Lecture 15 Flashcards
How would one figure out the cardiac output in ml/beat?
HR x SV = CO
What is the stroke volume?
The amount of blood pumped from each ventricle per beat
How does one figure out the SV?
The volume of blood in diastolic minus the volume of blood in systole
What is the average blood volume of an adult?
4.5 -5 L
How much L of blood passes through the heart each minute?
The total blood supply in a minute
Is the SA node pacemaker intrinsic or extrinsic?
Intrinsic but is modified by extrinsic control to change pacemaker potential
Is the AP in the heart rate modified by AV node and SNS?
No. The AP stays the same intensity each time
What are the types of extrinsic HR controls?
Neural
Hormonal
Other factors
How does neural control HR?
SNS via thoracic nerve can increase slope of pacemaker potential to reach AP quicker (increase HR)
Ex. Scared, stress
PSNS via vagus nerve lowers HR by longer AP generate
How do hormones control HR?
Epi and norepinephrine
Thyroid hormones - increase HR over days by increase mitochondria numbers and epi receptors
What are other factors that alter the HR?
Ion - high K+ in ISF will decrease HR but can cause heart attack
Fever - increase temp = increase HR
Age - younger = higher HR
Fitness - lower HR from more fit ppl
What is the pathway of the pulmonary artery?
Towards the heart
Pulmonary vein towards lungs
At what condition are the cardiac fibers at optimal length?
Greater stretch the more optimal length for contraction because the more cross bridges formed at max stretch will make a greater force (higher SV)
What is Frank-Starling law?
The force of ejection is proportional to length of ventricle contraction
How can venus return increase?
Exercise (increased rate) or lower HR because it allows the ventricles to fill more
What is blood flow?
The volume of blood flowing through any tissue/ min
Determined by pressure and resistance
What are the 3 concepts that determines the resistance in blood?
Vessel length
Blood viscosity
Radius of arterioles controlled by smooth muscles (changeable)
What occurs if vasoconstriction happens?
Decrease radius = more resistance and less force to organs
More press in artery
Less press in organ (less blood flows into organ caps)
What are the intrinsic regulations of the arteriolar radius?
Myogenic regulation - smooth muscle reacts to the amount of pressure to allow more/less space
Metabolic regulation - high metabolism (low O2 high CO2 cause cells to release nitric oxide vasodia) // (endothelins -> vasocon)
What are the extrinsic regulations for the arteriole radius?
Neural regulation (SNS) - veno and vaso constriction by increased SNS signals
Hormonal - epinephrine increases blood flow to fight or flight components - Angio II + ADH / histamine
What controls the vasoconstriction to the brain?
Only the intrinsic can
What receptor constricts when epinephrine binds to it?
a-receptor constricts
b- receptor dilates
What hormones cause vasoconstriction in the systemic vascular resistance? How does this affect BP?
Angiotensin II, antidiuretic hormone (ADH), Norepinephrine, epinephrine
Increases BP
What is the hydrostatic pressure?
The pressure exerted on the walls of blood vessels
When flow is opposed by resistance
How is pulse pressure determined?
Pulse pressure = systolic - diastolic
How is mean arterial pressure determined?
MAP = diastolic + 1/3 pulse pressure
What are the 3 intrinsic regulations that control MAP?
Cardiac output
Arteriolar radius
Blood volume (Venus return)
What are the 2 extrinsic regulations that control MAP?
Neural -> baroreceptors (stretch) in carotid and aortic arch send signal to medulla to SNS or PSNS
-> chemoreceptors responds to pH, CO2, O2
Hormonal -> epinephrine increases HR,CO and MAP
-> renin-angiotensin increases vasoconstriction, venoconstriction and MAP
-> ANP to stop renin and lower MAP
