chapter 6 the muscular system. functions of muscular system slide 6.8 1.produce movement and...

Chapter 6The Muscular System

Functions of Muscular SystemFunctions of Muscular System

Slide 6.8

1. Produce movement and manipulate the environment

2. Maintain posture

3. Stabilize joints

4. Generate heat

The Muscular SystemThe Muscular System

Muscles are responsible for all types of body movement

Three basic muscle types are found in the body

Skeletal muscle

Cardiac muscle

Smooth muscle

Similarities of all Types of MusclesSimilarities of all Types of Muscles

Slide 6.2

Muscle cells are elongated (muscle cell = muscle fiber)

Contraction of muscles is due to the movement of microfilaments

All muscles share some terminology

Prefix myo refers to muscle

Prefix mys refers to muscle

Prefix sarco refers to flesh

Differences in the types of musclesDifferences in the types of muscles

Slide 6.1Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Skeletal Muscle CharacteristicsSkeletal Muscle Characteristics

Most are attached by tendons to bones

Cells are multinucleate

Striated – have visible banding

Voluntary – subject to conscious control

Cells are surrounded and bundled by connective tissue

Skeletal, striated, voluntary

Skeletal Muscle AttachmentsSkeletal Muscle Attachments

AponeurosesTendon

Tendon – cord-like structure

Aponeuroses – sheet-like structure

Sites of muscle attachment Bones

Cartilages

Connective tissue coverings

Cardiac Muscle CharacteristicsCardiac Muscle Characteristics

Has striations

Usually has a single nucleus

Joined to another muscle cell at an intercalated disc

Involuntary; the heart has a pacemaker

Found only in the heart

Figure 6.2b

Cardiac, striated, involuntary

Smooth Muscle CharacteristicsSmooth Muscle Characteristics

Has no striations

Spindle-shaped cells

Single nucleus

Involuntary – no conscious control

Found mainly in the walls of hollow organs

Arranged in layers

2 layers Figure 6.2a

Smooth, no striations, involuntary

Microscopic Anatomy of Skeletal MuscleMicroscopic Anatomy of Skeletal Muscle

Cells are multinucleate

Nuclei are just beneath the sarcolemma

Sarcolemma (organelle) – specialized plasma membrane

Figure 6.3a


Sarcoplasmic reticulum (organelle)

Specialized smooth ER that surrounds all myofibrils

Stores Ca ions to be able to release them on demand

Figure 6.3a


Myofibril (organelle)

Bundles of myofilaments

Myofibrils are aligned to give distrinct bands

I band = light band

A band = dark band

Figure 6.3b

Microscopic Anatomy of Skeletal MuscleMicroscopic Anatomy of Skeletal Muscle Sarcomere

Chains of contractile units in myofibrils

Two types of myofilaments

Thick = myosin

Thin = actin

Figure 6.3b

Microscopic Anatomy of Skeletal MuscleMicroscopic Anatomy of Skeletal Muscle Thick filaments = myosin filaments

Composed of the protein myosin

Figure 6.3c


Thin filaments = actin filaments

Anchored to the Z disc

Composed of the protein actin

Figure 6.3c


Myosin filaments have heads (extensions, or cross bridges)

Myosin heads link the thick and thin during contraction

Myosin and actin overlap somewhat

Figure 6.3d


Thick (myosin) and thin (actin) filaments produce the striations in skeletal muscle

Figure 6.3d

Organizational levels of Skeletal MuscleOrganizational levels of Skeletal Muscle

Organ – the muscle (biceps)

Fiber – a muscle cell

Myofibril – organelle composed of sarcomeres and myofilaments

Sarcomeres – unit of myofibril

Myofilament – actin and myosin

Skeletal Muscle Cell Skeletal Muscle Cell

Nucleus – control center

Sarcolemma – plasma membrane

Sarcoplasm – cytoplasm


Sarcoplasmic reticulum – storage of calcium ions to be released when stimulated by an impulse

T-tubules – surround the myofibrils and assist in delivering ions


Mitochondria (lots) – provide energy and ATP

Myofibril – composed of thick and thin filaments and many sarcomeres

Muscle ContractionMuscle Contraction

From nerve stimulus to From nerve stimulus to sarcomere contractionsarcomere contraction

Nerve Stimulus to MusclesNerve Stimulus to Muscles

1. Skeletal muscles must be stimulated by a nerve to contract

Motor unit is composed of:

One neuron

All muscle cells stimulated by that neuron

One nerve cell branches into axonal terminals

Figure 6.4a

Nerve Stimulus to MusclesNerve Stimulus to Muscles Axonal terminals form

junctions with sarcoplasm called neuromuscular junctions

Nerve and muscle do not make contact there is a gap

Synaptic cleft – gap between nerve and muscle

Gap is filled with interstitial fluid

Figure 6.5b


2. Action potentials are sent down the neuron in response to a stimuli

Because the two cells do not touch, the action potential cannot ‘jump the gap’

Figure 6.5b


3. The neuron communicates indirectly with the muscle cell by releasing a neurotransmitter

The neurotransmitter for skeletal muscle is acetylcholine (ACh) and it is stored in the axonal terminal

4. Sarcolemma has receptors for Ach and causes an action potential in muscle cell

Transmission of Nerve Impulse Wrap-upTransmission of Nerve Impulse Wrap-up

1. How does the neurotransmitter produced by the motor neuron cause the skeletal muscle to contract?

2. What is the neurotransmitter in muscle cells?

3. What is the synaptic cleft?4. What makes up a motor unit?5. List the steps of transmission of a nerve

impulse.

The Sliding Filament Theory of Muscle ContractionThe Sliding Filament Theory of Muscle Contraction

Slide 6.17a

Put your right palm on the back of your left hand.

Now slide your right palm toward your left elbow

What happened to the distance between your elbows?

This is how muscle contraction works!

Figure 6.7


Slide 6.17a

Activation by nerve causes calcium to be released by the sarcoplasm reticulum

Calcium binds to actin and exposes myosin binding sites where the myosin heads attach and form a crossbridge

ATP is used as the energy source

Figure 6.7


Slide 6.17b

The thin filament slides past the thick filament towards the center as each myosin head attaches and detaches

Distance between Z discs shortens as actin moves toward the center

The result is that the entire muscle is shortened (contracted)

Figure 6.7


Slide 6.17b

Length of the A band (myosin and actin) stays the same

Length of the H zone (only thick filaments) shortens

Length of the I band (thin filaments) shortens

http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter42/animations.html#

Figure 6.7

http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter42/animations.html




The Sliding Filament TheoryThe Sliding Filament Theory

Go to figure 6.8 in your book and summarize the steps for the sliding filament theory and explain how a muscle contracts

Transmission of Nerve Impulse to Muscle Transmission of Nerve Impulse to Muscle ContractionContraction1. Nerve impulse sent and received by axonal terminal

2. Neurotransmitter (acetylcholine) is released upon arrival of nerve impulse

3. Diffuses across synaptic cleft and attaches to receptors on the sarcolemma

4. Triggers an action potential of the muscle cell

5. The action potential causes the SR to release calcium ions

6. The calcium ions bind with the actin filaments to open the binding site for myosin

7. Myosin heads bind to them with the help of ATP

8. The cell contracts

chapter 6 the muscular system. functions of muscular system slide 6.8 1.produce movement and...

Documents

skeletal muscle figure

involuntary slide

b slide

c slide

d slide

flesh slide

heat slide

types of muscles slide