Muscle Rules! HBS – 4.2.1 - PowerPoint Presentation

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Muscle Rules!HBS – 4.2.1

Drill: Please grab your skeleton and sit with your partner! Have your lab manual out too!

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Types of MuscleThere are 3 types of muscle in our bodies

SkeletalSmoothCardiacEach has different characteristics that we will look at today.

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Skeletal Muscle

Voluntary – we control the movementStriated – looks like long fibers with striations at the Z-zonesLinked to bones by tendonsFunction – to help us move / move our bones

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Smooth Muscle

Involuntary Action – controlled by our CNSNon-striatedFound in arteries, veins, intestines, etc.Function : Maintain organ dimensions – stretch and recoil

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Cardiac Muscle

InvoluntaryStriated – but fibers tend to be branched which is unlike skeletal muscle.Found in walls of the heartFunction : To pump the heart!!!!Highly resistant to fatigue w/ lots of mitochondria

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Let’s Start By Building a Muscle from Spaghetti!

Pick up one piece of spaghetti. Each piece of spaghetti will represent one skeletal muscle cell or fiberEach muscle fiber is enclosed by a delicate membrane called the

endomysium

.

(For the purposes of this activity, the yellow outer coating of the spaghetti represents this membrane. Each fiber contains many myofibrils.)

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Spaghetti Muscle Cont’d

Pick up a handful of spaghetti. This bundle of fibers represents a

fascicle

.

Each fascicle, however, is covered by a membrane called the

perimysium

.

Place the bunch of spaghetti on the end of a piece of plastic wrap.

Roll the spaghetti up in the plastic used to represent the perimysium.

Hold up the completed fascicle. Pull the ends taut, and notice that this tissue has little to no bumps. These ends represent dense regular connective

tissue.

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Spaghetti Muscle Cont’d

Fascicles group together to form a skeletal muscle.Combine your fascicle w/ three other pairs’ to form a whole muscle. These fascicles are bound together by an even tougher outer membrane called the epimysium.

Wrap the combined fascicles in another piece of plastic wrap.

This layer of wrap will represent the

epimysium

.

Twist the plastic wrap on each end of the completed muscle.

At the ends of the muscle, the

epimysia

blend together to form tendons, cordlike structures that attach muscle to bone, cartilage or other connective tissue.

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Step 1Locate the ventral side and use a pencil to place a dot on the lateral and medial side of the radial groove (about halfway up the humerus).

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Step 2Locate the ulna just below the fold of the elbow. Help the students see the hollowed out area in the

antecubital region. Place a pencil dot above this area.

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Step 2 Cont’d - Rule 1

These dots each represent an attachment point for a muscle. Note that there are at least two attachments (in this case three) and the muscle will cross a joint at the elbow. This leads us to Muscle Rule #1: Muscles must have at least two attachments and must

cross at least one joint.

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Step 3 – Brachialis Muscle

Using terra cotta clay, form two balls about the diameter of a nickel.Rolling the clay between the tabletop and a palm, roll each ball into a long carrot. The total length of the carrots should stretch from the humeral attachment to the ulnar attachment.

Bring the fat part of the carrots together, leaving the tops free

(

rabbit ears

).

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Step 3 – Brachialis Muscle Cont’D

Attach the two free ends to the humeral attachments. Place the combined fat end across the elbow and attach the end to the ulnar attachment. Pinch off any extra clay.

Use

your thumb to

press

the

clay muscle onto

the

arm.

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Step 4 – Rule 2

Using your left thumb to represent the humeral attachments and your left middle finger to represent the ulnar attachment, place the left hand on the right arm where the attachments would be.Make

sure to cross the joint.

Pull your

forearm towards

your heart

and

watch the position of

your fingers. You should notice that your

index finger and thumb are closer together than when you started.

This lead to

rule 2:

Muscles always “pull” and get shorter.

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Step 5 – Rule 3

Repeat the motion and identify which attachment is “pulling” or moving closer to the other attachment. The attachment that moves is known as the

insertion

of the muscle.

The

insertion is usually the distal attachment.

The

attachment that does not move and pulls the other attachment toward it is referred to as the

origin. The origin is usually the proximal attachment.

This leads to Rule 3:The attachment that moves is known as the insertion and the attachment that remains stationary is known as the origin.

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Step 6

Extend your arms out in front of their bodies. Notice this angle is 180°. Show the movement again of

the muscle

you

have

just built

.

This

time pay attention to what happens to this angle when the muscle shortens.

Notice that the angle decreases. Do you remember what we call motion at a joint that decreases the angle between articulating

bones?

Flexion

and thus a muscle such as this is referred to as a

flexor

.

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Step 7 – Rule 4

Flex your arms one more time, but stop at the end of the movement.If muscles only pull, then how can the arm be straightened?What do we call motion at a joint that increases the angle between articulating bones?Extension and thus a muscle that controls this movement is referred to as an

extensor

.

Muscles

that decrease the angle between ventral surfaces of the body are known as flexors. Muscles that increase the angle between ventral surfaces of the body are known as extensors

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Step 8

Place a pencil dot halfway up the dorsal side of the humerus. Place another dot just distal of the elbow onto the ulna

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Step 9 –triceps medial head

Using terra cotta clay, form a ball the diameter of a nickel. Roll the ball into an even tube. Attach the ends of the clay tube to dots on the humerus and on the ulna. Since the back of the humerus is flat, the muscle shapes to the bone and is also flat.

Use your

thumbs to flatten

the clay

.

Remove

any clay that

makes its way

to the ventral side.

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Step 9 Cont’d

Act out the action of this muscle. With the right arm in the flexed position, place the left thumb on the back of the humerus and the left index finger on the back of the elbow. “Pull” with your index fingers and the angle should increase to 180°.

Repeat

the motion and

think of Rules

2, 3 and 4.

Since

the angle in this motion increases, the muscle is an extensor.

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The TricepsOrigin = proximal half of dorsal humerus

Insertion = distal of elbow on the ulnaAction = extends elbow

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Flexors and Extensors

Flexors are on the ventral side of the body and extensors are located dorsally. “For smooth movements to occur, can both extensors and flexors be contracting at the same time?” When the flexors are pulling, the extensors are relaxing.

This brings us to

Rule #5:

Muscles

work in opposing pairs

.

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Rule # 6

Muscle fibers point to the attachments and show the direction of pull.

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Naming Muscles

Each muscle is given a Latin name based on one or more of its featuresTake a look at the following muscle names and brainstorm what you can tell about these muscles simply by their namesTrapezius

and Rhomboid minor

Gluteus

maximus

and Gluteus

minimus

Frontalis

and Temporalis

Orbicularis

Oculi

and Transverse

abdominis

Flexor

Carpi

Ulnaris

and Extensor

digitorum

longus

SternoCleidomastoid

and

Brachioradialis

Biceps

Brachii

and Triceps

Brachii