Ch. 4 Cardiovascular Function Flashcards
what are the functions of the cardiovascular system?
deliver vital oxygen and nutrients to the cells, removes waste products, and transports hormones
how does the lymphatic system assist in maintaining homeostasis?
by returning excess fluid from the body’s tissues back to the circulatory system as well as by playing a vital role in the immune system
how does the pericardium protect the heart?
protects it against trauma from surrounding structures, invasions of foreign bodies, and friction from the constant movement. it also provides support in terms of anchoring the heart and prevents over distention
automaticity
process by which cardiac cells are able to generate an impulse to contract even with no external nerve stimulus
the SA node automatically generates impulses at what rate?
60-100 bpm
the AV node is able to initiate impulses at what rate?
40-60 bpm
what can happen if the impulses fail to fire at the SA or AV nodes?
the ventricles will attempt to pace themselves, but can only generate impulses around 20-40 bpm, which may not result in adequate cardiac output because the ventricles may not have a chance to fill completely before they contract
what does the P wave on an EKG represent?
atrial contraction or depolarization
on an EKG what does the QRS complex represent?
ventricular contraction or depolarization. atrial reploarization occurs here, but we don’t see it because it is masked by the ventricular depolarization
what does a more intense contraction do to the EKG?
it creates a higher wave or complex
what does the T wave represent on an EKG?
ventricular repolarization or relaxation
abnormal variations in the EKG
arrhythmias or dysrhythmias
what ions do the cardiac muscle cells need in order to work? why?
Na, K, and Ca. need Na and K for the sodium-potassium pumps that will initiate and conduct electrical signals. need Ca for muscle contractility. need Na for the neurologic system which controls the cardiac function
how does the nervous system function in the contractility of the heart?
rate of contraction (chronotropic effect), rate of electrical conduction (dromotropic effect), and strength of the contraction (inotropic effect)
detect chemical changes in the blood
chemoreceptors
located in the carotid artery. detect the pressure in the heart and arteries
baroreceptors
what will stimulating the SNS do to the heart rate and blood pressure? what about the parasympathetic nervous system?
SNS will increase heart rate and blood pressure, parasympathetic will decrease heart rate and blood pressure
what is pulse pressure?
the difference between the systolic and diastolic pressures and represents the force that the heart generates each time it contracts
what two things significantly affect blood pressure? what is the equation?
cardiac output and peripheral vascular resistance
BP=CO x PVR
the force opposing blood in the peripheral circulation. it increases as the diameter of the blood vessel decreases. stimulation of the SNS can initiate systemic vasoconstriction to raise blood pressure
peripheral vascular resistance
how does the afterload affect the heart?
the higher the afterload, the harder it is for the heart to eject blood, thus lowering the stroke volume
how is the stroke volume affected by preload?
the amount of blood returning to the heart that the heart must then manage
what happens as afterload and preload increase?
blood pressure increases
how does antidiuretic hormone affect blood pressure and volume?
it increases water reabsorption in the kidney, so increases the blood volume and pressure. additionally it is a vasoconstrictor which increases the PVR, which also increases blood pressure
how does aldosterone affect blood volume and pressure?
it increases blood volume by increasing the reabsorption of Na in the kidneys which attracts water. increasing renal water reabsorption will increase blood volume and pressure
how does the renin-angiotensin-aldosterone system affect the heart?
becomes activated when renal blood flow decreases. stimulates aldosterone secretion. in hypotensive states, this mechanism raises blood pressure and maintains the blood supply to vital organs