Chapter 9 the muscular system > Skeletal muscle tissue

Recognize definitions of vocabulary words

• Muscle fiber- elongated cells each capable of contracting along its longitudinal axis

Identify the 3 types of muscle tissue

• Skeletal Muscle: Attached to bones

• Cardiac Muscle: Found in the heart

• Smooth Muscle: Found in organs

Know what substances are moved by the contraction of the 3 types of muscle tissue

• Skeletal Muscle: Moves bones.

• Cardiac Muscle: Pumps blood.

• Smooth Muscle: Moves food, air, and bodily fluids.

Be able to list the 5 functions of skeletal muscle

1. Produces skeletal movement

2. Maintain posture and body position

3. Supports soft tissues

4. Guards entrances and exits

5. Maintain body temperature

Be able to identify by diagram the 3 wrappings of skeletal muscle tissue

• Epimysium: Outer layer around the entire muscle.

• Perimysium: Surrounds bundles of muscle fibers (fascicles).

• Endomysium: Surrounds individual muscle fibers

List the levels of organization of a skeletal muscle

1. Muscle fibers are composed of myofibrils and muscle fibers are covered by the endomysium

2. Then bundles of muscle fibers form a fascicle and are surrounded by the perimysium

3. When you bundle the fascicles and blood vessels together and surround that with the epimysium it forms the whole muscle

Identify the location and function of satellite cells

• Location: Outside of muscle fibers.

• Function: Repair and regenerate muscle tissue.

Identify the location and the function of transfers Tubules

Deep depressions in the sarcolemal surface forms a network of narrow transverse tubules that extend into the sacoplasm that helped distribute the electrical signal to contract throughout the muscle fiber

List the differences between typical cells and muscle fibers

Skeletal muscle fibres are very large in some cases, muscle fibers are as long as the entire muscle

Skeletal muscle fibers are multi nuclear

Differentiate between Actin and Myosin filaments

Thin filaments are actin filaments while thick filaments are myosin filaments

Describe the function of Troponin and Tropomyosin In muscle contraction

Tropomyosin mlecules form a long chain that covers the active sites, thus preventing actin-myosin interaction

Troponin holds tropomyosin in place

Describe the function of calcium in muscle contraction

• When calcium ion concentration in the sarcoplasm rises, the troponin molecules change position, moving the tropomyosin molecules and exposing active sites allowing cross-bridges to be farmed; contraction begins

Using a labeled diagram of a sarcomere Describe what occurs to the different regions during contraction

• M-line: Stays the same

• Z-lines: Moves closer together

• Zone of Overlap: Gets Larger

• H-band: Got smaller

• I-band: Got smaller

• A-band: Stays the same

Describe the sliding filament mechanism of a muscle contraction

• Myosin heads of thick-fillamesnts bind to active sites on thin fillaments (crossbridge formation)

• Myosin head pivot tword the M-line pulling the actin filament toward the center of the sarcomere

• Cross-bridge detaches and returns to normal position

• Cycle is repeated

Draw and label a neuro muscular Junction

• Each skeletal muscle fiber is controlled by a motor neuron at a single neuro muscular junction midway along its length

• The expanded tip of an axonal branch is the synaptic knob

• The narrow space that exists between the synaptic knob and the sarcolemma is the synaptic cleft of the synapse

• Within the cytoplasm of the synaptic knob are tiny, sac-like structures that are filled with neurotransmitter these are synaptic vesicles

• The neurotransmitter within the vesicles is acetylcholine (ACH)

• The synaptic cleft contains the enzyme acetylcholinesterase which breaks down acetylcholine to end contraction (Diffusion and reuptake from synaptic knobs)

Using the diagram describe how a neuro muscular Junction functions

The electrical impulse passing down the neuron arrives at the synaptic knob, causing vesicles to burst. When the synaptic vesicles burst, neurotransmitter (ACH) is released into the synaptic cleft. ACH crosses the synapse and binds to receptors on the sarcolemma (this causesal a local transmembrane potential). This continues until acetylcholinesterase (ACHE) removes the bound ACH.

Identify the 2 factors on which the amount of tension a skeletal muscle produces when stimulated by a motor unit

• Frequency of stimulation.

• Number of motor units recruited.

Describe why muscle tone is important

To stabilize the position of the bones and joints to maintain balence and posture

Contrast muscle Atrophy with muscle Hypertrophy

• Atrophy: The net enlargement of muscles that have been stimulated to produce near-maximal tension

• Hypertrophy: The result of a skeletal muscle not being stimulated by a motor neuron on a regular basis and therefore losing muscle tone and mass; the muscle becomes flaccid and the muscle fibers become smaller and weaker thus reducing the muscle size, tone, and power

Contrast fast twitch muscle fibers with slow twitch muscle fibers

• Fast: larger in diamete,r have large energy reserve, Relatively few mitochindria, can contract in 0.01 seconds or less following stimulation, most of skeletal muscle fibers in the body are fast fibers, fast fibers produce powerful contractions; however, they use enormus amounts of ATP and fatigue easily. Example Sprinter

• Slow Twitch: Have a diameter about half that of fast fibers, contain a relatively larger number of mitochondria than fast fibers, mitochondria of slow fibers are able to contribute a greater amount of ATP than fast muscle fibers, Are specialized to contract for extended periods of time, contain an extensive capillary supply which dramatically increases oxygen supply (myoglabin binds to the oxygen molecules which allows the slow fibers to contain oxygen reserves that can be mobilized during a contraction.) Example Marathon runners

Explain in relation to type of muscle fibers why exercise is important

Resistance exercise will increase the number of myofibrils in the muscle fibers making them bigger and stronger which will help the fibers be stronger. Endurance exercise will trigger an increase in blood supply to the muscle fibers allowing the slow twitch to work for longer since they actively use glucose and oxygen in the blood for ATP production.

List 5 effects of aging on the muscular system

• Skeletal muscle fibers become less in diameter

• Skeletal muscles become smaller and less elastic

• Tolerance for exercise decreases

• Ability to recover from muscular injuries decreases

• There is a rate of decline in muscular performance in all individuals