PHYSIOLOGY 1 Unit 2

LEARNING GOALS I will understand the anatomy of a muscle fibre. I will understand the components involved in muscle contraction.

WHAT WAS ANATOMY? Anatomy is the study of the structures of the various body systems

WHAT IS PHYSIOLOGY? Study of the functions of the various body systems

TOPICS IN THIS UNIT HOW OUR MUSCLES CONTRACT 2. HOW WE PRODUCE ENERGY FROM FOOD 3. HOW OUR CARDIO-VASCULAR SYSTEM WORKS 4. HOW OUR RESPIRATORY SYSTEM WORKS

MUSCLE CONTRACTION

OUR FOCUS: SKELETAL MUSCLE Attaches to bones of the skeleton to produce movement Voluntary Capable of very fast contractions = fatigues easily Examples!?!?

SKELETAL MUSCLE a single muscle is defined as...a number of muscle fibres: bound together by connective tissue and usually linked to bone via … Tendons!!

MUSCLE TEAMWORK Most muscles are arranged in pairs (e.g. biceps/triceps, quads/hams) When one group contracts, the other relaxes to allow for the movement: AGONIST - the muscle contracting ANTAGONIST - the muscle relaxing but...it ’ s not that simple (since most actions require other additional muscles to ‘ fine tune ’ the movement) e.g., teeth brushing

SYNERGISTS - muscles surrounding the joint being moved (helping the AGONIST) FIXATORS - steady joints closer to the body (work on the joint that is more proximal). Essentially stabilizes the origin.

MUSCLE TEAMWORK PRACTICE For each action listed, list 1 agonist, antagonist, 1 synergist & 1 fixator: elbow flexion knee flexion dorsiflexion hip extension shoulder flexion elbow extension Shoulder ABduction Plantar flexion

MUSCLE CELLS (FIBRES)

each ‘string’ is a muscle fibre (bundled up together) cut your meat against / through the fibre (against the grain) to make it easier to eat

A single muscle is made up of many cells or fibres diameter of fibres - varies btw mm and 0.1mm (NOTE: hair is about 0.15mm) length of fibres - depends on length of muscle (e.g. bicep fibres = 15 cm) cell organelles - because they are such big cells, they have multiple nuclei & because they use so much NRG, they have many mitochondria

Remember, each fibre is a CELL with it’s own set of organelles

sarcolemmamuscle cell membrane sarcoplasmic reticulum a network of membranes surrounding the myofibrils that contain Ca mitochondriaenergy production site

VIDEO

LOOKING OUTWARD (FROM MUSCLE FIBRE) individual muscle fibres are surrounded by a sheath of connective tissue, called the ENDOMYSIUM groups of muscle fibres are bound together with a sheath of connective tissue, called the... PERIMYSIUM the groups of muscle fibres are called FIBRE BUNDLES (fasicle) these bundles of muscle fibres are in turn bound together by a stronger sheath, called the EPIMYSIUM this group of bundles makes up a MUSCLE BELLY

VIDEO

LOOKING INWARD (FROM MUSCLE FIBRE) Within a single MUSCLE FIBRE, are many MYOFIBRILS that run the length of the fibre (# per fibre varies greatly)

Each MYOFIBRIL is made up of 1000 ’ s of SARCOMERES that attach end-to-end down the entire length of the MYOFIBRIL (i.e. think bands on a snake)

Inside these SARCOMERES are the actual proteins that are responsible for muscle contraction, ACTIN (thin filament) and MYOSIN (thick filament), stacked up on top of each other

During muscular contraction…the SARCOMERES are brought closer together (making muscle smaller) due to an overlap between ACTIN and MYOSIN

VIDEO

INSIDE MYOFIBRILS... Within 1 sarcomere, there are many myosin & actin filaments stacked in both directions

The sarcomere is often divided up into different zones to show how it behaves during muscle action.

VIDEO The Z - line separates each sarcomere. The H - Zone is the center of the sarcomere. distance btw. the actin filaments within the same sarcomere (only myosin) The M – Line is where adjacent myosin filaments anchor on to each other. It is the midpoint of a sarcomere The darker A - Bands are where myosin filaments align The lighter I – Bands are where actin filaments align. distance btw. the myosin filaments of 2 neighbouring sarcomeres (only actin) When muscle contracts the H-zone and I-band both shorten as the z-lines are pulled towards each other. In full contraction the H – Zone can disappear.

LEARNING GOALS I will understand the anatomy of a muscle fibre. I will understand the components involved in muscle contraction.