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58 Cards in this Set

  • Front
  • Back
Sensation
conscious and subconscious awareness of changes in internal or external environment (CNS)
Perception
conscious awareness & interpretation of sensation ( Cortex)
Sensory Modality
Each unique type of sensation; touch, pain, vision, hearing, etc
General senses
Somatic senses, Visceral senses
Somatic senses
from bodys walls
Visceral senses
are sensations from internal organs
Special senses
smell, taste, hearing, vision & balance
Sensory receptor
demonstrate selectivity, they respond of one type of stimuli
Events occurring within a sensation
1. Stimulation of the receptor

2. Transduction (conversion) of stimulus into a graded potential
a. Vary in amplitude and are not propagated

3. When graded potential reaches threshold action potential is generated

4. Integration of sensory input by the CNS
Free nerve endings
Bare dendrites
Pain, temp, tickle, itch & light touch
Encapsulated nerve endings
Dendrites enclosed in CT capsule
Pressure, vibration& deep touch
Separate sensory cells
• Specialized cells that respond to stimuli
• Vision, taste, hearing, balance
Generator potentials
Found in free and encapsulated nerve endings & olfactory receptors

• If large enough, its generated action potential in a 1st order neuron
Receptor potentials
- found in all special senses except olfaction
• cells release neurotransmitter molecules
Exteroceptors
• Near surface of body
• Receive external stimuli
• Hearing, vision, smell, taste, pressure, pain, vibration & temp
Interoceptors
• Monitors internal environment (BV or viscera)
• Usually not conscious except for pain or pressure
Proprioceptors
• Muscle, tendon, joint & internal ear
• Senses body position & movement
• Awareness of body position in space
Photoreceptors-
Light
 
Chemoreceptors -
Chemicals/molecules
• Taste, smell & changes in body fluid chemistry (dehydration)
Osmoreceptors
Monitor H20 Levels
Nocioceptors-
Unconsiuous. Detect tissue damage ( &thus (may) register pain)
Thermoreceptors
Temperature
Mecanoreceptors
Detect pressure, stretch, touch, vibration, proprioception, hearing, equilibrium & Blood Pressure
Adaptation of Sensory Receptors
• Decrease in sensitivity of a receptor to a long lasting stimuli

- Bad smells disappear
- Hit water starts to feel only warm
Slowly adapting receptors
• ( pain, blood chemistry.. (dehydration) , body position) continue Action Potentials as long as stimulus persists
Rapidly adapting receptors
(smell, pressure, touch)
- Adapt quickly for detecting stimulus changes
Somatic sensations
Stimulation of sensory receptors in skin, subcutaneous layer, mucous membranes, muscles, tendons, joints (& inner ear)

Most receptors - tip of tongue, fingers & lips
Touch
crude touch - ability to only perceive s/t has touched skin

fine (discriminating) touch gives location & texture
Pressure
sustained sensation over a large area
Vibration
rapidly repetitive signals
Itching
chem stimulation of free nerve endings by bradykinins (chemicals) often because of a local inflammatory response
Tickle
stimulation of free nerve endings only by someone else
Rapidly Adapting
1.) Corpuscle of touch)
2.) Hair root plexus
Slowly Adapting
3.) Type I cutaneous mechanoreceptors (fine touch)

4.) Type II cutaneous mechanoreceptors (stretching)
Corpuscle of touch
Encapsulated receptor in dermal papillae of hairless skin (hands, eyelids, tongue, genitals)

Fine (Discriminative) touch and pressure- Rapidly adapting
 
 
Hair root plexus
Rapidly touch receptors in hairy skin

Free nerve endings wrapped around hair follicles, detect hair movement
Type I cutaneous mechanoreceptor
Flattened dendrite touches Merkel cells of stratum basaleFree nerve endings for Fine Touch & Pressure, Slow Adapting
25% of receptors in fingertips, hands, lips, external genetalia.

 
Type II cutaneous mechanoreceptor
Encapsulated receptors deep in dermis ( and hands/soles), ligaments, & tendons to detect stretching in fingers/limbsSlow Adapting
Pressure Receptors
Pressure is a sustained sensation felt over wider area than touch.. Involve:
1.) Corpuscle of Touch
2.) Type I mechanorecpetors
3.) Lamellated Corpuscles
Lamellated corpuscle
Onion like encapsulated dendrite, found in dermis, subcutaneous layer, mucous & serous membrane, joints, tendons, muscles, periosteum, mammary glands, & certain viscera.. Sense pressure
Thermal sensations
Free nerve endings with 1mm diameter receptive fields on the skin surfaceCold receptors, Warm receptors
Pain Sensations. Noceiceptors
= pain receptors

• Free nerve endings- in every tissue except brain
• Tissue injury releases chemicals such as K+ kinins or prostaglandins that stimulate nociceptors

Little adaptation
Fast Pain
acute
Slow Pain
(chronic) - aching or throbbing pain
Phantom pain -- Phantom limb sensations
cells in cortex still active
Superficial somatic pain
skin
Deep somatic pain
muscle, tendons, joints and fascia
Visceral pain
organs
Referred pain- Visceral pain
felt just deep to the skin over affected organ OR far away from the organ

• Skin area & organ are served by the same Spinal Cord level
• Heart attack- is felt in skin along left arm since are both supplied by T1-T5
Pain Relief
• Aspirin and ibuprofen block formation of prostaglandins that stimulate nonciceptors

• Novocain/Lidocaine blocks Action Potentials along pain fibers

• Morphine decreased the perception of pain in the brain
Proprioceptive or Kinestetic Sense
Awareness of body position and movement.

Proprioceptors adapt only slightly

Sensory information is sent to cerebellum and cerebral cortex
Muscle spindles
a proprioceptor but also monitor muscle length and participate in stretch reflexes ( contraction)

 
Golgi Tendon organs
- A proprioceptor, but also monitor change un muscle force

• Too much force in tendon a sensory signals to CNS cause muscle’s relaxation

• Found at junction of tendon & muscle
Joint Kinesthetic receptors
• Signal joint position/movement
• Type II mechanoreceptors
- found in joint capsule
• Lamellated corpuscles
- found in CT around joint (“widely distributed”)
1st order neurons
conduct AP from somatic receptors TO spinal cord ( cell body in DRG) OR from cranial nerves to brain stem.
2nd order neurons
conduct APs from spinal cord OR brainstem to opposite side of thalamus-- decussates.
3rd order neurons
in thalamus; conduct APs from thalamus to primary somatosensory cortex.

 
Somatic sensory map of cerebral cortex
• Relative size of corical areas:
- Proportional to # of sensory receptors & thus to sensitivity of each body part

• Can be modified
- Can learn Braille & will have larger area representing fingertips