Heart Test #2 Flashcards
What does cardiac output measure?
a measure of how hard the heart is working?
What is cardiac output?
the volume of blood ejected from the left ventricle, into the aorta each minute
What is the formula for cardiac output (CO)?
CO = SV (stroke volume) x HR (heart rate)
Stroke volume unit of measure
SV : stroke volume (ml/beat)
Heart rate unit of measure
HR : heart rate (beats per minute)
The Franklin-Sterling Law states….
The more the heart is stretched (i.e. filled with blood), the harder it will contract, forcing more blood out
Cardiac output
Venous return
Affects stroke volume
What is venous return?
rate of blood flow back to the heart
What regulates the heart rate?
- autonomic control and chemical regulation
Where is the autonomic control center located?
the medulla oblongata
What does the autonomic control center/medulla oblongata receive messages from?
Proprioceptors (body position)
Chemoreceptors (O2 , CO2 , pH)
Baroreceptors (blood pressure)
Chemoreceptors detect what?
changes in the chemical composition of the blood
What are the two branches of the autonomic nervous system?
- parasympathetic nervous system
- sympathetic nervous system
Sympathetic nerves run from _______________ _______________ to the _____________
medulla oblongata, SA node
What neurotransmitter is used by the sympathetic nervous system?
norepinephrine
What is norepinephrine’s effect on heart rate?
- increases the amount depolarization occurs (more “+”)
- decreases the amount of times repolarization occurs
- thus increasing the heart rate
- increases Ca+2 entry, increasing the force of contraction
The vagus nerve (X) acts as what for the parasympathetic nervous system?
the main component of the PSNS/contains the main nerves of the PSNS
What neurotransmitter does the parasympathetic nervous system release?
acetylcholine (ACh)
What is acetylcholine’s effect on heart rate?
Hyperpolarization of SA node (more “-“)
-takes longer to depolarize
thus heart rate slows
What two components are involved in chemical regulation?
hormones and ions
What hormones increase heart rate?
epinephrine and thyroid hormone
What ion increases heart rate?
Ca2+
What ion decreases heart rate?
Na+ and K +
In what ways is a fetus dependent on the mother?
- Fetal lungs, kidneys and GI tract are nonfunctioning
- O2 and nutrients come from mother’s blood
- CO2 and wastes are passed to mother’s blood
What is the placenta?
a disc of tissue that connects a mother’s uterus to the umbilical cord, and is ultimately responsible for delivering nutrients and oxygen to a fetus
The placenta acts as what organs for the fetus?
lungs, kidneys and GI tract of fetus
What is the relationship between the placenta and blood vessels?
- the placenta contains both the mother and fetus’s blood vessels
- blood vessels do not connect, but just lie close to one another
What process does the placenta/fetus use to transport O2, nutrients, and waste products?
diffusion
What’s different about fetal hemoglobin?
Fetal Hemoglobin has higher affinity for O2 than mother’s Hb (speeds up transfer of oxygen from mother to fetus
What does the umbilical cord connect?
connects fetus to the placenta
What does the umbilical cord contain?
2 umbilical arteries
- from fetus to placenta
- carry low O2 blood
1 umbilical vein
- carries high in O2 blood back to fetus
What does the umbilical vein join?
the portal and inferior vena cava
What are the fetal differences in blood flow?
Some blood (already oxygenated) from right atrium passes directly to left atrium through foramen ovale (whole between left and right atrium)
Remaining blood in rt atrium passes to rt ventricle and then enters the pulmonary artery
Much of the blood entering pulmonary artery passes through the ductus arteriosus (connects pulmonary trunk to aorta) to the aorta
Only a small portion of blood in pulmonary artery goes to lungs (nonfunctional) (are growing organs that still need oxygen from the blood)
What parts of the fetus change at birth?
- lungs
- foramen ovale
- ductus arteriosus
- umbilical arteries
- umbilical vein
Fetal changes at birth: lungs
Lungs inflate and become functional
Fetal changes at birth: foramen ovale
foramen ovale gradually closes to become fossa ovalis (indent)
Fetal changes at birth: ductus arteriosus
Ductus arteriosus closes and becomes ligamentum arteriosum
Fetal changes at birth: umbilical vein
Umbilical vein becomes round ligament (belly BUTTON)
Fetal changes at birth: umbilical arteries
Umbilical arteries become lateral umbilical ligaments
What is the cause of the phenomenon known as “blue babies”?
failure of foramen ovale/ductus arteriosus to close causing blood to not become fully oxygenated
What are the common heart problems?
- Heart murmur
- Atherosclerosis
- Ischemia
- Myocardial infarction
Heart murmur
- Heart valve does not completely close
- Allows some backflow of blood (regurgitation)
- Common, but usually not serious
Atherosclerosis
- blockages of coronary circulation
- fatty substances deposited in arteries (inadequate blood flow)
- can cause inadequate blood supply to heart muscle
Atherosclerosis can lead to what?
Ischemia
Ischemia
- Reduced O2 supply weakens heart cells
- Angina pectoris (chest pain: “stop these activities”)
Myocardial infarction
- aka a HEART ATTACK
- Depending on extent of damage, can cause heart cells not to beat in synchrony (fibrillation)
- Dead tissue is replaced by noncontractile scar tissue (heart mad weak now)
How do defibrillators work?
cause a unison depolarization of the heart to attempt to make it contract/beat again
