Lecture 7: Neuromuscular Aspects of Movement II Flashcards
CNS
Brain
Spinal cord
PNS
Nerve branch pairs
- 12 cranial
- 31 spinal
Plexuses
- cervical, brachial, lumbar, sacral
Afferent nerves
aka sensory nerves
carry information TO the CNS (Arrive)
Efferent nerves
aka motor nerves
carry information FROM the CNS (Exit)
Myotomes
Area of MUSCLE CONTROLLED by a specific nerve pair
Differ slightly btwn ppl
MOTOR NERVES leave the brain and spinal column in pairs
Dermotomes
Area of body FELT by a specific nerve pair
SENSORY NERVES enter the brain and spinal column in pairs
Motor cortex
Part of brain that DECIDES on which muscles to activate
Where commands come from when you want to MOVE
Somatosensory cortex
Where FEELINGS from body parts (SENSORY) arrive for processing
Motor Homunculus
Homonculus means “little man”
Shows parts of body controlled by motor cortex
Larger area = greater and finer control
HAND AND MOUTH (speech) dominate
Motor unit
All muscle fibres activated by one motor nerve
For fine control, muscles have less motor units
Powerful muscles have many motor units
EMG
Electromyography
The signal in the motor nerve is an AP
When the AP reaches the muscle, it is amplified and travels along the muscle from the NMJ
Types of EMG
Surface EMG w/ skin mounted electrodes
- differential w/ 2 contacts
Fine wire EMG w/ wire electrodes inserted via a needle
Surface EMG
Summation of 1000s of APs in muscle fibres
- multiple muscles can be tracked simultaneously to record sequencing of muscle activation
EMG: hissing sound (flexing against resistance)
Walking EMG: steam engine sound
- downside is having shaved patches
Fine wire EMG
From APs of only 1 or 2 muscle fibres so it looks very different
- downside: Pt wire can break in body
Basic muscle tone
amount of tension in muscles
muscles always contract slightly and make noise
Muscle fibre types
- Type I
- Type IIa
- Type IIb
Type I fibres
slow twitch, oxidative fibres
slow to contract but very fatigue resistant
Ex. soleus
Type IIa fibres
fast twitch, oxidative fibres (lactic acid)
fast to contract but fatigue resistant
Ex. last 30m of 100m sprint
Type IIb fibres
fast twitch, glycolytic fibres (use stored up glycogen in muscle)
fast to contract, fast to fatigue when glycogen runs out (builds lactic acid = pain)
Ex. sprints until about 70m of 100m
Elastic storage of energy
When muscle-tendon structure is stretched, elastic energy is stored in tissue
- energy is released when the muscle shortens again (used to produce extra force)
Stretch-shorten cycle
Use elastic storage
Ex. To jump straight high, you bend down first and stretch tendons which stores elastic energy
Ex. loading up structures when pitching
Ascending limb of length-tension curve
Sarcomeres are too short = active insufficiency
Descending limb of length-tension curve
Sarcomeres are too long = passive insufficiency
- helped by elastic tissue
Elasticity and length-tension
Elastic component stretches out longer than contractile component
- more force when muscle goes into passive insufficiency
Less of a drop off in passive insufficiency during stretch-shortening cycle
