Intro to senses Flashcards
What is sensory information?
Sensory information
- Continuously surrounds us
- Gives information about inside and outside environment
- Detected by receptors and sent to the brain
- Comes in multiple forms
* touch, taste, hearing, vision, smell, equilibrium
- Receptors classified in multiple ways
What are receptors?
Receptors
- Respond to stimulus
- Initiate sensory input to CNS
- Range from simple structures to complex structures, sense organs
What are stimuli ?
Stimuli
- Changes in sensory information
- Detected by receptors
- Some pleasurable
* e.g., tasty meal
- Some alert to danger
* e.g., detecting hot object
- Others with moment-to-moment information
* e.g., air temperature
What is sensation?
Sensation
- Conscious awareness of sensory information
- Only stimulus that reaches cerebral cortex
- Aware of only a fraction of stimuli
- Much input relayed to lower areas of the brain
* response initiated without awareness
* e.g., stimuli regarding blood pressure or carbon dioxide levels
For a stimulus to be consciously perceived, the sensory input must be sent to what area of the brain?
cerebral cortex
What must recptors do ?
Transduce
- Change one form of energy into a different form
- Original energy specific to type of receptor
* e.g., light energy in eye, sound energy in ear
- Energy transduced to electrical energy
* conducted along a sensory neuron
What is required to be a tranducer?
Two criteria necessary
1) maintenance of resting membrane potential across plasma membrane
2) modality gated channels within plasma membrane
- open in response to stimulus
What is a recptive field?
- Area of distribution of sensitive ends of receptor
- Inverse relationship between field size and ability to identify location
- If field small, precise location determined easily
- Broad field, only general region detected
What is a Tonic receptors?
Tonic receptors
* respond continuously to stimuli at constant rate
* e.g., balance receptors in inner ear
* sensitiVity stays same over time
What is a phasic receptor?
Phasic receptors
* detect new stimulus or change in stimulus
* sensitivity decreases over time
* e.g., tactile receptors of skin
* can undergo adaptation
- reduction in sensitivity to continuously applied stimulus
* e.g., loss of awareness of pressure while sitting in a chair
How does a receptor function as a transducer?
Transducers change one form of energy (e.g., light, sound) into electrical energy conducting along sensory neurons.
What are the classes of receptors?
- Stimulus type
- Location
- Structural complexity
Examples of recptors classified by stimulis type.
- Mechanoreceptors-respond to touch, pressure, vibration, stretch, and itch
- Thermoreceptors-sensitive to changes in temperature
- Photoreceptors-respond to light energy (e.g., retina)
- Chemoreceptors-respond to chemicals (e.g., smell, taste, changes in blood chemistry)
- Nociceptors-sensitive to pain-causing stimuli (e.g. extreme heat or cold, excessive pressure, inflammatory chemicals)
Examples of receptors classified by location?
- Exteroceptors
- Respond to stimuli arising outside the body
- Receptors in the skin for touch, pressure, pain, and temperature
- Most special sense organs - Interoceptors (visceroceptors)
- Respond to stimuli arising in internal viscera and blood vessels
- Sensitive to chemical changes, tissue stretch, and temperature changes - Proprioceptors
- Respond to stretch in skeletal muscles, tendons, joints, ligaments, and connective tissue coverings of bones and muscles
- Inform the brain of one’s movements
Examples of receptors based on Structural Complexity.
- Complex receptors (special sense organs)
- Vision, hearing, equilibrium, smell, and taste - Simple receptors for general senses:
- Tactile sensations (touch, pressure, stretch, vibration), temperature, pain, and muscle sense
- Unencapsulated (free) or encapsulated dendritic
endings
What are the three types of unencapsulated receptors and where are they located?
Free nerve endings are located in the skin and mucous membranes.
Root hair plexuses are located around hair follicles in the reticular dermis.
Tactile cells are located in the stratum basale of the epidermis.
What is reffered pain?
Referred pain
- Sensory nerve signals from certain viscera
* not perceived as originating from organ
* perceived as originating from dermatomes of skin
- Same ascending tracts within spinal cord
* house cutaneous and visceral sensory neurons
- Sensory cortex unable to differentiate actual and false stimuli
- Stimulus localized incorrectly
