Chapter 13 General Senses Flashcards
Special Senses
_______ are activated by changes in the internal or external environment
Sensory receptors
Survival depends upon these 2 factors:
- Sensation
- Perception
The awareness of changes in the internal and external environment
Sensation
The conscious interpretation of those stimuli
Perception
Specialized to respond to changes in the environment (stimuli)
Activation results in graded potentials that trigger nerve impulses
Sensory receptors
Classification of Receptors; 3 ways
- Type of stimulus
- Body location
- Structural complexity
Respond to touch, pressure, vibration, and stretch
Mechanoreceptors
Sensitive to changes in temperature
Thermoreceptors
Respond to light energy
Photoreceptors
Respond to chemicals
Chemoreceptors
Sensitive to pain-causing stimuli
Nociceptors
Respond to stimuli arising outside of body
Receptors in skin for touch, pressure, pain, and temperature
Most special sense organ receptors
Exteroreceptors
Also called visceroceptors
Respond to stimuli arising in internal viscera and blood vessels
Sensitive to chemical changes, tissue stretch, and temperature changes
Sometimes cause discomfort but usually person is unaware of their workings
Interoceptors
Respond to stretch in skeletal muscles, tendons, joints, ligaments, and connective tissue coverings of bones and muscles
Inform brain of one’s movement
Proprioceptors
Modified dendritic endings of sensory neurons
Found throughout body and monitor most types of “general sensory” information
Simple receptors (general senses)
Tactile sensations (touch, pressure, stretch, vibration)
Temperature
Pain
Muscle sense
One receptor can respond to multiple stimuli
General senses
Free nerve ending in general sense receptor
Present nearly everywhere in body
Abundant in epithelia and connective tissue
Mostly unmyelinated, small
3 types: Free nerve endings, tactile discs, hair follicle receptors
Nonencapsulated nerve endings
Unmyelinated fibers with knoblike swellings on their ends
Respond to temperature and painful stimuli
Free nerve endings
Free nerve endings associated with enlarged disc-shaped epidermal cells
Function as light touch receptors
Located in deeper layers of epidermis
Tactile (merkel) cells
Free nerve endings that are in and around hair follicles
Hair follicle receptors
Consist of one or more fiber terminals of sensory neurons enclosed in a connective tissue capsule
Almost all are mechanoreceptors
Vary in shape, size, and distribution
6 types
Encapsulated nerve endings
Small receptors involved in discriminative touch
Tactile corpuscles
Large receptors respond to deep pressure and vibration when first applied
Lamella (Pacinian) corpuscles
Respond to deep and continuous pressure
Bulbous corpuscles
Spindle-shaped proprioceptors that respond to muscle stretch
Muscle spindles
Proprioceptors located in tendons that detect stretch
Tendon organ
Joint capsules of synovial joints
Joint kinesthetic receptors
Part of sensory system serving body wall and limbs
Receives inputs from: exteroceptors, proprioceptors, interoceptors
Input is relayed toward head but processed along the way
Somatosensory system
Sensory receptors; First level of integration center
Receptor level
Processing in ascending pathways; Second level of integration center
Circuit level
Processing in cortical sensory areas; Third level in integration center
Perceptual level
Warns of actual or impending tissue damage so protective action can be taken
Stimuli: extreme pressure or temperature, histamine, ATP, acids
Impulses travel on fibers that release neurotransmitters glutamate and substance P
Pain
Results from stimulation of visceral organ receptors
Visceral pain
Comes from stimulation of joints, bones, muscles, and soft tissues
Somatic pain
Pain tolerance ________
Varies
Pain from one body region is perceived as coming from different region
Visceral and somatic pain fibers travel along same nerves
Brain assumes stimulus comes from common (somatic) region
Referred pain
