vst 206 outline notes. membrane permeability stimuli biochemicals mechanical impulses physical...
TRANSCRIPT
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