Neuromuscular System Flashcards
Summaries how a nerve impulse initiates a muscular contraction
- Electrical impulse begins at brain transmitted to muscle VIA spinal cord
- Motor neuron e stimulate muscle fibers within motor unit
- Point at which nerve meets the muscle fiber is motor end plate
- Nerve to muscle is neuromuscular junction
- Calcium ions enter synaptic knob + actyelochine is released
- Causes action potential along muscle fiber
- Triggering sliding filament theory
Summaries how recruitment patterns of motor units enables power + endurance athletes to meet demands of their events
- Strength of contraction depends upon number of motor units recruited
- Power athlete recruited MORE motor units
- Power athlete receives more units of type II muscle fibers
- Endurance athlete recruits more units of type I muscle fibers
- Endurance athlete use different spatial summation patterns to delay fatigue
Examine the function of the neuromuscular system in a muscle contraction stage 1
- Nervous system sends signal to muscular system to contract
- Electrical impulse from CNS transmitted to muscles VIA spinal cord
- Nerve cells/motor neurons transmit message
- Impulse arrives at motor end plate triggering acetylcholine + spread of impulse across synaptic cleft = muscular system produces force producing movement
Examine the function of the neuromuscular system in a muscle contraction stage 2
- Neuromuscular system is interaction between nervous system + muscular system to regulate/control movement
- 1 motor neurons cannot stimulate whole muscle
- Motor neurons + fibers stimulated are motor units
- Number of fibers innervated by motor unit varies
- Precision of movement required determines fibers innervated
- Reqruitment based on response time/speed of contraction
Examine the function of the neuromuscular system in a muscle contraction stage 3
- If impulse is a suitable strength the muscle fiber is innervated at neuromuscular junction
- An action potential is reached or not - ALL OR NONE law determines if motor unit contracts
- Wave summation + graduation of contraction
Using sliding filament theory, summaries process of muscular contraction
RESTING:
- Muscle relaxed due to lack of Ca2+ in myofirbil
EXCITATION:
1. Nervous impulse arrives at neuromuscular junction = release of acetylcholine
2. Causes depolarization of motor end plate that travels through muscle
3. Calcium is released from sarcoplasmic reticulum
4. Ca+ binds to troponin
5. Tropomyosin moves/changes shape, exposing active/binding site on actin
6. Myosin filaments attach to actin = cross-bridge
CONTRACTION:
7. Breakdown of ATP = energy which enables power stroke
8. Breakdown of ATP releases energy = enables myosin to pull actin filaments inwards + shortening muscle
9. Myosin detaches from actin + cross bridge broken when ATP mol binds to myosin head
RECHARGE:
10. Ca++ removed and process repeated
11. When ATP broken down = myosin head attaches to actin binding site further along actin filament
12. Repeated pulling of actin over myosin = ratchet mechanism
13. Process of muscular contraction can last as long as there ATP/Ca+ stores
RELAXATION:
14. Once impulse stops, Ca+ pumped back to SR and Actin returns to resting position = muscle lengths + relax
Role of dendrites + axon + mylein sheath + nodes of rancher + motor end plate + axon terminal
- highly branches process + specialized to receive stimuli from sensory neurons/organs
- conducts nerve impulse to other cells
- insulates nerve impulse /conduction
- gaps in sheath where action potential jumps from node to node
- transfer impulse from motor neuron to muscle fibers (effector)
- ends w synaptic end bulb contracting neuromuscular substance
Outline stages of excitation and contraction during muscular contraction
EXCITATION
- Nerve impulses reaches neuromuscular junction/motor end plate
- Acetylcholien released across synaptic cleft
- Nervous stimulation of muscle tissue
- Triggers an action potential
CONTRACTION
- Ca+ ions released/bind to troponin
- Active site on actin exposed
- ATP provides energy for cross bridge formation
- Myosin heads from cross bridge w actin
- Myosin heads move/ratchet Pe chains pulled towards center of myosin
Summaries function of any 4 labeled parts of motor neurons
-Cell body transits signal + controls function of the cell
- Axon terminal = Info passed to next cell here
- Dendrites = receive info from other neurons conduct impulse to cell body
Explain how 4 features of type IIx muscle fibers an able them for anaerobic physical activities s
-High in PC = high rate of contraction
- High stores of PC = Mantain high rate of contraction for longer
- Increased fiber size = Allows increased strength
- High force production = Allows speed/power
- High actin/myosin = Allows faster contraction
Explain how training can adjust recruitments of different muscle fiber type s
- low intensity endurance training = rotational recruitment of different slow twitch muscle fibers
- High intensity training e.g sprinting recruits more type IIx fibers
- High intensity training = more synchronous muscle fiber recruitment
- As muscles get stronger —> fewer fibers needed to produce force needed
- As load increases IIa recruited to aid type I + load becomes greater still IIa will support IIx
- High intensity training increases rate of recruitment fibers
Name a track event that would use fast oxidative glycolysis IIa muscle fibers + why
- 200m / 400m/ 800m
- Fibres contain large numbers of mitochondria + myoglobin
- Manufcature + split ATP quickly
- Utilise both aerobic + anaerobic metabolism
- Produces fast muscle contraction
- Produces strong muscle contraction
- Fatigue slower than type 2x
Explain how 4 different characteristics of slow twitch fibres (type 1) enable the to be better suited for endurance activities
- High mitochondrial density =Higher rate of aerobic energy production
- High myglobin content = Enables higher rate of oxygen delivery
- High capillary density = Enables higher rate of oxygen delivery + higher rate of gaseous exchange
- High oxidative enzyme activity = Higher rate of aerobic energy performance
- Smaller fiber diameter allows faster gas exchange due to smaller diffusion distance
Characteristics of fast glycolysis IIx
- Low conc of myglobin
- limited capillary network
- low levels of mitochondria
- large motor neurons size 1000+
- large fiber diameter
- small myglobin in contents
- not resistant to force
- very fast speed of contraction
- high levels of force produced
How do muscle contract
A band= actin + myosin
I band= only actin filaments
M line/H zone= only myosin filaments
Z line= one sarcomere
When a muscle contracts, actin filaments slide over mysoin filaments:
- I band shorter
- Z lines closer tgt + sarcommere shortens
- H zone narrower
- A bands stay same length
- so everything shorter EXCEPT A bands
