The Cardiovascular System

1
The Cardiovascular System

• Cardiovascular Control During Exercise
• Chapter 11 and 12

2
Heart Structure and Blood Flow

• The atria receive blood into the heart the
  ventricles eject blood from the heart.

Atria
Ventricles
3
The Myocardium

• Because the left ventricle must produce more
  power than other chambers, its myocardium is
  thicker due to hypertrophy.

4
Cardiac Conduction

• Cardiac tissue is capable of autoconduction.
• It initiates its own pulse without neural control.

5
Cardiac Conduction

• The sinoatrial (SA) node is the hearts
  pacemaker, establishing the pulse and
  coordinating activity throughout the heart.

6
Extrinsic Control of Heart Activity

• Heart rate and contraction strength can be
  altered by the autonomic nervous system or the
  endocrine system.

7
Electrocardiography (ECG)

• The ECG is a recording of the hearts electrical
  functioning.
• An exercise ECG may reveal underlying cardiac
  disorders.

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8
Cardiac Function

• The cardiac cycle
• Relaxation diastole.
• Contraction systole.
• ECG waves P, QRS, T.
• Stroke volume.

9
Cardiac Function

• Ejection fraction from left ventricle (60 at
  rest).
• Cardiac output (4.8-6.4 L. min-1)

10
Vascular System

• Arteries.
• Arterioles.
• Capillaries.
• Venules.
• Veins.

11
Venous Return

• Blood returns to the heart through the veins,
  assisted by
• Breathing.
• Muscle pump.
• Valves.
• Valsalva Manuever

12
Distribution of Blood

• Activity dictates distribution.
• Vasoconstriction.
• Vasodilation.

13
Blood Pressure (NHLBI, 2003)
Pressure Normal Pre-hypertension Stage I Hypertension Stage II Hypertension
Systolic lt 120 120-139 140-159 gt 160
Diastolic lt 80 80-89 90-99 gt 100
Treatment
Otherwise healthy None None Diuretics for most, possibly other drugs Two-drug combo usually one is a diuretic
With other diseases None Medically treat diseases Multiple medications Multiple medications
14
Blood

• Blood and lymph are the substances that transport
  materials to and from body tissues.
• Fluid from plasma enters tissues, becoming
  interstitial fluid.

15
Blood

• Most interstitial fluid returns to the
  capillaries, but some enters the lymphatic system
  as lymph, eventually returning to the blood.

16
Blood

• Blood is about 55 to 60 plasma and 40-45
  formed elements including RBCs, WBCs, etc.
• Hematocrit ration of blood cells to total blood
  volume.

17
Blood

• Oxygen is primarily transported bound to the
  hemoglobin in red blood cells.
• As blood viscosity increases, so does resistance
  to flow.

18
Total Peripheral Resistance

• TPR length x viscosity
• ______________
• (Radius)4

19
Response to Exercise

• As exercise intensity increases, HR increases.

20
Exercise

• The heart ejects blood more often, thus speeding
  up circulation.

21
Response to Exercise

• Stroke volume also increases, so the amount of
  blood ejected with each contraction increases.
• Increases in HR and SV increase cardiac output.

22
Response to Exercise

• More blood is forced out of the heart during
  exercise then when at rest, and circulation
  speeds up.

23
Response to Exercise

• This insures that adequate supplies of the
  needed materials - oxygen and nutrients - reach
  the tissues and that waste products, which build
  up much more rapidly during exercise, are quickly
  cleared away.

24
Major Changes in Blood During Exercise

• The a-vO2 difference increases.
• Increased extraction of oxygen from the blood
  for use by the active muscles.

25
Major Changes in Blood During Exercise

• Plasma volume decreases during exercise.
• Water is forced into tissues by increased blood
  pressure.
• Water also evaporates.

26
Major Changes in Blood During Exercise

• Hemoconcentration occurs as plasma fluid (water)
  is lost.
• Although the actual number of red blood cells
  might not increase, the relative number of red
  blood cells per unit of blood increases, which
  increases O2 carrying capacity.

27
Major Changes in Blood During Exercise

• pH levels drops from resting values of 7.4 to
  7.0 or lower.
• Muscle pH decreases even further.
• The decrease in pH results primarily from
  increased blood lactate accumulation with
  increasing exercise intensity.