Peripheral Receptors and Autonomic Nervous System

What type of fibers are associated with intrafusal muscle fibers?

Ia and II

What fiber type is most associated with the nuclear bag?

Ia

What fiber type is most associated with nuclear chain?

II

Muscle spindle fibers

modified skeletal muscle fibers arranged parallel to typical skeletal fibers and ensheathed in a connective tissue covering in the muscle itself to detect stretch via mechanical deformation

Why is the muscle spindle striated as well?

to maintain sensitivity throughout range of motion OR co-contraction

What are the two types of intrafusal fibers?

Nuclear bag (spiral endings)

Nuclear chain (flower spray endings)

What is the non-contractile center of an intrafusal fiber?

nuclear bag

What is the contractile end of an intrafusal fiber?

nuclear chain

Are type Ia fibers phasic or tonic and what does that mean for their action?

Phasic, velocity of muscle stretch

Are type II fibers phasic or tonic and what does that mean for their action?

Tonic, detects pressure, stretch, and touch

Where are the cell bodies of origin for a muscle spindle?

dorsal root ganglion

What receives sensory information in the dorsal horn?

nucleus proposus

What are extrafusal fibers innervated by?

alpha motor neurons from the ventral horn

What are intrafusal muscle fibers innervated by?

gamma motor neurons of the ventral horn

When more channels are physically deformed, what occurs?

AP elicited

What does a reflex grade of 1+ indicate?

Present with small magnitude or seen only with reinforcement

What does a reflex grade of 3+ indicate?

reflex is enhanced, high normal

What does a reflex grade of 4+ indicate?

Non-sustained clonus, more than high normal

Clonus

repetitive vibratory movements

What does a reflex grade of 5+ indicate?

sustained clonus

What does a reflex grade of 2+ indicate?

normal

What does a reflex grade of 0 indicate?

absent reflex

If an individual has hyperreflexia, when might this be considered normal?

If its symmetrical

Fasciculus

a bundle of myelinated axons that travel together in the CNS (also called a tract, lemniscus, column, peduncle, or capsule)

Fasciculus proprius

roads connecting adjacent cord levels to send copies of the incoming sensory information to multiple levels of the spinal cord

What neurotransmitter will be released by the descending collateral onto the inhibitory interneuron during a muscle spindle reflex?

glutamate

What neurotransmitter will be released from the inhibitory interneuron onto the alpha motor neuron for the antagonist muscle during a deep tendon reflex?

GABA

Golgi Tendon (Tension) Organ (GTO)

sensory receptor which monitors tension in the muscle via tensile forces in the tendon

What type of fiber is the GTO?

Ib

What does the GTO synapse on to decrease activity or turn off the muscle?

inhibitory interneuron