Muscular system part 1 Flashcards
1
Q
How many muscles are there in the human body
A
600
2
Q
what is the essential function of muscle
A
contraction or shortening
3
Q
muscular contractions provide
A
body movement, propel body fluids and food, generate heartbeat, and distribute heat
4
Q
What are the 3 types of muscle tissue that humans have
A
- Skeletal muscle
- cardiac muscle
- smooth muscle
5
Q
Skeletal and smooth muscle cells are both
A
elongated; hence their cells are called muscle fibers
6
Q
what are the functions of skeletal muscles
A
- support the body and maintains posture
- make bones and other body parts move
- help maintain a constant body temperature
- contractions assists in blood and lymphatic circulation
- help protect bones and internal organs and stabilize joints
- form sphincters to regulate the passage of substances
7
Q
what are sphincters
A
specialized donut-shaped muscles that help to pinch shut openings
8
Q
what are the properties of the skeletal muscles
A
- excitability
- contractility
- extensibility
- elasticity
9
Q
What is Endomysium
A
a thin layer of areolar connective tissue that surrounds each individual muscle fiber (muscle cell)
10
Q
What are muscle fibers grouped into bundles called
A
fascicles
11
Q
what is perimysium
A
a sheath of connective tissue that covers the dascicles
12
Q
what is epimysium
A
the connective tissue layer that closely surrounds the bulk of the entire skeletal muscle
13
Q
collagen fibers of the epimysium continue as a strong
A
tendon that attaches the muscle to a bone that they will move
14
Q
what is aponeurosis
A
connective tissue forms broad fibrous sheets that attach muscles indirectly to bones, cartilages, or connective tissue coverings
15
Q
what is a skeletal muscle fiber
A
a single cells that contracts in response to stimulation and relaxes when the stimulation ends
16
Q
what is the plasma membrane called in the skeletal muscle
A
sarcolemma
17
Q
what is the cytoplasm called in the skeletal muscle
A
sarcoplasm
18
Q
what is the smooth endoplasmic reticulum called in the skeletal muscle
A
sarcoplasmic reticulum
19
Q
what is the storage site for calcium (Ca++)
A
sarcoplasmic reticulum
20
Q
Nuclei are pushed aside by
A
the long ribbon-like organelles known as myofibrils
21
Q
what does the sarcoplasmic reticulum do
A
encases hundreds or even thousands myofibrils which are bundles of myofilaments
22
Q
the sarcoplasm contains
A
- mitochondria between myofibrils
- glycogen that provides stored energy for muscle contraction
- myoglobin that binds oxygen until it is needed for muscle contraction
23
Q
Alternating Light (I) and Dark (A) bands along the length of the myofibrils give the muscle cell its
A
striated appearance
24
Q
Each myofibril is composed of
A
numerous sarcomeres
25
Each sarcomere extends between two dark, vertical lines called
Z lines
26
The light (I) band has a midline interruption (darker area) called
Z discs
27
The dark (A) band has a lighter central area called the
H zone
28
The M Line is the
center of the H zone that contains tiny protein rods that hold the adjacent thick filaments together
29
a sarcomere contains two types of proteins called
myofilaments
30
Thick and dark (A band) are filaments composed of
a single protein called myosin
31
Thin and light (I band) are filaments composed of
3 proteins
- actin
- troponin
- tropomyosin
32
The thick filaments are located in the ___ while the thin filaments are located in the __
- center
- ends
33
When a sarcomere shortens
the actin filaments slide past the myosin filaments and approach one another, forming hundreds of cross-bridges
34
These cross-bridges then move like the oars of a boat to
pull the thin filaments toward the center of the sarcomere
35
this movement is called the
sliding filament theory of muscle contraction
36
The sliding filament theory of muscle contraction brings the
Z lines closer together and increases the zone of overlap between thin and thick filaments
37
The myosin filaments contain the
ATPase enzyme which breaks down ATP and release energy needed for muscle contraction
38
Troponin and tropomyosin are inhibitory proteins that prevent the
sliding of the actin and myosin filaments when the muscle fiber is relaxed
39
The nerve impulses for voluntary movement come from the
motor areas of the brain
40
the motor areas of the brain generate
motor impulses
41
what do the motor impulses travel along
motor nerves
42
after motor nerves
motor neurons in the spinal chord
43
motor neurons carry the impulses to the
muscles and cause them to contract
44
what is a motor unit
a single motor neuron and all the skeletal muscle cells it stimulates constitute a motor unit
45
each motor neuron has a long extension called an
axon
46
An axon reaches the muscle and branches into a number of
axon terminals
47
the axon terminals form
junctions with the sarcolemma of a different muscle cell
48
The junctions that contain vesicles filled with a chemical are called
Neuromuscular junctions
49
What is the chemical in the vesicles called
nuerotransmitter
50
What is the specific neurotransmitter that stimulates skeletal muscle cells
Acetylcholine
51
What is the point where the axon terminal of a motor neuron contacts the sarcolemma of a muscle cell
neuromuscular junction
52
The axon terminal contains presynaptic vesicles containing a chemical called
neurotransmitter acetylcholine
53
the sarcolemma of the muscle fibers contain
receptor sites for acetylcholine
54
At the synapse the synaptic cleft is
the tiny space between the axon terminal and the sarcolemma
55
events at the neuromuscular junctions
1. motor impulse
2. calcium channels open
3. calcium stimulates the release of acetylcholine
4. sarcolemma becomes more permeable to sodium ions
5. generates a current called action potential
6. a single nerve impulse produces only one contraction
56
what happens in event 1
contraction begins when a motor impulse arrives at the axon terminal
57
what happens in event 2
calcium channels open and the calcium enters the axon terminal
58
what happens in event 3
calcium stimulates the release of acetylcholine from presynaptic vesicles. Acetylcholine crosses the synaptic cleft and binds to receptors in the sarcolemma of the muscle fiber
59
what happens in event 4 (depolarization)
if enough acetylcholine is released, the sarcolemma becomes more permeable to sodium ions that rush into the muscle cells and diffuse potassium ions
- the imbalance gives the cell excessive positive sodium ions
60
what happens in event 5
action potential if generated and travels over the sarcolemma conducting electrical impulse resulting in the contraction of the muscle
61
when acetylcholine is broken down by acetylcholinesterase in event 5 what occurs
repolarization
62
what happens in event 6
a single nerve impulse produces only one contraction. Until one Is over the next one cannot start
63
depolarization is followed by repolarization which involves
the outflow of potassium ions that will restore positive charge to the outside of the sarcolemma
64
AcetylCholinesterase enzyme in the sarcolemma
inactivates acetylcholine and in the absence of further impulses, the muscle fiber will relax and return to its original length
65
Graded responses are produced in 2 ways
1. by changing frequency
2. by changing the number of muscle cells being stimulated
66
what is an example of changing the frequency of muscle stimulation
muscle twitches, Tetanus
67
what is an example of changing the number of muscle cells being stimulated at a time
stronger muscle contraction
68
ATP is the
primary source of energy and is not stored in large amounts in muscle fibers
69
Secondary sources of energy are
Creatin PO4 and Glycgoen
70
Creatine PO4
an energy-transferring molecule; the energy released by the break down of creatine is used to synthesize more ATP
71
Glycogen
the most abundant source of ATP
when energy is needed for sustained contractions it is first broken down to glucose and then ATP
72
aerobic metabolism
oxygen is present
73
anaerobic metabolism
oxygen is not present
74
muscles have 2 sources of oxygen
1. hemoglobin
2. myoglobin
75
Hemoglobin
circulating blood brings a continuous supply of oxygen carried by the protein hemoglobin present in the red blood cells
76
myoglobin
muscle fibers carry a protein called myoglobin which stores some oxygen
77
what are the 3 pathways for ATP generation
1. aerobic respiration
2. anaerobic glycolysis
3. direct phosphorylation
78
aerobic respiration (Kreb's cycle)
- occurs in mitochondria
- very efficient yields 32 ATP
- slow
- requires lots of oxygen during strenuous activty
79
Anaerobic glycolysis
- occurs in the cytoplasm
- glucose breaks down to pyruvic acid and produces 2 ATP molecules
- pyruvic acid is converted to lactic acid
- 2 1/2 times faster
80
lactic acid accumulation produces severe
muscle fatigue and soreness
81
direct phosphorylation
- it can regenerate ATP by transferring its phosphate to ADP
- generates ATP very rapidly but it supplies only for 8 seconds
82
creatine phosphate is rebuilt when a muscle is
resting by transferring a phosphate group from ATP to creatine
83
what is oxygen debt (deficit)
in spite of the increase in respiratory rate, muscle fibers literally run out of oxygen
84
the intermediate lactic acid produced in an anaerobic process
lowers the pH of the intracellular fluid within the muscle cell which contributes to muscle fatigue
85
muscle tone is a steady or
constant state of partial contraction in a resting muscle
86
hypertrophy
muscle increases in size due to exercise
87
atrophy
muscle decreases in size
88
what are the types of muscle contractions
1. isotonic contractions
2. isometric contractions
89
isotonic contraction
- muscle contracts and brings movement
- tone or tension remains the same
- examples include jogging, swimming, weight lifting etc
90
isometric contractions
- involves contraction without movement
- tension in muscles increases
- examples include pushing against the wall with bent elbows, both hands pushing equally
