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2.5 Sensory systems Flashcards

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1
Q

Sensory homonculus

A

What the male body would look like if each part grew in proportion to the area of the cerebral cortex of the brain concerned with its sensory perception

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2
Q

Frontal lobe

A

Anterior half of cortex, motor functions

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3
Q

Parietal lobe

A

Posterior half of cortex, sensory functions

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4
Q

Stimulus

A

Change in the external or internal environment that causes a reaction-specifically potentials- in peripheral NS receptors

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5
Q

Examples of stimuli

A

Light, sound, touch, chemical odor, chemical taste

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6
Q

Sensation (Perception)

A

Conscious awareness, in the cerebral cortex, of stimuli received by peripheral sensory receptors

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7
Q

1st step of afferent sensory circuit

A

Stimulation and transduction (peripheral sensory receptor neuron transforms stimulus into electrical signals–> graded potentials)

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8
Q

2nd step of afferent sensory circuit

A

Generation of action potentials in the 1st order sensory neuron (may be separate cell from sensory receptor)
-Triggers at threshold stimulus level

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9
Q

AP frequency dictated by…

A

Strength of stimulus and graded potentials

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10
Q

Sensation

A

APs transmission to the thalamus, then to cerebral cortex where selective attention yields conscious perception of a stimulus

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11
Q

What is the thalamus’ role in sensation

A

Filters “noise,” decides whether or not it’s worth it to perceive incoming information

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12
Q

Types of peripheral sensory receptors

A

Exteroreceptors
Interoreceptors
Propioreceptors

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13
Q

Exteroreceptors

A

Monitor external environment; associated with skin (somatic sensory receptors) or special sense organs of the head

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14
Q

Interoreceptors

A

AKA visceral sensory receptors
Monitor internal environment
Associated with internal organs and tissues (ex: blood vessels, visceral organs)

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15
Q

3 types of interoreceptors

A

Chemoreceptors
Thermoreceptors
Stretch receptors

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16
Q

Propioceptors

A

Monitor body position and movements, muscle length / tension, joint positions
Associated with joints, tendons , muscles and vestibular organ

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17
Q

Receptors classified by modes of stimuli

A 
Chemoreceptors
Thermoreceptors
Mechanoreceptors
Photoreceptors
Baroreceptors
Nociceptors
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18
Q

Chemoreceptors

A

Detect chemicals detected in fluid-liquid or airborne

Ex: blood gases, salts, scents in the air, flavors in foods)

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19
Q

Thermoreceptors

A

Respond to changes in temperature

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20
Q

Mechanoreceptors

A

Respond to touch, external pressure, vibration and stretch (mostly skin but also gut and bladder)

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21
Q

Photoreceptors

A

Respond to photons (light)

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22
Q

Baroreceptors

A

Sense pressure by ‘reading’ deformation of a body structure

Ex: blood vessel stretch for blood pressure regulation

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23
Q

Nociceptors

A

React to painful, noxious stimuli, can be both extero and intero (but fewer intero)

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24
Q

Stimulation of a sensory receptor causes…

A

A local dendritic depolarization

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25
Transduction
Transforming physical or chemical stimulus into electrical signal
26
Generator potential
The first order neuron itself has has the graded potential and will itself fire the the action potential towards the central nervous system
27
What do generator potentials apply to?
Common, applies to all tactile (mechano) receptors in the skin and visceral organs
28
Receptor potentials
A dedicated receptor experiences a graded potential response that varies with stimulus intensity--> Stimulates action potentials in adjacent first order neuron
29
What are receptor potentials used by?
Relatively rare, used by gustatory and photoreceptors
30
Tactile (touch) receptors
Where generator potentials can start | Often "free nerve endings" (i.e. dendrites) that transduce mechanical stimuli
31
What do deep pressure receptors sense?
Vibration
32
What do slowly adapting touch receptors sense?
Rough?
33
Skin averages ~ ___ tactile receptors/ square inch
400
34
Where are afferent tactile signals processed / perceived?
Primary somatic sensory cortex
35
Small receptive fields
Surface area of skin occupied by a single receptor
36
Small receptive fields
Has many MORE neurons in the primary cortex (surface area of skin occupied by a single receptor) -appears larger on "map" ex: fingers
37
Large receptive fields
Represented by fewer neurons in the cortex, appear smaller | ex: trunk
38
Smaller receptive fields allow for what?
Very fine spatial resolution of sensations.. impacts two-point discrimination
39
If receptors are numerous and close together, leads to
Small receptor fields
40
For generator potentials in a tactile receptor, transduction leads to this type of membrane potential in the dendrite of the first order sensory neuron
Graded potential | THERE ARE NOT ACTION POTENTIALS IN DENDRITES
41
What are nociceptors stimulated by?
Thermal, mechanical or noxious (potentially damaging) stimuli
42
Chemical stimuli of nociceptors
Injuries locally release prostaglandins and other substances that stimulate nociceptors
43
Mechanical stimuli of nociceptors
Severe distention (gut, joints), skeletal muscle spasms or a "charlie horse"
44
What do the stimuli of nociceptors initiate?
Generator potentials in free nerve endings in skin and visceral organs
45
What happens after there is a generator potential in nociceptors?
AP delivered to peripheral NS nerves, ultimately to CNS tracts in DORSAL HORN and GANGLION of the spinal cord
46
The more painful the stimulus...
The faster the action potentials fire from nociceptors
47
What do nociceptors express that facilitate Ca2+ release at their presynaptic junctions?
μ-opioid receptors
48
Ca2+ release in nociceptors (presynaptic junction) is essential for...
Substance P neurotransmitter release
49
What does morphine do in pre-synaptic neuron?
It blocks the Ca2+ release in nociceptors in presynaptic junction which stops AP propogation
50
POSTsynaptic sensory neurons in the dorsal horn also express...
μ-opioid receptors
51
What do μ-opioid receptors normally do in the post-synaptic sensory neurons?
Depolarize the cell..
52
What does morphine do in the post-synaptic neuron?
Blocks the μ-opioid receptors and hyper polarizes the post-synaptic dendrite
53
What natural substance can work in a similar fashion to morphine?
``` Endogenous endorphins (enkephalins and dynorphins) ```
54
Propioreceptors provide information about...
- The position and rate of movement of body parts - The weight of held objects (golgi tendon organs) - The range of movement of a joint
55
Propioreceptors are located in
- Deep skin, joints and muscles (muscle spindles and Golgi tendon organs) - Vestibular organ (ears)
56
Where is propioreceptive info typically processed?
- First in the cerebellum (balance, coordination) | - Ultimately perceived as your body sense in the cerebral cortex
57
Propioreceptors are (tonic / phasic)
Tonic | Never fatigue
58
Nociceptors are (tonic / phasic)
Phasic | Fatigue
59
Trigenimothalamic tract
Conveys pain, tickle itch and temperature from face to contralateral cortex (neck up)
60
The Trigenimothalamic is a _____ neuron system
3
61
Trigenimothalamic tract: primary
Trigeminal (fifth) nerve from face, nose, mouth to brainstem
62
Trigenimothalamic tract: secondary
Crosses to opposite side (decussates) in brainstem, enters trigenimothalamic tract, ascends to thalamus
63
Trigenimothalamic tract: tertiary
Thalamus to somatosensory cortex
64
Spinothalamic tract
Conveys pain, tickle, itch and temperature (from body to contralateral cortex) Neck down
65
The spinothalamic tract is a ____ neuron system
3
66
Spinothalamic tract: primary (1st order)
From body periphery to posterior (dorsal) horn of spinal cord
67
Spinothalamic tract: secondary (2nd order)
Crosses to opposite side (decussates) in spinal cord, enters spinothalamic tract, ascends to thalamus
68
Spinothalamic tract: tertiary (3rd order)
Thalamus to somatosensory cortex
69
Spinocerebellar system
- Carries tonic propioreceptive information to cerebellum (unconscious) - Coordinates movement of major motor units (cerebrum) effecting major muscle groups
70
The spinocerebellar is a ____ neuron pathway
2
71
Spinocerebellar system: steps
- Primary neuron to spinal cord | - Secondary neuron to ipsilateral cerebellum
72
Does the spinocerebellar system decussate?
NO
73
: The vestibular organs in your inner ear contain numerous ___________ that communicate information about body position & balance to the ___________
Proprioceptors / cerebellum
74
Where are tactile inputs processed?
Primary somatic sensory cortex

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