Introduction to sensory systems Flashcards
What are sensory systems responsible for?
1) Collecting information regarding our external and internal environment
2) Conveying that information from the PNS into the CNS
3) Sensory information is utilized by the CNS to:
a) conscious appreciation of the specific qualities of a sensory stimulus
b) appropriate reflex response to a given stimulus
What are sensory receptors or ending of the PNS responsible for?
1) Monitor changes in one’s external and internal enviornment
2) Serve as biological transducers (change/transduce sensory stimuli into electrical signals = information)
3) Conduct information into the CNS
What are sensory neurons (primary sensory neurons) in the PNS?
1) Cell bodies of these neurons are almost always located in peripheral ganglia of spinal and cranial nerves
2) Perpheral processes innervate sensory receptors in peripheral tissue
3) Central processes project into the spinal cord or brain
What are the 5 different receptor classifications based on stimulus response?
Chemoreceptors Photoreceptors Thermoreceptors Mechanoreceptors Nociceptors
What are chemoreceptors?
Montior changes in chemical species in a tissue environment
What are photoreceptors?
Monitor changes in light (rods and cones)
What are thermoreceptors?
Monitor changes in temperature
What are mechanoreceptors?
Monitor changes in mechanical and physical stimuli
What are nociceptors?
Monitor noxious stimuli
Respond to noxious chemical stimulation, noxious thermal extremes, noxious mechanical stimuli
What are the different classes of receptors?
Encapsulated and nonenscapsulated endings
What are nonencapsulated endings?
Terminals of axons that lie next to cells or free in the extracellular space
What are the different types of nonencapsulated endings?
Free nerve endings
Merkel endings
Peritrichial nerve endings
What are free nerve endings?
Axonal terminal “free” between cells in tissue
What are merkel endings?
Branched terminals that end as expansions on merkel cells, located in basal layers of skin (mostly in glaborous skin)
What are peritrichial nerve endings?
Axonal terminal distributed along the root/shaft of hair follicles
What are the different types of encapsulated nerve endings?
Pacinian corpuscles Meissner's Corpuscles Ruffini's Endings End Bulbs Neuromuscular spindles Neurotendinous spindles
What are pacinian corpuscles?
Single axon that terminate ina capsule made up of collagen and thin flattened cells that are arranged concentrically to the terminal
What are Meissner’s corpuscles?
encapsulates terminals of several axons
What are ruffini endings?
thin delicate capsules
single axon that is highly branched
What are end bulbs?
Single axon that is highly branched
Often spherica most commonly located at musculocutaneous junctions
What are neuromuscular spindles?
Found in skeletal muscle
What are neurotendinous spindles?
AKA golgi tendon organs
Found in tendons and ligaments
What do nonencapsulated and encapsulated receptors generally monitor?
Somatosensory stimuli in cutaneous or other deeper tissues (also monitor various stimuli in visceral tissue
What receptors are found in cutaneous areas?
Free nerve endings Peritrichial endings Merkel's endings ruffini endings Meissner's Corpuscles Pacinian corpuscles
What do free nerve endings monitor in cutaneous areas?
Monitor thermal, painful (noxious) and tactile stimuli
Where are free nerve endings found in cutaneous areas?
In deep epidermis, dermis and hypodermis tissue
What do peritichial endings monitor in cutaneous areas?
Tactile stimuli
Where are peritrichial endings found in cutaneous areas?
Respond to best of movement of hair
Where are merkel’s endings found in cutaneous areas?
Deep epidermis
What do merkel’s endings monitor in cutaneous areas?
Tactile stimuli
What do ruffini endings monitor in cutaneous areas?
Pressure and stretch (tactile)
Where are Ruffini endings found in cutaneous areas?
Dermis/hypodermis
Where are Meissner’s corpuscles found in cutaneous areas?
Dermal papillae, located in glabrous skin
What do Meissner’s corpuscles monitor in cutaneous areas?
Tactile receptor
What do pacinian corpuscles monitor in cutaneous areas?
vibration
Where are Pacininan corpuscles found?
Dermis and hypodermis
What are the different nerve endings found in joints?
Free nerve endings
small pacinian corpuscles
ruffini-like endings
neurotendinous spindles
Where are the free nerve endings found in joints and what do they monitor?
In synovial membrane, joint capsule and periarticular CT and they are nocioceptors
Where are the small pacinian corpuscles found in joints and what do they monitor?
In periarticular CT around the joint capsule and they are proprioceptors
Where are the Ruffini-like endings found in joints and what do they monitor?
In joint capsular tissue and are proprioceptors
Where are the neurotendinous spindles (Golgi tendon organs) found in joints and what do they monitor?
In articular ligaments and are proprioceptors
What are the receptors found in skeletal muscle?
Free nerve endings
Neuromuscular spindles
Where are the free nerve endings found in skeletal muscles and what do they monitor?
Connective tissue around the muscle and they are nocioceptors
Where are the neuromuscular spindles found in skeletal muscles and what do they monitor?
Distrbuted mostly in muscle near its junction with tendon and most numerous in muscles that perform highly skilled maneuvers and they are proprioceptors
What are the receptors found in tendons?
Free nerve endings
Golgi tendon organs (neurotendinous spindles)
Where are the neuromuscular spindles found in tendons and what do they monitor?
Neuromuscular and proprioceptors
What are the receptors found in viscera?
Free nerve endings
Pacinian corpuscles
What do free nerve endings in tendons monitor?
Nocioceptors
What do free nerve endings in viscera monitor?
Nocioceptors
What do pacinian corpuscles in viscera monitor?
Stretch and distension
What type of nerve fibers are included in peripheral nerves?
Peripheral nerves include sensory and motor fibers that are distributed to various end organs or tissues
What are the trends from A(alpha) to B in myelinated fibers of peripheral nerves?
Thick myelin sheaths move from thick (A-alpha) to thin myelin sheaths
Also, the diameter decreases from A-alpha to B
What are the unmyelinated fibers in unmyelinated fibers?
C fibers
What receptors are type Ia fibers?
Neuromuscular spindle
What receptors are type Ib fibers?
Neurotendinous spindle and Ruffini endings
What receptors are type II fibers?
Neuromuscular spindle
Meissner’s & Pacinian Corpuscles
What receptors are type III fibers?
Pain and Temperature receptors
What receptors are type IV fibers?
Pain & temperature receptors
