1
Q
how is a stimulus detected in sensory physiology
A
- by a receptor
2
Q
how is a signal sent
A
- via neurons to/within the CNS
- at each synapse the sensory info is modulated and shaped
3
Q
what happens to a signal that reaches cerebral cortex
A
- stimulus enters our consciousness
4
Q
what happens to a signal that does not reach the cerebral cortex
A
- stimulus is processed and a response is elicited without our conscious awareness
5
Q
what is perceived stimuli (special senses)
A
- vision
- hearing
- taste
- smell
- equilibrium
6
Q
what is perceived stimuli (somatic senses)
A
- touch
- temperature
- pain
- itch
- proprioception
7
Q
what is subconscious processing (somatic stimuli)
A
- muscle length and tension
- proprioception
8
Q
what is subconscious processing (visceral stimuli)
A
- blood pressure
- blood glucose concentration
- internal body temp
- lung inflation
- pH of cerebrospinal fluid
- pH an oxygen content of blood
9
Q
what is proprioception
A
- awareness of body movement and position in space
10
Q
how are sensory receptors transducers
A
- they convert a stimulus into an intracellular response
- may or may not be neurons
11
Q
what are the 4 main types of sensory receptors and examples
A
- chemoreceptors ex. pH, Na+, oxygen, glucose
- mechanoreceptors ex. pressure, vibration, gravity, acceleration, sound waves
- thermoreceptors ex. hot/cold
- photoreceptors ex. light
12
Q
what is adequate stimulus
A
- the form of energy to which the sensory receptor is most responsive
- the receptor may respond (less strongly) to other forms of stimuli
ex. the preferred stimuli for photoreceptors is light
13
Q
what is receptor potential
A
- stimulus results in change in membrane potential of the receptor cell
- a graded potential
- can be depolarization or hyperpolarization
14
Q
examples of receptor potential
A
- when light photons fall on the retina in the eye, rods and cons hyperpolarize
- when skin is touched, touch receptors depolarize
15
Q
what is a threshold stimulus
A
- the minimum stimulus needed to generate enough of a receptor potential to produce an intracellular response
- response can be either AP firing (if the receptor is a neuron)
- or neurotransmitter release (non-neuron receptors)
16
Q
explain pain and temperature receptors and pressure receptors (sensory receptors that are neurons)
A
- transduction occurs at the receptor end of primary sensory neurons
- slow and fast response (stubbing your toe)
- you feel the pressure first before the pain
pain and temperature
- unmyelinated axon
- free nerve endings
- synapse in the spinal cord
pressure
- layers of connective tissue
- enclosed nerve ending
- myelinated axon
- synapse in the spinal cord
17
Q
explain sensory receptors that are not neurons and the exception
A
- receptor is separate from the primary sensory neuron
- ex. specialized receptor cell (hair cell found in the ear)
- myelinated axon
- most special sense receptors are cells that release neurotransmitter onto sensory neurons, initiating an action potential
- exception (olfaction)
18
Q
how are stimulus properties distinguished
A
- stimulus modality (what kind is it)
-> labeled line coding - location (where is it)
-> receptive fields, input convergence, lateral inhibition, anatomical map - intensity (how strong is it)
-> population and frequency coding - duration (how long does it last)
19
Q
what is stimulus modality determined by
A
- the sensory receptor that is activated
ex. photoreceptors in the eye -> light - the area of the brain to which the sensory signal is sent
ex. photoreceptors send signals along visual pathways to the visual center of the cerebral cortex
20
Q
what is labeled line coding
A
- brain always associates the signal from a particular group of receptors with a specific modality
-> signals from photoreceptors are always perceived as “light” even if they were activated by other stimulus such as mechanical stress (seeing stars)
21
Q
stimulus modalities and their pathways
A
- olfactory pathways from the nose project through the olfactory bulb to the olfactory cortex
- most sensory pathways project to the thalamus. the thalamus modifies and relays information to cortical centers
- equilibrium pathways project to the cerebellum
- olfactory pathway is the only one that does not pass through the thalamus
22
Q
what are large receptive fields
A
- convergence creates large receptive fields
- the receptive fields of three primary sensory neurons overlap to form one large secondary receptive field
- convergence of primary neurons allows simultaneous subthreshold stimuli to sum at the secondary sensory neuron and initiate an action potential
- two stimuli that fall within the same secondary receptive field are perceived as a single point, because only one signal goes to the brain (no two-point discrimination)
23
Q
what are small receptive fields
A
- found in more sensitive areas
- when fewer neurons converge, secondary receptive fields are much smaller
- the 2 stimuli activate separate pathways to the brain
- the 2 points are perceived as distinct stimuli and hence there is two-point discrimination
24
Q
what is perception threshold
A
- minimum stimulus intensity required for activation of higher (secondary, tertiary) neurons in the sensory pathway and thus transmission of the signal to the brain for perception
25
what is the anatomical organization of stimulus location and an example
- cerebral cortex highly organized so that specific areas correspond to specific receptive fields
- input to these regions always interpreted as being from that particular location
ex. somatosensory cortex organized such that each ascending tract from a particular body part has a specific corresponding region of cerebral cortex
- direct stimulation of a cortical area will lead to perception of a stimulus at the associated location
26
what is lateral inhibition of stimulus location
- enhances contrast between activated receptive fields and inactive neighbors which makes a stimulus easier to perceive
- primary neuron response is proportional to stimulus strength
- pathway closest to the stimulus inhibits neighbors
- inhibition of lateral neurons enhances perception of stimulus
27
what is intensity
- coded by number of receptors activated (population coding) and frequency of action potentials (frequency coding)
28
what is duration
- coded by duration of action potentials
- some receptors can adapt or cease to respond
29
tonic vs phasic receptors
- tonic receptors adapt slowly (fire for duration of stimulus
- phasic receptors adapt rapidly (fire only when a stimulus changes)
ex. itchy sweater - you stop feeling it after a certain amount of time
30
what are the steps of coding for stimulus intensity and duration
1. receptor potential strength and duration vary with the stimulus
2. receptor potential is integrated at the trigger zone
3. frequency of action potentials is proportional to stimulus intensity, duration of a series of action potentials is proportional to stimulus duration
4. neurotransmitter release variers with the pattern of action potentials arriving at the axon terminal
31
sensory neurons use action potential ________ to code stimulus, _________ and ______ _______ to code stimulus _______
- frequency
- intensity
- burst
- duration
- duration
32
what are the 3 cutaneous and 1 proprioceptive somatic senses
1. touch (mechanoreceptors) - pressure, vibration, stretch, flutter
2. pain and itch (nociceptors)
3. temperature (thermoreceptors)
4. info about body and limb position/movement
33
name the 5 cutaneous sensory receptor types
- free nerve endings
- meissner's corpuscles
- pacinian corpuscles
- ruffini corpuscles
- merkel receptors
34
what is the stimulus, location, structure, and adaptation for free nerve endings
stimulus = temperature, noxious stimulus, hair movement
location = around the hair roots and under surface of skin
structure = unmyelinated nerve endings
adaptation = variable
35
what is the stimulus, location, structure, and adaptation for meissner's corpuscles
stimulus = flutter, stroking
location = superficial layers of skin
structure = encapsulated in connective tissue
adaptation = rapid
36
what is the stimulus, location, structure, and adaptation for pacinian corpuscles
stimulus = vibration
location = deep layers of skin
structure = encapsulated in connective tissue
adaptation = rapid
37
what is the stimulus, location, structure, and adaptation for ruffini corpuscles
stimulus = stretch of skin
location = deep layers of skin
structure = enlarged nerve endings
adaptation = slow
38
what is the stimulus, location, structure, and adaptation for merkel receptors
stimulus = steady pressure, texture
location = superficial layers of skin
structure = enlarged nerve endings
adaptation = slow
39
what is the key point of somatosensory nerve fibers
- size and myelination of different sensory nerve fibers contributes to how quickly you can sense and respond to a stimulus
BPK 205
flashcards
Decks in class (32)
# Cards
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Lecture 118
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Lecture 240
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Lecture 320
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Lecture 421
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Lecture 539
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Lecture 620
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Lecture 727
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Lecture 820
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Lecture 921
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Lecture 10/1132
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Lecture 1221
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Lecture 1339
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Lecture 1424
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Lecture 1522
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Lecture 1615
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Lecture 1718
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Lecture 1811
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Lecture 1920
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Lecture 2018
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Lecture 2120
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Lecture 2221
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Lecture 2325
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Lecture 2422
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Lecture 2521
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Lecture 2616
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Lecture 2714
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Lecture 2820
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Lecture 2916
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Lecture 30+3123
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Lecture 3221
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Lecture 3325
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Lecture 3414
