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78 Cards in this Set

  • Front
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Function OF CVS

}transport mechanism for human body

Functions of the Heart

1. Generating blood pressure
2. Routing blood
3. Ensuring one-way blood flow
4. Regulating blood supply
1. Generating blood pressure
* flow = pressure/resistance. Flow is dictated by heart resistance, dictated by blood vessels
* heart beats ~ 4-5 L of blood/minute at rest
1. Routing blood:
1. separates pulmonary, systemic, chambers separate blood
1. Ensuring one-way blood flow:
1. valves (preventing backflow) , arteries use pressure
1. Regulating blood supply
* Changes in contraction rate and force match blood delivery to changing metabolic needs
* Example: riding a bike (blood flow to legs increase, blood flow to internal organs decrease)

ARTERY AND VEIN

AWAY AND TO THE HEART

Where is the heart located?

* mediastinum: area from the sternum to the vertebral column and between the lungs
* parietal pleura
* serous membrane lines thoracic cavity
* pleura cavity:
* serous fluid ( lubricate and reduce friction)
* fibrous pericardium
* tough CT, creates cavity of heart, outer line, separates heart and lungs, serous membrane
* Apex
* Blunt rounded point of cone. Directed anteriorly, inferiorly and to the left
* Base
* Flat part at opposite of end of cone. Directed posteriorly, superiorly and to the right

* Heart Note

* tilted left
* 1/3 mass on right, 2/3 left

Superior right point:

at the superior border of the 3rd right costal cartilage

Superior left point:

at the inferior border of the 2nd left costal cartilage 3cm to the left of midline

Inferior left point:

at the 5th intercostal space, 9 cm from the midline

* Inferior right point
* at superior border of the 6th right costal cartilage, 3 cm from the midline
* palpation:
* pushing down on structures outside of the body to feel for internal structures

Pericardium

or pericardial sac: cover around heart, creates cavity around heart

Fibrous pericardium

tough fibrous outer layer. Prevents over distention; acts as anchor outer most layer, tough fibrous outer layer, anchor for the heart >> attached to the diaphragm at bottom and vessels of the top. Prevents over dissenstion (can only grow or expand to a certain degree) the wall of the cavity. Separates heart from lungs

Serous pericardium

thin, transparent, inner layer. Simple squamous epithelium inner layer, double layer, serous membranes (continuous membrane with sera fluid) 1) parietal pericardium: in contact with the fibrous pericardium outer layer 2) visceral pericardium (pericardial sac): also called the epicardium (heart tissue), inner layer, close contact with the wall of the heart

Parietal pericardium:


Visceral pericardium

lines the fibrous outer layer



(epicardium): covers heart surface



* The two are continuous and have a pericardial cavity between them filled with pericardial fluid
* pericardial fluid: lubrication to protect from abrasion

Epicardium

– visceral layer of serous pericardium

* Myocardium
* – cardiac muscle layer is the bulk of the heart
Endocardium
* – chamber lining & valves - simple squamous with some underlying connective tissue, made up of cardiac muscle (trabeculae carneae)
* Auricles
* Auricles create pockets, are extensions of the atrias

Sulci:

grooves on surface of heart containing coronary blood vessels and fat

* coronary sulcus
* encircles heart and marks the boundary between the atria and the ventricles
* anterior interventricular sulcus
* marks the boundary between the ventricles anteriorly
* posterior interventricular sulcus
* marks the boundary between the ventricles posteriorly
* right atrium:
* receives blood from superior, inferior vena cava and the coronary sinus (brings blood back from the cardiac tissue)
* tricuspid valve:
* AV value, separates atria from the ventricle, 3 cusp
* right ventricle:
* has muscles cone shaped, raised bundles of cardiac tissue: papillary muscles (contract) attached to the chord tendineae (also attaches onto the valves which keeps them functioning)
* pulmonary semilunar valve:
* allows blood to flow to the lounge and stops blood from moving back into the right ventricle
* pulmonary trunk:
* splits in to the right and left pulmonary artery to give blood to both lungs
* left atrium
* receiving blood from lungs, has bicuspid valve
* bicuspid valve
two cusps
* left ventricle:
* walls thicker because it has to pump blood to the rest of the body, papillary muscles, chord tendinae
* interventricular septum
* thickened area that separates ventricle
* aortic semilunar valve:
* blood from the left ventricle to the aorta

Relaxed Left Ventricle

cardiac muscle is relaxed and the papillary muscles are also relaxed which allows for low tension on the chordae tendinae. Blood coming back from the lungs so there is more pressure in the atrium compared to ventricle because it is empty. This allows for filling to occur. High pressure in the aorta and low pressure from the ventricle allows for the semilunar valve to stay closed and the AV valve to remain open for filing

Contracted Left Ventricle

atria contract before ventricle and than the ventricle begins to contract. This makes the volume smaller and the pressure higher inside the heart and it also contracts the papillary muscles which holds the valves to stop from inversion into the atrium. Blood pressure pushed AV valves closed. Semi lunar valves are pushed open when blood pressure in heart is greater than in the aorta

Valves:

ensures one-way flow of blood

Atrioventricular valves (AV valves)

• Leaf-like cusps attached to papillary muscles by tendons (chordae tendineae). Right has three cusps (tricuspid). Left has two cusps (bicuspid, mitral). When valve is open, canal is atrioventricular canal.

Semilunar valves

• Right (pulmonary); left (atrial). Each cusp is shaped like a cup. When cusps are filled, valve is closed; when cusps are empty, valve is open

Coronary Circulation

* Coronary circulation is blood supply to the heart
* Heart as a very active muscle needs lots of O2
* When the heart relaxes high pressure of blood in aorta pushes blood into coronary vessels
* Many anastomoses
* anastomoses
*
* connections between arteries supplying blood to the same region, provide alternate routes if one artery becomes occluded

Right coronary artery

exits aorta just superior to point where aorta exits heart; lies in coronary sulcus. Extends to posterior aspect of heart

* Right marginal artery (lateral wall of right ventricle)
* Posterior interventricular artery lies in posterior interventricular sulcus, supplies posterior and inferior aspects of heart

Left coronary artery

exits aorta near right coronary. Branches

* Anterior interventricular artery (left anterior descending artery) in anterior interventricular sulcus important because it supplies a large part of left ventricle

* Left marginal artery supplies lateral wall of left ventricle
* Circumflex artery extends to posterior aspect

Great cardiac vein:

drains left side of the heart

Small cardiac vein:

drains right margin of heart

Coronary sinus:

large venous cavity, empties into right atrium, merging point of many veins

Heart Skeleton

fibrous CT plate that separates atrium and ventricle

* forms rings around valves: provides structural support
* provides attachment point for cardiac muscle
* provide barrier for electrical signals of ventricles and atria

Cardiac Muscle

• Elongated, branching cells containing 1-2 centrally located nuclei (centrally located)


• Contains actin and myosin myofilaments

* lots of mitochondria (constant supply of ATP)
* T tubes are wider and wrap around myofibrils at Z disks
* SR are near T tubes at certain points, can sense AP
* no terminal cistera
* Intercalated disks
* Electrically, cardiac muscle of the atria and of the ventricles behaves as single unit
* desmosome:
* Intercalated disks:
* specialized cell-cell contacts; connect point between 2 cardiac cells >> electrical synapse: gap junctions >> connecting cytoplasm of cells to other neighbouring cells >> which allows signal to carry through all cells
* desmosome:
* specialized structures that connects cells together
* SA node:
* sinoatrial node. Generate spontaneous action potentials. Action potentials pass to atrial muscle cells and to the AV node; pacemaker of heart, dictates the speed of AP, the faster, in right atrium close to the superior vena cava entry point
* AV node:
* atrioventricular node. Action potentials conducted more slowly here than in any other part of system. Ensures ventricles receive signal to contract after atria have contracted; fires (depolarizes) after SA, located between inter-atrial septum, close to AV valves, fewer gap junctions

Conducting System of the heart

- SA node


- AV node

* these cells have fewer myofibrils
* - different ion channels
* - may have different diameters and number of gap junctions
* AV bundle
* right and left bundle branches
* purkinje fibres
* AV bundle:
* passes through hole in cardiac skeleton to reach interventricular septum; brings signal to ventricle, AP speeds up
* Right and left bundle branches:
* extend beneath endocardium to apices of right and left ventricles
* Purkinje fibers:
* Large diameter cardiac muscle cells with few myofibrils. Many gap junctions. Conduct action potential to ventricular muscle cell, conduct AP quickly send electrical signal to nonspecialized cardiac muscle cells

Cardiac muscle action potential

Resting state:


• High extracellular Na+ and Ca2+; high intracellular K+
1) Depolarization: Na+ influx (Na+ channels opened, K+ channels close, Ca2+ channels start to open)


2) Early repolarization: Some voltage-gated K+ channels open, causing early repolarization. (Na+ channels close)
Plateau Phase: some Ca2+ channels are open, producing the plateau by slowing further repolarization; lengthens AP


3) Final repolarization: many K+ channels open, Ca2+ channels close


• Na+/K+ ATPase (“pump”) restores ion gradient

Differences Between Skeletal and Cardiac Muscle Physiology

• Cardiac: action potentials conducted from cell to cell. Skeletal: action potential conducted along length of single fiber


• Cardiac: rate of action potential propagation is slow because of gap junctions and small diameter of fibers. Skeletal: it is faster due to larger diameter fibers.


• Cardiac: calcium-induced calcium release (CICR). Movement of Ca2+ through plasma membrane and T tubules into sarcoplasm stimulates release of Ca2+ from sarcoplasmic reticulum


Autorhythmicity: SA Node Action Potential

* Self-generating action potentials in regular time intervals


1) Pacemaker potential: Na+ “leakage” into cell, causes resting membrane potential to move towards threshold.


• Inside of cell becomes more electrically positive.


• K+ channels closing


2) Depolarization phase:


• Ca2+ channels open, K+ channels closed


3) Repolarization phase:

* Ca2+ channels close, K+ channels open

** Notes

* pacemaker cells generate own AP
* SA node forces at faster rate >> stimulates cells: key pacemaker for the heart
* resting membrane potential: -60 (pacemaker potential)
* Na+ leak channels
* depolarization: voltage gated Ca2+ close, K+ opens
* happens continually

Refractory Period

* Absolute: Cardiac muscle cell completely insensitive to further stimulation
* Relative: Cell exhibits reduced sensitivity to additional stimulation
* Long refractory period prevents tetanic contractions
* heart needs to relax for the chambers to actually fill

Electrocardiogram - ECG

Record of electrical event in the myocardium that can be correlated with mechanical events (contraction, relaxation, valves open and close)

P wave:
* depolarization of atrial myocardium. Signals onset of atrial contraction, when SA node first fires
QRS complex:
* ventricular depolarization and signals onset of ventricular contraction. Repolarization of atria simultaneously. Bigger because ventricles work harder, atria begins to relax
* T wave:
* repolarization of ventricles; precedes ventricular relaxation
PQ interval
* or PR interval: 0.16 sec; atria contract and begin to relax, how long it takes for atria to contract and relax
QT interval:
* 0.36 sec; ventricles contract and begin to relax, time it takes for ventricles to contract and relax

Cardiac Cycle

* happens is a single heartbeat
* Heart is two pumps that work together, right and left half

• Repetitive contraction (systole) and relaxation (diastole) of heart chambers


• Blood moves through circulatory system from areas of higher to lower pressure.


– Contraction of heart produces the pressure

Systolic state

(2 phases): chamber contracts and ejects blood







Phase 1: Isovolumetric contraction
Phase 2: Ejection

Diastolic state
* (3 phases): chamber fills with blood




Phase 3: Isovolumetric relaxation
Phase 4: Passive ventricular filling
Phase 5: Active ventricular filling (atrial systole)

What artery is called they widow maker

anterior interventricular artery: left anterior descending,





important because it supplies a large part of left ventricle.






Called widow maker because if it is blocked the left side of the heart will die and person will die because left ventricle supplies body with blood