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Musculoskeletal Module > Lecture 25 > Flashcards

Lecture 25 Flashcards

1
Q

What are the major symptoms of neurological diseases?

A

Movement disorders

-some will involve sensory or intellectual disorders

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2
Q

What are the 3x classes of movement?

A
  1. Voluntary-
  2. Reflexes - SOMATIC (not autonomic) Vestibular reflex, stretch reflex, Withdrawl reflex
  3. Rhythmic motor patterns(semiautomatic movements) - breathing, locomation, chewing
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3
Q

What are 3x examples of Somatic Reflexes?

A 
Vestibular reflexes(cat thrown and always lands on feet)
Stretch reflex (assess patient conditions with neurological disorders)
Withdrawal reflex (pain reflex - level of anaesthesia - whether withdrawl reflex is abolished or not)
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4
Q

What are 3x examples of rhythmic motor patterns?

A
  1. breathing - semiautomatic normally, dont need to think about it, but we can stop it with our own free will. Can voluntarily suppress breathing for a while, but after a while, breathing respiratory system in brain stem, rising CO2 and decreasing O2, will get oscillator/motor pattern of breathing going again
    -LIMITED control
  2. locomotion (walking)
    -control much better voluntarily
  3. chewing
    -control much better voluntarily
    -semiautomatic movements
    Not entirely reflex or voluntary - inbetween
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5
Q

What are the 7 major components of the Motor system?

A
  1. Cerebral cortex
  2. Thalamus
  3. Basal Ganglis (group of nuclei)
  4. Brain stem (base)
  5. Cerebellum
  6. Spinal Cord
  7. Muscles
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6
Q

What are the 2x Subcortical loops?

A
  1. Cortex –> Basal ganglia –> thalamus –> cortex
    -sets excitability of motor cortex
  2. Brainstem –> cerebellum –> Thalamus –> cortex
    subcortical loops engaged in movement.
    Forebrain: engaged in Voluntary movements
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7
Q

What 5x things does the Forebrain consist of, and what is it engaged in?

A
  1. Cerebral cortex
  2. Basal Ganglia
  3. Thalamus
  4. Brain stem
  5. Cerebellum
    engaged in VOLUNTARY movements
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8
Q

What 2x things does the Spinal cord and Brain stem consist of, and what is it engaged in?

A
  1. Spinal cord
  2. Muscles
    these 2x areas are where these movements are generated and controlled
    -not always fully controlled or controlled at all by cerebral cortex and subcortical loops
    REFLEXES and RHYTHMIC MOTOR PATTERNS
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9
Q

What are smooth muscles controlled by?

A

autonomic nervous system

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10
Q

What are muscles controlled by?

A

Motor neurons

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11
Q

Motor neurons/LMN

A 
located in spinal cord - 31 segments
Cervical
Thoracic
Lumbar
Sacral
Coccyx
Motor neurons cell bodies located
1. Anterior/Ventral horn -Grey matter of ALL spinal cord segments
2. Brain stem (Mid brain, Pons-, Medulla oblongata) - multiple nuclei that contain motor neurons that send axons to muscles
-specific nuclei of brain stem
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12
Q

What are the 2x locations of motor neurons?

A
  1. Anterior/Ventral Horn of all spinal cord segments - Grey matter of spinal cord
  2. Brain Stem (Midbrain, pons + Medulla oblongata)-specific nuclei of brain stem
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13
Q

What are the 3x components of the brain Stem?

A
  1. Midbrain
  2. Pons- connect to body via 12 Cranial nerves (connect brain stem to motor and sensory structures around the head and neck)
  3. Medulla Oblongata
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14
Q

What are the 5x classes of vertebrae/spinal levels?

A
  1. Cervical
  2. Thoracic
  3. Lumbar
  4. Sacral
  5. Coccyx
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15
Q

What are Cranial nerves?

A

12x Cranial nerves
Located in Pons
Connect brain stem to motor and sensory structures around the head and neck
9x of the cranial nerves contain axons coming from motor neurons, which project to various muscle groups
-e.g. Tongue muscles (innervated by motor neuron group from dorsal/posterior Medulla Oblongata called Hypoglosso nucleous. Tight group of cells that send axons to out tongue through hypoglossal nerve(cranial nerve 12/XII)

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16
Q

What is special about 9x of the 12 cranial nerves?

A

9x Cranial nerves contain Motor neuron axons, which project out to various muscle groups

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17
Q

What is the innervation of the tongue muscle?

A

Tongue muscles are innervated by Cranial nerve XII (12)
Hypoglosso Nucleus Motor neuron group is located in the posterior/dorsal Medulla Oblongata
is a tight groups of cells
send motor neuron axons out to tongue via Hypoglossal nerves

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18
Q

What are the 2x types of Motor neurons?

A
  1. ALPHA(a) motorneurons

2. GAMMA (y) motorneurons

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19
Q

What are the 9x names of the 9x cranial nerves with axons of motor neurons?

A
  1. III Oculomotor
  2. IV Trochlear
  3. V trigeminal
  4. VI Abducent
  5. VII Facial
  6. IX Glossopharyngeal
  7. X Vagus
  8. XI Accessory
  9. XII Hypoglossal
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20
Q

Sir John Eccles

A

characterised response and behaviour of motor neurons
noble price 1963
Prof at Otago
Intracellular recordings of motor neurons
-Glass Microelectrode, connected to amplifying equipment. Resting Membrane Potential RMP. synaptic potential. Action Potential. Mainly from Motor Neurons in spinal cord
1. -now used to electrophysiologically characterise nerves
2. -morphology of nerve cells. Dye (standard or fluorescent) to microelectrode. Diffuse into cell and fill it. Histological analysis, can identify morphology of nerve cells
Worked in Chicago and America - organisation of cerrebellum

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21
Q

What are the components of a neuron?

A 
Cell body (30-40 micron)
Axon (goes outside cell body)
Long dendrites (over 1mm)
22
Q

Alpha motor neurons

A

White and Grey matter
Ventral/Dorsal(animals) horns
Ventral horn = various groupings of motor neurons forming Motor nuceli. send axons via ventral root –> spinal nerves –> muscle fibres
-Innervate EXTRAFUSAL muscle fibres
-Extrafusal muscle fibres are the main skeletal muscle fibres type in the body of the muscle
Each AP will depolarise and have Contractiong of WHOLE muscle -controlled by alpha motor nueonrs

23
Q

What is the name of the main skeletal muscle fibre type of the muscle body?

A

Extrafusal muscle fibres

  • main muscle fibre on the muscle body
  • alpha motor neurons connects to them
24
Q

Somatic cell Motor Neurons

A

Start in brainstem/spinal cord
Long (sometimes short) axons to Skeletal muscle
ACh neurotransmitter

25
Q

Autonomic cell Motor Neurons

A

Sympathetic or Parasympathetic - both start in brainstem or spinal cord
Dont send direct axons to spinal cord: have switch/(para)Sympathetic Ganglia
-Preganglionic fibre - release Neurotransmitter - innervates Postganglionic fibres
Somatic motor neurons: Direct pathway
Autonomic (Para/Sympathetic) neurons: have a Switch (P/S ganglia) before can reach targets
So many inputs into brain. Only 3x outputs (1x Somatic/Motor neurons) and (2x Autonomic Neurons)
-can asses the functions of the brain by monitoring movement or autonomic responses (i.e. outputs)
-function of the brain is also sensory inputs (feelings, temp, pain etc) but also movement

26
Q

What is the ratio between input and output to and from the brain?

A

So Many inputs into the brain
Only 3x Outputs from the brain (1x Somatic Motor neurons + 2x Autonomic (para/symp) neurons)
Outputs of the somatic and autonomic Nervous system
-can asses the functions of the brain by monitoring movements or autonomic responses (i.e. outputs)
-there is also sensory input but also movement

What ever leaves the brain, has to leave through these 3x nerve channels

27
Q

How can you assess the function of the brain?

A

can asses the functions of the brain by

  1. Monitoring Movements or Autonomic responses (monitoring 3x types of outputs)
    - there is also sensory input but also movement
28
Q

Gamma (y) Motor Neurons

A

Also Located in Ventral Horn of Spinal Cord
smaller nerve cell
axons conducting slowly (still myelinated)
1. Innervate only Peripheral parts of Intrafusal musle fibres in muscle spindles
2. Increase the response of muscle spindles to stretch (when activated, response of muscle spindle to stretch is enhanced)
Cells group innervates small structure embedded in muscles called muscle spindles
-muscle spindle is a capsule which is embedded within Extrafusal muscle fibres.
-Multiple spindles in each muscle. Little sensors re muscle length. Extremely sensitive to tiny changes in length.
-Inside capsule= sensory fibres/cells. Sensory innervation Gamma motor neurons. Endings of axon form spiral connections.
-Fibres have contractile elements of Actin and Myosin (pinky) just in the Peripheral parts of the Intrafusal msucle fibres ONLY)
-Depolorisation of Intrfusal fibres = Not contraction of entire muscle as is only a tiny part of the whole thing. Control sensitivity of these sensory structures to changes in length
in all cells except tongue and diaphragm have Intrafusal muscle fibres

29
Q

Ventral/Anterior Horn of Spinal Cord

A

Contains both alpha and Gamma motor neurons

2x groups of cells are intermingled/next to eachother

30
Q

What is a motor unit?

A
  1. Cell body
  2. Axonal branches
  3. ALL muscles fibres that the M unit innervates

The anatomical AND functions unit of the motor system

Each (extrafusal) muscle fibres is innervated by only ONE MN at a SINGLE NMJ neuromuscular junction(end-plate)
but each MN innervates many muscle fibres- induce contraction of multiple muscle fibres, each via their own individual motor endplate

Innervation ratio:
=number of muscle fibres innervated by individual Motor Neuron (of that 2x motor unit)
=5-2000 range

31
Q

What is the functional and anatomical unit of the motor system?

A

Motor Unit

32
Q

What is the innervation ratio?

A

Innervation ratio:
The number of muscle fibres innervated by an individual Motor Neuron (of that 1x motor unit)
5-2000 muscle fibres

33
Q

What is the process of innervation?

A

1x AP in cell body
spread along axon
propagate
Induce simultaneous activation and contraction of 5-2000 muscle fibres
Production of force
-contributes to small or large increment of force/part of overall contraction strength

34
Q

What are the classification of Motor Units?

A

based on anatomical, physiological and biochemical properties

  1. S type: (slow) type 1
  2. FF type (Fast, Fatigable) or type II B
  3. Rare intermediate type: Type II A
35
Q

What are the 3x things the classification of motor units is based on?

A

Anatomical prop
Physiological prop
Biochemical prop
-3x properties to differ between

36
Q

What are the 2 (pot. 3x) classified types of Motor units?

A
  1. S type (slow) Type I
  2. FF type (Fast, fatiguable) Type II B
  3. rare INTermediate type (type II A)
37
Q

What is the rare type of Motor unit classified as and called?

A

Rare INTERMEDIATE Type II A

38
Q

What are the 6x differentiating features between the S type and FF type of Motor Units?

A
  1. Size (innervation ratio)
  2. Twitch time
  3. Power
  4. Metabolism
  5. Relative Number
  6. Fatigue
39
Q

What is the Size (innerv. ratio), Twitch time, Power and Metabolism of S type Motor Units?

A

Size (innervation ratio) = Small
Twitch time = long (over 50ms)
Power = weak - dependant on inn. ratio
Metabolism= oxidative/aerobic-rely on continuous supply of Oxygen
Relative number = many!
Fatigue = none or slow (little or none)! - repetitive activation
Endurance - more continuously occurring weaker contractions

40
Q

What is the Size (innervation ratio), Twitch time, Power and Metabolism of FF type motor units?

A

Size (innervation ratio)= large
Twitch time = short (about 20ms)
Power = powerful
Metabolism= ANaerobic/Glycolytic - less dependant on Oxygen
Relative number = few
Fatigue = Rapid-respond less and less with contraction
-Sprinters
-better suited to powerful but brief contractions

41
Q

What are S Type I Motor units best suited for?

A

Endurance

More Continuously occurring Weaker contractions

42
Q

What are FF Type II Motor units best suited for ?

A

Sprinters

Powerful but brief contractions

43
Q

What happens when we engage/recruit more muscle fibres?

A

What happens when we lift an object that is progressively creating bigger resistance to or movement?

44
Q

What is the Size principle?

A

size matters
Recruitment of motor units during muscle contraction
Motor units are not engaged/recruited in contraction
-especially if force of contraction if increasing in a random way
1. S type recruited first - active during relatively weak contractions. Active all the time. (Motor units belonging to S type continuously activated -postural muscles to maintain vertical position). Nerves fire 24/7. But dont fire/silent/complete Atonia of muscle tone during REM/Paradoxical sleep. Muscles fully relaxed (except Eye (extra-occular), Respiratory(cyrythmic motor pattern generator) + Urinary & Bowel Sphincters muscles. Don’t lose muscle tone)
-Sphincters have double control system (Smooth via Autonomic. Striated via skeletal)
2. FF type recruited only at High levels of Muscle Force

45
Q

What is the physiological consequences of the “size principle”?

A
  1. S type motor units “fire” almost always
  2. S type motor units are best suits for carrying sustained but small loads
  3. Weaker contractions can be graded with greater precision than strong contractions
    - only encounters force slightly
  4. Necessity to exercise (hard!) to prevent atrophy of FF units - FF units particularly which are only contracted during strong contractions
46
Q

What is the relationship between the properties of motor neurons MN and the muscle fibres that they innervate?

A

MN properties and their respective muscle fibres that they will innervate have matching properties
Exception: Soleus and Gastrocnemius
(soleus = fast
Gastroc = slow)

47
Q

There are different properties between 2x different type of muscles fibres. Are these properties coded genetically and determined at level of muscle? or are these properties dependant on the input from the brain via motor neurons?

A

Cross innervation experiment
Cats
Cut ends next to muscle, and crossed to insert the end into opposite muscle
-Peripheral axons can regenerate
-Motor axons can regenerate and reinnervate (under optimal conditions) their target muscle
-waited weeks. Properties of muscle
- Muscles are slaves of the nerves. Play to the tune of motor neurons. Cross connections=change properties

48
Q

What is the effect of cross innervation?

A

cross innervation changes

  1. Type of contraction
  2. Biochemistry of muscles (expression of myoglobin)
49
Q

What 2x substances released by MN motor neurons determine biochemical and psychological properties?

A

fast ACH Neurotransmitter
+ trophic factors released by MNs
(together with ACh?)

50
Q

What is the myoglobin content and response of S type alpha motor neurons?

A

High Myoglobin levels= red muscle

Response= slow responding to contractions

Musculoskeletal Module (27 decks)

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