NEUROMUSCULAR JUNCTION

• CONSISTS OF:

• 1. THE AXONAL TERMINAL OF A SOMATIC MOTOR NEURON.

• 2. SYNAPTIC CLEFT

• 3. THE MOTOR END PLATE.

NEUROMUSCULAR JUNCTION

NEUROMUSCULAR JUNCTION

NEUROMUSCULAR JUNCTION

NEUROMUSCULAR JUNCTION

• FOR MORE INFORMATION

• SEE MODULE NUMBER 2

• OF THE MUSCULAR CD ROM.

SLIDING FILAMENT THEORY

SLIDING FILAMENT THEORY

SLIDING FILAMENT THEORY

SLIDING FILAMENT THEORY

SLIDING FILAMENT THEORY

SLIDING FILAMENT THEORY

SLIDING FILAMENT THEORY

• FOR MORE INFORMATION

• SEE MODULE NUMBER 3

• OF THE MUSCULAR CD ROM.

MOTOR UNIT

• A MOTOR UNIT IS A SOMATIC MOTOR NEURON AND ALL OF THE MUSCULE CELLS IT INNERVATES.

• THE NUMBER OF MUSCLE FIBERS PER MOTOR UNIT MAY BE AS HIGH AS SEVERAL HUNDRED OR A FEW AS FOUR.

MOTOR UNIT

• AS A RESULT, STIMULATION OF A • SINGLE MOTOR UNIT CAUSES A WEAK

• CONTRACTION OF THE • ENTIRE MUSCLE, OR A NUMBER OF MOTOR

UNITS MAY CAUSE A STRONG CONTRACTION OF THE ENTIRE MUSCLE.

MUSCLE TWITCH

• THE RESPONSE, A CONTRACTION

• FOLLOWED BY RELAXATION, OF A

• MUSCLE TO A SINGLE BRIEF

• THRESHOLD STIMULUS.

MUSCLE CONTRACTION

• THERE ARE THREE PHASES:

• 1. LATENT PERIOD• 2. PERIOD OF

CONTRACTION• 3. PERIOD OF RELAXATION

LATENT PERIOD

• THE PERIOD TIME, USUALLY A

• FEW MILLISECONDS, AFTER THE

• DECISION TO CONTRACT A SKELETAL

• MUSCLE AS BEEN MADE AND THE

• ACTUAL SHORTING OF THE MUSCLE

• HAS OCCURRED.

PERIOD OF CONTRACTION

• THE PERIOD OF CONTRACTION IS

• WHEN CROSS BRIDGES ARE ACTIVE,

• FROM THE ONSET TO THE PEAK OF

• TENSION DEVELOPMENT, AND THE

• MYOGRAM TRACING RISES TO A PEAK.

PERIOD OF CONTRACTION

• IF THE TENSION BECOMES GREAT

• ENOUGH TO OVERCOME THE

• RESISTANCE (WEIGHT BEING

• MOVED),THE MUSCLE SHORTENS.

PERIOD OF RELAXATION

• THE PERIOD OF RELAXATION

• FOLLOWS THE PERIOD OF

• CONTRACTION, AND IS THE RESULT

• OF Ca2+ ION CONCENTRATION

• RETURNING TO NORMAL LEVELS.

PERIOD OF RELAXATION

• THE MUSCLE TENSION DECREASES TO

• ZERO AND THE TRACING

• RETURNS TO THE BASELINE. IF THE

• MUSCLE HAS SHORTENED DURING

• CONTRACTION, IT NOW RETURNS TO

• ITS INITIAL LENGTH.

THREE PHASES OF MUSCLECONTRACTION

GRADED MUSCLE RESPONSES

• MUSCLE CONTRACTION CAN BE GRADED

• IN TWO WAYS:

• 1. BY CHANGING THE SPEED OF STIMULATION.

• 2. BY CHANGING THE STRENGTH OF THE STIMULUS.

GRADED MUSCLE RESPONSES

• MUSCLE RESPONSES TO AN INCREASE IN THE NUMBER OF STIMULI:

• 1. TREPPE

• 2. TEMPORAL (WAVE) SUMMATION

• 3. INCOMPLETE TETANI

• 4. COMPLETE TETANI

TREPPE

• A MUSCLE MUST HAVE BEEN AT REST FOR A PERIOD OF TIME.

TREPPE

• ALL PHASES OF MUSCLE CONTRACTION

• ARE PRESENT AND HAVE

• NOT BEEN ALTERED.

TREPPE

• THE STIMULI ARE EQUIDISTANCE APART.

TREPPE

• THE AMOUNT OF TENSION IS INCREASING DUE TO WARMING OF THE MUSCLE. THE INCREASE IN TEMPERATURE CAUSES ENZYMES TO BE MORE EFFECTIVE.

TREPPE

• THE AMOUNT OF TENSION DEVELOPED, WITH THE SAME STRENGTH OF STIMULUS, INCREASES AND THEN REMAINS THE SAME.

MYOGRAMS

INCOMPLETE TETANI

• IF THE STIMULUS• STRENGTH IS HELD • CONSTANT AND THE

• MUSCLE IS STIMULATED AT AN• INCREASINGLY

FASTER• RATE, INCOMPLETE• TETANI RESULTS.

INCOMPLETE TETANI

• ALL PHASE OF MUSCLE CONTRACTION ARE PRESENT.

• HOWEVER, THE PERIOD OF RELAXATION IS SHORTED.

INCOMPLETE TETANI

• THE STIMULI ARE OF THE SAME STRENGTH, HOWEVER, THEY ARE BECOMING CLOSER TOGETHER.

INCOMPLETE TETANI

• THE AMOUNT OF TENSION IS INCREASING DUE TO AN INCREASE IN THE NUMBER OF Ca2+.

COMPLETE TETANUS

• WHEN ALL EVIDENCE OF

• MUSCLE • RELAXATION

• DISAPPEARS AND THE • CONTRACTIONS FUSE

• INTO A SMOOTH,• SUSTAINED

• CONTRACTION,• COMPLETE TETANUS

• RESULTS.

COMPLETE TETANUS

• NOTICE THAT THE PERIOD OF RELAXATION HAS

• COMPLETELY• DISAPPEARED.

COMPLETE TETANUS

• THE STIMULI ARE BEING DELIEVED ONE AFTER ANOTHER, WITH NO TIME ELAPSED.

COMPLETE TETANUS

• THE TENSION HAS PLATEAUED, BECAUSE ALL OF THE MYOFILAMENTS ARE FORMING BONDS. THERE IS A MAXIMUM OF Ca2+

IN THE MYOFIBRIL.

MUSCLE TONE

• MUSCLE TONE KEEPS THE MUSCLES

• OF THE BODY FIRM, HEALTHY, AND

• READY TO RESPOND TO STIMULI.

• IN ADDITION, MUSCLE TONE HELPS

• STABLIZE JOINTS AND MAINTAIN

• POSTURE.

MUSCLE TONE

• MUSCLE TONE IS THE RESULT

• OF ASYNCHRONOUS MUSCLE

• MOTOR UNIT CONTRACTION.

ENERGY FOR CONTRACTION

• 1. ATP

• 2. CREATINE PHOSPHATE

• 3. GLYCOLYSIS

• 4. AEROBIC CELLULAR RESPIRATION

MUSCLE FATIGUE

• TRUE MUSCLE FATIGUE IS THE

• RESULT OF BUILD UP OF ACIDIC

• COMPOUNDS, MAINLY LACTIC ACID,

• A REDUCTION IN THE AMOUNT OF ATP, AND ELECTROLYTE

IMBALANCES.