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Lecture 7

NROC64H3 Lecture Notes - Lecture 7: Excitatory Synapse, Brainstem, Cytosol

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Matthias Niemeier

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NROC64H3S Sensory and Motor Systems
Lecture 7 -03.02.12
Short Answer: Explain the McGurk Effect
Fah bad dah thing.
- Motor Programs
Motor system: Muscles and neurons that
control muscles
Role: Generation of coordinated movements
Parts of motor control
1. Spinal cord coordinated movements
2. Brain motor programs in SC
The Somatic Motor System
- Types of Muscles:
1. Smooth: Digestive tract, arteries, related
2. Striated Cardiac/heart and skeletal/bulk of
body muscle mass
- Somatic Musculature (skeletal)
1. Axial trunk movement
2. Proximal shoulder, elbow, pelvis, knee movement
3. Distal: Hands, feet, digits movement
Think axial-close, proximal, next close, distal-FAR
The Lower Motor Neuron
= lower motor neuron: Innervated by ventral horn of SC
- Upper motor neuron: Supplies input to SC
- 30 segments
- Ventral Horn:
Cervical and lumbar are swollen
Medial lateral: axial distal
Dorsal ventral: flexors extensors (THINK OF EXAMPLE ON RIGHT)
- Alpha Motor Neurons
2 lower motor neurons ALPHA and GAMMA
Motor unit = alpha neuron + muscle fiber(s)
Motor neuron pool: populations of lower motor neurons innervating 1 muscle
- The Somatic System
Graded Control of Muscle
Contraction by Alpha Motor
1. Varying firing of motor neurons: More Ach release, temporal
2. Recruit additional synergistic motor units
3. Small and large motor neurons (more muscle fibers)
Types OF Motor Units
1. Red muscle fibers: Lots of mito and enzymes,slow to contract, can
sustain contraction
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2. White muscle fibers: Little mito, anaerobic metabolism, contract and fatigue rapidly
3. Fast m. units: fast, white fibers
4. Slow motor units: slow, red fibers
Neurocmuscular Matchmaking
Experiment: John Eccles - Are muscles properties due to innervating
nerve characteristics?
Alternate nerve input switch in muscle phenotype./physical
Hypertrophy: Exaggerated growth of muscle fibers
Atrophy: Degeneration go muscle fibers
ALS: Loss of large a-neurons, loss of superoxide dismutase increase in
superoxdice radical?. Exicitotoxicity: elevated levels of Glu
Duchenne muscular dystrophy: ONLY MALES, X-x-some, defective muscle
Myastentia gravis: Autoimmune; antibodies against nicotinic Ach
tetrad 4 Ca channels
Excitation-contraction Coupling
- Muscle contraction
A-motor neurons release Ach innervate
muscle fibers
Ach large EPSP in muscle fibers (via nicotinic
Ach receptors
AP = excitation = trigger Ca release = fiber
Relaxation: Ca levels lowered by organelle
- Molecular Basis of Muscle Contraction
Z lines: Division of myofibril into segments
Sarcomere: 2 Z liens + myofibril
Thin filaments: Series of bristles, have actin, have
Thick filaments: B/W and among thing filaments. Have myosin
Sliding filament module:
Ca binds to troponin myosin binds to actin,
Myosin head pivots, causing filaments to slide
Steps in Excitation-Contraction Coupling
1. Excitation: AP Ach RELEASE EPSP AP in muscle fiber DEPOLARIZATION
2.Contraction: Ca binds to troponin myosin bids to actin myosin pivots and
disengages cycle continues as longs as there is CA2+ and ATP
3. Relaxation: EPSPS End
resting production Ca
sequestered by SR (ATP
driven pump) myosin
binding actin covered
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