Senses

Question 1

What are the 4 conditions that must be satisfied for a sensation to occur?

Answer 1

1) A stimulus or change in the environment that activates a sensory receptor
2) Convert the signal to an electrical signal which produces nerve impulses
3) Nerve impulse must be conducted along a neural pathway to the brain
4) The region of the brain must then receive and integrate the nerve impulse into a sensation

Question 2

What protects the eye?

Answer 2

• Eyelids - blink reflex protects the eye and spreads fluid across the eye
• Bony structure - socket
• Tear ducts/ glands - tears contain salts,mucus and lysozyme to clean and lubricate the eye
• Eyelashes/ eyebrows - protect the eye from sweat and UV rays

Question 3

How does the eye move?

Answer 3

6 external eye muscles act together to rotate the eyeball in its socket. They form an incomplete cone shape around and behind the eye. Movement of both eyes is synchronised - this can be voluntary or was a reflex

Question 4

How many rods are there and how do they work?

Answer 4

120 millions rods contain rhodopsin and perceive shades of grey. In bright light the rhodopsin splits faster into open and retinal then I reforms; this reduces vision. loss of rods can cause night blindness

Question 5

How many cones are there and how do they work?

Answer 5

6 million cones contain retinal and 1 of 3 proteins for red, green or blue vision. Important for fine details and colour vision in bright light.

Question 6

What are the 3 types of cells in the olfactory epithelium?

Answer 6

• Olfactory receptor cells
• Supporting cells
• Basal cels

Question 7

What is the olfactory pathway?

Answer 7

On each side of the nose, 40 bundles of unmyelinated axons of olfactory receptor cells pass through 20 holes in the ethmoid bone and terminate in one of the 2 olfactory bulbs. Some project to the temporal lobe of the cerebral cortex, others project the limbic system and hypothalamus.

Question 8

What makes up the outer ear?

Answer 8

• The external pinna (or auricle) collects sound waves and channels them inwards. The pinna is made of elastic cartilage covered by skin
• The external auditory canal ends at the tympanic membrane.

Question 9

What makes up the middles ear?

Answer 9

The ossicles are the smallest bones in the body. they multiply the amplitude of vibration 15 - 20 times. This air filled cavity is connected to the nasopharynx via the pharyngotympanic or eustacian tube

Question 10

What makes up the inner ear?

Answer 10

Outer bony labyrinth - a sense of cavities in the temporal bone; filled with perilymph
Inner membraneous labyrinth - filled with endolymph
This consists of the cochlea, vestibules and semi - circular canals

Question 11

What are the semi circular canals?

Answer 11

The 3 semi circular canals lie at right angles to each other; they detect rotations. All 3 canals open at both ends, into the utricle

Question 12

What is the organ of corti?

Answer 12

The spinal organ of corti rests between the basilar membrane and the gelatinous, tectorial membrane, which covers the hairs. It consists of supporting cells, inner hair cells and outer hair cells

Question 13

What are the 5 primary tastes?

Answer 13

• Sour
• Bitter
• Sweet
• Salty
• Umani (savoury)

Question 14

What are the 4 types of papillae?

Answer 14

• Vallate
• Fungiform
• Filiform
• Foliate