1.6 Sensory organs Flashcards
How is the olfactive cavity structured?
- Composed of epithelium found in the nasal cavity interspersed between normal respiratory epithelium
- Made up of bipolar neurons that penetrate through the cribriform plate and terminate on the glomerulus
What is the glomeruli?
Aggregations/clusters of cells that pick up the same type of smell
How are the bipolar neurons arranged?
Different bipolar neurons for different smells are interspersed around the nasal cavity - once penetrated the cribriform plate, they converge on the same glomeruli
What is the function of the turbinate bones?
Host olfactory epithelium and respiratory epithelium
What is the function of supporting cells in the olfactory epithelium?
Secrete lipid-rich fluid mucus that entrap chemicals
What is the vomeronasal organ?
- Duct links nasal and oral cavities caudal to incisor teeth
- VNO are blind ending caudal sacs (bilateral)
What is the Flehmen reaction?
Pump air in and out
- sexual
How is taste transmitted?
Through the bipolar neurons - impulse moves through CN7 + CN9
Why is there no discrimination in glomerulus?
Brain has to discriminate neurons (individual) that terminate on the brain
Are the gustatory receptor cells singular or multiple?
Single receptor type
Where do the gustatory inputs link into?
- ingestion or food avoidance
- salivation, pre-absorbtive insulin release
- diuresis and apnoea when water in pharynx
What do the sympathetic fibres control in the eye?
Cause the pupil to expand
What do the parasympathetic fibres control in the eye?
Cause iris muscles to contract and become smaller
What is the transparent media?
Cornea, aqueous humour, lens and vitreous humour direct and converge light on the retina
What is the non - transparent media?
Choroid, uvea, sclera - support transparent media
What is the photosensitive layer?
Retina made up of rod and cones
How does signal transduction take place?
Light splits rhodopsin in rods and cones which causes a signal transduction on neuronal fibres which generates information (vision)
Sodium channels are opened, cascade events take place, rhodopsin changes from a Cis → Trans form
What is the outer ear made up of?
Pinna (leading to ear canal - external acoustic meatus) ends @ tympanic membrane (eardrum)
- air but no fluid
What is the middle ear made up of?
Three bones
- Malleus
- Incus
- Stapes
- air but no fluid
What is the inner ear made up of?
Cochlea (sound transduction), semicircular canals + (utriculus + saccule) = maculae - responsible for balance and posture
- has a fluid medium, though the movement of this cause the refraction of sound as the hair cells are also deflected allowing the movement of sound
What are the two functions of the ear?
Auditory system = sound
Vestibular system = balance/locomotor
How is the ear involved in sound detection?
Outer ear: sound collected from external auditory canal to tympanic canal and tympanic membrane
Middle ear: Maleus, Incus and Stapes conducts sound to oval window
Inner ear: Oval window transmits waves to the cochlea and then to the brain through CNVIII
How is the ear involved in balance and motion?
Semicircular canals detect angular movement while maculae detect linear acceleration
What is the cochlea made up of?
Basilar membrane - shearing effect sends signals through vestibular + cochlea nerve
Organ of Corti - responsible for sound detection
Hair cells - discharge electrical impulses through the cranial nerve
CN VIII - vestibular cochlea
What is the role of the semi-circular canal in sound production?
Force of inertia causes flow of fluid in cavity in opposite direction which binds the cupula + hair cells which discharges electrical signals that will be sent
What is the semicircular canal made up of?
Cupula - contains hair cells covered in a gelatinous cupula
Hair cells
CN VIII
What are the saccule and utricle made up of?
Deflected ↓ if going ↑ Deflected ↑ if going ↓ Maculae Hair cells which are positioned at 90 degrees to each other CN VII
