THE MUSCULAR THE MUSCULAR SYSTEMSYSTEM

What do you already know about What do you already know about muscle tissue?muscle tissue?

What is the definition of an organ?What is the definition of an organ?

Types of muscle tissueTypes of muscle tissue

Skeletal muscleSkeletal muscle

Cardiac muscleCardiac muscle

Smooth muscleSmooth muscle

FunctionsFunctions

1.1. Producing body movements by Producing body movements by changing chemical energy into changing chemical energy into mechanical energymechanical energy

2.2. Stabilizing body positionsStabilizing body positions

3.3. Generating heatGenerating heat

4.4. Moving substances Moving substances

Within the bodyWithin the body

Skeletal muscle anatomySkeletal muscle anatomy

Connective tissue around muscle Connective tissue around muscle ((epimysiumepimysium))– Extends to form tendon (dense regular Extends to form tendon (dense regular

connective tissue) – connects muscle to connective tissue) – connects muscle to periosteum of boneperiosteum of bone

Muscles: bundles of Muscles: bundles of fascicles (group of fascicles (group of fibers – cells) fibers – cells) surrounded by surrounded by perimysiumperimysium

Nerves and blood Nerves and blood vesselsvessels– At least 1 capillary At least 1 capillary

per muscle fiberper muscle fiber

Myofibrils= contractile organelles Myofibrils= contractile organelles stripesstripes

Sarcoplasmic reticulum - encircles Sarcoplasmic reticulum - encircles myofibrils= similar to smooth ER; myofibrils= similar to smooth ER; function = stores calciumfunction = stores calcium

Filaments (thin and thick)– inside Filaments (thin and thick)– inside myofibrils; don’t extend length of myofibrils; don’t extend length of fiber; contained in sarcomeresfiber; contained in sarcomeres

Anatomy of muscle fiberAnatomy of muscle fiber

No mitosisNo mitosis

Growth: hypertrophy due to Growth: hypertrophy due to hormones (testosterone, HGH)hormones (testosterone, HGH)

Sarcolemma = cell membraneSarcolemma = cell membrane

Sarcoplasm = cytoplasm Sarcoplasm = cytoplasm (glycogen!!)(glycogen!!)

Myoglobin Myoglobin – a protein– a protein = binds = binds with/release O2 for the mitochondriawith/release O2 for the mitochondria

Mitochondria = many!Mitochondria = many!

Don’t writeDon’t write

Review:Review:– SarcolemmaSarcolemma– SarcoplasmSarcoplasm– Sarcoplasmic reticulumSarcoplasmic reticulum– MyofibrilsMyofibrils– filamentsfilaments

HOW A MUSCLE CONTRACTSHOW A MUSCLE CONTRACTS

A neuron connects to a muscle fiber A neuron connects to a muscle fiber [called the neuromuscular junction (NMJ)][called the neuromuscular junction (NMJ)]

Arrival of nerve impulse causes release of Arrival of nerve impulse causes release of acetylcholine (ACh: a neurotransmitter – a acetylcholine (ACh: a neurotransmitter – a chemical).chemical).

ACh diffuses to receptors on muscular ACh diffuses to receptors on muscular membrane (sarcolemma), opening a Namembrane (sarcolemma), opening a Na++ ion channel, causing Naion channel, causing Na++ to enter the to enter the muscle fibermuscle fiber

Muscle contraction contMuscle contraction contCauses muscle action potential due to Causes muscle action potential due to change in membrane potential (b/c of change in membrane potential (b/c of addition of Naaddition of Na++ ) )Sarcoplasmic reticulum releases stored Sarcoplasmic reticulum releases stored CaCa+2 +2 into sarcoplasminto sarcoplasmCauses muscle contraction (sliding Causes muscle contraction (sliding filament mechanism):filament mechanism):– Unblocks actin (thin) so myosin (thick) heads Unblocks actin (thin) so myosin (thick) heads

can bind to themcan bind to them– Filaments slide past one another, shortening Filaments slide past one another, shortening

the musclethe muscle

Sliding filament mechanism

Sliding filament mechanismSliding filament mechanism

Lengths of filaments do not changeLengths of filaments do not change

Sarcomere shortensSarcomere shortens

Causes shortening of muscle fiber Causes shortening of muscle fiber and muscleand muscle

Plants/drugs effect NMJPlants/drugs effect NMJ

Botulinum toxin from bacterium Botulinum toxin from bacterium Clostridium botulinum blocks Clostridium botulinum blocks exocytosis of AChexocytosis of ACh

Curare – plant derivative – used on Curare – plant derivative – used on arrow/blowgun darts. Binds to/blocks arrow/blowgun darts. Binds to/blocks ACh receptorsACh receptors

Muscle physiologyMuscle physiology

Muscles tug on tendons which pull on Muscles tug on tendons which pull on bonesbones

One bone is pulled towards anotherOne bone is pulled towards another

Insertion towards originInsertion towards origin

Most cross a jointMost cross a joint

Muscle groupsMuscle groupsPrime mover and Prime mover and antagonistantagonist

Opposite actionsOpposite actions

Switch rolesSwitch roles

Opposite sides of Opposite sides of bone/jointbone/joint

Lever Lever systemssystems

Most of the bones of the limbs (arms & legs) act as levers. These levers are powered by muscles.A lever is a rigid rod able to rotate about a fixed point known as a fulcrum, formed by the joint. Any force applied to the lever is called the effort.A force that resists the motion of the lever, such as the downward force exerted by a weight on the bar, is called the load or the resistance.The contraction of the muscles is the effort and the part of the body concerned is known as the resistance or load.Bones of the body act as levers (a mechanical device) which create a mechanical advantage of strength or speed.

Muscle contractionMuscle contraction

Muscle fibers: all-or-noneMuscle fibers: all-or-none

Strength of muscle contraction: Strength of muscle contraction: depends on # of contracting fibersdepends on # of contracting fibers

Affects energy usageAffects energy usage

Providing energyProviding energyATP broken down during contractionATP broken down during contractionStore little ATP, must produce itStore little ATP, must produce it3 ways:3 ways:– Aerobic respiration: slow, requires O2, lots Aerobic respiration: slow, requires O2, lots

ATPATP– Anaerobic glycolysis and lactic acid Anaerobic glycolysis and lactic acid

formation: faster, no O2 needed, less ATPformation: faster, no O2 needed, less ATP– Creatine phosphate and ADP: CP not found Creatine phosphate and ADP: CP not found

in other cells, very fast, doesn’t lastin other cells, very fast, doesn’t last

Muscle fatigueMuscle fatigueno contraction no contraction even with even with stimulation - occurs stimulation - occurs from from oxygen debt oxygen debt (lactic acid builds (lactic acid builds up and ATP runs up and ATP runs low)low)

Types of muscle contractionsTypes of muscle contractions

Isotonic: with movementIsotonic: with movement

Isometric: muscle against immovable Isometric: muscle against immovable (or almost) object(or almost) object

Effect of exerciseEffect of exercise

Aerobic (endurance): results in Aerobic (endurance): results in muscles with resistance to fatigue. muscles with resistance to fatigue.

Resistance (isometric) training: Resistance (isometric) training: enlarged musclesenlarged muscles

In review……… In review……… (don’t write)(don’t write)

Lifting weights is an example of resistance Lifting weights is an example of resistance or endurance training?or endurance training?

The reaction of creatine phosphate and The reaction of creatine phosphate and ADP generates ATP quickly or slowly?ADP generates ATP quickly or slowly?

The ability of your body to use oxygen to The ability of your body to use oxygen to produce ATP is _____ respiration.produce ATP is _____ respiration.

True or False: The strength of a muscle True or False: The strength of a muscle contraction is determined by the amount contraction is determined by the amount of muscle fibers that are contracting.of muscle fibers that are contracting.

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The strength of a muscle contraction The strength of a muscle contraction depends on what?depends on what?

What is the relationship between the What is the relationship between the strength of a muscle contraction and strength of a muscle contraction and energy usage?energy usage?

Muscle fatigue is due to ____ debtMuscle fatigue is due to ____ debt

exampleexample

Running a 100 yd dash in 12 seconds Running a 100 yd dash in 12 seconds requires 6L of oxygen.requires 6L of oxygen.

But the max amount that could be But the max amount that could be delivered and used by your muscles delivered and used by your muscles (VO2 max) would be 1.2 L(VO2 max) would be 1.2 L

Oxygen debt?Oxygen debt?

= 4.8L= 4.8L

THE THE POINTPOINT

The more oxygen your body can take The more oxygen your body can take in and use determines your in and use determines your enduranceendurance

DON’T WRITEDON’T WRITE

Why are some Why are some people better at people better at endurance endurance activities?activities?

Why are some Why are some people FAST?people FAST?

Is it genetic? Is it Is it genetic? Is it training?training?

Types of muscle fibersTypes of muscle fibers1. Slow oxidative fibers1. Slow oxidative fibers– Little power (small in diameter); fatigue Little power (small in diameter); fatigue

resistant; many mitochondria. Adapted for resistant; many mitochondria. Adapted for maintaining posture & endurance activitiesmaintaining posture & endurance activities

2. Fast oxidative-glycolytic fibers2. Fast oxidative-glycolytic fibers– Intermediate in diameter, faster than #1 but Intermediate in diameter, faster than #1 but

briefer in duration. Adapted for: briefer in duration. Adapted for: walking/sprintingwalking/sprinting

3. Fast glycolytic fibers3. Fast glycolytic fibers– Large diameter (contract strongly/quickly); tire Large diameter (contract strongly/quickly); tire

quickly; large amount lactic acid build upquickly; large amount lactic acid build up– Short, rapid, intense movementShort, rapid, intense movement– Adapted for intense anaerobic movements of Adapted for intense anaerobic movements of

short duration: weight lifting/throwing a ballshort duration: weight lifting/throwing a ball

muscle fibers in musclesmuscle fibers in muscles

Muscle are a combo of different Muscle are a combo of different fibersfibers

Proportion of fibers is Proportion of fibers is individualindividual