1.6 Sensory organs

Question 1

How is the olfactive cavity structured?

Answer 1

1. Composed of epithelium found in the nasal cavity interspersed between normal respiratory epithelium
2. Made up of bipolar neurons that penetrate through the cribriform plate and terminate on the glomerulus

Question 2

What is the glomeruli?

Answer 2

Aggregations/clusters of cells that pick up the same type of smell

Question 3

How are the bipolar neurons arranged?

Answer 3

Different bipolar neurons for different smells are interspersed around the nasal cavity - once penetrated the cribriform plate, they converge on the same glomeruli

Question 4

What is the function of the turbinate bones?

Answer 4

Host olfactory epithelium and respiratory epithelium

Question 5

What is the function of supporting cells in the olfactory epithelium?

Answer 5

Secrete lipid-rich fluid mucus that entrap chemicals

Question 6

What is the vomeronasal organ?

Answer 6

1. Duct links nasal and oral cavities caudal to incisor teeth
2. VNO are blind ending caudal sacs (bilateral)

Question 7

What is the Flehmen reaction?

Answer 7

Pump air in and out

- sexual

Question 8

How is taste transmitted?

Answer 8

Through the bipolar neurons - impulse moves through CN7 + CN9

Question 9

Why is there no discrimination in glomerulus?

Answer 9

Brain has to discriminate neurons (individual) that terminate on the brain

Question 10

Are the gustatory receptor cells singular or multiple?

Answer 10

Single receptor type

Question 11

Where do the gustatory inputs link into?

Answer 11

• ingestion or food avoidance
• salivation, pre-absorbtive insulin release
• diuresis and apnoea when water in pharynx

Question 12

What do the sympathetic fibres control in the eye?

Answer 12

Cause the pupil to expand

Question 13

What do the parasympathetic fibres control in the eye?

Answer 13

Cause iris muscles to contract and become smaller

Question 14

What is the transparent media?

Answer 14

Cornea, aqueous humour, lens and vitreous humour direct and converge light on the retina

Question 15

What is the non - transparent media?

Answer 15

Choroid, uvea, sclera - support transparent media

Question 16

What is the photosensitive layer?

Answer 16

Retina made up of rod and cones

Question 17

How does signal transduction take place?

Answer 17

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

Question 18

What is the outer ear made up of?

Answer 18

Pinna (leading to ear canal - external acoustic meatus) ends @ tympanic membrane (eardrum)
- air but no fluid

Question 19

What is the middle ear made up of?

Answer 19

Three bones

1. Malleus
2. Incus
3. Stapes
   - air but no fluid

Question 20

What is the inner ear made up of?

Answer 20

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

Question 21

What are the two functions of the ear?

Answer 21

Auditory system = sound

Vestibular system = balance/locomotor

Question 22

How is the ear involved in sound detection?

Answer 22

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

Question 23

How is the ear involved in balance and motion?

Answer 23

Semicircular canals detect angular movement while maculae detect linear acceleration

Question 24

What is the cochlea made up of?

Answer 24

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

Question 25

What is the role of the semi-circular canal in sound production?

Answer 25

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

Question 26

What is the semicircular canal made up of?

Answer 26

Cupula - contains hair cells covered in a gelatinous cupula
Hair cells
CN VIII

Question 27

What are the saccule and utricle made up of?

Answer 27

Deflected ↓ if going ↑
Deflected ↑ if going ↓ 
Maculae 
Hair cells which are positioned at 90 degrees to each other 
CN VII