Lecture

it is lined by serous membrane that is subdivided into parietal and visceral

it covers closely to the heart, (like skin)

it lines the surface of the pericardial sac

it is made of dense connective tissue, it also stabilizes the heart within the mediastinum

Intercellular communication, it communicates through small openings between each of the cells, it helps with action potential-polarization of ions

They convey the farce of the contractions from cell to cell. The connect cardiac muscles

help move neighboring cells as one unit (syncytium)

HEART ANATOMY (used): Interventricular septum, interatrial septum

HEART ANATOMY: Ventricles

HEART ANATOMY: Chordae teninae, bicuspid/tricuspid valves, papillary muscles, pulonary & aortic semilunar valves

HEART ANATOMY: Nodal cells (conducting system)

pulmonary, coronary, systemic

• Produce powerful contractions, has a long plateau phase, long slow twitch, long refractory period
• Controls and coordinates heartbeat

• Atria contract > push blood to ventricles > ventricles contract > push blood out of the heart
• SA node generates impulses at regular intervals with a brief pause

• Action potentials to release Ca++ to bind to troponin
• Expose active sites on the actin
• Cause sarcomere shortening and muscle contraction

• Action Potentials
• Length of the contractions

• Ca++ enters from extracellular fluid during the plateau phase of action potential
• This arrival of Ca++ causes the release of Ca++ from the SR
• Skeletal muscle fiber contraction quickly, however cardiac muscles contracts longer and will continue until the plateau ends

• Cardiac > rapid due to fast channels and massive influx of Na+
• Skeletal > same thing

• Cardiac > Resting potential -90mV threshold -75mV
• Skeletal > Resting potential -85mV threshold -50mV

• Cardiac > voltage regulated @ +30mV > slow voltage; plateau Ca++ open, will remain open at 0mV of 175 m/sec
• Skeletal > voltage regulated +30mV; no plateau

• Cardiac > slow K+ channels, open to restore resting potential
• Skeletal > same

• Cardiac > During depolarization; plateau and portion of repolarization, very long
• Skeletal > During depolarization; normal length

• Cardiac > Takes place during repolarization
• Skeletal > takes place during repolarization & hyperpolarization

• Nodal cells > Stop watch; reaches threshold first and sets heart rate
• Conducting cells > conductor; distributes stimuli to myocardium

impulse spreads across atria to atrioventricular (AV) node > AV bundle and bundle branchs via Purkinje fibers to ventricles

The heart can conduct impulses without external stimulation unlike that of the skeletal muscles

Each time the heart will repolarize it and will gradually move toward threshold, (always ready to start again)

• Bradycardia is too little K+; slower than normal heart rate
• Trachycardia is too much K+; faster than normal heart rate

• protein channels > sodium, potassium, calcium
• Started by the prepotential but it is initiated by massive influx of sodium
• The plateau is caused by calcium channels remain open for 175 m/sec at 0 mV
• Repolarization > uses potassium channels that open & calcium channels close
• (no leak channels=no hyperpolarization)

Potassium helps restore resting potential

• Systole > contraction phase; ventricles together
• Diastole > Relaxation phase

SV (stroke volume)= EDV-ESV

• Preload: filling with blood EDV
• Contractility: force produced during contraction
• Afterload: resistance in circulation ESV

CO(ml/min)=heart rate(beats/min) * stroke volume(ml/beat)

• "more in"="more out"
• Larger EDV=larger stroke volume

• Basic control in the medulla oblongata(brain stem)
• Cardioacceleratory center > accelerate heart rate (sympathetic neurons)
• Cardioinhibitory center > lower heart rate (parasympathetic neurons)
• Blood pressure sensors (baroreceptors)
• Oxygen, carbon dioxide receptors (cemoreceptors)

• Parasympathetic release of Ach which extends repolarization and decrease of heart rate
• Sympathetic release of NE or E which shortens repolarization and accelerates the rate of spontaneous repolatization

• Adrenal medulla hormones (E/NE)
• Thyroid hormones
• Glucagon

Arteries > Arterioles > Capillaries > Venules > Veins

• Contain layers of tissue: Tunica externa(connective tissue) > Tunica media (smooth muscle) > Tunica intima (epithelium)
• Thicker walls

• Fenestrated Capillaries
• >contain pores or windows
• >rapid exchange of water and solutes between plasma and interstitial fluid

• Exchange between blood and cells take place
• organized into interconnected capillary beds
• vasomotion of precapillary sphincters(bands of smooth muscle) controls flow

• collect blood from capillaries
• merge into medium-sized veins
• merge then into large veins
• BP is low and valves keep blood flowing to the heart

• Fetus > umbilical arteries > placenta > umbilical vein > fetus
• Umbilical vein > ductus venous
• Hepatic veins > ductus venous > inferior vena cava > right atrium > foramen ovale > left atrium > pumonary trunk > ductus arteriosus > arota > umbilical arteries