Cardiovascular (Homeostasis and Integration)

vagal tone

slowing of the heart rate

what system slows heart rate?

parasympathetic nervous system

chronotropic agents

factors that change heart rate, alter activity nodal cells, act on nerves innervating the SA or AV node

positive chronotropic agents role

increase heart rate, include sympathetic nerve stimulation and some hormones

dromotropism

rate of conduction through the conduction system of the heart

where do primary factors to change HR come from?

autonomic innervation and certain hormones

positive chronotropic agents

epinephrine, norepinephrine, thyroid hormone, caffeine, nicotine, cocaine

epinephrine/norepinephrine

increases came and Ca influx

Thyroid hormone

increases number of beta adrenergic receptors, makes nodal cells more responsive to epinephrine and norepinephrine

caffeine

increases cAMP and heart rate

nicotine

stimulates norepinephrine and increases heart rate

cocaine

inhibits reuptake of norepinephrine, increases heart rate, can lead to fast and erratic heart beat(possibly fatal)

negative chronotropic agents

parasympathetic innervation, beta-blocker drugs

parasympathetic innervation

axons releasing acetylcholine, bind voltage gated K channels, causes hyperpolarization, longer time for cells to reach threshold, slows heart rate

beta blocker drugs

interfere norepinephrine and epinephrine binding to beta receptors, used to treat high blood pressure

major variables influencing stroke volume

venous return, inotropic agents, afterload

starlings law

states that the critical factor controlling stroke volume is preload

preload

the degree to which the cardiac muscle cells are stretched before they contract

most important factor to cause stretch

the amount of blood in the ventricles, which is controlled bu venous return

what is preload proportional to?

the amount of ventricular myocardial fiber stretch just before systole (EDV)

what can increase stroke volume?

anything that increases EDv or increases the force of the ventricular contraction

what does extrinsic control of SV include?

sympathetic drive to ventricular muscle fibers and hormonal control

cardiac reserve

increase in cardiac output above rest level, HR accelerated during exercise, SV increased to more than 100mL, subtract cardiac output a trest from output with exercise

increased flow to coronary vessels during exercise

helps ensure sufficient oxygen reaches cardiac muscle

skeletal muscle blood flow increasing during exercise

needed to meet high metabolic demands

increased percentage of blood flow to skin during exercise

to help dissipate heat

relatively less blood during exercise

to abdominal organs, kidneys, less metabolically active structures

blood flow distribution during exercise

increase in total blood flow, due to faster and stronger heartbeat, due to blood removal from venous reservoirs, ensures metabolically active tissues receiving adequate blood

hypertension

blood pressure too high, can damage blood vessels and lead to cardiovascular disease

hypotension

blood pressure too low, body deprived of nutrients, may cause death if severe

systems that help maintain blood pressure

endocrine, nervous, urinary

orthostatic hypotension

temporary drop in blood pressure when standing up from a prone or reclining position, also known as postural hypotension

what causes orthostatic hypotension

due to blood pooling in he extremities and the SNS not signaling the lower vessels to constrict and send blood back toward the heart

what does prolonged hypertension cause?

heart failure, renal failure, stroke, and vascular disease

primary hypertension

main type, no single cause

secondary hypertension

result of a disease, usually from tumor of the adrenal medulla

secondary hypertension can be a sign of?

cushings, physical obstruction of the renal arteries, kidney disease, arteriosclerosis, hyperthyroidism

factors that are involved in the development of hypertension

diet, obesity, age, gender, diabetes mellitus, genetics, stress, smoking

what is used to treat hypertension

diuretics, beta blockers, calcium channel blockers, ACE inhibitors, and ATI receptor antagonists

regulation of blood pressure/flow

dependent on cardiac output, resistance, blood volume, variable regulated through nervous system and endocrine system, needs to be high enough to maintain tissue perfusion

arryhmias

uncoordinated atrial and ventricular contractions caused by a defect in the conduction system

fibrillation

rapid and irregular contraction where the SA node is no longer controlling the heart rate

atrial fibrillation

can cause clotting and inefficient filling of the ventricles

ventricular fibrillation

when ventricles pump without filling and if the rhythm is more rapidly re established circulation stops and brain death occurs

defibrillation

application of an electrical stimulus to shock the heart back to a normal SA rhythm

ectopic pacemaker

a conducting cell that takes over excitation in the conduction system

extrasystole

premature contractions

systemic edema

may occur if right ventricle impaired, more blood remaining in systemic circulation, additional fluid entering interstitial space

pulmonary edema

may occur if left ventricle impaired, more blood remaining in pulmonary circulation, swelling and fluid accumulation in the lungs, breathing difficulties and impaired gas exchange

athersclerosis

coronary arteries narrowed and occluded

coronary spasm

sudden arrowing of vessels, both can lead to angina or myocardial infarction

angina pectoris

pain sensation on left side of chest, arm or jaw, generally results from strenuous activity, referred pain, medications inducing temporary vascular dilation

myocardial infarction(heart attack)

sudden and complete occlusion of coronary artery, region of myocardium deprived of oxygen, possible tissue death, sudden excruciating substernal chest pain radiating down left arm

heart attack effects/symptoms

weakness, shortness of breath, nausea, anxiety, and sweating

heart murmur

abnormal heart sound, result of turbulence of blood passign through heart, some medically important and others are not

bradycardia

persistently low heartrate in adults, >60 bpm

tachycardia

persistently high resting heart rate 100> bpm

cause of tachycardia

heart disease, fever, anxiety

cause of bradycardia

hypothyroidism, electrolyte imbalance, and congestive heart failure