VST 206 outline notes

Membrane permeability stimuli Biochemicals mechanical impulses physical factors

AUTOMATICITY Ability to spontaneously depolarize Conductive tissue All or Nothing Principal If one fiber depolarizes, then the others will follow.

Impulse travel speed Atria – Impulse carried via the SA node via the internodal tracts to the AV Ventricles – Impulse pauses at the AV node before entering the bundle of His

Impulse Speed - Ventricles As the impulse enters the bundle of His from the AV node, the speed increases The bundle of His is a continuation of the AV node

CONTRACTILITY Shortening of the muscle fiber in response to an impulse. Can be compromised by ?

REFRACTORY period What is it? How does it relate to arrythmias What are the clinical signs of arrythmias ?

Phases of the Cardiac Cycle Diastole-the period of Systole-the period of contraction

Conductive Fibers Impulses are spontaneously generated The cardiac cycle spans from what to what?

Atria Contraction of the atria will supply what? How long do the av valves remain open. Semilunar valves are closed during atrial contraction

Ventricular & Atrial Filling/Contraction What happens in the different phases?

Heart Sounds 1st heartsound: 2nd heart sound: Cardiac Murmurs: Caused by ? Systolic murmurs occur between Diastolic murmurs occur between

The regulatory mechanisms of the cardiovascular system are designed for maintaining what Blood Supply to Tissues = CO x R What is CO ? R?

Heart rate Controlled by the Autonomic Nervous System: Influences HR Direct SM vs PSM.

Sympathetic Nervous System Sympathetic nerves stimulate heart action by the release of Lidocaine is a sodium channel blocker and it is commonly used in

Parasympathetic NS Parasympathetic nerve stimulation releases ______________ which decreases heart rate due to depression of the S.A. node

SM vs PSM Sympathetic denervation causes a small decrease in the resting rate. Parasympathetic denervation causes a marked elevation in the heart rate.

Cardiac Innervation Vagus n (parasympathetic) – Direct innervation – SA and AV nodes – ______ muscle Sympathetic – Direct innervation What parts of the heart are

Humoral Factors Not as pronounced as CNS Beta 1 Receptors Muscarinic 2 Receptors

What Controls Cardiac Stroke Volume? Preload Afterload Contractility Distensibility Synergy of Ventricular Contraction

Vasoconstrictor Norepinephrine stimulates ?

Vasodilator fibers - Sympathetic vasodilation commonly occurs in ?

Non-Neurogenic Control of Vascular Resistance (vs. direct innervation) Beta-2 receptors - Stimulation of these receptors by circulating norepinephrine causes vasodilation. Alpha-2 receptors – can also be stimulated by circulating epinephrine in a fight or flight response can cause vasoconstriction that competes with Beta 2 receptor stimulation by NE

End of week 3 9/16/2015

Direct Innervation vs. Indirect Influence of Vascular Resistance The effects of circulating catecholamines on vascular smooth muscle are minor compared to the effects of Circulating catecholamines have little effect on blood pressure except for

catecholamines are: __________ They are made from phenylalanine and tyrosine.phenylalanine The release of these are from what

Baroreceptors (Aortic Arch, Carotid Sinus) sense a change in vascular pressure Baroreceptor sends signals to where?

Afferent Nerves What are they a. where are they? b. Carotid sinus fibers form ?

Efferent Fibers nerve fibers that direct impulses from the where to where? Autonomic motor fibers: a. Sympathetic nerves b. Parasympathetic nerves

Effecters are tissues with a specific function

Effectors (continued) Cardiac Tissue: S.A. node and myocardium – Increases in sympathetic nervous tone increase the heart rate and force of contraction thereby increasing the c.o. and the b.p. – Decreases in sympathetic tone and increases in parasympathetic stimulation decrease the heart rate and decrease the force of contraction thereby decreasing the c.o. and BP

Topic V Congestive heart failure Definition Anything that can cause a decrease in stroke volume CO = HR x SV

Heart Failure: Adverse changes in the following can result in heart failure: Decreased ? Increased ? Decreased ? What is Asynergy

Compensatory Mechanisms Acute adjustments vs chronic adjustments

Limits of Increasing HR Decreased preload – Decreased contractility

Increased Force of Contraction Sympathetic nerve stimulation increases the force of myocardial contraction.

Vasoconstriction Sympathetic nerve stimulation promotes vasoconstriction

Expansion of Extra-cellular fluid volume (ECF)Volume Sodium Retention – Can occur in the short term or chronically to increase blood volume.

Mechanisms of Na+ (ECF) Retention

Atrial (B-type) Natriuretic Peptide – what is it?

Uses for NT-proBNP assay

Chronic adjustments: Cardiac Enlargement Increased diameter by Increased mass by

HYPERTROPHY Physiologic hypertrophy – Pathologic hypertrophy –

Pathologic Enlargement Eccentric Hypertrophy Concentric Hypertrophy