Worksheet titled "Anatomy: Muscle Worksheet" listing various muscle-related terms such as Oxygen Debt, Muscle Fatigue, Heat Production, and others, each paired with a numbered blank for definitions.

Here’s the correct matching for the Anatomy: Muscle Worksheet based on standard physiological definitions:

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✔ Correct Answers:

A. Oxygen Debt → 9. Amount of oxygen needed to convert lactic acid to glucose
*(After intense exercise, muscles accumulate lactic acid; oxygen debt refers to the extra O₂ required post-exercise to metabolize it back to glucose or pyruvate.)*

B. Muscle Fatigue → 11. Muscle loses ability to contract
*(Fatigue occurs when a muscle can no longer generate force due to metabolic exhaustion, depletion of ATP, or accumulation of waste products.)*

C. Heat Production → 13. Muscles are a major source of energy/heat
*(Muscle contractions generate heat as a byproduct — this is essential for thermoregulation.)*

D. Threshold Response → 4. Minimal strength needed to cause a contraction
*(The threshold stimulus is the minimum intensity required to trigger an action potential and subsequent muscle contraction.)*

E. All/None Response → 1. If muscle contracts at all, it contracts completely
*(This refers to the “all-or-none” law — a single muscle fiber either contracts fully in response to a stimulus above threshold, or not at all.)*

F. Twitch → 2. Contraction that only lasts a fraction of a second
*(A twitch is a brief, weak contraction caused by a single action potential.)*

G. Cramp → 12. Muscle contracts spasmodically and not relax
*(Cramps are involuntary, painful, sustained muscle contractions often due to electrolyte imbalance or overuse.)*

H. Myogram → 7. Recording of a muscle contraction
*(A myogram is a graphical recording (e.g., from EMG or force transducer) showing the tension or electrical activity during contraction.)*

I. Sustained Contraction → 5. A sustained forceful contraction
*(This refers to prolonged, strong muscle contraction — often achieved through summation or tetanus.)*

J. Tetanic Contraction → 15. Muscle is exposed to a series of contractions, does not complete relaxation
*(Tetanus = fused, continuous contraction due to rapid stimulation preventing full relaxation between twitches.)*

K. Muscle Tone → 6. Muscles continually partially contracted
*(Tone = low-level, involuntary contraction maintaining posture and readiness for movement.)*

L. Latent Period → 10. The time between a stimulus and response
*(Latent period = brief delay after stimulus before contraction begins — includes time for excitation-contraction coupling.)*

M. Recruitment Units → 8. Increasing the number of motor units contracting in a whole muscle
*(Recruitment = activating more motor units to increase force output — key for graded muscle response.)*

N. Period of Contraction → 14. Period where muscle pulls on attachment
*(This is the phase where cross-bridges form and the muscle generates tension/shortens.)*

O. Period of Relaxation → 3. Period where muscle returns to its former length
*(Relaxation phase — Ca²⁺ is pumped back into SR, tropomyosin blocks actin sites, muscle lengthens passively.)*

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📝 Final Answer Key:

| Term | Number |
|-----------------------|--------|
| A. Oxygen Debt | 9 |
| B. Muscle Fatigue | 11 |
| C. Heat Production | 13 |
| D. Threshold Response | 4 |
| E. All/None Response | 1 |
| F. Twitch | 2 |
| G. Cramp | 12 |
| H. Myogram | 7 |
| I. Sustained Contraction | 5 |
| J. Tetanic Contraction| 15 |
| K. Muscle Tone | 6 |
| L. Latent Period | 10 |
| M. Recruitment Units | 8 |
| N. Period of Contraction | 14 |
| O. Period of Relaxation | 3 |

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✔ This matches standard human anatomy & physiology terminology. Let me know if you’d like diagrams or further explanation of any term!