List AND describe the functions of skeletal muscles

Movement
Posture
Supports soft tissue
Guards entrances and exits
Provides heat/maintains body temperature
Storage of minerals

List AND describe the characteristics of skeletal muscle

Responsiveness (excitability)- to chemical signals, stretch and electrical change across the plasma membrane
Conductivity- local electrical change triggers a wave of excitation that travels along muscle fiber
Contractility-shortens when stimulated
Extensibility- capable of being stretched
Elasticity- returns to its original resting length after being stretched.

What are two other names for a muscle fiber?

Myofiber
Myocyte

Describe the number and location of nuclei in a myofiber

There are many nuclei
Location: Nuclei are just below the sarcolemma-specialized cell membrane

Muscle cells are packed full of which type of protein filament?

Actin
Myosin

Make sure you understand the difference between a myofiber and a myofibril!

Myofiber= muscle fiber= myocte-single muscle cell. Their cytoplasm is packed full of myofibrils.

Myofibril- are bundle of protien filaments (actin and myosin) that cause contraction.

What is another name for the muscle cytoplasm?

Sarcoplasm

What is another name for the plasma membrane of a myofiber?

Sarcolemma= cell membrane

Describe the location of the T tubules, sarcoplasmic reticulum, and terminal cisternae. What is the function of each of these structures?

Transverse tubules (T-tubules)- circles around myofibrils. Carry electric current to cell interior. Transmits signal to contract.

Describe the location of the sarcoplasmic reticulum (SR) and the function.

Modified smooth ER

Network arond each myofibril

Stores calcium

Describe the location of the terminal cisternae and the function.

Part of the network around the myofibril, the end sacs. The terminal cisternea and the SR store calcium

What is a “triad” referring to?

1 tubule and 2 tubule cisternea

Label the connective tissue wrappings of a skeletal muscle.

What is an aponeurosis? Where are some regions in the human body might you find one? How does an aponeurosis differ from a tendon?

Aponeurosis- sheet-like structure

You can find them at sites of muscle attachement

Aponeurosis is a sheet-like structure and

Tendon is a cord-like structure

What is the name given to the contractile unit of muscle?

Sarcomere

What protein is the thin filament made of?

Actin

What protein is the thick filament made of?

Myosin

What exactly is a cross bridge?

The head aka extensions or crossbridges of Myosin filaments

What is the function of a Titin protein? What two regions of the sarcomere does it connect?

The titin protein is responsible for passive electricity of the muscles. It connects at the Z line and M line of the muscle fiber.

Label the following regions of a sarcomere:

1. Z - Line
2. I –Band
3. A – Band
4. H – Zone
5. M – Line
6. Thin filament
7. Thick filament
8. Dark Band
9. Light Band

• The thick filaments produce the dark A band.
• The thin filaments extend in each direction from the Z line.
• Where they do not overlap the thick filaments, they create the light I band.
• The H zone is that portion of the A band where the thick and thin filaments do not overlap.
• The entire array of thick and thin filaments between the Z lines is called a sarcomere

Which band of a sarcomere contains only actin?

I band

Which band of a sarcomere has actin and myosin?

A band

Which zone of a sarcomere has only “bare” myosin?

H zone

Which region of a myosin molecule attaches to actin?

Head/Cross bridge

Describe AND draw the relationship between the following proteins in a sarcomere during muscle contraction AND muscle relaxation:

1. Actin
2. Myosin
3. Myosin binding site
4. Myosin head
5. Troponin
6. Tropomyosin
7. Calcium (Ca)
8. ATP and ADP

What happens to the sizes of the following bands/regions of sarcomere during contraction AND relaxation?

1. Distance between Z – Lines
2. Size of I – Band
3. Size of A – Band
4. Size of H – Zone
5. Length of individual actin and myosin filaments

Distance between the Z-lines stays the same

Size of I-Band becomes narrow (shortens) during contraction at maximum width at relaxation

Size of A-Band remains unchanged

Size of H-Zone Disappears almost (shortens) during contraction and at maximum width at relaxation

Explain, in detail, the concept of a motor unit. How would the arrangement of a motor unit differ for fine control vs. strength control?

A motor neuron and the muscle fibers it innervates

*dispersed throughout the muscle
*when contract together causes weak contraction over wide area
*provides ability to sustain long-term contraction as motor units take turns resting (postural control)
1.) Fine control
small motor units contain as few as 20 muscle fibers pernerve fiber
i.e. eye muscles
2.) Strength control
*gastrocnemius muscle has 1000 fibers per nerve fiber (recruitment)

Describe, in detail, all of the components of a neuromuscular junction (NMJ) including:

1. Synaptic knob
2. Junctional folds
3. Synaptic cleft
4. Basal lamina
5. Acetylcholine
6. Acetylcholine receptors
7. Aceytlcholinesterase

a. synaptic knob is the swollen end of the nerve fiberb.

Junctional folds: located on the sarcolemma, functions to increase surface area for ACh receptors and contains acetylcholinesterase to break down ACh and relax musclesc.

Synaptic cleft: tiny gap between nerve and muscle cell; function is a space for reactions to occurs

Basal Lamina: thin layer of glycoprotein and collagen all over muscle fibers

Acetylcholine: chemical component released from neuron to produce a stimulusf.

Acetylcholine receptors sense the ACh being released into the synaptic gap and open channels to allow chemicals in for the muscle to contract.

Acetylcholinesterase breaks down the ACh causing the muscle to relax

Briefly summarize the four actions necessary for muscle contraction and relaxation.

1.Excitation - action potentials in the nerve lead to formation of action potentials in a muscle fiber
2. Excitation-Contraction Coupling - action potentials on the sarcolemma activate myofilaments.
3. Contraction - shortening of a muscle fiber or at least the formation of tension.
4. Relaxation - return of a muscle fiber to its resting length

Diagram AND explain in words ALL of the steps involved in muscle contraction AND relaxation. Yes, this will take you some time. You should know by now how you learn best, so choose a method that works for you. The more times you go through this and the more detail you include, the better off you will be!

Study Book and Slides

Discuss HOW some of the neuromuscular toxins covered in class affect the NMJ.

Some of the toxins are cholinesterase which prevent acetylcholinesterase from degrading ACh, causes spastic paralysis and possible suffocation.Flaccid paralysis can occur when curare competes with ACh preventing a motor neuron from producing a stimulus

Discuss HOW myasthenia gravis leads to progressive weakness

It is an autoimmune disease that binds to ACh receptors preventing ACh from stimulating a muscle and makes body less and less sensitive to ACh.

Explain, in detail, why an individual becomes rigid soon after death, but then days later, becomes floppy. Make sure to include the roles of ATP and calcium in your explanation.

Occurs because muscle cells have a massive release of Ca2+ from sarcolemma causing muscles to contract and stiffen, muscles become floppy again because there is no more ATP being produced to reset the sarcolemma and proteins start breaking down.

Explain the phenomenon of “all or none” when describing muscle contraction.

In a muscle fiber in order for contraction all of the muscle fibers must be stimulated or no contraction will take place**All muscle fibers dont fire at once, one goes, then another and another and so on till all fibers are contracting**

What does recruitment mean in terms of muscle contraction?

As muscle fibers are stimulated more are "recruited" and stimulated

What are the three phases of twitch AND what is happening on the molecular and cellular level during each of these phases?

1. Latent period before contraction: action potential moves through sarcolemma causing Ca2+ to be released

2. Contraction phase: calcium ions bind, tension builds to peak

3. Relaxation phase: Ca2+ levels fall, active sites are covered, tension falls to resting levels

Compare and contrast unfused and fused tetanus. Make sure to mention “treppe” and wave summation in your answer.

fused tetanus, muscle contractions are short and close together; doesnt allow for muscles to relax inbetween contractions, the treppe increases, treppe=increased stimulation.Unfused tetanus, muscle contractions are further apart, allows muscles to relax between contractions

Compare and contrast isotonic and isometric muscle contraction. Give some examples of each.

Isometric muscle contraction is when a muscle develops tension without changing length, important in posture function and joint stabilization. Isotonic muscle contraction is when muscle fiber tension increases and muscle fibers shorten and lengthen, lifting weights.

What is the difference between a concentric and eccentric isotonic contraction?

concentric is when tension exceeds resistance and muscles shorten.eccentric is when resistance exceeds tension and muscle lengthens.

Explain what is meant by the statement that, “A muscle is never entirely relaxed.” Yes, this question is asking you to talk about muscle tone.

A muscle is never entirely relaxed, some fibers react at different times to provide muscle tone, normal tension of a muscle at rest= muscle tone.

Review the processes of anaerobic and aerobic respiration

Refer to slides and book

Compare and contrast, in detail, what is occurring on a molecular and cellular level for immediate, short term, and long term energy needs of a muscle.

long: Aerobic respiration needed for prolonged exercise

36 ATPs/glucose molecule

After 40 seconds of exercise, respiratory and cardiovascular systems must deliver enough oxygen for aerobic respiration

oxygen consumption rate increases for first 3-4 minutes and then levels off to a steady state

Limits are set by depletion of glycogen and blood glucose, loss of fluid and electrolytes

What is creatine phosphate in terms of a supplement? Specifically, who is it going to benefit? Why?

It is a molecule that produces more ATP, the more energy produced the more work a muscle fiber can do.

Describe on a molecular and cellular level what is occurring when a muscle becomes fatigued.

ATP synthesis declines as glycogen is consumed

sodium-potassium pumps fail to maintain membrane potential and excitability

lactic acid inhibits enzyme function

accumulation of extracellular K+ hyperpolarizes the cellmotor nerve fibers use up their acetylcholine

What types of things would an endurance athlete be concerned with? Explain!

Oxygen uptake, for aerobic respiration, and nutrient availability for energy production and electrolyte balance to prevent muscle fatigue

Describe what is occurring when a muscle goes into “oxygen debt.” Make sure to explain EPOC in your response.

EPOC stands for excess postexercies oxygen consumption, this is the heavy breathing occurring when you exercise, its purpose is to replenish phosphagen system, reconvert lactic acid, and to serve the elevated metabolic rate.

Compare and contrast slow twitch and fast twitch muscle fibers.

-Slow oxidative fibers, Smaller diamter, more mitochondria, myoglobin and capillaries,adapted for aerobic respiration and resistant to fatigue, Slow to contract, soleus and postural muscles of the back-Have large diameter, large glycogen reserves, few mitochondria, Fast glycolytic,rich in enzymes for phosphagen and glycogen lactic acid systems sarcoplasmic reticulum releases Ca quickly, contractions are quicker, fatigue quick

How exactly do strength workouts increase muscle size?

stimulates cell enlargement due to synthesis of more myofilamentsHypertrophy (increased muscle size) vs. increase in number of muscle cells

What is DOMS? What exactly causes it?

Delayed Onset Muscle Soreness. This is caused by a build up of lactic acid in the muscle tissue from strenuous activity.

How does endurance training prepare an athlete for an Ironman triathlon? Explain what is going on at the molecular and cellular level!

Refer to notes

Compare and contrast skeletal muscle, cardiac muscle, and smooth muscle making sure to include the following in your comparison. This question may be more appropriate for the lab portion of this course:

1. Does it have one nucleus or is it multinucleated?
2. What is the location of nucleus (central vs. peripheral)?
3. Striated or non-striated?
4. Voluntary or involuntary?
5. Can it divide?
6. Intercalated discs?
7. Major function?
8. Where in the human body is it found?

Refer to notes