The Heart Flashcards
What does the term “double pump” mean?
Each heartbeat pumps blood to the lungs and to the body
- Pulmonary circulation: send blood to lungs
- Systemic circulation: send blood to body
In what cavity is the heart located in the body?
In the Middle Mediastinum
What is the pericardium? What does it consist of?
Sac containing the heart
Consists of two layers:
- Outer Fibrous: anchor and protect heart
- Inner Serous
- Parietal layer: outermost layer
- Visceral layer (epicardium): surface of heart
What is the pericardial cavity?
The parietal and visceral layers of the Inner Serous pericardium have epithelial cells that produce pericardial fluid that fills the pericardial cavity
- This reduces friction
What does the heart wall consist of?
- Epicardium (visceral layer)
- Myocardium
- Endocardium
What are the characteristics of the heart muscle, Myocardium, which is part of the heart wall?
- Involuntary and striated muscle
- Intercalated discs
- Gap junctions to carry action potentials
- Ventricular muscle mass larger than atrial muscle mass
- Ventricular muscle mass pumps blood out of heart and needs to have a stronger contraction
- Cardiac skeleton
- collagen connective tissue separates atria and ventricle
- no action potentials between two sides except through two openings causing millisecond delay
What are the chambers of the heart?
Right and Left Aria
- Atria have appendages called auricles
- Larger space to expand and receive extra blood during exercise
Right and Left Ventricles
- Coronary Sulcus: “crown” indentation that separates Atria from Ventricle
- Intraventricular Sulci: Anterior and Posterior that separate the two ventricles
What is the septum of the heart?
A Septum is a wall. There is:
- Interatrial septum: separates atria
- Open as fetus for fetal gas exchange
- Closed as adult
- Interventricular septum – always closed
- Part membranous, part muscle.
- Muscle part contracts.
- Part membranous, part muscle.
Walk through Blood Flow through the heart
- Right Atrium
- receives deoxygenated bloods from:
- Superior vena cava
- Inferior vena cava
- Coronary Sinus
- receives deoxygenated bloods from:
- Right Ventricle
- Passes through Tricuspid Valve
- Pulmonary Trunk
- Passes through Pulmonary Semilunar-Valve
- Lungs
- Gas exchange
- Pulmonary Veins
- Left Atrium
- Left Ventricle
- Passes through the Bicuspid Valve
- Aorta
- Passes through the Aortic Semlunar-Valve
What are the Great Vessels?
- Aorta
- Superior/Inferior Vena Cava
What are the Atrioventricular Valves (AV) and how do they work?
- Tricuspid and bicuspid
* right vs. left side, respectively
Chordae tendineae attach to Papillary muscles which control the opening and closing of the valves
What are the semilunar valves?
The Pulmonary Semilunar Valve in trunk and Aortic Semilunar Valve
Arranged as 3 half-moon cusps (pockets)
What arteries are involved in Coronary Circulation in the heart?
Left Coronary Artery
- Anterior Interventricular Artery (widowmaker)
- Circumflex Artery
Right Coronary Artery
- Posterior Interventricular Artery
- Marginal Artery
Both arteries are fused (anastomoses)
What veins are involved in coronary circulation of the heart?
- Great cardiac vein
- Middle cardiac vein
- Small cardiac vein
The coronary sinus ultimately receives all cardiac venous blood and returns it to the right atrium
What makes up the conduction system of the heart?
Autorhythmic cells stimulates heart, generating hearbeat by starting action potentials
The ANS can modify heart rhythm but not establish the rhythm
All cardiac muscle cells are autorhythmic but 1% lose ability to contract
- These cells form the pacemakers and conduction system
What components make up the conduction system of the heart?
Sinoatrial (SA) Node
- Primary Pacemaker (fastest ap/min)
Atrioventricular (AV) Node
- Secondary Pacemaker (slower ap/min)
ORDER:
- SA Node
- AV Node
- AV Bundle
- Split into Left and Right Bundle Branches
- Purkinje Fibers loop around
- Where does the cardiac muscle contract first? Last?
- Why is there a 0.12 sec delay across the AV node?
- What separates the atrial muscle mass from the ventricular muscle mass?
- Why does the interventricular septum begin to contract before the apex?
- Atrial Cardiac muscle contract first and Upper Regions of the Ventricular Wall conduct last
- 0.12 sec delay due to the AV Node not firing as fast as SA
- Cardiac Skeleton separates the atrial and ventricular muscle masses
- Interventricular Septum contracts first b/c AP reaches there first
What are the different Waves and intervals in the EKG?
- P Wave: Atrial Depolarization
- QRS Complex: Ventricular Depolarization
- T Wave: Ventricular Repolarization
P-Q Interval: Atria depolarizes and contracts
P-R Interval: Atri and Ventricles Depolarize +contract
Q-T Interval:
S-T Segment: Blood Gone
Quiescent Period: Time between cycles
What does an EKG or ECG measure?
Measures electrical impulses sent down each chamber
What heart rate changes what actually changes in the conduction cycle?
The Quiescent period gets longer or shorter
What phenomena control blood flow through the heart?
Contraction and Relaxation of the
- Atrioventricular (AV) Valves
- Semilunar (SL) Valves
How does Pressure affect blood flow? What pressures are involved in the Cardiac Cycle?
Blood always flows from an area of high pressure to an area of low pressure
- Pressure is a result of the size of a chamber and the volume of blood within it
- Venous Pressure
- Atrial Pressure*
- Ventricular Pressure
- Aterial Pressure*
How do the chambers behave during a normal cardiac cycle?
Two Atria will contract while the Two Ventricles relax, then, Two Ventricles contract while the two Atria relax
- Systole: Contraction
- Diastole: Relaxation
What are the phases of the cardiac cycle?
- Ventricular Filling
- Isovolumetric Contraction
- Ventricular ejection
- Isovolumetric relaxation
What occurs during Ventricular Filling?
In diastole, ventricles expand and pressure decreases
- AV valves open when atrial pr. > ventricular pr.
3 Phases of Ventricular Filling:
- Rapid ventricular filling
- Diastisis
- Atrial systole
70% of Ventricle fills w/ Phases 1 & 2 due to pressure difference
30% of Ventricle fills w/ Phase 3 due to Atrial Contraction
END DIASTOLIC VOLUME = 130 mL
What is Isovolumetric Contraction?
Same Volume Contraction:
- Brief moment during contraction when Ventricle Pr>Atria Pr but Vent Pr<arterial></arterial>
- Atrial Diastole Begins
- Ventricular Systole Begins
- AV Valves close when Ventricular Pr>Atrial Pr
- No blood ejected because Arterial Pr>Ventricular Pr
What occurs during Ventricular Ejection?
Ventricular Pr>Arterial Pr
- SL Valves open when Ventricular Pr>Arterial Pr
- Rapid ejection then reduced ejection
Stroke Volume = 70 mL
End-Systolic Volume = 60 mL
What occurs during Isovolumetric Relaxation?
Brief period of time where the volume remains the same but the blood has been ejected so pressure goes down
- SL Valves are closed and AV Valves are still closed
Early Ventricular Diastole
- Ventricles expand = pr decreases
- SL Valves close when arterial pr>ventricular pr
Quiescent Period
- Begins whe atrial pr>ventricular pr
- AV valves will open and ventricular filling occurs to begin next cycle
What are the volume changes that occur during the cardiac cycle?
End-systolic volume=60 ml
- left from previous heart beat
Passively added during atrial diastole (70%)
- rapid ventricular filling + diastasis = 70 ml
Atrial systole (30%)
________________________________________________
Total end-diastolic volume = 130 ml
Stroke volume minus - 70 ml
(ejected by ventricular systole) ___________
Leaves the end-systolic volume = 60 ml
What are the chamber volume and pressure changes listed in the diagram below?
What is cardiac output?
amount of blood ejected from the left ventricle into the aorta per minute
What is cardiac ouput determined by?
Stroke volume (SV) and Heart Rate (HR)
SV x HR = Cardiac Ouput
Example: (70 ml/beat)(75 beats/minute) = 5,250 ml/min or 5.25L/min
In 1 min all of the blood within the body cycles through once
What is cardiac reserve?
difference between maximum cardiac output and resting cardiac output
- Resting cardiac output = 5 L/min
- Max (exercise) cardiac ouput = 20 L/min
- The max is 300% higher, so cardiac reserve = 300%
Exercise increases Cardiac Reserve
How do we compensate for congestive heart failure and pump more blood?
We tap into the cardiac reserve when ventricle not pumping all of the 70mL that it should
How is Stroke volume regulated?
- Preload
- Contractility
- Afterload
What is Preload?
More stretch in the sarcomere = more forceful contraction
- Increased venous return + Increased length of the Diastole = Increased ventricular filling = Increased Preload = Increased Ventricular stretch
- This results in a more forceful contraction = increased stroke volume = increased cardiac output
What is contractility?
External factors such as epinephrine increase the contractility of the muscle resulting in increased stroke volume = increased cardiac output
What is Afterload?
Pressure in the artery right after ventricle is higher then ventricular pressure and decreases cardiac output
- blood pools in ventricle => leading to hypertrophy of ventricle => leads to congestive heart failure
What will affect cardiac output?
Heartrate (HR) or Stroke Volume (SV)
What is the difference between Stroke Volume (SV) and Cardiac Output (CO)?
Stroke Volume (SV): amount of blood that moves out of heart w/ each Cardiac Cycle
Cardiac Output (CO): amount of blood that leaves the heart per minute
How does the automic nervous system regulate heart rate?
Sensory Input received from:
- Baroreceptors: Blood Pressure
- Chemoreceptors: Chemical concentration
Sensory Input sent to medulla oblongata. Motor output sent to:
- Cardioacceleratory neurons - via sympathetic NS
- release epinephrine at SA node
- increase heart rate
- Cardioinhibitory neurons - via parasympathetic NS
- release acetylcholine at SA node
- decrease heart rate
What kinds of chemicals can be used to regulate heart rate?
Hormones
- epinephrine, norepinephrine, thyroxine, glucagon
Ions
