Functional Anatomy Flashcards
structure of skeletal muscle
epimysium
fascicle
perimysium
muscle fibre
myofibril
Fascicle
a bundle of skeletal muscle fibres surrounded by the perimysium.
Epimysium
connective tissue sheath surrounding each muscle.
Perimysium
connective tissue which surrounds each bundle of muscle fibres
Muscle fibre
surrounded by a plasma membrane called the sarcolemma, which contains sarcoplasm. Amuscle fibreis composed of many fibrils, which give the cell its striated appearance.
Endomysium
connective tissue which surrounds each muscle fibre.
Myofibril
small thread like strands that run through each muscle fibre.
What is the slidinbg flimaent theory
Explains the shortening of the sarcomere (in a concentric contraction) and the resulting contraction of the muscle.
Explain the sliding filament theory
When there is a neurochemical stimulation, calcium ions are released from the sarcoplasmic reticulum into the sarcomere prompting a reaction in each muscle fibre between the myosin and the actin filaments.
Myosin filaments creates crossbridges (myosin heads) at regular intervals. These cross bridges attach and reattach at different times along the actin pulling on them to create movement and maintain tension
This causes the actin to move into the centre of the sarcomere, shortening the myofibril and causing the actin and myosin filaments to be almost fully overlapped when in a fully contracted position causing the H Zone and I band disappear.
As each sarcomere shortens, so does the total length of each muscle fibre
When the contraction finishes, the myosin and actin filaments return to a relaxed position (ATP releases energy causing myosin to detach from the actin and crossbridge is broken)
H.A.I.Z
H zone (distance between the actin filaments)
A band (length of the myosin filament)
I band (distance from the edge of myosin to the Z-Line)
Z line (edge of the sarcomere)
during contraction
H zone disappears/becomes smaller.
I band disappears/becomes smaller.
A band does not change in size.
motor unit
is the motor neuron and all the muscle fibres with which it connects to and stimulates.
small motor unit
innovates a small number of muscle fibres and are not strong, but they provide subtle and precise control.
large motor unit
innovates a large number of muscle fibres and are strong with little fine control.
dendrites of sensory neurons
pass impuluse/signal from the sensory receptors to the cell body of the sensory neurons/eye
axon of motor neurons
transmit impulse/signals away from cell body to the muscle fibres
neuron
a cell within the nervous system that transmits impulse/signals to other nerve cells/muscle
spinal cord
transmit impulse/signal from the brain to parts of the body
motor unit
causes contraction of the associated muscle fibres
force-velocity relationship
describes the inverse relationship between force production and the velocity of movement.
Concentric contraction
as more force is required the speed of movement cannot be as fast (or as less velocity is required the more force can be produced).
Eccentric contraction
as more force is required muscle velocity increases. As less force is required muscle velocity decreases.
Force – length relationship
relates directly towards the amount of muscle force that can be produced at a varying muscle length.
When full flexed/extended (out range of the contraction), not as much force can be produced, compared to the mid-range (resting length).
The force length relates directly to the mid-range (resting length) of a muscle the greatest force production can be generated due to the maximal / optimal overlap of actin and myosin.
All or none
motor unit receives stimulation/impulses/action potential to threshold, all the muscle associated with that motor unit will contract to their maximum level (all at the same time). Producing maximum force: more/greater number of motor units are used, activating large motor units, recruits appropriate muscle type 11
Muscle fibre - Type IIa
Fast contraction speed – used for speed endurance based activities
Moderate force of contraction
Fatigue resistance but not as much as slow twitch fibres
Generate greater force and more powerful contractions as they are larger than red fibres
Possess some aerobic characteristics such as moderate levels of myoglobin, mitochondria and blood capillaries
Stimulated by relatively large motor neurons and are stimulated at a moderate frequency
E.g. 200m / 400m(up to 70% fast twitch)
Muscle fibre - Type IIb
Rapid contraction speed – used for speed, strength and power based activities
High force of contraction
High capacity for anaerobic ATP production
Fatigue very quickly – no oxygen
Generate greater force and more powerful contraction as they are larger than red fibres
Possess very few aerobic characteristics such as low levels of myoglobin, mitochondria and blood capillaries, but very high anaerobic characteristics such as high levels of glycogen
Stimulated by very large motor neurons and are stimulated at a very high frequency
E.g. 100m / 200m Sprinter, High / Long Jumper, Thrower (up to 80% fast twitch),
Muscle fibre - Type 1
Slow twitch
Slow contraction speed – used for endurance activities
Low force of contraction
High capacity for ATP production – generates ATP using the aerobic system
Fatigue resistant
Contract repeatedly for continuous activity
Possess more aerobic characteristics such as high levels of myoglobin, mitochondria and blood capillaries
Stimulated by relatively small motor neurons and are stimulated at a low frequency
E.g. 10,000m / Marathon Runner, Endurance swimmer / cyclist (up to 80% slow twitch)
How the process of brain reciving signal
- Brain receives a signal from the sensory nerve
- Message travels via motor neurons- Structure Slide
- Arrives at the neuromuscular junction and has to cross the synapses (RIVER/GAP)
- Arrival of Action Potential which opens calcium channels Ca+ ions.
- Influx of calcium triggers a biochemical cascade 6. This causes the release of Acetylocholine which is a neurotransmitter into the syapse.
- Signal on the end plate then transmit nerve signals to the muscle fibre.
- This signal releases the calcium from the sarcoplasmic reticulum causing Sliding Filament Theory
- Nerves cells extend across the length of the Myofibril BUT only stimulate portions of the muscle belly
relationship between muscle contraction and nerve function
In order for muscles to contract or shorten, muscle fibres must be stimulated by nerve or electrical impulses sent via motor neurons.
The sensory neurons receive a stimulus (such as the starter gun) and sends electrical impulse to the brain (Central nervous system).
A message is sent from the brain, in the form of an action potential, down the spinal cord through to the motor neuron.
The motor neuron receives the signal and transmits it to the muscle fibre, which activates muscle movement.
