haemostasis, haemorrhage and shock

Question 1

what is haemorrhage?

Answer 1

an acute loss of blood from a damaged blood vessel

Question 2

what is shock?

Answer 2

the state in which the decreased blood volume results in a fall in blood pressure and impaired delivery of nutrients to cells

Question 3

what should the immediate action to blood loss be?

Answer 3

stop the bleeding

Question 4

what should the short term action to blood loss be?

Answer 4

restore the blood pressure

Question 5

what should the medium term action to blood loss be?

Answer 5

restore fluid volume

Question 6

what should the long term action to blood loss be?

Answer 6

replace blood consitiuents

Question 7

what is haemostasis?

Answer 7

stopping blood loss

Question 8

what are the components involved in haemostasis?

Answer 8

• vascular response
• platelet response
• plasma response

Question 9

what is coagulation?

Answer 9

plasma response

Question 10

describe the vascular response in haemostasis?

Answer 10

Smooth muscle
- Spasm due to trauma
- Myogenic response
- Humoral factors (vasoconstrictors)
Endothelium
- Platelet adhesion and aggregation
- Anticlotting and fibrinolysis

Question 11

describe the platelet response in haemostasis?

Answer 11

• Damage to blood vessel causes turbulent blood flow so platelets come into contact with vessel wall (collagen)
• Platelets adhere; clump together (aggregate)
• Release chemicals that cause further aggregation (Positive feedback)
• Formation of platelet plug
• Effective in sealing small blood vessels

Question 12

describe the formation of a platelet plug

Answer 12

• damaged blood vessel
• platelets aggregate and release chemicals
• thromboxane A2 and ADP
• vasoconstriction
• platelet plug

Question 13

describe coagulation in haemostasis?

Answer 13

• Various plasma proteins and tissue components combine to convert fibrinogen to fibrin to form the blood clot
• Numerous ‘clotting factors’ are involved (many made in the liver)
• The synthesis of several clotting factors requires the presence of vitamin K
• The clotting factors are activated in an enzyme cascade
• One activated factor activates the next one in the sequence

Question 14

where are many of the clotting factors involved in coagulation made?

Answer 14

the liver

Question 15

what is required for the synthesis of many clotting factors?

Answer 15

vitamin K

Question 16

what can have an affect on coagulation?

Answer 16

calcium deficiency

Question 17

which blood clotting factor doesnt exist?

Answer 17

VI (same as IV)

Question 18

what are the two pathways of coagulation?

Answer 18

intrinsic and extrinsic

Question 19

how is the intrinsic coagulation pathway activated?

Answer 19

vascular damage

Question 20

how is the extrinsic coagulation pathway activated?

Answer 20

tissue damage

Question 21

what are required for both the intrinsic and extrinsic coagulation pathways?

Answer 21

phospholipid and calcium ions

Question 22

which blood coagulation pathway is more important at initiating clotting after injury?

Answer 22

extrinsic

Question 23

which blood coagulation pathway is more important to maintain the process?

Answer 23

intrinsic

Question 24

what is thrombosis?

Answer 24

blood clots form inside intact blood vessels causing blockages

Question 25

which coagulation pathway is involved in thrombosis?

Answer 25

intrinsic

Question 26

what is fibrinolysis?

Answer 26

dissolving the blood clot once it has served its purpose

Question 27

which enzyme is involved in fibrinolysis?

Answer 27

plasmin

Question 28

what triggers the compensatory mechanisms when there is a fall in blood pressure?

Answer 28

arterial baroreceptors

Question 29

what are the hormones released in baroreceptor relflexes?

Answer 29

adrenaline angiotensin II vasopressin (ADH)

Question 30

which nerves control baroreceptor reflexes?

Answer 30

sympathetic

Question 31

sequence of events following a decrease in blood volume

Answer 31

- decrease in BP - decrease in baroreceptor firing - CVS centres - increase in sympathetic NS activity - increase in HR, vent. const, veso const. and arteriole const - increase in ventricular and vaso constriction increases stroke volume - increase in HR increases cardiac output - increase in artieriole const, increases peripheral resistance - overall increase in mean arterial blood pressure

Question 32

what are the medium term responses to blood loss?

Answer 32

- Shifting interstitial fluid back into blood vessels - Decreasing fluid loss in kidney - Increasing fluid intake

Question 33

what does a decrease in arterial blood pressure cause through baroreceptor reflexes?

Answer 33

- vasoconstriction of arterioles - increases total peripheral resistance - decreases capillary blood pressure - decreases hydrostatic pressure pushing fluid out the capillary - more fluid is drawn back into the capillaries by oncotic pressure

Question 34

what does a decrease in fluid loss in the kidney cause?

Answer 34

- decreased glomerular filtration - increased reabsorption of sodium ions and water by stimulating the release of renin-angiotensin-aldesterone and the antidiuretic hormone (both vasoconstrictors)

Question 35

renin-angiotenisn-aldosterone system

Question 36

antidiuretic system

Question 37

antidiuretic system

Question 38

what are stimuli of thirst?

Answer 38

- increase in plasma osmolarity and decrease in ECF volume - angiotensin II - dry mouth

Question 39

feed-forward regulation

Question 40

what are the long term responses after blood loss?

Answer 40

Restore plasma proteins - Released from liver (3-4 days) Replace blood cells, esp. RBCs Erythropoiesis - Regulated by erythropoeitin (EPO) - EPO released from kidney - Stimulates RBC production in bone marrow - Return to normal in 2-3 months

Question 41

what are the different types of shock?

Answer 41

- hypovolaemic shock - low resistance/distributive shock - cardiogenic shock

Question 42

describe hypovolaemic shock

Answer 42

- decrease in ECF volume due to haemorrhage - sweating, diarrhoa, burns etc

Question 43

describe low resistance/distributive shock

Answer 43

- decrease in peripheral resistance due to vasodilation - eg anaphylactic shock