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Homeostatic Mechanisms and Blood
Negative Feedback, Blood Groupings, Clottings and Pathology
170
Biochemistry
Undergraduate 1
02/08/2013

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Term
What is homeostasis?
Definition
The maintenance and control of a constant internal environment
Term
What is pathophysiology?
Definition
The failure to maintain homeostasis
Term
Outline the simple response pathway?
Definition
Stimulus -> Sensor -> Controller -> Effector -> Response
Term
What is negative feedback?
Definition
The production of a particular reponse decreases the initial stimulus so no further response can occur
Term
Which three systems are involved in homeostatic control?
Definition
Nervous, Endocrine and Paracrine
Term
What does ANS stand for?
Definition
Autonomic Nervous System
Term
What are the three control centres for the ANS?
Definition
Hypothalamus, Brain Stem and the Spinal Cord
Term
What are the two branches of the ANS?
Definition
Sympathetic and Parasympathetic Systems
Term
What does the Sympathetic Nervous System control?
Definition
Defense mechanisms 'Fight/Flight Response'
Term
What does the Parasympathetic Nervous System control?
Definition
Relaxation mechanisms 'Rest/Digest Response'
Term
How many types of neurons are involved in the Sympathetic Nervous System?
Definition
Two
Term
How many types of neurons are involved in the Parasympathetic Nervous System?
Definition
Two
Term
Where do Preganglionic neurons originate in the ANS?
Definition
The CNS
Term
What does CNS stand for?
Definition
Central Nervous System
Term
Where do postganglionic originate in the ANS?
Definition
Autonomic ganglia
Term
What are the two areas that parasympathetic pathways begin?
Definition
Cranium and Pelvis
Term
What is the relative length of the preganglionic nerve in the parasympathetic pathway?
Definition
Long
Term
What is the relative length of the postganglionic nerve in the parasympathetic pathway?
Definition
Short
Term
What is the relative length of the preganglionic nerve in the sympathetic pathway?
Definition
Short
Term
What is the relative length of the postganglionic nerve in the sympathetic pathway?
Definition
Long
Term
Which area does the parasympathetic pathways begin?
Definition
Thoracic/Lumbar
Term
Explain how the adrenal medulla is a unique in its sympathetic pathway?
Definition
Preganglionic neurone stimulates the adrenal medulla directly to release adrenaline into the blood stream. (There is no postgnglionic neurone)
Term
What are the four neurotransmitters involved in the ANS?
Definition
Acetylcholine, nradrenaline, arenaline and NANC
Term
What are the two types of synapses involved in the ANS?
Definition
Cholinergic and adrenergic
Term
What are the two types of cholinergic synapses?
Definition
Nicotinic and muscarinic
Term
What are the two types of adrenergic synapses?
Definition
Alpha and Beta
Term
Which PNS pathway/s contain ganglia for nictotinic synapses?
Definition
Sympathetic and parasympathetic pathways
Term
What do nictonic synapses stimulate?
Definition
The neuromuscular junction
Term
What molecule inhibits nictonic synapses?
Definition
Curare (Arrow Poison)
Term
Which PNS pathway/s contain ganglia for muscarinic synapses?
Definition
Parasympathetic Pathway
Term
What molecule inhibits muscarinic synapses?
Definition
Atropa Belladonna (deadly nightshade)
Term
Which molecule affects alpha1 postsynaptic adrenoreceptors more?
Definition
Noradrenaline
Term
Which molecule affects alpha2 presynaptic adrenoreceptors more?
Definition
Adrenaline
Term
What molecule inhibits alpha adrenoreceptors synapses?
Definition
Phentolamine
Term
What do alpha1 postsynaptic adrenoreceptors do?
Definition
Initiate vasoconstriction
Term
What do alpha2 postsynaptic adrenoreceptors do?
Definition
Reduce transmission of adrenergic and cholinergic synapses
Term
What molecule inhibits beta adrenoreceptors synapses?
Definition
Propranolol
Term
What do beta1 adrenoreceptors do?
Definition
Increase the heart rate
Term
What do beta2 adrenoreceptors do?
Definition
Vasodialation
Term
Which molecule affects beta1 adrenoreceptors more?
Definition
Both equally affetced by adrenaline and noradrenaline
Term
Which molecule affects beta2 adrenoreceptors more?
Definition
Adrenaline
Term
What are the six functions of blood?
Definition
1)Transport
2)Body temperature maintenance
3)Control pH
4)Removal of toxins
5)Regulation of ions
6)Regulation of blood clots
Term
What three cells are present in the blood?
Definition
Erythrocytes, Leukocytes and Thrombocytes
Term
What percentage of the body is blood?
Definition
8%
Term
What is plasma?
Definition
The fluid part of blood that carries cells and ions etc.
Term
What is serum?
Definition
The fluid part of the blood after all the cells and proteins etc. have been removed
Term
What percentage of blood is plasma?
Definition
55%
Term
What percentage of blood are erythrocytes?
Definition
44%
Term
What percentage of blood are leuokocytes?
Definition
1%
Term
What is a persons haematocrit?
Definition
The percentage of total blood volume occupied by red blood cells
Term
What is a normal haematocrit for men?
Definition
45%
Term
What is a normal haematocrit for women?
Definition
42%
Term
After blood has been centrifuged what are the three layers?
Definition
The plasma, buffy coat and haematocrit
Term
What does the buffy coat contain?
Definition
White blood cells
Term
What are the five components of plasma?
Definition
Water, ions, organic moleucles, vitamins and gases
Term
What are the five types of organic molecule in the plasma?
Definition
Amino acids, proteins, glucose, lipids, wastes
Term
What are the three types of plasma proteins?
Definition
Albumins, globulins and fibrinogen
Term
What percentage of plasma is water?
Definition
90%
Term
Why is it good that a large volume of plasma is water?
Definition
The water is able to hold heat more easily and so body temperature can be maintained
Term
What is the function of erythrocytes?
Definition
To carry oxygen to the body cells
Term
Name and explain two examples of an erythrocyte?
Definition
Biconcave shape = large surface area
Thin cell membrane = rapid diffusion of oxygen
Term
Why do erythrocytes not respire the oxygen?
Definition
They have no mitochondria so cannot undergo respiration
Term
What is the life span of an erythrocyte?
Definition
120 days
Term
Which sex has the higher concentration of erythrocytes?
Definition
Males
Term
What are microcytic erythrocytes?
Definition
Small red blood cells that are found in iron deficient anaemia
Term
What are macrocytic erythrocytes?
Definition
Small red blood cells that are found in folate deficient anaemia
Term
What is the composition of haemoglobin?
Definition
Four chained globin molecules + four haem groups
Term
Which ion is present in the haem group of haemoglobin?
Definition
Iron
Term
What are the four types of globin protein chains?
Definition
Alpha, beta, gamma and delta
Term
What is a porphyrin ring?
Definition
The group that holds the iron ion in the haem group
Term
Which globin chains are found in normal humans?
Definition
Two alpha and two beta
Term
Which globin chains are found in foetuses?
Definition
Two alpha and two gamma
Term
What colour is haemoglobin when oxygenated?
Definition
Red
Term
What colour is haemoglobin when deoxygenated?
Definition
Blue
Term
How many molecules of oxygen can be carried by each iron atom?
Definition
One
Term
What two factors affect haemoglobins ability to bind oxygen?
Definition
Partial pressure of oxygen and the number of free binding sites for oxygen
Term
What is the name given to haemoglobin when oxygen is bound?
Definition
Oxyhaemoglobin
Term
Where is haemoglobin at 100% saturation?
Definition
At the lungs
Term
Where is haemoglobin at 25% saturation?
Definition
At resting tissues
Term
When will the haemoglobin saturation fall below 25%
Definition
During exercise
Term
Is the relative strength of oxyhaemoglobin stronger or weaker than that of carboxyhaemoglobin?
Definition
STronger
Term
What percentage of venous blood is CO2?
Definition
23%
Term
How does haemoglobin resist changes to pH during high levels of CO2?
Definition
Acts as a buffer by absorbing the excess H+ ions from carbonic acid
Term
Is the relative strength of oxyhaemoglobin stronger or weaker than that of carbomonoxyhaemoglobin?
Definition
Weaker
Term
What are the two abnormalities is haemoglobin production?
Definition
Haemoglobinopathies and Thalassaemias
Term
What causes haemoglobinopathies?
Definition
Abnormal haemoglobin chains
Term
What causes thalassaemias?
Definition
Decreased production of haemoglobin chains
Term
Give an example of haemoglobinopathies?
Definition
Sickle cell anemia
Term
What are the two types of thalassaemias?
Definition
Alpha-thalassaemias and Beta-thalassemia
Term
What causes sickle cell anemia?
Definition
A mutation in a beta chain from glutamic acid to valine
Term
How do sickle celled erythrocytes destroy the malaria parasite?
Definition
By producing high levels of superoxide and hydrogen peroxide which is very toxic
Term
What are the two possible causes of thalassemia
Definition
Deletion of globin genes or a mutation in gene expression
Term
What happens in alpha-thalassemia?
Definition
Production of alpha-globulin is defective
Term
What happens in beta-thalassemia?
Definition
Production of beta-globulin is defective
Term
What defines a blood group?
Definition
The antigens (glycolipids/proteins) on the surface of the erythrocyte
Term
What is a complete blood group?
Definition
The 29 antigens on the surface of an individuals erthrocyte
Term
What are the four alleles in the ABO blood group system?
Definition
A, B, H and h
Term
Which is the dominant allele in the ABO blood group system?
Definition
H
Term
What does the H allele code for?
Definition
A transferase that converts a precursor substance into H substance
Term
What does an individual with a HH genotype produce?
Definition
H substance
Term
What does an individual with a Hh genotype produce?
Definition
H substance
Term
What does an individual with a hh genotype produce?
Definition
No H substance
Term
What is the Bombay phenotype?
Definition
hh
Term
What does the Bombay phenotype mean?
Definition
Despite the possession of an A or B allele the erythrocyte will not have ABO blood grouping because no substance H is present
Term
What does the A allele code for?
Definition
N-acetyl galactosamine
Term
What does the B allele code for?
Definition
Galactose
Term
What does the AB genotype mean?
Definition
They posses both the A and the B antigens
Term
What does the O allele code for?
Definition
Nothing (The individual would just have substance H)
Term
What is the relationship between blood group and location?
Definition
Patches of the earth tend to have similar blood groups e.g UK is mainly O
Term
An individual that produces A substance will produce which antibodies?
Definition
Beta
Term
An individual that produces B substance will produce which antibodies?
Definition
Alpha
Term
An individual that produces just H substance will produce which antibodies?
Definition
Alpha and Beta
Term
An individual that produces both A and B substance will produce which antibodies?
Definition
No antibodies
Term
What is an agglutinogen?
Definition
Another name for the blood group antigens
Term
What is an agglutinin?
Definition
Another name for the antibodies against the blood group antigens
Term
Which blood group is the universal donor?
Definition
O
Term
Which blood group is the universal recipient?
Definition
AB
Term
Which antigen in the Rhesus group is the most common/important
Definition
The D antigen
Term
Is an individual has the genotype DD they are said to be what?
Definition
Rh+
Term
Is an individual has the genotype dd they are said to be what?
Definition
Rh-
Term
Is an individual has the genotype Dd they are said to be what?
Definition
Rh+
Term
What is the Rhesus antigen problem?
Definition
If the mother of a baby is Rh- and the baby is Rh+ the mother will produce antibodies against the baby. This will not kill the first child but may kill a subsequent child due to the presence of her antibodies
Term
How do we clinically get round the Rhesus antigen problem?
Definition
Rh- mothers are given an injection of Anti-D immunoglobulin hat will remove the babies Rh+ blood before she can make anti-D antibodies
Term
How does a mother react to a different ABO blood group?
Definition
The mother makes IgM's but they do not cross the placenta so the baby is unaffected
Term
What are platelets?
Definition
Fragments of megakaryocytes used to clot blood
Term
Which organelle does a platelet lack?
Definition
A nucleus
Term
What two important properties do platelets have to aid clotting?
Definition
It can secrete products and contract
Term
What is haemostasis?
Definition
The arrest of bleeding from a broken blood vessel
Term
What are the three steps of haemostasis?
Definition
Vascular spasm, formation of the platelet plug and blood coagulation
Term
What happens during the vascular spasm stage of haemostasis?
Definition
Platelets/damaged cells release vasoconstrictors that cause the smooth muscle of the vessel to constrict to stopping blood flow. Due to the vasoconstriction the endothelial layers adhere to eachother
Term
Name the two vasoconstrictors released by platelets?
Definition
ADP and serotonin
Term
What happens during the formation of the platelet plug during haemostasis?
Definition
1. Platelets adhere to the exposed collagen of the damaged lining.
2. vWF is released by the platelets to aid the adhesion of platelets together 3. Thromboxane A2 is secreted to cause nearby platelets to adhere
4.Prostacyclin is released to limit the size of the platelet plug
Term
What does vWF stand for?
Definition
von Willebrand's Factor
Term
What are the four functions of the platelet plug?
Definition
Seal the break, strength of the wall, vasoconstriction and secretion of chemicals to aid cloting
Term
What is a thrombus?
Definition
A blood clot
Term
What are the two pathways involved in blood clotting?
Definition
The intrinsic and the extrinsic pathway
Term
What stimulates the intrinsic pathway?
Definition
The exposure of collagen
Term
What stimulates the extrinsic pathway?
Definition
The blood contact with damaged external blood tissue causing the release of tissue factor
Term
Outline the intrinsic pathway?
Definition
1. Exposure of collagen converts Factor XII into active Factor XII
2. Production of active Factor XII produces Ca2+ ions that converts Factor XI into active Factor XI
3. Production of active Factor XI produces Ca2+ ions that convert Factor IX into active Factor IX
4. Active factor IX combines with Factor VIII to produce Ca"+ ions and PL which converts Factor X into active Factor X
Term
Outline the extrinsic pathway?
Definition
1. Damage of external tissue causes the conversion of Factor VII which creates Tissue Factor (Factor III) and Active Factor VII
2. Tissue factor and Active Factor VII then activate step 3 of the intrinsic pathways and releases Ca2+ and PL to convert Factor X into active Factor X
Term
Outline the positive feedback of the extrinsic pathway?
Definition
Production of Factor X restarts the extrinsic pathway at step 1
Term
Outline the positive feedback of the intrinsic pathway?
Definition
Production of thrombin restarts the intrinsic pathways at step 2
Term
Outline the common pathway?
Definition
1. Production of active Factor X releases Ca2+ ions, Factor V and PL to convert Prothrombin into thrombin
2. Prothrombin converts Fibrinogen into Fibrin and converts Factor XIII into active Factor XIII
3. The presence of active Factor XIII and Ca2+ converts fibrin into cross-linked fibrin
Term
What are the two anticlotting processes?
Definition
Production of Anti-thrombin and the producion of Thrombomodulin, protein C and S
Term
What does the production of anti-thrombin do?
Definition
Inhibits the clotting factors, including thrombin
Term
Which molecule enhances the work of anti-thrombin?
Definition
Heparin
Term
What does the production of Thrombomodulin and protein C and S do?
Definition
Thrombomodulin bind to thrombin to inhibit its effects and activate proteins C and S. protein S then binds to protein C to inhibit Factors Va and VIIIa
Term
What do fibroblasts do?
Definition
Form scar tissue to heal the wound
Term
What recruits fibroblasts?
Definition
Growth Factor Beta
Term
Which enzyme dissolves the healing clot?
Definition
Plasmin
Term
What is thromboembolism?
Definition
The blockage of a blood vessel due to an un-removed clot
Term
Outline the mechanism of Fibrinolysis?
Definition
1. Plasminogen is converted to plasmin by plasminogen activators
2. Plasmin converts fibrin into soluble fibrin fragments
Term
What secretes the plasminogen activators?
Definition
The endothelial cells
Term
What is Contusion?
Definition
Bruising
Term
What causes contusion?
Definition
Bleeding under the skin causing clots in the tissue
Term
How is contusion stopped?
Definition
Production of plasmins
Term
What four things can cause thromboembolism?
Definition
Athersclerosis, imbalances in the clotting system, slow moving blood and the release of thromboplastin from traumatized tissue
Term
What happens when 75% of the lumen vessel is blocked?
Definition
Hypoxia
Term
What happens when 90% of the lumen vessel is blocked?
Definition
Anoxia
Term
What are the four inherited disorders of haemostasis?
Definition
Structural defects, quantity/quality of the platelets, deficiency of coagulation factors and thrombotic disorders
Term
What is the most noticeable sympton of a platlet disorder?
Definition
Petechiae (pin point red spots)
Term
What causes thrombotic thrombocytopenic purpura?
Definition
Low platelets numbers in area of lots of small clots
Term
What are the symptoms of thrombotic thrombocytopenic purpura?
Definition
Dark red/black blotch bruising
Term
What causes is von Willebrand's Disease?
Definition
Deficiency of vWF so easily bleeding
Term
What causes Haemophilia A?
Definition
Deficiency in factor VII
Term
What causes Haemophilia B?
Definition
Deficiency in Factor IX
Term
What are the four acquired disorders of haemostasis?
Definition
Hepatic disease, Vitamin K deficiency, renal disease and Drug induced disorders
Term
What are the main two anticoagulants?
Definition
Warfarin and Heparin
Term
When is an patient prescribed Warfarin?
Definition
When they are deficient in vitamin K
Term
When is a patient prescribed Heparin?
Definition
When they have serious internal blood clotting
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