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Physiology > Taste And Olfactory > Flashcards

Taste And Olfactory Flashcards

1
Q

What are the sensory components of the peripheral nervous system

A

Afferent nerve fibers thar carry information to the central nervous system

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2
Q

What is the sensory transmission pathway

A
  1. Sensory receptor (in periphery) undergoes transduction
  2. This goes to primary order neuron in the spinal cord, where it will synapse (cell body in dorsal root ganglion)
  3. Then to the second order neuron in the brain stem/spinal cord (interneurons can modify incoming signals here)
  4. Then to third order neurons in the thalamus
  5. Then to fourth order neurons in the sensory cerebral cortex
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3
Q

What senses does the thalamus see

A

All senses besides olfactory

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4
Q

What are sensory receptors formed from

A

Terminal portions of nerve fibers

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5
Q

Receptors respond to an “adequate stimulus”. What is an adequate stimulus?

A

Form of stimulus energy to which receptors are most sensitive. This has nothing to do with stimulus strength

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6
Q

How can receptors be stimulated

A

By several modalities. This is because receptors are adequate, but not absolute. However, they will transduce information based on what the receptor codes for

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7
Q

What are sensory receptors based on the kind of stimulus

A

Mechanoreceptors
Chemoreceptors
Thermoreceptors
Photoreceptors

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8
Q

What are sensory receptors based on location

A

Exteroreceptors
Interoreceptors
Propioceptors (internal mass of body; muscle, joint, tendon)

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9
Q

What are additionally classified receptors

A 
Special receptors (vision, taste, audition, olfaction, balance
Nociceptors
Superficial receptors
Deep receptors
Visceral receptors
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10
Q

What is the process for general sensory transduction

A
  1. Stimulus energy
  2. Receptor
  3. Receptor potential (or generator potential if naked nerve ending)
  4. Action potential
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11
Q

How is an impulse initiated

A
  1. Stimulus activates a receptor
  2. Local graded potential (generator or receptor) occur across the membrane
  3. (In afferent nerves) separate local potentials are summed at the first node of ranvier
  4. Membrane reaches threshold, leading to an action potential
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12
Q

What is a generator potential

A

A graded potential that occurs in naked nerve endings. There is no gap between the firing axon, and the receptor. There are voltage gated channels at the end of the afferent neuron

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13
Q

What is a receptor potential

A

A graded potential occurring when the receptor is a separate cell. This way, the stimulus uses a neurotransmitter to cross the synaptic cleft, enter chemically gated channels, and depolarize the afferent nerve fiber

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14
Q

What kind of information do sensory receptors transmit

A

Modality, location, intensity, duration

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15
Q

What is neural encoding

A

The way sensory receptors transmit location, modality, intensity, and duration to the brain

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16
Q

What is modality

A

The quality or nature of a stimulus (ex: light, sound, taste, pressure)

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17
Q

What are labeled lines

A

Pathways of sensory neurons that are dedicated to that modality. Ex: if touch pressure activates a photoreceptor, it will still present as light, not pressure

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18
Q

What is location of a sensation

A

The ability to locate the site of stimulation and discriminate between two closely spaced stimuli

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19
Q

How is location encoded

A

By receptive fields of sensory neurons. When these receptive fields are stimulated, they activate that specific neuron

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20
Q

How are complex receptive fields translated

A

When a receptive field is stimulated, they activate primary neurons. Messages from primary neurons are integrated, and multiple primary neurons can synapse on one secondary neuron

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21
Q

What is 2-point discrimination

A

The minimum distance between two detectible stimuli. Higher mean threshold= more difficult to discriminate

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22
Q

How is intensity of a stimulus encoded to the CNS

A
  1. Frequency code: as stimulus intensity increases, firing frequency (AP) of sensory neurons increases
  2. Population code: large stimuli will activate more receptors and produce larger responses than small stimuli
  3. As intensity increases, types of receptors activated will increase too.
    * all 3 can occur at the same time
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23
Q

How is duration encoded

A

By the duration of firing sensory neurons. The way nerve fibers change their firing frequencies over time

24
Q

What are the duration receptors

A

Phasic: fast adapting receptors, they only code the start and stop of a stimulus (putting clothes on)(ex: pacinian corpuscles) Tonic: slow adapting receptors. They send a continuous signal because the receptor potential remains depolarized (Merkel’s receptor)

25
Q

Negative symptoms associated with nerve dysfunction

A

Loss of nerve fiber or sensory receptor function. Ex: Numbness, loss of thermoreceptors, blindness, deafness.

26
Q

Positive symptoms associated with nerve dysfunction

A

Somatosensory receptors are activated (excitation). Pain, paresthesias, visual sparkles, tinnitus

27
Q

What is tinnitus

A

Ringing in the ears caused by hair cells being constantly activated due to them responding to low sound levels

28
Q

What does the somatosensory system process

A

Touch, position, pain, temperature

29
Q

What kind of receptors does the somatosensory system use

A

Mechanoreceptors, thermoreceptors, nociceptors

30
Q

What nerves mediate taste

A

CN 5 (trigeminal), 7 (facial), 9 (glossopharyngeal), and 10 (vagus)

31
Q

Distinguish flavor vs. Taste

A

Taste is the perception of sweet, salty, bitter, or sour whereas flavor is taste+smell+chemical irritation

32
Q

What is the most common cause of decreased taste

A

Medication side effect

33
Q

What are the tree types of papilla

A

Fungiform, foliate, circumvallate

34
Q

What dissolved substances do the five tastes respond to

A 
Sour: H+ in citric acid
Sweet: glucose
Bitter: alkaloids
Salty: NaCl
Umami: L-glutamate
35
Q

How will a salt receptor respond to a piece of candy

A

A salt receptor may be activated by glucose, but it will still be received as salt! (Labeled lines)

36
Q

What kind of receptors are on the tongue

A

Chemoreceptors (taste receptors), mechanoreceptors, thermoreceptors

37
Q

How is taste transduced

A
  1. Substance is dissolved in saliva and enters taste receptors
  2. Receptor potential becomes depolarized
  3. This opens either voltage gated Na+ channels, or voltage gated Ca2+ channels. Na channels will release ATP through channels, and Ca channels release vesicles of ATP
  4. ATP binds to afferent nerve ending (NOT A NEURON), depolarizes the afferent nerve ending, and sends an action potential
38
Q

Which two cranial nerves are most important for taste transduction

A

CN VII (facial) and CN IX (glossopharyngeal)

39
Q

What is the limbic system associated with

A

The drive for food! It provides an affective dimension to taste

40
Q

What is flavor directed by

A

Olfactory neurons

41
Q

What are olfactory neurons stimulated by

A

Volatile substances that reach the nasal cavity through the oropharynx

42
Q

What diseases may develop in individuals with disturbances in smell

A

Parkinson’s and Alzheimer’s

43
Q

What is the most common cause of smell disturbance in young adults

A

Trauma (cribriform plate is bone, olfactory nerve axon pass through here)

44
Q

What are the 7 primary olfactory modalities

A

Peppermint, camphoric, ethereal, musk, putrid, pungent, floral

45
Q

What is the lifespan of olfactory receptors

A

30-40 days

46
Q

What is the purpose of olfactory receptors

A

Detect, bind, and transduce odors

47
Q

What do mitral cells carry

A

Sensory information to different areas of the brian

48
Q

What is the process of olfactory transduction

A
  1. Odor binds to olfactory receptor cell, activating G-protein release
  2. G protein activates adenylate cyclase, which convert ATP to cyclic AMP
  3. An increase in cAMP opens cation channels, allowing Na and Ca to flow in (slight depolarization)
  4. An increase in Ca in the cell leads to the opening of Cl- channels, allowing Cl- to leave, further depolarizing the cell.
  5. Depolarization travels to the olfactory nerve axon, generating an action potential
  6. AP is carried along the axon towards the olfactory bulb
49
Q

How fast do olfactory nerves travel

A

Slow. They are among the slowest and smallest in the nervous system because they are not myelinated

50
Q

What do glomeruli receive

A

Input from one type of olfactory receptor (labeled lines)

51
Q

What is the job of glomeruli

A

To sort and fire components before relaying information to second order neurons in the mitral cell

52
Q

What does the olfactory system have direct access to

A

The hippocampus, where long term memories are formed

53
Q

What kind of nerves are olfactory receptors

A

Primary neurons of CN I

54
Q

What is an olfactory bulb

A

The apical dendrites of mitral cells (secondary neurons)

55
Q

What are the two regions of the olfactory complex

A
  1. Parahippocampal gyrus

2. Uncus

56
Q

Why is the uncus of clinical significance

A

Seizures often originate in this region, and are preceded by hallucinations of unpleasant odors (burning tar)

Physiology (3 decks)

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