Ch #6: Nervous System (pt. 2)

Where are proprioceptors located?

joints & muscle (NOT classified as muscle tissue)

Golgi tendon organ (GTO) & muscles spindles are considered what?

proprioceptors

What is the job of the muscle spindle?

provide the brain with info about a muscles length (feeling without sight)

Muscle spindle fibers are what class of fibers and in which direction do they run?

intrafusual (inner “layer/inside the spindle) and side to side/horizontally

Skeletal muscle fibers are what class of fibers and in which direction do they run?

extra fusual (outer “layer”) and run up and down/vertically

Afferent Nerve

Detects changes in muscle length and speed in the muscle spindle and then sends that info to Only

• only one of these per muscle spindle

Gamma motor/efferent nerves innervate what type of fibers?

intrafusal (aka muscle spindles)

Alpha motor/efferent neurons innervate what type of fibers?

extrafusal (aka skeltetal muscle fibers)

Do alpha/gamma motor/efferent neurons work together or separately?

together….during contraction especially

What are the phases of the stretch reflex?

1. muscle spindle detects stretch

2. sensory/afferent neuron inside spindle activates

3. info travels into the spinal cord/CNS

4. gamma (spindle) & alpha (sk muscle) motor neurons contract

5. muscle contraction occurs

Purpose of stretching is to….

lengthen and warm up a muscle

What are the 4 types of stretch?

static, dynamic, ballistic, PNF

Explain what’s wrong with ballistic stretching?

don’t do this because it activates the muscle spindle = muscle contracts and shortens muscle = opposite of the goal of stretching

What type of stretching activates the muscle spindle?

ballistic stretching

Where can you find GTOs?

tendons

What is the purpose of GTOs

to sense the tension placed on a tendon and respond with the reflex relaxation of the muscle

What do GTOs protect?

muscles and joints from severe injury (ie muscle being pulled off bone when lifting heavy weight)

What are the phases of the relaxation reflex?

• GTO detects tension placed on the tendon

• 1B sensory/afferent sends an action potential

• “SA” action potential signal enters the CNS via the dorsal root (SAID)

• sensory/afferent action potential synapses with an inhibitory neuron which releases an IPSP

• IPSP then inhibits the alpha motor neuron from signaling to the muscle spindle

• muscle relaxes/contraction stops

What technique allows you to adapt a GTO

progressive overload

What are the 3 reflex types?

stretch reflex, flexion reflex, cross-extensor reflex

What type of reflex is common in children? Is this voluntary or involuntary?

stretch reflex (one used at the doctor); involuntary

What reflex is activated by touching a hot stove?

flexion reflex

What type of reflex is a flexion reflex? How many neurons does it recruit?

simple reflex; 3

What do interneurons connect? What reflex relies on these?

sensory/afferent to motor/efferent; flexion reflex

Reciprocal Inhibitors

additional motor neuron that inhibits the opposing muscle

Cross-Extensor Reflex is defined as?

occurs when sensory information crosses the spinal cord and works to extend the opposite leg to support the body

What reflex is common in newborn babies?

cross-extensor reflex

Reflex vs voluntary movement can be explained as?

reflex = involuntary motor activity controlled by the spinal cord

voluntary = brain (motor cortex of cerebrum) controls this which allows for environment based adjustments to occur