Section 2: Muscular System
What is a muscle
tissue made up of many muscle cells and associated connective tissue. There are 3 main muscle types: skeletal, cardiac and smooth
What is a skeletal muscle cell
an individual cell that when activated produces force that can lead to motion
What is a sacromere
the fundamental unit of skeletal and cardiac muscle. Many sacromeres are arranged in sequence within a single myofibril and many myofibrils make up a muscle cell
what are myofilaments
sacromeres are composed of a highly organized arrangement of myofilaments composed of actin and myosin that interact with each other to generate force (slide across each other)
Put these in order of size: muscle fiber, muscle cell, myofibrils, fascicle, myofilaments
muscle cell, fascicle, muscle fibers, myofibrils, myofilaments
cross bridge function
the binding of actin to myosin myofilaments and change in the conformation of myosin. The cross bridge cycle is the process involving attachment, conformational change and detachment (with ATP) that generates force.
What is the sliding filament theory
Theory explaining the mechanism of muscle contraction associated with the cross bridge cycling and the sliding of myofilaments past each other to generate force.
what is a motor neuron
neuron that synapses with skeletal muscle cells
Motor unit
is a motor neuron and all the muscle cells that it innervates (controls)
what is neuromuscular junction
the synapse between a motor neuron and a skeletal muscle cell
muscle action potential
an action potential (depolarization followed by repolarization) on the membrane of a skeletal muscle cell
Steps for neuromuscular activation
1. Depolarization of a motor neuron (neuronal action potential) - electrical
2. Neurotransmitter release at neuromuscular junction (acetylcholine (ACH)) - chemical
3. Depolarization of muscle fibre - electrical
4. cross-bridge formation and sacromere shortening - mechanical
muscle fibers act as an all or none matter true or false
true
What are two ways you can control the amount of force a whole muscle generates
1. motor unit recruitment
2. the action potential frequency (as action potential frequency increases, force increases.
what determines the maximum isometric force a whole muscle can generate
the muscle size, more muscle cells means more sacromeres which causes more force
what is an EMG
EMG is a technique to measure electrical activity produced by muscles (measurement of muscle action potentials that occur when a muscle is stimulated
How is EMG taken
1. skin preperation and proper electrode placement
2. a small needs is inserted into a muscle and the electrical activity is recorded directly
what is the y axis on EMG tracing
mV, V
What is the x axis on the EMG tracing
time
Is there a relationship between EMG amplitude and muscle force
Yes, as EMg increases, force increases
How does stimulus repose occur (steps)
1. stimulus occurs
2. Sensory - specialized cells in our eyes detect light
Afferent
3. Cortical - the neural information is processed (combined with prior behavioural instructions)
Efferent
4. Motor - an effect is determined
5. muscles are activated to perform the appropriate task
What is reaction time
the time it takes the CNS to sense, process and intiate a response to a stimulus
What is Movement time
Time it takes for person to execute a specific movement (does not include reaction time). The time from the onset of muscle activation (EMG) to the end of the response.
What is response time
Reaction time and movement time combined
Factors that reaction time is dependent on
1. Stimulus intensity and modality (e.g., visual, auditory)
2. Simple reaction time: there is only one stimulas and one response
3. choice reaction time: there are a number of different stimuli presented each requiring a different response
what is dual task interference
simultaneous performance of two tasks often leads to perfomance deficits in the component task, it is a proff of capacity limitation in cognition