Special Senses

Question 1

What is olfaction?

Answer 1

Sense of smell

Question 2

Where are olfactory receptors located?

Answer 2

Dendrites of olfactory sensory neurons in the olfactory epithelium.

Question 3

What type of stimulus does olfactory receptors detect?

Answer 3

Chemical stimuli- odorant molecule.

Question 4

How does olfactory receptors respond to stimulus?

Answer 4

1) Odorant molecule binds to
2) G-protein coupler receptor
3) Opens Na+ and Ca2+ channels
4) Na+ and Ca2+ enters neutron
5) Triggers series of events that contributes to
6) Depolarisation
7) Action Potential

Question 5

Which cranial nerve transmits olfactory information to the brain and what is the most important destination for olfactory information in the brain?

Answer 5

• Olfactory nerve.

- Olfactory cortex.

Question 6

What is gustation?

Answer 6

Sense of taste.

Question 7

What are taste receptor cells?

Answer 7

• Present primarily on the upper surface of the tongue.
• Helps give person sensation of taste.
• Located within taste buds.
• ‘Gustatory epithelial cell’= type of specialized epithelial cell.
• Forms synapses with sensory neurons, which then synapse with basal cells & taste receptor cells.
• Single taste receptor cell responds primarily to just one of 5 basic tastes

Question 8

How does depolarisation of taste receptor cells lead to discharge of action potentials in sensory neurons (salt/sour)?

Answer 8

1) Na+ in salt (NaCl) or H+ in sour (acidic) food.
2) Enter taste receptor cells via Na+ or H+ leak channels
3) Depolarisation of taste receptor cell
4) Taste receptor cell releases neurotransmitter (serotonin)
5) Neurotransmitter stimulates sensory neuron
6) Depolarisation and action potentials in sensory neuron

Question 9

How does depolarisation of taste receptor cells lead to discharge of action potentials in sensory neurons (sweet/bitter/umami)?

Answer 9

1) Sweet, bitter or umami molecules in food
2) Bind to g-protein coupled receptor on taste receptor cell
3) Depolarisation of taste receptor cell
4) Taste receptor cell releases neurotransmitter (ATP)
5) Neurotransmitter stimulates sensory neuron
6) Depolarisation and action potentials in sensory neuron

Question 10

Which cranial nerves transmit gustatory information and where does gustatory information end up in cerebral cortex?

Answer 10

• Cranial nerves: Facial, Glossopharyngeal and Vagus.

- Gustatory information ends up in primary gustatory cortex.

Question 11

What is equilibrium?

Answer 11

Sense of physical balance.

Question 12

What are hair cells for equilibrium ?

Answer 12

Receptors in ampulla detecting rotational movements of head.

Question 13

Where are hair cells found for equilibrium?

Answer 13

Ampulla of semicircular ducts.

Question 14

What type of stimulus does each set of hair cells detect?

Answer 14

• Hair cells in posterior semicircular duct detect head titling from side to side.
• Lateral duct horizontal rotation.
• Anterior duct vertical rotation.

Question 15

How do hair cells detect a stimulus

Answer 15

Bending cilia in preferred direction depolarises hair cell and bending in opposite direction hyperpolarises hair cell

Question 16

What is the vestibule and what is its role?

Answer 16

• Consists of 2 membranous sacs (saccule and utricle)
• Contains a region called maculae contains receptors (hair cells) that are embedded in a gelatinous material that is covered in calcium carbonate crystals (otoliths)
• Detect head position with respect to gravity and linear acceleration.

Question 17

Which cranial nerve transmits balance (vestibular) information to the brainstem and why does this information end up in so many brain regions?

Answer 17

-Cranial Nerves: oculomotor, trigeminal, abducens.
Diversity of projections enable us to:
-Adjust peripheral muscles (i.e. muscles that maintain standing posture via reticulospinal tract).
-Conscious sense of head position and movement.
-Keep our eyes focused on specific point when head is moving (by adjusting eye movement

Question 18

What is hearing?

Answer 18

Perception of sound

Question 19

What does hair cells detect in the ear?

Answer 19

• Frequency (number) of pressure waves per second (hertz): ‘pitch’ of sound.
• Amplitude of pressure waves (decibels). Intensity or volume of sound.

Question 20

What causes hair cells in ear to depolarise

Answer 20

-Displace in left direction stimulates (depolarises) hair cells

Question 21

Describe the 6 steps involved in the perception of sound

Answer 21

1. Sound waves arrive at lympanic membrane.
2. Movement of the lympanic membrane causes displacement of the auditory ossicles.
3. Movement of the stapes at oval window establishes pressure waves in perilymph of the scala vestibuli.
4. Pressure waves distort the basilar membrane on their way to the round window of scala tympani.
5. Vibration of the basilar membrane cause vibration of hair cells against tectorial membrane.
6. Information about the region and intensity of stimulation is relayed to CNS over cochlear nerve.

Question 22

Where does auditory (sound) information project to in the cerebral cortex

Answer 22

Pressure waves enter cochlea via oval window and exit cochlea via round window.

Question 23

What is vision?

Answer 23

Perception of sight

Question 24

What are the two parts of the retina and where the photoreceptors found?

Answer 24

2 layers of Retina: Pigmented Part and Neural Part.

-Photoreceptors in pigmented part of retina

Question 25

What are the two types of photoreceptors and what type of stimulus do they respond to?

Answer 25

Cones & Rods
-Highest density of cones: center of visual axis (macular and fovea).
-Highest density of rods: periphery (away from center of visual axis).
Detect photons (basic units of visible light)
- Rods detect if photons are present (light) or not (dark).
-Cones provide information about the wavelength of the photons (color).

Question 26

Where does processing of visual information occur (retina and brain) & How does visual information travel from the retina to the primary visual cortex?

Answer 26

• Visual information leaves the retina via axons of ganglions cells that travel in optic nerve.
• Axons in optic nerve may or may not cross the midline on their way to synapse onto neurons in the lateral geniculate nucleus of the thalamus.
• Neurons in lateral geniculate nucleus of thalamus project to the primary visual cortex.

Question 27

What is the dorsal stream?

Answer 27

Dorsal Stream: Primary visual cortex to structures in parietal lobe.
-Analysis of visual motion. Visual control of action.

Question 28

What is the ventral stream?

Answer 28

Ventral Stream: Primary visual cortex to structures in temporal lobe.
- Perception of visual world. Recognition of objects.