What are the types of muscles ?
- striated involuntary (cardiac muscles)
- striated voluntary (skeletal muscles)
- non-striated involuntary (smooth muscles)
What are the 5 properties of skeletal muscles ?
- extensibility
- elasticity
- contractility
- excitability
- conductivity
What are the four functions of skeletal muscles ?
- generate movement
- maintain posture
- generate heat
- stabilize joints
What composes the «thick filaments»
Each thick filament consists of myosin molecules whose head protrude at opposite end of filament
What composes the «thin filaments»
A thin filament consists of 2 strands of actin subunit twisted into a helix plus two types of regulatory proteins : troponin and tropomyosin
Describe the physiology of skeletal muscles fibers
- AP arrives at neuromuscular junction
- Ach liberation and binding on sarcolemma
- ion permeability change
- depolarization
- ignition of AP in the sarcolemma
Exitation-contraction coupling phase
- AP travels along the whole sarcolemma
- AP travels along the T-tubules
- sarcoplasmic reticulum liberates Ca 2+
- Ca 2+ binds to troponin
- myosin binding sites on actin are exposed
- myosin heads bind to actin
- contraction
What is a motor unit
It is the functional unit of the neuromuscular system that allows the production of force and movement.
It is composed of the alpha motor neuron in the ventral horn of the spinal cord and the muscle fibers it innervates
What are the four types of motor units ?
- slow motor unit : for sustained muscular contraction
- large motor unit : easily fatigable
- fast fatigable motor unit : for brief exertion that requires large force
- intermediate : fast fatigable resistant motor unit : not as fast as FF but develops 2X the force of slow motor unit
What are the different muscles fibers ?
- slow twitch (type I) : slow oxidative fibers - contracts slowly but resistant to fatigue
- fast twitch (type II) : fast glycolytic fibers - generates fast powerful contractions but quickly fatigable
- intermediate : fast oxidative glycolytic fiber - will adapt to body demand
The ratio of each is genetically determined, different in everyone and different in every muscle
What is the order of recruitment of MNs ?
From the weakest to the strongest during contraction. It is the size recruitement principle or Henneman principle.
What are the 3 phases of muscle twitch
Lag/latent : excitation contraction
Contraction phase : cross bridges activity
Relaxation phase : Ca 2+ re-enter the SR
What are the 3 muscular metabolic pathways
- direct phosphorylation
- anaerobic
- aerobic
What is the difference in eccentric and concentric contraction regarding the Henneman’s principle ?
- in concentric contraction MU1 is activated before MU2
- in eccentric contraction MU2 is activated before MU1
What is muscle tone ?
Even when considered to be relaxed, skeletal muscles are slightly contracted due to spinal reflexes. There is no production of movement but it allows the stabilization of joints.
Define hypotonia
Absence of low level muscle contraction that leads to muscle tone
It causes a flaccid appearance with functional impairments and weak reflexes
Can result from damage to cerebellum or loss of innervation in skeletal muscles
Define hypertonia
Excessive muscle tone accompanied with hyperreflexia
Can result from a damage to UMN in the CNS
Classify the body receptors by the type of stimuli they detect
- mechanoreceptors
- thermoreceptors
- nociceptors
- chemoreceptors
- photoreceptors
Classify the body receptors according to their location
- exteroceptors
- anteroceptors
- proprioceptors
Classify body sensory receptor according to their complexity
- complex receptors
- simple receptors
What is a reflex ?
Reflexes are automatic responses to a stimulus, unconscious of changes inside or outside the body
Reflex are involuntary, poly synaptic or monosynaptic
What are the 4 spinal reflexes
- stretch reflex
- golgi tendon reflex
- flexor and crossed extensor reflex
- superficial reflexes
What is the information provided by muscle spindles ?
Muscle length
What is the information provided by golgi tendon organ ?
Amount of tension in the muscle
What is a muscle spindle ?
Intra fusal muscle fiber enclosed in connective tissue capsule
- type Ia fiber : center of the fiber- rate and degree of stretch - heavily myelinated : allows for fast conduction- very high sensitivity
- type II fiber : end of fiber - degree of stretch - myelinated - low dynamic sensitivity only sends signal about the actual length of the muscle
