Muscles and Movement

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Nov 10, 2013 (3 years and 7 months ago)

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HL Papers 1 and 2

Muscles and Movement

Muscles and Movement


Responding to stimuli is one of the six life
functions


Movement is responding to stimuli



Movement from point A to point B is called
locomotion



Done by the coordination of the nervous system
with the muscles and bones


Muscles and Movement


You need:



Nerves (went over previous topic)


Carry impulses to and from the brain to co
-
ordinate muscular
activity


Motor neuron impulses stimulate the muscles to contract


Nerve impulses control timing and speed of muscular
contraction



Muscles


Contain receptors that send information via sensory neurons to
the brain about the position of the muscle


Contract to bring movement to the joint


Work in muscles pairs on each side of a joint


Muscles and Movement


Muscles have a belly (
gaster
) and a tendon



Belly
-

fleshy portion of the muscle
between the tendons.



Tendon
-

a white fibrous cord of dense,
regularly arranged connective tissue that
attaches muscle to bone. They have the
tensile strength of steel.


Muscles and Movement


Belly and
Tendon



Muscles and Movement


Each muscle has an origin and an insertion.



Insertion

is the attachment of the muscle
tendon to the moveable bone



Origin

is the attachment of the other
muscle tendon to the stationary bone.


Muscles and Movement


Bones



Bones meet at a joint and act as levers


Different types to joints between bones control the range of movement


Provide rigid anchorage for muscles through tendons


Form blood cells in the bone marrow


Provide a hard framework to support the body


Allow protection of vulnerable softer tissue and organs


Allow for the storage of minerals, especially calcium and phosphorus


Connected by
ligaments



Ligaments



fibrous tissue


run from one bone to another, across joints


connect bones together, and give the joint strength.


Muscles and Movement


Bones and
Ligaments


Muscles and Movement
-

Joints


Consist of two or more bones, connected by ligaments
and muscles, connected to bones by tendons, to facilitate
movement.



Joints contain the following:



Cartilage


smooth, strong covering on articulating
surfaces of a joint



Synovial Fluid



lubricates articulating surfaces of
cartilage; acts like a shock absorber. Contains nutrients
and Oxygen for the cartilage.


Muscles and Movement
-

Joints


Spongy Bone



end of bones that are light
and strong.




Band Ligaments



tough elastic structures
holding bones of a joint together.




Capsular Ligaments



encloses joint to
protect it.


Example


Elbow Joint


Movement


A comparison


The knee is similar to the elbow.


both are hinge joints


Freely movable are also called
diarthrotic

joints.


The hip is also a
diarthrotic

joint, but is a
ball and socket joint.


Movement


A comparison

Hip Joint

Knee Joint



Muscle Structure


Striated Muscle


Muscles are made up of various strands, like rope



A skeletal muscle is made up of bundles muscle
fibers
, or muscle
cells.




Each muscle
fiber

is surrounded by a
sarcolemma
, the muscle
fiber’s

cell membrane.




Each muscle
fibers

contains many
myofibrils




The cytoplasm, called
sarcoplasm
, contains mitochondria
packed between the myofibrils. In between the myofibrils is a
transverse tubular endoplasmic reticulum, called the
sarcoplasmic

reticulum.


Muscle Structure


Striated Muscle


In the myofibrils, there are two
protein

myofilaments

called
myosin

and
actin
.



The
myosin

is the
thick filament
, that appears
darker
.



The
actin

is the
thin filament
, that appears
light
.



The stripes are caused by the alternating light and dark
bands.

Muscle Structure


Striated Muscle


Structure and Contraction of Skeletal
Muscle


Sarcomere



section between the z


lines



Actin

filaments

are
held together by transverse bands
called Z line
.




Where the
actin

partially overlaps the myosin filaments
and from end to end of the myosin filament
, is called the
A band




The
area where only myosin is seen

is called the
H band
or zone
. This is between the two Z lines.


Structure and Contraction of Skeletal
Muscle


Across the
fibers

there are
transverse tubules, or T


tubules



Tubules touch the
sarcolemma

and associated with vesicles
which are part of the
sarcoplasmic

reticulum


A T
-
tubule with a pair of vesicles is called a triad.



The vesicles are important.


Regulate the movement of calcium ions to and from the
sarcoplasm
. The Ca
+2

concentration determines the activity of
ATPase


Structure and Contraction of Skeletal
Muscle


Structure and Contraction of Skeletal
Muscle



Sliding Filament Theory


The
actin

slides across the myosin, powered by ATP



On the
actin

filament are binding sites for the heads of the
myosin



Actin

filaments

contain
actin

as well as
tropomyosin

and
troponin
.


Tropomyosin

forms two strands which wind around the
actin

filament, covering the binding site.



The
tropomyosin

is held in place by the
troponin
. This is how
the
actin

filament remains at rest.



Sliding Filament Theory


The thick filaments are composed of
myosin molecules



Each has a
bulbous head



The head protrudes from the length of the myosin filament.



The head, binds to the site on the
actin

filament.




This is what causes movement of the filaments, and eventually
the movement of the whole muscle.


Actin
, Myosin,
Tropomyosin
, and
Troponin


Contraction


Sliding Filament


4 Steps


1. The myofibril is stimulated to contract by the arrival of an
action potential


Triggers the release of calcium ions from the
sarcoplasmic

reticulum, to surround the
actin

molecules.


The calcium ions react with the
troponin
.


When the
troponin

is activated, it triggers the removal of the
blocking molecule,
tropomyosin
.


The binding sites are now exposed.


Contraction


Sliding Filament

2. Each bulbous head has an ADP and Phosphate group attached
to it (called a charged bulbous head).


It reacts with a binding site on the
actin

molecule beside it.
The phosphate group detaches.


This is called Attachment


3.
The ADP molecule is then released from the head


This is a trigger for the rowing movement of the head.



The head tilts 45
o

and pushes the
actin

filament along.



This step is called the power stroke and the
myofibril contracts.




Contraction


Sliding Filament

4. A molecule of ATP binds to the head.


The protein,
ATPase
, catalyses the hydrolysis of ATP.


The result is ADP and Phosphate is attached to the bulbous
head


It is said to be charged again


The charged head detaches from the binding site and
straightens.


With more ATP and calcium, the head attaches again, step 2,
to shorten more. Another power stroke is
acheived
.


When no more impulses arrive, calcium ions are moved back
into the vesicles of the
sarcoplasmic

reticulum binding sites
are covered by the
tropomysin

and the muscle relaxes.



Exposure of Binding Sites


Sliding Filament Theory (
Animation
)


Extensions


Muscle Disorders


Multiple Sclerosis




Muscular Dystrophy