Exam 1: Heart Flashcards
1
Q
Heart Location
A
- Mediastinum: the cavity in the thorax which contains the heart
- extends from the 2nd rib to the 5th intercostal space
- rests on the superior surface of the diaphragm
- about 2/3 of the heart lies to the left of the midsternal line
- flat base on the posterior surface
- apex that points inferiorly toward the left hip
2
Q
Heart Covering
A
From superficial to deep:
- Fibrous Pericardium
- Serous Pericardium
3
Q
Fibrous Pericardium
A
- dense connective tissue
- protects the heart
- anchors the heart to surrounding structures
4
Q
Serous Pericardium
A
- thin
- two-layers
- — parietal layer: lines the inside of the fibrous pericardium
- — visceral layer: attached to the external heart surface and is called the epicardium
- — between the layers: pericardial cavity containing serous fluid lubricating the outside of the heart
- — loss of fluid creates painful pericarditis
- — cardiac tamponade: too much fluid which restricts the heart’s activity
5
Q
Layers of the Heart
A
From Superficial to Deep:
- Epicardium (visceral pericardium)
- Myocardium
- Endocardium
6
Q
Myocardium
A
- forms the bulk of the heart
- consists mostly of cardiac muscle
7
Q
Endocardium
A
- thin layer of squamous epithelium and connective tissue that lines the chambers of the heart
8
Q
Chambers of the Heart
A
- Right Atria and Left Atria
- — relatively small and thin-walled because their function is only to collect blood and pass it to the ventricles
- — atria are separated by the interatrial septum
- — right and left auricles protrude from the atria like ears
- — pectinate muscle: raised bundles line interior surface
- — fossa ovalis
- Right Ventricle
- Left Ventricle
- — ventricles are separated by the interventricular septum
9
Q
Fossa Ovalis
A
- shallow depression within the interatrial septum
- in fetal life, this was the foramen ovale
- – blood passed directly from right to left atrium
- — this opening closes shortly after birth
10
Q
Blood enters the right atrium from
1, 2, and 3
A
- superior vena cava - drains the upper part of the body
- inferior vena cava - drains the lower part of the body
- coronary sinus - drains the myocardium
11
Q
Blood enters the left atrium from….
A
- the pulmonary veins
- — two from the right, and two from the left
- — transport oxygen rich blood from the lungs back to the heart
- left atrium makes up most of the heart’s base
12
Q
Ventricles
A
- make up most of the heart volume
- trabeculae carnae: irregular ridges of muscles on the interior surface
- papillary muscles: cone-like muscles which connect to the valves
- thickened walls because of the amount of work required to pump the blood greater distances
- when the ventricles contract, blood is forced into circulation
13
Q
- Right ventricle sends blood through….
2. Left ventricle sends blood through….
A
- the pulmonary trunk
- divides into the right and left pulmonary arteries
- blood goes to lungs - aorta
- largest artery of the body
- blood goes out to body tissues
14
Q
Pulmonary Circuit
A
- the right side of the heart collects O2-poor and CO2-rich blood from the body and pumps it to the lungs where CO2 is unloaded and O2 is picked up
15
Q
Systemic Circuit
A
- the left side of the heart collects O2-rich and-CO2 poor blood and pumps it to the arteries where it is transported to the body tissues
- in the body, O2 is dropped off and CO2 is picked up
16
Q
How the heart tissue gets nutrients
A
- the heart picks up almost no O2 or nutrients from the chambers of the heart, but has its own coronary circulation
- the right and left coronary arteries arise from the base of the aorta and encircle the heart in the atrioventricular groove
- — left –> anterior interventricular artery (LAD) and circumflex artery
- — right –> marginal artery and posterior interventricular artery
- considerable variation among people in the arterial blood supply of the heart
- many anastomoses among the arterial branches
- — a grid of arteries which allows for detours to be taken if an artery is blocked
17
Q
Cardiac Veins
A
- collect blood after it passes through the capillary beds of the myocardium
- Three large veins
- — great cardiac, middle cardiac, small cardiac
- — drain into the coronary sinus which empties into the right atrium
- several anterior cardiac veins also empty into the right atrium
18
Q
Myocardial Infarction
A
- heart attack
- — lack of blood flow to one area of the heart
- can be caused by an arterial blockage in the coronary circulation
- cell death due to oxygen deprivation results in tissue replacement with scar tissue
19
Q
Heart Valves
A
- two atrioventricular valves
- — tricuspid and mitral
- two semilunar valves
- — aortic and pulmonary
20
Q
Atrioventricular Valves
A
- regulate flow of blood between the atrium and the ventricle on the same side
- — tricuspid on the right
- — mitral/bicuspid on the left
- valve flaps are connected to papillary muscles by collagen cords called chordae tendinae
- when the ventricle contracts, the valve closes preventing backflow into the atrium
- — papillary muscles also contract preventing the flaps from going into the atrium
21
Q
Semilunar Valves
A
- prevent backflow of blood back into the ventricle
- — Aortic Valve: between the left ventricle and the aorta
- – Pulmonary Valve: between the right ventricle and pulmonary trunk
- when the ventricle contracts, the semilunar valve is forced open
- when the ventricle is relaxed, backpressure of the aorta/pulmonary trunk forces the semilunar valve closed
22
Q
Cardiac Muscle
A
- striated and contracts by sliding filaments
- — like skeletal muscle
- has only one or two centrally located nuclei
- a greater portion of the the cell is made up of mitochondria
- — heart relies almost exclusively on aerobic respiration
- — cardiac muscle cannot incur much oxygen debt
- intercalated discs
- gap junctions
23
Q
Intercalated discs
A
- found in the junctions of cardiac muscle cells
- contain anchoring desmosomes
- — prevent separation of cells during contraction
24
Q
Gap Junctions
A
- found in the junctions of cardiac muscle cells
- allow ions to pass from cell to cell
- — this electrical coupling allows the entire myocardium to act as a coordinated unit
25
Intrinsic Caidiac Conduction System
- autorhythmic cells: non-contractile cardiac cells
- able to to initiate action potentials that spread throughout the heart
- note: the heart is well supplied with nerves which can alter the rhythm
26
Sequence of Excitation
1. Sinoatrial node
2. Atrioventricular node
3. Bundle of His
4. Purkinje Fibers
5. Ventricular Muscle Cells
27
Sinoatrial Node
- located on the right atrial wall just inferior to the entrance of the superior vena cava
- heart's pacemaker: determining the sinus rhythm
- --- contain autorhythmic cells
- start the sequence of excitation
28
Atrioventricular Node
- recieve impulse after the sinoatrial node
- --- step 2 of excitation
- ---a wave of depolarization spreads via gap junctions throughout the atrium to the AV node
- located on the inferior interatrial septum
- impulse is delayed, allowing the complete contraction of the atrium
29
Bundle of His
- receive impulse after the atrioventricular node
- --- step 3 of excitation
- located in the superior part of the interventricular septum
- this is the only electrical connection between the atria and the ventricles
- splits into right and left bundle branches that the impulse continues along
30
Purkinje fibers
- receives the impulse from the branches of the Bundle of His
- --- step 4 of excitation
- reach down to the apex and then into the ventricular walls
- ---- walls: cell to cell transmission via gap junctions occurs between ventricular muscle cells
31
Arrhythmias
- irregular atrial or ventricular contractions
32
Fibrillation
- condition of rapid and irregular or out-of-phase contractions in which contractions are no longer controlled by the sinoatrial node
- an electrical shock to the heart may allow the sinoatrial node to regain control of rhythms
- --- defibrillation
- --- depolarizes the entire myocardium
33
EKGs
- an electrocardiograph records electrical currents generated in the heart and spread through the heart and the body
- three distinguishable waves
- --- small P wave
- --- QRS complex
- --- T wave
- the size, duration, and timing of the deflection waves tend to be consistent in a healthy heart so that changes in patterns may reveal disease or past damage
34
P wave
- small
| - depolarization wave from the sinoatrial node through the atria
35
QRS complex
- results from ventricular depolarization and precedes ventricular contraction
- obscures a graphical recording on the EKG of atrial repolarization
- --- bc atrial repolarization occurs at the same time as ventricular depolarization
36
T wave
- caused by ventricular repolarization
37
Normal Heart Sounds
- lub-dup sound is associated with closing of heart valves
- lub: when AV valves close
- --- ventricles contract
- dup: when SL valves close
- --- ventricles relax
38
Murmur
- abnormal heart sounds
- one fairly common murmur occurs when the mitral valve fails to completely close
- --- swishing sound as the the blood backflows into the left atrium
39
Cardiac Cycle
1. Ventricular Filling
2. Ventricular Systole
3. Isovolumetric Relaxation
- Quiescent Period
- --- total heart relaxation
- --- about half of the cardiac cycle
40
Systole
contraction of chambers
41
Diastole
relaxation of chambers
42
Ventricular Filling
- step 1 of the cardiac cycle
- mid to late diastole
1. blood flows passively from the atria to the ventricles
- --- SL valves are closed
2. then, the atrial systole occurs
- --- P wave
- --- forces the remaining atrial blood into the ventricles
3. atrial diastole occurs as the ventricles depolarize
- --- QRS complex
43
Ventricular Systole
- step 2 of the cardiac cycle
1. ventricles contract
- --- AV valves are closed
- --- SL valves are forced open
- --- blood is forced into the aorta and pulmonary trunk
- --- pressure in the aorta generally reaches 120mmHg
- atria are filling as the ventricles contract
44
Isovolumetric Relaxation
- step 3 of the cardiac cycle
- early diastole
1. following ventricular repolarization, the ventricles relax
2. pressure in the aorta and pulmonary trunk causes a backflow resulting in the closure of the SL valves
3. atria started filling while the ventricles contracted
- --- when the blood pressure in the atria exceeds that in the ventricles ( the ventricles are relaxed and got rid of their blood), the AV valves are forced open
45
Cardiac Output
- amount of blood pumped by each ventricle in one minute
- calculated by multiplying the heart rate (number of beats per minute) times the stroke volume (the volume of blood pumped out by one ventricle with each beat
- varies considerably in response to the oxygen demands of the body
46
Extrinsic Factors which regulate heart rate
| in addition to the intrinsic conduction system
- autonomic nervous system
- hormones
- --- epinephrine and thyroxine
- --- increase heart rate
- imbalance in ion concentrations
- age, body temp, gender, exercise
47
Autonomic Nervous System Regulates Heart Rate
- parasympathetic: decrease heart rate
- sympathetic: increase heart rate
- --- release norepinephrine
- --- enhance Ca2+ entry into contractile cells
- under resting conditions, both division of the ANS send impulses to the SA node
- --- this usually inhibits the heart rate
48
Imbalance in Ion concentrations affect heart rate
- the relationship between intracellular and extracellular ions must be maintained in a certain balance
- hypocalcemia decreases heart rate
- hypercalcemia may result in too many contractions
- Too much Na+ and K+ may interfere with the transport of Ca2+ into the cardiac muscle cells
- the mode of action of many cardiac drugs involves the transport of calcium into cardiac cells
49
Disorders:
1. Tachycardia
2. Bradycardia
1. abnormally elevated heart rate
- --- usually > 100 bpm
2. abnormally depressed heart rate
- --- usually
50
Congestive Heart Failure
- cardiac output is not enough to meet tissue needs
- damage to the myocardium may be done by coronary atherosclerosis, chronic hypertension, and multiple myocardial infarcts
51
If the left side of heart fails...
- pulmonary congestion
- the right side continues to pump to the lungs -->
but the blood can't properly enter and exit the left side on the way back from the lungs -->
so everything is backed up as it waits (congestion) -->
lung tissue may become engorged -->
forcing circulation fluid into the lung tissue -->
causing a pulmonary edema
- diuretics are often given to treat edema
52
If the right side of the heart fails...
- results in edema in the extremities
- blood cannot properly enter and exit the right side as it comes back from the body --> everything comes backed up as it waits (congestion) --> fluid is absorbed into the body tissue because it has to go somewhere --> edema of the extremities
- diuretics are often given to treat edema
