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Anatomy Chapter 9 and 10 > Anatomy Chapter 9 and 10 > Flashcards

Anatomy Chapter 9 and 10 Flashcards

1
Q

What is the body location of skeletal muscle?

A

Attached to bones or (some facial muscles) to skin

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2
Q

What is the body location of cardiac muscle

A

Walls of the heart

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3
Q

What is the body location of smooth muscle

A

Unitary muscle in walls of hollow visceral organs (other than the heart) multi-unit muscle in intrinsic eye muscles, air ways, large arteries

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4
Q

What is the cell shape and appearance of skeletal muscle?

A

Single, very long, cylindrical, multinucleate cells with obvious striations

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5
Q

What is the cell shape and appearance of the cardiac muscle?

A

Branching chains of cells, uni- or binucleate, striations

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6
Q

What is the cell shape and appearance of the smooth muscle?

A

Single, spindle-shaped, uninucleate; no striation

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7
Q

What are the special characteristics of muscle tissue?

A

Excitability (responsiveness or irritability): ability to receive and
respond to stimuli
Contractility: ability to shorten when stimulated
Extensibility: ability to be stretched
Elasticity: the ability to recoil to resting length

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8
Q

What are muscle functions?

A
  1. Movement of bones or fluids (e.g., blood)
  2. Maintaining posture and body position
  3. Stabilizing joints
  4. Heat generation (especially skeletal muscle)
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9
Q

Describe a muscle (organ)

A

Consists of hundreds to thousands of muscle cells, plus connective tissue wrappings, blood vessels, and nerve fibers and is covered externally by the epimysium

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10
Q

Describe a fascicle (a portion of the muscle)

A

A discrete bundle of muscle cells, segregated from the rest of the muscle by a connective tissue sheath and is surrounded by perimysium

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11
Q

Describe a muscle fiber (cell)

A

An elongated multinucleate cell; it has a banded (striated) appearance and is surrounded by endomysium

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12
Q

Describe a thick filament?

A

Each thick filament consists of many myosin molecules
whose heads protrude at opposite ends of the filament.

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13
Q

Describe a thin filament?

A

A thin filament consists of two strands of actin subunits
twisted into a helix plus two types of regulatory proteins
(troponin and tropomyosin).

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14
Q

Describe ion channels

A
  • Play the major role in changing of membrane potentials
  • Two classes of ion channels:
  • Chemically gated ion channels – opened by chemical messengers such as
    neurotransmitters
  • Example: ACh receptors on muscle cells
  • Voltage-gated ion channels – open or close in response to voltage changes
    in membrane potential
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15
Q

What four steps must occur for skeletal muscle to contract

A
  1. Events at neuromuscular junction
  2. Muscle fiber excitation
  3. Excitation-contraction coupling
  4. Cross bridge cycling
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16
Q

Describe a neuromuscular junction?

A

The region where the motor neuron contacts the skeletal muscle. It consists of multiple axon terminals and the underlying junctional folds of the sarcolemma

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17
Q

What are the sequence of events leading to contraction?

A
  1. Events at the
    neuromuscular
    junction
    2.Muscle fiber excitation
    3.Excitation-contraction coupling
    4.Cross Bridge Cycle
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18
Q

What events occur at neuromuscular junction?

A

-A motor neuron fires an action potential
(AP) down its axon.
-The motor neuron’s axon terminal
releases acetylcholine (ACh) into the
synaptic cleft.
-ACh binds receptors on the junctional
folds of the sarcolemma.
-ACh binding causes a local depolarization
called an end plate potential (EPP).

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19
Q

What occurs in the muscle fiber excitation?

A

The local depolarization (EPP) triggers an AP in the adjacent sarcolemma

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20
Q

What occurs in the excitation-contraction coupling

A

-AP in sarcolemma travels down T tubules.
-Sarcoplasmic reticulum releases Ca2+.
-Ca2+ binds to troponin, which shifts
tropomyosin to uncover the myosin-binding
sites on actin. Myosin heads bind actin.

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21
Q

What occurs in the cross bridge cycle?

A

contraction occurs via cross bridge cycling.

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22
Q

What events occur at the neuromuscular junction

A
  1. AP arrives at the axon terminal
    2.Voltage-gated calcium channels open, calcium enters motor neuron
    3.Calcium entry causes release of ACh neurotransmitter into synpatic cleft
    4.ACh diffuses across to ACh receptors (Na + chemical gates) on sarcolemma
    5.ACh binding to receptors, open gates, allowing Na+ to enter resulting in end plate potential
    6.Acetylcholinesterase degrades ACh
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23
Q

What are the requirements for skeletal muscle contraction?

A
  1. Activation: neural stimulation at a
    neuromuscular junction
  2. Excitation-contraction coupling:
    * Generation and propagation of an action potential along
    the sarcolemma
    * Final trigger: a brief rise in intracellular Ca2+ levels
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24
Q

What are the events at the neuromuscular junction

A

-Nerve impulse arrives at axon terminal
-ACh is released and binds with receptors on the sarcolemma
Electrical events lead to the generation of an action potential

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25
In the relaxed state, thin and thick filaments overlap only what ?
Overlap only slightly
26
What occurs during contraction
During contraction, myosin heads bind to actin, detach, and bind again, to propel the thin filaments toward the M line
27
As h zones shorten and disappear what else occurs
sarcomeres shorten, muscle cells shorten, and the whole muscle shortens
28
What occurs when a sarcomere contracts
the Z lines move closer together, and the I band becomes smaller. The A band stays the same width.
29
What occurs at full contraction
the thin and thick filaments overlap.
30
ACh effects are quickly terminated by what and what does it prevent
by the enzyme acetylcholinesterase. Prevents continued muscle fiber contraction in the absence of additional stimulation
31
what are the summary of events in the generation and propagation of an action potential in a skeletal muscle fiber?
1. An end plate potential (EPP) is generated at the neuromuscular junction 2.Depolarization: Generating and propagating an action potential (AP) 3. Repolarization: Restoring the sarcolemma to its initial polarized state (negative inside positive outside)
32
What is the latent period?
-Time when E-C coupling events occur -Time between AP initiation and the beginning of contraction
33
What are the events of excitation contraction coupling
AP is propagated along sarcomere to T tubules Voltage-sensitive proteins stimulate Ca2+ release from SR Ca2+ is necessary for contraction
34
What is excitation contraction coupling
it is the sequence of events by which transmission of an action potential along the sarcolemma leads to the sliding of myofilaments
35
What is the cross bridge cycle?
It is the series of events during which myosin heads pull thin filaments toward the center of the sarcomere
36
What occurs in the cross bridge cycle ?
1.Cross bridge formation 2.The power (working) stroke 3.Cross bridge detachment 4.Cocking of mysosin head
37
What does a motor unit consist of
Consists of One Motor Neuron and All The Muscle Fibers it Innervates
38
Where do the axons of motor neurons extend from
from the spinal cord to the muscle
39
What do branching axon terminals form?
Form neuromuscular junctions, one per muscle fiber
40
Describe muscle tone
-Constant, slightly contracted state of all muscles -Due to spinal reflexes that activate groups of motor units alternately in response to input from stretch receptors in muscles -Keeps muscles firm, healthy, and ready to respond
41
What is muscle fatigue
Physiological inability to contract
42
When does muscle fatigue occur
Occurs when: Ionic imbalances (K+, Ca2+, Pi) interfere with E-C coupling Prolonged exercise damages the SR and interferes with Ca2+ regulation and release
43
What occurs rarely, during states of continuous contraction, and causes contractures (continuous contractions)
Total lack of ATP
44
Why is extra O2 needed after exercise?
For replenishment of -oxygen reserves -Glycogen stores -ATP and CP reserves Conversion of lactic acid to pyruvic acid, glucose, and glycogen
45
What are isotonic contractions
Muscle changes in length and moves the load
46
Isotonic contractions are either what
Either concentric or eccentric
47
What occurs in concentric contractions
the muscle shortens and does work
48
What occurs in eccentric contractions
the muscle contracts as it lengthens
49
Describe isometric contractions
-The load is greater than the tension the muscle is able to develop -Tension increases to the muscle’s capacity, but the muscle neither shortens nor lengthens
50
What is the only source used directly for contractile activities
ATP
51
Available stores of ATP are depleted in how many seconds
are depleted in 4–6 seconds
52
How is ATP regenerated by
-Direct phosphorylation of ADP by creatine phosphate (CP) -Anaerobic pathway (glycolysis) -Aerobic respiration
53
What are factors that increase the force of skeletal muscle contraction
-High frequency of stimulation (temporal summation and tetanus) -Large number of muscle fibers recruited -Large muscle fibers -Muscle and sarcomere stretched to slightly over 100% of resting length
54
What is velocity and duration of contraction influenced by
Influenced by: Muscle fiber type Load Recruitment
55
What are the factors that influence the velocity and duration of skeletal muscle contraction
-Predominance of fast glycolytic fibers -Small Load/Increased recruitment -Predominance of slow oxidative fibers
56
What is the influence of load on duration and velocity of muscle shortening
a. The greater the load, the briefer the duration of muscle shortening b. The greater the load, the slower the muscle shortening
57
What do long-distance runners have a large number of
They have a large number of SO fibers and relatively few FO and FG fibers
57
What do long-distance runners have a large number of
They have a large number of SO fibers and relatively few FO and FG fibers
58
What do body builders have a large number of
They have a large number of FG fibers and relatively few FO and SO fibers
59
What does Aerobic (endurance) exercise such as jogging, swimming, biking lead to
Leads to increased -Muscle capillaries -Number of mitochondria -Myoglobin synthesis -Results in greater endurance, strength, and resistance to fatigue -May convert fast glycolytic fibers into fast oxidative fibers
60
What does resistance exercise such as weight lifting or isometric exercises lead to
-Muscle hypertrophy Due primarily to increase in fiber size -Increased mitochondria, myofilaments, glycogen stores, and connective tissue -Increased muscle strength and size
61
what are intercalated discs apart of
Are part of the cardiac muscle sarcolemma
62
What do intercalated discs contain
contain gap junctions and desmosomes.
63
Where can smooth muscle tissue be found in
around organs in the digestive, respiratory, reproductive tracts and the iris of the eye.
64
What do intermediate filaments and dense bodies of smooth muscle fibers do
Harness the pull generated by myosin cross bridges
65
Smooth muscle are usually in what two layers
longitudinal and circular)
66
Longitudinal layer of smooth muscle shows what
Shows smooth muscle fibers in cross section
67
Circular layer of smooth muscle shows what
shows longitudinal views of smooth muscle fibers
68
What is peristalsis
Alternating contractions and relaxations of smooth muscle layers that mix and squeeze substances through the lumen of hollow organs
69
What occurs when longitudinal layer contracts
organ dilates and shortens
70
What occurs when circular layer contracts
organ constricts and elongates
71
What can happen in hyperplasia
Smooth muscle cells can divide and increase their numbers Example: estrogen effects on uterus at puberty and during pregnancy
72
Within age what happens to connective tissue and muscle fibers
Connective tissue increases and muscle fibers decrease
73
By what age does loss of muscle mass begin
by age 30
74
What does regular exercise reverse
Reverses Sarcopenia
75
What may block distal arteries, leading to intermittent claudication and severe pain in leg muscles
Atherosclerosis
76
In the body a first class lever system does what
raises your head off your chest
77
What does the posterior neck muscles do
provide the effort
78
What is the atlanto-occipital joint
It is the fulcrum
79
What is the weight to be lifted called
the facial skeleton
80
Second class leverage in the body is exerted when you do what
When you stand on tip-toe
81
What is the exert exerted by when you stand on your tip-top
exerted by the calf muscles pulling upward on the heel
82
What is the fulcrum when you stand on tip-toe
the joints and the ball of the foot
83
What is the load when you stand on tip-toe
the weight of the body is the load
84
In the body what exemplifies a third class leverage
flexing the forearm by the biceps brachii muscle
85
Where is the effort exerted by when flexing the forearm
proximal radius of the forearm
86
What is the fulcrum when flexing the forearm
the elbow joint
87
What is the load when flexing the forearm
The hand and distal end of the forearm

Anatomy Chapter 9 and 10 (1 decks)

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