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Question 1

The Cardiac Cycle

Answer 1

The period from the beginning of one heartbeat to the beginning of the next

During the cardiac cycle, pressure changes occur as the atria and ventricles
alternately contract and relax
* When a chamber of the heart contracts, there is an increase in blood pressure
inside the chamber
* When a chamber of the heart relaxes, there is a decrease in blood pressure inside the chamber
* Blood always flows from regions of high pressure to low pressure

Question 2

Blood always flows from regions of ____ pressure to ____ pressure

Answer 2

high to low

Question 3

Mechanical events of the cardiac cycle are associated with changes in
pressure and blood volume in the heart
* The pressure differences cause opening and closing of heart valves that allow
one-way blood flow through heart
* Changes in pressure and blood volume correspond with electrical events on
the EKG

Answer 3

The Cardiac Cycle

Question 4

The Cardiac Cycle
* Pump Cycle
* Phases of the pumping action of the heart

Answer 4

• Periods of valve opening and closure
• Changes in pressure within the atria and ventricles
• Changes in ventricular volume
• Reflect the amount of blood entering and leaving the ventricle during each heartbeat
• Heart sounds

Question 5

One complete cardiac cycle includes both contraction and relaxation of the
atria and ventricles
* Systole
_______ of a heart chamber forcing blood out
* Diastole
_______ of a heart chamber allowing blood filling

Answer 5

contraction relaxation

Question 6

Phase 1: Mid-to-late Diastole

Answer 6

• Two components
  Ventricular Filling
  Atrial Contraction
• Ventricular filling
• Ventricles are relaxed
• Intraventricular pressure is low
• AV valves are open
• Semilunar valves are closed
• Most ventricular filling is passive
• Passive blood flow from the atria into the ventricles accounts for about most of ventricular filling
• Atrial contraction
• Occurs following SA node depolarization
• Relatively little contribution to ventricular filling in normal, resting heart
• Atria contract and compress blood in the atria
• Slight rise in atrial pressure
• Deliver remaining blood to the ventricles
• Atria relax and are in atrial diastole for the rest of the cardiac cycle
• This causes a pressure gradient reversal across the AV valves which causes them to close

Question 7

2 components of phase 1:
Mid-to-late Diastole?

Answer 7

Ventricular Filling
Atrial Contraction

Question 8

Ventricles are relaxed
* Intraventricular pressure is low
* AV valves are open
* Semilunar valves are closed
* Most ventricular filling is passive
* Passive blood flow from the atria into the ventricles accounts for about most of ventricular filling

Answer 8

Phase 1: Mid-to-late Diastole
* Ventricular filling

Question 9

Phase 1: Mid-to-late Diastole
* Atrial contraction

Answer 9

Atrial contraction
* Occurs following SA node depolarization
* Relatively little contribution to ventricular filling in normal, resting heart
* Atria contract and compress blood in the atria
* Slight rise in atrial pressure
* Deliver remaining blood to the ventricles
* Atria relax and are in atrial diastole for the rest of the cardiac cycle
* This causes a pressure gradient reversal across the AV valves which causes them to close

Question 10

Phase 2: Systole

Answer 10

• Isovolumetric Contraction
• Ventricular contraction
• Increased ventricular pressure
• All four heart valves are momentarily closed
• When ventricular pressure exceeds atrial pressure, the AV valves close
• The semilunar valves remain closed until the ventricular pressure
  exceeds the pressure in the pulmonary trunk or aorta
• Once the ventricular pressure exceeds the pressure in the pulmonary trunk and aorta, the semilunar valves open
• Blood is ejected from the ventricles

Question 11

Phase 3: Systole

Answer 11

• Ventricular Ejection
• Begins when the semilunar valves open
• Blood is pumped out of the ventricles and into the pulmonary trunk and aorta
• Ventricular volume decreases

Question 12

Phase 4: Early Diastole

Answer 12

• Isovolumetric relaxation
• Period between closure of the semilunar valves and opening of AV valves
• Precipitous fall in ventricular pressure without a change in volume
• Atria:
• Filling with blood
• Increased atrial pressure
• Rapid ventricular filling
• Atrial blood pressure begins to exceed the pressure in the ventricles
• The AV valves open
• Blood flows from the atria into the ventricles

Question 13

Quiescent period

Answer 13

• Follows ventricular systole
• The entire heart is relaxed for ~ 0.4 sec

Question 14

Heart Sounds

Answer 14

• Triggered by valve closure and blood passing through the heart
• “Lub-Dub” sound is produced by vibrations and turbulence created by blood flow inside the heart
• First sound is “lub”
• Longer and louder
• Reflects AV valve closure
• Indicates the beginning of ventricular systole
• Second sound is “dub”
• Shorter and sharp
• Reflects semilunar valve closure
• Indicates the beginning of ventricular diastole

Question 15

• Heart rate (HR)
  The number of ventricular contractions per minute
• Stroke volume (SV)
  The amount of blood pumped out of the ventricle with each contraction
  ~ 70 ml/beat at rest

Answer 15

Cardiac Output

Question 16

• The number of ventricular contractions per minute

Answer 16

Heart rate (HR)

Question 17

• The amount of blood pumped out of the ventricle with each contraction
• ~ 70 ml/beat at rest

Answer 17

Stroke volume (SV)

Question 18

CO = SV x HR

Answer 18

The volume of blood pumped by each ventricular contraction per minute

Example (normal resting adult):
* SV = 70 ml/beat and HR = 72 bpm
* CO = 70 ml/beat x 72 bpm = 5,040 ml/min or about 5 L/min

Question 19

At rest CO is

Answer 19

~ 5 L/min

Question 20

During stress such as exercise, the normal heart has the capacity to
increase CO by 4 - 5 times that of resting which would be …..

Answer 20

At rest CO is ~ 5 L/min
* During stress such as exercise, the normal heart has the capacity to
increase CO by 4 - 5 times that of resting
* ~ 20 – 25 L/min

• Athletes can increase CO by as much as 7 times that of resting
• ~ 35 L/min,

Question 21

Cardiac Output
* May be altered by changes in SV and/or HR
* Direct relationship

Answer 21

• Heart Rate
  ↑ HR = ↑ CO; ↓ HR = ↓ CO
• Stroke Volume
  ↑ SV = ↑ CO; ↓ SV = ↓ CO

Question 22

Extrinsic control: factors from outside of the heart
* Neural input
* Circulating hormones (neurotransmitters, but can include drugs)
Intrinsic control: factors from within the heart
* Starling’s Law of the Heart

Answer 22

Factors that affect heart rate and contractility

Question 23

• Autonomic Control of HR

Answer 23

• Heart rate is influenced by 3 types of factors:
  Sympathetic control
  Parasympathetic control
  Hormonal control
• Fibers of the ANS project to almost every part of the heart
  SA node
  AV node
  Ventricular myocardium
• The ANS regulates both HR and SV (contractility)

Question 24

Sympathetic nervous system activation causes

Answer 24

• ↑ HR
• ↑ SV (contractility)
  Sympathetic cardiac nerves emerge from the sympathetic trunk from thoracic region of spinal cord
  Provides innervations to the:
• SA node
• AV node
• Ventricular myocardium
  Neurotransmitter is norepinephrine

Question 25

Sympathetic Control of HR

Answer 25

* Increased sympathetic activity * Increases action potential frequency * Action potential is transmitted faster * Reduced delay of impulse conduction between the atria and ventricles * Shortens the time it takes for action potentials to travel through the ventricles * ↑ HR * ↑ CO

Question 26

Parasympathetic nervous system activation causes

Answer 26

* ↓ HR The vagus nerve (X) emerges from the medulla oblongata Primarily innervates the * SA node * AV node Neurotransmitter is acetylcholine

Question 27

Parasympathetic Control of HR

Answer 27

* Increased parasympathetic activity * Vagus nerve stimulation Decreases depolarization Decreases action potential frequency Action potential is transmitted slower * Decreased conduction between atria and ventricles * Lengthens the time it takes action potentials to travel through the ventricles * ↓ HR * ↓ CO

Question 28

Hormonal Control of HR

Answer 28

Epinephrine (Catecholemines) * Secreted by the adrenal medulla, usually in response to sympathetic nervous stimulation * Travels through the bloodstream to the heart * Increases the frequency of action potentials generated by the SA node * ↑ HR * Increases speed of action potential conduction through heart * ↑ HR Thyroid hormones (Thyroxine) Causes proliferation of adrenergic receptors, the binding sites for catecholamines, resulting in: * ↑ HR * ↑ SV * ↑ CO * Decreased total peripheral resistance (when present in very large amounts) * Inadequate thyroid function can produce decreased HR, SV, and CO

Question 29

* Age * HR is fastest in fetus (140 - 160 bpm) * HR gradually decreases through childhood and most of adult life * The elderly commonly develop tachycardia * Gender * HR is faster in women (72 - 80 bpm) compared to men (64 - 72 bpm) * Physical fitness * Highly-fit individuals have lower resting HR due to increased vagal tone and decreased sympathetic tone * Body temperature * Increased body temperature (hyperthermia) , as in fever or strenuous exercise increases HR * Decreased body temperature (hypothermia) decreases HR * Both conditions are associated with changes in metabolic rate of the myocardium

Answer 29

Other Factors that Influence HR

Question 30

Other Factors that Influence HR * Age

Answer 30

* HR is fastest in fetus (140 - 160 bpm) * HR gradually decreases through childhood and most of adult life * The elderly commonly develop tachycardia

Question 31

gender and HR

Answer 31

* HR is faster in women (72 - 80 bpm) compared to men (64 - 72 bpm)

Question 32

physical fitness and HR

Answer 32

Highly-fit individuals have lower resting HR due to increased vagal tone and decreased sympathetic tone

Question 33

body temperature and HR

Answer 33

* Increased body temperature (hyperthermia) , as in fever or strenuous exercise increases HR * Decreased body temperature (hypothermia) decreases HR * Both conditions are associated with changes in metabolic rate of the myocardium

Question 34

Increased body temperature (_______) , as in fever or strenuous exercise increases HR

Answer 34

hyperthermia

Question 35

Decreased body temperature (_______) decreases HR

Answer 35

hypothermia

Question 36

Both conditions, hyperthermia and hypothermia, are associated with changes in _____ _____ of the myocardium

Answer 36

metabolic rate

Question 37

Ventricular Contractility

Answer 37

The capacity of the ventricles to produce force

Question 38

Preload

Answer 38

Also called End Diastolic Volume (EDV) The amount of blood in the heart at the end of ventricular filling

Question 39

Afterload

Answer 39

* Also called End Systolic Volume (ESV) * The pressure the ventricles must overcome to eject blood out of the left ventricle

Question 40

Any factor that causes an ↑ in contractility =

Answer 40

= ↑ SV (↑ CO)

Question 41

Any factor that causes a ↓ in contractility =

Answer 41

↓ SV (↓CO)

Question 42

Control of ventricular contractility

Answer 42

* Sympathetic nervous system * Hormonal

Question 43

Contractility refers to force of contraction at any given ______

Answer 43

preload The more blood in the ventricles at beginning of systole... * The greater the force of contraction * The more blood ejected by the ventricles

Question 44

Contractility refers to force of contraction at any given preload * The more blood in the ventricles at beginning of systole... * The greater the force of contraction * The more blood ejected by the ventricles Results: * ↑ SV and ↑ CO * ↓ ________ (ESV)

Answer 44

afterload

Question 45

Starling’s Law of the Heart

Answer 45

Heart adjusts output to match venous return * Starling’s Law is based on the observed changes that occur in EDV and preload as a result of venous return

Question 46

EDV

Answer 46

end diastolic volume

Question 47

Starling’s Law is based on the observed changes that occur in EDV (end diastolic volume) and preload as a result of _______ return

Answer 47

venous

Question 48

End diastolic volume (EDV) * Determined by _____ return * Influenced by central _______ pressure * ↑ EDV = ↑ force of contraction (contractility) * ↑ EDV = ↑ SV * ↑ EDV = ↑ CO

Answer 48

venous

Question 49

Preload * The amount of tension, or stretch, on the ventricular myocardium * The cardiac muscle fibers are stretched due to the blood filling the chambers * The effect of stretching ventricular walls = ↑ force of ventricular contraction * This is an example of ______ control of the heart

Answer 49

intrinsic

Question 50

Starling Curves

Answer 50

Within normal limits, any factor that increases venous return will result in: * ↑ preload (EDV) * ↑ force of contraction * ↑ SV

Question 51

Afterload * The pressure the left ventricle must exceed before the aortic valve opens * Indicates how hard the cardiac muscle must work to push blood into the arterial system * Must push blood against the mean (average) arterial pressure * ↑ mean arterial pressure = ↑ afterload (ESV) * Must push blood against the total peripheral resistance * ↑ total peripheral resistance = ↑ afterload (ESV) * An Increased afterload (ESV) results in: * ↓ SV * ↓ CO

Answer 51

An Increased afterload (ESV) results in: * ↓ SV * ↓ CO

Question 52

Tachycardia

Answer 52

* HR > 100 bpm * Causes: * Fever * SNS stimulation * Exercise * Certain hormones * Certain drugs

Question 53

Bradycardia

Answer 53

* HR < 60 bpm * Common in endurance-trained individuals Causes: * Hypothermia * PNS stimulation * Certain drugs

Question 54

Systemic Blood Pressure Expressed in terms of _____ of mercury (mm Hg)

Answer 54

Expressed in terms of millimeters of mercury (mm Hg)

Question 55

Systolic blood pressure (SBP)

Answer 55

* The maximum blood pressure generated during ventricular contraction (systole)

Question 56

Diastolic blood pressure (DBP)

Answer 56

The lowest blood pressure that remains in the arteries during ventricular relaxation (diastole)