Muscle contractions

Tropism

Movement of organisms towards eexternal stimulus

Sacromeres

Composed of strands of actin & myosin protein. Responsible for muscle contractions.

Myofibrils

Contractile units, composed of repeating sacromeres

What stimulates the release of Ca²⁺

An action potential arriving at muscle fibres stimulates the sarcoplasmic reticulum to release.

What does Ca²⁺ bind to and why?

Ca²⁺ binds to tropomyosin

Move & expose myosin binding sites on actin filament.

Where does ATP attach to

Myosin head

What happens after ATP hydrolysis

Myosin head cocks towards Z line

What is powerstroke

Shortening of sacromeres by sliding actin and myosin more compactly

Z line

M line

Myosin

Actin

Light band

Dark band

What is Titin

Long fibrous elastic protein that stretches from Z line to M line. Acts as molecular spring.

Purpose of Titin

Helps sacromeres to recoil after stretching to prevent over extension of muscle

Intercostal muscles

Muscles involved in ventilation

Internal intercostal muscle location

Deeper within muscles

External intercostal muscle location

Surface of muscle

Orientation of Internal intercostal muscle

diagonally along direction of ribs

Orientation of External intercostal muscles

Parallel to direction of ribs

What is titin and what is its purpose?

It is a very long protein (longest in human body)

Connects z-line and m-line, acts as spring to keep actin and myosin in place.