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Year 2 term 3 control > Sensory and motor innervation of muscle > Flashcards

Sensory and motor innervation of muscle Flashcards

1
Q

What is the route of descending motor fibers to the skeletal muscles?

A

Upper motor neurones which consist of the motor cortex and brain stem. With input from basal ganglia and cerebelumm.
It can either have direct contact with the lower motor neurone or via the local circuitary neurone (reflex coodination) to the LMN and then to the skeletal muscle

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2
Q

What is the motor function of the brain stem?

A

Basic movement and posture control

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3
Q

What is the function of the motor cortex?

A

Planning, initating and direct control of voluntary muscles

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4
Q

What is the function of the brain and spinal cord in the motor system?

A

Brain: initiates, integration and cordination

Spinal cord: Simple reflexes and pattern generation

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5
Q

What brodmas areas is the motor cortex?

A

4 and 6

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6
Q

Where is the primary motor cortex found?

A

In the pre central gyrus –> frontal lobe

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7
Q

What is the role of the pyramidal cells? Where is there cell bodies found?

A

There cell bodies are found in the 5th cortical layer.
Two types
Betz cells that are invovled in the indirect pathway to teh LMN via the local circuit neurones (reflex coordination)
Non betz cells which are a small proportion and are involved in the direct pathway

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8
Q

How many cortical layers are there?

A

6

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9
Q

What is the route of corticalspinal tracts?

A

Descend down the midbrain, pons and medulla
Where 95% roughly decessate the midline at the clossed medulla to run down the posterior/latearl corticalspinal tract on the contralateral side
The other 5%ish descend down the anterior/ventral cortical spinal tract on the ipsilateral side.
Terminate directly or indirectly ( via interneurones) in the ventral grey horn on the contralateral side to synapse with the LMN.

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10
Q

What part of the Cerebral hemisphere looks at facial expression?

A

angular gyrus

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11
Q

Where is the LMN found in the ventral grey horn?

A

They are localised in laminar 9 of the ventral horn

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12
Q

How do the efferent axons exit the spinal cord and what nucleus generates the force by the muscle?

A

The efferent axons exit the spinal cord via ventral roots and then spinal nerves (mixed).

The alpha neurone are directly responsible of for the generation of force by the muscles

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13
Q

What are muscles made up of and how are they innervated?

A

Muscles are compromised of many fibers with are enclosed within a connective sheath.
Within any muscle each fiber is innervated by a single axon

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14
Q

Describe the distribution of lamina 9 and its size throughout the cord?

A

The size of lamina 9 varies from rostral to caudal of the cord.
The varation in size of lamina 9 reflects the demands of peripheral musculature and innervation

The lamina 9 is largest at the cervical and lumbar region due to innervation of the upper and lower limb musculature.

Ther are about 150000 alpha neurones on either side of the spinal cord

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15
Q

What is the relationship between each muscle and alpha motor neurones?

A

Each muscle is innervated by a group of alpha motor neurones called motor neurone pool.

The motor neuron pool extends rostrally-caudally along the axis of the spinal cord

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16
Q

What is the motor neuron pool distribution of medial gastrocnemius and soleus?

A

Medial gastrocnemius: L5-S2

Soleus: L4-L7

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17
Q

What is the prinicipal of segmental organization of the spinal cord?

A

Motor neurones controlling flexor muscles (bicep brachii) lie dorsal while those controlling extensor muscle (tricep brachi) lie ventral.
Motor neurones controlling axial muscles lie medial while those controlling distal muscles lie lateral

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18
Q

What is a motor unit?

A

It is a alpha motor neurone and all of the muscle fibers innervated by it . The smallest unit needed to produce a movement.

Motor neurones can innervate more than 1 muscle fiber but each muscle fiber is innervated by one axon as divergence of motor neurone occurs.

The distrubution of motor neurone is spread evenly to get a even contractility and therefore damage to motor neurone won’t impige movemnet.

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19
Q

What are the different size motor units and how many muscle fibers can one alpha motor neurone innervate?

A

Small motor unit–> e.g. extraocular muscles. Around 3 motor fibres per 1 alpha motor neurone

Medium motor unit –> e.g. soleus. Around 180 muscle fibres per 1 alpha motor neurone

Large motor unit –> gastrocnemius. Around 1000-2000 muscle fibres per 1 alpha motor unit.

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20
Q

What are the size of the motor neurones of small and large motor units and which is recruited first?

A

Small motor units compromise of small motor neurones and innervate small number of muscle fibres

Large motor units compromise of large motor neurones and innervate large number of muscl fibres

Small motor units are recruited first before large producing increase force

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21
Q

What are slow motor units and give a example?

A

Compromise of small motor units and small red motor fibers that produce a low force but are resistant to fatigue. Example is posture muscles

They have good blood supply, high HB, high levels of mitchondria

22
Q

What are fast fatiguable motor units and give examples?

A

Large motor units and large paler muscle fibres that produce large force but become fatigued quickly. Such as bicep brachii

Have low blood supply, anerobic respiration and use up ATP quickly

23
Q

What are Fast fatigue resistant motor units?

A

Intermediate, moderate force and some fatigue

24
Q

How do you record electrical motor activity of specific muscle?

A

Using electromyography
Fine guage needle into a specific muscle to pick up there electrical motor activity

The activity of the muscles reflex the synchronous recruitment of fibers within muscles

25
Q

What is the consequence of innervation of muscle at low frequenzy (5hz)

A

Muscle twitch –> contraction followed by relaxation

26
Q

What is the consequence of innervation of muscle fibres at 10hz?

A

Summation of the twitch

27
Q

What is the consequence of innervation of muscle fibres at 20hz?

A

Leads to smooth muscle contraction

28
Q

What is the consequence of innervation of muscle fibres at 40hz?

A

Summation of the twitches to cause tension which is not natural

29
Q

What are the 3 types of input to the alpha motor neurones?

A

Sensory input from the peripheral proprioceptors

Local input from spinal interneurones

Descending input from brain upper motor neurones

30
Q

What are muscle spindles and where are they found?

A

They are sensory apparatus of the muscle

Lie parallel to the muscle fibers

31
Q

What type of fibres are muscle spindles and alpha muscle fibres?

A

Muscle spindles are intrafusal muscle fibres –> detect the rate of length change of muscles

Alpha muscle fibres are extrafusal muscle fibres –>generate tension by contracting and allow skeletal movement

32
Q

What is the function of muscle spindles?

A

To detect muscle length change.

They enable regulation of muscle contraction and precise matching of force generation and motor task

33
Q

How do muscle spindles contribute to proprioception?

A

They detect position and movement of body in space

34
Q

What is the relationship between alpha motor neurones and muscle spindles?

A

The interaction between alpha motor neurones and muscle spindles ensures that muscles are always under a degree of stretch. This is muscle tone

35
Q

What are the two types of muscle spindles?

A

Bag and chain

36
Q

What is the chain spindles made up of and what is there function?

A

Made up of 1a and 2 afferent spindles which encode the static response to fibers. I.e they continue firing as long as the muscle is stretched

37
Q

What is the bag spindles made up of and what is there function?

A

Made up of only 1a afferent fibers which encode the dynamic response of fibres. I.e rate of change during rapid stretch

38
Q

What is the function of extrafusal fibres? Where do they recieve there innervation?

A

The extrafusal fibres form the bulk of the muscles and generate muscle tension.

Recieve motor innervation from the alpha motor neuroens

39
Q

What is the function of intarafusal fibres? Where do they recieve there innervation?

A

Intrafusal fibres (spindles) have a sensory function and do not generate muscle tension.

They recieve there motor innervation from gamma motor neuroens

40
Q

What is the function of the gamma MN?

A

Regulating the length of the motor spindle

41
Q

What is the relatinship between alpha and gamma MN?

A

Activation of the Alpha mn causes the contractin and shortening of the muscle fibres

Shortening of the extrafusal fibres causes the collapge of the intrafusal fibres loosing sensitivity

This is correct by Gamma mn which matches the length of the interfusal fibres vs extrafusal fibres

42
Q

What is golgi tendon organ, where is it found and what fibres is it made up of?

A

Mechanoreceptor in series with muscle fibres.

It is made up of 1b afferent fibres

43
Q

What is the function of golgi tendon organ?

A

It detects the change of muscle tension. As the muscle contract the force acts directly onto the tendon.
Monitor of muscle tension and force of contraction

Also involved of proprioception –> detection of the position and movement of body in space

44
Q

What is the difference in muscle spindle and golgi tendon organ?

A

Muscle spindle detects change in length whiel golgi tendon detects change in tension

45
Q

When is the golgi tendon organ activated but not the muscle spindle?

A

When there is isometric contraction ( change in muscle tension but not in length of the muscle) the 1b (golgi) but not the 1a afferent (spindle) is activated

46
Q

When is the muscle spindle but not the golgi tendon organ activated?

A

When there is isotonic contraction ( change in muscle length but not tension) 1a (spindle) is activated but 1b( golgi tendon) is not

47
Q

What is the relative conduction velocity of 1a,1b,2?

A

1a>1b>2

Conduction velocity is positively associated with axon diameter

48
Q

What are large diameter, fast conduction afferent fibres (1/2) associated with?

A

Low threshold mechanoreceptor

49
Q

What are small diameter, slow conducting afferent fibres (3/4) assoicated with?

A

Nociceptors and thermoreceptors

50
Q

When there is damage to the descending motor pathways it causes upper motor neurone syndrome. After several days what symptoms are there?

A

The Babinski sign–> seen in babies but should be lost
Spacicity
Hyporeflexia
Loss of fine movement

51
Q

What occurs in motor neurone disease? What is the pathalogy

A

Initially muscle weakness and atrophy
Loose function of all voluntary muscles
Does not cause cognitive impairment

Pathalogy is the degeneration of alpha motor nucleus

Year 2 term 3 control (2 decks)

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