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Human Anatomy and Physiology, Chapter 6
Muscles and Muscle Tissue
TO BE DONE INDIVIDUALLY ON SEPARATE PAPER
INTRODUCTION
1. What is the origin of the word muscle?
From the Latin mus meaning mouse
Looked like “little mice” running under the skin
OVERVIEW OF MUSCLE TISSUES
Muscle Types
Introduction
2. Contrast the body location, cell shape and appearance, and regulation, speed
and rythmicity of contraction of the three types of muscle tissue.
Skeletal
Cardiac
Smooth
Location
Attached to bones Heart
Hollow organs, vessels,
airway
Cell
Multinucleated,
Uninucleate,
Uninucleate, non-striated
shape/appearance striated
branched, striated
Regulation
Voluntary
Involuntary
Involuntary
Cell-type and use
Speed
Slow
Very slow
specific
Rhythmicity
No
Yes
Some
Skeletal Muscle
3. List several functions of the connective tissue covering around and within
muscle.
Support, protect, transmit force, provide access, insulate(?)
Muscle Functions
4. List four important functions of muscle tissue.
Producing Movement
Maintaining Posture
Stabilizing Joints
Generating Heat
MICROSCOPIC ANATOMY OF SKELETAL MUSCLE
5. Sketch a typical skeletal muscle cell and labels these parts: sarcolemma, nuclei, sarcomere,
myofibril, I band, and A band.
6. Why do muscle fibers appear striated?
Contain many myofibrils with their dark A bands and light I bands aligned
7. Define the A band and I band in terms of thick and thin filaments.
A band = thick filaments with thin filaments overlapping at each end
I band = thin filaments
8. Contrast myosin and actin.
Myosin is in the thick, actin in the thin
Myosin heads stick out and pull the thin filaments to the center of the sarcomere during
contraction
SKELETAL MUSCLE ACTIVITY
Stimulation and Contraction of Single Skeletal Muscle Cells
Introduction
The Nerve Stimulus and the Action Potential
9. Describe the relationship between a motor nerve, motor neuron, and a motor
unit.
Nerve = 100s of motor neurons
Axons of motor neurons branch into a number of axonal terminals
Motor unit = a motor neuron and all the fibers it stimulates
10. Describe the readiness of the resting muscle fiber.
Resting membrane potential established
Ca2+ stored in SR
Myosin heads are pulled back
11. How does the motor neuron initiate an action potential on the sarcolemma?
Releases acetylcholine (ACh)
ACh binds to receptors and Na channels open
Na entering changes the voltage, opens more sodium channels
K channels open in response, voltage returns to normal
Wave of voltage change = action potential
12. What must be done to stop the contraction and get the cell ready for another
one?
ACh is broken down by the enzyme acetylcholinesterase
Na pumped out, K pumped in
Ca actively transported into SR
Myosin heads pulled back
Mechanism of Muscle Contraction: The Sliding Filament Theory
13. Summarize the sliding filament theory of skeletal muscle contraction.
Neither thick nor thin filaments shorten
Thin filaments slide over thick towards the middle of the sarcomere
14. How does the action potential start the contraction?
Causes the release of Ca from the SR
Ca binds to tropomyosin on the thin filament
Opens up places for myosin heads to attach and pull
15. Order the cyclic events in the myosin-actin interaction.
Cross bridge attachment
Power stroke
ATP binding and cross bridge detachment
Hydrolysis of ATP and cocking of the myosin head
Contraction of a Skeletal Muscle as a Whole
Graded Responses
16. List two ways in which muscle contraction may be graded.
Increase the rapidity of stimulation
Stimulate more fibers
Providing Energy for Contraction
17. How much ATP is stored in skeletal muscle cells?
4-6 seconds worth
18. Once its stored ATP is depleted, how does a muscle fiber generate more?
Creatine phosphate + ADP ==> Creatine + ATP
Anaerobic respiration making lactic acid
Aerobic respiration
19. Correlate ATP generation mechanism and exercise type.
ATP + CP, 100 meters
Anaerobic, 400 meters
Aerobic, anything longer
Muscle Fatigue and Oxygen Debt
20. Define muscle fatigue and list factors contributing to this condition.
= physiological inability to contract
Factors: low ATP, accumulation of lactic acid, ion imbalances
21. List biochemical physiological activities which are carried out as the oxygen
debt is repaid.
Get rid of lactic acid and make ATP and CP
Types of Muscle Contraction - Isotonic and Isometric
Velocity and Duration of Contraction
22. What characteristics are used to classify the types of skeletal muscle fibers?
Speed of contraction; how fast myosin splits ATP
Source of ATP
Oxidative use aerobic respiration
Glycolytic use lactic acid fermentation
23. Contrast the major types of skeletal muscle fibers.
Slow oxidative
High myoglobin stores O2, makes muscle red
Fatigue-resistant
For high endurance activities
Fast oxidative
High myoglobin stores O2, makes muscle red
Moderately fatigue-resistant
For sprinting, walking
Fast glycolytic
Low myoglobin makes muscle much lighter
Fatigable
Short-term intense activity like swingin’ dat bat
Muscle Tone
24. Describe functions of muscle tone.
Maintain firmness, health, readiness
Effect of Exercise on Muscles
25. Describe several effects of aerobic or endurance exercise on skeletal muscle.
Greater endurance, strength, fatigue-resistance
Capillaries, mitochondria, oxygen storage increase
26. Describe beneficial effects of aerobic or endurance exercise other than
those on muscle.
Metabolism and neuromuscular coordination more efficient
Improves digestion and elimination
Strengthens the skeleton
Increases capacity of cardiovascular and respiratory systems
27. Describe exercise required to increase muscle mass.
High-intensity resistance exercise
“... a few minutes every other day is sufficient.”
MUSCLE MOVEMENTS, TYPES, AND NAMES
Introduction
Types of Body Movements
Introduction
28. Define origin and insertion as it pertains to muscle.
Origin = attachment to the immovable or less movable bone
Insertion = attachment to the movable bone
Special Movements
Interactions of Skeletal Muscles in the Body
29. Differentiate prime mover, antagonist, synergist, and fixator. [4 points]
Prime mover
= the muscle causing most of a movement
Ex. biceps flexes the forearm
Antagonist
= the muscle causing the opposite movement
Ex. triceps extends the forearm
Synergist
= a muscle helping the prime mover
Ex.: brachioradialis helps flex the forearm
Fixator
= a muscle contracting to stabilize the origin of the prime mover
Ex. trapezius holds shoulder steady while flexing forearm
Naming Skeletal Muscles
30. What characteristics are used in naming muscles?
Location, like temporalis
Shape, like deltoid
Relative size, like gluteus maximus
Direction of fibers, like transverses abdominus
Number of origins, like triceps
Location of attachments, like sternocleidomastoid
Action, like adductor magnus
MUSCLE MECHANICS: IMPORTANCE OF Fascicle ARRANGEMENT AND LEVERAGE
31. How are the three types of muscle systems distinguished?
1st class: fulcrum in the middle
2nd class: load in the middle
3rd class: effort on the middle
Summary: 1-2-3, F-L-E
32. Exemplify the three lever systems.
1st class: scissors; nodding the head
2nd class: wheelbarrow; calf muscle pulling you up on tiptoe
3rd class: forceps; biceps contract when doing curls
33. What three factors are affected by the three components of the body’s lever systems?
Speed of contraction
Range of movement
Weight of the load that can be lifted
GROSS ANATOMY OF SKELETAL MUSCLES
DEVELOPMENTAL ASPECTS OF THE MUSCULAR SYSTEM
34. Characterize the transmission and progression of Duchenne muscular dystrophy. [3 points]
Sex-linked recessive
B/w 2 and 6 become clumsy; eventually interferes with breathing; respiratory failure in
20s
35. In what directions does neuromuscular coordination develop? [2 points]
Head-to-toe and proximal-to-distal
36. Describe an auto-immune disease affecting the neuromuscular junction. [3 points]
Myasthenia gravis: droopy lids, trouble swallowing, weakness
Fewer ACh receptors present
Antibodies to ACh receptors present