The intracellular compartment contains approximately
25-28 L of fluid.
The third space is the space in the body where fluid does not usually collect, examples include the
peritoneal and pleural cavities.
The action potential can be summarized as follows:
1. Resting potential. Small subset of potassium channels open, permitting K+ to enter and exit the cell based on electrochemical forces. There is no net movement of K+ ions.
2. Threshold. As a depolarizing stimulus arrives a few Na+ channels open allowing Na+ ions to enter the neurone. The increase in positive ions inside the cell depolarized the membrane potential and brings it closer to the threshold at which the action potential is generated ( -55mV).
3. Depolarisation phase. After the threshold potential is reached additional voltage gated sodium channels open and Na+ ions rush into the cell. The voltage across the membrane rapidly reverses and reaches its most positive value.
4. Repolarisation phase. At the peak of the action potential, two processes occur simultaneously. Many of the voltage-gated sodium channels begin to close and more potassium channels open. This allows positive ions to leave the cell and causes the membrane potential to shift back towards the resting membrane potential. As the membrane potential approaches the resting potential the potassium channels channels are maximally activated and open.
5. Hyperpolarisation phase. The membrane potential then hyperpolarizes beyond the resting membrane voltage as more potassium channels are open at this point than during the membranes resting state, allowing more positively charged potassium ions to leave the cell.
6. Recovery. A return to steady state occurs as the additional potassium channels opened during the action potential close. The membrane potential is now determined by the subset of potassium channels that are normally open during the membranes resting state.
The velocity of the action potential increases with
increasing axonal diameter.
The velocity also increases if the neurone is myelinated.
The following factors promote gastric emptying:
Increased food volume in the stomach
Parasympathetic innervation (via the vagus nerve)
Prokinetics such as metoclopramide and erythromycin
Proteins empty fastest and fats slowest
Prolongation of the QT interval can be caused by
NON-sedating antihistamine drugs such as terfenadine and astemizole.
Cocaine increase QT intervals ?
acute intoxication but not in chronic abuse.
Decreased oxygen tension causes
vasodilatation of arterioles.
Locally released serotonin causes
vasoconstriction of arterioles.
An area with no ventilation is termed a
An area with no perfusion is termed
This is the ideal V/Q.
At approximately 2/3 of the way up the chest the V/Q = 1.
At the apex the V/Q =
V/Q = 3
and at the base V/Q = 0.6.
V/Q = 0.6.
The criteria for the systemic inflammatory response syndrome are:
Temperature < 36°C or > 38°C
Heart rate > 90 bpm
Respiratory rate > 20/min or PaCO2 < 4.3 kPa
White cell count < 4 x 109/l or > 12 x 109/l (or 10% bands)
ECG criteria for LVH have good
specificity but poor sensitivity for actual left ventricular hypertrophy.
Many people who actually have LVH do have ECGS which reveal it.
The Sokolow-Lyon index is positive for LVH if the
S wave in V1 plus the R wave in V5 or V6 > 35 mm (7 large squares).
LVH is present if the R wave in aVL is greater than
EKG vs Echocardiography LVH?
Echocardiography-> gold standard for diagnosis of LVH.
P mitrale is indicative of
· left atrial enlargement-> delay in left atrial activation,->broad, bifid or notched P wave
· ECG changes are most prominent in the inferior leads.
P mitrale is typically caused by
· mitral regurgitation, which results in left atrial enlargement.
Vitamin D is metabolized in the kidney to
Renin is produced by the
juxtaglomerular apparatus and promotes the formation of angiotensin.
Erythropoietin in synthesized by
Interstitial cells in the renal cortex. It is a hormone that regulates red blood cell production.
PTH reduces re-absorption of
phosphate in the proximal convoluted tubule.
Thiazide diuretics inhibit re-absorption of
Na and Cl ions in the distal convoluted tubule
blocking the thiazide sensitive Na/Cl co-transporter.
A polysnaptic reflex occurs when more than one synapse connects the afferent (sensory) and efferent (motor) signals. Examples of polysynaptic reflexes include:
Pupillary light reflex
The following are the classic criteria of left anterior fascicular block on ECG:
Dominant negative deflection of QRS complex in lead II (i.e. axis < -30°)
Q waves in lead I and aVL
R waves in leads II, III and aVF
are ECG criteria for LBBB:
Widened QRS (> 0.12 seconds)
RSR pattern in V4-V6
Q wave in V1
Dominant R wave in V6
Upright and notched lead I (M pattern)
The commonest causes of LBBB are:
Coronary artery disease
The third heart sound can be physiological in
children where it is due to the presence of a supple ventricle that can undergo rapid filling.
When heard in older adults ->sign of increased ventricular filling secondary to disease such as heart failure or mitral regurgitation.
The fourth heart sound is due to conditions which cause
stiffness of the ventricles.
EDRF (nitric oxide) is produced and released by the endothelium to promote
smooth muscle relaxation.
released in response to <- calcium, bradykinin and histamine, and also in response to painful stimuli.
Endothelin-1 is a potent
vasoconstrictor released by the endothelium.
Thromboxane A2 is a potent
vasoconstrictor released by the endothelium.
The kidneys receive approximately
1.2 L of blood flow per minute
20-25% of the cardiac output.
The blood flow in the renal cortex is approximately
20 times greater in the renal cortex than in the medulla.
The kidney is approximately
11-14 cm in length
6 cm wide
4 cm thick.
The intracelleular compartment contains approximately
25 L of fluid.
the extracellular compartment contains approximately
Lymph is an example of an
Transcellular fluids are fluids that are formed from the transport activities of cells. Examples include:
CSF, GIT fluids, bladder urine, aqueous humour and joint fluids.
The normal value of the CVP is
The tip of the catheter must be in the
junction between the superior vena cava and the right atrium.
Cannon a waves are very large a waves that occur when the right atrium contracts against a closed tricuspid valve. They occur in:
Complete heart block
Both gelofusine and 0.9% saline contain
154 mmol/l of sodium.
125 mmol/l of chloride compared with 0.9% saline which contains 154 mmol/l.
molecular weight 30,000.
The average molecular gelatine weight of gelofusine is
Regarding class II haemorrhage in a 70 kg male:
750-1500 mL of blood would have lost.
pulse rate 100-120 with a normal blood pressure.
Urinary output is only mildly affected and usually in the region of 20-30 mL/hour.
pulse pressure is usually decreased.
respiratory rate 20-30.
Cerebral perfusion pressure (CPP) = mean arterial pressure (MAP) intracranial pressure (ICP). CPP is reduced by:
High pCO2 (due to resultant vasodilatation)
Regarding the electrical basis of cardiac contractility
Cell membrane potentials are determined primarily by 3 factors.
? These are the concentrations of ions inside and outside the cell.
? The permeability of the cell membrane to those ions through specific ion channels.
The activity of electrogenic pumps.
The first phase of a cardiac action potential is a rapid rise in sodium permeability.
The second phase in a cardiac action potential is a rapid fall in sodium permeability and a slight rise in potassium permeability.
The resting membrane potential of a ventricular myocyte is
An increase in cardiac output can generally be attributed to an increase in
Alkalosis is a
negative inotropic factor.
The effect of increased sarcomere length on the contractile proteins is termed
Terminal arterioles/Post capillary venules are small vessels measuring
Albumin generates about
70% of oncotic pressure.
In most capillary systems of the body there is a net filtration of fluid of about --% from the intravascular compartment to the extravascular compartment.
Normal coronary blood flow is around
200ml/minute at rest.
Coronary blood flow may increase up to 5 times during exercise.
5 times during exercise.
An increase in carbon dioxide leads to cerebral
An increase in potassium leads to cerebral
Regarding skeletal muscle blood flow
At rest it accounts for approximately 20% cardiac output.
During swallowing the nasopharynx is
It is sealed by elevation of the soft palate
superior constrictor muscle contraction.
The primary peristaltic wave forces the food bolus down the oesophagus into the stomach in a wave that last approximately
gastric emptying and gastric acid secretion.
Each villus is approximately
0.5-1.6 (millimetres) in length.
An example of secondary active transport is the glucose symporter SGLT1, which co-transports
one glucose molecule into the cell for every two sodium ions it imports into the cell.
The Thin descending Henle displays a high permeability to
water and solutes
20% of water resorption
The normal value for arterial blood pH is
The normal value for arterial blood PaCO2 is
The normal level for total serum calcium is
calcium that enters the body in a normal diet is absorbed by the small intestine.
About 40% is absorbed
The pituitary gland weighs approximately
Head trauma is the cause of neurogenic diabetes insipidus in
17% of cases.
Small cell lung cancer is a common cause.
Symptoms of SIADH include
headache, nausea, vomiting, convulsions and coma.
Management of SIADH includes the use of
The combined weight of the adrenal glands ranges from
Regarding Cushings syndrome Patients often suffer with psychological disturbances such as
euphoria and psychosis.
Anxiety and depression are also common.
the most common non iatrogenic cause of Cushings syndrome.
Antifungal treatment for Cushings syndrome.
Ketoconazole->It inhibits cortisol synthesis but is of limited efficacy.
Regarding phaeochromocytoma may be familial.
Up to 25% may be familial.
Delta cells of the pancreas secrete
Proinsulin ->insulin by
In the maturation of insulin there is release of a fragment termed the
Insulin acts to increase the
secretion of hydrochloric acid by parietal cells in the stomach.
cholecystokinin stimule vs inhibit-> Glucagon
increased urea production-> stimule vs inhibit-> Glucagon
Regarding IDDM male/female incidence
There is an equal incidence in males and females.
NIDDM accounts for --% of cases of diabetes.
90% of cases.
Regarding NIDDM The pathophysiology includes an
inability of cells to respond to normal levels of insulin i.e. they are insulin resistant.
A fasting blood sugar of > 7mmol/L suggests the diagnosis.
The primary mechanism of action of metformin is
---> suppress glucose production by the liver.
also Increasing insulin sensitivity is an important action
Efferent arteriole is narrower vs widther than the afferent,
Narroweer ->creating a capillary hydrostatic pressure of about 7.3kPA.
Glomerular Filtration->The osmotic pressure of the blood is around
4kPA and is provided mainly by plasma proteins.
Glomerular Filtration Less than --% of the glomerular filtrate is excreted as urine.
Atrial natriuretic peptide
decreases reabsorption of sodium and water from the Distal convoluted tubule and collecting ducts.
ACTH with highest levels at around
8am in the morning.
The release of thyroid stimulating hormone is at its highest in the
early evening is at its lowest
highest during the night.
Calcitonin is secreted by the
parafollicular C cells in the thyroid gland.
At the arterial end of a capillary the hydrostatic pressure is around
The osmotic pressure of the blood at the arterial end is around
Hydrostatic pressure at the venous end of a capillary is around
% of carbon dioxide in the blood is dissolved in the water of the plasma.
% of carbon dioxide in the blood is transported in combination with haemoglobin.
% of carbon dioxide is transported in the blood in the form of sodium bicarbonate.
The normal platelet count is between
200 and 350 x 109/L.
The lifespan of a platelet is between
8 and 11 days, after which time they are destroyed by macrophages mainly in the spleen.