BIO1022 Chapter Notes - Chapter Prescribed: Troponin, Cognitive Map, Myoglobin
30 May 2018
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BIO1022 Week 4 Readings
concept 40.1
- animal form and function are correlated at all levels of organisation
- exchange with the environment
• exchange of nutrients, waste products and gases occurs as substances
dissolve in an aqueous solution move across the plasma membrane of
each cell
• internal body fluids link exchange surfaces to body cells
• the spaces between cells are filled with fluid - in many animals called
interstitial fluid
• complex body plans also include a circulatory fluid such as blood -
exchange between interstitial fluid and the circulatory fluid enables cells
throughout the body to obtain nutrients and get rid of wastes
- hierarchical organisation of body plans
• cells - tissues - organs - organ system
- coordination and control
• endocrine system
•
o signalling molecules released into the bloodstream by endocrine
cells are carried to all locations in the body
o signalling molecules - hormones
o
▪ only cells that have receptors for particular hormones
respond
• nervous system
•
o neurons transmit signals along dedicated routs connecting specific
locations in the body
• both work to maintain a stable internal environment
concept 50.5
- muscle cell contraction relies on the interaction between protein structures
called thin and thick thilaments
• thin - globular protein actin
• think - myosin molecules
- muscle contraction is the product of filament movement powered by chemical
energy
- vertebrate skeletal muscle
• moves bones and body
• within a typical skeletal muscle is a bundle of long fibres running parallel
to the length of the muscle
• inside a muscle cell - a longitudinal bundle of myofibrils - which contain
thick and thin filaments
•
o the myofibrils in muscle fibres are made up of repeating sections
called sarcomeres - basic contractile units of skeletal muscle
- the sliding filament model of muscle contraction
• a contracting muscle shortens but the filaments that bring about
contraction stay the same length
find more resources at oneclass.com
find more resources at oneclass.com
• the thick and thin filaments ratchet past each other - powered by the
mason molecules
• Each myosin molecule has a long tail region and a globular head
region. The tail adheres to the tails of other myosin molecules, bind- ing
together the thick filament. The head, which extends to the side, can bind
ATP. Hydrolysis of bound ATP converts myosin to a high-energy form that
binds to actin, forming a cross-bridge.
• When a new molecule of ATP binds to the myosin head, the cross-bridge
is broken.
• Muscle contraction requires repeated cycles of bind- ing and release. In
each cycle, the myosin head freed from a cross-bridge cleaves the newly
bound ATP and binds again to actin.
- the role of calcium and regulatory proteins
• calcium ions and proteins bound to actin play crucial roles in
muscle contraction and relaxation
• tropomyosin - a regulatory protein and the troponin complex a set of
additional regulatory proteins are bound to the actin strands of thin
filaments
• motor neurone cause muscle contraction by triggering the release of Ca2+
into the cytosol of muscle cells with which they form synapses
• The arrival of an action potential at the synaptic terminal of a motor
neuron causes release of the neurotransmitter acetylcholine. Binding of
acetylcholine to receptors on the muscle fibre leads to a depolarisation,
triggering an action po- tential. Within the muscle fibre, the action
potential spreads deep into the interior, following infoldings of the
plasma membrane called transverse (T) tubules. These make close
contact with the sarcoplasmic reticulum (SR), a specialised endoplasmic
reticulum. As the action potential spreads along the T tubules, it triggers
changes in the SR, opening Ca2+ channels. Calcium ions stored in the
interior of the SR flow through open channels into the cytosol and bind to
the tropophin complex, imitating muscle fibre consctrivtion
- nervous control of muscle tension
• in vertebrates - each branched motor neuron may synapse with many
muscle fibres - although each fibre is controlled by only one motor
neuron
• a motorunit consists of a single motor neuron and all the muscle fibres it
controls
• when a motor neuron produces an action potential - all the muscle fibres
in its motor unit contract as a group
• As more and more of the motor neurons controlling the muscle are
activated, a process called recruitment, the force (tension) developed by a
muscle progressively increases
• tetanus - occurs when the rate of muscle contraction is so high that
the muscle fibre cannot relax at all between stimuli - the twitches fuse
into one sustained contraction
- types of skeletal muscle fibres
• oxidative and glycolytic fibres
•
o fibres that reply mostly on respiration - oxidative fibres
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Animal form and function are correlated at all levels of organisation. Hierarchical organisation of body plans cells - tissues - organs - organ system. Muscle cell contraction relies on the interaction between protein structures called thin and thick thilaments thin - globular protein actin think - myosin molecules. Muscle contraction is the product of filament movement powered by chemical energy. The tail adheres to the tails of other myosin molecules, bind- ing together the thick filament. The head, which extends to the side, can bind. In each cycle, the myosin head freed from a cross-bridge cleaves the newly bound atp and binds again to actin. Binding of acetylcholine to receptors on the muscle fibre leads to a depolarisation, triggering an action po- tential. Within the muscle fibre, the action potential spreads deep into the interior, following infoldings of the plasma membrane called transverse (t) tubules. These make close contact with the sarcoplasmic reticulum (sr), a specialised endoplasmic reticulum.
