Midterm #2 Flashcards
1
Q
How many skeletal muscles are there in the human body?
A
More than 600
2
Q
What percentage of body weight do skeletal muscles contribute?
A
40-60% of total body weight
3
Q
What are the main functions/purposes of skeletal muscle?
A
1) Force Generation
2) postural support
3) heat production during cold stress
4
Q
Muscles that decrease joint angles are called?
A
Flexors
5
Q
Muscles that increase joint angles are called?
A
Extensors
6
Q
What separates and holds skeletal muscle in place?
A
Fascia
7
Q
What are the 3 layers of connective tissue(fascia) in skeletal muscle? Where is each one located?
A
1) Epimysium - surrounds the entire muscle
2) Perimysium - surrounds individual muscle bundles
3) Endomysium - Surrounds each muscle fibre
8
Q
What is one distinct difference between skeletal muscle from other types?
A
They are multinucleated
9
Q
What is the cell membrane that surrounds the muscle fibre?
A
Sarcolemma
10
Q
What is the purpose of the sarcolemma?
A
usual membrane functions + assists in the transmission of neural impulses
11
Q
What are satellite cells and what do they do?
A
undifferentiated cells that are predicted to play a key role in muscle growth and repair
12
Q
What is the myonuclear domain? Why is this important for muscle growth?
A
This is the ratio of cell volume per nucleus. This is important because a nucleus can only sustain the necessary gene expression(production of proteins) for a limited area. Therefore as muscle grows, more nuclei are made. And vice versa
13
Q
What are myofibrils?
A
Myofibrils contain the contractile proteins.
14
Q
What makes up myofibrils?
A
Actin and myosin
15
Q
What makes up thick filaments?
A
Myosin
16
Q
What makes up thin filaments?
A
Primarily actin plus troponin and tropomyosin.
17
Q
Myofibrils can be further divided into…
A
Sarcomeres
18
Q
What are sarcomeres?
A
The smallest functional unit of a muscle.
19
Q
What separates sarcomeres?
A
The Z line or Z disk
20
Q
What is the A band?
A
There the thick filaments(myosin) are located
21
Q
What is the I band? What happens during muscle contraction?
A
Where the light filaments(actin) are and not overlapping myosin. Essentially the space between the thick filaments.
The I band decreases in size due to the increasing overlap of myosin and actin.
22
Q
What is the H zone? What happens during contraction?
A
This is the zone where there is only myosin, no actin. This region will decrease in size as myosin pulls actin towards the m-line creating more overlap of the two filaments.
23
Q
What is the sarcoplasmic reticulum?
A
a network of membranous channels within the sarcoplasm. The SR is the storage site for Ca.
24
Q
Why is the Ca in the sarcoplasmic reticulum important?
A
Becasue the Ca release is required for muscle contraction.
25
What is the transverse tubule?
A membranous channel that extends from the sarcolemma completely through the muscle fibre using channels called terminal cisternae. The T-tubules are responsible for transmitting nerve impulses throughout the whole muscle fibre to permit the release of Ca from the sarcoplasmic reticulum.
26
What is the anatomical relationship between the sarcoplasmic reticulum and the transverse tubules?
These two systems bring together the dihydropyridine receptor and the ryanadine receptor.
27
What is the dihydropyridine receptor?
resides in the transverse tubules and allows the ryanadine receptor to release Ca. The dihydropyridine receptor does not directly release Ca.
28
What is the ryanadine receptor?
Resides in the terminal cisternae and after being stimulated by the dihydropyridine receptor, the ryanadine Ca channel will open causing Ca to be released from the sarcoplasmic reticulum triggering muscle contraction.
29
What type of neurons innervate skeletal muscle?
Motor neurons
30
What is a motor unit?
The nerve and all muscle fibres it innervates
31
What is the site where a motor neuron and a muscle cell meet called?
Neuromuscular junction.
32
At the site of a neuromuscular junction, there is a pocket within the sarcolemma. What is this pocket called?
The synaptic cleft
33
T or F - The motor neuron makes direct contact with the muscle cell.
False, The motor neuron and muscle cell are separated by the synaptic cleft.
34
Since there is no contact, how does the motor neuron stimulate the muscle cells?
By sending the neurotransmitter, ACh, which diffuses across the synaptic cleft and binds with the receptors on the motor end plate.
35
What happens when ACh binds to the motor end plate?
Causes an increase in permeability to sodium resulting in a depolarization called the end-plate potential.
36
T or F - End-plate potentials are always large enough to exceed the threshold.
True, EPPs are always large enough to start the contractile process.
37
How does training positively adapt the neuromuscular junction?
Training increases the NMJ size which increases the number of synaptic vesicles and ACh receptors. These changes allow for better stimulation of the muscle from the motor neuron.
38
What breaks down ATP that is used for muscle contraction? Where is this structure location?
Myosin ATPase; located on the myosin head.
39
How much does one cycle of the "power stroke" shorten the muscle in the percentage of the muscle's resting length?
Typically about 1% of the muscles resting length.
40
What is excitation-contraction coupling?
The act of depolarization of a muscle(excitation) that results in the contraction of the muscle.
41
State the steps of muscle excitation.
1) Impulse arrives at NMJ
2) ACh is released and diffused across the synaptic cleft
3) ACh causes an end-plate potential that depolarizes the muscle cell
4) Depolarization travels through T-tubules and causes release of Ca from the sarcoplasmic reticulum
5)
42
State the steps of contraction
1) Ca binds with troponin
2) The binding of Ca causes a position change in tropomyosin
3) the change to tropomyosin opens the myosin binding site on actin
4) Myosin binds with actin after hydrolyzing ATP.
5) Fresh ATP will bind to myosin releasing and cocking for next attachment
43
Steps of Muscle Relaxation
1) The impulse for muscle contraction is stopped
2) Ca is pumped back into the sarcoplasmic reticulum
3) Ca releases from troponin moving tropomyosin back in position to cover actin not allowing myosin to bind to actin
4)
44
What is muscle fatigue?
a reduction in muscle power output. This can lead to reduced force generation and shortening velocity.
45
What is the most likely causes of muscle fatigue?
Changes to the central nervous system or peripheral factors within the skeletal muscle.
46
How does Hydrogen Ions cause muscle fatigue?
H+ will bind to troponin where Ca is supposed to bind. This prevention will not allow the positional change of tropomyosin which does not allow muscle contraction to initiate.
47
What causes muscle fatigue in prolonged, moderate exercise?
The build-up of free radicals which changes the myosin head contractile apparatus and depletion of glycogen.
48
What is the more proven reason for muscle cramps caused by exercise? What could cause this?
Increased excitability of motor neurons. This causes uncontrolled and involuntary contractions. This could be caused by depressed signals from the GTO which sends inhibitory signals to the CNS.
49
Why does dehydration and electrolyte imbalance not cause muscle cramps?
If the body was dehydrated or had an electrolyte imbalance, the whole body would cramp up instead of just a single muscle. This is because dehydration and electrolytes affect the whole body, not just one muscle.
50
What are the biochemical characteristics of muscle function?
1) Oxidative capacity
2) type of myosin isoform(differences in myosin ATPase activity)
3) the abundance of contractile protein within the fibre
51
What determine oxidative capacity of a muscle fibre?
The number of mitochondria, number of capillaries surrounding the muscle, and the amount of myoglobin within the fibre.
52
What are the 4 contractile properties of muscle fibre that determine their performance?
1) maximal force(based on the number of myosin and actin filaments per cross-sectional area) - more myosin heads to attach and generate force
2) speed of contraction - based on cross-bridge cycling speed and number of myosin ATPases
3) maximal power output - determined by force generation and shortening velocity(power = force x shortening velocity
4) efficiency of contraction - the amount of energy used to produce 'x' amount of force(energy used/force)
53
What are the functional characteristics of Type 1 fibres?
High mitochondrial volume, more capillaries, high myoglobin volumes, high resistance to fatigue.
Slower shortening velocity and lower myosin ATPase activity and contain less actin and myosin per cross-sectional area. Lastly, type 1 are more efficient due to the high oxidative potential.
54
What are the functional Characteristics of Type 2 fibres?
low mitochondrial volume, limited capacity for aerobic metabolism, low/less resistance to fatigue. Rich in glycolytic enzymes.
Type 2 have faster shortening velocities, higher specific force, andhigher power output.
55
T or F - Muscle fibres will only exhibit one type of muscle fibre.
False, muscle fibres are typically blended between the 3 different types typically having more of one kind than the other 2 showing those characteristics more.
56
T or F - Sedentary adults possess ~50% slow oxidative(type 1) fibres.
True.
57
What is muscle action?
Describes to process of muscle movement(shortening vs lengthening)
58
What is dynamic exercise?
exercise that involves movement of body parts
59
What is the difference between concentric and eccentric actions?
concentric - the shortening of a muscle
eccentric - the lengthening of a muscle when force is produced
60
What is a muscle twitch?
When a muscle is given only a single stimulus
61
What is the difference between summation and Tetanus?
Summation - neural stimulations are increased and the muscle does not have time to relax between stimuli. The force produced is additive.
Tetanus - Stimuli is further increased to the point where contractions are blended together into a single, sustained contraction. These contractions continue until stimulation stops or muscle fatigues.
62
Why is the shortening velocity faster in type 2 fibres?
This is because the sarcoplasmic reticulum releases Ca at a faster rate and fast twitch fibres have a higher ATPase activity.
63
How is force regulated in muscle?
1) number and type of motor units recruited.
2) the initial length of a muscle
3) the nature of the neural stimulation
4) the contractile history of the muscle
64
How does initial length of.a muscle affect force production?
There is an optimal length for a muscle to start contraction at due to how where the actin is in relationtion to myosin. If you were to strethc the muscle to its limit, you will reach a point where myosin has no actin to bind to for contraction. So initial length is important due to the amount of binding sites available for myosin.
65
What is postactivation potentiation? Why is this important?
postactivation potentiation(PAP) is the increase in muscle force production following a bout of non-fatiguing, submaximal muscle contractions.
PAP results in phosphorylation of the muscle fibres which increases muscle sensitivity to Ca. This results in increased actin-myosin interaction
66
T or F - Maximum shortening velocity is greatest at the highest force.
False, maximum shortening velocity is greatest at the lowest force. Force is the resistance acting against the muscle.
67
What are the primary functions of the cardiovascular system?
Deliver adequate amounts of O2 and remove wastes from body tissues
68
What is cardiac output?
The amount of blood pumped by the heart, per minute.
CO = HR x SV
69
how does the heart meet oxygen demands during exercise?
1) increasing cardiac output
2) redistribution of blood flow from inactive organs to the active skeletal muscles
70
T or F - The Circulatory system is an open loop circuit.
False, the blood is brought back by the veins making it a continuous cycle. This makes it a closed circuit.
71
T or F -Ateries carry oxygenated blood from the heart and Veins carry deoxygenated blood to the heart.
False - arteries carry blood away from the heart and veins carry blood to the heart.
Does not have to do with O2 levels in the blood, just the direction of blood flow.
72
Why does is the left ventricle larger than the right ventricle?
This is because the right ventricle is only pumping to the lungs which is close by requiring only small pressure. The left ventricle is pumping to the entire body requiring high pressure/force to get the blood throughout the entire body.
73
What are the 4 valves and their locations in the heart?
Tricupsid(right atrioventricular valve) - between the right atrium and ventricle.
Bicuspid(left atrioventricular valve) - between the left atrium and ventricle.
Pulmonary semilunar valve - between the right ventricle and pulmonary artery.
Aortic semilunar valve - between the left ventricle and aorta
74
What are the 3 layers of the heart?
Epicardium - outermost layer
Myocardium - muscular, middle layer
Endocardium - inner layer
75
What is the role of the myocardium?
To generated force and pump blood
76
T or F - Individual coronary veins drain into the right atrium.
False, they merge then drain into the coronary sinus which then drains into the right atrium.
77
What is the cause of a heart attack?
A blockage in the coronary arteries.
78
What is the purpose of intercalated disks within cardiac muscle cells?
They permit the transmission of electrical impulses from one fibre to another.
79
What is systole?
This is the phase where the ventricles contract.
80
What is diastole?
This is the phase where the ventricles relax and fill with blood.
81
How much blood do the ventricles eject during systole?
About 2 thirds of the blood that was in them.
82
How long does a typical cardiac cycle last and how long for each phase?
Cardiac cycle = 0.8s
Systole = 0.3
Diastole = 0.5
83
How do the timing of the phases change during exercise?
time spent in Diastole is greatly reduced while systole is barely reduced.
84
When do the semilunar valves open?
When the pressure within the ventricles exceeds the pressure in the pulmonary artery and aorta.
85
When is systolic and diastolic blood pressure recorded?
Systolic blood pressure is the pressure generated as blood is ejected from the heart.
Diastolic blood pressure is the pressure during ventricular relaxation. Reduced BP occurs here.
86
What is mean arterial pressure?
The average pressure during a cardiac cycle.
87
Why is mean arterial pressure hard to calculate during exercise?
Because you have to know how long the 2 phases last since they do not last equal amounts of time.
88
What factors affect Mean arterial pressure?
1) Cardiac output
2) total vascular resistance
89
What are baroreceptors and where are they located?
These are pressure receptors and are sensitive to pressure changes in the aorta and carotid arteries.
90
What controls the sympathetic nervous system activity to the heart? Where is it located?
The cardiovascular control centre which is located in the medulla oblongata
91
What is the pathway of the electrical current of the heart?
SA node -> AV node -> AV bundle -> left/right bundle branches -> purkinje fibres
92
What is an ECG?
What are the different components of an ECG?
Electrocardiogram
P wave - depolarization of the atria
QRS complex - depolarization of the ventricles
T wave - ventricular repolarization
93
How does the parasympathetic nervous system and sympathetic nervous system affect heart rate?
PNS - release ACh at the nodes decreasing HR. Therefore the PNS is what slows the heart down.
SNS - releases norepinephrine that binds to beta receptors which increases HR and force of myocardial contraction.
94
T or F - Sympathetic activity is what initially increases HR.
False, it is the parasympathetic withdrawal that increases HR initially. Once reaching about 100bpm, then the sympathetic outflow will occur. This will start during moderate-intensity exercise.
95
What is heart Rate Variability?
Refers to the variation i the time between heartbeats.
96
T or F - a wide variation in resting heart rate variation is considered to be a good index of a healthy balance between parasympathetic and sympathetic nervous systems.
True, this variation shows that both systems are working together. As exercise increases, HRV will decrease as the sympathetic system takes over
97
What are the three factors that regulate stroke volume?
1) end-diastolic volume
2) average aortic pressure
3) the strength of ventricular contraction
98
How does aortic pressure affect stroke volume?
Because the aorta acts as a barrier to the ejection of blood as the ventricular pressure needs to exceed aortic pressure.
99
What are the factors affecting end-diastolic volume?
1) venoconstriction
2) Muscle Pump
3) Respiratory Pump
100
What is hematocrit?
percentage of the blood that is composed of cells.
101
Blood flow = ?
Blood flow = Difference in pressure / resistance.
102
What is the major contributor to increasing resistance? Where is this resistance located?
radius of the vessel.
The resistance is located in the arterioles.
103
What are the methods the body uses to deliver increased amounts of O2 to the skeletal muscles during exercise?
1) increased cardiac output
2) redistribution of blood flow from inactive organs to active skeletal muscles
