Physiology Flashcards
Define flow
Volume per unit time
Define Reynolds number
Reynolds number is a dimensionless quantity that helps predict fluid flow patterns in different situations by measuring the ratio between inertial and viscous forces.
Basically predicts when flow through a tube is likely to change from laminar to turbulent
Which Reynold’s number is the turning point where laminar flow become turbulent
2000
What is the formula for Reynolds number
Re = pvD/μ
Reynolds number = Fluid density x Velocity x pipe diameter / dynamic viscosity of fluid
Why is turbulent flow useful in trachea
Droplets fly off in all directions hitting mucosa which allows them to be cleared
Define ohms law
V = IR
Describe course of RCA
Arises from anterior aortic sinus of aortic root and runs between right atrium and right ventricle
Describe course of LCA
Arises from left posterior sinus of aortic root then devides into circumflex and LAD.
Circumflex runs between left atrium and left ventricle
LAD runs between left and right ventricles
What percentage of CO goes to coronary blood flow
5%
Describe why exercise can trigger angina in terms of blood flow
CO can increase 4-7 fold during exercise whilst coronary blood flow only increases 3-4 fold
Why is turbulent flow important in the aortic root
Blood moving through aortic valve becomes turbulent which causes back flow into sinus valsalve and therefore into coronary arteries.
Describe the major venous drainage of the heart
Great and small cardiac veins coalesce into coronary sinus and drain into right atrium
Which vessels play a minor part in venous drainage of the heart
Thebesian veins- very small veins impeded in the myocardium which drain directly into each chamber separately
Which equation is used to calculate the transmembrane potential considering only 1 ion
Nernst equation
Which equation is used to calculate the transmembrane potential considering multiple ions
Goldman-hodgkin-katz equation
What is the Nernst equation
Pd = nRT/F X Ln (Ion o/ Ion i)
Potential difference = (Valence X Universal gas constant X Absolute temperature/ Faraday constant.) X Ln (outside conc./ Ion inside conc.)
What is the resting membrane potential of a neuron
-70mv
How long does an action potential last in a neuronal cell
1msec
How long does an action potential last in a cardiac myocyte
300msec
How do action potentials spread between cardiac myocytes
GAP junctions
Describe the 4 phases of the cardiac myocyte action potential
0- Na+ influx through fast channels and CA2+ influx through T-type channels - causing membrane depolarisation
1- Potassium outflow acts to repolarise
2- More Ca2+ influx via L-type channels prolongs action potential
3- Ca2+ channels close causing re-polarisation
4- Membrane stabilised at -85mV
How do pacemaker cells in SAN and AVN fire automatically
Continuous slow leak of ions causing action potentials to be triggered
Describe 3 phases of action potential in pacemaker myocyte
Phase 4- Slow Na+ inflow causing slight depolarisation to -40mV the threshold potential
Phase 0- Ca2+ influx via T-type channels causing depolarisation
Phase 3- K+ outflow repolarises membrame
Which ECG leads show inferior infarct (RCA)
Leads II, III, AVF
Which ECG leads show anterior infarct (LAD)
Leads V1 and V2
Which ECG leads show Lateral infarct (Circumflex)
Leads I, AVL, V5, V6
How is MAP calculated
MAP = Diastolic pressure + 1/3 pulse pressure
What causes dichrotic notch in aortic pressure wave
Aortic valve closing
Backflow around aortic valve
What is the normal pressure in the right atrium
< 5mmHg
What is the normal pressure in the right ventricle
<25/5 mmHg
What is the normal pressure in the pulmonary artery
<25/10 mmHg
What is the normal pressure in the Left atrium/ Pulmonary wedge pressure
< 12 mmHg
What is the normal pressure in the left ventricle
<130/10 mmHg
What is the normal pressure in the Aorta
<130/90 mmHg
Which 2 metabolic factors have largest impact on coronary artery vasoconstriction
increased PO2
Decreased PCO2
Define Hagen-pouseuille’s law
The volumetric flow rate of a fluid through a pipe is directly proportional to the fourth power of the diameter and the pressure difference, and inversely proportional to the pipe length and the fluid’s dynamic viscosity.
Give the Hagen-pouseuille’s equation
Q = △P π r⁴/8 η L
Flow = pressure difference X π X radius ⁴ / 8 X Viscosity of liquid X length of tube
Which 2 cranial nerves transmit action potentials from baroreceptors in heart
Glossopharyngeal (IX)
Vagus (X)
How do you calculate average weight of a child over 5 years old
Weight (kg) = (Age x3) + 7
Which agent is used to measure total body water
Deuterium Oxide (D2O)
Explain the Cushing’s reflex in acute head injury
Triad of: Hypertension, bradycardia, irregular respiration.
Caused by increased inter cranial pressure. Sign indicates imminent brain herniation
In what form is the majority of CO2 transported in the blood
Bicarbonate (90%)
Carbamino compound (5%)
Dissolved in plasma (5%)
Which 4 cranial nerves carry parasympathetic outflow
CN III
CN VII
CN IX
CN X
What are some of the signs of CNVII palsy (cerebellopontine tumour)
Ipsilateral facial weakness
Ipsilateral loss of taste
Ipsilateral loss of tear production and sweating
Explain how hypermagnesaemia (magnesium overdose) can cause muscle weakness
Magnesium competes for voltage gated calcium channels and prevents ACh vesicle exocytosis from presynaptic terminal
How does Zollinger Ellison disease cause gastric ulcers
Neuroendocrine gastrin producing tumour of G cells in pyloric region of stomach. Gastrin leads to HCL production by parietal cells which when unregulated causes multiple ulcers.
What do G cells produce in stomach
Gastrin ( causes parietal cells to produce HCL)
What do parietal cells produce in stomach
HCL
What do D cells produce in stomach
Somatostatin (acts to decrease gastrin production)
What do Chief cells produce in stomach
Pepsinogen- inactive pepsin which is a proteolytic enzyme involved in protein digestion
What do Enterochromafin cells produce in stomach
Histamine (triggers parietal cells to produce HCL)
Which 2 factors lead to closure of the ductus arteriosus
Increased oxygen tension as foetus takes a breath.
Dropping PGE2 levels as placenta is removed.
Which drug can be used to maintain patency of ductus arteriosus in babies with a ductal dependant congenital cardiac disease
PGE1
Define respiratory quotient
Dimensionless number that is the ratio of carbon dioxide produced to oxygen consumed in respiration. It can be used to calculate basal metabolic rate.
What Is the respiratory quotient of carbohydrates
1
What Is the respiratory quotient of fat
0.7
What Is the respiratory quotient of protein
0.8
What Is the respiratory quotient of amino acids
0.8
What is the role of foetal renin in maternal-foetal circulation
Renin converts angiotensinogen to angiotensin I. Angiotensin I is converted to angiotensin II by ACE.
Angiotensin II regulates uteroplacental vascular resistance and blood flow.
What is a delta ratio in acid-base disorder
The ratio of change in anion gap to the ratio of change in bicarbonate
What does a delta ratio in acid- base disorder of <0.4 tell you
Normal anion gap acidosis
What does a delta ratio in acid- base disorder of 0.4-0.8
Combination of normal and high anion gap metabolic acidosis
What does a delta ratio in acid- base disorder of 1-2 tell you
High anion gap metabolic acidosis
What does a delta ratio in acid- base disorder of >2 tell you
Metabolic acidosis with co-existing metabolic alkalosis
or a compensated respiratory acidosis
How many molecules of ATP does one cycle of the Kreb’s cycle produce
15
Describe what the relative refractory period is in the cardiac myocyte action potential
The Na+ channels can’t be re-activated until they have returned to their resting potential to avoid tetany. Na+ channels start to reach this point at phase 3 and fully reach it by phase 4. In phase 3 a supra maximal stimulus may trigger an action potential as some of the Na+ channels are available already.
Why should tracheostomy tube cuff pressure be kept between 20-25mmHg
Excessive cuff pressure can compromise blood flow to tracheal mucosa by branches of the inferior thyroid artery.
What are the signs of anterior spinal cord syndrome
- Bilateral loss of temperature and pain sensation.
- Complete motor paralysis. - Proprioception intact (dorsal columns supplied by posterior spinal artery)
- Caused by damage/occlusion to anterior spinal artery.
What are the signs of posterior spinal cord syndrome
Bilateral loss of proprioception and vibration sense. Pain and temperature sensation intact. Caused by damage to posterior spinal artery.
Which artery is affected in locked-in syndrome
Basilar artery
Where is the narrowest part in a child’s airway
At the level of the cricoid cartilage
Describe temperature control of hypothalamus
Posterior hypothalamus sets temperature set point and responds to cold stimulus. Acetylcholine Is main neurotransmitter.
Anterior hypothalamus senses warming of blood. Main neurotransmitters include dopamine, 5HTP, norepinephrine, prostaglandins
What are cold receptors in the skin also known as
Bulbs of krause
What are warm receptors in the skin also known as
Bulbs of Ruffini
Describe the Gibbs- Donnan effect
The Gibbs-Donnan effect is the unequal distribution of charged permeant ions across a semi-permeable membrane due to the effect of presence of charged unpermeant ions.
Damage to which nerve during radical mastectomy causes winging of the scapula
Long thoracic nerve C5, C6, C7
Mutation of which gene causes primary polycythaemia
JAK2
What are the levels of neuromuscular blockade
Complete (PTC = 0)
Deep (PTC >=1 TOF count 0)
Moderate (TOF count 1-3)
Shallow block ( TOF count 4, TOF ratio < 0.4)
Minimal block (TOF count 4, TOF ratio 0.4-0.9)
Acceptable recovery (TOF ratio >0.9)
Give signs and symptoms of hypermagnesemia
ECG: Prolonger PR and wide QRS. In severe cases complete heart block
Hyporeflexia
Double vision
nausea and vomiting
Respiratory depression
How do you calculate osmolality
Osmolality = Glucose + urea + 2(Na+)
What is normal serum osmolality in mOsmol/kg
280-305 mOsmol/kg
Define Pasteur point
The partial pressure of oxygen at which oxidative phosphorylation ceases.
Around 1mmHg
(mitochondria no longer able to carry out aerobic respiration)
How can a fast insufflation rate of intra-abdominal CO2 cause bradycardia
Peritoneal stretch receptors trigger vagal response causing increased parasympathetic and reduces sympathetic drive to heart.
Describe ventilation and perfusion in West zone 1 of lung
Apical alveoli are more distended here and have high intra-alveolar pressure which compresses blood vessels.
Good ventilation
Poor perfusion
High V/Q (deadspace)
Describe ventilation and perfusion in West zone 3 of lung
Alveoli at lung bases are compressed due to weight of lung (gravity). The venous pressure is higher than alveolar pressure.
Poor ventilation
Good perfusion
Low V/Q (shunt)
Describe ventilation and perfusion in West zone 2 of lung
Alveolar pressure is lower than arterial pressure but higher than venous pressure. This are has optimal V/Q matching
What is the resting membrane potential of a cardiac myocyte
-90mV
What is the resting membrane potential of the SAN
-60mV
At what level does the spinal cord terminate and become cauda equina in adults
L1
Why can glycosuria be normal in pregnancy
During pregnancy there is increased renal vasodilation causing GFR and renal blood flow to increase. This reduces threshold for glucose to be filtered out.
What is the chemotactic trigger zone also known as
Area postrema
Which drug is used to treat MuSK (muscle specific tyrosine kinase) myasthenia gravis
Rituximab
Where is aldosterone secreted
Zona glomerulosa in adrenal cortex
How does aldosterone act on the kidney
Acts on ENaC coupled channel in principal cells of DCT. This causes increased Na+ reabsorption and increased K+ excretion.
Which Aquaporins are present in descending loop of Henlé
AQP1
Which Aquaporins are always present in basement membrane of loop collecting duct
AQP3 and AQP4
Which Aquaporins are inserted into tubular cell wall of collecting duct in response to ADH
AQP2
Where are V2 (vasopressin) receptors found
Collecting duct of nephrons.
Trigger AQP2 insertion into luminal membrane
Where are V1 (vasopressin) receptors found
peripheral arterioles
Cause vasoconstriction
Where are V3 (vasopressin) receptors found
CNS
Trigger ACTH release
What effect does ANP have on kidneys
Promotes Na+ and H20 excretion.
Increases GFR by causing vasodilation of afferent renal arteriole and efferent arteriole vasoconstriction.
Inhibits renin and aldosterone release
What is the Cockcroft-Gault equation
Equation used to estimate creatinine clearance
(140-age) x lean body weight) / (Creatinine (mg/l) X 72)
Why does Uncal herniation cause fixed dilated pupils
Parasympathetic nuclei in the midbrain become compressed causing unopposed sympathetic enervation to Iris causing dilation and loss of light reflex.
What is the formula for Cerebral Perfusion Pressure (CPP)
Cerebral perfusion pressure = MAP - ICP/CVP (Whichever is higher)
Outline CSF flow
Produced by ependymal cells in choroid plexus in lateral ventricle.
Flows through foramen of Monroe into 3rd Ventricle
Flows through aqueduct of Sylvius into 4th Ventricle
Flows through foramen of magendie into cisterna magna to supply spinal cord
Also flows through and foramen of Luschka into subarachnoid space to supply brain
Re-absorbed by arachnoid vili.
Define Huffner’s constant
The volume of oxygen that can be bound to 1g of adult Hb.
1.34
What is the formula for arterial oxygen content
Arterial oxygen content = [Hb x Sa02 X 1.34] + [0.003 X PaO2]
Define pulmonary hypertension
Pulmonary artery systolic pressure > 30mmHg or mean pressure > 20mmHgh.
How is anion gap calculated
anion gap =
(Na+ + K+) - (Cl- + HC03-)
Give 8 causes of raised anion gap metabolic acidosis
MUDPILES
Metformin
Urea
DKA
Paracetamol
Isoniazid
Lactate
Ethylene glycol
Salicilate
Describe features of Type Ia sensory nerve fibres
- Primary afferent sensory fibres for stretch receptors in muscle known as muscle spindle
- Myelinated large diameter
- fast conduction speeds 80- 120 m/s
Describe features of Type Ib nerve fibres
- Primary afferent sensory fibres for stretch receptors in muscle known as Golgi tendon organ
- Myelinated large diameter
- fast conduction speeds 80- 120 m/s
Describe Golgi Tendon Reflex
An inhibitory reflex stimulated by stretch of Golgi tendon organ in muscle.
Synapse in Doral columns with interneurons that inhibit the same muscle contraction or cause contraction of antagonising muscle.
Avoids over stretching muscle
Uses Type 1b afferent nerve fibres
Describe features of Type II nerve fibres
Primary afferent sensory fibres for cutaneous mechanoreceptors in skin
Myelinated
Fast conduction speeds
Describe features of Type III nerve fibres
(aka Type A-delta) Primary afferent sensory fibres for nociceptors. Temperature and sharp pain sensation.
Lightly myelinated
Moderate conduction speeds
Describe features of Type B nerve fibres
Preganglionic autonomic nerve fibres
lightly myelinated
smaller diameter than type A nerves and slower conduction speeds
Describe features of Type C nerve fibres
Primary afferent sensory fibres for pain and temperature sensation
Unmyelinated
Slow conducting speed
Responsible for neuropathic pain. Poorly localised
E.G DOMS
rupture of aneurysm of which artery is most commonly implicated in subarachnoid haemorrhage
Anterior communicating artery
What is the Anrep effect
Increased after load causes increased contractility of the heart
What is the Bowditch effect
Increased heart rate causes increased contractility of the heart
Describe double Bohr effect
CO2 in foetal blood diffuses down its concentration gradient into maternal circulation at placenta. Lower CO2 shifts oxygen dissociation curve to left increasing affinity of Hb for oxygen
Loss of CO2 makes foetal blood relatively more alkaline which shifts oxygen dissociation curve to the left. Increasing Hb affinity for oxygen
What are the 5 parts of the brachial plexus
RTDCB - Read that damn cadaver book
Roots
Trunks
Divisions
Cords
Branches
Which part of the brachial plexus is blocked during inter scalene block
Trunks
Define abdominal compartment syndrome
Intra-abdominal pressure >20mmHg with organ compromise
How can abdominal compartment syndrome cause acute renal failure
Reduced renal arterial pressure due to compression of great vessels
Increased pressure causes renal outflow obstruction which causes back pressure.
Reduces filtration gradient in glomerulus
How do you calculate target tidal volume when ventilating a patient
Ideal body weight X 6ml/kg
What is the saturated vapour pressure of water at 37C
6.3kPa
What is the diagnostic criteria for ARDS
1- Acute onset with identifiable condition
2- Bilateral pulmonary infiltrates + oedema on XR
3- Pulmonary wedge pressure <18 mmHg
4- Reduced PaO2/FiO2 ratio
Give 4 conditions associated with a Transudative pleural effusion
CCF
Liver cirrhosis
Nephrotic syndrome
Severe hypoalbuminaemia
Give 4 conditions associated with a exudative pleural effusion
Malginancy
Infection - empyema
P.E
Pulmonary infarction
Trauma
Describe Light’s criteria for pleural effusions
Pleural fluid is considered an exudate if any of the following are present:
1- The ratio of pleural fluid to serum protein is greater than 0.5
2-The ratio of pleural fluid to serum LDH is greater than 0.6
3- The pleural fluid LDH value is greater than two-thirds of the upper limit of the normal serum value
Describe the Bainbridge reflex
Increase in heart rate in response to increased venous return to right atrium in high volume states. Triggered by atrial stretch receptors
At how many weeks gestation does surfactant production begin
20 weeks
At how many weeks gestation does surfactant production reach an adequate level
35 weeks
What is the L:S (Lecithin: sphingomyelin) ratio in mature foetal lungs
2
What is the L:S (Lecithin: sphingomyelin) ratio in immature foetal lungs
<2
What is the purpose of surfactant
Reduce alveolar surface tension
Outline puppilary reflex
Afferent nerve CNII carries action potential to pretectal nucleus in brain. Nasal fibres decussate at optic chiasm on the way
From pretectal nucleus afferent nerves go to Edinger westphal nucleus.
Parasympathetic fibres of CNIII go to Cilliary ganglion. From here 2 efferent limbs to puppilary muscle- 1 ipsilateral and 1 contrallateral
Causes Miosis in response to light
List endogenous compounds that are metabolised by the lungs
Bradykinin
Noradrenaline
Adenosine
Serotonin (5HTP)
PGE2
Leukotrienes
Name a hormone that is activated in the lungs
Angiotensin 1 to angiotensin 2
Which nerve fibres enter via Dorsal ramus
Sensory nerves from skin
Motor nerves to deep muscles of the back
Which nerve fibres enter via Ventral ramus
Mainly motor nerves
Which nerve roots make up the Cervical plexus
C1-C4
Which nerve roots make up the Brachial plexus
C5-T1
Which nerve roots make up the Lumbar plexus
L1-L4
Which nerve roots make up the Sacral plexus
L4-S4
Define allodynia
Pain sensation from a stimulus that does not normally cause pain
How do you manage patients with adrenal insufficiency during major surgery
100mg hydrocortisone intra-operatively
200mg in 24hr infusion post operatively
How do you calculate Cerebral Perfussion Pressure (CPP)
CPP = MAC - ICP or CVP (whichever is highest)
What is the target range of cerebral percussion pressure (CPP) in traumatic head injury?
50-70mmHg
Summarise central chemoreceptors that control breathing
- Found on ventral surface of medulla
- Stimulated by increased H+ ions in CSF (indirectly by increased CO2)
What are the 2 types of peripheral chemoreceptors and which nerves are their afferents
Aortic bodies- Vagal afferents
Carotid bodies- glossopharyngeal afferents
(Both sense increased PCO2, increased H+ AND LOW PO2)
What proportion of renal blood flow goes to medulla and cortex
Cortex 90%
Medulla 10%
Name the capillaries that run along the loop of Henle into the medulla of the kidney
vasa recta
Which technique uses nitrous oxide inhalation to estimate cerebral blood flow
Kety-Schmidt technique
Inhale 10% Nitrous oxide for 10 minutes and measure jugular venous concentration which is assumed to be the same as cerebral conc.
Does ICP affect rate of CSF production
No
CSF production is indépendant of ICP
What volume of CSF is produced in one day
500ml
Where is CSF absorbed
Dural venous sinuses via arachnoid vili
What conc. of K+ is normal in CSF
2.5-3.5mmol/L
What conc. of glucose is normal in CSF
2.7-4.2 mmol/L
Which 2 ions are found at a higher conc. in CSF compared to plasma
Magnesium and Chloride
What is the formula to calculate pH
pH = - Log(H+)
Describe the Haldane effect
Haemoglobin can carry increased amounts of CO2 in its deoxygenated compared to oxygenated state
(Venous blood carries more CO2)
This is because Carbon dioxide binds to amino groups of Hb forming carbamino compounds. But oxygen reduced Hbs affinity to bind CO2.
Describe the Bohr effect
Affinity of Hb for oxygen decreases in acidic pH or high CO2
Haemoglobin buffers H+ ions by dissociating oxygen to bind H+ ions. Therefore increased acidity causes reduced oxygen affinity and right shift of oxygen dissociation curve
What is the normal anion gap range
8-16mmol/L
What effect does hypoalbuminaemia have on calculated anion gap
Under-estimates anion gap
metabolic acidosis could be due to lactic acidosis or DKA despite normal anion gap
List 4 causes of normal anion gap metabolic acidosis
ABCD
Addisons
Bicarbonate loss ( GI tract/ renal)
Chloride excess (lots of NaCL fluids)
Diuretics (acetazolamide)
What is the pKa of carbonic anhydrase
6.1
Where is the majority of HC03- Reabsorbed in the kidney
PCT
List the fat soluble vitamins
ADEK
Vitamin A, D, E, K
Outline the swallowing reflex
- Food is voluntarily pushed into pharynx by raising tongue
- Swallowing receptors (in tonsil pillars) in pharynx trigger autonomic pharyngeal muscle contractions
- Soft palate elevates to stop food entering nasal cavity
- Palatopharyngeal folds pull medially so well masticated food can pass posteriorly
- Vocal cords close and epiglottis pulls upwards by neck muscles
- Upper pharyngeal sphincter relaxes to allow masticated food to enter oesophagus
Where is calcitriol produced
PCT of nephrons
Where is calcitonin produced?
Parafollicular cells (C-cells) of thyroid gland
Where is glucagon produced
alpha cells in pancreas
Where is CCK produced
Duodenal mucosal cells
Where are oxytocin and ADH released from
Posterior pituitary
Which hormones are released from anterior pituitary
GH
prolactin
ACTH
MSH (melanocyte stimulating hormone)
TSH
FSH
LH
How many molecules of oxygen can be carried by one Hb
4
Describe cooperative binding in Hb
Binding to first molecule of oxygen causes change in shape of Hb which increases its affinity for further oxygen binding of the other globing chains
Which glial cells make up the blood brain barrier (BBB)
Astrocytes
Which lung volumes can’t be measured with a spirometer
FRC
Total lung capacity
residual volume
How can FRC be measured
Helium dilution
Body plethysmograph
Which method is used to measure anatomical dead space
Fowler’s method
Breathing in 100% oxygen and exhaled gas analysed by nitrogen analyser. As deadspace slowly replaced with oxygen the nitrogen volume increases until a plateau is reached.
Which method is used to measure physiological dead space
Bohr’s method
Which glial cells are the macrophages of the central nervous system
Microglia
Which glial cells insulate neurones in the CNS
Oligodendrocytes
Which glial cells insulate neurones in the peripheral nervous system
Schwann cells
Which glial cells form an epithelial layer that lines the ventricles and central canal of spinal cord
Ependymal cells
What is another name for the cell body of a neurone
Soma
What is the function of dendrite in a neuronal cell
Receive information from other cells
What is the resting potential of a neuronal cell
-70mV
What is meant by saltatory conduction
Saltatory conduction is the propagation of action potentials along myelinated axons from one node of Ranvier to another.
Depolarisation only occurs at nodes of Ranvier which speeds up the transmission of the AP
What are the signs of spinal cord hemisection (Brown Squared syndrome)
Ipsilateral motor and proprioception loss
Contralateral loss of pain and temperature sensation
What are the signs of complete cord transection
Loss of motor function and sensation below level of injury
- Some reflexes recover and can become hyperactive
What are the signs of central cord syndrome
Motor impairment worse than sensory loss
upper limbs and distal muscles more affected than lower limbs and proximal muscles
What can cause central cord syndrome
Trauma that causes hyper extension of neck
Especially in elderly patients with narrow spinal cord e.g spinal canal stenosis or spondylosis
At which level does the sympathetic trunk start and end
T1- L2/3
Which artery supplies the anterior 2/3 of spinal cord
Anterior spinal artery
Which arteries supplies the posterior 1/3 of spinal cord
2 X posterior spinal arteries
What is the role of the radicular arteries in the spine
Support blood supply to spinal cord by feeding into anterior and posterior arteries
Which artery is a major contribution to the blood supply of the lower 2/3rds of the spinal cord
Artery of Adamkiewicz ( arteria radicularis manga)
At what level does the artery of Adamkiewicz arise
T11- L3
How many pairs of spinal nerves are there
31
8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal
List the ascending spinal tracts
Dorsal columns
Lateral spinothalamic
Anterior spinothalamic
Anterior spinocerebellar
posterior spinocerebellar
List the descending spinal tracts
Lateral corticospinal
Anterior corticospinal
Rubrospinal
tectospinal
reticulospinal
Vestibulospinal
What is the role of Dorsal columns
Ascending tract for fine touch and proprioception
What is the role of anterior spinothalamic tract
Ascending tract for crude touch and pressure sensation
What is the role of lateral spinothalamic tract
Ascending tract for pain and temperature sensation
What is the role of lateral spinocerebellar tract
Ascending tract for proprioception
In which part of the dorsal columns do nerves from below the level of T6 travel
Medial part known as Gracile fascicle
In which part of the dorsal columns do nerves from above the level of T6 travel
Lateral part known as Cuneate fascicle
Where no neurones in dorsal columns decussate
Medulla
Where do neurones in spinothalamic tracts decussate
At level where afferent 1st order neurone enters spinal cord
Explain the decussation of corticospinal tracts
80% decussate at medulla to form lateral corticospinal tract
20% do not decussate and form the anterior corticospinal tract
Which reflex is monosynaptic
Stretch reflexes e.g bicep or patella tendon
Which spinal reflex is polysynaptic
Withdrawel reflex
Sensory nerve from receptor synapses with interneurone in spinal cord which synapses with motor neurone to effector organ (muscle)
Which arteries is the basilar artery formed from
Left and Right vertebral artery
Which artery supplies the posterior cerebral hemisphere and brainstem
Basilar artery
What is the normal range of MAP under which cerebral blood flow is controlled by auto regulation
50-150 mmHg
How does hypothermia affect cerebral blood flow?
In hypothermia metabolic activity in the brain reduces which reduces blood flow due to flow metabolism coupling
How does a low PaCO2 affect cerebral blood flow
Causes vasoconstriction and reduced cerebral blood flow
List 4 circumventricular organs
Choroid plexus
Posterior pituitary gland
Area Postrema
Pineal gland
List 5 functions of CSF
1 Protect brain from trauma
2 Support weight of the brain by CSF buoyancy
3 Respiratory control via acid-base
4 Ionic homeostasis
5 Nutrition for brain tissue
Which intrinsic muscle of the larynx is innervated by Superior Laryngeal Nerve (SLN)
Cricothyroid
List the 5 intrinsic muscles of the Larynx
Cricothyroid
Cricoarytenoideus
Aretynoideus
Thyroaretynoideus
Thyroepiglotticus
What happens in unilateral recurrent laryngeal nerve injury
Hoarseness of voice and weak cough
What happens in bilateral recurrent laryngeal nerve injury
Airway obstruction or horseness of voice
(Partial injury to RLN causes more adduction of vocal cord than complete)
Does compliance increase or decrease with age
Increases
What term is used to describe how compliance varies during inspiration and expiration on a lung compliance curve
Hysteresis
How does closing capacity change as a percentage of vital capacity with age
Young healthy person CC is 10% of vital capacity
Patient > 65 years old CC is about 40% of VC
What happens when closing capacity is equal to FRC
Airway closure
Occurs in neonates and infants
40 year olds when supine
> 65 year old when standing
How is closing capacity measured
Helium dilution + Fowler’s method
Phase 1: Dead space gas with no helium
Phase 2: Mixed dead space and alveolar gas with increasing helium conc.
Phase 3: Plateau of just alveolar gas containing fixed conc. helium
Phase 4: Closing volume reached, Helium conc. increases further as airways closed
Which metabolic reaction causes production of 2,3 DPG
Glycolysis
Why does stored blood’s p50 lie to the left on oxygen dissociation curve compared to normal blood
No 2,3 DPG in stored blood
What does a huge V wave on CVP monitoring suggest
Tricuspid regurgitation
What is the minimum MAP required to maintain auto regulation of renal blood flow to maintain constant GFR
MAP > 80
Where in the kidney is aldosterone produced
Zona Glomerulosa
When in the day is aldosterone release highest
Morning
What does an increased strong ion difference mean in terms of Stewart’s theory of acid-base
Increased strong ion difference (SID) = gain of strong cations (Na+ / K+) or loss of strong anions (Cl-) this causes alkalosis
What does a reduction in strong ion difference mean in terms of Stewart’s theory of acid-base
Reduced strong ion difference (SID) = loss of strong cations (Na+ / K+) or gain of strong anions (Cl-) this causes acidosis
Which metabolic disturbance is seen in Aspirin overdose
Initial respiratory alkalosis followed by metabolic acidosis
What effect does Gastrin have on gastric emptying
Increases gastric emptying by increasing pyloric pumping force
Which enzyme is deficient in Gilbert’s disease
Glucoronyl transferase
(responsible for conjugation of bilirubin)
Explain why post hepatic jaundice causes dark urine and pale stools
Increased levels of conjugated bilirubin enter blood due to not being able to drain into intestine where bacteria break it down. More filtered into urine causing dark urine.
Intestines break down conjugated bilirubin into stercobilinogen then oxidised to stercobilin which gives faeces brown colour. Absence of this causes pale stools.
How can you calculate an estimate for osmolality
Osmolality = 2(Na+) + Urea + Glucose
How is post dural puncture headache managed in first 24 hours
Supportive Mx- Hydration and simple analgesia e.g paracetamol
what is the gold standard management of post dural puncture headache post 24 hours
Epidural blood patch
What is the flow rate of a 14G cannula
360mL/min
Which drugs can be used to increase heart rate in a transplanted heart
Direct acting Beta agonist drugs- Noradrenaline, adrenaline, isoprenaline
(Transplanted hearts are denervated so need direct acting catecholamines that act on SAN)
Which physiological parameters must be checked to exclude reversible causes when doing brainstem testing
Na+ 115-160
Glucose 3- 20
PO2 >10kPa
temperature >34
Why is the vocal cord more adducted in partial laryngeal nerve injury than complete
Recurrent laryngeal nerve supplies abductors more than adductors. During partial injury abductors are affected more than adductors.
Which SOFA score defines sepsis
Sequential organ failure assessment (SOFA) score of 2 or more
What causes the 4th heart sound
When during atrial systole blood hits into a non compliant left ventricle
e.g in aortic stenosis, hypertrophic cardiomyopathy
What causes the 3rd heart sound
Blood flowing rapidly into the relaxing ventricles during early diastole.
Congestive cardiac failure
What is the role of T-tubule in sarcomere
Extension of sarcolemma (cell membrane) that invaginates into sarcomere to transmit AP to Dihydropiridine receptor of sarcoplasmic reticulum where calcium is released
What blocks the actin- binding site when a myocyte is at rest
Tropomyosin
What does calcium bind to during myocyte contraction to cause the tropomyosin to move away from actin binding site
Troponin C
What binds on the actin binding site to cause cardiac muscle contraction
Myosin head
What determines the force of contraction of cardiac myocyte
Number of cross bridges formed - this depends on free calcium conc.
Outline the stages of skeletal muscle contraction
- AP reaches sarcomere and spreads down into T-tubules
- Conformational change in DHP receptor on sarcoplastic reticulum
- DHP receptor interacts with Ryanodine receptor on SR
- Calcium induced calcium release
- Calcium binds to troponin C
- Troponin C moves tropomyosin out of the way so it no longer covers actin binding site
- Myosin head binds to actin binding site and pivots to pull the actin and myosin over each other
- Na+/Ca2+ exchange pump moves Ca2+ back into SR
- ATP binds to myosin causing it to release from actin
Which cranial nerve is the afferent fibre for the baroreceptors in carotid sinus
Glossopharyngeal (CN IX)
Which cranial nerve is the afferent fibre for the baroreceptors in aortic arch
Vagus (CN X)
What effect does adenosine have on smooth muscle
Causes vasodilation by reducing calcium influx
What effect does prostaglandin E and prostacyclin have on vascular smooth muscle
Both are vasodilators
How does Anti natriutic peptide (ANP) control ECV and Na+ conc.
ANP is released from atria in response to increased stretch of the wall during high volume state
ANP binds to receptors in collecting duct causing increased NA+ and water exertion
Are lungs more or less compliant during inspiration compared to expiration
Less compliant during inspiration
What is a normal volume for FRC
2.5-3L
What effect does exercise have on pulmonary vascular resistance (PVR)
Reduces PVR
What is the equation for Systemic vascular resistance (SVR)
SVR = (MAP-CVP)/CO X 80
Which units are used to measure SVR
Dynes.s/cm5
What does the Pentose phosphate shunt produce
NADPH
Which cells produce calcitonin in the thyroid
Parafollicular cells
What percentage protein bound is T3 and T4
99% bound to thyroxine-binding globulin
Which adrenal cells are affected in pheochromocytoma
Chromafin cells
Which drug can be used to manage carcinoid syndrome
Octreotide
What causes secretin release
S cells in the duodenum release secretin in response to low pH (acid) and fat
What is the effect of secretin on the pancreas
Causes increase in volume of pancreatic juices and HCO3- content
What causes release of CCK
I cells in duodenum release CCK in response to fatty acids and protein
What are the functions of CCK
Stimulates Acinar cells in pancreas to release more enzyme into pancreatic juice
Stimulates increased bile production and gall bladder contraction
Increases satiety
What is the normal volume of CSF
150ml
What effect does sympathetic stimulation have on detrusor muscle
Causes relaxation and urine retention
What effect does parasympathetic stimulation have on detrusor muscle
Causes muscle contraction and micturition
Which of the external and internal urinary sphincter is innervated by the pudendal nerve S2-4
External urinary spincter- this is under voluntary control
How do you calculate maintenance fluids for children
4-2-1 rule
4ml/kg/hr for first 10kg
2ml/kg/hr for next 10kg
1ml/kg/hr for any weight after that
How do you calculate fluid deficit in children
Fluid deficit = weight x %dehydration x 10
signs of 5-10% dehydration
- Reduced skin turgor, sunken eyes, tachycardia, tachypnoea, reduced UO
Signs of >10% dehydration
Skin mottled, deeply sunken eyes, markedly increased HR, RR and markedly reduced UO
Explain how an intra-aortic balloon pump works
IABP inserted via femoral artery and up to descending aorta.
IABP inflates during diastole to increase coronary perfussion pressure
Deflates during systole which reduces after load
How is FRC measured
Helium dilution
Body Pletysmograph
Which gas is used in diffusion capacity testing of the lung
CO
carbon monoxide
Where in the kidney is Adenosine released
Macula densa
What effect does Adenosine have on renal blood flow
Baseline level of constriction of afferent arteriole
Reduced Adenosine release in response to reduced GFR causes less consctriction of afferent arteriole and increased GFR
What effect does PGE2 have on renal blood flow
Dilated afferent arteriole to increase GFR
Where is PGE2 released in nephron
DCT
Why can NSAIDs cause reduction in GFR
NSAIDS inhibit PGE2 which is responsible for dilation of afferent arteriole in bowmen’s capsule
What effect does angiotensin II have on GFR
Causes constriction of efferent arteriole to increase GFR
What is the main excitatory neurotransmitter for painful stimulus where Aδ neurone synapses with second order neurone
Glutamate
What are the main Inhibitory neurotransmitters for painful stimulus where Aδ neurone synapses with second order neurone
Gamma-amino butyric acid (GABA)
Glycine
At what plasma conc. of Glucose do you start to get glycosuria
10mmol/L
What proportion of filtered urea is reabsorbed
50%
What effect does acidosis have on k+ excretion from the kidney
Reduced k+ excretion
What effect does alkalosis have on k+ excretion from the kidney
Increased k+ excretion
What effect does supine position have on FRC
Reduces FRC
What effect does a general anaesthetic have on FRC
Reduces FRC
Who has a greater FRC men or women
Men
What effect does a exercise have on FRC
Increases FRC
Define venous admixture
The amount of mixed venous blood which would have to be added to ideal pulmonary end-capillary blood to explain the observed difference between pulmonary end-capillary PO2 and arterial PO2
(Basically a volume of venous deoxygenated blood that appears to have bypassed the lungs (shunted) which has causes a lower than expected arterial PO2)
What is the Chloride shift in red blood cells
When HCO3- leaves red cells CL- enters red cells to maintain electric neutrality
Where in the stomach are chief cells found
Fundus
What is the effect of secretin on the stomach
Inhibits gastric acid secretion
What is the role of ADH in platelets
ADH has a role in platelet aggregation.
Stored in dense granules in platelet.
Binds to P2Y12 receptor on platelet causing platelet aggregation
What is the mnemonic WET FLAG for paediatric emergencies
W eight (age+4) X 2
E nergy 4 x weight (energy for defib)
T ube age / 4 + 4
FL uids 20ml/kg bolus NS
A drenaline 0.1ml/kg of 1:10,000
G lucose 2ml/kg of 10% glucose
What are the main differences in signs of neuroleptic malignant syndrome and serotonin syndrome
Serotonin syndrome has hyperreflexia and clonus whereas NMS has more pronounced rigidity known as lead pipe rigidity
What is the risk of using Suxamethonium in patients with Neuromuscular disorders
May cause hyperkalaemia by recruiting extra-junctional Ach receptors
What do gamma cells of the pancreas release
Pancreatic polypeptides
What do Epsilon cells of the pancreas release
Ghrelin
Describe the differences between type 1, type 2a and type 2b muscle fibres
Type 1: Slow contracting slow to fatigue, use aerobic respiration, fine movements, more mitochondria, contain more myoglobulin
Type 2a: Fast twitch, intermediate motor units, anaerobic, intermediate myoglobin
Type 2b: Fast twitch, large motor units, anaerobic, low myoglobin, high glycolytic capacity late recruitment
How long before brainstem testing must sedatives and neuromuscular blocking drugs be held
48 hours
Which cranial nerve reflexes are tested during brainstem testing
Pupillary reflex (CNII + CNIII)
Corneal reflex (CNV + CNVII (blink))
Pain response (pressure on supraorbital notch)
Gag reflex (CNIX + CNX)
Cough reflex( CNX- Stimulate carina with suction)
Which 2 tests need to be carried out twice before determining brainstem death
Cranial nerve testing
Apnoea test
Which ECG lead configuration is used to detect left ventricular ischaemia
CM5
Describe closing capacity in the lungs
Closing capacity is the volume at which airway closure starts.
Closing capacity = closing volume + residual volume
Normally smaller than FRC so airway closure does not occur during tidal volume breaths
What effect does pH have on pulmonary vascular resistance (PVR)
PVR decreases with more alkaline blood (increased pH)
What effect does PaCO2 have on pulmonary vascular resistance (PVR)
Increased PaCO2 increases PVR
What effect does Angiotensin have on pulmonary vascular resistance (PVR)
Angiotensin increases PVR by causing vasoconstriction
What effect does Prostacyclin have on pulmonary vascular resistance (PVR)
Prostacyclin decreases PVR due to vasodilating effect
What effect do volatile anaesthetic agents have on pulmonary vascular resistance (PVR)
All volatile anaesthetic agents reduce PVR
What is the formula for Oxygen Flux
DO2 = CO X (( Hb X Sa02 X 1.34) + (PaO2 X 0.003))
DO2 = CO X Arterial oxygen content
Which Ion Is exchanged to secrete H+ into the filtrate of the PCT
Na+ is reabsorbed out of filtrate in exchange for H+ which is secreted into the filtrate
What is the function of Aα nerve fibres
Motor nerves to muscles and proprioception
What is the function of Aβ nerve fibres
Touch and pressure sensation
What is the function of Aγ nerve fibres
Innervate muscle spindles which are stretch receptors that detect changes in the length of a muscle
What is the function of Aδ nerve fibres
Sharp pain sensation
Temperature sensation
What are the 4 factors in Apfel score for PONV
Female gender
Previous PONV or motion sickness
Opiate use
Non-smoker
What effect does Calcitonin have on plasma calcium levels
Reduces Calcium levels
Inhibits osteoclasts
Reduces calcium reabsorption in kidney
What effect does PTH have on calcium
Increases Calcium levels
Stimulates Osteoclasts
Increases calcium reabsorption from kidney
Increases intestinal calcium reabsorption
Why can TURP syndrome cause visual disturbances/ blindness
During TURP procedure high volumes of irrigation fluid are used most commonly 1.5% Glycine
Glycine causes direct depressant effects on CNS including visual disturbances
Which calcium channel blocker can be used in cerebral vasospasm
Nimodipine
How long does it take before proteolysis starts in starvation
24 hours
