W3L1 - Motor Control Flashcards
Why is motor control important to study?
Nervous system’s ultimate function: Control behaviour (move muscles)
What are three examples demonstrating brain is essential for behaviour?
1.) Locked in Syndrome
- Awake but cognitively intact
- Caused by brainstem stroke
2.) Sea Squirt
- Larvae: Brain in head and big tail for swimming
- Adult: Eat its own brain after attaching to a rock
- Brain is useless once need to move is lost
3.) Blindsight
- Cortically blind people respond to visual stimuli they don’t consciously see
- Visual system intact but unable to consciously process, but it’s able to use information to navigate environment
What are the 3 kinds of muscle cells or fibres
Voluntary body movements
- Skeletal (Straited)
Involuntary body movements
- Smooth: Gut and Lungs
- Cardiac: Heart
How many skeletal muscles do we have? What kinds are there? What kind of movements do they make?
- Approximately 700 skeletal muscles
- Agonist/Flexor or Antagonist/Extensor
- They can only make one movement (i.e. contract, but there are 2 kinds)
What are the types of muscle contractions and what is its underlying mechanisms
Isometric contraciton: Same Length
- e.g.Carrrying table
Isotonic contraction: Same tone
- e.g. Picking up something
Sliding Filament Theory is the underlying mechanism
What is the anatomy of skeletal muscle?
Many muscle fibres in each muscle
- Each muscle fibre innervated by one motor neuron
- One motor neuron innervates many muscle fibres
- Fine motor control: Few muscle fibres per motor unit
- Gross motor control: Many muscle fibres per motor unit
What is the anatomy of the muscle fibre. Name the key parts and the functions?
T-Tubules
Folded cell membranes outside the muscle fibre
Myofibrils
Main work force that cause the muscle contraction. They contain thick filaments (myocin) and thin filamenets (actin)
Sarcoplasmic Reticulum
Modified form of endoplasmic reticulum and is full of calcium.
How does the motor neuron affect the muscle fibre? Link this to sliding filament theory.
How motor neuron affects muscle fibres
- Motor neuron from the spinal cord synapses on a muscle fibre (neuromuscular junction; NMJ), releasing acetylcholine
- Axon-to-Membrane
- Voltage-gated Na channels and sodium rushes into the cell, depolarises the membrane.
AP
- AP propagates in all directions and including going down the t-tubules
- Calcium released from the sarcoplasmic reticulum
- Myocin (Thick) and Actin (Thin) filaments in myofibrils to slide over each other, causing muscle contraction
- When AP is gone, calcium is gradually taken up by the sarcoplasmic reticulum
- Muscle relaxes and goes back to its resting position (the filaments goes back to its resting position) until another AP comes down the motor neuron.
What are 3 differences between synaptic trasmission and msulce contraction
In muscle contraction
- AP always causes muscle twitch (no threshold)
- AP propogrates in all directions
- Only Acetylcholine is released
How is force modulated in muscles?
Force is modulated by:
- Number of motor neurons activated
- Rate of firing of motor neuron
An AP ALWAYS result in muscle twitch
What are the 2 kinds of reflexes discussed?
Muscle Spindles/ Intrafusal Fibres
- Located in muscle
- Detect muscle length
Golgi Tendon Organs
- Located in tendons
- Detect muscle stretch (or rather, tension and force because of the stretch)
What is the difference between extrafusal and intrafusal muscle fibres
Extrafusal Muscle Fibres
- Voluntary movement
- Innervated by alpha motor neuron
Intrafusal Muscle Fibres
- Involuntary movement
- Innervated by gamma motor neuron
How does the intrafusal fibres/muscle spindles work?
- Signal from brain telling muscle to contract
- AP generated in alpha and gamma motor neurons
- Extrafusal fibres contract and intrafusal fibres contract a bit (not as much)
- When intrafusal fibres contract
- Afferent fibre detects small change in length and sends information back to the alpha motor neuron in spinal cord (via. monosynaptic connection)
What is the gorgi tendon reflex. What is the function and give an example.
Golgi Tendon Reflex
- Bundle of nerves located in tendons, at the ends of the muscle
- Prevent muscle damage and a polysynaptic reflex
- e.g. Increasing tension in muscle to hold more weight. Golgi tendon organ sends information to spinal cord and an inhibitory interneuron sends an inhibitory signal to alpha motor neuron so that the muscle relaxes a little
