Control of movement- lipski 1 and 2

Question 1

What are the three types of movement

Answer 1

Voluntary
Reflexes (somatic e.g. withdrawal reflex)
Rhythmic motor patterns (e.g. breathing)

Question 2

What part of the brain controls voluntary movements

Answer 2

The forebrain

Question 3

What parts control reflex movements and rhythmic motor patterns

Answer 3

The spinal cord and brainstem

Question 4

What are the three parts of the brainstem

Answer 4

Midbrain, pons, medulla

Question 5

Where are motor neurons located

Answer 5

Nuclei in the brainstem and in the anterior horn of the spinal cord

Question 6

How do motor neurone that have their cell bodies in the brainstem communicate with the muscles

Answer 6

The motor neurons that have their cells bodies in the brain stem connect to their muscles through cranial nerves e.g. the vagus nerve, and oculomotor nerve.

Question 7

What are the types of motoneurons

Answer 7

Alpha and gamma

Question 8

What are the main kind of fibres in our skeletal muscle

Answer 8

Extrafusal muscle. These fibres generate tension (force) by contracting.

Question 9

What kind of motoneurons innervate extrafusal muscle fibers

Answer 9

Alpha motorneurons

Question 10

What do gamma motorneurons innervate

Answer 10

Intrafusal muscle fibres

Question 11

What are intrafusal muscle fibres

Answer 11

Muscle fibres that lie within muscle spindles. There are multiple spindles within muscles and they sense changes in the length etc of the muscle.

Question 12

What is the role of gamma motoneurons

Answer 12

They innervate intrafusal muscle fibres. When the neuron is activated the muscles spindles have an increased response to stretch. Increasing contraction of muscle

Question 13

What is the motor unit

Answer 13

The anatomical and functional unit of the muscle system (neuron plus all the muscle fibres it innervates)

Question 14

How many muscle fibers can one MN innervate

Answer 14

5-2000

Question 15

What are the two classifications of motor units

Answer 15

Type 1 / S type (slow)
Type 2b/ FF type (fast, fatigable)
Type 2a is intermediate (mix of two types)

Question 16

What are the 4 most important differences in S and FF type motor units and how do S types better

Answer 16

Metabolism- S oxidative, FF glycolytic

Twitch time S- long, FF-short

Size- S- small, FF large

Power S weak, FF powerful

But there are many S types and they don’t fatigue or fatigue slowly.

Question 17

How does recruitment of the different motor units occur

Answer 17

Using the size principle. S type are recruited first- i.e. the are recruited during relatively weak contractions. FF type units are recruited only at relatively high force

Question 18

What do we need to do to prevent FF type atophy

Answer 18

Exercise!

Question 19

What are the two mechanisms that control force in muscle contraction

Answer 19

The frequency of AP, recruitment of additional motor units

Question 20

What are the main receptors which control movement

Answer 20

Muscle spindles (monitor muscle length and speed of length change)
Golgi tendon organs (monitor muscle tension)
Pain receptors in the skin
Joint receptors (monitor position and if hyperextension or flexion is occurring)

Question 21

What are the five elements of a spinal reflex

Answer 21

Receptors
Afferent (sensory) fibers
Central synaptic relay
Efferent (motor) fibers
Effectors (skeletal muscles)

Question 22

What are the fastest conducting nerve fibres in our body

Answer 22

Type 1a afferents

Question 23

Describe the pathway of the stretch reflex

Answer 23

Receptors located in the muscle spindle detect changes in length of muscle and the speed of length change, transmit via type 1a afferents whose cell body lies in the dorsal root ganglion, synapses with alpha motoneuron in the ventral horn of the spinal cord, transmits via axon of alpha motoneuron to effectors, extrafusal muscle fibres.

Question 24

Where are cell bodies of sensory (afferent) nerve cells found

Answer 24

In the dorsal root ganglion.

Question 25

Describe the second pathway or additional synaptic relay in stretch reflexes

Answer 25

1a afferent fiber transmits to an interneuron (as well as excitatory alpha mn) which inhibits other motoneurons from innervating the antagonist muscle. E.g. prevents triceps from firing if you are trying to activate a biceps reflex.

Question 26

What fibers are involved in the inverse myototic reflex and what is it

Answer 26

The golgi tendon organ reflex. Stop muscles from being overstretched. Fibres are 1b afferents which synapse with 1b interneurons who synapse with alpha motoneurons.

Question 27

What fibres are involved in reciprocal inhibition

Answer 27

1a sensory afferents have slips to 1a inhibitory interneurons which inhibit alpha motoneurons that supply the muscle that has the opposite action to the one required in the stretch reflex.

Question 28

What fibres are involved in the stretch reflex

Answer 28

1a afferents that are in muscle spindles synapse with alpha motoneurons in the ventral horn of the spinal cord the alpha motoneurons innervate extrafusal muscle fibres

Question 29

What fibres are involved in the withdrawal reflex

Answer 29

Type III and IV afferent fibers relay nociceptive stimuli to excitatory interneurons that synapse with alpha motoneurons that innervate extrafusal fibres that are in flexor muscles in the flexor or withdrawl reflex.

Question 30

Where are cell bodies of afferent nerve fibres found

Answer 30

In the dorsal root ganglion