Physiology Ch. 13 Con.

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Pulmonary Circulation

Path of blood from right ventricle through the lungs and back to the heart
Systemic Circulation

Oxygen-rich blood pumped to all organ systems to supplu nutrients
Pulmonary and Systemic Circulations

Rate of blood flow through systemic circulation = flow rate through pulmonary circulation
Main structures of the heart
- 4 chambers: 2 atrial/ 2 ventricles (left/right)
- 2 AV valves: tricuspid (right)/ bicuspid (mitral) (left)
- 2 semilunar valves: Pulmonary (between right ventricle - pulmonary artery) Aortic (between left ventricle - aorta)
Atrioventricular and Semilunar Valves
- One way valves
- Opening and closing of valves occur as a result of pressure differences
Atria and ventricles are separated in 2 functional units by AV valves(connective tissue) they allow blood flow from____ into the____.

Atria, ventricles
At the origin of pulmonary artery and aorta are_______. They open during_____contraction.

semilunar valves, ventricular
Cardiac Cycle and blood volume

Refers to the repeating pattern of contraction and relaxation of the heart
Systole: (ventricle contraction)

phase of contraction
Diastole:

phase of relaxation
End-diastolic volume (EDV)
- Total volume of blood in the ventricles at the end of diastole
- How much blood are in ventricles
Stroke Volume (SV)
- Amount of blood ejected from ventricles during systole
- How much blood pumped out
End systolic volume (ESV)
- Amount of blood left in the ventricles at the end of systole
- EDV - SV= ESV
Steps of Cardiac cycle (6 steps)
- Step 1: Isovolumetric contraction
- Step 2: Ejection
- Step 3: Ventricle pressure drops below aortic pressure
- Step 4: Isovolumetric relaxation
- Step 5: Rapid filling of ventricles
- Step 6: Atrial systole----> then cycle repeats back to step 1
Steps of Cardiac cycle
Step 1: Isovolumetric contraction
- Contraction of the ventricle causes ventricular pressure to rise above atrial pressure. AV valves close
- Ventricular pressure is less than aortic pressure. Semilunar valves are closed. Volume of blood in ventricle is EDV
Steps of Cardiac cycle
Step 2: Ejection
- Contraction of the ventricle causes ventricle pressure to rise above aortic pressure. Semiluar valves open.
- Ventricular pressure is greater than atrial pressure. AV valves are closed. Volume of blood ejected: SV
Steps of Cardiac cycle
Step 3

Ventricular pressure drops below aortic pressure
Steps of Cardiac cycle
Step 4: Isovolumetric relaxation
- Back pressure causes semilunar valves to close
- AV valves are still closed
- Volume of blood in the ventricle: ESV
Steps of Cardiac cycle
Step 5: Rapid filling of ventricles
- Ventricular pressure decrease below atrial pressure
- AV valves open
- Rapid ventricular filling occurs
Steps of Cardiac cycle
Step 6: Atrial systole
- Atrial contraction
- Push 10-30% more blood into the ventricle
- Then cycle repeats
Heart Sounds

Caused by the closing of the AV and semilunar valves
Lub (first sound)

Produced by closing of the AV valves during isovolumetric contraction.
Dub (second sound)

Produced by closing of the semilunar valves when pressure in te ventricles falls below pressure in the arteries
Heart Murmurs

Abnormal heart sounds produced by abnormal patterns of blood flow in the heart
Heart Murmurs
Defective heart valves

Valves become damaged by antibodies made in response to an infection, or congenital defects
Heart Murmurs
Mitral Stenosis(Bicuspid)
- Mitral valve becomes thickened and calcified
- Impairs blood flow from left atrium to left ventricle
- Accumulation of blood in left ventricle may cause pulmonary hypertension
Heart Murmurs
Incompetent valves
- Damage to papillary muscles
- Valves do not close properly
- Murmurs produced as blood regurgitates through valve flaps
Heart Murmurs
Septal defects
- Usually congenital
- Holes in septum between the left and right sides of the heart
- May occur either in interatrial or interventricular septum
- Blood passes from left side of the heart to the right side of the heart through the septal holes
Systemic Circulation
- When oxygen-rich blood pumped to all organ systems to supply nutrients it travels through.
- The role is to direct the flow of blood from the heart to the capillaries, and back to the heart
- Heart>Arteries>Arterioles>Capillaries>Venules>Veins>Heart
Blood vessels composed of 3 tunics:
- Tunica externa
- Tunica media
- Tunica interna
Tunica externa

Outer layer comprised of connective tissue
Tunica media

Middle layer composed of smooth muscle
Tunica interna

Innermost layer has elastin
Elastic arteries
- Numerous layers of elastin fibers between smooth muscle
- Expand when the pressure of the blood rises
- Act as recoil system when ventricles relax
Muscular arteries
- Are less elastic and have a thicker layer of smooth muscle
- Diameter changes slightly as BP raises and falls
Arterioles
- Contain highest % of smooth muscle
- Greatest pressure drop
- Greatest resistance to flow
Most of the blood volume is contained in the____

venous system
Venules
- Formed when capillaries unite
- Very porous
Veins
- Contain little smooth muscle or elastin
- Contain 1 way valves that ensure blood flow to the heart
Capillaries
- Smallest blood vessels
- 1 endothelial cell thick
- Provide direct access to cells
- Permits exchange of nutrients and wastes
Ischemic Heart Disease
- Ischemia: Oxygen supply to heart tissue if deficient
- Most common cause is atherosclerosis of coronary arteries (Heart muscle, several of them)
- Increased lactic acid produced by anaerobic respiration
- Angina pectoris: Substernal pain....can lead to--->Myocardial infarction (MI)
- **Cardiac muscle cannot repair itself
Electrical Activity of the Heart
SA node:
- Demonstrates automaticity
- Functions as the pacemaker
- Spontaneous depolarization (pacemakeer potential)
- SA node spreads APs to myocardial cells
When myocardial cell reaches threshold, cells depolarize
Rapid depolarization occurs:
- VG Na+ channels open
- Inward diffusion of Na+
Rapid repolarization:
- VG K+ channels open
- Rapid outward diffusion of K+
Conducting tissues of the Heart
APs spread through myocardial cells through____

gap junctions
Conducting Tissues of the Heart
Impulses cannot spread to ventricles directly because of______

Fibrous tissue
Conduction pathway:
- SA node--> AV node--> Bundle of his--> Purkinje fibers
- Stimulation of purkinje fibers cause both ventricles to contract simutaneously
Conduction of Impulse
- APs from SA node spread quickly
- Time delay occurs as impulses pass through AV node
- Impulse conduction increases as spread to purkinje fibers
- Ventricular contraction begins 0.1-.0.2 sec after contraction of the atria
Refractory Periods
- Heart contracts as syncytium (ie contracts together)
- Contraction lasts almost 300 msec
- Refractory periods last almost as long as a contraction
- Myocardial muscle cannot be stimulated to contract again until it has relaxed. Summation cannot occur
Electrocardiogram (ECG/EKG)
- The body is a good conductor of electricity
- Tissue fluids have a high concentration of ions that move in response to potential differences.
- Measure of the electrical activity of the heart per unit time.
- Potential differences generated by heart are conducted to body surface where they can be recorded on electrodes on the skin
- Does not measure the flow of blood through the heart
EKG Waves
P wave

Atrial depolarization
EKG Waves
QRS complex
- Ventricular depolarization
- Atrial repolarization (hidden)
EKG Waves
T wave

Ventricular repolarization
Correlation of EKG with Heart Sounds
First Heart sound:
- Produced immediately after QRS wave
- Rise of intraventricular pressure causes AV valves to close
Correlation of EKG with Heart Sounds
Second Heart sound:
- Produced after T wave begins
- Fall in intraventricular pressure causes semilunar valves to close
Arrhythmias

Abnormal heart rhythms
Flutter
- Extremely rapid rates of excitation and contraction of atria or ventricles.
- Atrial flutter degenerates into atrial fibrillation
Fibrillation
- Contractions of different groups of myocardial cells at different times
- Coordination of pumping impossible
- Ventricular fibrillation is life threathening
- Can cause blood clots
Bradycardia

HR slower < 60 beats/ min
Tachycardia

HR > 100 beats/min

Author

rleighn25

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Card Set

Physiology Ch. 13 Con.

Description

Continued Pulmonary and Systemic Circulations

Updated

2011-09-29T19:28:41Z

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