Chapter 9 Part 2 (Lecture) Flashcards
List the Events that Occur at the Neuromuscular Junction
- Arrival of action potential at synaptic terminal
- AP causes Ca2+ to enter axon synaptic terminal
- Ca2+ stimulates exocytosis of ACh vesicles
- ACh enters synaptic cleft
- ACh binds at motor and plate
- Appearance of an action potential in the sarcolemma
- Return to intial state
List the Step of the Contraction Cycle
- Energized myosin head is “cocked”
- Exposure of myosin binding site on actin, forms the cross bridge
- Pivoting of myosin heads (Power Stroke)
- Detachment of cross bridge
2 Ways to Stop the Contraction Cycle
- Run out of Ca2+
- Run out of ATP
Why is Ca2+ important in the Contraction Cycle?
Ca2+ is used to bind to the troponin which changes shape and moves tropomyosin exposing myosin binding sites.
Why is ATP important in the Contraction Cycle?
ATP is the energy source.
Treppe Graph
Wave Summation
Incomplete Tetanus
Complete Tetanus
3 Types of Skeletal Muscle Fibers
- Slow Oxidative (SO) Fibers
- Fast Oxidative Glycolytic (FOG; Intermediate) Fibers
- Fast Glycolytic (FG) Fibers
Slow Oxidative (SO) Fibers
- Least powerful
- Fatigue resistant, red, myoglobin, many mitochondria, small fiber diameter
- Suited for endurance-type activity
- Marathon or triathalon
Fast Oxidative Glycolytic (FOG; Intermediate) Fibers
- Moderately fatigue resistant, red to pink, intermediate diameter
- Suited for sprinting and walking
Fast Glycolytic (FG) Fibers
- Fatigable
- Suited for short term intense or powerful movements, white, few mitochondria, large fiber diameter
- Weight lifting
Sliding Mechanism of Muscle Contraction
Thin slides over thick to cause a contraction
Motor Unit
One motor neuron and many skeletal muscle fibers
- One motor neuron to multiple muscles
- One muscle to only one motor neuron
Motor-End Plate
The specific part of a skeletal muscle fiber’s sarcolemma directly beneath the NMJ
Neurotransmitter
Chemical substance released from a motor end fiber; causes stimulation of the sarcolemma of muscle fiber
Achetylcholine
Triggers action potential that releases Ca2+
Achetylcholinesterase
Removes ACh from synaptic cleft ending muscle stimulation
Events involved in skeletal muscle fibers contraction beginning with the necessary motor impulse initiated by the brain.
- NMJ
- Contraction Cycle
Explain why and how a contracted skeleta muscle relaxes.
Ca2+ is pumped out of the sarcoplasm, actin is covered up so myosin can’t bind with actin.
Name the 3 pathways that regenerate energy/ATP in muscle cells
- Aerobics
- Anaerobics
- Creatine-Phosphate
How is Lactic Acid produced in muscle cells and what its accumulation causes.
Produced by anaerobic respiration.
Muscles shut down until Lactic Acid is removed.
O2 Debt
Demand for O2 outstripes O2 supply
Muscle Fatigue
Muscle runs out of ATP
Twitch
Single contraction followed by an imediate relaxation
What is meant by the “all or nothing” response in skeletal muscle fibers.
The threshold must be reached
Explain how smooth and graded contractions of a skeletal muscle are produced.
Based on strength and frequency of stimuli
Define the term used to describe a myogram that shows a series of twitches with increasing strength.
Wave summation
Name the term when a myogram illustrates a sustained contraction that lacks even slight relaxation between twitches.
Complete Tetanus
Muscle Recruitment
Beacuse a whole muscle is composed of many motor units, controlled by many different motor neurons, simultaneous contraction of all units does not necessarily occur.
Isometric
Contraction but not shortening
Isotonic
Contraction with shortening
Force (Factors)
Size and Fiber Type
Velocity (Factors)
Fiber Type
Duration (Factors)
Fiber type
