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What is the shape of the heart?
A Hollow Cone Shape
Where does the heart point to?
The Right shoulder and the Left Hip
How much does the heart weigh?
What is the Angle of Lewis?
The bend on the sternum at the Manubrium and Body, Point of maximum intenstiy
Describe the Fibrous Sac
- Not expandable
- Anchors the heart to the surrounding structures
What is Pericardial Friction Rub?
When there is a lack of pericardial fluid and the heart rubs against the outer wall
What is Cardia Tamponade?
When there is too much pericardial fluid
What are the 3 layers of the wall of the heart?
- Middle- Myocardium
- Outer- Epicardium
Describe the Inner layer of the heart
- Simple Squamous Epithelium
- Lines inner portion of the heart as well as the blood vessels
Describe the Middle layer of the Heart
- Made up of Muscle
- Needs a good blood supply
- Is supplied by the left and right coronary arteries
Describe the Outer layer of the Heart
- Visceral layer of the Serous Pericardium
What branches off of the Left Coronary Artery?
- Cirumflex Artery
- Anterior Interventricular Artery
What branches off of the Right Coronary Artery?
- Marginal Artery
- Posterior Interventricular Artery
Where do the Anterior and Posterior Interventricular Arteries meet?
What causes a Myocardial Infarction or Askemia?
When a vessel is blocked by a thrombus or an Atheroma
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
Where do Cardiac veins bring blood to?
The Coronary Sinus and then to the right atrium of the heart
What are the four chambers of the heart?
- Right Atrium
- Right Ventricle
- Left Atrium
- Left Ventricle
What are the openings in the Right Atrium?
- Superior Vena Cava
- Inferior Vena Cava
- Opening of the Coronary Sinus
What are the openings in the Right Ventricle?
- Pulmonary Valve
- Tricuspid Valve
What are the openings of the Left Atrium?
Pulmonary Veins (4)
What are the openings of the Left Ventricle?
What are the muscles called in the Ventricles?
- Trabeculae Carnae
- Papillary Muscles
What attaches to the papillary muscles?
Where are the pectinate muscles located?
- Right Atrium
- No muscles in the left atrium
What is an Auricle?
The additional space attached to the atriums
What is the Absolute Refractory period?
When the muscle is being stimulated, it cannot be stimulated again during this period
What is the relative refractory period?
When the muscle can be stimulated again
What is the resting membrane potential of the skeletal muscle?
What is the resting membrane potential of the 99% of Cardiac Muscles?
What is the resting membrane potential of the 1% or Cardiac Muscles?
What is the threshold for skeletal muscle?
What is released to maintain the stimulation of Cardiac musscles?
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
What is Complete Tetnus?
When muscle relaxation is eliminated, occurs in skeletal muscle but not cardiac
Why does cardiac muscle require complete relaxation?
To Allow the heart to fill up with blood
What is Ventricular Fibrilation?
Post heart attack the heart's beat is irregular, therefore the blood doesn't have time to leave the heart
What are the pacemaker cells?
- the 1% of Cardiac Muscles
- SA Node
- AV Node
- AV Bundle
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
Describe the AV Node
- Sends AP 40x-60x per minute
- If SA Node stops working, AV Node will take over
Describe AV Bundle
If both SA node and AV Node stop working, AV Bundle will take over
What is a Fixed Interval Pacemaker?
Acts as the SA Node sending out AP at a certain frequency
What is a Deman Pacemaker?
Sends out AP if the SA Node stops working
Where is the SA Node located?
The posterior wall of the Right Atrium, inferior to the Superior Vena Cava
Where is the AV Node located?
Inferior portion of the Interarterial Septum, overlooking the Tricuspid
Where is the AV Bundle located?
- Inferior portion of the interartierial septum
- Left+Right Bundle- Interventricualr Septum
- Porkinje Fibers- Wall of the Ventricles
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
Why is there a need for the delay in the pathway of the AP?
The Atrium needs to pump before the Ventricles do
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
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
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
What does an EKG measure?
The electrical current in the heart
What is shown in the QRS complex of the EKG?
What is shown at the P junction of an EKG?
What is shown at the T junction of an EKG?
What makes the 2 sounds of the heart?
- 1-Closure of Tricuspid and Bicuspid
- 2- Closure of Aortic and Pulmonary Valve
What occurs during systole?
Blood is pumped out of the heart
What occurds during diastole?
Heart is in relaxation and is filling up with blood
Where is the systolic and diastolic measured from?
The mmHg in the Aorta
What does the umbilical chord contain?
1 vein and 2 arteries
What are the two veins that carry oxygen?
- Pulmonary Vein
- Umbilical Vein
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
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
What does the umbilical Vein become after birth?
The Round Ligament of the Liver
What does the Foramen Ovale become after birth?
What does the Ductus Venosus become after birth?
What does the Ductus Arteriosus become after birth?
What does the Proximal Umbilical Arteries become after birth?
Superiod Vescical Arteries
What does the Distal Umbilical Arteries become after birth?
Medial Umbilical Ligament
What is the first seputm and foramen formed in a fetus?
Septum Primum and the Ostium Primum
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
How do you determine Cardiac Output?
Cardiac Output= Heart Rate x Stroke Volume
How do you determine Stroke volume?
Stroke Volume = End Diastolic Volume - End Systolic volume
What is the EDV?
Volume that collects in ventricles during diastole
What affects the EDV?
- Length of Ventricular Diastole
- Venous Return
What is the ESV?
Volume of blood remaining in the ventricle after contraction
What affects the ESV?
- Force of Contraction
- Arterial Pressure
What external factors affect Stroke Volume?
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
What is inotropism?
Factors affecting contractility of the heart
What is a positive inotropic factor?
Sympathetic Nerve System
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
How does Epinephrine affect contractility?
The same way that norepinephrine affects it
What are the 4 positive intropisms?
- Sympathetic NS - Norepinephrine and Epinephrine
- Digitalis- Digoxin
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
What are some negaive intropic factors?
- Acidosis- when the body becomes more acidic
- Hyperkalemia- high K in blood
- Drugs- Calcium blockers
What is the afterload?
Pressure that the heart needs to pump against
What are the factors affecting afterload called?
What is a positve chronotropic?
Sympathetic nervous sytem- releases norepinephrine, which increases Na influx, so there are more APs per minute
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
What do you call HR > 100 bpm?
What do you call HR < 60 bpm?
What would happen to the hR is the vagus nearve were severed?
HR would increase to around 100 bpm