L21 - Special Senses

Question 1

Special senses

Answer 1

1. Olfaction (chemoreceptors)
2. Gustation (chemoreceptors)
3. Vision (photoreceptors)
4. Hearing (Mechanoreceptors)
5. Equilibrium (Mechanoreceptors)

Question 2

3 Chambers of eye

Answer 2

1. Anterior = space between cornea and iris
2. Posterior = space between iris and anterior lens (TINY SPACE)
3. Vitreous = space posterior to lens (posterior cavity)

Question 3

Fluids of eye

Answer 3

Aqueous Humor
- Fills anterior and posterior space
- Regeneratable

Vitreous Humor
- Jelly-like fluid in posterior chamber (behind lens)
- Vitreous space, structure of eye
- Non-regeneratable

Question 4

3 Tunics layers

Answer 4

1. Fibrous (Sclera and cornea)
2. Uvea/vascular (Choroid, ciliary body-cantpin, iris)
3. Retina (Neural retina - photoreceptors + neurons, retinal pigment epithelium - supports neural)

Question 5

(2nd Tunic) Vascular Tunic

Answer 5

Choroid = absorbs scattered light
Ciliary body = has ciliary muscle
Iris = Smooth muscle across anterior lens
Pupil = Controls iris size

Question 6

Cornea

Answer 6

• must be no conjunctiva on cornea (so it is CLEAR)
• avascular (few blood vessels)
• GREATEST refractive power

Question 7

Lens

Answer 7

• elastic, flexible
• transparent gel threads, no nuclei
• little refractive power, can be altered

Question 8

Ciliary muscle

Answer 8

• Ciliary muscle contracts → suspensory ligaments slacken → lens rounder → more refraction (good for near vision) - Parasympathetic

When ciliary muscle relaxes → ligaments tighten → lens becomes flatter → less refraction (good for far vision) - Sympathetic

Question 9

2 muscles of iris

Answer 9

1. Sphincter [pupillae helps shrink pupil
2. Dilator pupillae helps dilate pupil

Question 10

2 types of photoreceptors

Answer 10

Rods
- Dim conditions
- No colour

Cones
- Colour vision
- In fovea
- Need more light for response

Question 11

Blind spot/Optic disc

Answer 11

site of entry/exit of optic nerve. no photoreceptors, so it can’t detect light.

Question 12

Conjunctiva

Answer 12

• Mucous membrane lubricating eye, inner surface of eyelid.
• NOT OVER CORNEA.
  e.g. when eye is red, my cornea (circle in middle) isn’t red

Question 13

Lacrimal apparatus (TEARS) - facial nerve

Answer 13

Maintains conjunctival surface and cornea. Moistens, cleans, provides nutrients, oxygen

Question 14

Accessory structures of eye

Answer 14

Palpebrae
Eyelashes
Tarsal plates/glands
Extrinsic eye muscles

Question 15

Optic nerve journey

Answer 15

1. Photoreceptors synapse with bipolar neurons (first-order) in retina.
2. Bipolar neurons synapse with ganglion cells (second-order) in retina.
3. Ganglion cell axons form the optic nerve, which meets at the optic chiasm.
4. Nasal retina fibers cross, temporal fibers stay, continue as optic tract.
5. Synapse at thalamus and 3rd order neurons travel to visual cortex.

Question 16

External ear purpose

Answer 16

• protection
• collection of sound waves

Question 17

External ear contains

Answer 17

1. Auricle (part we see)
2. External acoustic meatus (the canal)
3. Tympanic membrane (Separates middle and external ear)

Question 18

Tympanic membrane

Answer 18

• Made of epithelial membrane
• Separates external and middle ear (both air-filled)

Question 19

Middle ear

Answer 19

• Between tympanic and inner ear
• Air-filled
• Contains 3 ossicles (Malleus, incus, stapes)
• Continuous with auditory, eustachian, pharyngotympanic tube
• Connects to nasopharanx

Question 20

How ear works

Answer 20

1. Sound waves come into external ear and move tympanic membrane.
2. Ossicles in middle ear send vibrations into inner ear.
3. Vibrates oval window, leftover movement exits through round window

Question 21

3 windows/membranes of middle ear

Answer 21

1. tympanic
2. oval
3. round

Question 22

whys tympanic big and oval small?

Answer 22

concentrates force so it is more clear

Question 23

2 muscles that decrease movement of ear ossicles to protect tympanic and oval window

Answer 23

1. Tensor tympani
2. Stapedius

Question 24

Inner ear = hearing + vestibular

Answer 24

Vestibular (balance):
- semicircular canals and (CÚPULA)
- Vestibule contains utricle and saccule (MACULA)
- brainstem

Hearing:
- cochlea, and cochlear duct (contains spiral organ)
- temporal lobe

Question 25

Spiral organ in cochlear duct

Answer 25

- contains sensory receptors = hair cells (mechanoreceptors) - Pressure wave from endolymph causes stereocilia (hair cells) to move

Question 26

Process of ear

Answer 26

1. Sound waves through tympanic 2. Ear ossicles move, sound waves amplified 3. Through Oval window, wave in perilymph 4. Distortion of hair cells in basilar membrane (in spiral organ) 5. Impulses sent to Cochlear nerve 6. Remaining leaves through round window

Question 27

Perilymph vs endo

Answer 27

Endo = in cochlear duct and semicircular canals, surrounds hair cells Peri = in spiral organ

Question 28

3 semicircular ducts (each has a cupula) - direction sensitive, rotational

Answer 28

1. Anterior 2. Posterior 3. Lateral