ILA formatives Flashcards
What do central chemoreceptors in the ventral medulla respond to?
CSF pH
What cell provides cilia for mucocillary escalator?
Columnar epithelial cells
Equation for vital capacity
Tidal volume + Inspired reserve volume + Expired reserve volume
Arterial gas picture for type 1 respiratory failure
Low pO2
Normal/low pCO2
Where are the main peripheral chemoreceptors located?
Aortic arch and carotid arteries
What is the term used to describe a malignant tumour of the pleural membranes?
Mesothelioma
What can cause type 1 respiratory failure?
Conditions that affect oxygenation
- Low ambient oxygen (e.g. at high altitude)
- Ventilation-perfusion mismatch (e.g. pulmonary embolism)
- Alveolar hypoventilation due to reduced respiratory muscle activity, e.g. in acute neuromuscular disease (this form can also cause type 2 respiratory failure if severe)
- Diffusion problem ( e.g. in pneumonia)
- Shunt (oxygenated blood mixes with non-oxygenated blood from the venous system, e.g. right to left shunt)
What is the arterial blood gas picture for type 2 respiratory failure?
Low pO2
High pCO2
Normal/high HCO3
What factors cause bronchoconstriction?
Cold dry air
Parasympathetic stimulation
Histamine release
Beta-Blockers
If a peanut is inhaled, where in the airway is it most likely to become lodged?
Right main bronchus
Which nerve supplies motor function to the diaphragm?
Phrenic
Which changes in blood stimulate carotid chemoreceptors?
Oxygen, carbon dioxide and H+ ions
What can lead to type 2 respiratory failure?
Inadequate alveolar ventilation
- Increased airways resistance - COPD
- Reduced breathing effort (drug effects, brain stem lesion, extreme obesity)
- A decrease in the area of the lung available for gas exchange (chronic bronchitis)
- Neuromuscular problems
Which nerve are superior laryngeal and recurrent laryngeal branches of?
Vagus
In sickle cell, what does hypoxia cause the HbS to do?
Polymerise
What structure is a protein in multiple sub units?
Quaternary
How does hydroxyurea work in treating sickle cell?
Increases the synthesis of HbF (2 alpha 2 gamma chains, greater affinity for oxygen than HbA)
What causes sickle cell anaemia?
An autosomal recessive inherited condition substituting an amino acid in the beta globin chain
What causes the sickling in sickle cell?
Deoxygenated HbS polymerises and binds to the cell cytoskeleton which distorts the normal cell shape into the classic sickle shape
What is a disulphide bond?
A covalent bond between side chains of cysteine residues
What is a hydrogen bond?
A type of Vander Waals force. It is the strongest of them and is the interaction between dipoles, involving a hydrogen and an oxygen/nitrogen/fluorine
What is van der waals force?
A weak attractive interaction between two atoms due fluctuating electrical charges
What is hydrophobic force?
the attraction of hydrophobic protein side chains which form tightly packed cores on the interior of proteins which exclude water molecules
Which enzyme causes the double helix to unzip?
Helicase
In sickle cell, occlusion of what typically causes acute pain crisis?
Bone
- Early presentations can be pain in the hands and feet with severe pain in bones such as femur, humerus, ribs and pelvis occurring in older children
- These are due to vaso-occlusive events in the small vessels
- Repeated events in the bones can lead to chronic infarcts
Which enzyme unwinds supercoiled DNA?
Topoisomerase
What is renin and what is its function?
Renin is a proteolytic enzyme which activates angiotensinogen to produce angiotensin I
How is water distributed in a healthy 70kg man?
Intracellular 28L. Interstitial 11L. Intravascular 3L.
What is the principle site of renin production?
Juxtaglomerular cells
If the patient does have diabetes insipidus and is not producing any ADH which of the following is MOST LIKELY to show her blood and urine osmolality after 3 hours of water deprivation?
Blood 300/urine 100
- During the water deprivation test the body should detect an increased serum osmolality (300) and produce ADH in order to promote water retention.
- As she is unable to produce ADH she will produce dilute urine (low osmolality, 100) instead of concentrated urine.
What can low albumin cause?
A low albumin causes a decrease in oncotic pressure and water diffuses from the blood into the interstitial fluid
Seen in pitting oedema
What is insensible fluid loss and give an example?
Insensible fluid loss is loss that is not easily measured e.g. sweating, water lost from respiration, evaporation during abdominal surgery.
Where is ADH synthesised and stored?
Synthesised by the supraoptic and paraventricular nuclei of the hypothalamus.
Stored in the posterior pituitary gland
What is the role of aldosterone and where is it synthesised?
Steroid hormone released from the adrenal cortex in response to stimulation by angiotensin II
It promotes sodium reabsorption and potassium secretion in the distal tubules of the kidneys
What is severe pulmonary hypertension a cause of?
Right heart failure
- Right ventricle has to work harder to pump blood through the pulmonary artery
- RV unable to generate sufficient pressure and therefore starts to fail
What is pulmonary oedema in the presence of a normal central venous pressure a sign of?
Left heart failure
- Left sided heart failure causes an increase in pulmonary pressure leading to pulmonary oedema
- A raised central venous pressure is a reflection of right sided heart failure
Which nerve innervates the pericardium?
Phrenic
Describe the normal pathway of electrical conduction through the heart
SAN
Contraction of atria
AVN
Bundle of His
Purkinje fibres
Contraction of ventricles
What is the purpose of the Ductus Arteriosus in the foetal cardiovascular system?
allow blood to bypass the foetal lungs by shunting it from the Pulmonary Artery to the Aorta
What does shortness of breath, severe peripheral oedema and ascites after a heart attack indicates
Biventricular failure
If the end diastolic volume (EDV) in the average healthy person’s left ventricle is 120mls, what would you expect the end systolic volume (ESV) to be?
50mls because stroke volume of 70mls in the average person
Which artery most frequently supplies the Atrio Ventricular Node?
R coronary artery
- RCA supplies the area above including both SA & AV nodes
- LAD supplies most of the area below the AV conducting system, the His-Purkinje system
What does an increase in L ventricular end-diastolic pressure signify
L heart failure
- reduced contractility, reduction in stroke volume so end diastolic volume and end diastolic pressure will be increased
Equation for cardiac output
heart rate x stroke volume
What does an increase in L atrial end-systolic pressure signify?
Mitral valve stenosis
- Mitral stenosis causes an increased resistance to blood flow across the valve therefore a higher pressure is required to force blood from atrium to ventricle i.e. a higher left atrial end systolic pressure
What is secreted by Chief cells?
Pepsinogen
What is secreted by D cells?
Somatostatin
What is the function of the drug ‘Omeprazole’ on the GI tract?
Inhibition of Proton Pump to reduce acid secretion
What is the action of the proton pump in the parietal cells of the stomach?
K+ into cell, H+ out of cell
What supplies arterial blood to the Jejunum?
Superior mesenteric artery
What structures are classified in embryology as part of the ‘foregut’?
Proximal half of the Duodenum
Pancreas
Lower third of oesophagus
Gallbladder
Where does the Common Bile Duct drain into?
Duodenum
What is secreted by G cells?
Gastrin
How many layers of muscle are present in the stomach wall?
3
What is the first location that Fat is acted upon by Lipase enzymes when passing through the GI tract?
Oral cavity
What is the function of the vagus nerve and its action on parietal cells?
Vagus nerve is part of the parasympathetic system and releases acetylcholine onto parietal cells
What is the function of Intrinsic Factor produced in the stomach?
- Intrinsic Factor is a glycoprotein produced by the parietal cells of the stomach and is essential for the absorption of Vit B12.
- It binds with Vit B12 and forms a complex that resists digestion by gastric enzymes.
- The Vit B12 complex then passes through the stomach where it absorbed in the terminal ileum, transported to the liver and stored
What is secreted by Enterochromaffin (ECL) Cells?
Histamine
What is the change in cell-type (‘metaplasia’) seen in the lower oesophagus after prolonged reflux of acid?
Stratified squamous to columnar
What do central chemoreceptors respond to?
CSF pH
What cells provides cilia for the mucociliary escalator?
Columnar epithelial Cells
How do you calculate vital capacity?
Tidal volume + Inspired reserve volume + Expired reserve volume
What are the arterial blood gases for Type 1 respiratory failure?
low pO2, normal/low pCO2
Where are the main peripheral chemoreceptors located?
Carotid arteries and aortic arch
What is the term used to describe a malignant tumour of the pleural membranes?
Mesothelioma
What can cause type 1 respiratory failure?
This type of respiratory failure is caused by conditions that affect oxygenation such as:
- Low ambient oxygen (e.g. at high altitude)
- Ventilation-perfusion mismatch (parts of the lung receive oxygen but not enough blood to absorb it, e.g. pulmonary embolism)
- Alveolar hypoventilation due to reduced respiratory muscle activity, e.g. in acute neuromuscular disease (this form can also cause type 2 respiratory failure if severe)
- Diffusion problem (oxygen cannot enter the capillaries due to parenchymal disease, e.g. in pneumonia)
- Shunt (oxygenated blood mixes with non-oxygenated blood from the venous system, e.g. right to left shunt)
What is the definition of functional residual capacity?
the amount of air remaining in the lungs after normal quiet expiration
What are the arterial blood gases for type 2 respiratory failure?
low pO2, high pCO2, normal-high HCO3
How does adrenaline cause bronchodilation?
Adrenaline causes bronchodilation, by binding to β 2 -receptors in the smooth muscle of the bronchioles and causing their relaxation.
What can cause bronchoconstriction?
Cold dry air
Parasympathetic stimulation
Histamine release
Beta-Blockers
If an adult inhales a peanut, where is it most likely to become lodged in their airway?
Right main bronchus
Which nerve supplies motor function to the diaphragm?
Phrenic
Changes in what blood parameters stimulates carotid chemoreceptors?
Oxygen, carbon dioxide and H+ ions
What can cause type 2 respiratory failure?
- Increased airways resistance - chronic obstructive pulmonary disease
- Reduced breathing effort (drug effects, brain stem lesion, extreme obesity)
- A decrease in the area of the lung available for gas exchange (such as in chronic bronchitis)
- Neuromuscular problems
Where does the Vagus Nerve supplies voluntary motor function to?
Larynx
What causes an increased serum unconjugated (free) bilirubin and increased faecal urobilinogen?
Pre-hepatic cause of jaundice
What is the structure in the middle of the hepatic lobule?
Central vein
What structure is situated within the duodenal loop?
Pancreas
What causes obstructive jaundice?
Cirrhosis
Pancreatic carcinoma
Gallstones
Hepatitis
Bacterial enzyme hydrolysis in the gut produces this compound which is excreted in faeces
Stercobilinogen
The hepatic blood supply is how much of cardiac output?
25%
What is the cause of physiological jaundice of the newborn?
Excess breakdown of foetal haemoglobin
Microsomal enzyme uridine diphosphoglucoronosyl transferase (glucuronyl transferase) catalyses the formation of what?
Conjugated bilirubin
In the pancreas what is secreted by the A,B,D and F islet cells?
Glucagon is secreted by the alpha (A) islet cells.
Insulin is secreted by the beta (B) islet cells.
Somatostatin is secreted by the Delta (D) islet cells
Pancreatic polypeptide is secreted by the F islet cell.
Which compound is returned to the liver by the enterohepatic circulation?
Urobilinogen
Obstructive jaundice is commonly caused by gall stones within what structure?
Common bile duct
What are some functions of the liver?
Storing Vitamins A D E K
Production of Cholesterol
Glycogen storage
Conversion of thyroxine (T4) into triiodothyronine (T3)
What is CCK released in response to?
presence of amino acids in the gut
A 69 year old lady was slurring her words at a church coffee morning. At the same time her right arm began to feel heavy and weak. 24 hours later all her symptoms had resolved.
Likely cause?
Stroke/TIA
Whilst examining an elderly lady who arrives on the stroke ward, it becomes apparent that she can only see one half of your face. Where is the likely lesion?
Occipital lobe lesions
* Typically cause visual disturbances and depends on where the lesion is
* These can include visual illusions and hallucinations
* Trouble recognising objects or facial blindness
* Being able to write but not read
What is homonymous hemianopia?
When a lesion affects most of the occipital lobe on one side
the patient is unable to see the visual field on the opposite side of the lesion
An 89-year-old right-handed patient presents with acute onset of weakness and numbness of their left lower leg and foot is unusually agitated and in an aggressive mood. Which artery is likely to have been affected?
Anterior cerebral artery
* Supplies the anteromedial surface of the cerebral hemisphere.
* Paraplegia usually affects the lower limbs sparing the upper limbs and face.
* They may be incontinent.
* They may display frontal lobe symptoms e.g. personality changes
An elderly patient with a stiff flexed arm, and a stiff extended leg (both on the left) which the patient finds difficult to bend. Where is the cause most likely to be located?
Upper motor neurone
While examining a patient you observe that they walk with a wide unsteady gait and appear uncoordinated. Their speech is slurred. Where is the likely lesion?
Cerebellum
-Patients have a wide unsteady gait
- Impaired coordination
- Uncontrolled repetitive eye movements
- Difficulty with fine motor tasks
- Intentional Tremor
- Slurred speech
You are clerking an elderly gentleman who has had a stroke; the patient keeps trying to take his gown off and some of his responses are inappropriate and occasionally rude. Where is the likely lesion?
Frontal lobe
A 42 year old female suffers a violent headache followed by sudden collapse. You notice that her left pupil is fixed and dilated and her left eye is deviated laterally and downwards. Which artery is likely to have been affected?
Posterior communicating
Paralysis of the third cranial nerve affects the medial, superior, and inferior recti, and inferior oblique muscles.
A 40 year old removal man felt immediate back pain and a popping sensation after lifting a heavy box. The next day he noticed he was tripping over his right foot as it was dragging along the floor. Where is the cause most likely to be?
compression of the nerve root by a prolapsed vertebral disc
A 30 year old pregnant lady complains to the GP of progressive hand weakness. She is unable to open jars and even grip her tea cup. The GP noticed that the muscles around her thumb were wasting. Where is the cause most likely to be located?
Peripheral nerve
A 30 year old woman noticed both her eye lids becoming progressively more droopy with time (ptosis). Weeks later she began to experience double vision, and found it progressively more tiring and difficult to chew while eating. Which of these is the likely cause?
Myasthenia Gravis
- Condition of the neuromuscular junction
- Acetylcholine receptors are blocked by an auto immune reaction between the receptor protein and anti-acetylcholine receptor antibody
53 year old man with hypertension presents with sudden collapse; unable to move any part of his body except for eye movements, he appears to understand your questions, but is unable to answer. Where is the likely lesion
Brainstem
51 year old man has a 2 month history of weakness in both of his hands, he is now unable to open jars. His hands show wasting of the thenar eminence. He has recently developed slurred speech and difficulty swallowing. His tongue appears spastic and he is unable to protrude it. Which of these is the likely cause?
MND
A 75 year old patient presents to their GP surgery with an intensely itchy vesicular rash in two separate horizontal lines at the level of the nipple and umbilicus respectively. Which dermatomal distribution is this affecting?
T4
T10
The vagus nerve is composed of
Parasympathetic motor and sensory fibres
Which group of spinal nerves innervates the biceps reflex?
C5
C6
Which of these is not in CNS?
Ependymal cells
Schwann cells
Microglia
Astrocytes
Oligodendrocytes
Schwann cells
principle glial cells of the PNS.
They form the myelin sheath of motor and sensory neurones.
Which group of spinal nerves innervates the ankle reflex?
S1
S2
Where do the different tracts decussate?
- corticospinal tract decussates in the pyramids of the lower medulla
- spinothalamic tract decussates within the spinal cord.
- dorsal column decussates in the medulla oblongata
- anterior (ventral) spinocerebellar tract decussates twice – once in the spinal cord as part of the anterior white commissure and then again in the superior cerebellar peduncle.
- posterior (dorsal) spinocerebellar tract does not decussate
A 78 year old lady presents to her GP surgery with an intensely itchy vesicular rash in a horizontal line at the level of the nipple. What is the most likely diagnosis?
Shingles
Common in elderly
Produces a rash that is usually unilateral and has a dermatomal distribution
This descending motor tract originates in the cerebral cortex and synapses in the spinal cord
Corticospinal
A sexually active 75 year old gentlemen presents with a stamping gait. He is diagnosed with tabes dorsalis. On examination he has a loss of joint position sense and cannot feel the tuning fork (vibration) when placed on his medial malleolus. Which tract is affected?
Dorsal column medial lemiscus pathway
A 48 year old obese diabetic man, who smokes 30 a day presents with bilateral “glove and stocking” loss of pain, temperature and pin prick sensation. Which tract is affected?
Spinothalamic
Lateral spinothalamic pathway conducts pain and temperature
Anterior spinothalamic pathway conducts crude touch and firm pressure
Diabetes is a common cause of ‘glove and stocking’ peripheral neuropathy
What is the mechanism of anaemia in chronic renal failure?
Chronic renal failure causes a reduction in the production of erythropoietin.
How does aldosterone act on distal collecting duct?
- Acts on the distal collecting duct to cause an increase in the uptake of sodium.
- This increase in sodium causes an increase in the blood pressure
What does renin do?
Renin is secreted by the juxtaglomerular cells (JGC)
Renin is released in response to stimulation of beta adrenergic receptors on the JGC
Renin converts Angiotensinogen to Angiotensin I by removing a short amino acid chain
The macula densa stimulates renin release in response to changes in Na+ delivery to the distal tubules
What is the outermost layer of the kidney?
Capsule
What is renal clearance?
Renal clearance of a molecule is ‘the volume of plasma cleared of that molecule per minute’
How much of the cardiac output passes through the kidneys?
20%
