Lecture 10: Controlling the Heart and Blood Pressure Flashcards
What generates pressure for systemic circulation?
The left ventricle
What is linked to the high pressure in the large systemic arteries?
Ventricular contraction and ejection of blood
What is pulsatility in major arteries due to?
Non-continuous pumping of blood (systole/diastole)
What is Mean Arteriole blood Pressure a critically important determinant of?
Blood flow
Is blood pressure high or low in major arteries?
High
Where does blood pressure fall steeply?
Across the Arterioles, Capillaries and Venules
What is reduced due to the steep fall of blood pressure across Arterioles, Capillaries and Venules?
The oscillatory nature of blood pressure
Is blood pressure high or low in veins?
Low
What does the large pressure difference between the arterial and venous sides of the circulatory system do?
Creates a driving force for blood flow
What does ejection of blood into the arterial system maintain?
Arteriole blood volume and blood pressure
What is arteriole blood volume and pressure determined by?
Balance between blood flow “in” and “out”
What are effects of blood flow into the arteries?
3
- Fills arteries
- Increases arterial blood volume
- Raises arteriole pressure
What are effects of blood flow out of the arteries?
3
- Drains arteries
- Decreases arterial blood volume
- Lowers arterial pressure
What are causes of blood flow in to the arteries?
3
- Ventricular contraction
- Ejection of blood
- Cardiac output
What are contributing factors to blood flow out of the arteries?
(2)
- Capillary flow
- Controlled by resistance of the arteries
A balance of blood flow in and blood flow out determines what?
Blood pressure
What does an increase of cardiac output do to blood flow?
Increases inflow
What does an increase in resistance do to blood flow?
Decreases outflow
What does an increase in cardiac output and resistance do?
Increases arterial volume and pressure
What is the equation for Mean arteriole pressure?
Arterial pressure = Cardiac output x Total peripheral resistance
What is cardiac output determined by?
Stroke volume and heart rate
What is stroke volume determined by?
Contraction strength
What is heart rate determined by?
Contraction speed
What is the approach of small animals to meeting cardiac output needs?
High heart rates with a small stroke volume
What is the approach of large animals to meeting cardiac output needs?
High stroke volume with a small heart rate
How does a failing heart meet the needs of cardiac output?
Increased heart rate to make up for a small stroke volume
What happens to the heart during exercise?
Heart rate/stroke volume increase leading to a larger cardiac output
What 2 systems are used by the brain to control and respond to changes in blood pressure?
- Afferent input
- Effect output
What are baroreceptors?
Blood pressure sensors
What kind of receptors are baroreceptors?
Stretch receptors
Where are baroreceptors located?
In the walls of arteries
How does the brain sense pressure changes in the arteries?
Through baroreceptors
What does the carotid artery supply blood too?
The brain
What do baroreceptors do when the blood pressure is optimal in arteries?
It send a signal to the brain at a constant optimal pace
What do baroreceptors do when the blood pressure rises in arteries?
It sends a signal to the brain at an increased pace above what is seen as optimal
What do baroreceptors do when the blood pressure falls in arteries?
It sends a signal to the brain at an decreased pace below what is seen as optimal
What 2 signalling systems does the brain use to control heart rate?
Parasympathetic/sympathetic systems
What system used by the brain slows down heart rate?
The parasympathetic system
What system used by the brain speed up heart rate?
The sympathetic system
What pathway does the parasympathetic system follow to innervate the sinoatrial and atrioventricular nodes?
The vagus nerve
What pathway does the sympathetic system follow to innervate the sinoatrial, atrioventricular nodes and the ventricle walls?
Down to the sympathetic trunk ganglion then out through the sympathetic cardiac nerves
What parts of the heart are innervated by the parasympathetic nervous system?
SA and AV nodes
What parts of the heart are innervated by the sympathetic nervous system?
SA/AV nodes and the ventricle walls
How does the parasympathetic nervous system act on the SA/AV nodes?
It slows the amount of the signals sent by the sinoatrial node and increases the length of the delay on signals induced by the AV node
How does the sympathetic nervous system act on the SA/AV nodes?
It increases the amount of the signals sent by the sinoatrial node and decreases the length of the delay on signals induced by the AV node
What happens to stroke volume as the body is positioned upright during the tilt test?
It decreases slightly
What happens to cardiac output as the body is positioned upright during the tilt test?
It decreases
What happens to heart rate as the body is positioned upright during the tilt test?
It increases
How is MAP maintained whilst cardiac output decreases during the tilt test?
Total peripheral resistance increases
What is Cardiac output calculated by?
Cardiac output = stroke volume x heart rate
