BIOL1008 Lecture Notes - Lecture 20: Myoglobin, Endoplasmic Reticulum, Patellar Reflex
Muscles
Role of muscles
Movement- joint movement
Posture- holding position
Joint stabilisation- aid ligaments to maintain joint (takes pressure off joints)
Heat production- most commonly shivering, but any activity produces heat as a
product
Muscles
Types of muscles
oSmooth (lines internal organs)
oCardiac (heart)
oSkeletal or striated
Voluntary movement
Nervous control
Ability to stretch and extend
Returns to original length by shortening or contracting when stretching ceases or
elasticity
Muscle structure
A muscle fibre (contractile) is multinucleate- cells have fused together to form a
single muscle fibre
Myofibrils are made up of contractile units- characterised by thick (myosin) and thin
(actin) filaments, both are proteins
Several of each component in parallel to build up a muscle
Striated muscle structure
Muscle made of parallel fibres
Fibres made of parallel myofibrils
Myofibrils composed of sarcomeres in series
Each sarcomere has Z-lines, A bands, and I bands
Bands contain thick (myosin) and thin (actin) filaments
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Microscopic structure of striated muscle
Cross-bridges formed between head of myosin and actin
Contraction occurs as cross-bridges release from one point on actin and reform at
new site
Rate of contraction can differ as result of types of myosin
A bands- where myosin and actin filaments overlap
I bands- where there is only actin filaments
Z lines- where the actin filaments connect
Contraction of muscles
Caused by interaction between the lollipop heads of myosin fibres and the actin
fibres
The heads connect to the actin move backwards pull the actin past them
release them connect to another one repeat
Energy is required to break the bonds to allow another contraction to occur- no
energy is required to attach the myosin to the actin
Fast and slow twitch fibres
Rate of contraction is determined by type of myosin
Rate is dependent upon how fast cross-bridges are broken
Requires energy in the form of ATP (adenosine triphosphate)
Role of tendons
Collagenous
Connect muscle to bone by forming continuous
collagen connection through fibres
Tendon of origin connects muscle to bone nearest
to centre of body
Tendons of insertion connect to bone distal further
from centre of body
find more resources at oneclass.com
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Document Summary
Joint stabilisation- aid ligaments to maintain joint (takes pressure off joints) Heat production- most commonly shivering, but any activity produces heat as a product. Types of muscles: smooth (lines internal organs, cardiac (heart, skeletal or striated. Returns to original length by shortening or contracting when stretching ceases or elasticity. A muscle fibre (contractile) is multinucleate- cells have fused together to form a single muscle fibre. Myofibrils are made up of contractile units- characterised by thick (myosin) and thin (actin) filaments, both are proteins. Several of each component in parallel to build up a muscle. Each sarcomere has z-lines, a bands, and i bands. Bands contain thick (myosin) and thin (actin) filaments. Cross-bridges formed between head of myosin and actin. Contraction occurs as cross-bridges release from one point on actin and reform at new site. Rate of contraction can differ as result of types of myosin. A bands- where myosin and actin filaments overlap.
