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NEUR201 > Module 4 > Flashcards

Module 4 Flashcards

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1
Q

What is the somatosensory system

A

It provides information about the body’s internal and external states and helps maintain homeostasis

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2
Q

What are the three types of sensory receptors?

A

Exteroceptive: Detect things at skin level (e.g. contact, temp)
Proprioceptive: Detect body movement (joints and limbs)
Enteroceptive: Monitor internal organ function

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3
Q

What are the components of the somatosensory system?

A
  • Somatosensory receptors and neurons
  • Afferent axons and neurons
  • Neurons in somatosensory cortex
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4
Q

How is the somatosensory cortex organized?

A

Somatotopic (body) map, which is distorted due to receptor density

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4
Q

What is the pathway of sensory information?

A

Receptor → Sensory neuron → Spinal cord → Brain → Motor neuron → Skeletal muscle

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5
Q

Which horns of the spinal cord handle sensory and motor info?

A

Dorsal horn = Sensory input
Ventral horn = Motor output

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6
Q

What are the key characteristics encoded by sensory signals?

A
  • Modality: Receptor specificity (e.g. touch vs temp)
  • Intensity: Firing frequency and number of active axons
  • Location: Somatotopic mapping
  • Duration: AP pattern reflects stimulus start/end
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7
Q

What is the receptive field?

A

A region of skin that, when stimulated, affects a neuron’s activity. Smaller receptive fields allow finer discrimination (e.g. fingertips)

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8
Q

How does receptive field relative size relate to discrimination?

A

Smaller fields = better two-point discrimination
Larger fields = less spatial precision

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9
Q

What are the main pathways for somatosensory information to reach the brain?

A
  • Dorsal columns: Touch and proprioception
  • Spinothalamic tract: Pain and temperature
  • Spinocerebellar tract: Proprioceptive feedback to cerebellum
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10
Q

What wavelength range does visible light cover in the spectrum?

A

400-750 nm

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11
Q

Name the two main types of components in the eye

A

Optical components (focus light) and Neural components (detect/transmit visual info)

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12
Q

What structure of the eye controls pupil size?

A

Iris

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13
Q

What is the function of the cornea?

A

Initial focusing of light entering the eye

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14
Q

What role do ciliary play in vision?

A

Change the lens shape to adjust focus (ask what this is known as - accommodation)

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15
Q

Describe the path of light through the eye before phototransduction begins

A

Cornea → aqueous humor → pupil → lens → vitreous humor → retina

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16
Q

What changes occur in the lens during accommodation?

A

Lens becomes rounder for near focus (contracted ciliary muscles) and flatter for distant focus (relaxed muscles).

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17
Q

What are the three components of the near response?

A

Accommodation, Pupil constriction and eye convergence

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18
Q

What optical defect causes myopia and how is it corrected?

A

Light focusses in front of the retina, corrected with concave lens

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19
Q

What are the three retinal layers from back to front?

A

Photoreceptors, interneurons and ganglion cells

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20
Q

What happens to photoreceptors in the dark during phototransduction?

A

Retinal inactive → cGMP-gated channels open → Na+/Ca2+ influx depolarizes photoreceptor → glutamate released continuously

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21
Q

How do rods and cones differ in number and function?

A
  • Rods (~120 million) for night vision, no colour (scotopic)
  • Cones (~8 million) for daylight vision and colour (photopic)
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22
Q

Which cone types correspond to which colours?

A
  • S-cones = blue
  • M-cones = green
  • L-cones = red
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23
Q

What are ON-centre and OFF-centre ganglion cells responsible for?

A

ON-centre activated by light in center, OFF-centre activated by light in surround, both enhance contrast and edge detection.

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24
Outline the visual pathway from retina to cortex
Photoreceptors → bipolar cells → retinal ganglion cells → optic nerve → optic chiasm → LGN → primary visual cortex (V1).
25
Where are rods and cones primarily located in the retina?
Rods = peripheral retina Cones = concentrated in the fovea
26
How do cones contribute to colour perception?
Colour is perceived based on relative activation of S-, M-, and L-cones corresponding to blue, green, and red light.
27
Approximately how many colours can a human perceive?
~ 1 million
28
What is a common genetic cause of colour blindness?
Congenital deficiency affecting M and L opsins on the X chromosome
29
What percentage of males are affected by congenital red-green colour blindness?
About 8%
30
What key visual features does the primary visual cortex (V1) process?
Form, motion, depth, colour and spatial awareness
31
What is the retinal ganglion cell's receptive field?
The specific area of the retina from which it receives input
32
How does convergence affect visual acuity in the retina?
- Low convergence (fovea) → high acuity - High convergence (periphery) → low acuity
33
What are the basic properties of audible sound?
Frequency (pitch in HZ) and amplitude (loudness in dB)
34
What is the typical range of human hearing for frequency and intensity?
Freq = 20-20,000 Hz Int = 0-140 dB
35
What are the major structures of the outer, middle and inner ear?
- Outer: Pinna, auditory canal - Middle: Tympanic membrane, ossicles (malleus, incus, stapes), Eustachian tube - Inner: Cochlea
36
Describe the transmission of sound through the ear from air to chochlea
Pinna → auditory canal → tympanic membrane → ossicles → oval window → cochlea
37
How does the chochlea distiguish between high and low frequency sounds?
- High frequencies vibrate the basilar membrane near the oval window. - Low frequencies vibrate near the cochlear apex.
38
What triggers the activation of chochlear nerve axons?
Stereocilia deflection opens K⁺ channels → depolarisation → neurotransmitter release → cochlear nerve activation.
39
How are pitch, loudness and duration of sound encoded in the cochlea?
Pitch: location of hair cell activation Loudness: firing rate Duration: length of firing
40
What is the auditory pathway from the cochlea to the cortex?
Cochlea → cochlear nerve → brainstem → MGN (thalamus) → primary auditory cortex (temporal lobe)
41
What does tonotopic organisation in the auditory cortex mean?
High-frequency sounds activate the posterior region. Low-frequency sounds activate the anterior region.
42
What are the two main types of deafness and examples of causes?
Conduction: blockage, infection, damaged ossicles Sensorineural: hair cell damage, noise exposure, ototoxic drugs
43
What type of stimulus does the vestibular system detect?
Changes in head position, Linear and angular acceleration (not velocity)
44
What structures detect linear and angular acceleration in the vestibular system?
Lin = Utricle and saccule Ang = Semicircular canals
45
What are the functions of the utricle and sacculae?
Utricle = Detect linear acceleration Saccule = Detects vertical linear (e.g gravity)
46
What do the semicircular canals detect and how are they oriented?
They detect angular acceleration and are oriented in three planes: horizontal, anterior and posterior
47
How do the semicircular canals detect rotation?
Endolymph lags during head rotation → bends the cupula in the ampulla → deflects hair cell stereocilia
48
What is direction-selective firing in vestibular hair cells?
- Toward kinocilium: ↑ firing - Away from kinocilium: ↓ firing - Hair cells have a baseline firing rate
49
What are otolith organs and how do they function?
Utricle & saccule; hair cells in a gelatinous layer with otoliths that shift with gravity to stimulate hair cells during acceleration
50
What are three major functions of the vestibular function?
- Gaze stabilization (e.g., VOR) - Postural control - Spatial orientation (position, movement, acceleration)
51
What central pathways process vestibular information?
Signals from vestibular nuclei project to: - Oculomotor nuclei (eye movements) - Neck motor neurons (head stability) - Cerebellum/spinal cord (balance)
52
What are common vestibular disorders and their causes?
- Vertigo: Vestibular dysfunction → dizziness - Motion sickness: Visual-vestibular mismatch - "Bedspins": Alcohol alters cupula density - Ototoxic drugs: Hair cell damage (e.g., gentamycin)
53
Where are taste receptor cells located?
In taste buds on the tongue (papillae), palate, pharynx and epiglottis
54
Three main types of taste receptor and their roles
- Type I: Glial-like support cells - Type II: Detect sweet, umami and bitter (GPCRs) - Detect sour and salty (ion channels)
55
How often are taste cells replaced?
Every 10-14 days
56
Where are olfactory neurons located?
Olfactory epithelium in upper nasal cavity
57
What is the basic transduction pathway for olfaction (smell)
Odorant binds GPCR → activates G-protein → ↑cAMP → opens cation channels → depolarization.
58
How does the taste modality sweet transduce signals
- Receptor: T1R2 + T1R3 (Type II) - Pathway: GPCR → G-protein (gustducin) → PLC → ↑Ca²⁺ → TRPM5 → ATP release
59
What is the process involved in sour taste transduction? (include ion channel and receptor type)
Protons enter via Otop1, block K⁺ channels → depolarization → Ca²⁺ influx → neurotransmitter release (Type III)
60
What is the likely receptor for salty taste and how does it work?
ENaC allows Na⁺ influx → depolarization → Ca²⁺ influx → neurotransmitter release (Type III)
61
Through which cranial nerves do taste signals travel?
- CN VII (Facial) – anterior 2/3 of tongue - CN IX (Glossopharyngeal) – posterior 1/3 - CN X (Vagus) – pharynx, epiglottis
62
What do chemical senses help us do?
Detect nutrients, avoid toxins, guide appetite and enable mate selection
63
What type of cells are olfactory receptor neurons?
Bipolar neurons with dendrites in mucus and axons that form the olfactory nerve
64
How many types of olfactory receptors do humans have, and how does odor detection work?
- Around 1000 receptor types - Detection is combinatorial, each odorant activating multiple receptors
65
What is the first step in olfactory transduction?
An odorant binds to a GPCR on the cilia of an ORN
66
What happens after GOlf G-protein is activated in ORNs?
It activates adenylate cyclase, which increases cAMP, opening CNG ion channels → Na⁺/Ca²⁺ influx → depolarization.
67
How does Ca²⁺ amplify the depolarization in olfactory transduction?
By opening Ca²⁺-gated Cl⁻ channels, causing Cl⁻ efflux, which further depolarizes the membrane
68
How does the olfactory adaptation (desensitisation) occur?
- cAMP broken down by phosphodiesterase - Ca²⁺-calmodulin reduces channel sensitivity - Na⁺/Ca²⁺ exchangers remove Ca²⁺
69
Where do the olfactory receptors axons project first?
Olfactory bulbs, then second order neurons project to the olfactory cortex (part of limbic system)
70
What makes olfaction unique among sensory systems?
It bypasses the thalamus in the first stage of cortical processing
71
What senses contribute to flavour perception?
- Taste - Smell - Texture - Temperature - Pain/spiciness
72
What type of receptor are type 2 and what are they receptive to?
GPCR - sweet, umami and bitter
73
What type of receptor are type 3 and what are they receptive to?
Ion channel - salty and salty

NEUR201 (3 decks)

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