CARDIOVASCULAR SYSTEM Physiology Topic #3

THE HEART

LEARNING GOALS I will be able to identify the structure and function of the heart. I will be able to explain how the heart contracts. I will be able to find my target heart rate.

the heart is a muscle (MYOCARDIUM) characteristics: involuntary contractions capable of speeding up fatigue resistant (approx. 3 billion contractions/lifetime) CARDIOVASCULAR ANATOMY

the heart is considered a “ double pump ” and is divided into R and L sides R heart - pumps deoxygenated blood from the veins to the lungs (for PULMONARY CIRCULATION) L heart - pumps oxygenated blood from the lungs to the body (for SYSTEMIC CIRCULATION) each side consists of 2 chambers HEART ANATOMY

CHAMBERS OF THE HEART

receive the blood from the body (right atrium) and lungs (left atrium) before pumping it into ventricles act as ‘ reservoirs ’ for blood while ventricles are pumping THE ATRIA

these larger pumps receive blood from atria and pump it to the lungs (RIGHT VENTRICLE) or to the body (LEFT VENTRICLE) NOTE: the right pumps de-oxygenated blood, the left pumps oxygenated blood THE VENTRICLES

ADDITIONAL STRUCTURES

STRUCTUREFUNCTION tricuspid valve bicuspid (mitral) valve pulmonary artery (1/lung) pulmonary veins (2/lung) vena cava (inf. & sup.) aorta (& descending aorta) pulmonary semilunar valve aortic semilunar valve

STRUCTUREFUNCTION tricuspid valveseparates R atrium from the R ventricle bicuspid (mitral) valveseparates L atrium from the L ventricle pulmonary artery (1/lung)carries blood from the R ventricle to the lungs pulmonary veins (2/lung)return blood from the lungs to the L atrium vena cava (inf. & sup.) return blood to the heart from the upper body (superior) & from the lower body (inferior) aorta (& descending aorta) carries blood from the heart out to the upper body (aorta) & to lower body (descending aorta) pulmonary semilunar valve prevents blood from flowing back from the pulmonary artery into the R ventricle again aortic semilunar valve prevents blood from flowing back from the aorta into the L ventricle again

FOR YOUR VIEWING PLEASURE internal structure mechanics anatomy

muscular extensions of the ventricle walls, PAPILLARY MUSCLES, attach to the valves via CHORDAE TENDINAE & prevent them from opening up into the atria Ensures unidirectional flow of blood in heart MECHANICS OF THE ATRIO-VENTRICULAR VALVES

ELECTRICAL CONDUCTION

heart can speed up according to the oxygen demands of the muscles the speed at which the heart contracts is governed by a collection of nerve cells in the R atrium called the SINUS NODE the SINUS NODE stimulates contraction independent of the brain The heart’s pacemaker Chew on this! ELECTRICAL CONDUCTION OF THE HEART

1. SINUS (SA) NODE gives signal to contract 2. signal is passed from the R atrium to the L atrium by the INTERNODAL PATHWAY 3. signal moves to the bottom of the atria and is passed to the INTERVENTRICULAR SEPTUM by the ATRIOVENTRICULAR (AV) NODE 4. nervous tissue in the septum called the BUNDLE OF HIS, splits into R and L branches 5. the R and L BUNDLE BRANCHES pass the signal on to the PURKINJE FIBRES at the bottom of each ventricle ELECTRICAL CONDUCTIONCONDUCTION

During one CARDIAC CYCLE, there are 2 “main events ”: 1. DIASTOLE - phase of relaxation when heart is filling with blood (therefore, low pressure in blood vessels) 2. SYSTOLE - phase of contraction where heart ejects blood (therefore, high pressure in blood vessels) BLOOD PRESSURE

MEASURING HEART RATE

to get a true measure of RHR, you need to take it FIRST thing in the morning from an athletic perspective, a low RHR is a good thing b/c then you should be able to work a little harder before reaching your maximum heart rate (MHR) TRY IT...count for 10 s RHR = _____ beats X 6 = _____ bpm WHAT ’ S YOUR RESTING HEART RATE?

WHAT ’ S YOUR MAX HEART RATE? to find out the max # of times your heart should be able to beat in 1 minute... MHR = your age = _____ bpm MHR = your age = _____ bpm

to get any cardiovascular benefit from exercise, you need to work your heart enough, but not too much (or you ’ ll tire out too quickly) the general rule of thumb is that you should work out at 50-85% of your MHR (depending on your existing level of fitness) WHAT ’ S YOUR TARGET HEART RATE?

LEARNING GOALS I will be able to identify the structure and function of the heart. I will be able to explain how the heart contracts. I will be able to find my target heart rate.

REVIEW QUESTIONS

1. Describe the role of each of the 4 valves in the heart. 2. All of the valves have the same basic function...what is it? 3. Which valves are responsible for the ‘ sounds ’ of the heart? 4. Why is the L ventricle larger than the R? 5. What is the function of the interventricular septum? 6. What part of the ventricle receives the message to contract first? Why? CARDIO REVIEW Q ’ S

7. Describe what happens to the (a) heart (b) blood pressure during DIASTOLE. 8. Describe what happens to the (a) heart (b) blood pressure during SYSTOLE. 9. If you want to gain an aerobic benefit from exercise, why shouldn ’ t you exercise (a) above 85% (b) below 50%