1. Cardiac Control During Exercise

2. Functions of the Cardiovascular System
The cardiovascular system serves a number of important functions, the major cardiovascular functions fall into five categories:
1. Delivery
2. Removal
3. Transport
4. Maintenance
5. Prevention

3. Functions of the Cardiovascular System
Delivers O2 and nutrients to every cell in the body
Removes CO2 and waste from every cell in the body
Transports hormones from glands to their target receptors
Maintains body temperature and pH levels
Prevents infection

4. Structure and Function of the Cardiovascular System
Any system of circulation requires three components:
1. Pump (Heart)
2. A system of channels (the blood vessels)
3. A fluid medium (the blood)

5. Structure and Function of the Cardiovascular System
Heart
Two Atria (receivers)
Two Ventricles (senders)
Path of Blood (Cell to Heart)
**Deoxygenated Blood **
Capillaries
Venules
Veins
Superior or Inferior Vena Cava

6. Structure and Function of the Cardiovascular System
Path of Blood (At the Heart)
** Deoxygenated Blood **
Right Atrium
Right Ventricle
Pulmonary Arteries
*Lungs--> Receives Oxygen
** Oxygenated Blood **
Pulmonary Veins
Left Atrium
Left Ventricle
Path of Blood (Heart to Cell)
** Oxygenated Blood **
Aorta
Arteries
Arterioles
Capillaries

7. The Cardiac Conduction System
The heart has the ability to generate its own electrical signal called autoconduction.
The heart contracts rhythmically without neural stimulation
The four of the components of the cardiac conduction system are:
1. Sinoatrial (SA) node
2. Atrioventricular (AV) node
3. Atrioventicular (AV) bundle
4. Purkinje fibers

8. The Cardiac Conduction System
The impulse for the heart to contract is initiated from the SA node (The Pace Maker)
The electrical impulse spreads to the AV node
As the electrical impulse spreads through the Atria they are signalled to contract
The AV node conducts the impulse fron the atria to the ventricles
The impulse then enters the AV bundle and then the Purkinje fibers

9. Extrinsic Control of the Heart Activity
Although the heart initiates its own electrical stimulus (intrinsic control), it can be altered
Three Extrinsic systems that can affect the heart are:
1. The parasympathetic nervous system
2. The sympathetic nervous system
3. The endocrine system (hormones)

10. Extrinsic Control of the Heart Activity
The Parasympathetic Nervous System
It slows down impulse conduction thus, decreases heart rate
The Sympathetic Nervous System
It stimulates the impulse thus, increasing heart rate
The Endocrine System
Norepinephrine and Epinephrine (Cateholamines)
Stimulate the heart, increasing its rate

11. Vascular System
Vessels that transport blood from the heart to the tissues and back:
Arteries
Arterioles
Capillaries
Venules
Veins

12. Vascular System Arteries & Arterioles Capillaries Veins
Carries blood AWAY from the heart
Carries oxygenated blood
The largest largest, most muscular & most elastic
Capillaries
Narrowest vessels , one cell thick
All exchange between blood and tissue occurs at the capillaries
Veins
Carries blood TOWARDS the heart
Carries deoxygenated blood
Contain valves to prevent back flow of blood

13. Vascular System Return of Blood to the Heart
Most of the time we are in an upright position, the cardiovascular system requires assistance to overcome the force of gravity when returning blood for the lower parts of the body.
The three basic mechanism are:
1. Breathing
2. The Muscle Pump
3. Valves

14. Vascular System 1. Breathing 2. The Muscle Pump 3. Valves
Each time you inhale or exhale, pressure changes in the abdominal and thoracic cavities assist blood return to the heart
2. The Muscle Pump
When skeletal muscle contract the vein in the immediate vicinity are compressed and blood is pushed upward towards the heart
3. Valves
Inside the veins
Allow the blood to flow in ONE direction, thus preventing back flow and pooling of blood

15. The Blood
The volume of blood in the body varies considerably with individual size and state of training
Larger the size and the highier the level of endurance training the highier the amount of blood
~ Without training 5-6 L in men and 4-5 L in women

16. Composition of Blood 55 - 60 % of the total blood volume is Plasma
90% of Plasma is H2O
% of total blood volume are Red Blood Cells (RBC), White Blood Cells (WBC) or Platelets

17. The Blood Red Blood Cells White Blood Cells Platelets
RBC transport oxygen primarily bound to their hemoglobin
Each RBC contains ~ 250 million hemoglobin, each able to bind to 4 O2 molecules, so each RBC can bind up to a billion molecules of O2
White Blood Cells
WBC protect the body from disease organism invasion
Adults have ~ 7, 000 WBC per cubic mm of blood
Platelets
Are not really cells, but rather cell fragments
Required for blood coagulation (clotting), which prevents excessive blood loss

18. Cardiovascular Response to Exercise
All changes to the cardiovascular system have a similar goal: To allow the system to meet the increased demands placed upon it by carrying out its functions with maximum efficiency
We will look at the changes of the following components of the cardiovascular system:
Heart Rate
Stroke Volume
Cardiac Output

19. Heart Rate
Heart rate reflects the amount of work the heart must do to meet the increased demands of the body when engaged in activity
Must compare at Rest vs. Exercise
Maximum Heart Rate - the highest heart rate value you achieve in ALL OUT effort to the point of exhaustion
HR max = Age

20. Heart Rate Resting Heart Rate Heart Rate during PA
Avg bpm
can be as high as +100bpm to as low as bpm
Your rest heart rate dereases with age but increases with temperature or altitude
Pre exercise heart rate are NOT good indicators of RHR
Heart Rate during PA
When you begin your HR increases rapidly in proportion with the intensity of the PA
When the rate of work is held constant at submaximal levels, HR reaches a plateau
This plateau is the steady state heart rate

21. Measuring your Heart Rate

22. Stroke Volume Stroke Volume is determined by:
Stroke Volume is the volume of blood pumped per contraction
Stroke Volume is determined by:
1. The volume of venous blood returned to the heart
2. The capacity to enlarge the ventricle
3. Ventricle contractility
4. Aortic or Pulmonary Artery pressure (the pressure which the ventricle must contract against)
The first two have to do with the filling capacity of the ventricles
The second two have to do with the ability to empty the ventricles

23. Stroke Volume SV = EDV - ESV
Stroke volume increases with increasing rates of work, but only up to exercise intensities between 40-60% of maximal capacity
End-Diastolic Volume (EDV) - the volume of the ventricle when filled
End-Systolic Volume (ESV) - the volume of the blood remaining in the ventricle
SV = EDV - ESV

24. Explanations of SV Increase
Frank-Starling Mechanism
A larger volume of blood enters the chamber when your ventricle fills up, thus the ventricle walls will stretch more. In order to eject the greater amount of blood, your ventricle must react to this increased stretching by contracting more strongly.
There is also an increase in the muscular strength of the ventricle through exercise, thus increasing the contractile strength of the ventricle

25. Cardiac Output
Cardiac Output is the total volume of blood pumped by the ventricle per minute or simply the product of heart rate (HR) and stroke volume (SV)
CO = HR x SV
Thus any changes in HR or SV will have an impact on the other component.

26. Cardiac Output
1. You rise from a reclining position to a sitting position, to standing.
2. You start to walk, than jog and finally run?
How does your heart respond?

27. Cardiac Output
1. If your HR in the reclining position is 50 bpm it will increase to about 55 bpm and to about 60 pbm.
When your body shifts from reclining to a standing position your SV drops immediately, due to gravity pulling the blood down and decreasing the amount of blood to the heart.
Thus, the increase in HR when changing to an upright position is to maintain the Cardiac Output because CO = SV x HR

28. Cardiac Output
#2 As you begin your activity, your HR increases from about 60 bpm to 90 bpm, with a jog it goes to 140 bpm and can reach 180 bpm with a run.
The increase in HR maintains your CO when changing positions
However, your SV and your HR both increase during activity thus, increasing your cardiac output

29. Cardiac Output
During exercise, cardiac output increases primarily tomatch the need for increased oxygen supply to the working muscles!!!