BIOL 273 - Unit 4.3 + 4.4 Flashcards
Describe late diastole
Entire heart relaxed
atria and ventricles are relaxed
- semilunar valves closed; AV valves open
- blood enters ventricles passively
Describe Atrial systole
atria contract, ventricles relaxed
- semilunar valves closed , Av valves open
- small amount of blood enters ventricles
Describe isovolumic ventricular contraction
ventricles contract
- AV and semilunar valves closed
- volume doesn’t change
Describe Ventricular ejection
semilunar valves open, AV valves shut
- blood ejected (systemic circulation)
Isovolumic ventricular relaxation
semilunar valves closed; AV valves closed
What are the steps to the cardiac cycle
- Late diastole
- Atrial systole
- Isovolumic ventricular contraction
- Ventricular ejection
- Isolvolumic ventricular relaxation
Describe the “lub” sound during the cardiac cycle
due to closing of AV valves
Describe the “dub” sound
due to closing of semilunar valves
End diastolic volume (EDV)
maximum volume in ventricle - end of ventricular filling
End systolic volume (ESV)
minimum volume in ventricle - end of ventricular contraction
What is cardiac output and how to calculate it
- the amount of blood pumped by the heart in one minute
Heart Rate x Stroke Volume
Stoke volume = EDV - ESV
Factors influencing Heart Rate
- Parasympathetic stimulation - decreases heart rate
- Sympathetic stimulation - increases heart rate
- Plasma Epinephrine (from adrenal medulla) - increases heart rate
Factors influencing stroke volume
- Parasympathetic stimulation - decrease contractility
- Sympathetic stimulation - increases contractility
- Plasma Epinephrine - increases contractility
- Increased End-Diastolic volume - increases stroke volume
What is the hollow tube of blood vessels made of (2)
- Lumen
- Wall (made of layers)
What does the wall of blood vessles consist of (4)
- Inner lining - enothelial cells make up endothelium
- Elastic connective tissue
- Vascular smooth muscle (vasoconstriction/vasodilation)
- Fibrous connective tissue
What are the five types of blood vessels
- Artery - thick walled to withstand high pressure
- Arteriole - smallest arteries
- Capillary - smallest blood vessels - exchange of material
- Venule - smallest veins
- Vein - transport blood at low pressure
What are the factors that influence blood flow through the vessels of the body (4)
- Myogenic autoregulation
- Paracrine hormones
- Innervation by sympathetic division of autonomic nervous system
- Hormone signals via circulating epinephrine
What is myogenic autoregulation
stretch receptors in wall of arterioles when activated cause vasoconstriction
What are paracrine horomones
released from vascular endothelium and tissues - cause vasodilation or vasoconstriction
innervation by sympathetic division of autonomic nervous system is to referred to
- Norepinephrine - binds to alpha receptors, causes vasoconstriction
- Epinephrine - binds to alpha receptors, reinforces vasoconstriction
Hormonal signals via circulating epinephrine
binds to beta 2 receptors
- found ONLY in vascular smooth muscle of heart, liver and skeletal muscle
- causes vasodilation
How is pressure decreased in blood flow
pressure decreased by friction between blood and the walls of the blood vessel
Describe the relationship between flow, pressure and resistance
flow isn proportional to the pressure difference and inversely proportional to the resistance
When does blood flow occur
When there is a pressure gradient from high to low pressure
Describe arterial blood pressure
it reflects the driving pressure caused by the heart pumping:
- highest in arteries
- lowest at point of return to the heart
Systolic pressure
time when the heart is contracting - highest arterial pressure
Diastolic pressure
time when the ventricle relaxes - lowest arterial pressure
P wave in ECG
Depolarization of atria
QRS complex in ECG
ventricular depolarization
T wave in ECG
repolarization of ventricles
P-R segment in ECG
atrial contraction
S-T segment in ECG
ventricular contraction, just after Q wave
What does the mean arterial pressure factor
systolic pressure and diastolic pressure
- becasue arterial pressure is pulsatile
Factors affecting mean arterial pressure
- Cardiac output
- Changes in blood volume (normally constant)
- Peripheral resistance
How can peripheral resistance affect mean arterial pressure
- modify the diameter of arterioles
- ## small changes in radius means large changes in resistance
Baroreceptors
stretch sensitive mechanorecepotrs found in vessel walls of the carotid artery and aorta.
- monitors blood pressure
- vasodilation
- negative feedback
