A&P - Chapter 17 (Part 2) Flashcards
What is released when you transmit a nerve impulse across a synapse?
Neurotransmitters
How do nerve impulse’s work? (6)
- Neurotransmitters cross the synapse
- Binds with receptors on the muscle fibres sarcolemma
- Excites the sarcolemma
- Initiates a nerve impulse across the sarcolemma
- Triggers the SR to release Ca into the sarcoplasm
- Resulting in muscle contraction
What plays a critical role in a series of events that allow binding of myosin and actin?
Ca released from the SR
What are the steps of muscle contraction? (4)
- Each myosin head in the thick filament moves into a resting position after an ATP molecule binds and transfers its energy
- Ca released from the SR binds to troponin in the thin filament
- this allows tropomyosin to shift from its position blocking the active sites of actin - Each myosin head binds to an active site on a thin filament and displaces the remnants of ATP hydrolysis
- The release of stored energy from step 1 brings everything back to the original position
- pulls actin along
What are the remnants of ATP hydrolysis? (2)
- ADP
2. P
When will each head of actin stay bound?
Until another ATP molecule binds to it and pulls it back into its resting position
What happens to myosin during contraction?
It binds to actin which forms cross bridges that act as levers to pull the myofilaments past each other
What happens to the myofilaments as the muscles contract?
They slide past each other
What do contractions require? (2)
- Ca
- cross bridge formation - ATP
- energy
What actively removes Ca in order to stop contractions?
SR
What are 2 basic energy source pathways for muscle contraction?
- Aerobic
2. Anaerobic
Aerobic
Occurs when lots of O2 is available in blood
- very slow process
Anaerobic
Occurs when O2 levels in the blood are low
- very fast process
What energy system would you use for long term activities?
Aerobic
What energy system would you use for short term activities?
Anaerobic
What does anaerobic system produce?
Lactic acid
- contraction in the absence of adequate oxygen
What is a symptom of lactic acid?
Soreness
How do you make up for oxygen debt?
Heavy breathing after exercise
What is fatigued caused by?
Repeated muscle stimulation without adequate rest
What does fatigue lead to?
Reduced strength of muscle contraction
- eventually lead to loss of muscle’s ability to contract
What does repeated muscular contraction depletes? (2)
- Cellular ATP stores
2. Outstrips the ability of the blood supply to replenish oxygen and nutrients to make more ATP
What is required for survival?
The ability to maintain relatively stable body temperature
What is the by product of skeletal muscle contractions?
Heat
Where does energy for contractions come from?
Breaking ATP bonds
What is most energy used for? What is the second thing energy is used for?
- Contraction
- Heat
- regulates body temperature
What 2 structures are needed for muscle contraction?
- Motor neuron
2. Neuromuscular junction
Motor neuron
Specialized nerve fibre that transmits an impulse to a muscle, causing a contraction
Neuromuscular junction
Specialized point of contract between a nerve ending and the muscle fibre it innervates
What 2 things makes up a motor unit?
- Motor neuron
2. Muscle cell it innervates
What does it mean if you have fewer number of fibres in a motor unit?
More precise movements
What does it mean if you have more number of fibres in a motor unit?
The more powerful the contraction available it is
