Cardiovascular Review Flashcards
What does the Systolic Blood Pressure Estimate?
- Work of Heart
- Force Blood exerts against arterial walls during systole
What does Diastolic Blood Pressure indicated?
- Peripheral resistance
- Ease blood flows from arterioles in capillaries
When does Diastolic Blood Pressure occur?
- Relaxation phase of cardiac cycle
What is the mean arterial pressure?
- average force exerted by blood against wall during cardiac cycle
Describe structure of veins
- Smooth Muscle Layer
- One-way valves prevent back-flow of blood
Describe structure of arteries
- Walls contain elastic fibers/muscle fibers
- Smooth muscle layer
In Arteries, what controls blood flow to capillary beds?
- Smooth muscle fibers
Describe function of capillaries
- Blood pressure forces fluid from capillary
- Osmotic pressure within capillaries draws fluid back in
How is resistance proportional to the radius of a vessel?
- Inversely proportional to fourth power
- R = flow resistence
- R = r (radius)
- 16R = 1/2 r
What controls the diameter of a capillary?
- Precapillary sphincter
- ring smooth muscle
- encircles the capillary at origin
What provides a means for blood flow regulation within a specific tissue?
- Sphincter constriction
- Sphincter relaxation
What two factors trigger precapillary sphincter relaxation to open more capillaries?
- Driving force of increased local BP plus intrinsic neural control
- Local metabolites produced in exercise
What do capillaries feed into small veins or venules?
- Deoxygenated blood
What do veins in the lower body eventually empty into?
- Inferior Vena Cava
What is the body’s largest vein?
- Inferior Vena Cava
Where does the Vena Cave return blood to?
- Right atrium
Where does the Inferior Vena Cave return blood from?
- Abdomen
- Pelvis
- Lower Extremities
Where does blood from vessels in the head, neck, shoulders, thorax and abdominal wall flow into?
- Superior Vena Cava
Where do the superior and inferior vena cava’s join?
- The Heart
What enters the Right Atrium?
- Mixed-venous blood
What prevents blood from flowing in 2 directs in veins?
- One-way Valves
How does blood travel in veins against gravity?
- One-way valve
- Small muscular contractions
- pressure changes in thoracic cavity with breathing
- Milking propels blood back to heart
What would happen if their were no valves in veins?
- Blood would stagnate in extremities
- People would faint when standing
- Reduced venous return
- Diminished cerbral blood flow
How is blood pressure within different portions of the arterial system determined?
- Relates to total area in the section
- Resistance
What reduces total peripheral resistance during rhythmic muscle activity? Why?
What
- Vasodilation in active muscles
Why
- Enhance blood flow through peripheral vasculature
What propels blood through the vascular circuit back to the heart?
- Alternate muscle contraction/relaxation
What does increasing blood flow during steady-rate exercise rapidly do? when does it happen?
- Increases systolic blood pressure
- First few minutes
What happens to Systolic Blood Pressure as steady-rate exercise continues? Why?
What
- Declines
Why
- Arterioles in active muscles continue to dilate reducing peripheral resistance
What happens to diastolic bllod pressure during steady-rate exercise?
- Remains relatively unchanged
How does systolic blood pressure change with increasing exercise intensity?
After initial rapid rise from resting
- Increases linearly wiht intensity
What happens to diastolic blood pressure with increasing exercise intensity?
- Remains stable
- or Decreases slightly at higher levels
How high might systolic blood pressure increase in healthy individuals during maximum exercise? why?
How high:
- 200mm Hg
Why:
- Likely due to large cardiac output
What type of exercise produces higher SBP and DBP at a given VO2max, leg or arm exercise? Why?
What
- Arm
Why
-smaller arm muscle mass/vasculature offer greater resistance to blood flow
What happens following a single bout of submaximal exercise for normotensive and hypertensive individuals?
- BP temporarily falls below pre-exercise levels
- Likely due to unexplained peripheral vasodilation
How long can the hypotensive response to exercise last?
- 12 Hrs
How much O2 does the myocardium extract in the coronary vessels?
- 70-80%
What is the sole mechanism for increasing myocardial O2 supply during exercise?
- Increase coronary blood flow
What two factors increase myocardial blood flow?
- Elevated myocardial metabolism dilates coronary vessels
- Increased aortic pressure during exercise forces a proportionately greater volume of blood into coronary circulation
What does RPP stand for?
- Rate-Pressure Product
What is Rate-Pressure Product?
- Estimate of myocardial workload and VO2
How is the RPP computed?
- from product of peak SBP measured at brachial artery and HR
What is the Equation for RPP?
RPP = SBP x HR
What is the Rate-Pressure Product an index of? explain it
What
- Relative Cardiac Work
Explain
- Relates closely to directly measured myocardial VO2 and coronary blood flow in healthy subjects over a wide range of exercise intensities
What does RPP range from? what does it depend on?
- 6000 at rest
- > 40000 during exercise
- Depends on intensity/mode
What does cardiac muscle do that other tissue does not?
- Has its own rhythm
At what rate would the heart beat at if left to its own inherent rhythmicity?
100b/min
What is the sinoatrial (SA) node’s purpose?
Heart’s Pacemaker
- provides Innate stimulus of heat action
What accelerates the heart in anticipation before exercise?
- Nerves that directly supply myocardium
- chemical “messangers” that circulate in blood
What adjusts to the intensity of physical effort for heart rate?
- Nerves that directly supply myocardium
- Chemical “messengers” in blood
Where is the cardiovascular control center?
- Ventrolateral medulla
What regulates the heart’s output of blood and blood’s preferential distribution to all body’s tissues?
- Input from the brain and peripheral nervous system bombard cardiovascular control center in ventrolateral medulla
What are the neural mechanisms for cardiovascular regulation before and during activity?
- Higher brain areas (central command) input to ventrolateral medulla
What are the receptors to ventrolateral medulla?
- Aortic and Carotid Arterial Mechano-receptors
- Cardiac Mechano-receptors
- Skeletal Muscle Ergoreceptors
What do aortic and carotid arterial mechano-receptors read?
- arterial baroreflexes
What do cardiac mechanoreceptors read?
- Cardiopulmonary reflexes
What do skeletal muscle ergoreceptors read?
- Exercise pressor reflex
What are the functions of ventrolateral medulla?
Cardiovascular Center
- Heart chronotropic, inotropic function
- Active Skeletal Muscle: Modulation of vasomotor tune
- Inactive Skeletal Muscle: Muscle Vasoconstriction
- Kidney and Splenic Bed Vasoconstriction
What does muscle vasoconstriction of inactive skeletal muscle by the ventrolateral medulla do?
- Maintain central blood volume/pressure
What does neural influence do to myocardium’s inherent rhythm?
- Overrides it
Where does neural input originate from and what does it flow through?
From
- Cardiovascular Center
Through
- Sympathetic/Parasympathetic components of autonomic nervous system
What innervates the atria from the cardiovascular center?
- Sympathetic and Parasympathetic neurons
What innervates the ventricles from the cardiovascular center?
- Almost exclusively sympathetic fibers
Where do Parasympathetic nerve endings concentrate in the heart?
- Atria, including SA and Av nodes
Where do sympathetic nerve endings concentrate in the heart?
- SA and AV node
- Muscle of atria
- Ventricles
What does stimulation of sympathetic cardioaccelerator nerves release?
- Epinephrine
- Norepinephrine
What does the release of epinephrine and norepinephrine from the stimulation of sympathetic cardioaccelerator nerves do?
- Causes chronotropic and inotropic effects on heart
What is the chronotropic effect on the heart?
- SA node Depolarization
- Increase HR
What is the Inotropic effect on the heart?
- Increased myocardial contractility
Where does sympathetic stimulationg produce vasoconstriction?
- Generalized
- Except coronary arteries
Why does sympathetic stimulation cause generalized vasoconstriction?
- ## Norepinephrin, released by adrenergic fibers, acts as vasoconstrictor
What does Adrenergic mean?
- Epinephrin/norepinephrin neurotransmitter
Why does dilation of blood vessels under adrenergic influences occur?
- Decreased adrenergic activity
What do parasympathetic neurons release?
- Acetylcholine
What does the release of acetylcholine from parasympathetic neurons do in the heart?
- Delays rate of sinus discharge
- Slows HR
What is bradycardia?
- slower than normal HR
What does Bradycardia result from?
- Stimulation of Vagus Nerve from medulla’s cardioinhibitory center
Does Parasympathetic stimulation excite or inhibit tissues?
- Excites some
- Inhibits others
What is the main reason for HR increase at the start and during low/moderate exerise?
- Inhibition of parasympathetic stimulation
How does HR increase further during strenous exercise?
- Additional parasympathetic inhibition
- Direct activation of sympathetic cardioaccelerator nerves
What continually modulates medullary activity?
- Impulses originating in brain’s higher somatomotor central command center
What provides the greatest control over HR during exercise?
- Central Command
What causes the heart rapidly turning on during exercise?
- decreasing parasympathetic inhibitory input
- Increasing stimulus input from central command
What explains how emotional state can effect cardiovascular response? What difficulty does this create?
Explains
- Central command of cardiovascular regulation
Difficulty
- Obtaining true resting values of HR and BP
What must the cardiovascular center receive?
- Reflex sensory input from peripheral receptors
Where are the reflex sensory input from peripheral receptors that send info to the cardiovascular center?
- Blood Vessels
- Joints
- Muscles
What do chemoreceptors and mechanoreceptors within muscle and vasculature monitor?
- Chemical physical state
What do chemoreceptors and mechanoreceptors within muscle and vasculator that monitor chemical physical states do?
- Modify parasympathetic/sympathetic outflow to provide appropriate cardio/respiratory response to various intensitites of physical activity
What three mechanisms continually assess the nature and intensity of exercise and muscle mass activation?
- Reflex neural input from mechanical deformation of Type II afferents within active muscles
- Chemical stimulation of Type IV afferents within muscles
- Feed-forward outflow from motor areas of central command
What govens central nervous system’s regulation of blood flow and BP during dynamic execise?
- Specific Mechanoreceptor Feedback
What are the specific mechanoreceptors that govern the central nervous system’s regulation of blood flow and BP during dynamic exercise?
- Pressure-sensitive baroreceptors
- Cardiopulmonary Receptors
Where are the pressure-sensitive baroreceptors that govern the central nervous system’s regulation of blood flow and BP during dynamic exercise?
- Aortic Arch
- Carotid Sinus
What do the cardiopulmonary receptors that govern the central nervous system’s regulation of blood flow and BP during dynamic exercise do?
- Assess mechanical activity in left ventricle, right atrium, and large veins
How does peripheral input function as a negative feedback controller to regulate BP?
- Inhibit sympathetic outflow from cardiovascular center
- Blunt inordinate rise in arterial BP
What physical law does blood flowing through a vascular circuit follow?
- Hydrodynamics applied to rigid, cylindrical vessels
What are the two factors that relate to the volume of flow?
Volume is:
- directly related to pressure gradient between two ends of the vessel
- inversely related to resistance encountered to fluid flow
What creates resistance in blood vessels that impedes blood flow?
- Friction between blood and internal vascular wall
What three factors influence resistance?
- Blood thickness (viscosity)
- Length of conducting tube
- Blood Vessel radius
What does Poiseulle’s Law express?
- relationship among pressure differential, resistance, and flow
What does Flow equal?
Flow = pressure gradient x vessel radius^4 / (vessel length x fluid viscosity)
What is true about vessel length in Poiseuille’s Law?
- Remains Constant
Explain how blood flow changes
- small variation in blood viscosity
- Radius change has greatest impact
How does blood flow change the most with change in radius?
- Constriction and dilation
What type of arteries provide mechanisms to regulate blood flow?
- Small arterial blood vessels
- constriction and dilation
What do any increases in energy expenditure require from blood flow?
- rapid adjustments
What happens to local arterioles of active muscles during exrcise? what about vessels of tissues that could compromise blood supply?
Active muscles
- Dilate
Unnessary Tissues
- Constrict
What two factors reduce blood flow to non-active tissues?
- Increase sympathetic nervouse system outflow
- Local chemicals that directly stimulate vasoconstriction or enhance effects of other vasoconstrictors
How does skeletal muscle blood flow relate to metabolic demands?
- Closely coupled
How does skeletal muscle blood flow closely couple metabolic demand?
- nerual vasoconstriction activity
- locally derived vasoactive substances within endothelium and red blood cells
How many muscle capillaries remain open at rest?
- 1 in 30-40
What does the opening of dormant capillaries in exercise do?
- Increases total muscle blood flow
- Delivers large blood volume, only minimal change in blood flow velocity
- Increases effective surface for gas and nutrient exchange
What do local factors related to tissue metabolism act directly on for vasodilation occurs?
- smooth muscle bands of small arterioles
- precapillary sphincters
What are some examples of factors within active muscles that regulate vasodilation?
- decreased tissue oxygen
- local increase in blood flow
- temperature
- carbon dioxide
- acidity
- adenosine
- magnesium
- potassium
- nitric oxide produced by endothelial cells lining blood vessels
How can the venous system increase local blood flow?
- “assessing” increases in metabolic needs of active muscle
- Releasing vasodilatory factors
What does nitric oxide serve as for blood? what does it do?
Signal molecule
- dilates blood vessels
- decreases vascular resistance
What provokes Nitric Oxide synthesis in vascular endothelium?
Increased blood flow through vessel lumen
- Signal Chemicals
- Sheering stress
- vessel stretch
What happens to the vascular endothelium in Congenital Heart Defects?
- No production of Nitric Oxide
What does the release of nitric oxide from vasculare endothelial cells do for local blood flow?
Initiates Cascade of Events:
- Attenuate sympathetic vasoconstriciton
- induce arterial smooth muscle relaxation
- increase blood flow
What do drugs like Viagra and Nitroglycerin do?
- Cause Vasodilation by stimulating NO gas release
When does vasodilation occur from NO release?
- When NO penetrates smooth muscle cells
What does MAP stand for?
- mean arterial pressure
- average arterial pressure during a cardiac cycle
What is the Equation for MAP?
MAP = DBP + [0.33 (SBP - DBP)]
What do MAP and Cardiac Output estimate?
- change in total resistance to blood flow in the transition from rest to exercise
- TPR = MAP/Q
What are the net effects of local metabolic-induced vasodilation vs. sympathetically induced vasoconstriction?
- O2 Transport
- Perfusion Pressure
