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Anatomy Lecture BIOL 223 > Exam 2: Tension Production Energy use and Muscular Activity > Flashcards

Exam 2: Tension Production Energy use and Muscular Activity Flashcards

1
Q

Tension “Pulling Strength”

Tension “Pulling Strength”

A
  • Sliding of actin and myosin filaments causes sarcomere shortening
  • In a muscle cell, all sarcomeres shorten causinf muscle cell shorten
  • Tension in a muscle depends on:
  • Tension that develops in individual muscle cells during contraction
  • Numer of muscle cell that contract
  • Amount of shortening depends in resistance
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2
Q

Fiber Shortening

Fiber Shortening

A
  • As sarcomeres shorten, muscle cell shortens, producing tension
  • Pulls on connective tissue and bone to which it is attached
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3
Q

Tension

Tension

A

Tension produced in individual muscle fibers (Muscle cells) can vary due to:
* Length-tension relationship
* Frequency of stimulation by motor neuron

Tension produced by entire muscle can vary due to:
* Number of muscle cells receving nerve stimulation, commanding them to contract
* Muscle cells are grouped in motor units

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4
Q

Tension production by muscle fibers: Length-Tension relationship

Tension production by muscle fibers: Length-Tension relationship

A

Amount of tension depends on number of cross bridges formed
* Depends on degree of overlap of actin and myosin filaments

Skeletal muscle contracts most forecully over a narrow range of resting lengths

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5
Q

Tension Production by Muscle Fibers: Frequency of Stimualtion

Tension Production by Muscle Fibers: Frequency of Stimualtion

A

Twitch
* Cycle of contraction, relaxation produced by a single action potential in a muscle cell
* not typical of most normal skeletal muscle activity

Latent Phase - Action potential occurs
* No contraction until Ca2+ is released from SR

Contraction Phase - Tension rises to Peak
* Ca2+ moves tropomyosin off actin active sites
* Myosin cross bridges form, actin is pulled

Relaxation phase - Tension falls to resting levels
* Ca2+ is pumped back into Sr
* Actin sites coverd by tropomyosin
* No cross bridges remain

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6
Q

Tension Production by Muscle Fibers: Frequency of Stimulation

Tension Production by Muscle Fibers: Frequency of Stimulation

A

Most muscular activities invlove sustained musclular contraction
* Produced by high frequency of action potentials in muscle cell
* Produced in response to high frequency of action potentials in motor neuron (high frequency of stimulation)
* Summation of tension produces greater tension

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6
Q

Tension Production by Muscle Fibers: Frequency of Stimulation

Tension Production by Muscle Fibers: Frequency of Stimulation

A

Most muscular activities invlove sustained musclular contraction
* Produced by high frequency of action potentials in muscle cell
* Produced in response to high frequency of action potentials in motor neuron (high frequency of stimulation)
* Summation of tension produces greater tension

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7
Q

Summation

Summation

A

Repeated stimulation produced before relaxation phase has been completed
* Summation of tension caused by build up of calcium ions in sarcoplasm

Complete tetanus
* Mamximum tension production in a muscle cell - maximum cross bridge formation

Tetanus “disease”
* caused by clostridium tetani bacteria
* Bacterial toxin causes high frequency of action potentials in motor neurons

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8
Q

Summation

Summation

A

Repeated stimulation produced before relaxation phase has been completed
* Summation of tension caused by build up of calcium ions in sarcoplasm

Complete tetanus
* Mamximum tension production in a muscle cell - maximum cross bridge formation

Tetanus “disease”
* caused by clostridium tetani bacteria
* Bacterial toxin causes high frequency of action potentials in motor neurons

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9
Q

Treppe vs. Wave Summation

Treppe vs. Wave Summation

A
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10
Q

incomplete vs. Complete Tetanus

incomplete vs. Complete Tetanus

A
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11
Q

Tension

Tension

A

Tension produced in individual muscle fibers (cells) can vary due to:
* Length-Tension relationship
* Frequency of stimulation

Tension Produced by entire muscle can vary even more due to:
* Number of muscle cells reciving nerve stimulation, comanding them to contract
* Muscle cells are grouped in motor units

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12
Q

Tension Production by Skeletal muscls Number of active motor units

Tension Production by Skeletal muscls Number of active motor units

A

Motor Units:
* All the muscle fibers (cells) innervated by one motor neuron
* ammount of tension produced in a muscle determined by number of motor units activated
* Asynchronous Motor unit summation for sustained contractions

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13
Q

Tension Production by Skeletal muscls Number of active motor units

Tension Production by Skeletal muscls Number of active motor units

A

Differences in number and size of motor units in different muscles determines precision of control of movements

Small motor unit - precise control
* One motor neuron innervates a small number of muscle fibers

Large Motor Unit - Gross movement control
* One motor neuron innervates a large number of muscle fibers

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14
Q

Muscle Tone

Muscle Tone

A
  • Restin tension in a skeletal muscle
  • In any muscle, some motor units are always active: tense and firm the muscle
  • Which motor units are active is constantly changing, muscle tone is not produced by a specific subset of motor units
  • Stabalizes bones and joints
  • Greater resting muscle tone causes higher resting rate of metabolism
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15
Q

Contractions: Isotonic and Isometric

Contractions: Isotonic and Isometric

A

Isotonic - tension rises, length of muscle changes
* Concentric - muscle tension exceeds resistance and muscle shortens
* Eccentric - peak tension developed is less than the resistance, muscle elongates

16
Q

Contractions: Isotonic and Isometric

Contractions: Isotonic and Isometric

A

Isometric - tension rises, length of muscle remains constant
* Tension produced never exceeeds resistance
* Muscle as a whole does not shorten but individual muscle fibers shorten until internal connective tissues and tendons are taut
* Cannot shorten further because tension does not exceed resistance

17
Q

Lengthening a Muscle

Lengthening a Muscle

A

No active mechanism for a muscle fiber elongation
* A muscle cell does not cause itself to lengthen after contraction process ends

Returns to resting length due to:
* Recoil in elastic components in connective tissue
* Contraction of opposing muscle groups
* Gravity

18
Q

Energy use and muscle contraction

Energy use and muscle contraction

A
  • Muscle contraction requires large amounts of ATP
  • Muscle cells stores only enough high energy molecules to sustain contraction until additional ATP can be generated
  • ATP and Creatine Phopshate (CP) reserve last about 15 seconds once contraction begins
  • Muscle cell must genertae ATP at approx the same rate as it is used for remainder of contraction
19
Q

Energy use and muscle contraction

Energy use and muscle contraction

A
  • Muscle contraction requires large amounts of ATP
  • Muscle cells stores only enough high energy molecules to sustain contraction until additional ATP can be generated
  • ATP and Creatine Phopshate (CP) reserve last about 15 seconds once contraction begins
  • Muscle cell must genertae ATP at approx the same rate as it is used for remainder of contraction
20
Q

Creatine Phosphate and ATP

Creatine Phosphate and ATP

A

Creatine Phosphate (CP) reserves
* Adenosine Triphosphate (ATP) not used for long term storage of energy
* At rest, muscle cell makes more ATP than needed, extra ATP transfers high energy phosphate to creatine for storage
* CP reserves releases stored energy to convert ADP to ATP when ATP is needed at start of contraction
* Start of exercise CP+ADP <–> C + ATP
* At RestC+ATP <–> CP + ADP

21
Q

Cellular Respiration

Cellular Respiration

A

ATP Generation
* Aerobic cellular resp: most ATP used for resting muscle and for moderate levels of muscle activity
* Aerobic and Anerobic glycolosis pathways needed to generate additonal ATP for Peal Performance

22
Q

Aerobic Metabolism

Aerobic Metabolism

A

Aerboic Metabolism
* Uses O2 and releases Co2

Occurs in mitochondria
* Citric acid cycle
* CO2 is produces

Electron transport Chain
* ATP synthesis
* O is used as the final electron acceptor

23
Q

Muscle cell ATP Generation

Muscle cell ATP Generation

A

Resting muscle fibers rely on aerobic metabolism of Fatty Acids to generate ATP
* FA absorbed from ciruclation
* Broken down to 2-carbon units of acetyl CoA which enter directly into the Citric Acid Cycle
* Excess ATP used to store gluclose into glycogen, and create creatine phosphate . Also pumps ions and recycles waste products

23
Q

Muscle cell ATP Generation

Muscle cell ATP Generation

A

Resting muscle fibers rely on aerobic metabolism of Fatty Acids to generate ATP
* FA absorbed from ciruclation
* Broken down to 2-carbon units of acetyl CoA which enter directly into the Citric Acid Cycle
* Excess ATP used to store gluclose into glycogen, and create creatine phosphate . Also pumps ions and recycles waste products

24
Q

Muscle Cell ATP Generation

Muscle Cell ATP Generation

A

Contracting Muscle Fibers rely on aerobic and anaerobic metabolism of glucose
* Ammount of aerobic vs. anerobic metabolism depends on intensity of muscle contraction (Moderate vs. Peak)
* Glucose comes from circulation and breakdown of glycogen reserves within muscle cell

25
Q

Gluclose Metabolism in Muscle Cells

Gluclose Metabolism in Muscle Cells

A

Pyruvate Metabolism - anaerobic
* If oxygen supply to cells is too slow to allow all of pyruvate to be metabolized aerobically by cellular resp, rest of pyruvate converted to Lactic acid
* Conversion of pyruvate to lactic acid recycles cofactors needed by glycolysis enzymes

At peak performace
* 1/3 Aerobic (mito)
* 2/3 Anerobic glucose->pyruvate->lactic acid

26
Q

Anaerobic Metabolism

Anaerobic Metabolism

A

Anerobic Metabolism
* Produces ATP rapidly
* Allows muscle cell to generate additional ATP whem mitochondiral cellular rep pathway is unable to meet cells energy demands

Disadvantages
* Inneficient use of glucose
* Lactc acid lowers intracellular PH

27
Q

Recover Period

Recover Period

A

Begin immediatley after activity ends
Oxygen Debt (excess post-exercise oxygen consumption)
* Ammount of oxygen required during resting period to make enough ATP to restore muscle to normal conditions
* Rebuild ATP and Creatine Phosphate leveles
* Recycle lactic acid to make pyruvate
* Revuild Glycogen reserves

28
Q

Muscle Fatigue

Muscle Fatigue

A

Fatigued Muscle - a muscle that can no longer perform at required level of activity

Possible causes of fatigue:
* Exhaustion of energy resources
* Build up of lactic acid and lowering of PH
* Psychological Fatigue if lactic acid eneters the blood stream

Anatomy Lecture BIOL 223 (10 decks)

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