Weeks 10-12

Question 1

Somatosensory system

Answer 1

Responds to the EXTERNAL environment. (E.g. touch, temp, pain)

Cerebrum, cerebellum, brainstem and spinal cord

Question 2

Viscerosensory system

Answer 2

Responds to the internal environment

Question 3

3 classes of somatosensory receptors

Answer 3

Tactile sensations (mechanoreceptors)

Thermal sensations (thermoreceptors)

Nociceptive (painful) sensations (mechanical, thermal and polymodal nociceptors)

Question 4

Where are the meissner corpuscle and merkel’s disks located.

Answer 4

Epidermis

Meissner b/t dermal pupillae.

Merkels aligned with dermal pupillae.

Question 5

Where are pacinian corpuscles located

Answer 5

Subcutaneous tissue.

Question 6

Where are ruffini’s corpuscles located

Answer 6

Deep in the dermis (20% of skin receptors)

Question 7

Meissner’s corpuscle

Answer 7

LOW FREQ VIBRATIONS.

Looping axonal terminals.

Question 8

Merkel’s disks

Answer 8

SMALL FORMS AND SHAPES.

Dome structure

Question 9

Pacinian corpuscle

Answer 9

HIGH FREQ VIBRATIONS.

Sensory axon surrounded by fluid filled capsule

Question 10

Ruffini’s corpuscle

Answer 10

PRESSURE.

Nerve terminals and collagen fibrils.

Question 11

Free nerve endings

Answer 11

NOXIOUS (HARMFUL)

Penetrate into epithelial cells

Question 12

Stages of sensory transduction

Answer 12

1) Stimulus changes nerve ending.
2) Alters the membrane permeability of receptor membrane.
3) Produces receptors (generator) potential.
4) Triggers AP.

Question 13

Out of mechanoreceptors, nociceptors and thermoreceptors which are fast and slow afferents

Answer 13

Mechanoreceptors are fast.

Nociceptors and thermoreceptors are slow due to small diameter.

Question 14

Describe the 3 neurone chain in a mechanosensory pathway

Answer 14

1st order neurone: Primary afferent (into dorsal horn, spinal cord)

2nd order neurone: Central neurone (to thalamus)

3rd order neurone: Central neurone (to cortex)

Question 15

Where is the primary somatosensory cortex located?

Answer 15

Post central gyrus

Question 16

Where does the transduction of a painful stimulus occur

Answer 16

Free nerve endings of unmyelinated C fibres and thinly myelinated Ad fibres.

Question 17

What do pain afferents release?

Answer 17

NT glutamate and vesicles containing the neuropeptide substance P

Question 18

Where does the mechanosensory pathway cross over?

Answer 18

Decussates at the medulla.

Question 19

Where does the pain pathway cross over?

Answer 19

Decussates at the dorsal horn.

Contralateral pathway

Question 20

What structure is responsible for your blind spot?

Answer 20

Optic disc - where optic nerve axons leave the eye

Question 21

What are the two types of photoreceptors and their role?

Answer 21

Convert light energy to neural activity.

Cone cells: Colour vision (large number in fovea)

Rod cells: Achromatic (without colour), more sensitive to light (periphery of retina)

Question 22

What is the role of bipolar cells in the retina?

Answer 22

Create pathway from photoreceptors to ganglion cells.

Question 23

Amacrine/horizontal cells

Answer 23

Indirect pathways (modulators)

Question 24

Retinal ganglion cells

Answer 24

Axons leave the eye to form optic nerve

Question 25

Signal transduction in photoreceptors.

Answer 25

Light stimulus causes a change in protein conformation.

Binds GTP.

Decreases 2nd messenger.

Decrease Na+ conductance.

Question 26

What order does the optic nerve differentiate (branch off)?

Answer 26

Optic chiasm

Hypothalamus

Pretectum

Lateral geniculate
nucleus

Superior colliculus

Question 27

Where do sound waves turn into nerve signals?

Answer 27

Waves travel down external auditory meatus. Meets tympanic membrane.
Pressure waves are turned into nerve signals at the cochlea.

Question 28

How do we detect sound?

Answer 28

Within the scala media. Vibration cause the organ of corti to move. The tectoral membrane distorts the cilia of inner hair cells (sensory receptors)

Question 29

How does sound get converted into nerve impulses

Answer 29

Stereocilia are disturbed by movement causing mechano-electrical transduction.

The endolymph of scala media has a high [K+] and opening of channel causes depolarisation.

Depolarisation opens voltage gates Ca2+ channels. Causing NT release through afferent nerves.

Question 30

Where is the auditory complex located in the brain?

Answer 30

Superior temporal gyrus.

In temporal lobe.

Question 31

Olfactory sensory transduction

Answer 31

Odourant binds to receptors on cilia.

G protein activated and production of cAMP.

cAMP binds to open Ca2+ and Na+ channels.

Opening of Cl- channels.

Depolarisation.

Question 32

How do we smell?

Answer 32

Odourants enters nasal cavity and diffuse through olfactory nerves to the olfactory bulb.

Signals are sent to pyriform cortex in temporal lobe.

Question 33

What organs other than the tongue aid with taste?

Answer 33

Pharynx, palate and epiglottis.

Question 34

3 types of papillae (for tastebuds)

Answer 34

Circumvallate papillae: Largest, posterior.

Foliate papillae: Elongated, posterior lateral edge.

Fungiform papillae: Smallest, widespread across anterior and tip of tongue.

Question 35

Sensory transduction for taste

Answer 35

Dissolved molecules interact with receptors.

Triggers membrane depolarisation.

Accompanied by intracellular Ca2+ initiates NT release.

Excite afferent nerve.

Question 36

Sensory neurone pathways (gustation)

Answer 36

1st order: Medulla
2nd order: Thalamus
3rd order: Gustatory cortex