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THE MUSCULAR SYSTEM
FUNCTIONS OF MUSCLE
• PRODUCING MOVEMENT – BOTH INTERNAL AND WHOLE –
BODY
• MAINTAINING POSTURE
• STABILIZING JOINTS
• GENERATING HEAT
3 TYPES OF MUSCLE TISSUE
1. SKELETAL MUSCLE – USED TO
MOVE BONES
2. SMOOTH MUSCLE – MOVES
DIGESTIVE TRACT, URINARY
SYSTEM, REPRODUCTIVE
ORGANS, AND DIAPHRAGM
3. CARDIAC MUSCLE – PUMPS
HEART
SKELETAL MUSCLE ANATOMY
• MUSCLES CELLS ARE LONG FIBERS COVERED BY THE SARCOLEMMA (PLASMA
MEMBRANE)
• EACH MUSCLE CELL HAS MANY NUCLEI PUSHED ASIDE BY LONG ORGANELLES
CALLED MYOFIBRILS
• MYOFIBRILS HAVE LIGHT AND DARK BAND, THAT GIVE MUSCLE A STRIPED
(STRIATED) APPEARANCE
• MYOFIBRILS ARE MADE OF CHAINS OF TINY CONTRACTING UNITS CALLED
SARCOMERES.
• A SARCOMERE IS MADE OF
THREADLIKE PROTEINS CALLED
MYOFILAMENTS
• THERE ARE TWO TYPES OF
MYOFILAMENTS
• THIN (ACTIN) FILAMENTS
• THICK (MYOSIN) FILAMENTS
• AREAS OF THICK MYOSIN (AND ACTIN) FILAMENTS MAKE UP THE
DARK “A” BANDS
• AREAS BETWEEN THESE THICK FILAMENTS ARE LIGHT “I” BANDS
MUSCLE CONTRACTIONS
• MYOSIN FILAMENTS HAVE PROJECTIONS
CALLED “HEADS”
• THESE MYOSIN HEADS GRAB HOLD OF THE
ACTIN FILAMENTS AND PULL THEM
TOGETHER
• THIS CAUSES MUSCLES TO CONTRACT
HOWEVER, THIS DOESN’T HAPPEN ON ITS
OWN
HTTPS://YOUTU.BE/4201SRN0WLY
REVIEW OF ATP
• IN ORDER TO CONTRACT MUSCLES, NEED
ATP
• ATP IS A MOLECULE FOUND IN THE BODY
THAT SUPPLIES ENERGY
• IT IS ALSO CALLED ADENOSINE
TRIPHOSPHATE
• ENERGY IS RELEASED FROM ATP WHEN
THE LAST PHOSPHATE IS REMOVED FROM
IT.
• MUSCLES CAN GET ATP FROM 3 PROCESS
• USING CREATINE PHOSPHATE (CP)
• CREATINE PHOSPHATE IS A HIGH – ENERGY MOLECULE FOUND IN
MUSCLE FIBERS BUT NOT OTHER CELLS
• IT MAKES ATP BY ADDING ON A PHOSPHATE GROUP TO ADP
• BENEFITS AND DOWNFALLS OF USING
CREATING PHOSPHATE
• THIS WORKS GREAT TO CREATE ATP
QUICKLY, BUT CP SUPPLIES MAY BE USED UP
IN ABOUT 15 SECONDS
• USING AEROBIC RESPIRATION
• ABOUT 95% OF MUSCLE ENERGY (ATP) IS MADE USING
AEROBIC RESPIRATION
• AEROBIC RESPIRATION BREAKS GLUCOSE INTO CARBON
DIOXIDE AND WATER USING OXYGEN IN THE MITOCHONDRIA
OF CELLS.
• BENEFITS AND DOWNFALLS OF USING
AEROBIC RESPIRATION
• AEROBIC RESPIRATION IS VERY
GOOD AT MAKING A LOT OF ATP
BUT CAN BE SLOW AND REQUIRES A
CONSTANT SUPPLY OF OXYGEN
• IN THE FIRST STEPS OF AEROBIC
RESPIRATION, GLUCOSE IS SPLIT INTO
TWO MOLECULES OF PYRUVIC ACID
AND 2 ATP ARE RELEASED.
• AFTER THIS, IN THE PRESENCE OF
OXYGEN, THE PYRUVIC ACID WILL GO
ON TO CREATE MORE ATP.
• USING ANAEROBIC RESPIRATION
• ANAEROBIC RESPIRATION, TOO, CONTAINS
THE FIRST STEPS TO CREATE PYRUVIC ACID
• IN ANAEROBIC RESPIRATION, HOWEVER, THERE
IS NOT ENOUGH OXYGEN FOR PYRUVIC ACID
TO COMPLETE THE STEPS TO CREATE MORE
ATP.
• THIS CAN HAPPEN BECAUSE
• THE SUPPLY OF OXYGEN OR GLUCOSE IS
TOO LOW
• THE MUSCLE ACTIVITY IS TOO INTENSE
• IN THIS CASE, THE PYRUVIC ACID IS TURNED
INTO LACTIC ACID AND NO MORE ATP IS
PRODUCED.
• BENEFITS AND DOWNFALLS OF USING ANAEROBIC
RESPIRATION
• ANAEROBIC RESPIRATION ONLY MAKES ABOUT
3% AS MUCH ATP AS AEROBIC RESPIRATION
• THE BUILDUP OF LACTIC ACID DURING
PROLONGED PERIODS OF ANAEROBIC
RESPIRATION MAY CAUSE A BURNING
SENSATION THAT EXISTS DURING EXERCISE.
• HOWEVER, ANAEROBIC RESPIRATION IS OVER
2X FASTER THAN AEROBIC AND CAN PRODUCE
MUCH OF THE ATP NEEDED FOR UP TO A
MINUTE OF STRENUOUS ACTIVITY
MUSCLE CONTRACTION
• IN ORDER FOR MUSCLES TO WORK, THEY HAVE TWO SPECIAL FUNCTIONS…
• IRRITABILITY (THE ABILITY TO RECEIVE AND RESPOND TO STIMULUS)
• CONTRACTIBILITY (THE ABILITY TO SHORTEN WHEN ADEQUATE STIMULUS IS RECEIVED)
• MUSCLES ALSO NEED NERVES IN ORDER TO BE STIMULATED TO WORK (CONTRACT)
• ONE NERVE CELL MAY STIMULATE A FEW MUSCLE CELLS OR HUNDREDS OF THEM,
DEPENDING ON THE MUSCLE AND THE WORK IT DOES
• SKELETAL MUSCLES MOVE BY THE LAW OF “ALL-OR-NONE” CONTRACTION IN A
MUSCLE CELL.
• THAT IS, IT WILL ONLY FULLY CONTRACT OR NOT CONTRACT AT ALL.
• HOWEVER, MUSCLE ORGANS (CONSISTING OF 100S OF MUSCLE CELLS) WILL REACT
TO STIMULI WITH GRADED RESPONSES.
• THEY MAY CHANGE THE FREQUENCY OF CONTRACTION IN CELLS, OR CHANGE
THE NUMBER OF CELLS BEING CONTRACTED.
• MUSCLES CAN VARY IN THE AMOUNT OF ENERGY PUT INTO THE
CONTRACTIONS THEY DO.
• TWITCHES ARE SHORT JERKY MOVEMENTS OF MUSCLES CAUSED BY BREAKS BETWEEN
CONTRACTIONS OF MUSCLE CELLS.
• UNFUSED TETANUS IS WHEN MUSCLES ARE STIMULATED MORE RAPIDLY, SO THAT THERE IS
ALMOST NO RELAXATION BETWEEN CONTRACTIONS.
• FUSED TETANUS IS WHEN MUSCLE IS STIMULATED SO RAPIDLY THAT IT DOES NOT RELAX
BETWEEN CONTRACTIONS. (CREATES A SMOOTH CONTRACTION)
2 TYPES OF MUSCLE CONTRACTIONS
• THERE ARE TWO TYPES OF MUSCLE CONTRACTIONS….
• ISOTONIC (SOME TONE/TENSION) – NORMAL CONTRACTIONS;
MYOFILAMENTS SLIDE TOWARD ONE-ANOTHER, MUSCLE SHORTENS,
MOVEMENT OCCURS
• ISOMETRIC (SOME LENGTH) – UNSUCCESSFUL CONTRACTIONS; TENSION
INCREASES BUT MYOFILAMENTS DO NOT SLIDE, MUSCLE STAYS SAME
LENGTH, NO MOVEMENT OCCURS.
• HAPPENS WHEN WE ARE STRUGGLING TO MOVE SOMETHING WE CANNOT (EX: 2TON TRUCK)
MUSCLE TONE
• MUSCLE TONE IS THE STATE OF
CONTINUOUS PARTIAL
CONTRACTION IN THE MUSCLE
• IT IS TYPICALLY UNNOTICEABLE
• IT OCCURS WHEN A MUSCLE IS FIT
AND HEALTHY
MUSCLE FATIGUE
• MUSCLE FATIGUE MAY OCCUR WHEN WE EXERCISE OUR MUSCLES STRENUOUSLY FOR A
LONG PERIOD OF TIME
• A MUSCLE BECOMES FATIGUED WHEN IT WILL NOT CONTRACT EVEN THOUGH IT IS
STIMULATED TO DO SO.
• MUSCLE FATIGUE IS BELIEVED TO BE CAUSED BY OXYGEN DEBT.
• OXYGEN DEBT IS THE STATE OF LACKING THE NECESSARY AMOUNT OF OXYGEN TO SUSTAIN
RIGOROUS MUSCLE ACTIVITY
• (WITHOUT OXYGEN, MUSCLES CANNOT PRODUCE ENOUGH ATP TO KEEP FUNCTIONING)
POSITIVE EFFECTS OF AEROBIC EXERCISE
• AEROBIC EXERCISE IS ANY SUSTAINED ACTIVITY THAT INCREASES THE NEED FOR OXYGEN. IT IS
BENEFICIAL IN THAT IT…..
1.
CREATES STRONGER, MORE FLEXIBLE MUSCLES
2.
MAKES OVERALL BODY METABOLISM MORE EFFICIENT
3.
IMPROVES DIGESTION
4.
ENHANCES COORDINATION
5.
MAKE SKELETON STRONGER
6.
ENLARGES HEART TO PUMP MORE BLOOD
7.
MAKES LUNGS MORE EFFICIENT AT GAS EXCHANGE
POSITIVE EFFECTS OF RESISTANCE EXERCISE
• RESISTANCE EXERCISES RESULT WHEN MUSCLES ARE WORKING AGAINST AN ALMOST
IMMOVABLE OBJECT. THESE EXERCISES HAVE SOME BENEFITS, LIKE……
1.
INCREASE IN MUSCLE SIZE AND STRENGTH
2.
INCREASE IN CONNECTIVE TISSUE HOLDING MUSCLE