Saturday, July 22, 2006
Heart
HEART- BIOLOGY 220
Heart weighs about 250 – 350 grams
Heart is a transport system pump using blood as a transport medium
Located in the mediastinum – medial cavity of the thorax
Point of maximal intensity is where you press your finger between the fifth and sixth rib, where the apex contacts the chest wall
Pericardium – double walled sac the encloses the heart
Fibrous pericardium – loose fitting superficial part of the pericardial Sac
Serous pericardium – thin slippery two layer serous membrane- parietal layer and visceral layer (also called the epicardium layer)
Inflammation of the pericardium – Pericarditis
Layers of the Heart:
Epicardium
Mycocardium
Endocardium
Atria
Ventricles
Interatrial septum
Interventricular septum
Coronary sinus
Superior and inferior vena cava
Four pulmonary veins enter the left atria from the lungs
Papillary muscles play a role in value function
Look at diagram on page 682 in textbook for circulatory system
Pulmonary circuit – blood vessels that carry blood to and from the lungs
Systemic circuit – blood vessels that carry the functional blood supply to and from all body tissues
Right side of the heart is the pulmonary circuit pump
Left side of heart is the systemic circuit pump
Coronary circulation is the functional supply of blood to the heart
(Know the parts of the heart)
Cardiac muscle is striated and contract by the sliding filament mechanism
Cardiac cells are short, fat and interconnected and has centrally located nuclei
Intracellular spaces of the Cardiac muscle contains CT matrix filled with capillaries
Intercalated discs contain desmosones and gap junctions
Cardiac muscle has a lot of mitochondria organelles which give cardiac muscle the ability to resist fatigue. The heart requires more O2 for its energy metabolism than does skeletal muscle.
Some cardiac muscle cells are self excitable and can initiate their own depolarization in a rhythmic way – Autorhythmicity
The heart contracts as a unit due to depolarization waves across gap junctions
Na+ channels are open longer in cardiac muscle – absolute refractory period explains why heart muscles are protected against tetanus
Na+ channels are opened during depolarization causing an AP
The depolarization wave causes the sacroplasmic reticulum to release Ca2+ ions which cause the myofilaments to sliding across themselves (actin and tropin)
The time that Ca2+ channels stays open helps to explain why the AP and contractile phase is so much longer in cardiac muscle than in skeletal muscle. This helps in the heart ejecting blood from its chambers.
Ischemic – when the heart is deprived of blood, the cells are starving for oxygen and begin to metabolize anaerobically making lactic acid. The rise in H+ hinders the cardiac cells ability to produce ATP which is needed for Ca2+ channel pumps to open into extracellular fluid. When you have an increase in H+ and Ca2+ levels, the gap junctions will close, bypassing the damaged cells and forcing AP to go elsewhere…heart attack.
Independent but coordinated activity of the heart is a function of:
1) presence of gap junctions
2) intrinsic cardiac conduction system –initiates and distributes impulses throughout the heart so that it beats in a coordinated fashion
(There is a section on autorythmic cells and AP on page 690 that is rather detailed that you might want to look at)
Autorythmic cells are found in the following:
1) SA node – pacemaker
2) AV node – above tricuspid valve
3) Bundle of HIS
4) Left and right bundle branches
5) Perkinje fibers which supply the papillary muscles and are more prominent on the left side of the heart
The cardiac centers are located in the medulla oblongata
EKG or ECG is a composite of all AP generated by nodal and contractile cells
Deflection waves are the following:
1) P wave – lasts about 0.08 sec and results from the depolarization wave from the SA node to the atria
2) QRS complex – results from ventricular depolarization and precedes ventricular contraction.
3) T wave is caused by ventricular repolarization and last 0.16 sec
Heart murmurs are do to thin heart walls, defective values.
Systole – contraction period
Diastole-relaxation period
Cardiac output – amount of blood pumped out by each ventricle per minute (70 ml x number of beats per minute (75, 72 )
Stroke volume is the volume of blood pumped out of heart per minute (70 ml)Starling Law of the Heart – check handout
Tachycardia – fast heartbeat
Bradycardia – slow heartbeat
If the left side of the heart fails – pulmonary congestion occurs-edema in lungs
If the right side of the heart fails, peripheral congestion-edema in body, most noticeable the ankles, feet and hands
Heart weighs about 250 – 350 grams
Heart is a transport system pump using blood as a transport medium
Located in the mediastinum – medial cavity of the thorax
Point of maximal intensity is where you press your finger between the fifth and sixth rib, where the apex contacts the chest wall
Pericardium – double walled sac the encloses the heart
Fibrous pericardium – loose fitting superficial part of the pericardial Sac
Serous pericardium – thin slippery two layer serous membrane- parietal layer and visceral layer (also called the epicardium layer)
Inflammation of the pericardium – Pericarditis
Layers of the Heart:
Epicardium
Mycocardium
Endocardium
Atria
Ventricles
Interatrial septum
Interventricular septum
Coronary sinus
Superior and inferior vena cava
Four pulmonary veins enter the left atria from the lungs
Papillary muscles play a role in value function
Look at diagram on page 682 in textbook for circulatory system
Pulmonary circuit – blood vessels that carry blood to and from the lungs
Systemic circuit – blood vessels that carry the functional blood supply to and from all body tissues
Right side of the heart is the pulmonary circuit pump
Left side of heart is the systemic circuit pump
Coronary circulation is the functional supply of blood to the heart
(Know the parts of the heart)
Cardiac muscle is striated and contract by the sliding filament mechanism
Cardiac cells are short, fat and interconnected and has centrally located nuclei
Intracellular spaces of the Cardiac muscle contains CT matrix filled with capillaries
Intercalated discs contain desmosones and gap junctions
Cardiac muscle has a lot of mitochondria organelles which give cardiac muscle the ability to resist fatigue. The heart requires more O2 for its energy metabolism than does skeletal muscle.
Some cardiac muscle cells are self excitable and can initiate their own depolarization in a rhythmic way – Autorhythmicity
The heart contracts as a unit due to depolarization waves across gap junctions
Na+ channels are open longer in cardiac muscle – absolute refractory period explains why heart muscles are protected against tetanus
Na+ channels are opened during depolarization causing an AP
The depolarization wave causes the sacroplasmic reticulum to release Ca2+ ions which cause the myofilaments to sliding across themselves (actin and tropin)
The time that Ca2+ channels stays open helps to explain why the AP and contractile phase is so much longer in cardiac muscle than in skeletal muscle. This helps in the heart ejecting blood from its chambers.
Ischemic – when the heart is deprived of blood, the cells are starving for oxygen and begin to metabolize anaerobically making lactic acid. The rise in H+ hinders the cardiac cells ability to produce ATP which is needed for Ca2+ channel pumps to open into extracellular fluid. When you have an increase in H+ and Ca2+ levels, the gap junctions will close, bypassing the damaged cells and forcing AP to go elsewhere…heart attack.
Independent but coordinated activity of the heart is a function of:
1) presence of gap junctions
2) intrinsic cardiac conduction system –initiates and distributes impulses throughout the heart so that it beats in a coordinated fashion
(There is a section on autorythmic cells and AP on page 690 that is rather detailed that you might want to look at)
Autorythmic cells are found in the following:
1) SA node – pacemaker
2) AV node – above tricuspid valve
3) Bundle of HIS
4) Left and right bundle branches
5) Perkinje fibers which supply the papillary muscles and are more prominent on the left side of the heart
The cardiac centers are located in the medulla oblongata
EKG or ECG is a composite of all AP generated by nodal and contractile cells
Deflection waves are the following:
1) P wave – lasts about 0.08 sec and results from the depolarization wave from the SA node to the atria
2) QRS complex – results from ventricular depolarization and precedes ventricular contraction.
3) T wave is caused by ventricular repolarization and last 0.16 sec
Heart murmurs are do to thin heart walls, defective values.
Systole – contraction period
Diastole-relaxation period
Cardiac output – amount of blood pumped out by each ventricle per minute (70 ml x number of beats per minute (75, 72 )
Stroke volume is the volume of blood pumped out of heart per minute (70 ml)Starling Law of the Heart – check handout
Tachycardia – fast heartbeat
Bradycardia – slow heartbeat
If the left side of the heart fails – pulmonary congestion occurs-edema in lungs
If the right side of the heart fails, peripheral congestion-edema in body, most noticeable the ankles, feet and hands
