1. 9
MUSCLES & MUSCLE TISSUE

2. PART I
MUSCLES & MUSCLE TISSUE
OVERVIEW OF MUSCLE TISSUES

3. a. Types of muscle tissue
Skeletal
Cardiac
Smooth
Structure
Striated/Nonstriated?
Location
Where is this muscle tissue found in the body?
Function
Voluntary/Involuntary?
What is its function?
Striated (striped)
Striated (striped)
Nonstriated
Packaged in skeletal muscles that attach to and cover the bony skeleton
Occurs only in the walls of the heart
Walls of hollow visceral organs (e.g. stomach, urinary bladder, uterus, blood vessels)
Voluntary (consciously controlled)
Overall body mobility
Involuntary (unconsciously controlled)
Pump blood
Involuntary (unconsciously controlled)
Force substances through internal body channels

4. i. Overview of muscle tissues
B. Types of Muscle Tissue
Muscle contraction depends on two kinds of myofilaments – actin and myosin
Muscle Terminology
Prefixes – myo, mys, and sarco all refer to muscle
Myo-, mys-: muscle
Sarco-: flesh

5. b. Functional Characteristics of Muscle Tissue
Excitability/Irritability – ability to receive and respond to stimuli
Contractility – ability to shorten forcibly
Extensibility – ability to be stretched or extended
Elasticity – ability to recoil and resume the original resting length after being stretched

6. Stabilize Joints – stabilize and strengthen joints of the skeleton
c. Muscle Functions
Produce Movement – locomotion, coursing blood through the body, propulsion of substances through organs and tracts
Maintain Posture – erect or seated posture despite downward pull of gravity
Stabilize Joints – stabilize and strengthen joints of the skeleton
Generate Heat – muscles generate heat as they contract and maintain normal body temperature
Skeletal muscles are responsible for all locomotion
Cardiac muscle is responsible for coursing the blood through the body
Smooth muscle helps maintain blood pressure, and squeezes or propels substances (i.e., food, feces) through organs

7. Which of the following is not a prefix used to refer to muscle?
mys
myo
sarco
lemma
Answer: d. lemma

8. all of these muscle types are subject to conscious control
Of the following muscle types, which is the only one subject to conscious control?
smooth
skeletal
cardiac
all of these muscle types are subject to conscious control
Answer: b. skeletal

9. skeletal muscle is the only striated muscle type
Which two types of muscle appear striated when examined under a microscope?
smooth and skeletal
smooth and cardiac
cardiac and skeletal
skeletal muscle is the only striated muscle type
Answer: c. cardiac and skeletal

10. PART II
ANATOMY OF SKELETAL MUSCLE
MUSCLES & MUSCLE TISSUE

11. i. Skeletal muscle Gross Anatomy of a Skeletal Muscle
Each skeletal muscle is a discrete organ, made up of skeletal muscle fibers, blood vessels, nerve fibers, and connective tissue.
Connective Tissue Sheaths
In an intact muscle, the individual muscle fibers are wrapped and held together by several different connective tissue sheaths.
These connective tissue sheaths support each muscle fiber and reinforce the muscle as a whole, preventing muscles from bursting during exceptionally strong contractions.

12. 1. Connective tissue sheaths
Endomysium – surrounds each individual muscle fiber
Perimysium – surrounds each fascicle (groups of endomysium-wrapped muscle fibers)
Epimysium – surrounds the whole muscle

13. The connective tissue that covers each muscle fiber is the ________.
epimysium
perimysium
sarcolemma
endomysium

14. A. Gross anatomy of skeletal muscle
Attachments
Most skeletal muscles span joints and are attached to bones in at least two places.
When a muscle contracts, the muscle’s insertion (movable bone) moves toward the muscle’s origin (immovable or less movable bone).
Muscle attachments, whether origin or insertion, may be direct or indirect.

15. 2. attachments
Direct Attachments – epimysium of muscle is fused to periosteum of bone
Indirect Attachments – muscle’s connective tissue wrappings extend beyond the muscle and anchor the muscle to bone
Tendon – ropelike connective tissue; attaches muscle to bones
Aponeurosis – connective tissue sheet; attaches muscle to bones

16. A sheet like extension of the epimysium is called ________.
direct attachment
indirect attachment
tendon
aponeurosis
both 1 and 3
both 2 and 3
both 1 and 4
both 2 and 4

17. B. Microscopic Anatomy of a Skeletal Muscle Fiber
Each skeletal muscle fiber is a long cylindrical cell with multiple nuclei arranged underneath its sarcolemma, or plasma membrane.
The sarcoplasm, or cytoplasm, of a muscle fiber contains unusually large amounts of glycosomes (granules of stored glycogen – to be used to make ATP in cellular respiration) and myoglobin (a red pigment that stores oxygen – to be used to make ATP in cellular respiration).

18. B. Microscopic Anatomy of a Skeletal Muscle Fiber
Myofibrils
Each muscle fiber contains many rod-like myofibrils.
The myofibrils contain the contractile elements of skeletal muscle cells.

19. b. Microscopic anatomy of skeletal muscle fiber
Striations, Sarcomeres, and Myofilaments
Each myofibril is composed of two types of myofilaments.
Myosin – thick protein filaments
Actin – thin protein filaments
Actin and myosin overlap to form light and dark bands.
The alternation of these light and dark bands form striations.

20. The thin filaments of muscle fibers are comprised of which of the following components?
titin
troponin
actin
myosin
Answer: b. titin

21. 2. striations, sarcomeres, and myofilaments
These striations are actually bands, zones, and lines.
A Band – overlapping myosin and actin (dark bands)
H Zone – within an A band; myosin only
I Band – actin only (light bands)

22. 2. striations, sarcomeres, and myofilaments
M Line – within H Zone; where 2 myosin protein filaments join
Z Disc – within I Band; where 2 actin protein filaments join; forms sarcomere boundary
Sarcomeres are the basic units of contraction.
They extend from Z Line to Z Line.

23. Thick filaments are found in the ________ of the sarcomere.
Z-disc
I-band
A-band
all of the above contain thick filaments

24. The basic unit of contraction of a muscle fiber is the __________.
myofibril
sarcomere
fascicle
myofilament
Answer: a. sarcomere

25. C. ULTRASTRUCTURE AND MOLECULAR COMPOSITION OF THE MYOFILAMENTS
Thick Filament
Components
Myosin – protein with heads that form cross bridges between thick and thin filaments

26. C. ULTRASTRUCTURE AND MOLECULAR COMPOSITION OF THE MYOFILAMENTS
Thin Filament
Components
Actin – protein with active sites to which the myosin heads attach during contraction
Tropomyosin – rope-like protein wrapped around thin filaments; block myosin binding sites on actin in a relaxed muscle fiber
Troponin – binds calcium during muscle contraction

27. c. Ultrastructure and molecular composition of myofilaments

28. d. Sarcoplasmic reticulum and t-tubules
The sarcoplasmic reticulum stores calcium and releases it on demand when the muscle fiber is stimulated to contract.
Elongated tubes, called T-tubules, extend from the sarcolemma and penetrate deep into the muscle cell. They conduct impulses deep into the muscle cell and allow for uniform and synchronous contraction of the muscle.

29. The thin filaments are not comprised of which of the following components?
actin
titin
troponin
tropomyosin
Answer: b. titin

30. Calcium ions will bind to ________ when present in the sarcoplasm.
myosin heads
ATP
myosin binding sites
troponin

31. What is the major function of the sarcoplasmic reticulum?
store sodium ions
store potassium ions
expel calcium ions from the cell
store calcium ions
Answer: d. store calcium ions

32. The t-tubules are an extension of the ___________.
sarcomere
sarcoplasmic reticulum
sarcolemma
endomysium

33. PART III MUSCLES & MUSCLE TISSUE
SLIDING FILAMENT THEORY OF CONTRACTION

34. ii. Sliding filament model of contraction
Sliding Filament Theory of Contraction
During contraction, the thin filaments slide past the thick filaments so that the actin and myosin filaments overlap.

35. the A-bands get shorter
During a muscle contraction, the sliding filament theory would be apparent in a sarcomere because __________.
the I-bands get longer
the A-bands get shorter
the H zone becomes less obvious and the Z-discs move closer together
the Z-discs get pulled closer toward the I-bands and the H zone becomes more obvious
Answer: c. the H zone becomes less obvious and the Z-discs move closer together

36. ii. Sliding filament model of contraction
Mechanism
Muscle contraction requires calcium and energy, in the form of ATP, in order for the thick and thin filaments to slide past each other. The steps are:

37. B. Mechanism Relaxation
Prior to muscle contraction, the myosin binding sites on the actin molecule are physically blocked by tropomyosin. In addition, ATP is bound to the myosin heads. As a result, the myosin heads of the thick filaments cannot attach to the thin filaments.

38. B. Mechanism Contraction
Arrival of an action potential causes release of Ca2+ from the sarcoplasmic reticulum.
The Ca2+ binds to troponin, which changes shape and removes the blocking action of tropomyosin so that the myosin binding sites on the actin filament become exposed.

39. B. Mechanism Contraction
Cross Bridge Formation: ATP turns into ADP, releasing energy and allowing the myosin heads to attach to the binding sites on the actin filament, forming ‘cross bridges’.

40. B. Mechanism Contraction
Power Stroke: The myosin heads push on the thin filament, sliding it toward the center of the sarcomere.

41. B. Mechanism Contraction
Cross Bridge Detachment: Fresh ATP attaches to the myosin heads, releasing them from the binding sites on the actin and re-priming them for a repeat movement.

42. 2. contraction
These cross bridge attachments are formed and broken several times during a contraction. As this occurs simultaneously in myofibrils throughout the cell, the muscle cell shortens.

43. In a resting muscle cell the myosin binding sites are blocked by ________.
actin
myosin
troponin
tropomyosin

44. When a muscle cell is at rest most of the intracellular calcium is found in the ___________.
sarcoplasm
t-tubule
sarcoplasmic reticulum
myosin heads

45. Calcium is released from the sarcoplasmic reticulum in response to ______.
ATP
calcium pumps
an action potential
troponin

46. What substance must bind to myosin heads in order for the heads to detach from the thin filaments?
calcium
ATP
troponin
sodium

47. PART IV
EXCITATION-CONTRACTION COUPLING
MUSCLES AND MUSCLE TISSUE

48. Excitation-Contraction Coupling & Sliding Filament Mechanism of Contraction Presentation
WHO: Groups of 2 students
WHAT: Using the paper model, present the steps involved in Excitation-Contraction Coupling & Sliding Filament Mechanism of Contraction
HOW: Begin with an action potential propagating down the axon of a neuron. End with relaxation of the muscle fiber and release of calcium.
Be sure to include the following concepts/terms in your presentation:
Ca2+
synaptic vesicle
Acetylcholine
Na+
sarcolemma
T-tubule
sarcoplasmic reticulum
troponin
tropomyosin
myosin head
actin
Sliding Filament Theory
contraction
relaxation

49. a release of calcium ions from the sarcoplasmic reticulum
At the neuromuscular junction, the muscle contraction initiation event is ______.
a release of calcium ions from the sarcoplasmic reticulum
conduction of an electrical impulse down the t-tubules
binding of acetylcholine to membrane receptors on the sarcolemma
sliding of actin and myosin filaments past each other
Answer: c. binding of acetylcholine to membrane receptors on the sarcolemma

50. In a muscle fiber, the key intracellular event that stimulates muscle contraction is known as ________.
polarization
depolarization
repolarization
potential
Answer: b. depolarization

51. During depolarization, the sarcolemma is most permeable to _______.
sodium ions
potassium ions
calcium ions
chloride ions
Answer: a. sodium ions

52. What is calcium’s function during muscle contraction?
Calcium binds to troponin, changing its shape and removing the blocking action of tropomyosin.
Calcium binds to troponin to prevent myosin from attaching to actin.
Calcium depolarizes the muscle fiber.
Calcium flows down the t-tubules to stimulate the influx of sodium from the sarcoplasmic reticulum.
Answer: a. Calcium binds to troponin, changing its shape and removing the blocking action of tropomyosin.

53. Corpses usually exhibit rigor mortis because __________.
ATP hydrolysis stimulates myosin head attachment to actin
ATP hydrolysis promotes myosin head detachment from actin
calcium stores become deficient
corpses are non-living humans
Answer: b. ATP hydrolysis promotes myosin head detachment from actin

54. How does calcium re-enter the terminal cisternae after muscle contraction is finished?
diffusion
active transport
filtration
rings the doorbell

55. PART V
MUSCLES AND MUSCLE TISSUE
CONTRACTION OF A SKELETAL MUSCLE

56. i. Contraction of a skeletal muscle
The force exerted by a contracting muscle on an object is called muscle tension, and the opposing force exerted on the muscle by the weight of the object to be moved is called the load.

57. i. Contraction of a skeletal muscle
The Motor Unit
Each muscle is served by at least one motor nerve.
A motor neuron and all the muscle fibers it supplies is called a motor unit.
Muscles that exert fine control have small motor units.
Large, weight-bearing muscles, whose movements are less precise, have large motor units.

58. i. Contraction of a skeletal muscle
The Muscle Twitch
The response of a motor unit to a single action potential of its motor neuron is called a muscle twitch.
Graded Muscle Responses
Healthy muscle contractions are relatively smooth and vary in strength as different demands are placed on them.
These variations are referred to as graded muscle responses.

59. A single contraction in response to a single threshold stimulus is defined as _________.
summation
tetany
treppe
twitch

60. i. Contraction of a skeletal muscle
Graded Muscle Responses
Muscle contraction can be varied in two ways:
Change frequency of stimulation
Change strength of stimulus

61. i. Contraction of a skeletal muscle
Isotonic and Isometric Contractions
Isotonic Contractions (iso = same; tonic = tension)
Muscle length changes; load moved; tension constant
Isometric Contractions (iso = same; metric = measure/length)
Muscle tension changes; muscle length constant; load does not move; load > force muscle can generate

62. Which type of muscle contraction occurs when the muscle neither shortens nor lengthens during contraction?
isotonic
concentric
eccentric
isometric

63. Isometric contractions come into play when an individual is ________.
jumping
walking up-hill
lifting a heavy object
maintaining an upright posture
Answer: d. maintaining an upright posture

64. Providing Energy for Contraction
ii. MUSCLE METABOLISM
Providing Energy for Contraction
As a muscle contracts, ATP provides the energy for cross bridge movement and detachment and for operation of the calcium pump.
Surprisingly, muscles store very limited reserves of ATP, about 4-6 seconds’ worth at most.
Since ATP is the only energy source used for contraction, it must be regenerated as fast as it is broken down if contraction is to continue.

65. The energy source that is used directly for muscle contraction is ______.
ATP
glucose
creatine phosphate
fatty acids

66. Creatine Phosphate + ADP  Creatine + ATP
Muscle metabolism
ATP Regeneration
After ATP is broken down to ADP and P, it is regenerated by three pathways:
Direct Phosphorylation of ADP by Creatine Phosphate
Equation:
Creatine Phosphate + ADP  Creatine + ATP

67. B. Anaerobic Mechanism: Glycolysis and Lactic Acid Formation
Equation: Glucose  Lactic Acid + ATP
Huge amounts of glucose are used to produce relatively small amounts of ATP; accumulating lactic acid contributes to muscle fatigue and muscle soreness during intense exercise.

68. Glucose + Oxygen  Carbon Dioxide + Water + ATP
c. aerobic respiration
Equation:
Glucose + Oxygen  Carbon Dioxide + Water + ATP
Aerobic respiration provides a high yield of ATP, but it is relatively slow because of its many steps and it requires continuous delivery of oxygen and nutrients keep it going.

69. Muscle soreness may be due in part to which pathway of ATP production?
phosphorylation
aerobic respiration
anaerobic glycolysis
oxidation

70. A. Providing energy for contraction
Muscle Fatigue: physiological inability to contract even though the muscle still may be receiving stimuli; different from psychological fatigue in which the muscle can still contract but we feel tired
Oxygen Debt: extra amount of oxygen that the body must take in for restorative processes muscle needs in order to return to resting state

71. A. Providing energy for contraction
Heat Production
Only 40% of energy is used to do work – the rest is lost as heat.
Heat buildup is prevented from reaching dangerous levels by sweating.
Shivering occurs when muscle contractions are used to produce more heat.

72. PART VI
MUSCLES AND MUSCLE TISSUE
EFFECT OF EXERCISE ON MUSCLES

73. All of the following can occur during exercise except:
oxygen levels decrease
ATP levels decline
inorganic phosphate levels decrease
calcium levels decrease