Week 4 - Efferant and Afferent Tracts/Pathways Flashcards
tacile receptors
coruscple of touch (meissner corpuscle)
hair root plexuses
type 1 cutaneous mechoreceptors (tactile disc)
type 2 cutaneous (ruffini corpuscle)
lamellated (pacinian) corpuscles
itch and tickle receptors
thermoreceptors
warm/cold receptors
location: free endings in skin/mucous membranous of mouth, vagina and anus
sensation: warmth or cold
rate: 1sr rapid then slow
pain receptors
nonciceptors
location: free nerve endings in every body tissue expect brain
sensation: pain
rate: slow
propriceptors
muscle spindles
tendon origin
joint kinesthetic recpetors
corpuscle of touch (meissner corpuscles)
location: caspule surronds mass of dendrite in dermal papillae of hairless skin
sensations: onset of otuch and low- frequency vibrations
rate: rapid
hair- root plexuses
structure/location: free nerve endingwrapped around hiar follicles in skin
sensatoin: movement on skin surface that disburbs hair
rate: rapid
type 1 cutaneous mechorecpetors (tacile discs)
saucer-shaped free- nerve endings make contact with tactile epithelilums cells in epidermal
senation: continous touch and pressure
rate: slow
type 2 citaneous mechoreceptors (ruffini corpsuslce)
location/sturcture: elongated capsule surronds dendrtire deep in dermis and ligament and tendons
sensation: skin stretching and pressure
rate: slow
lamellated (pacinian corspuscles)
location/structure: oval, layered capsule surronds dendrties presnt in dermis and subcutanoues layer, submucousal tissues, joints, periosteum and some viscera
sensation: high frequency vibrations
rate: rapid
itch and tickle receptors
location/structure: free nerve endings in skin and mucous membrane
sensation: itching and tickling
rate: rapid and slow
muscle spindles
location/senestion: sensory nerve endings wrap around central area of encapsulate intrafusal muscle fibres within most skeletal muscle
sensation: muscle length
rate: slow
muscle spindles
location/senestion: sensory nerve endings wrap around central area of encapsulate intrafusal muscle fibres within most skeletal muscle
sensation: muscle length
rate: slow
tendon organs
location/structure: capsules encloses collagen fibres and sesnroy nerve endings at junction of tendon and muscle
sensation: muscle tension
rate: slow
joint kinesthetic receptors
location/structure: lamallted corsusples, type 2 cuntanoues mechorecpetor, tendon organs, and free nerve endings
sensation: joint position and movement
reate: rapid
1st order neurons
- First-order (primary) neurons are sensory neurons that conduct impulses from somatic sensory receptors into the brainstem or spinal cord. All other neurons in a somatic sensory pathway are interneurons, which are located completely within the central nervous system (CNS). From the face, nasal cavity, oral cavity, teeth, and eyes, somatic sensory impulses propagate along the cranial nerves into the brainstem. From the neck, trunk, limbs, and posterior aspect of the head, somatic sensory impulses propagate along spinal nerves into the spinal cord.
2nd order neurons
Second-order (secondary) neurons conduct impulses from the brainstem or spinal cord to the thalamus. Axons of second-order neurons decussate (cross over to the opposite side) as they course through the brainstem or spinal cord before ascending to the thalamus.
3rd order neuron
- Third-order (tertiary) neurons conduct impulses from the thalamus to the primary somatosensory area on the same side. As
the impulses reach the primary somatosensory area, perception
of the sensation occurs. Because the axons of second-order neurons decussate as they pass through the brainstem or spinal cord,
somatic sensory information on one side of the body is perceived
by the primary somatosensory area on the opposite side of the
brain.
sensory receptors
Sensory receptors are activated by changes in the internal or external environment
A. Sensory receptors are specialized to respond to changes in their environment called stimuli.
- Activation of sensory receptors by a strong enough stimulus causes the production of graded
potentials that trigger nerve impulses along afferent pathways to the CNS.
PNS
The PNS includes all neural structures outside the brain and spinal cord: sensory receptors, peripheral
nerves and their associated ganglia, and efferent motor endings.
simple receptors
general senses and may be nonencapsulated or encapsulated dendritic endings.
nonencapsulated dendetritc end
free nerve endings and detect temperature, pain, itch,
light touch, or are located at the base of hair follicles.
encapsulated dendritic endings
consist of a dendrite enclosed in a connective tissue capsule
and detect discriminatory touch, initial, continuous, and deep pressure, and stretch of muscles,
tendons, and joint capsules.
somatosensory system
the part of the sensory system serving the body wall and limbs, receives
input from exteroreceptors, proprioreceptors, and interoreceptors.
There are three main levels of neural integration in the somatosensory system
: the receptor level,
circuit level, and perceptual level.
receptor level
- Processing at the receptor level requires a stimulus to excite a receptor within its receptive field,
causing generation of graded potentials in order for sensation to occur.
a. If the receptor is part of a sensory neuron, the graded potentials produced are generator
potentials that can cause the generation of action potentials on the sensory neuron.
b. If the receptor is a separate structure from the sensory neuron, the graded potentials
produced are receptor potentials that may cause generator potentials on the sensory neuron.
c. Many receptors exhibit adaptation, in which a constant stimulus results in a gradual decrease
in receptor sensitivity.
circuit level
- Processing at the circuit level involves delivery of impulses along first-, second-, and third-order
neurons to the appropriate region of the cerebral cortex for stimulus localization and perception.