Week 1 Flashcards
How are the senses of taste and smell stimulated
Buy chemoreceptors (sensory receptor cells) binding to particular chemicals
Function of taste and smell
Protects us from poisons / spoiled food
Influences the flow of digestive juice
Smell can influence taste
Where are the sensory receptor cells for taste mainly packaged in
Taste buds
What does a taste bud consist of
Taste receptor cells
Support cells between taste receptor cells
Basal cells
Afferent nerve fibres
How long is the life span of taste receptor cells and what happens when it dies
10 days
Basal cells will differentiate into new taste receptor cells and replace the old one
Where are taste buds located at
Tongue
Pharynx
Epiglottis
Palate
Where are taste buds mostly located at
In papillae in the tongue
What are papillae seen as on tongue
Raised bumps or little red dots
4 types of papillae
Filliform
Fungiform
Vallate
Foliate
Which papillae contain taste buds
Fungiform
Vallate
Foliate
Which papillae is the most abundant
Filliform but it does not contain taste buds
How does action potentials travel from taste receptor cells to the brainstem
- Chemicals trigger the Taste receptor cells to produce action potentials
- Action potentials travel through the afferent nerve fibres
- to cranial nerves (V / IX / X)
- Action potential is then conveyed by the cranial nerves to cortical gustatory areas
What is cortical gustatory areas
Region of cerebral cortex responsible for the perception of taste
What are the cranial nerves involved in transmitting signals from afferent taste nerve fibres
Chorda tympani branch of facial nerve CN VII
Glossopharyngeal nerve CN IX
Vagus nerve CN X
Taste signals from where are conveyed to the brainstem via chorda tympani branch of facial nerve
Anterior 2/3 of the tongue (innervated by chorda tympani)
Taste signals from which part are conveyed to the brainstem via glossopharyngeal nerve
posterior 1/3 of the tongue
Taste signals from which part are conveyed to the brainstem via vagus nerve
Epiglottis
Pharynx
Why may patients who had undergone middle ear surgery experience an alteration to sense of taste
Because the facial nerve is closely related to the middle ear hence if it can damaged during the surgery and taste will be altered
What is bitter taste stimulated by
Alkaloids
Poisonous substances
toxic plant derivatives
What is the sour taste stimulated by
High amounts of free H+
What is the salty taste stimulated by
NaCl
What is the sweet taste stimulated by
Glucose
What is umami taste stimulated by
Amino acids especially glutamine
What is ageusia
Loss of taste
What can cause ageusia
Nerve damage
Glossitis
Radiation
Tobacco
Endocrine disorders
What is hypogeusia
Reduced taste function
What can cause hypogeusia
Chemotherapy
Medications
What is dysgeusia
Distortion of taste
Causes of dysgeusia
Glossitis
Gum infections
URTI
Medications
Chemotherapy
Neoplasms
Zinc deficiency
What are the 2 main cranial nerves involved in the sense of smell
Olfactory Nerve CN I
Trigeminal Nerve CN V
What is the difference between the types of smells that each cranial nerve is involved in
CN I is involved in common odours such as rose, chocolate, mint whereas CN V is involved in chemical stimulus such as smells that irritates you (ammonia) , burning, cooling
If you smelled something harmful, which nerve is involved to stop inhalation and why does it do it
CN V (trigeminal)
to protect the lungs
Where is the olfactory neuroepithelium located at
At the top of each nasal cavity
Does all the air breathed in reaches the olfactory neuroepithelium
No, only 10-15% reach the neuroepithelium. Most of the air goes down the nasopharynx into the airways
How is the smell of the food enhanced by swallowing
Due to retrograde airflow from the nasopharynx back to the nasal cavity
How does air reach the olfactory mucosa during quiet breathing
Because the olfactory mucosa is above the normal path of airflow, the air reaches above by diffusion
How does sniffing enhance smelling
Draws air currents upwards to the olfactory mucosa
What features does a substance must have in order to be smelled
Volatile
Water soluble
Why does the substance need to be water soluble in order to be smelled
So it can dissolve in the mucous which coats the olfactory mucosa
Function of the mucous coating the olfactory mucosa
Ensures moist environment and protection
Disperses odour substances to the olfactory receptors
How are odour substances transported to the receptors after it enters the mucous
Diffuse or by specialised proteins
What happens if you have too little mucous around your olfactory mucosa
Dry
Reduced sense of smell
What type of epithelium does the olfactory mucosa have
Pseudostratified columnar epithelium
What does the olfactory mucosa contain
Bi-polar neurones- receptor cells extend its axons on both sides
Supporting cells
Basal cells
Duct cell of Bowmans glands
Function of supporting cell in the olfactory mucosa
To protect the receptor cells
Function of duct cell of Bowmans glands
Secrete mucous that coats the olfactory mucosa
The axons of the olfactory receptor cells collectively form the
Afferent fibres of olfactory nerve
Describe how we smell
- Air containing odourants enters the nasal cavity and diffuse / drawn up to (by sniffing) the olfactory mucosa
- Odourants dissolves into the mucous that is coating the olfactory mucosa, becoming aqueous
- Aqueous odourants are picked up by the receptor cells
- Action potential fired from the receptor cells to the olfactory bulb via afferent fibres of olfactory nerve
- The chemical stimuli is converted into neural stimuli in the olfactory bulb then sent to the brain
Which part of the brain does olfactory bulb neuron’s pass the stimuli to
Temporal lobe
Olfactory areas
What is anosmia
Inability to smell
What is hyposmia
Reduced ability to smell
What is dysosmia
Altered sense of smell
What is phantosmia
Smell perceived in the absence of stimulus (olfactory hallucination)
Aetiology of abnormalities in smell can be
Conductive or sensorineural
What does it mean when an abnormality in smell is due to conductive reasons
Due to something blocking the molecules from getting to the olfactory mucosa
Examples of conductive reasons in abnormalities of smell
Polyps
Discharge
Mucous
What does it mean when an abnormality in smell is due to sensorineural reasons
Due to problems with the olfactory nerves / olfactory bulb itself
Examples of sensorineural reasons in abnormalities of smell
Head injuries
Neurological conditions (parkinson, alzheimers)
Brain tumours
Medications
What is UPSIT
Objective testing for sense of smell; clinicians asks patients to smell certain things then ask the patient to fill in the answer
What is epistaxis
Nose bleed
Causes of epistaxis
Idiopathic
Injury
Foreign bodies
Tumour
Inflammation
Hereditary hemorrhagic telangiectasia
Coagulopathy
Drug use
What is hereditary hemorrhagic telangiectasia
Autosomal dominant disorder that leads to abnormal formation of the vessels
Examples of coagulopathy
thrombocytopenia
Arteries that supplies the nasal cavity branched off from
Internal and External carotid arteries
Which artery that supplies the nasal cavity branched off from the internal carotid artery
Ophthalmic artery which branches off into anterior and posterior ethmoidal arteries
Which arteries that supply the nasal cavity branched off from the external carotid artery
Maxillary artery which branches -> sphenopalatine and greater palatine arteries
Facial artery which branches -> superior labial artery and lateral nasal artery
Where does epistaxis usually originate from
Kiesselbach’s plexus at nasal septum
Kiesselbach’s plexus is formed by which arteries
Anterior ethmoidal atery
Posterior ethmoidal artery
Sphenopalatine artery
Greater palatine artery
Septal branch of superior labial artery
Sometimes, the bleeding may originate from the posterior nasal cavity. Which artery is responsible
Sphenopalatine
Anterior or posterior epistaxis bleeds more profusely
Posterior
Management sequence for epistaxis
- Conservative (pressure, ice, drugs
- Nasal cautery
- Nasal packing
What is the conservative management for epistaxis
Apply external pressure to soft part of the nose
Ice pack on forehead or neck
Topical vasoconstrictors +/- lignocaine
Reversal of anti-coagulants
What should the position of the patient be when managing epistaxis conservatively
leaning forward
What should the patient do if there is blood in their mouth due to epistaxis?
Spit it out
What may happen if the patient swallows too much blood
Nausea and vomiting because blood is an emetic
Examples of anti coagulant
Warfarin
Rivaroxaban
Dabigatran
What is nasal cautery
Cauter the damaged vessel using silver nitrate stick
What can make nasal cautery difficult to perform
Heavy bleeding
Cannot identify the bleeding point
When is nasal packing used
Heavy bleeding unresolved by nasal cautery
Bleeding points that cannot be identified so cannot undergo nasal cautery
Examples of nasal packings
Nasal tampons
Rapid rhino
Why should nasal packing be avoided if possible
Because it requires hospital admission for observation
How is profuse epistaxis caused by posterior bleeding mostly treated
By ligation;
Sphenopalatine artery ligation
Which group of patients who presented with epistaxis should you suspect to have underlying conditions
Young children under 2
Elderly (cancer risk is higher) with recurrent epistaxis
Family history of hereditary haemorrhagic telangiectasia
Signs of cancer
What should you suspect in young children under 2 who present with epistaxis
NAI or underlying conditions because epistaxis usually does not occur in young children under 2
What are the nerves that can cause referred otalgia
Trigeminal (CN V3)
Vagus
Facial
Glossopharyngeal
Spinal nerve C2 C3
Why is CN V3 the only branch involved in referred otalgia
Because it is the only branch that provides general sensory innervation to the external ear
CN V3 provides general sensory innervation to
External ear
Lower lip
Chin
General sensation to anterior 2/3 of tongue
Lower molar, incisor and canine teeth
Lower gingiva
3 salivary glands
Name the branch of CN V3 that gives general sensory innervation to anterior 2/3 of tongue
Lingual nerve
Which branch of CN V3 innervates the external ear
Auriculotemporal nerve
What pathologies can cause referred otalgia due to CN V3
Lower teeth cavities, abscesses
Salivary gland infections / neoplasm
Anterior 2/3 of tongue infections / injury (piercings)
Which branch of the facial nerve gives general sensory innervation to the external ear
Posterior auricular branch
Other branches of facial nerve gives general sensory innervation to
Ethmoid sinus
Maxillary sinus
Nasal mucosa
Name the branches that gives general sensory innervation to ethmoid and maxillary sinuses and nasal mucosa
Vivian nerve
Greater petrosal nerve
pathologies that can cause referred otalgia due to facial nerve
Ethmoid / maxillary sinusitis
Nasal pathologies - foreign bodies
Vagus nerve gives general sensory innervation to
Inferior aspect of laryngopharynx
Inferior parts of external ear canal and tympanic membrane
Where is piriform fossa located at
Posterolaterally to each side of the laryngeal inlet
Pathologies that can cause referred otalgia due to vagus nerve
Foreign body in piriform fossa (e.g. fishbones)
Carcinoma of the larynx or piriform fossa
Piriform abscess
Glossopharyngeal nerve provides general sensory innervation to
Middle cavity
Superior part of tympanic membrane
Oropharynx
Posterior 1/3 of tongue
Tonsils
Pathologies that can cause referred otalgia due to glossopharyngeal nerve
Tonsilitis
post-tonsillectomy
Carcinoma at posterior 1/3 of the tonguee
Which branches of C2 and C3 are involved in giving general sensory in innervating the external ear
Lesser occiptal
Greater auricular
Pathologies that can lead to referred otalgia due to spinal nerves C2 and C3
Cervical neuritis
Herpes zoster
