Test #2 Flashcards
Def: Cardiac Output
The amount of blood pumped by heart per minute
Def: Stroke Volume
Blood pumped during each heartbeat (ml/beat)
Def: Cardiac Reserve
Difference between cardiac output at rest and maximum cardiac output during exercise
Def: Heart Rate
Number of times heart meats per minute (beats/min)
What is the equation for calculating cardiac output
CO=HRxSV
Def: Intrinsic Regulation
Results from normal functional characteristics, not on neural or hormonal regulation
Def: Extrinsic Regulation
Involves neural and hormonal control
What 3 factors regulate stroke volume
preload, afterload, contractility
Def: Preload
The amount of stretch of the ventricular walls before contraction
Frank-starling law of the heart
The greater the preload, the greater the force of contraction because stretching of the sarcomeres optimizes the overlap into a range for the highest pumping. Increased EDV= increased stretch on the walls=optimized overlap of actin and myosin = increased force of contraction = increased stroke volume
Def: Venous Return
Amount of blood returning to the heart from systemic circulation, which determines EDV. Can be affected by skeletal muscle contractions known as muscle pump
How does muscle pumping work
Skeletal muscles squeeze area of the veins to actively pump the blood toward the heart
Def: Afterload
The pressure the contracting ventricles must produce to overcome the pressure in the aorta and move blood into the aorta
Def: Contractility
The forcefulness of contraction of the ventricle muscle fibers, which is controlled by inotropic agents
Def: Inotropic Agents
Substances which increase or decrease contractility of the ventricle muscle fibers
Def: Positive Inotropic Agents
open Ca2+ channels of the cardiac accelerator nerves which release the neurotransmitter norepinephrine and the hormone epinephrine from the adrenal medulla
Def: Negative Inotropic Agents
Drugs such as calcium channel blockers and beta blockers (decrease oxygen demand)
Factors which regulate HR (7)
Autonomic nervous system, hormones, ions, age (increases but max decreases), gender (females higher at rest), physical fitness (decreased at rest), temperature (increase in temp increases HR)
Parasympathetic Nerve Stimulation Control of Heart Rate
Vagus nerve decreases heart rate. Neurotransmitter acetylcholine hyperpolarizes the heart causeing more K+ channels to open
Sympathetic Nerve Stimulation Control of Heart Rate
Cardiac accelerator nerves increase heart rate. NE released at the SA/Av nodes opens more Ca2+ channels
Hormonal Control of Hearth Rate
Epinephrin and NE are release from the adrenal medulla. Acts slower but last longer. Acts as a backup system
Effects of blood pressure
Baroreceptors monitor blood pressure in the internal carotid arteries and aorta, sensory information goes to centers in the medulla oblongata
Effects of pH, Carbon dioxide and oxygen
Chemoreceptors detect pH and CO2 changes in the medulla oblongata through the CSF, and chemoreceptors monitor O2 in the carotid and aortic bodies
Effects of extracellular ion concentration
excess or reduced extracellular K+ decreases heart rate