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. • 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 ?• 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