BRS MOCK 7 - Brainstem, Pancreas, HNS 1,2 Flashcards
What cranial nerves emerge from the midbrain?
Cranial nerves III and IV emerge at this level.
What cranial nerves emerge from the pons?
Cranial nerves V, VI, VII & VIII.
What cranial nerves emerge from the medulla?
Cranial nerves IX, X & XII emerge from medulla.
What tract are cranial nerves part of?
Corticobulbar.
Where does corticobulbar tract teminate?
Medulla.
What makes up the cerebral peduncles?
Corticospinal and corticobulbar tract.
Where are the cerebral peduncles?
Anterior portion of midbrain.
What do cranial nerves do once they emerge from corticobulbar tract?
Synapse with nuclei. Neurones from nuclei then go on and innervate structure in head, face, tongue and neck.
Which motor pathway has fibres which cross in the medulla? Where in the medulla does it cross?
Corticospinal. Cross over at pyramidal decussation.
Where are the descendings tracts in the medulla?
Medullary pyramids (anterior surface of medulla).
Anterior CNS blood supply?
Internal carotid system
Posterior CNS blood supply?
Vertebrobasilar
General somatic afferent nerve fibres function?
Fibres carry general sensation from skin, muscles, joints of head and neck.
General somatic efferent nerve fibres function?
Fibres innervate skeletal muscles.
General visceral afferent nerves fibres function?
Fibres carry sensation from viscera of head, neck, thorax and abdomen.
General visceral efferent nerves fibres function?
Fibres are the preganglionic parasympathetic neurons to cranial, thoracic and abdominal viscera.
Special somatic afferent nerve fibres function?
Fibres carry special senses of hearing and balance
Special visceral afferent nerve fibres function?
Fibres carry taste sensation.
Special visceral efferent nerve fibres function?
Innervate skeletal muscles of the jaw, face, larynx and pharynx.
Abdominal accessory organs start out as?
Foregut outgrowths.
What do acini in the pancreas do?
Secrete pro enzymes into ducts.
What do duct and centroacinar cells secrete into the pancreatic juice?
Bicarbonate ions.
What does bicarbonate in the pancreatic juice do?
Neutralises acid chyme from stomach which prevents damage to duodenal mucosa. Raises pH to optimum range for pancreatic enzymes to work.
What structures also produce bicarbonate instead of bicarbonate present in pancreatic juice?
Bile from liver and alkaline fluid from brunners glands.
How is bicarbonate secrete from pancreatic duct cells?
Carbonic anhydrase catalyses reaction of carbon dioxide with water to produce bicarbonate and H+ ions. Bicarbonate exchanged for chloride ion; bicarbonate enters lumen of duct while chloride enters duct cell. Sodium from blood enters duct cell while H+ enters blood.
How is high sodium in the blood maintained?
Na+/K+ exchange pump driven by ATP. Potassium into duct cell while sodium pumped into blood.
What drives water into lumen of pancreatic duct?
Sodium moves into lumen of duct down gradient from blood via paracellular junctions and water follows.
What channel drives chloride ions return to the lumen of the pancretic duct?
CFTR channel (cystic fibrosis transmembrane conductance regulator).
Why is pancreatic venous blood acidic but gastric venous blood is alkaline?
In pancreas H+ ions are released into blood. In stomach bicarbonate ions are released into blood.
Digestive enzymes in acinar cells are stored in what?
Zymogen granules.
What ensures that enzymes produced in pancreas are only activated once they enter the duodenum?
Trypsin inhibitor and enzymes are secreted as inactive pro enzymes.
What is the main enzyme that activates other proteolytic and lipolytic enzymes in the duodenum?
Trypsin.
What protein results in conversion of trypsinogen to trypsin? Where is this protein found?
Enterokinase secreted by duodenal mucosa. Found on the duodenal brush border.
What does lipase require for action?
Colipase and bile salts.
During cephalic and gastric phase what is mainly secreted in the pancreatic juices?
Enzyme rich juice. Lacks carbonate.
What is the gastric phase of pancreatic juice secretion?
Pancreatic juice secretion due to food arriving in the stomach.
What is the intestinal phase of pancreatic juice secretion? How is it different from the gastric and cephalic phase?
Hormone mediated when gastric chyme enters the duodenum. Both enzymes and carbonate released.
What stimulates enzyme secretion in pancreatic juice?
Acetylcholine from vagus nerve and cholecystokinin from duodenal I cells.
What stimulates release of cholecystokinin?
CCK releasing peptide due to increase in amino acid and fatty acids in lumen of duodenum. Gastrin releasing peptide.
What inhibits release of CCK?
Trypsin.
What triggers release of secretin from S cells?
Drop in pH in duodenum.
When does CCK affect bicarbonate secretion?
When paired with secretin it can cause a large increase in bicarbonate secretion. On its own has no effect on bicarbonate secretion.
What is held within the anterior cranial fossa?
Frontal lobe.
What is held within the middle cranial fossa?
Temporal lobes.
What is held within the posterior cranial fossa?
Cerebellum and brainstem.
What connects the orbit to the middle cranial fossa? What is present in this canal?
Optic canal. Optic nerve, ophthalmic artery.
What does the superior orbital fissure contain?
Ophthalmic divison of trigeminal nerve (V1), oculomotor nerve (III), Trochlear nerve (IV), Abducent nerve (VI), Superior ophthalmic vein.
What does foramen rotundum contain?
Maxilary division of trigeminal nerve (V2).
What does the foramen ovale contain?
Mandibular division of trigeminal nerve (V3).
What does the foramen spinosum contain?
Middle meningeal artery.
What does the middle meningeal artery supply with oxygen?
Dura mater.
What does the internal acoustic meatus contain?
Facial nerve (VII) and Vestibulocochlear nerve (VIII).
What does the jugular foramen contain?
Glossopharayngeal nerve (IX), Vagus nerve (X), Accessory nerve (XI).
What does the hypoglossal canal contain?
Hypoglossal nerve (XII).
What does the hypoglossal nerve innervate?
Tongue muscles.
What vein runs over the sternocleidomastoid muscle?
External jugular vein.
What are the 2 layers of the dura?
Periosteal and meningeal.
What is the largest dural venous sinus?
Superior sagittal sinus.
What is contained within the carotid sheath?
Internal jugular vein, common carotid artery and vagus nerve.
What divides the anterior and posterior triangles of the neck?
Sternocleidomastoid muscle.
What nerve innervates the sternocleidomastoid muscle?
Accessory nerve.
What does contraction of posterior crico-arytenoid muscles do?
Open/abduct vocal folds.
What does contraction of lateral crico-arytenoid muscles do?
Close/adduct vocal folds
What does contraction of cricothyroid muscle do?
Tense vocal folds and change pitch.
What are the divisions of the vagus nerve that innervate the larynx?
Superior laryngeal nerve and recurrent laryngeal nerve.
What does the superior laryngeal nerve divide into?
Internal and external laryngeal nerve.
A lesion to the internal laryngeal nerve causes what?
Loss of sensation above vocal folds.
A lesion to the external laryngeal nerve causes what?
Paralysis of cricothyroid muscle.
A lesion to recurrent laryngeal nerve causes what?
Paralysis in all muscle of larynx except cricothyroid and loss of sensation below vocal folds.
