Cardiovascular Flashcards
What are the 3 basic cell types in the heart?
Cardiac muscle cells, purkinje cells and nodal cells.
What are cardiomyocytes composed of and how are they connected to each other?
They majority of them are composed of myofilaments and mitochondria, and joined together by intercalated discs.
List the 3 types of basic cell types located in the heart in terms of decreasing propagation velocity.
Purkinje cells = 120cm/sec
Cardiomyocytes = 70cm/sec
Nodal cells = 20cm/sec
Where are nodal cells located? And how are they connected to each other
The two nodes in the heart: SAN & AVN
They are connected via gap junctions
Define ‘inotropic’ and give both exogenous and endogenous examples.
An inotropic substance is something that affects the force of cardiac contraction; positive inotropic agent = increased force of myocardial contraction
Eg catecholamines and digoxin
Define ‘chronotropic’ agents. Name an example.
Substances that affect HR (e.g. adrenaline, atropine)
Define ‘lusitrophy ‘
Rate of myocardial relaxation
Where is the vagus motor nucleus located?
Brainstem; medulla
The vagus nerve (CNX) has parasympathetic control over the CV system; true or false?
True
What receptors do catecholamines use in the heart and what is their effect?
NA & adrenaline use beta1-adrenoceptors in the hearts
Once stimulated, the activity of adenylyl cyclase increase = increased intracellular conc. of cAMP = stimulation of If = increased rate of depolarisation of pacemaker
What receptors does the ACh released from parasympathetic fibres target in the heart and what is their effect?
They use M2-muscarinic receptors
They reduce the activity of adenylyl cyclase = decreases of intracellular conc. of cAMP = decreases of no. Of active Ca2+ channels = decreased hyperpolarisation = activates inwardly rectifying potassium channels
RESULTS IN negative chronotropy and inotropy
Define end diastolic volume
Volume of blood in ventricles before contraction
Define ‘preload’
The end diastolic pressure, which is stretching the wall of the ventricles to their greatest geometrical dimensions
Define stroke volume
Volume of blood ejected from the heart over heart beat
Describe the Frank-Starling mechanism.
A greater EDV would increase the contractile strength of the ventricles (i.e. myocardiocytes) and will increase stroke volume
Increase EDV = increase contractile strength = increase SV
The reason behind this is that the myocardium will be more stretched due to a greater volume, therefore, their increased sacrilege length results in increased sensitivity to Ca2+ = munch stronger contraction
Describe the Anrep effect
Increased arterial pressure (due to vasoconstriction) causes a slow increase in contractility
How much blood runs through the average adult?
5-6L
What proteins are found in blood (plasma)?
Albumins, globulins and fibrinogen
What is the action of albumins in blood?
To help regulate the osmotic pressure to keep blood inside the vessels
What protein in blood is essential for the blood clotting mechanism
Fibrinogen
Define haematocrit and note the difference between the 2 sexes
The number of RBC/erythrocytes an individual possesses. Women have a slightly lower haematocrit of 3.9-5.8x10^12/L compared to Men of 4.5-6.5x10^12/L due to menstruation.
What is the average diameter of a RBC?
7.2micrometers
What are the 2 types of leukocytes in blood?
Agranulocytes and granulocytes
What is a unique characteristic of a neutrophil’s organelles that makes it easier to distinguish in an histology slide?
It’s 2-5 lobed nucleus: the more lobes = more mature
What type of granules are found in platelets and important for coagulation?
Alpha-granules
Define ‘haematopoiesis’ and where does this process occur?
The production and replacement of the formed elements in the blood that occurs in the bone marrow.
What define blood type?
The surface antigens that are present/absent.
What can occur is there is the wrong blood type used for an individual during a blood transfusion?
Blood agglutination = where the blood begins to clump together
What are the 3 steps taken of blood homeostasis following tissue damage/blood vessel damage?
- Vasoconstriction
- Formation of platelet plug (via collagen fibres)
- Coagulation (via fibrin)
What muscle mediates vasoconstriction?
Vascular smooth muscle
What 3 factors promote vasoconstriction?
- Sympathetic nervous system (immediate response)
- Enodthelin
- Platelets
What do serotonin and thromoboxane A2 promote?
Vasoconstricton
What receptor does fibrinogen bind to?
An active IIa/IIIb receptor complex (n.b. Activated by release of ADP)
What prevent blood coagulation in storage (e.g. blood banks)
The addition of chelatin agents and sodium citrate to blood.
What convert plasminogen to Plasmin? And what type of cell secretes it?
Tissue-type plasminogen activator secretes by endothelial cell’s
How is cardiac output calculated?
CO = HR x SV
How is mean arterial pressure calculated?
MAP = CO x TPR
Define ‘transmural pressure’.
Pressure exerted across the vessel wall
Coronary vessels compress during systole; true or false?
True; this can be problematic as it can reduce blood flow to cardiac tissue
What percentage of the cardiac output does the brain receive?
14%
What is the function of the Circle of Willis?
To ensure that cerebral flow is preserved even when a major cranial artery becomes blocked; lessens the extent of damage of reduced blood flow
What is the primary mediator of cellular contraction?
Increased intracellular levels of Ca2+
What does the Ca2+.Calmodulin complex activate in smooth muscle contraction?
Myosin light chain kinase (MLCK) that adds a phosphate group to myosin and the cross-bridge cycle starts.
What enzyme stops smooth muscle contraction via removing the phosphate group from myosin?
Myosin phosphatase
What volume of the respiratory tract is considered as ‘dead space’?
The upper respiratory tree; 0.15L
Name the 3 layers of alveolus.
Alveolar epithelium, interstitial space and capillary endothelium
What is the diffusion distance of alveoli?
0.2-0.6 microm
State the barometric pressure of air.
760mmHg
How do you calculate the amount of O2 transported in the dissolved form via blood?
Dissolved oxygen (mlO2/L) = 0.03 (solubility constant) - PO2
State Henry’s Law.
The amount of gas dissolved in a solution is directly proportional to the pressure of the over over the solution
How many subunits does the red blood pigment Haemoglobin contain? What is the component of each subunit?
4; each contains a polypeptide chain, haem-group (each haem group has a Fe atom which O2 binding sites)
What shape does the myoglobilin O2 dissociation curve have?
Hyperbolic curve
What 3 ways is CO2 carried in the blood and what type is most prevelant?
5% as dissolved CO2
5% attaches to Hb and other blood proteins
90% as bicarbonate ions
Describe the Haldane Effect.
The effect by which the combination of O2 with Hb displaces CO2 from Hb
What are the 2 main muscles control quiet breathing inspiration?
Diaphragm and the external intercostal muscles
What are the accessory muscles responsible for inspiration during exercise?
Sternocleidomastoid, Serratos anterior and pectoralis
What controls expiration during quiet breathing?
Passive, no muscles and elastic fibres.
What muscles are responsible for expiration during exercise?
Internal intercostals and the abdominal muscles: obliques, transversus & rectus
What determines gas distribution in the bronchioles?
The muscle tone of the smooth muscle of the bronchioles
Define translung pressure.
The pressure difference between the alveoli and pleural space
Define transorgan pressure
The pressure difference between the alveoli and the atmosphere
Where in the lungs has a higher ventilation(V)/perfusion(Q) ratio?
The lower lung has a higher V/Q ratio as perfusion is higher compared to ventilation
List the 3 steps of a cough.
- Breathe in to make a force that will pick up any debris and force it out the body via the mouth
- The glottis is then closed and you breathe out to build the pressure
- When the pressure is high enough, the glottis is forced open = a cough
