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What is the shape of the heart?
A Hollow Cone Shape
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Where does the heart point to?
The Right shoulder and the Left Hip
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How much does the heart weigh?
250g-350g
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What is the Angle of Lewis?
The bend on the sternum at the Manubrium and Body, Point of maximum intenstiy
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Describe the Fibrous Sac
- Not expandable
- Anchors the heart to the surrounding structures
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What is Pericardial Friction Rub?
When there is a lack of pericardial fluid and the heart rubs against the outer wall
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What is Cardia Tamponade?
When there is too much pericardial fluid
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What are the 3 layers of the wall of the heart?
- Inner-Endocardium
- Middle- Myocardium
- Outer- Epicardium
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Describe the Inner layer of the heart
- Epicardium
- Simple Squamous Epithelium
- Lines inner portion of the heart as well as the blood vessels
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Describe the Middle layer of the Heart
- Myocardium
- Made up of Muscle
- Needs a good blood supply
- Is supplied by the left and right coronary arteries
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Describe the Outer layer of the Heart
- Epicardium
- Visceral layer of the Serous Pericardium
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What branches off of the Left Coronary Artery?
- Cirumflex Artery
- Anterior Interventricular Artery
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What branches off of the Right Coronary Artery?
- Marginal Artery
- Posterior Interventricular Artery
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Where do the Anterior and Posterior Interventricular Arteries meet?
Anastomoses
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What causes a Myocardial Infarction or Askemia?
When a vessel is blocked by a thrombus or an Atheroma
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Where are the most common arteries to be blocked by an atheroma or a thrombus?
- Anterior Interventricular Artery
- Origin of Right Coronary Artery
- Circumflex Artery
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Where do Cardiac veins bring blood to?
The Coronary Sinus and then to the right atrium of the heart
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What are the four chambers of the heart?
- Right Atrium
- Right Ventricle
- Left Atrium
- Left Ventricle
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What are the openings in the Right Atrium?
- Superior Vena Cava
- Inferior Vena Cava
- Opening of the Coronary Sinus
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What are the openings in the Right Ventricle?
- Pulmonary Valve
- Tricuspid Valve
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What are the openings of the Left Atrium?
Pulmonary Veins (4)
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What are the openings of the Left Ventricle?
Aortic Valve
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What are the muscles called in the Ventricles?
- Trabeculae Carnae
- Papillary Muscles
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What attaches to the papillary muscles?
Chordae Tendinae
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Where are the pectinate muscles located?
- Right Atrium
- No muscles in the left atrium
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What is an Auricle?
The additional space attached to the atriums
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What is the Absolute Refractory period?
When the muscle is being stimulated, it cannot be stimulated again during this period
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What is the relative refractory period?
When the muscle can be stimulated again
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What is the resting membrane potential of the skeletal muscle?
-85mV
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What is the resting membrane potential of the 99% of Cardiac Muscles?
-90mV
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What is the resting membrane potential of the 1% or Cardiac Muscles?
-60mV
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What is the threshold for skeletal muscle?
-55mV
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What is released to maintain the stimulation of Cardiac musscles?
Ca+
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Describe the AP of the 99% of Cardia Muscles
- 1- Depolarizes Rapidly
- 2-Voltage regulated slow Calcium channels open to maintain stimulation
- 3- Calcium channels close and repolarization occurs
- 4- Potassium channels remain open
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What is Complete Tetnus?
When muscle relaxation is eliminated, occurs in skeletal muscle but not cardiac
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Why does cardiac muscle require complete relaxation?
To Allow the heart to fill up with blood
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What is Ventricular Fibrilation?
Post heart attack the heart's beat is irregular, therefore the blood doesn't have time to leave the heart
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What are the pacemaker cells?
- the 1% of Cardiac Muscles
- SA Node
- AV Node
- AV Bundle
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Describe the SA Node
- Main pacemaker of the heart
- Sets the heartrate
- Sends AP 70x-80x per minutes
- If working properly, the others are quiet
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Describe the AV Node
- Sends AP 40x-60x per minute
- If SA Node stops working, AV Node will take over
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Describe AV Bundle
If both SA node and AV Node stop working, AV Bundle will take over
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What is a Fixed Interval Pacemaker?
Acts as the SA Node sending out AP at a certain frequency
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What is a Deman Pacemaker?
Sends out AP if the SA Node stops working
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Where is the SA Node located?
The posterior wall of the Right Atrium, inferior to the Superior Vena Cava
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Where is the AV Node located?
Inferior portion of the Interarterial Septum, overlooking the Tricuspid
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Where is the AV Bundle located?
- Inferior portion of the interartierial septum
- Left+Right Bundle- Interventricualr Septum
- Porkinje Fibers- Wall of the Ventricles
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Pathway of the AP
- Sa Node
- Internodal Arterial Pathways and Atriums
- Delay of .04 seconds
- AV Node
- AV Bundle
- Left and Right Bundle
- Porkinje Fibers
- Ventricles
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Why is there a need for the delay in the pathway of the AP?
The Atrium needs to pump before the Ventricles do
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Why are Cardiac Muscles cells different than Skeletal Muscle cells?
- They are interrelated
- They contain Desmosomes (anchoring junctions)
- They contain gap junctions (allow for flow of ions)
- Only one needs to be stimulated
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What is the function of the CT in the heart when it comes to AP?
- The CT forms an elaborate network that has a high concentration in the atrial-ventricular junctions.
- CT does not carry electricity, so it stops the pulse from going straight into the ventricles
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What is the CT's function in the heart?
- Helps with distribution of AP
- Distributes force of contraction
- Prevents over expansion of the heart
- Provides support tissue
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What does an EKG measure?
The electrical current in the heart
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What is shown in the QRS complex of the EKG?
Ventricular Depolarization
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What is shown at the P junction of an EKG?
Atrial Depolarization
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What is shown at the T junction of an EKG?
Ventricular Repolarization
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What makes the 2 sounds of the heart?
- 1-Closure of Tricuspid and Bicuspid
- 2- Closure of Aortic and Pulmonary Valve
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What occurs during systole?
Blood is pumped out of the heart
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What occurds during diastole?
Heart is in relaxation and is filling up with blood
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Where is the systolic and diastolic measured from?
The mmHg in the Aorta
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What does the umbilical chord contain?
1 vein and 2 arteries
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What are the two veins that carry oxygen?
- Pulmonary Vein
- Umbilical Vein
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Where does the oxygenated blood in a fetus flow through?
Most of it bypasses the liver through the Ductus Veinosis and empties into the Interior Vena Cava
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Describe the blood flow in a fetus
- Inferior/Superior Vena Cava
- Right Atrium
- Foraman Ovale>L Atrium>LVentricle
- R. Vent>Pulmonary Trunk>Ductus Arteriosus>Aorta
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What does the umbilical Vein become after birth?
The Round Ligament of the Liver
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What does the Foramen Ovale become after birth?
Fossa Ovalis
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What does the Ductus Venosus become after birth?
Ligamentum Venosum
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What does the Ductus Arteriosus become after birth?
Ligamentum Arteriosum
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What does the Proximal Umbilical Arteries become after birth?
Superiod Vescical Arteries
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What does the Distal Umbilical Arteries become after birth?
Medial Umbilical Ligament
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What is the first seputm and foramen formed in a fetus?
Septum Primum and the Ostium Primum
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What occurs when the Septum Primum grows completely divides the atriums?
The Ostium Sicundum appears (fossa ovalis) and the Septum Sicundum starts to grow up towards the left atrium
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How do you determine Cardiac Output?
Cardiac Output= Heart Rate x Stroke Volume
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How do you determine Stroke volume?
Stroke Volume = End Diastolic Volume - End Systolic volume
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What is the EDV?
Volume that collects in ventricles during diastole
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What affects the EDV?
- Length of Ventricular Diastole
- Venous Return
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What is the ESV?
Volume of blood remaining in the ventricle after contraction
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What affects the ESV?
- Force of Contraction
- Arterial Pressure
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What external factors affect Stroke Volume?
- 1-Preload
- 2-Contractility
- 3-Afterload
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What is Frank Starling's Law of the Heart?
- Refers to Preload
- An important intrinsic factor is the length of cardiac muscle fibers prior to contraction
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What is inotropism?
Factors affecting contractility of the heart
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What is a positive inotropic factor?
Sympathetic Nerve System
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How does the sympathetic Nervous System affect contractility of the heart?
Releases the neurotransmitter Norepeniephrine which binds to the Beta 1 Adrenergic Receptors which activate Adenylate cyclase which produces cAMP which activated Protein Kinase which opens Slow Calcium Channels
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How does Epinephrine affect contractility?
The same way that norepinephrine affects it
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What are the 4 positive intropisms?
- Sympathetic NS - Norepinephrine and Epinephrine
- Thyroxine
- Glucagon
- Digitalis- Digoxin
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What does Digitalis do the the pumps in the cardiac muscles?
Inhibits K-Na pump, which means more Na is pumped into the cell. The Na-Ca pump revereses and brings Ca into the cell
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What are some negaive intropic factors?
- Acidosis- when the body becomes more acidic
- Hyperkalemia- high K in blood
- Drugs- Calcium blockers
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What is the afterload?
Pressure that the heart needs to pump against
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What are the factors affecting afterload called?
Chronotropics
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What is a positve chronotropic?
Sympathetic nervous sytem- releases norepinephrine, which increases Na influx, so there are more APs per minute
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What is a negative chronotropic?
Parasympathetic NS- Releases Acetylcholine, binds to cholinergic receptors (Muscarinic) specifically M2, creats K eflux, which makes cell more negative, so there are less APs per minutre
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What do you call HR > 100 bpm?
Tachycardia
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What do you call HR < 60 bpm?
Bradycardia
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What would happen to the hR is the vagus nearve were severed?
HR would increase to around 100 bpm
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