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Excitation-Contraction Coupling Excitation-Contraction Coupling

Excitation-Contraction Coupling - PowerPoint Presentation

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Excitation-Contraction Coupling - PPT Presentation

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

calcium muscle actin contraction muscle calcium contraction actin sliding fibre tropomyosin filament myosin binds theory attach atp reflex coupling excitation message muscles

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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. Slide11
Slide12

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