amp Reflexes Proprioception and Movement PSK 4U Unit 4 Day 4 Excitation Contraction Coupling Muscles work by converting electrical and chemical energy into mechanical energy The process of muscle contraction as a whole is often referred to as excitationcontraction coupli ID: 562555
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Slide1
Excitation-Contraction Coupling & Reflexes, Proprioception and Movement
PSK 4U Unit 4, Day 4Slide2
Excitation-Contraction Coupling
Muscles work by converting electrical and chemical energy into mechanical energy!
The process of muscle contraction as a whole is often referred to as “excitation-contraction coupling”
The “excitation” part describes the steps from when the electrical signal comes from the neuron and Ach is released, which in turn causes the release of calcium from
sarcoplasmic
reticulum which in turn exposes myosin binding sites on
actin
.
The “contraction” part describes the actual contraction portion (discussed as sliding filament theory)Slide3
Excitation-Contraction Coupling
Goes into a lot more detail on how:
SR is depolarized
Ach is
recirculatedSlide4
*CORRECTION*The 10 steps of the Sliding Filament Theory are actually NOT all classified as part of the SFT:
Message is sent down axon
Axon terminal releases Ach
Ach receptors on
sarcolemma
receive Ach
This stimulates the release of Calcium ions inside the muscle fibre (from
sarcoplasmic
reticulum)
Calcium binds to
troponin
(on
tropomyosin
)
Tropomyosin
(wrapped around
actin
) swivels off
This shows myosin binding sites
Myosin binds through the energy of ATP
Myosin attach, rotate, detach and attach again to “grab”
actin
and pull towards its centre – the
powerstroke
When calcium is depleted, when ATP is gone, the muscle fibre passively returns to its resting stateSlide5
*CORRECTION*The 10 steps of the Sliding Filament Theory are actually NOT all classified as part of the SFT:
Message is sent down axon
Axon terminal releases Ach
Ach receptors on
sarcolemma
receive Ach
This stimulates the release of Calcium ions inside the muscle fibre (from
sarcoplasmic
reticulum)
Calcium binds to
troponin (on tropomyosin)Tropomyosin (wrapped around actin) swivels offThis shows myosin binding sitesMyosin binds through the energy of ATPMyosin attach, rotate, detach and attach again to “grab” actin and pull towards its centre – the powerstrokeWhen calcium is depleted, when ATP is gone, the muscle fibre passively returns to its resting state
EXCITATIONSlide6
*CORRECTION*The 10 steps of the Sliding Filament Theory are actually NOT all classified as part of the SFT:
Message is sent down axon
Axon terminal releases Ach
Ach receptors on
sarcolemma
receive Ach
This stimulates the release of Calcium ions inside the muscle fibre (from
sarcoplasmic
reticulum)
Calcium binds to
troponin (on tropomyosin)Tropomyosin (wrapped around actin) swivels offThis shows myosin binding sitesMyosin binds through the energy of ATPMyosin attach, rotate, detach and attach again to “grab” actin and pull towards its centre – the powerstroke
When calcium is depleted, when ATP is gone, the muscle fibre passively returns to its resting state
CONTRACTIONSlide7
*CORRECTION*The 10 steps of the Sliding Filament Theory are actually NOT all classified as part of the SFT:
Message is sent down axon
Axon terminal releases Ach
Ach receptors on
sarcolemma
receive Ach
This stimulates the release of Calcium ions inside the muscle fibre (from
sarcoplasmic
reticulum)
Calcium binds to
troponin (on tropomyosin)Tropomyosin (wrapped around actin) swivels offThis shows myosin binding sitesMyosin binds through the energy of ATPMyosin attach, rotate, detach and attach again to “grab” actin and pull towards its centre – the powerstroke
When calcium is depleted, when ATP is gone, the muscle fibre passively returns to its resting state
SLIDING FILAMENT THEORYSlide8
EC Coupling + SFTIn essence, excitation-contraction coupling is the process by which a nerve impulse is translated into muscle contraction.
Sliding filament theory is the
mechanism
that explains how muscles contract.
On a unit test/assessment, I’ll ask for the steps of EC Coupling and Sliding Filament Theory of Muscle Contraction. These are the 10 steps we worked on memorizing and understanding!Slide9
Rigor MortisStiffening of the body beginning 3 to 4 hours after death
Deteriorating
sarcoplasmic
reticulum releases calcium
Calcium activates myosin-
actin
cross-bridging and muscle contracts, but can not relax.
Muscle relaxation requires ATP and ATP production is no longer produced after death
Fibers remain contracted until
myofilaments
decaySlide10
The Reflex ArcReflexes are an important part of all physical movement. Autonomic reflexes are mediated by the autonomic nervous system and usually involve the action
of smooth muscle, cardiac muscle and
glands.
Somatic reflexes
involve the stimulation of
skeletal muscles by
the somatic division of the nervous system. Slide11Slide12
The Reflex ArcStimulus causes sensory (afferent) neuron to generate a nerve impulse.
Impulse is carried to spinal cord where an interneuron interprets the signals and formulates response.
Motor neuron carries a response message from the spinal cord to the muscle (or organ).
The organ (or muscle, for example) carries out the response.Slide13
ProprioceptorsWe know the process (excitation-contraction coupling) and the mechanism (sliding filaments) by which a nerve impulse translates into a muscle contraction, but what exactly determines:
the
extent to which a muscle contracts,
the
moment when a muscle relaxes, and
how
muscles coordinate with other muscles and with other muscle groups in a particular area of the body?Slide14
ProprioceptorsThere are specialized receptors located within tendons, muscles, and joints. These are called proprioceptors
and
provide sensory information about:
The state of muscle contraction
The position of body limbs
The body’s posture
Balance Slide15
The Stretch ReflexMuscle spindles play an essential role in all physical movement. Spindles
run the length of a
muscle fibre and
send constant messages to the
spinal cord.
Muscle spindles detect changes in muscle
length and
responds to changes by sending a message to the spinal cord.
The
resulting muscle contraction allows for muscle to maintain proper
tension or tone, for example, in order to maintain our posture.Slide16
The Stretch ReflexSlide17
Tension ReflexGolgi tendon organs (GTOs) are sensory receptors that terminate where
tendons join
to muscle fibres. When a muscle stretches, so does the GTO receptor.
GTO
are responsible for detecting changes in muscle
tension.
Much
like the stretch reflex, GTO sends a message to the
CNS (central
nervous system) to help
protect the muscle from excessive tension that could injure the muscle, the joint, or both! GTOs continually provide feedback to the CNS so it’s likely they play an important role in the development of strength and force, since in order to able to exert greater force, it is necessary to overcome the action of the GTO itself!Slide18
Tension ReflexSlide19
Questions?Tomorrow we’ll begin looking at the major muscles in the body:How they are organizedOrigin/insertion points
Agonist and antagonist pairs
Types of contraction
How they are named