Cardiovascular Sytsem

Question 1

Whats the difference between michaelis-menten kinetics and allosteric enzymes?

Answer 1

Michaelis-menten - Both forward and reacion reaction increased equally. Only catalytic constant changes, not rate constant. Rate only increases up to certain substrate conc.

Allosteric - binding site remote to actvive site to allow effectors resulting in change in affinity at binding site (possible due to quaternatry structure). Allosteric inhibitors will stabilise T state, activators stabilise R state.

Question 2

Define a Co-factor & Co-enzyme

Answer 2

CoFactor - Non-protein compound that must be bound tightly (prostetic group) or loosely (coenzyme) for enzyme to function

CoEnzyme - CoFactor that binds reversibly to enzyme to activate it. Chemically changed during reaction so are also known as cosubstartes.

Question 3

what are subaceous glands?

Answer 3

Glands found in the skin, secreting an oily/waxy matter making skin slightly acidic

Question 4

What are keratinocytes?

Answer 4

Predominant cells in epidermis. Forms barrier against pathogens. Has Toll like receptors (TLRS) which detect PAMP’s, leading to the release of cytokines & chemotaxis

Question 5

What are the atrioventricular valves abnd what are their role?

Answer 5

Tricuspid and Mitral (bicuspid). Located between atria and ventricles preventing a backflow of blood during systole.

Chordae tendineae and papillary muscles ensure valve doesnt prolapse, known as subvalvular apparatus.

Question 6

What are semilunar valves and what are their purpose?

Answer 6

Aortic and Pulmonary. Located at the base of the pulmonary trunk. Permits blood flow into arteries but prevents backflow into ventricle

Question 7

Whats the role of the cardiac skeleton?

Answer 7

Provides structural integrity while also providing a non conducting tissue between atria and ventricles. This allows independant contraction of the two structures.

Question 8

What is the lymphatic system?

Answer 8

Open system collecting fluid that diffuses out of blood vessels at capillary beds. Forms lymph, which eventually is returned back to blood vessels.

Question 9

How are myocytes electrically coupled together?

Answer 9

Via gap junctions provided by intercolated disks. Allows muscle to act as a syncitium.

Question 10

What is the purkinje system?

Answer 10

Specialised conducting fibres which are able to conduct cardiac action potentials quicker and more efficiently than any other cardiac cell. Allows for synchronised ventricle contraction, essential for maintaining heart rhythm.

Question 11

What are the differences between a ventricular action potential (fast) and a pacemaker potential (slow).

Answer 11

• Resting potential less negative with pacemaker, therefore less depolarising required to reach threshold
• Ca+2 repolarise in ventricular AP’s whereas k+ repolarise Pacemake AP’s
• Peak tension in ventricular AP’s occurs at the end of repolarisation preventing cramp/tetanize. Whereas skeletal muscles peak tension occurs long after repolarisation, allowing multiple AP’s to occur leading to summation and prolonged muscle contraction.

Question 12

What are the stages of the cradiac cycle?

Answer 12

1) Atrial systole - atria contract, topping up filled ventricles
2) Isovolumetric contraction - Ventricles contract, valves closed
3) rapid ejection - Semilunar valvesopen, ventricles expel blood
4) reduced ejection - Semilunar valves still open & ventricles contract
5) isometic relaxation - Ventricles relax, all valves close
6) rapid ventricular filling - Atrioventricular valves open, blood fills ventricles
7) Diastasis - ventricles fil. slows as venouse pressure>ventricular pressure

Question 13

What does a Electrocardiogram Measure (ECG)?

Answer 13

detects potentials from the purkinje system. This is the only current that reaches the surface of the skin. Doesnt detect potentials from AV or SA nodes.

Question 14

How do you calculate cardiac output ?

Answer 14

CO = HR x SV

HR - heart rate

SV - Stroke volume

Question 15

Define the terms Preload, afterload & cardiac output..

Answer 15

Cardiac ouput - Volume of blood pumped into aorta

Preload - End diastolic volume that stretches the ventricles

Afterload - Pressure in L ventricle after contraction

Question 16

How does autonomic nerves system influences heart…

Answer 16

Parasympathetic - vagus nerve inervated, ACH released slowing HR (acting on SA node). also increases refractory period and decreases AV conduction.

Sympathetic - Noradrenaline release increasing heart rate & increases the amount of Na+ leak channels that are open so threshold reached quicker. Also decreases refractory period and increases AV conduction.

Question 17

How does Ach have an indirect effect on ventricular myocytes?

Answer 17

Works to inhibit the presynaptic release of noradrenaline

Question 18

what is starlings theory ?

Answer 18

Right and left cardiac output must be equal under normal conditions. Stroke volume of heart increases in response to volume of blood filling the heart. This is becuase the increase in stretch of the ventricles due to increase volume causes cardiac muscles to contract more forecefully. Allows increase in CO (SV+) without increasing HR.

Question 19

How do u calculate mean arterial pressure?

Answer 19

MAP = CO x TPR (Total peripheral resistance)

Question 20

What are Baroreceptors?

Answer 20

Non-encapsulated nerve endings in adventitia of arteries ( Aortic arch & carotid sinus). Axons terminate in the medulla oblongata.

Question 21

Describe flow diagram of Baroreceptor pathway..

Answer 21

Question 22

What are atrial receptors?

Answer 22

Low pressure strech receptors in the walls of the atria, sesnitive to volumes.

Question 23

Decribe the haemorrhage Flow diagram …

Answer 23