Heart

Question 1

Normal blood pressure values

Answer 1

120/80

Question 2

Physical factors affecting MAP

Answer 2

Cardiac output

Total peripheral resistance (resistance to flow) how narrow blood vessels are

Pressure in the veins (central venous pressure) = 0

MAP = CO X TPR

Question 3

Cardiac output =

Answer 3

Stroke volume X heart rate

V = I X R

Question 4

Resistance to flow

Answer 4

Viscosity X length
R4

Radius most important in determinant to flow

Question 5

Control of blood pressure

Answer 5

Short term - autonomic
Heart rate chronotropy
Force of contraction (INotropy)
Contract relax of blood vessel

Long term control - endocrine
Increase / decreases diuresis
Increased decreased thirst

Question 6

Arterial baroreceptors

Answer 6

Pressure sensitive receptors
Respond to stretch

Stretch - increases frequency of firing

Question 7

Changes in baroreceptor sensitivity

Answer 7

Central resetting
Exercise - work sensors in skeletal muscle cause resetting or baroreflex to a higher pressure. Allows pressure to rise without impairing mechanisms of increase of cardiac output

Peripheral resetting - threshold for barareceptros resets to higher pressure after a few days. Ensures best sensitivity for changes in blood pressure

Structural changes
If arterial walls become less compliant intraluminal pressure changes therefore baroreceptors not as sensitive caused by old age and hypertension

Question 8

Other types of sensor involved

Answer 8

Myelinated venoatrial mechanoreceptors
Filling pressure
Increase in vol = increase in firing rate - reflex tachycardia and diuresis

Non myelinated
Found in atria and ventricles
Bradycardia

Coronary artery baroreceptors

Chemosensors
Ischaemic metabloites
Mediate pain assosciated with angina

Question 9

Fall in blood pressure due to loss of blood

Answer 9

Decreases baroreceptors
CNS control medulla and hypothalamus

Sympathetic - +Ve - vasoconstriction
Venoconstriction - mobile blood store
Increase heart rate
Increase force of contraction

In exercise - central resetting

Question 10

Rise in blood pressure ?

Answer 10

Baroreceptor traffic increases
Parasympathetic nervous system turned up
Vasodilation
Pee more

Question 11

Long term control of blood pressure

Regulation of plasma volume

Answer 11

Renin angiotensin system - ACE inhibitors. Block formation of angiotensin 2 which causes increase in sympathetic activity vol retention vasoconstriction - increase bp

Atrial natriuretic peptide -
Makes pressure lower- too much stretch - reducing volume - secreted from ATRIA in response to stretch increases renal salt and water excretion causes a shift from plasma to interstitatial compartment

Vasopressin - released controlled by osmorecptors and baroreceptors stimulates by increase in osmolarity and fall in blood pressure reduces water excretion
Supports blood pressure during hypovolemia

Thirst - osmosis out of cells into the circulation stimulates thirst increases water intake increases bloody volume

Question 12

What does tachycardia mean

Answer 12

Speeding heart up

Question 13

Ionotropy

Answer 13

Contraction

Question 14

Lusotropy

Answer 14

Relaxation

Question 15

Tunica intima is

Answer 15

Endothelium

Question 16

Tunica media is

Answer 16

Smooth muscle

Question 17

Tunica adventita is

Answer 17

Collage

Question 18

Where is blood volume stored

Answer 18

Veins

Question 19

Resistance is

Answer 19

Inversely proportional to blood vessel diameter
Blood vessels get smaller the further away from the heart you get therefore resistance increases and pressure energy is lost

Question 20

Flow is less pulsation because

Answer 20

Due to increased blood vessel compliance
Further from heart = more compliant - pulsation is dampened down by movement of vessel wall
Thinner walls are more stretchy and more compliant

Question 21

Cardiac output is

Answer 21

What keeps up alive

Stroke volume X heart rate
Resting = 4-7l/min
Adjusted regurally

Question 22

What affects stroke volume

Answer 22

Positive
Diastolic stretch - depends on venous filling pressure. The volume entering at the beginning of a contraction cycle is the volume ejected at the end of the cycle

Force of contraction

Negative

Arterial pressure

Question 23

Venous return

Answer 23

Blood returns to the heart via the vena cava
Rate of VR determines cardiac output
Circulation is a closed loop

Question 24

Factors affecting VR

Answer 24

Skeletal muscle activity - veins contain non return valves contraction displaces into next department mechanisms important for extremities

Breathing - inspiration - blood from abdomen to thorax - venous return

Sympathetic nervous activity - veins are normally stretchy- when sympathetic is activated it decreases the stretch in the walls - increase in pressure - increased vr increased Co

Gravity changes in posture impact upon forces affecting venous return. Standing causes pooling of blood in the feet and lower legs
Compensated by baroreceptor reflex - vasoconstriction
Local myogenic response skeletal muscle pumping breathing