Muscular System Flashcards
(94 cards)
1
Q
special characteristics of muscle tissue
A
excitability (irritability/responsiveness)
contractility
extensibility
elasticity
2
Q
function of skeletal muscles
A
producing movement maintain posture/body position stabilize joints generate heat protect abdominal organs link the body and the external environment (manipulation)
3
Q
function of cardiac muscles
A
pump blood
involuntary contractions of the heart
4
Q
functions of smooth muscles
A
peristalsis-alternating contractions and relaxations that mix and squeeze substances thru the lumen of hollow organs
propulsion of substances
5
Q
is each skeletal muscle an organ
A
yes
it is made up of several different tissues (skeletal muscle fibers, bv, nerve fibers, connective tissue) working together to perform a common function
6
Q
endomysium
A
fine sheath of areolar connective tissue
reticular fibers that surround each muscle fiber
7
Q
perimysium
A
fibrous connective tissue that surrounds groups of muscle fibers called fascicles
8
Q
epimysium
A
overcoat of dense irregular connective tissue that surrounds the entire muscle
9
Q
origin
A
the muscles attachment to the immovable/less moveable bone
10
Q
insertion
A
the attachment of the muscle to the moveable bone
11
Q
sarcolemma
A
plasma membrane of muscle
12
Q
sarcoplasm
A
cytoplasm of muscle cells that usually contains large amounts of glycosomes and myoglobin
13
Q
glycosomes
A
granules of stored glycogen that provide glucose during muscle cell activity
14
Q
myoglobin
A
red pigment that stores and binds oxygen
15
Q
what attaches muscles to bones
A
tendons
16
Q
sarcoplasmic reticulum
A
elaborate smooth endoplasmic reticulum w interconnecting tubules surrounding each myofibril
functions in the regulation and storage of intracellular calcium levels
17
Q
excitability
A
irritability/responsiveness
the ability to receive and respond to a stimuli- any change in the inside/outside envt
18
Q
contractility
A
the ability to shorten forcibly when adequately stimulated
19
Q
extensibility
A
the ability to extend or stretch even beyond resting length when relaxed
20
Q
elasticity
A
ability of a muscle to recoil and resume its resting length after stretching
21
Q
location of skeletal muscles
A
attached to bones/skin/other muscles
22
Q
location of cardiac muscle
A
in the heart
23
Q
location of smooth muscle
A
hollow visceral organs and blood vessels
24
Q
structure of skeletal muscle
A
multinucleated
long
striated
cylindrical
25
structure of cardiac muscle
```
uninucleated
short
branching
striated
cylindrical
intercalated disks- gap junx
```
26
structure of smooth muscle
uninucleated
long
spindle like
gap junx
27
ctrl of skeletal muscle
voluntary
28
ctrl of cardiac muscle
involuntary
29
ctrl of smooth muscle
involuntary
30
reproduction of skeletal?
no
31
reproduction of cardiac?
minimal
32
reproduction of smooth?
yes
33
myofibrils
```
rodlike contractile elements that make up most of the muscle volume (hundreds to thousands in a single fiber)
has striations (perfectly aligned repeating series of dark A bands, and light I bands)
```
34
T-tubules
continuation of sarcolemma that protrudes deep into the cell forming an elongated tube that increases muscle fibers surface area, and conducts nerve impulses to the deepest regions of the muscle cell
allows every sarcomere to open voltage sensor proteins which release calcuim from adj SR terminal cisternae
35
triad
the relationship that occurs bt the paired SR terminal cisternae and T-tubule
36
T-tubule proteins act as
voltage sensors, so they can change shape when there is an electrical impulse to to open calcium ion channels on the SR
37
smallest contractile unit of Skeletal and cardiac muscles is
Sarcomere- located between two successive Z disks
38
z-disk
coin shaped sheet of proteins that anchors thin filament
39
m-line
middle line that anchors the myosin
40
A-band
dark
contains thick and thin filaments
actin+myosin
41
I-band
light
only thin filaments
actin
42
H-zone
only thick filaments
| myosin
43
3 filaments in a sarcomere
thick filament
thin filament
elastic filament
44
thick filament
myosin
| extends entire length of A band
45
thin filament
actin, troponin, tropomyosin
| extends across the I band and partially into the A band
46
elastic filament
made of titin
extends from Z disk to M line and holds thick filaments in place
assists muscle cell to spring back after stretching
47
sliding filament mechanism
proposes that changes in overall fiber length are directly associated with changes in overlap between the 2 sets of filaments
H-zone disappears as actin and myosin slide over eachother in contraction
48
neuromuscular junx: AXON TERMINAL
the branched end of a neurons axon that contains synaptic vesicles w the neurotransmitter ACH
49
neuromuscular junx: SYNAPTIC CLEFT
small space separating axonal terminals with the motor end plate of the muscle fiber
50
neuromuscular junx: MOTOR END PLATE
specific part of the sarcolemma looking towards the axon terminal; contains ACH receptors
51
first thing to happen at the neuromuscular junx
nerve impulse reaches the axon terminal and travels down the T-tubules
52
second thing to happen at the neuromuscular junx
voltage gated calcium channels on the SR open and release calcium down the electrochemical gradient
53
3rd thing to happen at the neuromuscular junx
calcium entry causes ACH (neurotransmitter) to be released via exocytosis and diffuse across the synaptic cleft
54
4th thing to happen at neuromuscular junx
2 ACH bind to the ACH receptors on the NaK chemical gated channels at the motor end plate
55
neurotransmitter
chemical that is released from a nerve cell which thereby transmits an impulse from a nerve cell to another nerve, muscle, organ, or tissue
56
at the skeletal muscle fiber level ACH the neurotransmitter
allows the NaK gates to open and begin depolarization of the sarcolemma
57
neurotransmitter used in skeletal muscle contraction
Acetylcholine
58
termination of ACH caused by
acetylcholinesterase
an enzyme in the synaptic cleft that breaks down ACH into acetic acid and choline
prevents continued contraction
59
resting potential
the potential difference (-70mv) across the membrane of a resting neuron/skeletal muscle
the outside (extracellular face) is positive
the inside face is negative
60
resting potential is generated by
difference in concentration of Na, K, Cl, proteins, and anions
61
sodium is the major
extracellular ion
62
potassium is the major
intracellular ion
63
depolarization
when Na+ enters the cell causing it to become more positive (or less negative)
change from -70mv until cell reaches -55mv threshold
64
at -55mv
the Na+ voltage gated channels open and only sodium floods in until sarcolemma reaches +30mv
65
at +30mv
an action potential is created
sodium gates close
potassium gates open to let K+ out
repolarization begins
66
repolarization
Na+ voltage gated channels close
K+ voltage gated channels open and K+ diffuses out
electrical polarity -70mv becomes restored in the sarcolemma
67
action potential is started when
depolarization brings sarcolemma to -55mv
| Na+ voltage gated channels open only Na comes in
68
action potential formed when
cell reaches +30mv
| carried down T-tubules
69
action potential causes the opening of
Ca++ voltage gated channels
| the calcium binds to troponin
70
the binding of calcium to troponin causes
troponin to move tropomyn exposing the myosin binding sites
71
action potential is all or nothing because
either threshold is reached or not, no in between
72
how is electrical imbalance restored
thru repolarization
73
ionic imbalance is restored thru
the sodium potassium pump
3 Na+ out
2 K+ in
74
absolute refractory period
part of the refractory period where the Na+ channel is resetting and another AP cannot be generated
75
relative refractory period
part of the refractory period where as long as it is under -55mv a second action potential can be generated
76
importance of calcium in muscle contraction
binds to troponin removing the tropomyosin blockage
cross bridge formation
working powerstroke-myosin head piviots and pulls actin filament towards m-line
77
calcium is stored in the
sarcoplasmic reticulum
78
when nervous system stimulation ceases calcium
is actively pumped back into the extracellular fluid for storage and later use
79
importance of ATP in muscle contraction
attaches to myosin head
allows detaching of cross bridge
becomes hydrolzyed to ADP and Pi and cocks myosin head back to high energy state
80
motor unit
motor neuron and all the muscle fibers it supplies (nerve/muscle functional unit)
has muscle fibers spread thru the muscle insulated by endomysium
so contraction of a single motor unit cause weak contraction of the whole muscle
81
muscle twitch
the response of a musce to a single action potential of its motor neuron
82
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 healthy, firm, ready to respond
83
twitch myogram: LATENT
1st few ms after stimulation from depolarization to calcium release 2ms
84
twitch myogram: CONTRACT
cross bridges form
muscle shortens
10-100 ms
85
twitch myogram: RELAX
calcium is reabsorbed
muscle tension goes to zero
10-100ms
86
3 ways ATP can regenerate
interaction w creatine phosphate
aerobic respiration
lactic acid fermentation
87
interaction of ADP w creatine phosphate
1atp per 1cp
| unique high energy molc stored in muscles that supplies ATP in exercising until muscles metab adj itself to the demand
88
aerobic resp
95%
32atp
glucose-pyruvic acid-krebs cycle-ETC
uses glucose 1st 30 min then fat for energy
89
lactic acid fermentation
2 atp
glucose-pyruvate-lactic acid-blood-fuel-pyruvic acid
used in anaerobic resp when bulging muscles compress bv and impair 02 delivery
90
pain causing discontinuation of exercise is
from lactic acid build up in liver
91
only 40% of energy released in muscle activity is
useful as work
| remaining 60% given off as heat
92
differences of smooth muscle
```
thin short spindle shaped fibers
connective tissue is only endomysium
less developed SR
no myofibrils/ T-tubules
actin and myosin present but not arranged in sarcomere
gap junctions
calcium binds to CALMODULIN which activates MYOSIN KINASE which phosphorylates myosin, activating myosin ATPases that provide energy for contraction
contractions/relaxations take longer
```
93
similarities bt skeletal and smooth muscle
actin and myosin in sliding mechanism
CALCIUM IS FINAL TRIGGER
ATP IS ENERGY SOURCE
94
differences of cardiac muscle
behaves as a functional synctium-intercalated disks
cells are mechanically, chemically, electrically connected
autorhythmic cells-self excitable and can initiate own depol
use Ca influx rather than Na to create AP
more mitochondria
ability to switch to whatever nutrient supply is readily available (fat drops on top)
20% Ca comes from ecf
danger of lack of o2 not nutrients
slower
