Cardiovascular physiology Flashcards
What is the very general pathway of blood in the heart?
-deox blood enters right atrium -> pushed into right ventricle -> pumped up to semilunar valve -> out to lungs to get oxygenated -> ox blood comes back to heart -> enters left atrium -> left ventricle -> up into aorta -> out to three places
What does the thickness of the ventricles have to do with their function?
-right ventricle has thin muscle because only has to pump to pulmonary valve
-left ventricle has thick muscle because has to pump to brain and rest of body = more important
The aorta has three branches, where do they go?
-upper body
-lower body
-supply for the heart itself
What is the number one priority of the heart?
-pump blood to the brain
What is flow velocity?
rate/C-S area of vessel
What three things affect resistance of flow?
-vessel diameter
-blood viscocity
-tube length
Does flow depend on absolute pressure?
-no, depends on pressure difference
Which factor of resistance can be changed through drugs and influence blood flow?
-vessel diameter
-viscocity??
What are the two main factors of blood flow?
-Pressure gradient
-Resistance
What are the two muscle types in the heart?
-skeletal = striated
-cardiac muscle
What are the characteristics of skeletal heart muscle?
-striations of fibers are parallel
-stimulated by somatic NS
-can only contract in one direction
-voluntary
What are some characteristics of cardiac muscle?
-fibers are branched
-pumps blood to heart
-stimulated by autonomic NS
-involuntary
What are the two types of muscle cells?
-myocardial autorhythmic cells
-myocardial contractile cells
What are myocardial autorhythmic cells?
-“pacemakers”
-generates electricity
-doesn’t contract
-never rest
What are myocardial contractile cells?
-contracts
-only 1% are self-excitable
-gap junctions = faster signals = heart contracts as one unit
-long refractory period = 250ms
What are the general features of cardiac cells?
-intercalated discs = branching
-gap junctions = fast signal relay
-many mito
-large T tubes
What is the intrinsic cardiac conduction system?
-network of noncontractile cells (autorhythmic) that initiate and distribute impulses to coordinate depolarization and contractions
What does the potential of an autorhythmic cell look like?
Pacemaker potential = slowly opening Na+ channels = unstable resting potential -> at threshold -> Ca2+ channels open -> Ca2+ influx = rising phase of AP = depolarization -> Ca2+ channels inactivated and K+ channels open -> repolarization -> charge falls
-never a flat line because it never rests
What is the charge of the cell naturally?
-70 mV
What is the threshold for action potential?
-40 mV
What is the pathway for the action potential of contractile cells?
depolarization opens Na+ channels in sarcolemma -> -90mV to +30mV -> depolarization in T tubules -> SR release Ca2+ -> also opens Ca2+ channels in sarcolemma -> Ca2+ surge = long depolarization = plateau -> repolarization from inactivating Ca2+ channels and opening K+ channels -> back to resting potential
What does the action potential for cardiac contractile muscle look like from a cellular view?
action potential enters -> voltage gates Ca2+ channels open -> Ca2+ enters cell -> Ca induced Ca release at ryanodine receptor -> Ca released from SR -> calcium spark -> Ca signal -> Ca binds to troponin -> contraction -> Ca unbinds -> relaxation -> Ca pumped into SR to store -> Ca exchange with Na -> Na gradient mediated by Na-K ATPase
What is Frank-Stirling Law?
-increase in end-diastolic ventricular volume produces increase in stroke volume
-force of heart muscle varies with wall fiber tension, which is function of length
-basically = more dilation of the left ventricle = increased ejection
-more SA of actin covering myosin = more contraction
pathway for regulation of monocyte action through adrenergic system
What signals control contraction?
-norepinephrine
-epinephrine
What is the relationship between contractions and crossbridges?
-graded contraction is proportional to crossbridges formed
-more Ca = crossbridges = more force/speed
What nerve connects to the SA and AV node?
-The vagus nerves
Where on the heart do the sympathetic nerve chain connect?
-only connects to contractile cells
-doesn’t connect to AV and SA node
What factors affect arterial blood pressure?
-cardiac output
-heart rate
- contractility
-filling pressure
- blood volume
venous tone
-peripheral resistance
-arteriolar tone
When you stand up from lying down, what is the pathway for maintaining blood pressure?
lying down -> stand up -> decrease in venous return -> decrease in end-diastolic volume -> decrease stroke volume -> decrease cardiac output -> decrease BP (stimuli) -> baroreceptors -> sensory neurons -> medulla obl. -> increase sympathetic and decrease parasympathetic = vasoconstriction, increase HR, increase peripheral resistance -> increase in blood pressure (-ve feedback response)
What are the Purkinje fibers?
-branch of cells in the ventricles
-allow the heart to have synchronized contractions
What is the bundle of His?
-the AV bundle
-sends electrical impulses from AV node to Purkinje fibers
In what order of structures does the electrical current flow?
-SA node -> pumps atria -> AV node -> AV bundle -> purkinje fibres -> pump ventricles
what is the cardiac cycle?
-coordinates sequence of events as blood enters atria, leaves ventricles and starts over
-synchronizing via Intrinsic electrical conduction system
-rate influenced by symp and parasymp division of ANS
What are the 6 stages of the cardiac cycle?
- Late diastole: full of blood
- atrial systole: makes sure all blood is in heart; top contraction
- isometric ventricular contraction (lub): no movement; pressure built; no backflow; atria go to diastole
- Ventricular ejection: ventricles contract; semilunar valves open
- isometric ventricular relaxation (dub): last bit of blood leaves ventricles; no more contraction; AV valves still closed
- diastole: heart fills with blood from atria to ventricles; due to low pressure
What is the electrical conduction pathway of the heart?
-SA node initiates -> depol spreads through atria via gap junctions and internodal paths -> to AV node ->fibrous tissue slows formation of APs -> AP travel down Bundle of His -> split to L and R atrioventricular bundles -> into purkinje cells
What is systole?
period of contraction
What is diastole?
period of relaxation
Why does increased pressure in the ventricles cause the AV valves to close?
**
What is the sympathetic nervous system activated by?
-emotional or physical stressors
-ex. norepinphrine = more rapid pacemaker
What is the vagal tone?
-the heart at rest
-parasympathetic
Which NS system does parasympathetic oppose?
-sympathetic
-involves acetylcholine
What is the Bainbridge?
-aka atrial reflex
-sympathetic reflex initiated by increased venous return
-SA node stim by stretch of atrial walls
-same law as Frank Sterling but for atria
What are the two main chemical regulations of heart rate?
1: hormones
-epinephrine = increased HR and contractility
-thyroxine = increases HR and effects of epinephrine
2: intra/extracellular ion [ ] maintenance
What are other factors of heart rate?
-age
-gender
-exercise
-body temperature
What occurs with age that can increase the effects on the heart?
-sclerosis and thickening of valve flaps
-decline in cardiac reserve
-fibrosis of cardiac muscle
-atherosclerosis
What are three possible congenital heart defects?
- ventricular septal defect: no septum separating ventricles = blood mixes; more blood in right
- coarctation of the aorta: narrow aorta = increases workload of left ventricle
- tetralogy of Fallot: four defects = narrow pulmonary trunk; hypertrophied R ventricle; ventricular septal defect; aorta opens from both ventricles
What is an arrhythmia?
-most common disorder
-includes atrial fibrillation and flutter
-related to age and or heart disease
What are the symptoms of arrhythmias?
-palpitation or fluttering sensation
-racing heart
-dyspnea
-syncope (fainting)
-fatigue
-chest pain
-cardiac arrest
What can cause arrhythmias?
-coronary artery disease (ischemia or infarction)
-altered impulse conduction
-changes in cardiac structure from heart failure
-drugs
-electrolyte distrubances
Why is coronary artery disease a common cause of arrhythmia?
-because it causes ischemia or infarction
-if cardiac cells lack O2, they depolarize = altered impulse formation and conduction
-this causes changes in automaticity
What are Ectopic Foci?
-ectopic foci = abnormal pacemaker sites outside of SA node with automaticity
-occur in atria or ventricles
-create additional beats
-can lead to tachycardia and bradycardia
-can occur after reentry too
What is Wolfe Parkinson White Syndrome? (on exam)
-cause of supraventricular tachycardia in children
-extra conducting tissue = accessory pathway
-sometimes can conduct electricity and establish a circuit with AV node
What is an AV block?
- conduction block within the AV node or bundle of His
-impairs impulse conductions from atria to ventricles
What are 5 types of supraventricular arrhythmias?
-Sinus tachycardia
-atrial tachycardia
-paroxysmal atrial tachycardia
-atrial flutter
-atrial fibrillation
What is sinus tachycardia?
-high sinus rate
-100-180 beats/min
-during exercise or from conditions that lead to increased SA nodal firing rate
What is atrial tachycardia?
-series of 3+ consecutive atrial premature beats at over 100/min
What is paroxysmal atrial tachycardia?
-tachycardia begins and ends in acute manner
What is atrial flutter?
sinus rate of 250-350 bpm
What is atrial fibrillation?
-uncoordinated atrial depolarizations
What are 4 ventricular arrhythmias?
-ventricular premature beats: from ectopic ventricular foci
-ventricular tachycardia: from abnormality or reentry; 100-200 bpm; life threatenening
-ventricular flutter: over 200 depol/min
-ventricular fibrillation: uncoordinated depol
When do the two heart sounds occur?
isometric ventricular contraction = lub
isometric ventricular relaxation = dub
