Week 9 Lecture
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_________ surrounds each muscle fiber and and encloses its contents
Sarcolemma
________ contains the cell nuclei of muscle fiber
Sarcoplasm
two main anatomical features of myosin
Polypeptide tail Globular head
___________ activates the myosin heads during crossbridging
ATP hydrolysis
What enzyme splits ATP in the cross bridge
ATPase
Skeletal muscle fibres differ in what three characteristics ?
• the primary mechanisms they use to produce ATP • the type of motor neuron innervation • the type of myosin heavy chain expressed
What are the four common characteristics of type 1 fibers ?
• Low myosin ATPase activity • Slow calcium handling ability and shortening speed • Less developed Glycolytic capacity • Large and numerous mitochondria
What 6 main areas is the brain divided into ?
Medulla Pons Midbrain Cerebellum Diencephalon Telencephalon
What is the role of the Pyramidal tract ?
Activates skeletal musculature in voluntary movement
What is the role of the Extrapyramidal tract
Controls posture and muscle tone
What tasks may the reticular formation be involved in?
Posture during movements CV Respiration m Sleep-wake Cycle
What are the five common features of the NMJ
• Schwann cells • ACH in terminal section of neuron • Basement membrane lining synaptic space • ACH receptors • Microtubules to transmit electrical signal to fiber
What three factors produce neuronal facilitation?
• Decreased sensitivity of the motor neuron to inhibitory neurotransmitters • Reduced quantity of inhibitory neurotransmitter substance transported into motor neuron • Combined effect of both mechanisms
How are motor units classified ?
Based on the properties of the fibers they innervates. Properties: • twitch characteristics • tension characteristics • fatigability
What is Sarcopenia ?
Age-related loss of muscle mass
Sarcopenia is due to what?
Decrease in muscle size Decrease in number of fibers
Describe the Actin filament structure
Two twisted monomers, bound my Tropomyosin polypeptide chains
What are the two main descending pathways
Pyramidal Extrapyramidal
What is the reticular formation?
A set of interconnected Nuclei, located throughout the brain stem
The reticular formation integrates information from what structures
• Spinal cord • cerebral cortex • Basal Ganglia • Cerebellum
The number of muscle fibres per motor neuron relates to what?
That particular muscles movement function
IPSP is a result of what
Increased resting cell membrane potential
What 2 mechanisms determine the force of a muscle contraction
Number of recruited motor units Frequency of motor unit discharge
List 2 changes to neural function with age
40% decrease in number of spinal cord axons 10% decrease in nerve conduction velocity