Exercise Physiology: Cardiovascular physiology

What are the functions of the cardiovascular system?

• deliver O2 and substrates

• remove CO2 and other waste products

• transport hormones

• regulate temperature and fluid balance

• maintain acid-base balance

• regulate immune function

What are the components of the cardiovascular system?

1. heart - pump

2. blood vessels - system of channels or tubes

3. fluid - blood

What is the primary goal of the cardiovascular system?

• the primary goal of the cardiovascular system is to ensure adequate blood flow to meet metabolic demands

What circulatory route are the right and left sides of the heart?

• Right (pulmonary)

• Left (systemic)

What is the route of blood flow through the heart?

1. right atrium

2. Right ventricle

3. lungs

4. left atrium

5. left ventricle

6. body

Does the right side of the heart (pulmonary circulation) pump oxygenate or de-oxygenated blood? Where does it pump blood to?

• pumps de-oxygenated blood from body to lungs

What is the flow of blood in pulmonary circulation (right heart)?

1. superior and inferior vena cava

2. right atrium

3. tricuspid valve

4. right ventricle

5. pulmonary valve

6. pulmonary arteries

7. lungs

Is the pulmonary circulation (right heart) a low- or high-pressure system compared to systemic (left heart)?

• low pressure system

Does systemic circulation (left heart) receive oxygenated or de-oxygenated blood? Where does it pump the blood to?

• receives oxygenated blood and pumps to the systemic circulation

what is the flow of blood in systemic circulation (left heart)?

1. lungs

2. pulmonary veins

3. left atrium

4. mitral (bicuspid) valve

5. left ventricle

6. aortic valve

7. aorta

Is the left heart (systemic) a high- or low-pressure system compared to pulmonary (right heart)

• high pressure

What is myocardium?

• cardiac muscle

What does thickness of the myocardium depend on?

• dependent on force generation

Which ventricle is the thickest? Why is it the thickest?

• left ventricle has greatest thickness

• must overcome the force of gravity (pooling of blood in legs)

• particularly thick in athletes or individuals with disease

How many fibers types does cardiac muscle?

• one fiber type

• Type one has a high capillary and mitochondrial density

• striated in appearance

How does the heart contract?

• calcium-induced calcium release

How does Ca2+-induced Ca2+ release work?

1. action potential on sarcolemma and through t-tubules inside the cell

2. Ca2+ from out the cell goes into t-tubule, enters the cell, and binds to the sarcoplasmic reticulum

3. results in Ca2+ release from the sarcoplasmic reticulum

What are the parts of a cardiac action potential?

1. pacemaker potential

2. depolarization

3. repolarization

What happens during pacemaker potential?

• slow depolarization due both opening Na+ channels and closing K+

• membrane potential never a flat line

What happens during depolarization?

• the action potential begins when the pacemaker potential reaches threshold

• depolarization due to Ca2+ influx though Ca2+ channels

What happens during repolarization?

• due to Ca2+ channels inactivating and K+ channels opening

• allows K+ efflux, which brings the membrane potential back to most negative value

What is entering the cell during depolarization?

• Na+

• Ca2+

what element leaves during repolarization?

• K+

Describe what’s happening at each part of the action potential

1. rapid depolarization due to opening of voltage-gated fast Na+ channels

2. Plateau (maintained depolarization) due to opening of voltage gated slow Ca2+ channels and closing of some K+ channels

3. repolarization due to opening of voltage gated K+ channels and closing Ca2+ channels

Which nervous system input is active below or above 100 bpm?

• Below 100 BPM - parasympathetic

• above 100 BPM - sympathetic

What arteries provide nutrient delivery and waste removal for the heart?

• coronary arteries

• left anterior descending artery called the widow maker (when heart not getting enough blood)

what is teh intrinsic heart rate?

• 100 BPM

What specialized cells in the heart initiate electrical signals?

• Sinoatrial (SA) node

• Atrioventricular (AV) node

• AV bundle (bundle of his)

• Purkinje fibers

What has extrinsic control of heart activity?

• parasympathetic nervous system

• sympathetic nervous system

• endocrine system

How does the parasympathetic nervous system control the heart?

• release acetylcholine

• Vagus nerve hyperpolarizes cell (decrease heart rate and force of contraction)

What is normal resting heart rate?

• 60-100 bpm (depending on vagal control)

• 35 bpm for elite endurance athletes

How does the sympathetic nervous system control the heart?

• facilitates depolarization of heart cells

• increase heart rate and force of contraction

• determine heart rate during stress

• max of 250 bpm

• release norepinephrine

How do you determine heart rate max?

• 220 - age = Heart rate max

Which system has a greater oxygen demand?

• sympathetic

Does the sympathetic system kick in immediately?

• no

• parasympathetic input must decrease fist

How does the endocrine system control the heart?

• catecholamines (epinephrine and norepinephrine)

• increases heart rate and force of contraction

What are the parts of an electrocardiogram (ECG)?

• P wave - atrial depolarization

• QRS complex - ventricular depolarization. Atrial repolarization underneath QRS complex

• ST segment - ventricular repolarization

• T wave - ventricular repolarization

• PR interval - AV delay

• QT interval - ventricular depolarization/repolarization

Label the parts of the ECG

1. P wave

2. QRS complex

3. ST segment

4. T wave

5. PR interval

6. QT interval

What does this show?

• Sinus Bradycardia

• <60 bpm

What does this show?

• Sinus Tachycardia

• >100bpm

What does this show?

• Premature ventricular contractions (PVC)

What does this show?

• Atrial fibrillation

What does this show?

Ventricular tachycardia

What does this show?

• ventricular fibrillation

What is diastole and systole?

• Diastole: relaxation phase (heart chambers filling)

• Systole: contraction phase (ventricles emptying)

What is stroke volume?

• volume of blood in mL pumper per beat

How do you calculate stroke volume?

• EDV-ESV

• Normal stroke volume: 110mL-40mL=70mL

What is most adaptable with endurance training?

• stoke volume

What is ejection fraction?

• fraction of blood pumped out of the left ventricle

• EF=SV/EDV

• 70mL/110mL=64%

What is cardiac output (Q)?

• total volume of blood pumped per minute (L/min)

• Q=HR x SV

• 70 bpm x 70mL= 4900 mL/min (4.9L/min)

What makes up the vascular system?

• arteries

• arterioles

• capillaries

• venules

• veins

What are arteries and arterioles?

• Arteries

  • carry blood away from heart

  • large, muscular, elastic

  • Aorta is largest artery

• Arterioles

  • have greatest control of blood flow within the system

  • resistance vessels

  • controlled by the sympathetic nervous system

What are capillaries and venules?

• Capillaries

  • exchange zone vessels

  • narrowest and simplest vessels

  • site of exchange between circulation and tissues (gasses, nutrients, hormones, etc)

• Venules

  • collect blood from capillaries

What are veins?

• carry blood from venules back to heart

• vena cave (superior and inferior) are the largest veins

• largest storage site for blood

• 70% of blood in veins at rest

Where is most of blood volume at rest?

• most of the blood volume is housed in the venous side of circulation at rest

What is blood pressure?

• pressure exerted against the wall of the vessel

• typically it’s arterial blood pressure that is of interest

• pressure is a function of blood volume and vascular size/diameter

What is diastolic blood pressure?

• pressure in the artery during cardiac filling

• normally 80mmHg at rest

What is systolic blood pressure?

• pressure in the artery during ventricular ejection

• normally 120 mmHg at rest

What is mean arterial pressure (MAP)?

• average pressure exerted by the blood in the arteries

• MAP = (0.67 x DBP) + (0.33 x SBP)

What is normal mean arterial blood pressure (MAP) at rest?

• 93 mmHg

What is hemodynamics?

• blood flows from an area of high pressure to an area of low pressure

What three conditions can result in increased blood flow?

• exercise

• lack of oxygen

• sitting to standing

• anything not coming from rest

What tissues receive most blood?

• metabolically active tissue

What receives most blood at rest?

• GI tract

• skin

What receives most blood during exercise?

• skeletal muscle

What are the three types of intrinsic control of blood flow?

• metabolic regulation

• endothelium mediated vasodilation

• myogenic response

What happens during metabolic regulation?

• increased O2 demand is the primary and strongest stimulus

• other chemical changes: CO2, K+, H+, lactic acid

What happens during endothelium mediated vasodilation?

• substances produced in the inner lining of arteriole

What are the myogenic responses?

• pressure changes cause dilation/constriction

• increase pressure causes smooth muscle to constrict

• decrease pressure causes smooth muscle to dilate

What is extrinsic control of blood flow mediated by?

• sympathetic nervous system

  • system or organ level control

In tissue, does SNS stimulation causes smooth muscle contraction or vasoconstriction

• both contraction and vasodilation

What is vasomotor tone?

• presence of the SNS influence at rest in order to maintain adequate blood pressure

What does an increase and decrease of SNS activity cause?

• increase: vasoconstriction

• decrease: vasodilation

What are baroreceptors?

• sense changes in arterial pressure

• detect changes in blood pressure and adjust accordingly

What are chemoreceptors?

• blood and muscle receptors

• monitor chemical environment for O2, CO2, and pH

What are mechanoreceptors?

• ensure muscle is receiving adequate blood flow relative to mechanical activation

What is venous return?

• blood flow back to heat

What aids venous return in overcoming the force of gravity?

• Venous valves

  • allow blood flow in only one direction

• Muscle pump

  • skeletal muscle contraction pumps blood back toward heart

• Respiratory pump

  • inspiration raises abdominal pressure and lowers thoracic pressure

What is the function of blood?

• transport gases, substrates, metabolic byproducts

• regulate temperature

• acid-base balance

What is hematocrit (Hct)?

• blood cell volume/total blood volume

What percentage of blood is plasma and formed elements?

• 55% plasma

• 45% formed elements

How many times is thicker is blood than water?

• two times

Does viscosity increase as hematocrit increase?

• yes

What must increase as red blood cells increase?

• plasma volume