9A.3

Question 1

Motor Neuron=

Answer 1

• uses a process called an axon to conduct nerve impulses
• allows for contraction of muscle
• FUNCTIONALLY connects to the muscle fiber, but not physically
• can attach to many muscle fibers(avg. 150)

Question 2

Synapse

Answer 2

• space that info can pass across-> synaptic cleft
• communication occurs using neurotransmitters

Question 3

The point at which the muscle fiber and motor neuron meet is…

Answer 3

neuromuscular junction

Question 4

Motor End Plate=

Answer 4

-usually one for each muscle fiber
-abundant nuclei and mitochondria

Question 5

Motor Unit=

Answer 5

-all muscle fibers of motor unit will contract and relax together

Question 6

Neuromuscular Junction (NMJ)

Answer 6

• where nerves meet

Question 7

Motor Neuron (def)=

Answer 7

-neurons that stimulate effectors (muscle/ glands)

Question 8

Synapse (def)=

Answer 8

site of functional connection between a motor neuron and muscle fiber

Question 9

Motor end plate (def)=

Answer 9

are of sarcolemma that receive neurotransmitters from motor neuron

Question 10

Motor unit (def)=

Answer 10

combination of the motor neuron and muscle fibers it controls

Question 11

Acetylcholine (ACh)

Answer 11

• during a skeletal muscle contraction, motor neurons will release it across the synaptic cleft
  -synthesized in the cytoplasm and stored in vesicles
  -nerve impulse forces release of vesicles
  
  • attaches to ACh receptors on the motor end plate, stimulating the muscle fiber (30-40 million)
  • fiber creates an electrical signal called a “muscle impulse”

Question 12

Muscle impulse

Answer 12

-changes sarcolemma and transmits impulse in all directions
- most important change will be at the use of Ca^2+

Question 13

where is the NMJ usually found

Answer 13

the middle of a fiber

Question 14

ATP is necessary for both contraction and relaxation

Answer 14

• muscle fibers only have enough ATP for brief contraction
• must be regenerated

Question 15

Creatine phosphate (Def)=

Answer 15

much more abundant than ATP in muscle fibers

Question 16

Creatine phosphate

Answer 16

-transfers stored energy to ADP to form ATP again

Question 17

after about 10 sec of contraction, begins to break down glycogen

Answer 17

• approx. 15-20 min of energy than fat

Question 18

Oxygen debt and fatigue

Answer 18

• many ATP molecules are made during cellular respiration, thus requiring high amounts of glucose
• muscles also have myoglobin
• function of respiratory and cardiovascular systems

Question 19

Myoglobin=

Answer 19

made in muscle cells and binds oxygen
- gives skeletal muscle reddish color
- can store oxygen temporarily for tissue (more attractive than hemoglobin)
- reduces a muscles requirement for constant blood supply

Question 20

Oxygen debt

Answer 20

• after a few minutes of strenuous activity, oxygen is not supplied fast enough for aerobic respiration
• anaerobic reactions begin, building up lactic acid
  
  • diffuses out and is carried to liver
  • liver begins to use ATP and O2 to react with the lactic acid
  • creates oxygen debt
• athletic training increases ones ability to do aerobic reactions

Question 21

Fatigue=

Answer 21

prolonged oxygen debt can lead to the inability of a muscle to control contraction

Question 22

Fatigue

Answer 22

• mostly due to accumulation of the lactic acid
  
  • lowers pH level, inhibiting muscle response

Question 23

Causes of Fatigue

Answer 23

• decreased blood flow
• ion imbalances
• (psychological loss of desire to continue usually counters this)
• Can also cause CRAMPS :(

Question 24

Cramps=

Answer 24

• sustained painful, involuntary muscle contractions
• decreased electrolyte concentration leads to uncontrolled stimulation

Question 25

Sarcomeres

Answer 25

• the functional unit of contractions

Question 26

Sliding Filament Theory

Answer 26

• these are the parts within fibers that will shorten
• Thick and thin filaments will not change shape, but rather slide past each other
• the Z- line will therefore move closer together, shortening the sarcomere

Question 27

what occurs in 2 parts

Answer 27

Contraction and Relaxation

Question 28

Contraction

Answer 28

• ACh arrives at sarcolemma forming a electrical muscle impulse
• Ca^2+ are released thru T-tubules flooding the sarcoplasm
• attach to troponin of actin filaments
• “opens up” their binding sites
• shape change that occurs produces the “power stroke” of contraction
• once complete, ATP binds to myosin again releasing actin
• these steps can repeat as long as ATP is available and Ca^2+ is present in high levels (fully contracted)

Question 29

Contraction

Answer 29

• ACh arrives at sarcolemma forming a electrical muscle impulse
• Ca^2+ are released thru T-tubules flooding the sarcoplasm
• attach to troponin of actin filaments
• “opens up” their binding sites
• shape change that occurs produces the “power stroke” of contraction
• once complete, ATP binds to myosin again releasing actin
• these steps can repeat as long as ATP is available and Ca^2+ is present in high levels (fully contracted)

Question 30

Relaxation

Answer 30

• Acetylcholmesterase (AChE) decomposes any ACh left in the synapse and at the motor end plate
• as muscle impulse stops, Ca^2+ is reabsorbed into the sarcoplasmic reticulum (no more ACh)
• Cross- bridge linkages break
• muscle fiber relaxes (titin