How does baroreceptor firing relate to blood pressure?
Higher BP increases firing - cause parasympathetic stimulation
Lower BP decreases firing - cause sympathetic stimulation
What is the NTS? Describe it.
NTS = nucleus of the tractus solitarius
Location that directs signals from the aortic and carotid baroreceptors (via CN X and XI, respectively) to the medulla, which has three cardiovascular centers: vasoconstrictor, cardiac accelerator, and cardiac decelerator centers
What are the formula and term for cardiac power?
P = CO x MABP
Cardiac minute work
What factors increase myocardial oxygen consumption (MVO2)?
Heart rate
Initropy
Afterload - pressure work
Preload (least effect) - volume work
Distinguish the two types of cardiac hypertrophy
Eccentric hypertrophy - in response to excessive preload, sarcomeres added in series
Concentric hypertrophy - in response to excessive afterload, sarcomeres added in parallel
What is the purpose of erythropoietin and how does it work?
Increase blood volume and pressure
Erythropoietin is produced in response to low oxygen saturation
Binds to RBCs in bone marrow to stimulate maturation
What is the purpose of ADH and how is its secretion regulated?
ADH increases blood pressure via water reabsorption in the kidneys
Osmoreceptors in the hypothalamus sense increased hematocrit during dehydration and stimulate ADH secretion
Decreased baroreceptor firing also increases ADH secretion
How does ADH work?
Two types of receptors:
V1 receptors on smooth muscle cells - binding of ADH causes increase in IP3 via G protein pathway, releasing stored calcium and increasing TPR
V2 receptors on kidney collecting tubules - binding of ADH causes increase in cAMP concentration, causing incorporation of aquaporins into membrane and increasing water reabsorption
Explain the renin-angiotensin-aldosterone system
Kidney senses low blood pressure and releases renin into the blood stream
Renin catalyzes cleavage of angiotensinogen produced in the lung to angiotensin I
ACE enzyme converts angiotensin I to angiotensin II
Angiotensin II causes vasoconstriction (increase TPR) and release of aldosterone
Aldosterone is a transcription factor that increases expression of epithelial sodium channels to increase Na reabsorption
What is the purpose of atrial natriuretic peptide (ANP) and how does it work?
ANP lowers blood pressure in response to increased stretching of atrial walls
Acts on kidneys and smooth muscle cells
Vasodilates and blocks secretion of renin and aldosterone, increasing sodium secretion
What properties determine normal electrical activity of the heart?
Automaticity - the ability of the heart to spontaneously fire action potentials
Excitability - the ability of cardiac cells to respond to electrical activity
Conductivity - the ability of the heart to conduct the action potential to all cardiac cells from the site of origin
What is the normal duration of the PR interval?
.12 - .2 seconds
What is the normal duration of the QRS interval?
.06 - .1 seconds
Short duration because of rapid conduction via Purkinje fibers
What is the duration of the QT interval?
Normally less than .42 seconds
Longer suggests abnormality with ventricular contraction
What are the five basic types of arrythmias?
- Normotopic
- Ectopic
- Re-entrant
- Conduction blocks
- Pre-excitation syndromes
When does the a wave in the Wigger’s diagram occur?
During atrial contraction
When does the c wave of the Wiggers diagram occur?
During isovolumetric contraction and of the left ventricle
When does the V wave of the Wiggers diagram occur?
During atrial filling
What causes heart sound S3?
Rapid flow of blood from the atria to the ventricles
What causes heart sound S4?
Vibrations of the ventricular wall due to ventricular filling during atrial systole
