Lecture 8 - Blood P and control of heart

Question 1

What is an important determinant of blood flow?

Answer 1

MAP

Question 2

1. Blood pressure is high and oscillatory in…..
2. Across what does blood pressure fall steeply? (Oscillatory nature reduced)
3. Large difference in pressure between ___ and ____ sides creates a ___ ____ for blood flow
4. What are resistance vessels?

Answer 2

1. Major arteries (pulmonary artery not as high)
2. Microcirculation (arterioles, caps and venules)
3. Arterial and venous……driving force
4. Small arteries and arterioles

Question 3

Arterial blood volume and pressure are determined by what?

Answer 3

Balance between blood flow in and out

Question 4

What is blood flow in and out? Balance between these two determines what?

Answer 4

Blood flow in:

• fills arteries, increases arterial blood volume and raises arterial pressure
• ventricular contraction, ejection of blood = CARDIAC OUTPUT

Blood flow out:
-drains arteries, decreases arterial blood volume, lowers arterial pressure
-Capillary flow, controlled by resistance of arteries
(amount of blood moving into caps i.e. blood flow out of arteries….small arteries and arterioles determine how easily it is for blood to move out of arteries and into caps)

Balance between these two determines pressure
-increase cardiac output (increase inflow)
-increase resistance (decrease outflow)
=increase arterial volume and pressure

Question 5

Soon MAP = ? x ?

Answer 5

CO x TPR

Like P = Q x R

MAP is tightly regulated - narrow range

Question 6

What is CO determined by?

Answer 6

CO = SV x HR

L/min = L/beat x beats/min

This is variable e.g. change in exercise will change HR and/or SV

Question 7

Stroke volume determined how and is life and right the same?

Answer 7

Go to graph and peak - trough of ventricular volume = SV (same for both left and right)

Question 8

Blood pressure sensors are called?

1. _____ cells in ___ ____ (mostly) or ____ ____ in neck. Densely packed in these arteries and connected to ____.
2. Sense _____ - the more _____ out = more ______ back to brain so e.g. pressure _____ and blood causes ______ of arterial wall = the cells send signal to ______ and brain responds (also happens if blood P too low)

Answer 8

Baroreceptors

1. Special cells in aortic arch (mostly) or carotid sinus in neck. Densely packed in these arteries and connected to nerves.
2. Sense stretch - the more stretched out = more signal back to brain so e.g. pressure increases and blood causes expansion of arterial wall = the cells send signal to brain and brain responds (also happens if blood P too low)

Question 9

What’s the brake and what’s the accelerator in the neural control?

Answer 9

Parasym is brake and sym is accelerator

Question 10

Parasympathetic

1. Sends signal through ___ nerve. ____ node - it makes the ______ longer and _____ slower (so it must innervate ____ node too) and larger pause = reduced _____ so reduced _____

Sympathetic:

2. Sends signal through ____ ____ (T1 - ___) through ____ ____ _____. Signal controls both ____ and ____ - makes SA ___ and AV ____ delay. It directly innervates ___ ____ - stimulates more _____ release so more x bridges so stronger beats (it has more control than ____ bc needed in fight/flight)

Answer 10

1. Sends signal through vague nerve. AV node - it makes the pause longer also pacemaker slowed (so it must innervate SA node too) and larger pause = reduced CO so reduced pressure
2. Sends signal through spinal cord (T1 - T4) through symp chain gang. Signal controls both SA and AV - makes SA faster and AV shorter delay. It directly innervates Purkinje fibres - stimulates more Ca release so more x bridges so stronger beats (it has more control than parasym bc needed in fight/flight)

Question 11

For the tilt table - SV decreases, HR increases but not as much so overall decrease CO but MAP needs to stay the same so what increases?

Answer 11

Vascular resistance