circulatory and respiratory system Flashcards
cycle of blood flow
blood is pumped into the aorta which branches into a series of srteries
the arteries branch into arterioles and then into micrscopic capillaries
exchange of gases, nutrients, and cellular waste occurs via diffusion across capillary walls
the capillaries than converge into venules and eventually into veins, which carry deoxygentated blood backtoward the heart
from the heart the deoxygentated blood returns to the heart to be pumped throughout the body once more
aorta
the main artery of the body, supplying oxygenated blood to the circulatory system. In humans it passes over the heart from the left ventricle and runs down in front of the backbone.
superior vena cava
large vein carrying deoxygenated blood into the heart
carrying blood from upper body, head, arms
inferior vena cava
a large vein carrying deoxygenated blood into the heart.
carries blood from the lower body
heart structure
driving force of circulatory system
its right and left valves can be viewed as 2 separate pumps- right side of the heart pumps deoxygenated blood into pulmonary circulation (toward lungs)
left side pumps oxygentated blood into systemic circulation (throughout body)
has 2 upper chambers called atria
2 lower chambers called ventricles
atria are thin walled
ventricles are muscular
ventricls
lower chambers of the heart
are muscular
left ventricle is more muscular than right because it is responsible for generating the force that propels systemic circulation and because it pumps against higher resistance
in patients with increased systemic resistance, the left ventricle can become hypertrophied (enlarged) which over time can lead to congestive heart failure and other caridovascular diseases
atria
upper chambers of the heart
thin-walled
blood retunring from the body first flows through the right atrium anf then through the tricuspid valve into the right ventricle, and finally through the pulmonary semilunar valve into the pulomnary arteries to continue to the lung
blood flow returning from lungs
blood returning from the lungs flows through the pulomnary veins into the left atrium, then through the mitral valve into the left ventricle, and finally out through the aortic semilumar valve into the systemic circulation
atrioventricular valves
located between the atria and ventricles on both sides of the heart
prevent backflow of blood into the atria
tricuspid valve
valve on right side of heart, has 3 cusps
mitral valve
valve on left side of heart, has 2 cusps
semilunar valves
have 3 cusps and are located between the left ventricle and the aorta, and betwen the right ventricle and the pulmonary arter
sound of heartbeat
made by successive closing of the atrioventricular and semilunar valves
heart’s pumping cycle
made of 2 alternating phases- systole, and diastole, which make up the heartbeat together
systole
period during whci the ventricles contract forcing blood out of the heart into the pulmonary and systemic circulation
diastole
period of cardiac muscle relaxation during which blood drains into all 4 chabers
reflected in measurements such as blood pressure
systolic blood pressure
measures the pressure in a patient’s blood vessels when the ventricles are contracting
diastolic blood pressure
measures the pressure during caridac relaxation
cardiac output
defined as the total volume of blood the left ventrcle pumps out per minute
cardiac output= heart rate (number beats per minute) x stroke volume (volume of blood pumped out of the left ventricle per contraction)
control of heart rate
cardiac muscle contracts rhythmically without stimulation from the nervous system, producing impulses that spread through its internal conducting system
SA is the pacemaker
an ordinary cardiac contraction originates in and is regulated by the SA node
a small mass of specialized tissue located in the wall of the right atrium
spreads impulses through both atria, stimulating them to contract simultaneously
the impulse arrives at the atrioventricular node (AV) which conducts impulses to the rest of the heart, allowing enough time for atrial contraction and for the ventricles to fill with blood
the impulse is then carried by the bundle of His (AV bundle) which branches into the right and left bundle branches, and finally through the Purkinje fibers in the alls of both ventricles, stimulating a strong contraction
this contraction forces blood out of the heart and into circulation
how does the autonomic nervous system affect heart contraction
modifies it
the parasympathetic nervous system innervates the heart via the vegus nerve and causes a decrease in heart rate
the sympathetic nervous system innervates th heart via the cervical and upper thoracic ganglia anf causes an increase in heart rate
the adrenal medulla exerts hormonal contraol via epinephrine (adrenaline) secretion which causes an increase in heart rate