Controlling the heart and blood pressure Flashcards
Cardiac output
How much the heart pumps out/ how much is in the pipes
Which ventricle generates the systemic blood pressure?
The left ven, generated at iso where V doesnt change but P is built to surge blood
What is the imporant determinant of blood flow
Mean arterial blood pressure
Where is blood P is highest?
The arteries, oscillatory pattern
Where does blood P fall and oscillatory nature reduced?
steeply across
the arterioles, capillaries, and
venules
Where is blood P low
Veins
Where is blood P the lowest
The right atrium
What creates the driving force of blood flow
The diff. in P of arterial and venous sides, not absolute P value
What is Haemodynamics?
How blood flows through a single vessel
Flow
Pressure diff/resistance
Q = ∆P/R
More flow is caused by…
Greater P difference/ lesser resistance
∆P =
MAP - 0 = MAP
MAP =
Q X R
What do we want to keep steady?
The pressure, so flow is steady
Blood flow in:
– fills arteries
– increases arterial blood volume
– raises arterial pressure.
– Ventricular contraction
– Ejection of blood
– CARDIAC OUTPUT
What determines flow out?
RESISTANCE
Blood flow out
– drains arteries
– decreases arterial blood volume
– lowers arterial pressure.
Capillary flow
– Controlled by resistance of the arteries
- Arterial blood volume and pressure are determined by:
– balance between blood flows “in” and blood flow out
- Balance flow in / out determines
pressure
– Increase cardiac output (increase inflow)
– Increase resistance (decrease outflow)
– Increase arterial volume and Pressure
MAP = CO x TPR
Arterial Pressure = Cardiac output x Total Peripheral Resistance
Factors that determine how much blood pumped out
-BPM
-Size of “squirt” i.e Stroke Volume
CO = SV x HR
Cardiac Output = Stroke Volume x Heart Rate
(L/min) (L/beat) contraction strength (beats/min)
contraction speed
Stroke volume of a healthy heart
70mL per beat
Healthy heart rate
60-80 bpm
Failing heart stroke volume
40mL/ beat
Failing heart rate
120 - 130 bpm
How much blood in our body
5L
What do we wanna keep steady as it drives the system?
MAP
Is MAP tightly controlled?
Yes, it has a narrow range
What is TPR?
Blood vessels vascular resistance
System that received info and releases info about BP in…
The brain (CNS), coordinated at the brainstem
In/Output from brain
– Afferent input from both the CNS and ‘periphery’ (baroreceptors)
– Efferent output to heart and vessels
What are baroreceptors?
Blood pressure sensors
Where are Baroreceptors located?
Arch of Aorta
What DO bARORECEPTORS DO?
-They are tonically active
-They dont turn on or off but have resting activity that ^ or decreases –> relayed to cardiovas pasrt of brainstem where decision is made to regulate the BP
Two neural controls of cardiac output
Sym and Parasym
Parasym
- Brake / reducing output
- When BP is too high, need to reduce
- Vaugus nerve reduces by affecting the SA and AV nodes i.e the pacemakes and “pause” nodes
Sym
- Accelerator
- When BP too low
- Sym cardiac nerves ^ by affecting ugus nerve reduces by affecting the SA and AV nodes i.e the pacemakes and “pause” nodes, (affects HR) + ven uscles to pump harder (affects SV)
Baroreflex
We dont have to think about our heartbeat
