Lecture 10 Flashcards
What is the format blood pressure is usually shown in?
Systolic BP over Diastolic BP
What is the highest pressure detected in the arteries?
Systolic, when the heart is contracting
What is the lowest pressure in the arteries?
Diastolic, when the heart is relaxing
Blood pressure falls steeply across what?
Arterioles, capillaries and venues
Where is blood pressure most oscillatory in nature?
In major arteries where blood pressure is high
Where is blood pressure the lowest?
In veins, furtherest away from the left ventricle
What creates a driving force for blood flow?
Large difference in pressure between arterial and venous sides. creates a concentration gradient
What does blood flow in cause?
Fills arteries
increases arterial blood volume
raises arterial pressure
Blood flow out causes?
Arteries to be drained
decrease in arterial blood volume
lowers arterial pressure
What is cardiac output?
ventricular contraction causing an ejection of blood
Blood flow out is controlled by?
resistance of the arteries into capillary beds
How to increase cardiac output?
Increase in flow
How to increase resistance?
decrease outflow
Mean arterial pressure =
CO x TPR
Cardiac output =
SV x HR
what is stroke volume?
Litres per beat
what is heart rate?
Beats pre minute
Which phase of the cardiac cycle does the volume of blood rapidly decrease?
ventricular ejection
If the stroke volume is high will the heart rate be high low?
Low because CO = SV x HR
What are baroreceptors?
blood pressure sensors
two examples of where baroreceptors are?
Carotid artery
aorta
Why is the left side of the heart required to function at high pressure?
because it supplies blood to the entire body
What is contraction strength?
Stroke volume
What is contraction speed?
Heart rate
When does the first sound wave happen? (ECG)
After the QRS wave
Where does the second sound wave happen? (ECG)
After the T wave
What nervous system does the Vagus nerve innervate?
Parasympathetic
Where does the Vagus nerve sit in the spinal cord?
Dorsal motor nucleus of vagus. Cardioinhibitory centre
Medulla oblongata
What does the vagus nerve do?
Decreases heart rate
What does the vagus nerve act on?
the SA node and AV node
Describe the pathway of the sympathetic cardiac nerves?
Begins in the cardioacceleratory centre in medulla oblongata. Travels to thoracic spinal cord and out the sympathetic trunk ganglion
What do the sympathetic cardiac nerves do?
increase heart rate and force of contraction
What is TPR?
All of the vascular resistance offered by the systemic blood vessels
What size vessels contribute the greatest resistance?
Smaller vessels such as Arterioles, capillaries, venules
Which spinal nerves are responsible for an increase in HR?
T1-4 spinal nerves
Why do we not want pulsatile blood pressure?
Because we want smooth, even and consistent blood flow to important parts of the body ie. brain
