationship re: muscle fibre contraction. The more ‘stretched out’ heart muscle fibres are at the beginning of a contraction, the stronger the contraction will be (relative to the amount of blood in the heart – provided it is not ‘hyperextended’) = Starling’s Law of the Heart
• Neurotransmitters
• Hormones

Question 13

Autonomic nervous system innervation

Answer 13

Sympathetic vs parasympathetic

Question 14

Cardiac pressoreflexes

Answer 14

control centers that receive information from stretch receptors in the aorta and carotid sinuses. If high BP is detected, a motor message will be sent to the SA-node to decrease HR

Question 15

Other factors the that influence heart rate and what they as a group are called

Answer 15

Emotions – e.g. anxiety, fear, anger vs grief
Exercise
Hormones
Blood temperature – increased blood temp tends to increase HR
Pain – can result in decreasing the heart  fainting
Stress response/Sympathetic NS

All called: Peripheral resistance

Question 16

Peripheral resistance is

Answer 16

Any force that acts against the flow of blood

Question 17

Blood viscosity

Answer 17

comes mainly from the proportion of RBCs and partly from blood protein concentration (e.g. polycythemia, anemia, hemmorhage)

Question 18

Tension in the muscles of the blood vessel walls

Answer 18

Vasomotor mechanism

Question 19

Vascomotor center located in the medulla can

Answer 19

Stimulate constriction of blood vessels

Question 20

Vasomotor pressorelexes

Answer 20

the stretch receptors in the aorta and carotid sinuses response to increased BP and messages are sent to inhibit the vasomotor center; and vice-versa

Question 21

Vasomotor chemoreflexes

Answer 21

same location as stretch receptors; are sensitive to excess carbon dioxide in the blood, as well as low oxygen and decreased arterial pH  vasoconstriction

Question 22

Varying normal range of blood pressure can be affected by

Answer 22

Strenuous exercise, stress  increased BP
Fitness level
Age, gender, race, weight
Stress, emotions
Hormones (e.g. renin, angiotensin II, aldosterone, ANH, ADH)
Diseases (e.g. diabetes, CVD)
Tobacco, alcohol, caffeine and other drugs

Feedback mechanisms work to go back to homostasis

Question 23

Hypertension

Answer 23

Higher than normal blood pressure reading

If BP is too high, it can cause the rupture of blood vessels

Silent killer- no symptoms

Question 24

Hypotension

Answer 24

Lower than normal blood pressure

If BP is too low, blood may stop flowing

Question 25

Blood pressure being measured with a

Answer 25

Sphygmomanometer

Question 26

Central venous pressure

Answer 26

Definition: The venous blood pressure within the right atrium (close to zero!)
Influences the pressure that exists in the large peripheral veins
Strong heart beat  blood is entering and exiting the heart effectively  low central venous pressure
Weak heart beat is weak flow of blood into the right atrium will be slowed  increased/high central venous pressure

Question 27

Mechanisms that help keep venous blood moving through circulatory system

Answer 27

Continued beating of the heart
Adequate BP in the arteries to push blood to and through the veins
Semilunar valves in veins that ensure blood flow in one direction (towards the heart)
Contraction of skeletal muscles – produces a ‘pumping’ action which squeezes veins
Changing pressures in the chest cavity during breathing also produces a kind of ‘pumping’ action in the veins in the thorax

Question 28

Pulse

Answer 28

Alternate expansion and recoiling of an arterial vessel wall

Possible due to pressure changes within arteries and the elasticity of arterial walls
Provides info re: the cardiovascular system, blood vessels, and circulation (e.g. rate, strength and rhythm of heart beat
Nine major pulse points