The Heart

What do gap junctions do in the heart?

allow simultaneous contraction of cardiac muscle

What causes the QRS complex?

ventricle depolarization

What is the function of the subendochondral conducting network? On what side of the heart is this network more elaborate?

-complete pathway through inter ventricular septum into apex and ventricular walls -more elaborate on the left side of the heart *Ventricular contraction immediately follows from apex towards atria

Does the heart need the nervous system to depolarize and contract?

NO. Heart depolarizes and contracts without nervous system stimulation due to auto rhythmic cells!

What is the function of the semilunar valves (pulmonary and aortic)?

Prevent back flow into the ventricles when the ventricles relax.

The heart is a _____-shaped, muscular structure located in the _______.

cone-shaped; thorax

What is pericarditis?

inflammation of the pericardium - excess fluid and can compress the heart

What layers make up the bulk of the heart?

myocardium

What are some major differences between cardiac muscle and skeletal muscle (in regards to nerve stimulation, contraction, etc.)

-About 1% of cells have autorhythmicity = do not need nervous system stimulation. can depolarize the entire heart -all cardiomyocytes contract as one unit, or none do -slower action potential and longer refractory period

Why does the atrioventricular node (AV node) delay impulses approximately 0.1 second?

-because fibers are smaller diameter, and have fewer gap junctions -allows atrial contraction to occur prior to ventricular contraction (can't have both at the same time)

Artery = moves blood ____ the heart. Vein = moves blood ______ the heart

Artery = Away from heart Vein = towards the heart

What is the main functional difference between atria and ventricle chambers?

Atria collect blood from the body/lungs Ventricles pump blood throughout the body Ventricles >>>> atria Left ventricle >>>> right ventricle

What is the cardiac cycle? How long does it last?

Cardiac cycle = all of the mechanical events associated with blood flow through the heart during ONE COMPLETE HEARTBEAT

Coordinated heartbeat is a function of the I____ C_____ C_____ system. Which is a network of ______ cells.

Coordinated heartbeat is a function of the INTRINSIC CARDIAC CONDUCTION SYSTEM = -network of NONCONTRACTILE (AUTORHYTHMIC) CELLS: -initiate and distribute impulses (Action potentials) -have unstable resting potentials called pacemaker potentials) -presence of gap junctions allow simultaneous contraction of cardiac muscle

The heart muscle behaves as a functional interconnected unit that can contract in UNISON. Why is this?

Due to intercalated discs in cardiomyocytes (cardiac muscle cells) -anchor cardiac cells together and allow FREE PASSAGE OF IONS

What is the main function of atrioventricular valves?

Ensure unidirectional blood flow through the heart. AV Valves - prevent back flow into the atria when ventricles contract

T or F: The ability of the heart to beat is controlled by the autonomic nervous system.

FALSE - it is controlled by the auto rhythmic cells! -if you take out a human heart, it still beats for a short time outside of the body

T or F: Arteries always carry oxygenated blood and veins always carry deoxygenated blood.

FALSE!! Neither always carry these types of bloods. i.e., pulmonary artery carries deoxygenated blood Pulmonary veins carry oxygenated blood

What does the SA node do?

Generates an action potential (stimulus) and impulse spreads across the right atria (causing the atria to contract) and to AV node.

Describe the third phase of the cardiac cycle.

Isovolumetric relaxation occurs in early diastole. -ventricles relax -backflow of blood in aorta and pulmonary trunk closes semilunar valves (because blood flows from high to low pressure!)

Describe the process of how AV valves open and close.

OPENING: 1. Blood returning to the heart fills the atria, putting pressure against atrioventricular valves; the AV valves are forced open. 2. As ventricles fill, AV valve flaps hang limply into ventricles. 3. Atria contract, forcing additional blood into ventricles. *AV valves open = atrial pressure > ventricular pressure CLOSURE: 1. Ventricles contract, forcing blood against atrioventricular valve cusps. 2. AV valves close. 3. Papillary muscles contract and chordae tendineae tighten, preventing valve flaps from everting into aorta. *AV valves closed = atrial pressure < ventricular pressure

What are the functions of the inner and outer layers of the pericardium?

Outer layer - very fibrous, anchors the heart, prevents overfilling Inner layers - contain fluid to provide lubrication

ANS can ____ heart rate.

Parasympathetic - lower HR sympathetic - increases HR

What is the difference between the pulmonary circuit (right side) and systemic circuit (left side) in regards to pressure?

Pulmonary circuit = short, low-pressure circulation Systemic circuit = blood encounters much resistance in the long pathways *As a result, the left ventricle has a much thicker wall (stronger muscle)

What do the chord tendinae do?

anchor AV valve cusps to papillary muscles

What causes the P wave?

atrial depolarization

What is the outer membrane surrounding the heart called?

epicardium

The membrane around the heart is known as the _______.

pericardium

Where are the pulmonary and aortic valves located?

pulmonary valve - between R ventricle and pulmonary trunk aortic valve - between L ventricle and aorta

Heart rate

refers to the frequency of cardiac cycle (measured in bpm) -physical conditioning lowers heart rate as a result of cardiac hypertrophy -essentially, working out the muscle a lot allows the muscle to grow!

An increase in the resistance to blood flow to the lungs would cause hypertrophy (because of greater work) of which of the following chambers? a. right atrium b. left atrium c. right ventricle d. left ventricle

remember, the right side of the heart is associated with pumping blood to the lungs c. right ventricle

If the heart releases blood in bouts, why is blood pressure constant?

the aorta (and other major arteries) are ELASTIC, so they absorb the bouts of ventricular ejection and 'smooth it out'

What is the only electrical connection between the atria and ventricles?

the atrioventricular (AV) bundle -atria and ventricles are not connected via gap junctions

What is the apex of the heart?

the end of the cone. it is caudoventrally pointed

Where are the tricuspid and mitral valves located?

tricuspid valve (R): between R atrium and R ventricle mitral valve (L): between L atrium and L ventricle

What causes the T wave?

ventricle repolarization

What is a heart murmur? What is it usually caused by?

murmur - irregular heart sound - usually due to valve problems

Describe the flow of blood through the heart.

1. Deoxygenated blood enters the vena cava. 2. goes into the right atrium 3. through tricuspid/right AV valve 4. to the right ventricle 5. through the pulmonary/right semilunar valve 6. through the pulmonary artery 7. to the lungs 8. back to the heart through the pulmonary veins (oxygenated now) 9. to the left atrium 10. through the bicuspid/left AV valve 11. to the left ventricle 12. through the left/aortic semilunar valve 13. through the aorta 14. to the body (carrying oxygen)

Write out the entire process of the conduction system of the heart in relation to an EKG.

1. P wave: atrial depolarization, initiated by the SA node 2. In between P and Q = With atrial depolarization complete, the impulse is delayed at the AV node. 3. QRS complex: Ventricular depolarization begins at apex. Atrial repolarization occurs. 3. In between S and T: Ventricular depolarization is complete. 4. T wave: Ventricular depolarization begins at apex. 5. Part after T wave: Ventricular depolarization is complete.

What are the three waves of the EKG?

1. P wave: depolarization of SA node 2. QRS complex: ventricular depolarization 3. T wave: ventricular repolarization

What are the steps in the conduction pathway of the heart?

1. SA node (pacemaker) generates action potentials (impulses) 2. Impulses pause (0.1 s) at the AV node. 3. AV bundle (bundle of his) connects the atria to the ventricles 4. The right and left bundle branches conduct the impulses through the inter ventricular septum. 5. The subendocardial conducting network (Purkinje fibers) depolarizes the contractile cells of both ventricles.

What are the 3 main functions of the cardiovascular system?

1. Transport: nutrients, gases (O2 and CO2) and waste around the body 2. Protection: against infection and blood loss 3. Maintain homeostasis: internal temperature, pH, fluid levels

Describe the first phase of the cardiac cycle and when it takes place. + are AV valves open/closed?

1. Ventricular filling - takes place in mid-to-late diastole (for both atria and ventricles) -AV valves are open -80% OF BLOOD PASSIVELY FLOWS INTO VENTRICLES -atrial systole (contraction) occurs, delivering the remaining 20%

Generally smaller animals have higher heart rates. Why?

1. consequence of metabolic rate and oxygen consumption 2. larger surface area to body mass ratio in smaller animals young animals have a higher heart rate - higher metabolic rate -tonic vagal inhibition is less developed in young animals *recall = vagus is associated with rest and digest (parasympathetic) = slows heart rate down humans = 60 bpm whale = 6 bpm rapid = 200 bpm canary = 17 bps

What are the three layers of the heart?

1. epicardium - outer, visceral layer of the pericardium 2. myocardium - majority of heart *** 3. endocardium - smooth lining continuous with the endothelial lining of large vessels attached to the heart

What is the main process of the conduction system by cardiac pacemaker cells (autorhythmic cells)?

1. sinoatrial node 2. atrioventricular node 3. Atrioventricular bundle (bundle of His) 4. Right and left bundle branches 5. Subendocardial conducting network (Purkinje fibers)

What is the pathway of blood through the heart? (Hint: 11 steps excluding valves)

1. vena cava (sup. & inf. ) 2. right atrium --> tricuspid valve 3. right ventricle --> pulmonic valve 4. pulmonic artery (deoxygenated) 5. lungs 6. pulmonary veins (oxygenated) 8. left atrium --> mitral valve 9. left ventricle --> aortic valve 10. aorta 11. systemic circulation

What are the 3 phases of the cardiac cycle (just the names)?

1. ventricular filling 2. ventricular systole (contraction) 3. isovolumetric relaxation (occurs in early diastole)

Describe the second phase of the cardiac cycle.

2. Ventricular systole (contraction) -rising ventricular pressure results in closing of AV valves (because blood starts to flow back to low pressure) -isovolumetric contraction phase (all valves are closed) -in ejection phase (end of contraction), ventricular pressure exceeds pressure on large arteries, forcing the SL valves to open (because blood flows from high to low pressure)

What is the ANS's role in the heart's rhythm?

ANS cannot generate the rhythm, but can ALTER it

The heart is two side-by-side pumps. The right side is the pump for the ______ circuit.

Right side = pulmonary circuit -vessels that carry blood to and from the lungs -blood entering right side: low O2/high CO2 blood

The pacemaker of the heart is known as the:

SA node

The sinoatrial (SA) node is also called the _____ of the heart. It is located in the ________.

SA node = pacemaker of heart; located in right atrial wall

Describe the process of how semilunar valves open and close?

Semilunar valves open: As ventricles contract and intraventricular pressure rises, blood is pushed up against semilunar valves, forcing them to open. Semilunar valves closed: As ventricles relax, pressure falls, blood flows back from arteries, filling the cusps of semilunar valves and forcing them to close.

T or F: Both side of the heart pump blood at the same time.

True

Atria: the receiving chambers Vessels entering the right atrium: ______ and ________ Vessel leaving the right ventricle: ____/_____ ___________ Vessels entering left atrium: ___ and _____ ______________ Vessel leaving the left ventricle: ______

Vessels entering the right atrium: superior vena cava and inferior vena cava Vessel leaving the right ventricle: right/left pulmonary artery Vessels entering the left atrium: right and left pulmonary veins Vessel leaving the left ventricle: aorta

What is an electrocardiogram (ECG or EKG)?

a composite of all of the action potentials generates by nodal and contractile cells at a given time

During end (ejection) stage of ventricular systole: a. the AV valves are closed, and the semilunar valves are open b. the SL valves are closed, and the AV valves are open c. all valves (AV + semilunar) are open d. all valves (AV + semilunar) are closed

a. AV valves closed; SL valves open At this point, the ventricle has high pressure and is starting to flow into the aorta. So what valve has to be open? The SL valves.

Remember - blood will always flow from ____ pressure to ____ pressure. This is what is responsible for valves closing/opening.

blood will always flow from HIGH PRESSURE TO LOW PRESSURE

What do the right and left bundle branches do?

carry impulses towards the apex of the heart

What are the three main components of the cardiovascular system?

heart, blood vessels, blood

Blood leaving the systemic circuit has high _____ and low ____.

high O2/low CO2

Where is the heart located (specific)?

in the medial region of the thoracic cavity (mediastinum) -sternal to vertebral column -between the lungs

Why does the left ventricle look bigger?

it is the area for systemic circulation, where blood encounters much resistance as it has to be pushed to all areas of the body long-distance; essentially, the left ventricle has thicker wall of muscle

Blood entering the right side (pulmonary circuit) of the heart has low ____ and high ____.

low O2/high CO2

What valves close to make the lub sound? What valves close to make the dub sound?

lub-dub - lub - AV valves closing (tricuspid and mitral) dub - semilunar valves closing (pulmonic, aortic)

What is making the heart sounds, aka "lub"-"dub"?

sound made from valves closing

The left side of the heart is the pump for the ______ circuit.

systemic circuit -vessels that carry blood to and from all of the body tissues blood leaving left side: high O2/low CO2

What are the two mechanical events in the cardiac cycle?

systole - contraction diastole - relaxation *both atria and ventricles have diastole/systole, but ventricle is more important