6 - Cardiovascular control 2

Question 1

Equation for stroke volume?

Answer 1

SV = end-diastolic vol - end-systolic vol

Question 2

Equation for cardiac output?

Answer 2

Q = SV x HR

Question 3

Equation for blood pressure? (MAP)

Answer 3

MAP = Q x total peripheral resistance (TPR)

Question 4

What is venous volume distribution affected by?

Answer 4

Peripheral venous tone
Gravity
Skeletal muscle pump
Breathing

Question 5

Where is central venous pressure measured?

Answer 5

The right atrium

Question 6

How is flow controlled in veins?

Answer 6

Veins are compliant. They can constrict to reduce venous return.

Question 7

In arterioles, what does constriction determine?

Answer 7

Blood flow to downstream organs
Mean arterial blood pressure
Pattern of blood flow to organs

Question 8

What is the main way flow is changed by? What equation shows this?

Answer 8

Vessel radius.
Flow = change in pressure/resistance
Resistance = 1/r^4

Question 9

What type of mechanisms are intrinsic to smooth muscle?

Answer 9

Local mechanisms - local blood flow regulation within an organ.

Question 10

What type of mechanisms are extrinsic to smooth muscle?

Answer 10

Systemic mechanisms - e.g.
Circulating hormones
Autonomic nervous system

Question 11

What is autoregulation? What are the theories behind it?

Answer 11

The intrinsic capacity to compensate for changes in perfusion pressure by changing vascular resistance.
E.g. if pp falls, without autoregulation flow will fall. With autoregulation, resistance will decrease so that flow can increase.
Theories for autoregulation are myogenic and metabolic.

Question 12

What is myogenic theory?

Answer 12

Smooth muscle fibres respond to tension in the vessel wall.

E.g. as pressure rises, fibres contract. Involves stretch sensitive channels.

Question 13

What is metabolic theory?

Answer 13

As blood flow decreases, metabolites accumulate and the vessels dilate. Subsequent increased flow washes the metabolites away

Question 14

What does injury do to vessel radius?

Answer 14

Serotonin release from platelets causes constriction.

Question 15

Name 4 LOCAL (endothelium derived) hormones?

Answer 15

Nitric Oxide (NO)
Prostacyclin
Thromboxane A2 (TXA2)
Endothelins (ET)

Question 16

Name 5 CIRCULATING (non-endothelium derived) hormones?

Answer 16

Kinins
Atrial natriuretic peptide (ANP)
Vasopressin (ADH)
Noradrenaline/Adrenaline
Angiotensin II

Question 17

How does Nitric oxide work?

Answer 17

VASODILATOR
Made from arginine
Diffuses into vascular smooth muscle cells

Question 18

How does Prostacyclin work?

Answer 18

VASODILATOR
Made from prostaglandin precursor (PGH2)
Anti platelet and anticoagulant effect too.

Question 19

How does thromboxane A2 work?

Answer 19

VASOCONSTRICTOR
Made from prostaglandin precursor (PGH2)
Heavily synthesised in platelets

Question 20

How do endothelins work?

Answer 20

VASOCONSTRICTOR
Made from nucleus of endothelial cells.
Have minor vasodilator effects.

Question 21

How do kinins work?

Answer 21

Hormones that bind to receptors on endothelial cells.
Stimulates NO synthesis.
VASODILATOR effects.

Question 22

How does Atrial natriuretic peptide (ANP) work?

Answer 22

Secreted from atria in response to stretch.

VASODILATOR effects to reduce BP.

Question 23

How does Vasopressin work?

Answer 23

Secreted from posterior pituitary in response to high blood osmolality. Binds to V1 receptors on smooth muscle to cause VASOCONSTRICTION.

Question 24

How does noradrenaline/adrenaline work?

Answer 24

Secreted from adrenal gland. Causes VASOCONSTRICTION.

Question 25

How does angiotensin II work?

Answer 25

VASOCONSTRICTOR from renin-angiotensin-aldosterone axis. | Stimulates SNS activity and ADH secretion.

Question 26

What is the broad function of the parasympathetic nervous system?

Answer 26

Rest and digest - heart rate

Question 27

What is the broad function of the sympathetic nervous system?

Answer 27

Fight or flight - circulation

Question 28

Where does the parasympathetic system arise from?

Answer 28

The cranial and sacral part of the spinal cord.

Question 29

Where does the sympathetic system arise from?

Answer 29

The thoracic and lumbar vertebra.

Question 30

Where do sympathetic neurones synapse?

Answer 30

Sympathetic chain paravertebral ganglia.

Question 31

What neurotransmitter is used in ALL pre-ganglionic fibres?

Answer 31

Acetylcholine

Question 32

What neurotransmitters are used in post-ganglionic fibres?

Answer 32

Sympathetic: Noradrenaline Parasympathetic: Acetylcholine

Question 33

Which fibres are longer in the sympathetic and parasympathetic system - pre or post ganglionic?

Answer 33

Sympathetic: Shorter pre, longer post (because of paravertebral ganglia) Parasympathetic: Longer pre, shorter post

Question 34

Sympathetic fibres initiate the heart and all blood vessels except what?

Answer 34

capillaries and pre capillary sphincters. | some metarteroles.

Question 35

What do sympathetic fibres heavily initiate? What is weakly innervated?

Answer 35

Heavily: Kindeys, gut, spleen, skin Lightly: Skeletal muscle, brain

Question 36

What does noradrenaline bind to?

Answer 36

a1 adrenoceptors to cause smooth muscle contraction and vasoconstriction.

Question 37

What is the VMC? What do the different parts do?

Answer 37

Vasomotor centre - part of brain. In bottom part of pons and medulla. Lateral parts control: Heart rate and contractility Medial parts control: Decreases heart rate via vagus nerve

Question 38

What are the 3 different areas in the VMC?

Answer 38

Vasoconstrictor (pressor) area Vasodilator (depressor) area Cardioregulatory inhibitory area

Question 39

What is baseline SNS discharge?

Answer 39

The sympathetic system is always innervating the vessels. Increased and decreased levels of innervation are what causes vasoconstriction and vasodilation.

Question 40

Summary: What extrinsic factors affect vessel radius?

Answer 40

Circulating hormones | Sympathetic nervous system

Question 41

Summary: What intrinsic (local) factors affect vessel radius?

Answer 41

``` Oxygen Metabolites Potassium Osmolarity H+ CO2 ```

Question 42

Which nerves increase HR and which decrease HR?

Answer 42

Sympathetic increases HR | Parasympathetic decreases HR

Question 43

How does noradrenaline have an affect on the force of contraction, what is the mechanism?

Answer 43

1. Noradrenaline binds to B1 receptors on heart cell 2. Increased cAMP 3. Increased protein kinase A 4. PKA phosphorylates the L-type calcium channels, SR calcium release channels and calcium ATPase. 5. Calcium influx, uptake and release is all increased = more forceful contraction.

Question 44

What extrinsic things increase stroke volume?

Answer 44

Sympathetic nervous stimulation | Plasma adrenaline

Question 45

What intrinsic things increase stroke volume?

Answer 45

End diastolic volume (Starling's law) Influenced by: Increased venous return & atrial pressure Increased respiratory movements = Decreased intrathoracic pressure

Question 46

How is arterial pressure detected?

Answer 46

Baroreceptors (-ve feedback). Respond to stretch. Fire more when they're stretched more.

Question 47

Where are baroreceptors found? How do they send info?

Answer 47

Mechanoreceptors are in the carotid sinus and aortic arch. Carotid sinus: Via glossopharyngeal nerve (PNS afferent) Aortic arch: Vagus nerve (PNS afferent and efferent)

Question 48

At what pressures can baroreceptors sense and when are they most sensitive?

Answer 48

They can respond to pressures between 60-180mmHg. | They are most sensitive at 90-100mmHg.

Question 49

How do baroreceptors change blood pressure?

Answer 49

Baroreceptor recognises increase in BP. Increased baroreceptor activity Increased afferent input Increased PNS stimulation to heart to SLOW HR. INHIBITS sympathetic stimulation of heart and blood vessels = slower HR and vasodilation (tonic activity decreases)

Question 50

What 4 things can increase venous return?

Answer 50

- Increased Skeletal muscle pump - Increased Blood volume - Increased sympathetic nerve stimulation - Increased respiratory movements

Question 51

How is arterial blood pressure maintained?

Answer 51

See poster