Muscle Reflexes

Are skeletal muscles voluntary / involuntary

Voluntary usually

Motor Control System

1. Cerebral cortex

2. Basal ganglia

3. Thalamus

4. Brainstem

5. Cerebellum

Local control systems of motor neurons receive instructions & information from what 2 places

Higher brain centres

Sensory receptors in muscles, tendons, & joints

What do muscle spindle apparatus respond to

muscle length

Do larger or finer control muscles have more spindles

Muscles that require finer control have more spindles e.g. extraocular muscles

Effect of stretching muscles on spindles

They stretch too

What do golgi tendon organs respond to

Tension a muscle puts on a tendon

Muscle spindle apparatus contains thin muscle cells called ________

Intrafusal fibres

2 types of intrafusal fibres

Nuclear bag fibre
Nuclear chain fibre

2 types of sensory nerve cells (afferent nerves)

Primary (type Ia)
Secondary (type II)

Which sensory nerve cells are around which intrafusal fibres

Primary (type Ia) on Nuclear bag & Nuclear chain fibres
Secondary (type II) on Nuclear chain fibres

Muscle Spindle Apparatus (during a slow contraction)

Say whether each graph has alpha nerve, gamma nerve or both

What do gamma motor neurons do to muscle spindles

Gamma motor neuron function is to adjust sensitivity of the muscle spindles, so that they respond appropriately as extrafusal fibres contract and shorten. The spindle fibres remain taut

What happens to muscle spindles without gamma nerve activity. Why is this a problem

They slacken reducing available sensory information about muscle length during rapid shortening contractions

Role of Alpha-gamma coactivation

prevents loss of information about muscle length during rapid shortening contractions

During a rapid stretch type ___ endings shows an increase in firing rate, while type ____ show a modest increase.

During a rapid stretch type Ia endings shows an increase in firing
rate, while type II show a modest increase.

In the release of the stretch, type ___ cease firing, while type ___ slows

In the release of the stretch, type Ia cease firing, while type II slows

What do type Ia endings report on

both velocity and length of muscle stretch

What do type II endings report on

Length of muscle stretch

Simplest reflex

Monosynaptic Stretch Reflex

What does Monosynaptic Stretch Reflex involve

a sensory neuron synapsing on a motor neuron in the spinal cord
(One synapse = monosynaptic)

What does the Monosynaptic Stretch Reflex maintain

optimal resting length of skeletal muscles

How to stimulate Monosynaptic Stretch Reflex

Can be stimulated by striking the patellar ligament in the “knee-jerk reflex”

Steps of reflex

1. Strike patellar ligament / Muscle is stretched by load

2. Spindle is stretched activating sensory neuron

3. Sensory neuron activates alpha motor neuron

4. Alpha motor neuron stimulates extrafusal muscle fibres to contract

5. Stretch on spindle is reduced

Striking the patellar ligament stretches what

tendon & quadriceps femoris muscle

Example of when load stretches the muscle & spindles causing a reflex contraction

Reflex contraction of muscles to restore arm position when lifting a weight to prevent damage from over stretching

Purpose of muscle spindles & the stretch reflex

Protect your body from injury caused by overstretching and to maintain muscle tone

Role of Golgi Tendon Organs

Constantly monitor tension in tendons

How is tension in tendons reduced (3 steps)

Sensory neuron stimulates interneuron in spinal cord.
Interneuron inhibits motor neuron.
Tension in tendon is reduced

How many synapses are involved with Golgi Tendon Organs reflex

2 - Disynaptic reflex

A = golgi tendon organ

Golgi tendon organ reflex (4 steps)

Role of GTOs

protect the muscle and surrounding connective tissue from injury due to a sudden, unaccustomed movement or an excessive load

The process of minimizing the influence of
GTOs is referred to as ______

disinhibition

What is disinhibition used for in athletics

Practicing disinhibition is part of athletic training to push performance to the limits of tissue capacity.

Risk of practicing disinhibition

Risk of rupturing muscles or tendons or broken bones

Flexor withdrawal reflex process

What stimulates Flexor withdrawal reflex

Painful stimulation of the skin

Activates the flexor muscles and inhibits the extensor muscles of the ipsilateral

Reciprocal inhibition

During flexor withdrawal reflex in the contralateral leg motor neurons to the extensors are activated while the flexor muscle motor neurons are inhibited (called Reciprocal inhibition). This crossed-extensor reflex enables the contralateral leg to support the body’s weight as the injured foot is lifted by flexion.