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Chapter 43

LIFESCI 2 Chapter 43: Chapter 43 Notes

Life Sciences
Course Code
Esdin Joseph

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Chapter 43 Notes
Neural Pathway
o Skin receptors → Sensory Neuron → Interneuron → Motor neuron → Effector
o Extremely rapid response
Classification of muscles
o Muscles are contractile tissue
o 3 types
Skeletal voluntary
Smooth involuntary
Radial and circular muscles in the eye
Cardiac involuntary
Levels of Organization
o Muscle
Muscle fiber
o Myofibril
o Each myofibril is made of functional units of contraction called sarcomeres
o Each sarcomere is bound by a network of interconnecting proteins called Z lines
o Thick filaments are composed of a contractile protein (myosin)
Myosin head
Acting binding site
ATP binding site
Myosin is connected to the Z line by the protein Titin
Each myosin molecule is made of two heads and two tails
o Thin filaments contain a contractile protein (actin) and two regulatory proteins
(troponin and tropomyosin)
Globular protein that polymerizes to form intertwined helix
Actin has a binding site for myosin
Tropomyosin is the ribbon like protein that raps around the binding site
Made of three spherical subunits
o Actin binding site
o Tropomyosin binding site
o Calcium binding site
Actin binding site is blocked by tropomyosin in order to regulate
o Contraction is the interaction between the thick and thin filaments
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