How they support our bodies systems………. Muscles How they support our bodies systems……….

Muscles 20–D4.1k explain how the motor system supports body functions (i.e., digestive, circulatory,respiratory, excretory and locomotory), referencing smooth, cardiac and striated muscle 20–D4.2k describe, in general, the action of actin and myosin in muscle contraction and heat production.

Muscles support all body function Muscles support all body function. They work to help in digestion to contract the stomach, help our heart pump oxygen to the rest of the body, help our lungs expand and contract and help us move. The type of job that is being accomplished dictates what type of muscle we need.

Smooth muscles: these are long and tapered and only have one nucleus they can be found in blood vessels and internal organ walls they contract involuntarily Examples– digestive tract,

Smooth muscles:

Peristalsis in the Stomach 1 5 2 4 3

Cardiac Muscles: Only found in the heart are tubular and striated only have one nucleus Contract involuntarily

Skeletal Muscles: these are also tubular and striated very long and have many nuclei contract voluntarily usually attached to the skeleton function is to support the body and make bones move maintain body temperature through ATP breakdown protect internal organs and stabilize joints found in pairs – one contracts and the other relaxes (biceps and triceps)

Skeletal Muscle

Answer these questions on your own! What is a muscle fibre?   What is a muscle? What are myofibrils? What are myofilaments?

Electron Micrograph of Striated Muscle tussue

Muscle Fibre Contraction coordination of 2 myofilaments – actin and myosin actin myofilament consists of 2 strands of protein (actin) molecules that are wrapped around each other (like beads)

myosin myosin myofilament consists of 2 strands of protein (myosin) molecules wounds around each other but about 10 times longer than actin and has a different shape. One end consists of a long rod while the other is a double headed globular region (the “head”)

Use Figure 10.5 to follow along the Sliding Filament Model A – myofilament contracts of the myosin moves bending up and towards the rod. The heads are now chemically bonded to the actin myofilament   B – the actin is pulled along as the myosin head bends and the actin slides past the myosin C - ATP is used to unbond the myosin and actin and reposition the myosin D - Myosin head rebonds with actin further down the fibre.

Actin is anchored at one end of each microfilament (Z- Line) The movement pulls the Z-Line (its anchor) along with it In the diagram below, A is relaxed, B is contracting and C is contracted http://www.youtube.com/watch?v=ren_IQPOhJc Cardiac Muscle

MuScle Video Muscle Video

Muscle Energy Energy for Muscle Contraction Muscles get ATP in 3 ways: Aerobic cellular respiration (makes most of the ATP for muscles) Lactic acid formation (occurs in oxygen deficit) The break down of a molecule called creatine phosphate  

Creatine Phosphate: A high energy molecule that build up when a muscle is resting It generates ATP by losing its phosphate. The phosphate combines with ADP to make ATP and the molecule then becomes creatine This is the fastest way to make ATP for muscles The energy last for about 8 seconds When the muscle is resting, a phosphate from an ATP gets transferred back to the creatine making creatine phosphate