Lecture 12- cardiac output and blood pressure

Question 1

What is the cycle for homeostatic control of blood pressure?

Answer 1

1. Change in blood pressure
2. Baroreceptors
3. Glossopharyngeal nerves
4. Medulla Oblongata
5. Autonomic nerves
6. Effectors (heart and blood vessels)
7. Back to start

Question 2

Where are these chemoreceptors located?

1. peripheral
2. central

Answer 2

1. Carotid body and aortic body
2. Medulla oblongata

Question 3

What do the chemoreceptors detect?

Answer 3

Increase in CO2 (decrease in pH)

Question 4

WHat is the formula for blood pressure?

Answer 4

BP= Cardiac output x total peripheral resistance

Question 5

What factors control short term blood pressure?

Answer 5

Baroreceptor reflex and Chemoreceptor reflex. (change heart rate and vasodilation/casoconstriction)

Question 6

What controls long term blood pressure?

Answer 6

• Kidney Na+/H2O homesostasis
• Hormones

(these control extracellular fluid volume which changed blood pressure)

Question 7

What is an inotropic effect?

Answer 7

A change in the force of muscular contractions (usually of the heart). A positive inotropic effeect will increase the strength of the contraction.

Question 8

What inotropic effects do these have?

1. SNS
2. PNS
3. Adrenaline

Answer 8

1. Positive
2. Minor negative since the vagal nerves don’t innervate the ventricles
3. Positive

Question 9

What causes:

Increased velocity of conduction of cardiac muscles

INcreased velocity of shortening and relaxing of cardiac muscle

Positive inotropic effect

Answer 9

The SNS

Question 10

What is contractility?

Answer 10

The contractile ability of cardiac muscle at a given preload

Question 11

What does a positive inotropic effect of the ventricles cause?

WHat chemical mechanism causes this?

Answer 11

Increase in stroke volume

Caused by increase in release of Ca2+ from intracellular stores. Calcium-induced-calcium release

Question 12

Which 3 factors influence venous return?

Answer 12

1. Posture
2. Muscle pump- constriction by muscles
3. Respiratory pump- inspiration creates internal pressure difference

Question 13

What is Starling’s law of the heart?

Answer 13

The energy of contraction is proportional to the intial length of the cardiac muscle fibre.

Question 14

What does ventricular filling rely on?

Answer 14

Atrial filling which is determined by central venous pressure or venous return

Question 15

What affect does an increased EDV have on CO? Starling’s Law?

Answer 15

Increased EDV increases the initial length (stretch) of cardiac muscl fibres and this increases Cardiac Output.