Test 2 Flashcards
(158 cards)
1
Q
What are the three different muscle types?
A
Skeletal, cardiac, and smooth
2
Q
What are the characteristics of cardiac muscle?
A
Located in the heart, part of the autonomic nervous system, and is irregularly striated
3
Q
What are the characteristics of skeletal muscle?
A
They are attached to bone, part of the somatic nervous system, and are striated.
4
Q
What are the characteristics of smooth muscle?
A
They are found around hollow organs, part of the autonomic nervous system, and are not striated.
5
Q
Muscles attached to long bones are in ______ pairs.
A
Antagonistic
6
Q
What is a flexor muscle?
A
Muscle that decreases the joint angle when it contracts.
7
Q
What is an extensor muscle?
A
Muscle that increases the joint angle when it contracts.
8
Q
What are tendons?
A
Connective tissue attaching muscle to bone.
9
Q
How do skeletal muscles work in antagonistic pairs?
A
One muscle in the pair contracts and changes the joint angle, while the other relaxes. When the other muscle contracts and changes the joint angle in the opposite direction, the initial muscle relaxes.
10
Q
Describe the microscopic characteristics of skeletal muscle.
A
Muscle fibers have elongated shape, and they contain multiple nuclei. Maintain 30-40% of total body weight.
11
Q
Why does skeletal muscle appear striated?
A
Because of the abundance of actin and myosin filaments of the sarcomeres. The filaments slide past each other during muscle contraction.
12
Q
What is a myofibril?
A
Cellular organelle specialized for generating force and contraction.
13
Q
What are thin filaments composed of?
A
Composed of actin, the contractile protein. Regulated by proteins tropomyosin and the troponin complex.
14
Q
What is a thick filament?
A
Comprised of myosin and binds to actin. Has globular heads capable of binding to actin.
15
Q
What is the Sliding Filament Hypothesis?
A
- Thick & thin filaments capable of sliding past each other 2. Each group of filaments within a sarcomere slides as a unit 3. Many shortened sarcomeres lead to shortening of muscle.
16
Q
What is the neuromuscular junction?
A
Synapse between motor neuron and skeletal muscle fiber.
17
Q
True or False: Neuromuscular junctions have inhibitory signals.
A
FALSE. Neuromuscular junctions never have inhibitory signals - they only have excitatory signals.
18
Q
What is botulinum toxin?
A
Produced by bacterium, Clostridium botulinum, in improperly preserved food. Blocks release of acetylcholine.
19
Q
What is botulism?
A
Deadly food poisoning caused by clostridium botulinum.
20
Q
What is Botox?
A
Used in cosmetic injections. LD(50) ~ 1-2 ng/kg. (A few teaspoons could wipe out the world population)
21
Q
What is curare?
A
Produced by Chondodendron tomentosum; South American arrow poison that blocks cholinergic receptors on motor end plate.
22
Q
What is succinylcholine?
A
Short-term paralysis; only depolarizing skeletal muscle relaxant. It binds to post-synaptic cholinergic receptors.
23
Q
What are organophosphates?
A
Inhibit AChesterase; found in insecticides and nerve gases (sarin).
24
Q
What are the steps of the Inhibition of AChesterase?
A
- AChesterase breaks down ACh in the cleft of NMJ 2. AChesterase terminates action of ACh 3. Involuntary twitching followed by paralysis and death.
25
What is myasthenia gravis?
Autoimmune destruction of cholinergic (nicotinic) receptors on motor end plate. ACh release is normal but EPPs are reduced; leads to muscle weakness and fatigue.
26
What is excitation-contraction coupling?
1. AP spreads from motor end plate along muscle fiber 2. AP travels into cell interior along transverse tubules. 3. Sarcoplasmic reticulum releases Ca2+ 4. Ca2+ binds to troponin 5. Troponin 'pushes' tropomyosin 6. Myosin moves along actin filament.
27
What is the cross-bridge cycle?
1. Attach - energized myosin heads bind to actin 2. Pull - myosin heads tilt forward (power-stroke) 3. Release - ATP binding detaches cross-bridge 4. Recharge - myosin heads flips back to original conformation.
28
List the functions of ATP in skeletal muscle contraction.
1. Hydrolysis of ATP by the Na+/K+-ATPase maintains the gradients and allows the membrane to produce and propagate action potentials 2. Hydrolysis of ATP by the Ca2+-ATPase provides energy for active transport of calcium ions into the reticulum 3. Hydrolysis of ATP of myosin-ATPase energizes the cross-bridges, providing energy for force generation 4. Binding of ATP to myosin dissociates cross-bridges bound to actin.
29
What are the requirements for contraction?
Calcium ions & ATP.
30
What is rigor mortis?
ATP is depleted after death, so body becomes rigid; begins 4 hours after death and lasts until decomposition.
31
What is isotonic contraction?
Muscle develops tension and shortens. Tension > load.
32
What is isometric contraction?
Muscle develops tension but does not shorten. Load >= tension.
33
What is recruitment?
Increasing muscle tension by increasing the number of muscle fibers contracting.
34
What is summation?
Unfused tetanus; repeated, additive contraction of muscle without full relaxation.
35
What is tetanus?
Smooth, sustained contraction of skeletal muscle.
36
Who are Hugh Huxley and Jean Hanson?
Performed SEM on muscle under different conditions; they observed that sarcomeres shorten during contraction.
37
List the components of the neuromuscular junction.
Acetylcholine is the neurotransmitter, only EPPs are graded potentials, and the threshold is one EPP.
38
What is tropomyosin?
Blocks binding sites on actin.
39
What is troponin?
Holds tropomyosin in its inhibitory position.
40
What are the steps of relaxation?
1. Membrane of SR contains primary active transport system for Ca2+ (Ca2+ ATPase) 2. Ca2+ pumped back into SR 3. Ca2+ decreases, dissociates from troponin 4. Tropomyosin blocks binding sites on actin for myosin ATPase 5. No more cross bridges, muscle returns to resting length 6. Ca2+ pulse lasts ~100-200 ns.
41
An increase in stimulus intensity leads to ____
an increase in force of contraction.
42
An increase in stimulus frequency results in _____
an increase in muscle tension (recruitment).
43
What is fatigue?
Inability to maintain muscle tension in spite of continued stimulation; due to depletion of nutrients and ATP.
44
True or False: Nerve conduction and action potentials are normal in a state of fatigue.
True.
45
What is psychological fatigue?
Decreased reactivity of cerebral cortex.
46
An increase in length leads to a(n) _____ in active tension.
Increase.
47
True or False: Velocity of maximal muscle contraction is positively correlated to load.
FALSE. Velocity of maximal muscle contraction is INVERSELY PROPORTIONAL to load.
48
What is creatine phosphate?
Immediate reserve of high-energy phosphate groups; depleted in ~ 30 seconds.
49
What is creatine kinase?
Can catalyze reaction in both directions; acts as a buffer in the breakdown of creatine phosphate into creatine and ATP.
50
What happens after muscle contraction?
1. ATP formation exceeds consumption 2. Creatine phosphate levels increase 3. Resting creatine phosphate levels are 5 X ATP levels.
51
What is oxidative phosphorylation?
Breakdown of nutrients provides energy to phosphorylate ADP; requires oxygen.
52
What are the principle fuels in muscle?
Fatty acids.
53
Oxidative phosphorylation is _____% of the energy in maximal exertion.
<=70.
54
What is glycolysis?
Breakdown of carbohydrates; anaerobic, used during strenuous exercise.
55
Is glycolysis an efficient way to make energy?
NO. It is relatively inefficient; glycolysis produces lactic acid, which contributes to muscle fatigue. It only makes a net 2 ATP.
56
When is oxidative phosphorylation best used for energy consumption?
During moderate exercise.
57
When is creatine phosphate best used for energy consumption?
During muscle contraction.
58
What are slow-twitch fibers?
Slow, oxidative; develop tension relatively slowly and fatigue slowly. Have a high capacity for aerobic metabolism.
59
What are fast-twitch fibers?
Fast, glycolytic; develop tension rapidly and fatigue rapidly. Adapted for anaerobic metabolism.
60
How can skeletal muscles be classified?
Basis of speed of contraction, and primary source of energy.
61
What are fast-oxidative fibers?
Fast twitch but high oxidative activity; intermediate in most properties.
62
What type of muscle fibers do very active muscles mostly contain?
Fast-twitch fibers (muscles of eyes and fingers).
63
What type of muscle fibers do postural muscles mostly contain?
Slow-twitch fibers (muscles of the back).
64
What have twin studies showed us about muscle fiber types?
Fiber type is genetically determined, and training does not change dominant type.
65
What is muscle atrophy?
Decrease in muscle mass and strength. Causes: Disuse, starvation, aging, and disease.
66
What is muscular dystrophy?
Progressive degeneration of muscle in young children. Most commonly inherited, only affecting males.
67
What is dystrophin?
Protein deficient; prevents damage to muscle cell membrane during contraction.
68
What is muscle hypertrophy?
Increase in muscle mass and strength; results from exercise and an increase in fiber diameter due to addition of myofibrils.
69
Does muscle hypertrophy result in a change in number of muscle fibers?
No.
70
What are the effects of high intensity, short duration exercise?
1. Increase in fiber diameter (FT fibers) 2. Increased number of glycolytic enzymes in fast-twitch fibers 3. No improvement in endurance.
71
What are the effects of low intensity, long duration exercise?
1. Little change in fiber diameter 2. Increases myoglobin content in all fiber types 3. Increased number of mitochondria in slow-twitch fibers 4. Increased endurance capacity.
72
What is myostatin blockade?
Myostatin inhibits muscle growth.
73
What is smooth muscle?
Mostly in walls of hollow organs and tubes; under control of the autonomic nervous system and circulating hormones.
74
What is the muscle fiber appearance of smooth muscle?
Spindle-shaped and shorter in length; have a smaller diameter, have only one nucleus, lack striations, and are in a circular arrangement around blood vessels.
75
True or False: Thick and thin filaments of smooth muscle are different than those in skeletal muscle.
FALSE. Thick and thin filaments of smooth muscle are the same as in skeletal muscle.
76
What are dense bodies?
Not present in skeletal muscle; connecting points between thin filaments.
77
Why is smooth muscle arranged diagonally?
Lots of overlap allows smooth muscle fibers to develop tension over a wide range of lengths.
78
Explain contraction of smooth muscle.
Contraction is caused by increased Ca2+ level in cytoplasm. Most Ca2+ enters from the extracellular fluid through Ca2+ channels in the cell membrane.
79
What is calmodulin?
Regulatory protein; calcium-binding protein.
80
What is a calcium pump?
Slowly removes Ca2+.
81
What is myosin ATPase?
Activity is low; develops tension slowly.
82
True or False: Smooth muscle contraction is graded.
True.
83
What are latch bridges?
Maintain tension with high efficiency.
84
What is the latch state?
Rigor-like state without movement caused via dephosphorylation of attached myosin head; each latch state maintains tension without using much ATP.
85
What is intrinsic activity?
Slow wave rhythm of membrane potential, accompanied by mild contraction and relaxation.; gradual depolarization and repolarization.
86
How do hormones affect smooth muscles?
They bind to hormone receptors; oxytocin binds to receptor on uterine muscle cells and induces contractions during labor.
87
What is the autonomic nervous system?
Subdivision of the motor division of PNS; innervated cardiac muscle, smooth muscle, and glands.
88
What is a preganglionic neuron of the motor pathway?
Cell body in the CNS; axon terminal in PNS (autonomic ganglion).
89
What is a postganglionic neuron of the motor pathway?
Cell body in ganglion; axon terminal in effector organ.
90
What is the sympathetic division of the ANS?
Reaction to emergencies: 'fight or flight'.
91
What are the effects of the activation of the sympathetic division?
Increased heart rate, increased blood glucose, increased blood flow to skeletal muscles, increased sweating, and dilation of pupils.
92
What are the neurotransmitters of the sympathetic division?
Preganglionic neurons release Acetylcholine and postganglionic neurons release norepinephrine. Norepinephrine binds to adrenergic receptors on effector organs.
93
Where do sympathetic cell bodies originate?
The thoracic and lumbar spinal cord.
94
What is the adrenal medulla?
Innervated by preganglionic sympathetic neurons; secretes epinephrine and effects are similar to norepinephrine.
95
What is the parasympathetic division of the autonomic nervous system?
Vegetative functions; 'rest and digest'.
96
What are the effects of the parasympathetic division?
Decreased heart rate, increased blood flow to internal organs, contraction of smooth muscle in intestine, and constriction of pupils.
97
Where do parasympathetic division cell bodies originate?
In the brainstem or sacral spinal cord.
98
Does the sympathetic or parasympathetic nervous system innervate the heart?
Both divisions innervate the heart.
99
What are the neurotransmitters of the parasympathetic division?
Preganglionic neurons and postganglionic neurons release acetylcholine; ACh binds to cholinergic receptors on effector organs.
100
What are single-unit smooth muscles?
Respond to stimuli as a single unit because cells are connected by gap junctions (uterus, G.I. tract, bladder walls).
101
What are multi-unit smooth muscles?
Cells respond to stimuli independently and contain few gap junctions (blood vessels, urinary tract, and airways).
102
What is metabolic rate?
Rate at which the body uses energy.
103
What are the influencing factors of metabolic rate?
Age, gender, sleep, food intake, hormones, and physical activity.
104
What is anabolism?
Reactions in which simple molecules combine to form more complex ones; require metabolic energy.
105
How does the process of anabolism store different forms of energy?
Glucose is stored as glycogen, fatty acids are stored as fat.
106
What is catabolism?
Breakdown of complex molecules to release metabolic energy; glucose, amino acids, and fatty acids are broken down by separate but interrelated pathways.
107
What percentage of released energy is captured as ATP?
38-44.
108
What is motility?
Movement of materials through the digestive tract.
109
What is secretion?
Secretion of digestive juices into the tract.
110
What is digestion?
Breakdown of food into smaller units.
111
What is absorption?
Transport of the products into the blood.
112
What is excretion?
Elimination of waste.
113
What is the lumen?
Hollow portion; outside of the body. Very hostile environment.
114
What is the stomach?
Very acidic; kills most bacteria.
115
What are ulcers?
Destruction of stomach wall by acid. Typically caused by helicobacter pylori.
116
What are villi?
1 mm long finger-like projections; large surface area and contains capillaries and lymph vessels (lacteals).
117
What are goblet cells?
Secrete mucus; epithelium replaced every five days.
118
What is the submucosa?
Connective tissue; contains blood vessels and autonomic nerve fibers.
119
What is muscularis externa?
Inner circular layer, outer longitudinal layer; autonomic nerve fibers responsible for motility.
120
What is serosa?
Connective tissue wrapping.
121
What is peristalsis?
Waves of smooth muscle contraction; stimulated by parasympathetic activity and inhibited by sympathetic activity.
122
What is segmentation?
Alternating contraction and relaxation of different segments of the digestive tract; increases time for absorption of nutrients.
123
What is a sphincter?
Tight ring of muscle that stops the movement of materials.
124
What is heartburn?
Inappropriate opening of the lower esophageal sphincter.
125
What is mucus?
Secretes by goblet cells; for protection and lubrication.
126
Where do glands secrete digestive enzymes and other substances to?
The lumen.
127
What are salivary glands?
Produce 1-2 L of saliva per day; water, mucus, salivary amylase, lipase, and lysozyme (antimicrobial).
128
What is the pancreas?
Secretes digestive enzymes and bicarbonate into the small intestine.
129
What is a sphincter?
A tight ring of muscle that stops the movement of materials.
130
What causes heartburn?
Inappropriate opening of the lower esophageal sphincter.
131
What is mucus?
Secreted by goblet cells; for protection and lubrication.
132
Where do glands secrete digestive enzymes and other substances?
The lumen.
133
What do salivary glands produce?
1-2 L of saliva per day; water, mucus, salivary amylase, lipase, and lysozyme (antimicrobial).
134
What does the pancreas secrete?
Digestive enzymes and bicarbonate ion to neutralize stomach acid for entrance to small intestine.
135
What is the function of the liver?
Produces bile.
136
What is the function of the gallbladder?
Storage of bile.
137
List the pancreatic enzymes.
Amylase, Trypsin, Nuclease.
138
What do duct cells produce?
Bicarbonate to neutralize HCl.
139
Who is William Beaumont?
"Father of American Physiology;" studied digestion as primarily a chemical process.
140
What do brush border enzymes do?
Hydrolyze disaccharides into monosaccharides.
## Footnote
Sucrose -> glucose + fructose; Maltose -> glucose + glucose; Lactose -> glucose + galactose.
141
Can cellulose be digested by humans?
No.
142
What is sucralose?
A no-calorie artificial sweetener.
143
What is the intrinsic factor of proteins?
Absorption of B12 in the small intestine.
144
What do epithelial cells secrete?
HCl (parietal cells) and pepsinogen (Chief cells).
145
What is a zymogen?
A proenzyme; inactive precursor of an enzyme.
146
What are the parts of the stomach?
Body and antrum are large open regions, fundus is the dome-shaped top section, and gastric glands.
147
What stimulates the secretion of HCl and pepsinogen?
Acetylcholine from the vagus nerve and gastrin in the blood.
148
Where does the digestion of fats occur?
Entirely within the small intestine.
149
What are bile salts?
Produced by the liver; help disperse lipid droplets into much smaller droplets; increases surface area.
150
What does lipase do?
Secreted by the pancreas; catalyzes hydrolysis of fatty acids from the first and third carbons of glycerol.
151
What are fat substitutes?
Olestra; cannot be absorbed by the intestinal system.
152
Where does absorption mainly take place?
The small intestine.
153
Where is aspirin and alcohol absorbed?
The stomach.
154
Where are glucose and amino acids absorbed?
Across the intestinal epithelium by secondary transport.
155
What is diarrhea?
Results from excess intestinal motility; loss of fluid and nutrients leads to dehydration.
156
True or False: Digestive system plays a major role in excretion.
FALSE. The digestive system does NOT play a major role in excretion.
157
What are the functions of the liver?
Production of bile, storage of nutrients, synthesis of new molecules, destruction of harmful substances.
158
What is the hepatic portal system?
Main gastrointestinal system absorption pathway.
