Sense organs

Question 1

Explain the role of the ‘stapedius’

Answer 1

A small muscle stop & reduce/ cushion large vibrations and is innervated by the facial nerve -> hence auditory symptoms in Bell’s palsy. (excessive sound due to the loss of cushion by stapedius)

Question 2

Describe specifically the structure of the inner ear.

Answer 2

called the labyrinth because of its complicated series of canals. Consists of an outer bony labyrinth that encloses an inner membranous labyrinth:
3 semicircular canals & vestibule (receptors for balance).

Question 3

Describe how ‘stereocilia’ trigger an electrical impulse

Answer 3

Fluid movement (vibration) causes stereocilia movement and initiates an electrical impulse.

Question 4

Name which cranial nerve provides sensory information for hearing and balance

Answer 4

The vestibulocochlear nerve (cranial nerve VIII) provides sensory information for hearing and balance.

Question 5

Describe in specific detail how external sound waves are perceived as ‘sound’ in the cerebrum of the brain

Answer 5

Sound wave (pressure waves) - > Mechanical vibration -> Fluid waves -> Nerve Impulse-> cerebrum

Question 6

List TWO functions of the Eustachian tube

Answer 6

1. Ventilate the middle ear,
2. Equalize pressure in middle ear (to avoid damage with pressure changes).
3. Drain mucus

Question 7

Explain why children are more prone to middle ear infections

Answer 7

Eustachian tubes and is a common route for infection to spread between the pharynx and middle ear (more horizontal, flat & short in children).

Question 8

Describe the structure of the ‘otolithic’ membrane’

Answer 8

A dense layer of calcium carbonate crystals extends over and rests on the hairs

Question 9

Name the THREE layers of the eyeball

Answer 9

Outer Layer: Sclera
Middle Layer: Uvea
Inner Layer: Retina

Question 10

Describe the main role of the ‘iris’

Answer 10

Iris controls the amount of light reaching the retina by adjusting pupil size.

Question 11

Describe how the following protect the eye : Eyebrows

Answer 11

Prevent sweat / materials entering eye.

Question 12

Describe how the following protect the eye: Eyelids/eyelashes

Answer 12

Eyelids: Spread secretions over eye, Eyelashes: trap small particles to protect the eye.

Question 13

Describe how the following protect the eye: Conjunctiva

Answer 13

Thin transparent mucous membrane of columnar epithelial cells lining the internal eyelids and anterior eyeball, protects the cornea. and secrete oily material to lubricate eyeball

Question 14

Describe how the following protect the eye: Lacrimal apparatus

Answer 14

They protect the eye from infection and by tear lubricate movements of the eye.

Question 15

Describe how the following protect the eye: Blinking

Answer 15

•Blinking spreads tears and closing the eyelid protects from injury.

Question 16

List THREE ways in which clear vision is achieved by the eyes

Answer 16

To achieve clear vision light must be focused on to the retina. This involves:

• Refraction of the light rays.
• *- Accommodation of the eyes.**
• *- Changing the size of the pupils.**

Question 17

Name ONE eye component that refracts most light rays

Answer 17

Cornea

Question 18

Describe in detail the difference between:

a. Greater refraction
b. Less refraction

(HINT: Think ciliary muscles, lens and suspensory ligaments)

Answer 18

a. When an object is close, the ciliary muscle contracts. This reduces suspensory ligament tension and the lens becomes more convex -> greater refraction.

b. When an object is distant, the ciliary muscle relaxes, increasing the tension on the suspensory ligaments and flattening the lens -> less refraction.
•Looking at near objects tires the eyes (use of the ciliary muscle).

Question 19

Describe how the pupil size is affected by:

a. Sympathetic nervous system
b. Parasympathetic nervous system

Answer 19

a. Sympathetic stimulation contracts the radial muscle fibres to dilate the pupils.
b. Parasympathetic stimulation contracts the circular muscle fibres to constrict the pupils.

Question 20

1. Name one investigative tool that can be used to view the retina
2. Name the location where the optic nerve exits the eyeball

Answer 20

1. Ophthalmoscope
2. Optic disc or blind spot

Question 21

List TWO layers of the retina

Answer 21

1. Pigmented layer
2. Photoreceptors layers

Question 22

Describe THREE differences between ‘rod cells’ and ‘cone cells’

Answer 22

1. Rode cells have a rode appearance and cone cells cone appearance
2. Rode: provide black, white greyscale/ Cone: Blue, red & green scale
3. Rode: 120 million cells / Cone: 6 million

Question 23

Describe TWO features of the ‘fovea centralis’

Answer 23

‘Fovea centralis’ :

• contains only cone cells.
• Area of highest visual acuity (this is why we move our eyes and head to look at things).

Question 24

1. State where Vitamin A is stored in the eye
2. Name the protein bound to Vitamin A in the eye

Answer 24

1. the pigmented layer of the retina stores vit. A.
2. Opsin

Question 25

Describe how the eyes adjust in the following situations:

a. Moving from dark to light sensitivity
b. Moving from light to dark sensitivity

Answer 25

a. Dark to light, the eyes adjust quite quickly -> ‘light adaptation’. decreasing its sensitivity.
b. Light to dark : increases slowly over some minutes. Photopigments take time to regenerate.

Question 26

Name the cranial nerve responsible for sense of smell

Answer 26

Olfactory nerve (CN I)

Question 27

Name the cranial nerve which innervates the tongue.

Answer 27

Hypoglossal nerve (CN XII).

Question 28

Explain what is meant by ‘papillae’

Answer 28

Papillae : Taste buds in elevations on the tongue: gripping food & taste

Question 29

Describe the difference between the following:

a. Circumvallate papillae
b. Fungiform papillae
c. Foliate papillae

Answer 29

a. Circumvallate: the largest at the back of the tongue
b. Fungiform: mushroom shaped all over the tongue
c. Foliate: at the margins of the tongue but most degenerate in childhood (breastfeeding, milk)

Question 30

1. Name TWO cranial nerves involved in taste physiology.
2. Name ONE cranial nerves involved in touch/ sensation

Answer 30

1. The facial nerve / glossopharyngeal nerve innervates both taste and general sensation of the posterior one-third of the tongue.
2. The trigeminal nerve supplies general sensation to the anterior two-thirds of the tongue.
   • The vagus nerve innervates the throat and epiglottis.

Question 31

List TWO main functions of the inner ear.

Answer 31

Receptors for balance semicircular & vestibule canals and hearing (cochlea)

Question 32

List THREE ways in which the cerebellum can make postural adjustments to maintain balance

Answer 32

1. Vestibular system (inner ear) -Head position
2. Visual feedback (from eyes) _{⇒ Need B12}
3. Proprioceptors in skeletal muscles, joints & ligaments

Question 33

What 2 bones in the inner ear send neve impulses for balance?

Answer 33

Vestibule and semicircular canals

Question 34

Explain how tears play an important immune role

Answer 34

Tears contain IgA and lysozymes

Question 35

Name the cranial nerve that controls tear secretion

Answer 35

Tears are secreted under the control of the trigeminal nerve (CN V).

Question 36

List two food sources of:

• Pre-formed vitamin A
• Carotenoids

Answer 36

• liver, eggs
• Fruits/ Veggies

Question 37

Explain why carotenoids are not considered to be toxic

Answer 37

because absorption is regulated

Question 38

What is meant by optic disc?

Answer 38

where optic nerve exit the eyeball