17-5: Factors affecting heart rate and heart diseases Flashcards
The basic heart rate is set by ___, but can be altered by: ___.
the conduction system (SA node); autonomic nervous system, chemicals, emotions, temperature, and gender and age
What has the most important influence on heart rate?
cardiovascular center of the autonomic nervous system
cardioacceleratory center
sends impulses over cardiac nerves to the heart when under stress
What kind of nerves are cardiac nerves?
sympathetic motor neurons
What do cardiac nerves release?
norepinephrine, which binds to adrenergic receptors at the SA node, causing it to fire more rapidly and the heart rate to increase
cardioinhibitory center
sends impulses over the Vagus nerve (cranial nerve X) to the heart
What does the vagus nerve release?
ACh, binding to colinergic receptors at the SA and AV node, causing it to fire more slowly and heart rate decreases
The cardioacceleratory center is controlled by the __ nervous system and the cardioinhibitory center is controlled by the __.
sympathetic; parasympathetic
vagal tone
when resting, the heart is in vagal tone - vagus nerve (PANS) in control
baroreceptors
special neurons in the carotid artery, aortic arch, and atria, that detect changes in blood pressure and send signals to the CAC and CIC to correct the problem
epinephrine
hormone produced by the adrenal gland when under stress
Epinephrine causes heart rate to ___ by ___.
increase by increasing the excitability of the SA node
hyperkalemia can lead to __.
heart block and cardiac arrest
hypokalemia can lead to __.
arrhythmias and a weak heart beat
hypercalcemia can lead to ___.
increased heart rate
hypocalcemia can lead to __.
slowed heart rate
How does emotion affect heart rate?
strong emotions like fear, anger and anxiety tend to increase heart rate; depression and grief cause heart rate to go down
How does temperature affect heart rate?
increased body temp (eg. fever, exercise) causes heart rate to go up
Women have ___ heart rate than men
faster
Heart rate ___ with age
decreases
myocardial infarction
the result of interrupted blood supply to an area of the myocardium; without O2, the area of heart tissue infarcts (dies) and the heart weakens
May be caused by thrombus, embolus, or atherosclerosis
thrombus
blood clot formed in coronary vessel
embolus
blood clot formed elsewhere, but travels to heart and lodges there
atherosclerosis
vessel blocked due to accumulated fatty deposits
How is a myocardial infarction diagnosed?
enlarged Q wave on EKG and serum enzyme studies
angina pectoris
temporary ischemia (reduced blood flow/O2 supply) to the myocardium causes myocardial cells to weaken but not die
may experience chest pain and tightness, difficulty breathing
What are some causes of angina pectoris?
coronary vessels constrict due to stress, atherosclerosis, strenuous exercise after a meal, or high blood pressure
heart murmur
abnormal heart sound; usually asymptomatic, but may lead to congestive heart failure and need to be repaired or replaced
What are the causes of a heart murmur?
faulty heart valve that allows regurgitation (some flow of blood backwards) or stenosis (a narrow, incompletely open valve); most common type is mitral valve prolapse
congestive heart valure
venous return > cardiac output (blood is returning faster than it is pumped out)
When does congestive heart failure occur?
when either ventricle fails to pump blood out as fast as it entered; blood backs up in the heart ,and it fails to meet the O2 demand of the body’s tissues
What can cause congestive heart failure?
long term hypertension, multiple heart attacks, coronary atherosclerosis
CHF can result in a pulmonary edema if __ ventricle fails, and/or a peripheral edema if __ ventricle fails
left (blood backs up into lungs); right (blood backs up in systematic loop)
Tachycardia
rapid heartbeat
Bradycardia
slow heartbeat
