Heart Flashcards
How big is the heart?
fist sized
What is the bottom of the heart called?
apex
How is the apex positioned?
points down and towards the left
How many chambers are the heart divided into?
four
What are the four chambers of the heart divided into?
2 atria and 2 ventricles
Atria location
superior of the heart
Each atrium contains what?
auricle
Auricle define
expansion area that increases the blood holding capacity of the atrium
What is the function of the atrium?
receive blood from the lungs or the body (blood goes to atria when it comes back to the heart)
Ventricles characteristics
Walls of the left ventricle are thicker than the walls of the right ventricle
Ventricles function
to pump blood to the lungs (right/pulmonary) or body (left/systemic)
Why is the left ventricle of the heart thicker than the right ventricle?
Left side thicker because has to pump blood further
What is the pericardial sac?
the fluid-filled sac that surrounds/covers the heart
What are the three components of the pericardial sac?
- fibrous pericardium
- visceral pericardium
- pericardial fluid
What is the fibrous pericardium?
the outermost layer of the pericardial sac
What is the visceral pericardium?
the innermost layer of the pericardial sac
Where is the pericardial fluid located?
between the fibrous and visceral pericardium
What is another name for the visceral pericardium?
epicardium
What is the function of the pericardial fluid?
reduce friction/heat and lubricate
What are the three layers of the heart?
- epicardium/visceral pericardium
- myocardium
- endocardium
What kind of tissue is the epicardium made of?
epithelium tissue
What kind of tissue is the myocardium composed of?
cardiac muscle
The myocardium contains what structures?
blood vessels/need energy
What kind of tissue is the endocardium made of?
Endothelium tissue
What are the characteristics of cardiac muscle cells?
- striated
- are short and branched
- contain a single nucleus
- contain a large number of mitochondria
- Intracellular space is filled with loose connective tissue and many capillaries
How are cardiac cells connected?
intercalated discs
What are intercalated discs?
Specialized cell junctions that are made of desmosomes and gap junctions
Desmosomes function
hold cell together/cell-to-cell connection
Gap junctions function
play an important role in impulse conduction
What is the function of the heart valves?
prevent regurgitation: backflow of blood
What are the two sets of valves of the heart?
- Atrioventricular valves
- Pulmonary semilunar valve and Aortic semilunar valve
Where are atrioventricular valves located?
between atria and ventricles
What is the function of the atrioventricular valves?
Separate the atria from the ventricles (top/bottom)
What are the two atrioventricular valves?
- Tricuspid valve (right) = like trap doors (tri- = three flaps)
- Bicuspid (mitral) valve (left)(bi- = two flaps)
What is the function of the chordae tendineae attached to papillary muscles?
Eversion = keeps flaps/valves from coming open/holds them closed
Which side of the heart is always bigger than the other?
left is always bigger than the right
What is the function of the pulmonary semilunar valve and aortic semilunar valve?
Separate the heart from arteries
What is the fibrous skeleton?
Dense connective tissue that forms rings around valves providing support
What are the functions of the fibrous skeleton?
- Foundation for valves (anchor)
- Prevention of overstretching
-Insertion point for muscle (myocardium) - Electrical insulator between atria and ventricles
What is the purpose of the electrical insulation of the fibrous skeleton?
So that the electrical signal does not directly pass from the atria to the ventricles, this way the signal is forced to use the conduction system
What is the function of the coronary vessels?
supply heart muscle with O2 and nutrients and remove waste products (CO2)
What are the functions of arteries and veins?
- arteries: carry blood away from the heart
- veins: return blood back to the heart
What is the pathway of blood?
Blood, low in O2 returns from body via the vena cavae (2 veins)
- Right atrium
- Tricuspid valve
- Right ventricle
- Pulmonary semilunar valve
- Pulmonary trunk/arteries
Lungs to pick up O2 and release CO2
- Pulmonary vein
- Left atrium
- Bicuspid valve
- Left ventricle
- Aortic semilunar valve
- Aorta
The cardiovascular system is made up of how many systems?
two
What are the two systems of the cardiovascular system?
- Pulmonary circuit (right side of the heart to the lungs)
Systemic circuit (left side if the heart to the rest of body)
The heart is myogenic. What does that mean?
If the pressure within a vessel is suddenly increased, the vessel responds to the sudden stretching of the wall by constricting. Diminishing pressure within the vessel causes relaxation and vasodilation
What cells are responsible for the myogenic nature of the heart?
autorhythmic cells
What are autorhythmic cells?
The autorhythmic cells serve as a pacemaker to initiate the cardiac cycle (pumping cycle of the heart) and provide a conduction system to coordinate the contraction of muscle cells throughout the heart.
Autorhymthic cells characteristics
- Specialized cardiac cells
- Unstable membrane potentials (Action potentials)
- Pacemaker potentials
- Establishes fundamental rhythm of heart
What three cell groups act as pacemakers?
- Sinoatrial node (SA node)
- Atrioventricular node (AV node)
- Conducting cells coming off the AV node
What determines the pace of the heart?
Rate of the heart is determined by the fastest group of pacemaker cells
Where is the location of the Sinoatrial node (SA node), and what is its bpm?
(outer right atrium and 80 bpm)
What is another name for the Sinoatrial node (SA node)?
“Pacemaker”
Where is the location of the Atrioventricular node (AV node), and what is its bpm?
(towards the center of the heart in the right atrium and 50 bpm)
Where is the location of the Conducting cells, and what is its bpm?
coming off the AV node and 30 bpm
What are the two conducting cells of the heart?
- AV bundle and bundle branches
- Purkinje fibers = depolarize on their own (30 bpm)
What is the function of the AV node?
delays signal between the atria and ventricle, thus separating the atrial and ventricular contractions
The heart rate is determined by the pacemakers, but what two systems can modify the heart rate?
ANS (autonomic nervous system) and endocrine system
Depolarization =
less negative (ex. -70mV to -50mV)
Cardiac Excitation: Step 1
Signal begins at SA node
Cells depolarize
This creates an action potential
Signal moves through the cells of atria via gap junctions (conduction)
This wave of depolarization causes atria to contract
Cardiac Excitation: Step 2
Signal spreads to AV node from SA node
Signal travels through AV node into the bundle of His (or AV bundle)
Signal travels down the interventricular septum via the left and right bundle branches
Signal travels up the walls of the ventricles via the Purkinje fibers
What happens after the action potential is generated by the SA node and travels through the conduction system?
Action potential spreads through the contractile cells
What are the three phases of a contraction of the heart?
- Depolarization
- Plateau
- Repolarization
Depolarization
Contractile fibers are brought to threshold by excitation of neighboring fibers
Voltage-gated Na + gates open
Rapid influx of Na+ (causes AP)
Depolarization
Na + gates close
Plateau
Voltage-gated slow Ca+2 gates open in cell membrane and SPR
Ca +2 enters the cell from ECF (extracellular fluid) and SPR (sarcoplasmic reticulum)
Some Ca +2 helps uncover myosin binding site on actin (in sarcomeres)
Na+ pumps turn on
Na+ leaves cells, balancing the Ca +2 entering, causing a plateau (steady)
Depolarization lasts 175 msec (much longer AP)
Repolarization
Slow voltage-gated K + channels open
K + rapidly effluxes
Ca +2 gates shut
K + leaves the cell, repolarizing cell
Return to resting potential
Refractory period function
The result is no contraction until relaxation is underway
Prevention of tetanus in the heart
Functional reason: in order for the heart to pump blood, ventricles must alternately fill (relaxation) and then empty (contraction)
How do the atria and ventricles contract?
in alteration; the atria contract first, while the ventricles are relaxed
Ventricular Relaxation (diastole)
- the pressure begins to decrease because the ventricles relax
-AV valves (bi and tricuspid) are shut, semilunars are open
- blood arteries begins to flow back due to reduction in pressure
- the semilunar valves to shut (because blood tried to go/flow back); all 4 valves are shut
- continued relaxation, ventricular space expands, further decreasing pressure
- ventricular pressure falls below atrial pressure, the AV valves open and the ventricular filling begins
Ventricular diastole: Ventricular filling
- rapid ventricular filling
- Gravity - SA node fires and the atria contract (systole) which finishes filling the ventricles
- semilunar valves are closed and the AV valves are open
Ventricular contraction (systole)
- near the end of atrial systole, the AP from the AV node causes a depolarization of the ventricles
- ventricular contraction begins from apex, pushing blood up against the AV valves, closing them
all 4 of the heart valves are shut
- ventricles continue to contract, increasing ventricular pressure
the left ventricle (thicker) has greater pressure than right
- when ventricular pressure exceeds arterial/blood pressure, semilunar valves open
- blood flows out of the heart and continues until the ventricles start to relax
What triggers the contraction of the ventricles?
Purkinje fibers
