Lec 13 Flashcards
Stimulus detected by
Receptor
Sensory cells
Neurons or anything
Signal is sent via ——— to cns
Neurons
Having Action Potential
How many neurons between receptor to cerebral cortex
3 neurons typically
If signal reaches cerebral cortex
Stimulus enters our consciousness
If signal does not reach cerebral cortex
Response is elicited without our conscious
Special senses
Special regions in brain
Somatic senses
Touch
Temperature
Pain
Itch
Proprioception
Somatic senses
Incoming/afferent
Somatic senses region in brain
Primary sensory cortex
Proprioception
Awareness of body movements and position in space
Subconscious processing example
Blood pressure
GI tract
Internal Temperature/PH/Osmolarity
Sensory receptors are
Transducer
Sensory cell specifically
Convert stimulus into an intracellular response
May or may not be neurons
4 main types of sensory neurons
Chemoreceptor
Mechanoreceptors
Thermoreceptors
Photoreceptors
Chemoreceptor example
PH, Na, Oxygen, Glucose
Mechanireceptor
Pressure, vibration, acceleration
Thermoreceptor example
Hot
Cold
Photoreceptor example
Light
Adequate stimulus
Form of energy to which sensory neuron is most responsive
-receptor may respond less strongly to other forms of stimulus
Stimulus
Change in membrane potential of receptor cell
*RECEPTOR POTENTIAL
(Graded potential in sensory cell)
Receptor potential can be
Depolarization (skin is touch)
Or
Hyperpolarization (light on retina)
Threshold stimulus
Minimum stimulus needed to generate enough receptor potential to produce intracellular response
Intracellular response can be
AP firing (if receptor is neuron)
Or neurotransmitter release (if non-neuron) often release neurotransmitters for partner neuron, then neuron fire AP
Sensory cells kind
1- neurons — sensory neurons
2- non-neurons — specialized sensory cell
Transduction means
Extracellular to intracellular
Primary sensory nerve endings
- free nerve endings
pain and temperature receptor
Unmyelinated axon
Slower rate
-enclosed nerve endings
pressure
Layers of connective tissue
Myelinated axon
Faster rate
Primary sensory Synapse in ———
Spinal cord
Grey matter
Dorsal region
Sensory receptors that are not neurons
Hair cell in inner ear
Machanoreceptor which has synapse with neuron
Most special senses receptors are cells that ———
Release neurotransmitters onto sensory neurons
EXCEPT SMELL/olfactory
Stimulus properties
Modality—what kinds
Location—where
Intensity—how strong(population and frequency)
Duration—how long
Modality determined by
-sensory receptor that is activated
-area of the brain which sensory signal is sent
Labeled Line Coding
Brain associate signal from particular receptors with specific modality
*photoreceptors are perceived as light even if activated by mechanical stress
All sensory stimulus move through ——— instead ———
Thalamus
Olfactory
Sensory neurons receptive field
Convergence—large receptive field
Small receptive field
Convergence receptive field
Primary sensory neurons overlap to form one large secondary receptive field
Convergence primary fields allows simultaneous sub threshold stimuli to sum at secondary sensory neuron
Two stimuli within same secondary receptive field are perceived as one single point
*NO TWO POINT DISCRIMINATION
Small receptive field
Fewer neuron convergence, smaller secondary receptive fields
Two stimuli active separately, point perceived as distinct stimuli
*TWO-POINT DISCRIMINATION
Perception thresholds
Minimum stimulus intensity for activation higher neurons in sensory pathway
Somatosensory cortex is proportional to
Sensitivity of that part
More sensitive has higher chance of
Two point discrimination
Lateral inhibition
Enhance contrast between activated receptive field and inactive neighbor
Makes stimulus easier to perceive
Stimulus intensity
Proportional to number of receptors activated
Frequency of AP
Duration
Coded by duration of AP
Some receptors can adapt
Receptors adaptation
Tonic receptors:
—adapt slowly - fire for long duration
Phasic receptors:
—adapt rapidly - fore when stimulus changes
Phasic receptors example
Olfactory neuron
Somatic senses
Cutaneous: (free endings)
1-touch—mechanoreceptor
2-pain/itch—nociceptor
3-temperature—thermoreceptor
Proprioceptive:
Where you are and organs position
Sense and respond rate is proportional to
Size and myelination
Fiber types from fastest to slowest
I>II>III>IV
Fiber type I example
Muscle/Proprioception
Fiber type II example
Mechanical stimuli
Fiber type III example
Cold, fast pain
Fiver type IV example
Heat, slow pain
Cutaneous sensory receptor types
Free nerve endings
Meissner corpuscle
Pacinian corpuscles
Ruffini corpuscles
Merkel corpuscles
Free nerve endings
Stimulus/location/structure/adaptation
Stimulus: temperature/noxious/hair movement
Location: around hair roots and under surface of skin
Structure: unmyelinated
Adaptation: variable
Pacinian corpuscles
Stimulus: vibration
Location: deep layers of skin
Structure: encapsulated in connective tissue
Adaptation: rapid
