Chapter 16 Flashcards
sensation
conscious or subconscious awareness of changes in the external or internal environment
perception
conscious awareness and interpretation of sensations; primarily a function of the cerebral cortex
sensory modality
each unique type of sensation i.e. touch, pain, vision or hearing
general senses
refers to both somatic and visceral senses
somatic senses
includes tactile senses (touch, pressure, vibration, itch, tickle), thermal sensations (warm and cold), pain sensations and proprioceptive sensations (perception of static and moving positions of the body)
visceral senses
provide info about conditions within internal organs (i.e. pressure, stretch, chemicals, nausea, hunger and temperature)
special senses
include the sensory modalities of smell, taste, vision, hearing and equilibrium/balance
process of sensation (4 steps)
- Stimulation of a sensory receptor
- Transduction of the stimulus (converts energy into a stimulus into a graded potential)
- Generation of nerve impulses
- Integration of sensory input
3 ways to classify sensory receptors
- microscopic structure
- location of the receptors and origin of stimuli that activate them
- type of stimulus detected
3 classifications based on microscopic structure
- free nerve endings of first order sensory neurons
- encapsulated nerve endings of first order sensory neurons
- separate cells that synapse with first order sensory neurons
free nerve endings
bare dendrites; lack any structural specializations that can be seen under a microscope; i.e. pain, temperature, tickle, itch and some touch sensations
encapsulated nerve endings
dendrites enclosed in connective tissue capsule ; a distinctive microscopic structure; i.e. somatic and visceral sensations (pressure, vibration and some touch sensations)
separate cells
synapse with sensory neurons; i.e. hair cells for hearing and equilibrium in the inner ear; gustatory receptor cells in taste buds and photoreceptors in the retina in the eye for vision
generator potential
a potential created by stimulation of dendrites of free nerve endings, encapsulated nerve endings and receptive part of olfactory receptors; if the potential is big enough to reach threshold, it triggers one or more nerve impulses in the axon of a first order sensory neuron
receptor potential
produced by sensory receptors that are separate cells; the potential triggers release of NT through exocytosis of synaptic vesicles
3 classifications based on location
Exteroceptors, Interoceptors and Proprioceptors
Exteroceptors
located at or near the external surface of the body; sensitive to stimuli originating outside the body; provide info about external environment; i.e. hearing, vision, smell, taste, touch, pressure, pain etc.
interoceptors/ visceroceptors
located in blood vessels, visceral organs, muscles and nervous system; monitor conditions of internal environment; nerve impulses produced by interoceptors are not consciously received unless strong stimuli (can be felt as pain or pressure)
proprioceptors
located in muscles, tendons, joints and the inner ear; provide info about body position, muscle length and tension and the position and movement of joints
6 classifications based on type of stimulus detected
Mechanoreceptors, thermoreceptors, nociceptors, photoreceptors, chemoreceptors and osmoreceptors
mechanoreceptors
detect mechanical stimuli; provide sensations of touch, pressure, vibration and proprioception and hearing and equilibrium; monitor stretching of blood vessels and internal organs
thermoreceptors
detect changes in temperature
nociceptors
respond to painful stimuli resulting from physical or chemical damage to tissue; free nerve endings; found in every tissue of the body except the brain
photoreceptors
detect light that strikes the retina of the eye
chemoreceptors
detect chemicals in the mouth (taste), nose (smell) and body fluids
osmoreceptors
sense osmotic pressure of body fluids
rapidly adapting receptors/ phasic receptor
adapt very quickly; specialized for signaling changes in a stimulus; i.e. receptors associated with pressure, touch, and smell
slowly adapting receptors/ tonic receptor
adapt slowly; continue to trigger nerve impulses as long as the stimulus persists; monitor stimuli associated with pain, body position and chemical composition of the blood
tactile sensations
include touch, pressure, vibration, itch and tickle
touch
result from stimulation of tactile receptors in the skin or subcutaneous layer
Meissner Corpuscles
rapidly adapting touch receptor; located in the dermal papillae of hairless skin; consists of egg shaped mass of dendrites enclosed by a capsule of connective tissue; abundant in fingertips, hands, eyelids, tip of the tongue, lips, nipples, soles, clitoris and tip of the penis
hair root plexuses
rapidly adapting touch receptors; found in hairy skin; consist of free nerve endings wrapped around hair follicles; detect movements on the skin that disturb hairs
Type I cutaneous mechanoreceptor or Merkel disc
slowly adapting touch receptor; saucer shaped, flattened free nerve endings that make contact with Merkel cells of the stratum basale; plentiful in fingertips, hands, lips and external genitalia
type II cutaneous mechanoreceptor or Ruffini corpuscle
slowly adapting touch receptor; elongated, encapsulated receptors; located deep in the dermis and in ligaments and tendons; found in hands, abundant in soles; most sensitive to stretching that occurs when digits or limbs are moved
pressure
sustained sensation felt over a larger area than touch; occurs with a deformation of deeper tissues; receptors: meissner corpuscles, merkel discs and pacinian corpuscles
lamellated or Pacinian corpuscle
rapidly adapting receptor; large oval structure composed of a multilayered connective tissue capsule that encloses a dendrite; found in dermis and subcutaneous layer, submucosal tissues that underlie mucous and serous membranes, around joints, tendons and muscles, in the periosteum, mammary glands, external genitalia, certain viscera (i.e. pancreas and urinary bladder)