PERIPHERAL NERVOUS SYSTEM Flashcards
The PNS includes all neural structures outside the brain and spinal cord. These structures are
sensory receptors, afferent and efferent nerves and their associated ganglia, and motor endings.
are specialized to respond to changes in their environment, which are called stimuli.
Sensory receptors
respond to mechanical force such as touch, pressure (including blood pressure), vibration, and stretch.
Mechanoreceptors
respond to temperature changes.
Thermoreceptors
respond to potentially damaging stimuli that result in pain.
Nociceptors
respond to chemicals in solution
Chemoreceptors
such as those of the retina of the eye, respond to light.
Photoreceptors,
are sensitive to stimuli arising outside the body
Exteroceptors
also called visceroceptors, respond to stimuli within the body
Interoceptors
respond to internal stimuli. However, their location is much more restricted.
Proprioceptors
They are found throughout the body and monitor most types of general sensory information.
general senses
Receptors that are housed in complex sense organs.
special senses
general sensory receptors are nerve endings that are
either nonencapsulated (free) or encapsulated.
nonencapsulated (free) nerve endings of sensory neurons are particularly abundant
epithelia and connective tissues.
Free nerve endings respond chiefly to
painful stimuli and temperature
Nerve endings that respond to cold (10–40°C, or 50–104°F) are located in the
superficial dermis.
Those responding to heat (32–48°C, or 90–120°F) are deeper in
the dermis
A key player in detecting painful stimuli is a plasma membrane protein called the
vanilloid receptor.
Another sensation mediated by free nerve endings is Located in the dermis
itch
which lie at the junction of the epidermis and dermis, function as light pressure receptors.
Epithelial tactile complexes
free nerve endings that wrap basketlike around hair follicles, are light touch receptors that detect bending of hairs
Hair follicle receptors
which nerve endings consist of one or more fiber terminals of sensory neurons enclosed in a connective tissue capsule.
encapsulated nerve endings
what is also called as Meissner’s corpuscles and are small receptors in which a few spiraling sensory terminals are surrounded by Schwann cells and then by a thin egg-shaped connective tissue capsule.
tactile corpuscles
what is also called Pacinian corpuscles, are scattered deep in the dermis, and in subcutaneous tissue underlying the skin. Although they are mechanoreceptors stimulated by deep pressure, they respond only when the pressure is first applied, and thus are best suited to monitoring vibration (
lamellar corpuscles
what is or Ruffini endings, which lie in the dermis, subcutaneous tissue, and joint capsules, contain a spray of receptor endings enclosed by a flattened capsule. They bear a striking resemblance to tendon organ
bulbous corpuscles
what are fusiform (spindle-shaped) proprioceptors found throughout the perimysium that wraps individual fascicles of skeletal muscle.
muscle spindles
Each muscle spindle consists of a bundle of modified skeletal muscle fibers,
called intrafusal fibers
what are proprioceptors located in tendons, close to the junction between the skeletal muscle and the tendon.
tendon organs
what are proprioceptors that monitor stretch in the articular capsules that enclose synovial joints.
Joint kinesthetic receptors
the part of the sensory system serving the body wall and limbs
somatosensory system
what are Three main levels of neural integration operate in the somatosensory
STEP 1 Receptor level: sensory receptors
STEP 2 Circuit level: processing in ascending pathways
STEP 3 Perceptual level: processing in cortical sensory areas
are fast adapting, often giving bursts of impulses at the beginning and the end of the stimulus.
phasic receptors
provide a sustained response with little or no adaptation.
tonic receptors
The stimulus energy must be converted into the energy of a graded potential, a process called
transduction
what is the ability to detect that a stimulus has occurred.
Perceptual detection
what is the ability to detect how intense the stimulus is.
Magnitude estimation
what allows us to identify the site or pattern of stimulation.
spatial discrimination
what is the mechanism by which a neuron or circuit is tuned to one feature, or property, of a stimulus in preference to others.
feature abstraction