Flashcards in General Sensory Mechanisms-4 Deck (22):
Merkels's discs are best characterized as what type of receptor?
- mechanoreceptors with expanded tip endings (free endings)
The Meissner's and Kraus' corpuscle are best described as what type of mechanoreceptors?
- encapsulated endings. Still receives skin tactile senses
What are the free and encapsulated endings that are located within deep tissue, mechanoreceptors?
- Ruffini's corpuscle are free expanded tip
- pacinian corpuscles are encapsulated
What roles can mechanoreceptors play in sensations?
- arterial pressure
Nocireceptors respond to what type of stimulus?
- free nerve ending that respond to pain
What is unique to the receptors in general?
- specific sensitivity: high sensitivity to one stimulus and nonresponsive to others.
- modality (refer to principal type of sensation)
-labeled line principle: specificity of nerve fiber for transmitting only one modality of sensation
What is the adaptation of receptors refer to?
- adaptation of receptors to a constant stimulus after a period of time.
What is a tonic receptors and how does it work?
- slow adapting receptor
- relay continuous stimulus strength
- transmit impulse while stimulus is present
What is a phasic receptor and how does it operate?
- rapid adaptation
- no continuous signal transmitted
- only stimulated when the strength of the stimulus changes
How many type A nerve fiber types are there?
- these are large to medium sized myelinated fibers
What are type C nerve fibers?
-more than half the sensory fibers in the peripheral nerves and postganglionic autonomic fibers
What are type A alpha fibers? (Group 1a)
-fibers from annulospiral ending of muscle spindle
The type A alpha (Group 1b) fibers are where?
- fibers that are from golgi tendons
What are type Abeta, gamma fibers (Group II)?
Conduct from cutaneous tactile receptors and flower-spray
What information do type Agamma fibers (Group III) generally conduct?
-temperature, crude touch, and pricking pain.
What sensations do group IV (Type C) fibers carry?
- pain, itch, temperature, and crude touch.
What is the best way to describe spatial summation?
-increase the signal strength being transmitted by progressively increasing the number of fibers.
What is a common type of sensation that uses spatial summation and how does it work?
- pain fibers
- Large number of endings in the center of field, and dissipates as we move away from the center. Generates overlap of one pain fiber over others.
How does temporal summation work?
- relies on the increasing frequency of a nerve impulse to increase the signals strength
Where is the stimulatory field of a neuronal pool located?
- located in the area within the pool that is stimulated by each incoming nerve fiber.
What is the difference of discharge and facilitated zones within a neuronal pool?
- the discharge zone is the area of neuron firing.
- the facilitated zone receives stimulus, but not strong enough to generate action potential, these zones can be either excitatory or inhibitory