PHS 206 CVS 2 Flashcards
Types of blood vessels
Arteries
Arterioles
Venules
Veins
Capillaries
Arteries
(aorta is largest)
-Thick-walled, extensive elastic tissue, smooth muscle, and connective tissue
-Under highest pressure
-Stressed Volume—volume of blood contained in arteries
Arterioles (smallest branches of the arteries)
-Extensive smooth muscle in walls
-Site of highest resistance to blood flow
-Innervated by sympathetic adrenergic nerve fibers
*α-Adrenergic receptors caused constriction of smooth muscle (resistance to blood flow)
●Found in skin and splanchnic vasculature
*β2-Adrenergic receptors cause relaxation of smooth muscle (decrease resistance)
●Found in skeletal muscle
Capillaries
-Lined by single layer of endothelial cells
-Site where nutrients, gases, water, and solutes are exchanged between blood and tissues
-Lipid-soluble substances (O2, CO2) diffuse across capillary wall
-Water-soluble substances (ions) use pores to cross capillary wall
-Not all capillaries are perfused with blood at all times
*Selective perfusion is determined by degree of dilation or constriction of arterioles and precapillary sphincters
Venules and veins
-Venules are thin-walled
-Veins have modest amount of elastic tissue, smooth muscle, and connective tissue
-Large capacitance (capacity to hold blood)
-Contain largest percentage of blood in cardiovascular system
-Unstressed volume—volume of blood contained in veins
-Smooth muscle in walls of veins innervated by sympathetic nerve fibers
*Increases in sympathetic nerve activity contracts veins lowering their capacitance and therefore reduces unstressed volume
Types of heart rate regulation
Intrinsic (situated within the heart) regulation
Extrinsic (originating outside the heart) regulation
Types extrinsic regulation
Neural
Cortical Input
Peripheral Input
Describe instrinsic regulation
Depolarization muscle membrane creates an action potential or electrical impulse
Impulse travels through the heart in an established pathway
SA node →across atria →AV node →AV bundle →left & right bundle branches → Purkinjie fibers → Ventricles
Describe the neural control of HR
Neural Influences override intrinsic rhythm
Sympathetic: catecholamines
Epinephrine: increases heart rate (tachycardia) and contractility
Norepinephrine: acts as a vasoconstrictor
Parasympathetic
Acetylcholine: decreases heart rate (bradycardia) and contractility
Endurance (aerobic) trg. increases vagal dominance
Nerve fibres involved in the neural control of HR
Cardiac accelerator nerves
Vagus nerves
Discuss the cardiac accelerator nerves
Sympathetic Fibers
Innervate SA node & ventricles
Increase heart rate
Increase contractility
Increase pressure
Discuss the vagus nerves
Parasympathetic Nerve
Innervates SA node & AV node
Releases acetylcholine
Slows heart rate
Lowers pressure
Discuss the cortical influence on the heart
Cerebral cortex impulses pass through cardiovascular control center in medulla oblongata.
Emotional state affects cardiovascular response
Cause heart rate to increase in anticipation of exercise
Discuss the peripheral influence on the heart
Peripheral receptors monitor the state of active muscle; and modify vagal or sympathetic
Chemoreceptors
Monitor pCO2, H+, pO2
Mechanoreceptors
Heart and skeletal muscle mechanical receptors
Baroreceptors in the carotid sinus and aortic arch.
↑ pressure → increase HR & contractility
↓ pressure → decrease HR & contractility
List the phases of the cardiac cycle
- rest
- atrial systole
- ventricular systole (isovolumetric ventricular contraction)
- ventricular ejection
- ventricular diastole (isovolumetric relaxation)
