overview: cardiovascular system and the heart circulatory system = heart, bvs, and blood...
TRANSCRIPT
Overview: Cardiovascular System and the Heart
Circulatory System = heart, BVs, and blood
Cardiovascular System = passageways for blood = heart, arteries veins, etc.
Two Hearts:1. Pulmonary Circuit
(right side) - takes blood to lungs for gas exchange
2. Systemic circuit (left side)- takes oxygen rich blood to the organs and oxygen poor blood back to the heart
• Right side of heart gets O2 poor blood– Pulmonary artery takes it
away from heart to lungs– Pulmonary veins bring it
back O2 rich
• Left side of heart serves systemic system– Aorta takes O2 rich blood out
to organs– Superior vena cava brings it
back from head, neck, upper limbs
– Inferior vena cava brings it back from organs below diaphragm.
Pericardium
• Double walled sac enclosing heart
• In the pericardial cavity is pericardial fluid that allows the heart to beat without friction
• Pericarditis is the pain caused by friction when the membranes are dry
Heart wall• Epicardium
– outer layer– fatty
• Myocardium– thickest layer– cardiac muscle
that pulls against a fibrous skeleton of fibers
– focuses the movement of electricity
• Endocardium– Smooth inner
lining
Chambers
• Right and left atria receive returning blood– have an easier
workload
• Right and left ventricles eject blood
Heart Valves• Ensure one way flow
• Made of flaps called cusps
• Open & close as a result of pressure changes
• When ventricles relax, valves are open
• Full ventricles contract pressure pushes valves shut
AV valves = between atria + ventriclesRight AV – tricuspid valveLeft AV – bicuspid valve (aka, mitral valve)
Semilunar valves = bet. ventricles + the great arteries
Coronary Circulation
• Getting blood to your heart• ~3 billion beats over an 80
year life span• Heart needs 5% of body’s O2
– delivered by coronary arteries
• Myocardial Infarction: fat deposits blocking arteries leading to necrosis of tissue– Anastomoses: our body’s defense
• Two arteries covering the same area
• If the damage is extensive, theheart beat becomes inefficient- coronary bypass may be necesssary
Cardiac Muscle and The Cardiac Conduction System
• Cardiocytes: short, thick branched cells-mononucleated, striated-myogenic –will beat rythmically w/o CNS stimulation-inherent contractile activity controlled by the ANS
• Intercalated discs join cells
end to end– Gap junctions allow ions to flow
between cells, keep electrical current flowing from one cell to the next
– The action potential travels thru all cells connected together forming a functional syncytium
Cardiac conduction system
• Our brain can modify the heartbeat, but not create it. Disembodied hearts can beat for hours.
• Sinoatrial (SA) node = the pacemaker-initiates heart beat and determines heart rate-damage to SA node results in slower heart rate – implant an artificial pacemaker
• Atrioventricular node = sends signals to the ventricles
Purkinje fibers arise from bundle branches near the apex and then spread throughout the myocardium.
Control of Heart Rate• Without nervous system control, the heart would
beat about 100 times per minute• Both sympathetic and parasympathetic nerves
innervate the SA node• When you are relaxed, your parasympathetic
nervous system (via the vagus nerve) sets a resting heart beat rate at about 70 beats/min
• When exercising or anxious, the sympathetic nervous system ↑ heart beat via hormones like adrenaline – this ↑ flow of O2 blood to muscles
• Average maximum heart rate is 220 minus your age
Electrical & Contractile Activity
Contraction = systoleRelaxation = diastole
These can apply to parts (e.g., atrial systole), or just to the ventricles
Sinus rhythm = normal beat triggered by SA nodeCan have ectopic focus (alternate source of beat, instead of SA node) called nodal rhythm
Arrhythmia = abnormal rhythm
Physiology of the SA node
• The nerves of the SA node are always slowly moving toward an action potential
• As soon as the heart beats it’s already starting toward another beat
• Avg. ~75 beats per minute
• Cardiac muscle has a sustained contraction, and a longer refractory period– This prevents tetanus:
continual contraction
Membrane potential starts around -60mV.Pacemaker potential is a gradual driftupward (slow inflow of Na+ w/o outflow of K+).Fast calcium channels – inflow of Ca+.
Electrocardiogram (ECG/EKG)
• Composite reading of many action potentials
• P wave: atria contract
• QRS complex: AV node fires, ventricles start to contract
• T wave: ventricles repolarizing
• U wave: not always seen – repolarization of papillary muscles or Perkinje fibers
Electrocardiogram
Cardiac cycle
“Lub-dub” sounds are made when the heart valves thatseparate the chambers of the heart open and close in sequence.
Now, you can…
• Identify the chambers and valves of the heart
• Trace the flow of blood through the heart chambers
• Contrast cardiac vs. skeletal muscle• Describe the physiological properties of
cardiac muscle• Describe the heart’s electrical conduction
system• Describe the physiological mechanism of
control of rate of heart beat