Midterm 2 Flashcards
1
Q
what are the types of myfilaments
A
- thick filaments
- thin filaments
- elastic filaments
2
Q
thick filaments
A
bundles of contractile protein myosin
3
Q
myosin
A
- have globular heads linked by intertwining tails
- each head has a active site that binds to actin
- myosin tails from opposite sides are attached together at the M-line
4
Q
thin filaments
A
proteins, actins, tropomyosin, and troponin
5
Q
actin
A
- multiple actin subunits string together, form two intertwining strands in functional thin filaments
6
Q
troponin
A
- small globular regulator protein, holds tropomyosin in place, assists with turning contractions on and off
7
Q
tropomyosin
A
- long rope-like regulatory protein, twists around actin, covering up active sites
8
Q
elastic filaments
A
single spring-like protein (titin)
- stabilizes the myofibril structure
9
Q
sarcomere
A
- the smallest functional unit of a skeletal muscle fiber
10
Q
I band
A
contains only thin filaments
11
Q
Z disc
A
in the middle of I band
- anchor thin filaments in place
- attachment point for elastic fibers
12
Q
A band
A
contains a zone of overlap, with both thick and thin filaments
- generate tension during contraction
13
Q
H zone
A
middle of A band contains only thick filaments
14
Q
M line
A
dark like in the middle of A band
- structural proteins hold thick filaments
- anchors elastic filaments
15
Q
filament sliding mechanics
A
myosin head attaches to actin –> pulls thin filament towards M-line –> brings Z discs closer together
- I band and H zone narrow
- A band doesn’t change
16
Q
cross bridge formation
A
when myosin and actin attach
17
Q
cross bridge cycling
A
the on/off interaction between myosin and actin
18
Q
stages of the cross bridge cycle
A
- ATP hydrolysis
- cross bridge formation
- powerstroke
- detachment
19
Q
ATP hydrolysis
A
- atp cocks myosin head
- atp turns into adp and Pi
ATP + H2O –> ADP + Pi
20
Q
cross bridge formation
A
- myosin head attaches to actin
21
Q
powerstroke
A
- adp and pi are released from myosin
22
Q
detachment
A
- another atp binds to myosin
- breaks the attachment to actin
23
Q
contraction cycle
A
repeats as long as atp is present
- repeats 20-40 times for each myosin head (cross-bridge cycle)
24
Q
channels definition and the types
A
transmembrane proteins allow certain substances to cross the membrane
- always open
- gated
25
always open channels
like pores, flow down their gradient
- leak channels
26
gated channels
- mechanically: uses a physical force
- chemically: ligand binds to a protein receptor
- electrically: controlled by a voltage change
27
true or false
a motor unit exits the spinal cord and consists of two motor neurons and innervates one muscle fiber
false
a motor unit consists of one motor neuron and innervates multiple muscle fibers
28
neuromuscular junction
the connection between the motor neuron and a muscle fiber
- where a nerve impulse (AP) is transmitted to the sarcolemma of the muscle fiber
29
skeletal muscles
- made up of long multinucleated cells arranged parallel
- contractions are voluntary
- striations
30
cardiac muscles
- short/highly branched with one nucleus
- intercalated discs joined together (contains gap junctions & desmosomes --> tight junctions)
- contractions is involuntary
- synchronous contractions
- striations
31
smooth muscles
- long/flat, single centrally located nucleus
- involuntary contractions
- linked by gap junctions
- allows synchronized contractions
- no striations
32
fasicles
bundles of muscle fibers within a skeltal muscle
33
types of muscle shapes
- parallel
- pennate (uni,bi, and multi)
- convergent
- circular
- fusiform
34
axon terminal
the end of the motor neuron axon where the electrical signal is transmitted to a chemical signal
- contains voltage gated Ca2+ channels
- contains synaptic vesicles that are filled with acetylcholine (ACh)
35
neurotransmitter
a chemical that transmits a signal from a neuron and triggers a change
36
synaptic cleft
the space between the axon terminal and muscle fiber
37
motor end plate
specialized region of the muscle fiber sarcolemma
- folded and contains NA+ channels
38
myosin and actin attachment steps
(4 steps)
1. Ca2+ (stored in the SR) binds to troponin
2. troponin changes shape and pulls tropomyosin
3. binding site on actin is exposed
4. myosin binds to actin (ATP present)
39
true or false
muscle fibers are excitable cells
true
40
excitable cells
- produce action potential
- defined by a rapid/ temporary change in membrane potential
- generated by opening/closing of Na+/K+ channels (active transporters)
41
membrane potential
the electrical potential difference across the plasma membrane
- mainly Na+ and K+
- rest at -90mV
42
resting membrane potential (RMP)
- at -90mV
- Na+ and K+ channels closed
43
depolarization
- Na+ channels open (Na+ enters cell)
- K+ channels closed
- makes less negative
44
repolarization
- Na+ channels closed
- K+ channels open (K+ exits cell)
- makes more negative
45
myofibrils
made up of contractile proteins
46
sarcoplasmic reticulum (SR)
- surrounds myofibrils
- stores and releases Ca2+
47
transverse tubules (t-tubules)
- deep inward extensions of sarcolemma
- surrounds each myofibrils
- tunnel-like network
48
terminal cisternae
- enlarged sections of the SR
- two terminal cisternae plus the corresponding t-tubule form a triad
49
how many mitochondria in a muscle fiber
many
50
how many nuclei in a muscle fiber
multiple
51
steps of skeletal muscle contractions
(4 steps)
1. Ca2+ is released from the SR at the terminal cisternae
2. Ca2+ binds to troponin
3. tropomyosin moves
4. myosin binding sites on actin becomes exposed
52
prerequisites of muscle relaxation
- no more acetylcholine is released into the synaptic cleft (motor neuron AP stops)
- acetylcholine is present in the synaptic cleft but is broken down by acetylcholinesterase
- Ca2+ ions pumped back into the SR
53
steps of muscle relaxation
(5 steps)
1. AP down the motor neuron stops
2. Acetylcholinesterase breaks down ACh
3. sarcolemma returns to RMP due to K+ exiting its channels
4. Ca2+ pumped back into the SR
5. active sites on actin are blocked
54
muscle fiber twitch
the response of 1 isolated muscle fiber to a single AP in a motor neuron
55
whats the RMP for motor neurons and muscle fibers
motor neuron: -70 mV
muscle fiber: -90 mV
56
myogram
records tension produced over time
57
what are the three phases of a muscle twitch
- latent period
- contraction period
- relaxation period
58
latent period
the time it takes the AP to propagate across the sarcolemma
59
contraction period
cross bridge cycling generates muscle tension
60
relaxation period
Ca2+ ions pumped back into the SR and muscle tension returns to resting state
61
muscle fatigue and what are the types
the inability of a muscle to maintain a given level of tension during activity
- central fatigue
- peripheral fatigue
62
central fatigue
arises from the CNS
63
peripheral fatigue
arises anywhere from the neuromuscular junction and/or within the muscle fiber
64
what does muscle fiber tension depend on
- the frequency of the AP firing by the motor neuron (wave summation)
- the length of the muscle fiber at rest (length-tension relationship)
65
length tension relationship and whats the optimal length of a sarcomere
- short enough to allow enough zone of overlap between thick and thin filaments
- long enough for thick filaments toward the M-line without running into the z-disc
- 100-120% of its resting length
66
wave summation and the types
repeated stimulation of the muscle fiber by the motor neuron results in greater tension production if the stimulus are close enough in time
- unfused tetanus
- fused tetanus
67
unfused tetanus
muscle fiber has time to partially relax between stimuli
- can get up to 80% of max
68
fused tetanus
muscle fiber doesn't have to time to relax
- can get up to 100% of max
69
fine motor control
smaller motor units
70
less control but higher power generation
larger motor units
71
true or false
as the force required for contraction decreases, the number of motor units recruited for that muscle increase
false
as the force required for contraction increase, the number of motor units recruited for that muscle increase
72
true or false
smaller motor units generally recruited first and as force decreases, larger motor units are not recruited
false
smaller motor units generally recruited first and as force increases, larger motor units are recruited
73
isotonic contractions and the types
constant tension produced, muscle length changes
- concentric
- eccentric
74
concentric contractions
muscles shorten (external force
75
eccentric contractions
muscles lengthen (external force>muscle force)
76
isometric contractions
muscle length remains constant (external force=muscle force)
77
true or false
skeletal muscle function = contraction/relaxation -->requires ATP
true
78
skeletal muscle functions
- contraction/relaxation
- pumping Ca2+ back into the SR
- power the Na+/K+ pumps to maintain gradients
79
types to generate energy for skeletal muscles and what it produces
- immediately
- rapidly
- sustained
all produce ATP
80
immediate energy
reaction with creatine phosphate in the cytosol
- stored ATP provides ATP for use (2-3 sec worth of muscle contractions)
- ADP + CP --> ATP + Creatine (10 sec worth of ms contr.)
- hydrolysis of 1 CP molecule produces 1 molecule of ATP
81
rapid energy
anaerobic metabolism in the cytosol (no oxygen) --> glycolysis
82
glycolysis
produces enough ATP for 30-40 sec of sustained muscle contractions
83
sustained energy
aerobic metabolism in the mitochondria (oxygen) --> oxidative metabolism
- cellular respiration
84
oxidative metabolism and the sources
continues to produce ATP as long as oxygen and nutrients are available
- glucose (preferred)
- fatty acids
- amino acids (if necessary)
85
how many ATP are produced by glycolysis and oxidative metabolism
1 glucose molecule produces:
2 ATP via glycolysis (anaerobic)
30 ATP via oxidative metabolism (aerobic)
in total 32 ATP
86
myoplasticity
the change in muscle structure as a result of physical training
87
types of training
- endurance (aerobic)
- resistance (strength)
88
endurance training
- aerobic
- large increase in frequency of a motor unit activation and moderate increase in force production
- causes biochemical changes
89
what are the effects of endurance training
- increased oxidative enzymes, mitochondria and associated proteins
- increasing blood vessel in network supplying muscles
- increasing fatigue resistance
- more efficient use of fatty acids and non-glucose fuels for ATP production
90
resistance training
- strength
- moderate increase in frequency of motor unit activation, large increase in force production
- causes primer anatomical changes both number of myofibrils and diameter of muscle fibres increase (hypertrophy)
91
hypertrophy
Decrease proportion of mitochondrial proteins and blood supply to muscle because of fiber enlargement
92
muscle metabolism at rest
93
muscle metabolism at moderate activity
94
muscle metabolism at peak activity
95
VO2
oxygen consumption
- the amount of oxygen taken in and used by the body per min
96
VO2 max
the max amount of O2 that an individual can use during max exercise
97
classes of skeletal muscle
- type I: slow
- type II: fast (IIa and IIx)
- classified based on myosin ATPase activity (speed of powerstroke) and the predominant energy source
98
myosin ATPase
a part of myosin is an enzyme (-ase) that catalyzes the hydrolysis of ATP --> ADP + Pi in cross bridge cycling
99
central nervous system (CNS)
brain and spinal cord
100
peripheral nervous system (PNS)
- 12 cranial nerves
- 31 spinal nerves
101
nervous system actions
- sensory input
- integration
- motor output
102
parts of the CNS
sensory (afferent):
- somatic sensory division: muscles/bones/joints and skin
- visceral sensory division: organs
motor (efferent):
- somatic motor division: muscles
- autonomic nervous system (ANS): smooth/cardiac muscles and glands
103
nervous tissue
made up of neurons and neuroglia
- neurons: are excitable cells (conduct electrical signals to transmit)
- neuroglia: provide structural support and protection for neurons
104
neuron sturcture
- cell body: soma (cell organelles)
- dendrites: receives input from other neurons
- Axon: generates/ conducts AP
- axon hillock
- axon collaterals
- axon terminals
- axolemma and axoplasm
structure:
- multipolar
- bipolar
- pseudounipolar
function:
- sensory/motor
- interneurons
105
types of neuroglia and the roles in the CNS
- astrocytes: anchor neurons and blood vessels, blood brain barrier
- oligodendrocytes: myelinated certain axons in the CNS
- microglial cell: phagocytes (immune cell)
- ependymal cell: lines cavities, cilia circulate fluid
106
types of neuroglia and roles in the PNS
- schwann cell: myelinates axons in the PNS
- satellite cells: surrounds and supports cell bodies
107
disuse
leads to anatomical and biochemical changes including decrease in number of myofibrils and size of fibre and decrease in oxidative enzymes (atrophy)
108
myelin sheath
- multiple layers of schwann cells (PNS) and oligodendrocytes (CNS) that wrap the axon
- provides insulation
109
true or false
Myelinated axons conduct action potentials about 15 to 25 times faster than unmyelinated axons
false
Myelinated axons conduct action potentials about 15 to 20 times faster than unmyelinated axons
110
RMP of a neuron and why
- K+ channels always leaking out (more)
- Na+ channels always leaking in (less)
results in -70 mV
111
local potentials and what are the parts
- smaller, local changes in the MP
- depolarization & hyperpolarization
- strength depends on the length of stimulation and number of ion channels
- weaken as they spread from source (decremental)
- multiple consume together in time and space as they spread through the cell body (neural integration)
112
depolarization and an example
Positive charges entered the cytosol (MP becomes less negative)
- eg. -70 to -60 mV
113
hyperpolarization
Either positive charges exit or negative charges enter the cytosol (MP becomes more negative)
- eg. -70 to -80 mV
114
action potentials
- large, uniform in magnitude changes in MP
- "all or none"
- depolarization --> repolarization--> RMP
- generated in the trigger zone (at the axon hillock) then regenerated and propagated along the axon length due to Na+/K+ channels in the axolemma
- requires threshold depolarization to be initiated
115
steps of action potential
(5 steps)
1. a local potential depolarizes the axolemma of the tigger zone to threshold
2. Na+ channels activate and enters the axon (depolarization)
3. Na+ channels inactivate, K+ channels open and exits the cell (repolarization)
4. Na+ channels return to resting state, repolarization continues
5. the axolemma may hyperpolarize before K+ channels return to resting state, axolemma returns to RMP
116
refractory period definition and the types
neurons are limited to how quickly they can fire another AP
- absolute refractory period
- relative refractory period
117
absolute refractory period
no amount of stimulus can produce another AP
- Na+ channels are activated then temporarily inactivated when K+ channels are activated
118
relative refractory period
only a strong stimulus can produce another AP
- K+ channels are still open
119
Action potential propagation steps
(4 steps)
1. the axolemma depolarizes to threshold due to local potentials
2. as Na+ channels activate, an AP is triggered and spreads down the axon
3. the next section of the axolemma depolarizes to the threshold and fires another AP as the previous section repolarizes
4. the current continues to move down the axon
120
continues conduction
in unmyelinated axons, every section of the axolemma from the trigger zone to the axon terminal must propagate an AP
- slower conduction speed as the axon depolarizes
121
types of action potential propagation
- continuous conduction
- saltatory conduction
122
saltatory conduction
in myelinated axons where insulating properties of myelin sheath increase efficiency and speed of signal conduction
- AP only at the nodes of ranvier
- jumps from one node to the next
123
what are two things that influence the speed of AP propagation
- myelinated axons: myelination lowers resistance to conduction by insulating the membrane
- axon diameter: axons with larger diameter have faster conduction speeds (larger axons have lower resistance to conduction)
124
what are the steps of action potentials down the axon
(3 steps)
1. local potential: soma
2. action potential: trigger zone (axon hillock)
3. action potential propagation: axon
125
where does a presynaptic neuron synapse with
- post synaptic neuron
- other target cells
126
termination of the synaptic transmission at the chemical synapse
the neurotransmitter must be removed
