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Pharmacology
week 2 (first half of cardio lecture)
42
Other
Not Applicable
01/19/2008

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Cards

Term
structure of the heart
Definition

cone-shaped, hollow, muscular organ weighing about 300g

in mediastinum, left of midline, between 3rd & 6th intercostal cartilage

 

function: supplying oxygenated blood to all cells of the body through 60,000 miles of blood vessels and returning deoxygenated  blood to the lungs 

Term

all muscle tissue contracts in response to a(n) ____ stimulus or impulse.

 

Cardiac muscle is unique; not only can it respond to a(n) _____ impulse, it also has ____ that can generate their own electrical impulses. 

Definition

electrical

electrical

pacemaker cells 

Term
Four primary characteristics of cardiac cells
Definition
Conductivity: ability of cardiac cells to receive an electrcal stimuls and then conduct it to other cardiac cells
 
Contractility: ability of cardiac cells to shorten, causing cardiac muscle contraction in response to an electrical stimulus (to eject the blood)
 
Automaticity: ability of cardiac pacemaker cells to generate their own electrical impulses (SA node-normal conduction starts here, AV node, bundle of his/purkinje fibers)
 
Excitability: irritability; ability of cardiac cells to respond to an electrical stimulus; when a cardiac cell is highly excitable, less stimulus is required to cause contraction
Term
ready state polarization
Definition
a property of all tissue cells; K+ is on the inside of the cell and Na+ is on the outside; muscle is relaxed and cardiac cells are ready to receive an electrical impulse
Term
depolarization
Definition
the phase of contraction; myocardial cells are conducting an electrical impulse through the muscle causing the heart to contract (heartbeat); as the electrical impulse moves through the cells, K+ leaves the cells and Na+ enters.  While in this state, the cardiac cells are fully depolarized.  They cannot respond to any further electrical impulses until they have repolarized.
Term
repolarization
Definition
the recovery phase; the cells are returning to a ready state, however, all cells are not repolarized at the same time.  So, some cardiac cells are able to conduct an electrical impulse sooner than others.  After the electrical impulse has passed through the cells, K+ reenters the cell and Na+ leaves.
Term
refractory period
Definition
the time between the end of a contraction and reutrn of the cardiac cells to the ready state. While the cells are recovering, the atria and ventricles are refilling with blood and preparing to contract again.
Term
the two phases of the refractory period
Definition

Absolute refractory period: cardiac cells have not completed repolarization and cannot be stimulated to conduct an electrical impulse and contract again (depolarize); period from the beginning of the QRS complex through about the first 1/3 of the T wave

 

Relative refractory period: cardiac cells have repolarized to the point that some cells can again be stimulated to depolarize, if the stiumus is strong enough.  If these cells are stimulated during this period, they could conduct the electrical impulse in an abnormal pattern.  The period from the end of the absolute refractory period to the end of the T wave (vulnerable).

Term
Autonomic Innervation
Definition

heart rate is under the control of the autonomic NS (symp/parasymp divisons); involuntary but can be modified with drugs

 

cardiac centers in the brainstem in the medulla oblongata (sends APs) 

Term
Sympathetic NS
Definition

via efferent (adrenergic) fibers to the heart, accelerates the heart rate and strengthens the force of contraction through the effects of circulation catecholamines- norepinephrine and epinephrine

 

fight or flight 

Term
Norepinephrine
Definition

binds with BETA 1 adrenergic receptors of the heart, increasing the rate of impulse generation and the strength of contraction during systole

 

binds with ALPHA 1 adrenergic receptors in the coronary arteries causing vasocontriction 

Term
Epinephrine
Definition

binds with BETA 2, BETA 1, and ALPHA 1 adrenergic receptors

 

BETA 1 - stimulate the heart

 

ALPHA 1- constricts certain blood vessels

 

BETA 2- dilutes certain blood vessels and causes bronchodilation 

Term
Parasympathetic NS
Definition
via the efferent (cholinergic) vagus nerve, when vagal stimulation occurs, the neurotransmitter ACETYLCHOLINE is released at the juntion of the nerve and the myocardium; it slows the heart rate by inhibiting impulse formation and electrical conduction in the heart
Term
Baroreceptors
Definition

specialized nerve tissue in the internal carotid arteries and the aorta are responsible for activation of the vagus nerve

 

e.g. when stimulated upon stretch, such as occurs in HTN, these receptors activate the vagus nerve to decrease HR & AV conduction (accommodate to change in pos'n so fainting doesn't occur in orthostatic HTN) 

Term
Blood pressure
Definition

pressure the blood exerts on the blood vessels walls, i.e., the arteries, capillaries, and veins

 

differs in the vessels - it is greatest in the arteries and falls as blood moves into the capillaries and veins

 

generated by the left ventricle during contraction/systole

 

arterial pressure is composed of the systolic and diastolic pressures 

Term
Systolic pressure
Definition
max pressure generated by the left ventricle during contraction (systole)
Term
Diastolic pressure
Definition
pressure exerted on the artery walls during relaxation of the diastolic phase of the cardiac cycle
Term
Pulse Pressure
Definition
difference between SBP and DBP
Term
BP is lowest at birth and increases with age as the vessels lose their _____ and therefore more pressure is required to pump blood through them.
Definition
elasticity
Term
BP is maintained by the interplay of four systems:
Definition

Renal

Endocrine

Neurologic

Cardiovascular 

Term
Renal System
Definition

produces and stores a proteolytic enzyme-RENIN- that is being released into the bloodstream in response to a decrease in BP

 

in the circ. system, renin reacts w/ a substrate formed in the liver, and inactive peptide-angiotensinogen, to form ANGIOTENSIN I

 

Angiotensin I is converted to ANGIOTENSIN II by the enzyme Angiotensin Converting Enzyme (ACE) found in highest quantities in the lungs

 

Angiotensin II is a powerful vasoconstrictor which then constricts blood vessels in order to elevate the BP directly

 

Angiotensin II stimulates the adrenal cortext to release ALDOSTERONE, a mineralocorticoid, increasig the reabs. of Na+ in the kidney which increases blood vol. and elevates BP indirectly 

 

Term
Renin-Angiotensin system is thought of as being responsible for the ____ control of BP.
Definition
long-term
Term
Endocrine System
Definition

posterior pituitary is also stimulated by a decrease in BP; it increases its release of ANTIDIURETIC HORMONE (ADH) or VASOPRESSIN

 

Aldosterone and ADH increase the reabs. of Na and H20, increasing blood vol. (decreased urine release leads to increased circulating vol) 

Term
Neurologic System
Definition

responds to a fall in BP by stimulating the sympathetic NS

 

this causes peripheral vasoconstriction and increased HR and stroke vol, which leads to an increase in CO (b/c CO = SV x HR)

 

NS also responds to messages from the pressure sensitive baroreceptors in the aortic arch and carotids

 

low pressure messages from baroreceptors elevate  BP.  In the heart, BETA receptor stimulation will cause increased contractility and HR; in the blood vessels, ALPHA receptors are stimulated causing vasoconstriction 

Term
Sympathetic NS regulation of BP is thought of as ____ control.
Definition
rapid and short-term
Term
Cardiac Output (CO)
Definition

volume of blood ejected from the heart in unit time (usually min)

 

~5 L

 

CO = SV x HR 

Term
Stroke Volume (SV)
Definition

volume of blood ejected with each beat

 

~70 cc/beat 

Term
Heart Rate (HR)
Definition

number of beats/min

 

60-90 beats/min is average 

Term

Blood Pressure

 

BP = ________ 

Definition

pressure the blood exerts on the blood vessels walls

 

BP = CO x PVR 

Term
Afterload
Definition

force against which the left ventricle must contract to eject blood

 

arterial pressure, arterial resistance (narrow diameter = higher pressure) 

Term
Preload
Definition
amount of blood going into the heart (amt the heart has to eject)
Term

Types of chemical effects on the heart

 

(3) 

Definition

Inotropic

 

Chronotropic

 

Dromotropic 

Term
Inotropic effects on the heart
Definition

affect the strength of myocardial contraction (strength leads to increased CO)

 

pos. inotropic effects = pts with pump failure respond to drugs with this action 

Term
Chronotropic effects on the heart
Definition

affect the rate of myocardial contraction by altering the rate of impulse formation at the SA node

 

pos chronotropic effect = pts w/ bradyarrhythmias respond to increased cardiac rate

 

neg chronotropic effect = pts w/ tachyarrhythmias respond to decreased cardiac rate 

Term
Dromotropic effects on the heart
Definition

affect the conduction of electrical impulses through the myocardium (through AV node)

 

pos dromotropic effect = pts w/ heart blocks respond to increased AV conducdtivity

 

neg dromotropic effect = pts w/ conduction disorders such as atrial fibrillation resond to decreased/blocked conduction 

Term
Hypertension
Definition

persistant elevation of SBP > 140mmHg or DBP > 90 mmHg at least 3 times on 2 different occasions

 

Isolated systolic HTN (ISH): persistant elevated SBP w/ normal DBP (more damage from systolic; treated as drastically as HTN w/ both elevated

 

primary HTN: 95% of people, genetic

secondary HTN: neurological problems, etc 

Term
Etiology of Primary HTN:
Definition

Imbalances

 

symp. NS hyperactivity: increased HR leads to decreased CO, which increases BP

 

renin-angiotensin system malfuntion: feedback loops may not work properly allowing for higher circulation levels of renin, leading to HTN

 

sodium balance problems & salt sensitivity: inability to normally excrete Na via the kidneys and/or abnormal electrolyte transport, resulting in disturbance in the systolic Ca/Na balance and vasoconstricition

 

age, AA heritage, DM, low renin levels often predict salt sensitivity

 

causes: increased Na intake, heredity, ETOH intake, smoking, obesity

 

**usually multifactorial 

Term
Etiology of secondary HTN:
Definition

second most common reason for office visits int he US and for use of prescription drugs

 

approx. 50 million Americans affected

about 32% AA popl'n, 23%  of white and Mexican-American popl'n

Term

Complications of Hypertension

 

(8) 

Definition
-Cardiovascular Disease: HTN is the major risk factor; more common than smoking, diabetes, etc.; increase in risk as BP rises above 110/75 mmHg
-Heart Failure: increased risk at all ages
-Left Ventricular Hypertrophy: common w/ HTN; associated w/ enhanced incidence of HF,ventricular arrhythmias, death following MI, sudden cardiac death
-Stroke (CVA): most common/important risk factor
-Intracerebral Hemorrhage: most important risk factor
-Chronic Renal Insufficiancy & End stage Renal Disease
-Retinopathy: caused by long term, uncontrolled HTN
-Acute, Life-Threatening Emergency: hypertensive encephalopathy
Term
symptoms/signs of HTN
Definition
often none; "silent killer" b/c don't realize that damage is being done until it's too late and irreversible
Term
Major Cardiovascular Disease risk factors:
Definition

HTN

obesity (BMI > 30 kg/m)

dyslipidemia

diabetes mellitus

smoking

physical inactivity

microalbuminuria

age (>55 for men, >65 for women)

family history of premature CVD 

Term
Lifestyle Modification Recommendations
Definition
weight reduction: 5-20mmHg SBP reduction
DASH eating plan: 8-14 mmHg
Dietary sodium reduction: 2-8 mmHg
Aerobic physical activity: 4-9 mmHg
Moderation in alcohol consumption: 2-4 mmHg
 
one drug decreases one side by 5-10 mmHg, so this can lead to a large # of drugs if lifestyle cannot be modified
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