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BIOL 310 > Exam #3 > Flashcards

Exam #3 Flashcards

1
Q

If small generator potentials reach a critical threshold near -40mV…

A

Na+ channels and K+ channels will sense the voltage change and open. Causing an all or none action potential to fire.

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2
Q

Action potentials travel to the synapse and lead to…

A

The release of neurotransmitter.

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3
Q

The junction between the terminal branch of the nerve fiber and muscle fiber is called…

A

Neuromuscular junction.

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4
Q

What areas of the brain contribute to the program of voluntary movement of muscles?

A

Primary motor cortex

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5
Q

What areas of the brain contribute to the execution of muscle voluntary movement?

A

Pyramidal tract

Motor neuron

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6
Q

What areas of the brain provide feedback for the execution of muscle voluntary movement?

A 
Sensory systems
Cerebellum
Thalamus
Basal nuclei
Brainstem
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7
Q

The primary motor cortex resides in…

A

Precentral gyrus

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8
Q

When you stimulate the primary motor cortex (motor homunculus) what is the result?

A

Twitch in the contralateral side.

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9
Q

What are upper motor neurons?

A

Reside in the primary motor cortex.

Large betz cells that send long axons down towards the spinal cord.

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10
Q

How does the basal ganglia motor loop help select and initiate movement?

A

Focuses activity from widespread regions onto the thalamus, then back onto the motor cortex (areas 4 and 6).

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11
Q

The basal ganglia consists of…

A

Caudate, putamen, and globus pallidus.

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12
Q

Lesions of the caudate (in the basal ganglia) results in…

A

Huntington’s disease.

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13
Q

Lesions of the substantia nigra (in the basal ganglia) results in…

A

Parkinson’s disease

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14
Q

What is the cerebellum’s function?

A

Coordinates muscle movement through direction, timing, and force.
Compares intended movement coming from the motor cortex with actual movement sensation (proprioception) coming in from the joints and muscles.

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15
Q

What is the pathway of voluntary movement in the CNS?

A
  1. Motor cortex axons descend through medulla.
  2. Cross over/decussate.
  3. Descend pyramidal tract.
  4. Synapse onto alpha motor neurons in the ventral horn of the spinal cord.
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16
Q

Action potentials in ___________ lead to muscle contraction.

A

Alpha motor neurons

the axons branch and innervate multiple muscle fibers

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17
Q

Loss of motor neurons either sporadically or inherited causes…

A

Amyotrophic Lateral Sclerosis (ALS)
Motor neurons degenerate and die leading to muscle atrophy.
Brain and cognition is still intact but muscle cannot be commanded to move.

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18
Q

Simple reflex skeletal muscle movement is mediated at…

A

The spinal cord level.

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19
Q

The 5 parts of a reflex arc are:

A
  1. Receptor - muscle spindle
  2. Afferent neuron - sensory dorsal root ganglion.
  3. CNS - spinal cord
  4. Efferent neuron - alpha motor neuron
  5. Effector - muscle
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20
Q

What do weak or absent reflexes indicate?

A 
Damage is done to the spinal cord at the reflex site.
Sensory nerve damage
Motor nerve damage
Spinal cord damage
Tendon/muscle damage
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21
Q

What do exaggerated reflexes indicate?

A

Damage is usually done below the site of spinal cord damage as the brain generally inhibits downstream alpha motor neurons.

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22
Q

What are skeletal muscles connected to?

A

Bones via tendons.

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23
Q

What are bundles of long multinucleated cells?

A

Myofibers

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24
Q

Inside myofibers are an extensive network of intracellular filament proteins called…

A

Myofibrils

intracellular proteins = actin and myosin

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25
Q

What is the origin of skeletal muscles?

A

Connection to stationary bone.

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26
Q

What is the insertion of skeletal muscles?

A

Connection to movable bone.

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27
Q

Isotonic muscle contractions result in…

A

Muscle SHORTENING.

The load is easily lifted.

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28
Q

Isometric muscle contractions result in…

A

Tension WITHOUT muscle shortening.
The load is too heavy to lift.
The sarcomere still shortens but series elastic elements (tendon) lengthen.

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29
Q

What neuron makes synapses with skeletal muscle cells to help the muscle contract?

A

Alpha motor neurons.

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30
Q

How do alpha motor neurons help with muscle contraction?

A

Release ACh onto the target muscle, which binds to the Nicotinic ACh Receptor.

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31
Q

The neuromuscular junction illustrated the precise alignment of…

A

Presynaptic active zones with postsynaptic nACh receptors.

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32
Q

T or F: Nicotinic Acetylcholine Receptor is a g-protein coupled channel.

A

FALSE

It is a ligand gated ion channel.

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33
Q

What happens once 2 acetylcholine molecules bind to the nicotinic receptor?

A

The receptor conformation changes, it channel opens, Na+ flows in, and the postsynaptic muscle cell becomes depolarized.

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34
Q

How is neuromuscular signaling ceased?

A

Acetylcholine is destroyed by acetylcholintesterase.

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35
Q

How does curare, the plant toxin, act on the muscles of hunted prey?

A

It inhibits the nACh receptor and stops the neuromuscular junction signaling.

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36
Q

If a prey is injected with curare, is it safe to eat?

A

Yes. Curare is too large and highly charged to pass through the lining of the digestive tact.

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37
Q

What is myasthenia gravis caused by?

A

Auto-antibodies to the nACh.

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38
Q

How does botox work?

A

Botulinum toxin inhibits SNARE protein exocytosis machinery and ACh release, so muscles don’t receive the signal to contract and wrinkles are relaxed.

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39
Q

What is the sarcomere, a muscle contractile unit, composed of?

A

Actin: scaffold for myosin.
Myosin: motor ratchet protein that binds and pushed actin.
Tropomyosin: covers actin binding sites during rest.
Troponin: binds Ca++ and move tropomyosin.

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40
Q

How does myosin form cross-bridges with actin?

A

Utilizes ATP to act like a molecular motor and pulls neighboring actin closer together. This shortens the sarcomere length and generates tension (force).
Regulated by Ca++, troponin, and tropomyosin.

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41
Q

What happens when Ca++ binds to troponin?

A

Troponin changes shape which displaces tropomyosin, allowing actin and myosin to interact.

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42
Q

Once action potential is propagates down the muscle sarcolemma and t-tubules…

A

Ca++ is released from intracellular stores in sarcoplasmic reticulum.

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43
Q

What is the function of DHP-Ryanodine receptors?

A

Mediate Ca++ release from sarcoplasmic reticulum.

Physically links T-tubule to sarcoplasmic reticulum.

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44
Q

What causes Ca++ channels to open from the SR?

A

Voltage change in T-tubule.

Ca++ efflux from SR to cytosol.

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45
Q

What is required to release the myosin head from actin?

A

ATP.

If no ATP rigor mortis occurs.

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46
Q

What events at the NMJ occur to lead to Ca++ influx?

A

Actin/myosin cross-bridge cycling.

Pumping of Ca++ back into SR.

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47
Q

What is ATP used for in muscle contraction?

A

Myosin release.

Ca++ pumped into the ER.

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48
Q

What does force come from in muscle contraction?

A

Actin/myosin cross-bridging.

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49
Q

T or F: skeletal muscle fiber diameter affects contraction strength.

A

True.

Add more myofibrils (actin/myosin cross-bridging) more strength is produced.

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50
Q

T or F: you canNOT incerase the number of myofibrils per muscle cell.

A

False.

You can increase the number of myofibrils per muscle cell with exercise.

51
Q

What three mechanisms regulate contraction strength?

A

Recruitment: bringing in more individual motor units.
Summation: high frequency action potentials cause multiple contractions to add together.
Length-tension: sarcomeres have optimum length for optimum actin/myosin overlap.

52
Q

T or F: all 3 mechanisms affecting contraction strength also affect cross-bridge cycling.

A

True.

53
Q

Are all fibers of a given muscle used in every single contraction?

A

No - muscle fibers (motor units) are recruited based on the amount of force required fro a given movement.

54
Q

T or F: nerve action potential is short.

A

True.
It is relative to muscle contraction.
Meaning that multiple muscle action potentials can occur during one muscle contraction allowing another contraction to start before the earlier contraction is finished.

55
Q

A relatively show train of action potentials leads to…

A

Subsequent stronger INDEPENDENT muscle contractions, also known as Treppe.

56
Q

What are two causes of Treppe?

A

Warming of muscle fibers.

Increased cytosolic Ca++ which ensures extra cross-bridging.

57
Q

What are some probable causes of fatigue of muscles?

A

Depletion of ACh.
Depletion of energy reserves exacerbated by blood vessel compression.
Lactic acid buildup.

58
Q

How is lactic acid formed?

A

If no oxygen products from oxidative phosphorylation and the kreb’s cycle are produced, it causes a build up of pyruvates. Those pyruvates are converted into lactate in the cytosol for a short-term fix.

59
Q

What are the 3 muscle contraction phases?

A
  1. Latent period
  2. Contraction
  3. Relaxation (pumping Ca++ moves troponin and tropomyosin back over binding sites)
60
Q

Cross-bridge cycling rate is dictated by…

A

The type of myosin present.
Fast myosin hydrolyzes ATP faster.
Slow myosin hydrolyzes ATP slower.

61
Q

An example of a muscle with fast twitch fibers is _________.

A

eye muscles

62
Q

An example of a muscle with slow twitch muscle fibers is ________.

A

soleus in foot

63
Q

What are some characteristics of glycolytic fibers?

A

Fast/white.
Have a high expression levels of fast myosin and glycolytic enzymes.
Recruited when high force is requires (weight lifting or sprinting).

64
Q

What are some characteristics of oxidative fibers?

A

Slow/red.
Rich in slow myosin, mitochondria and myoglobin, and have a high capacity for ATP production via oxidative phosphorylation.
Typically used first for modest requirements like long-distance running.

65
Q

What are some main characteristics of smooth muscle?

A

They have no striations because myosin and actin are arranged differently.
Tend to contract as a unit instead of individual fibers (gap junctions and varicosities).
Controlled by the ANS and is involuntary.
Stimulated by ACh and norepinephrine.

66
Q

Contraction of smooth muscle in arteries causes…

A

Vasoconstriction

Small radius and flow.

67
Q

Relaxation of smooth muscles in arteries causes…

A

Vasodilation

Large radius and flow.

68
Q

How are smooth muscles able to contract as a unit?

A

Varicosities along the neuronal axon allow diffusion of neurotransmitter over large sections of smooth muscle.
Gap junctions in a single unit also help distribute contraction signal.

69
Q

What does the sympathetic nervous system release?

A

Norepinephrine (or epinephrine from adrenal medulla) onto target organs. The neurotransmitters bind adrenergic receptors.

70
Q

What kind of affects does Beta-1 blockers have on the nervous system?

A

Block sympathetic excitatory affects on the heart.

Hypertension.

71
Q

What kind of affects does Beta-2 agonists have on the nervous system?

A

Dilate lung airways by inhibiting smooth muscle contraction.

Asthma.

72
Q

a1 adrenergic receptor activation causes smooth muscle contraction via…

A

Gq coupled receptor Ca++ release.

73
Q

Smooth muscles have what type/s of Ca++ channels?

A

Voltage gated
Ligand gated
Mechanical/stretch gated

74
Q

Excitation contraction coupling in smooth muscle utilizes _________ instead of troponin.

A

Ca++ calmodulin

75
Q

In excitation contraction coupling, myosin needs to be __________ to stimulate cross-bridge cycling.

A

phosphorylated via MLCK

76
Q

Beta-adrenergic receptors __________ adenylate cyclase signal transduction via _____.

A

Activate

Gs

77
Q

Alpha-2 adrenergic receptors _________ adenylate cyclase signal transduction via _____.

A

Inhibit

Gi

78
Q

Sympathetic activation coordinates “fight or flight” response by flooding the body with nor/epinephrine, which stimulates….

A

Variety of different adrenergic receptor subtypes scattered throughout the body causing appropriate response on tissues expressing particular receptors.

79
Q

Sympathetic activation increases heart rate and cardiac output (beta-1) and appropriately distributes blood flow to skeletal muscles by…

A

Vasoconstricting most body arterioles (alpha-1).

Vasodilating skeletal muscle arterioles (beta-2) so they receive more blood.

80
Q

Parasympathetic neurons release ________ onto target organs during times of rest.

A

Acetylcholine

81
Q

T or F: muscarinic acetylcholine receptors are g-protein coupled.

A

True

82
Q

What does the M1 muscarinic receptor do?

A

Closes the K+ channel, causing depolarization.

83
Q

What does the M2 muscarinic receptor do?

A

Opens the K+ channel, causing hyperpolarization.

An example would be slowing heart rate.

84
Q

What does the M3 muscarinic receptor do?

A

Increases Ca++ via IP3 and leads to smooth muscle contraction.

85
Q

What other brain areas influence autonomic output?

A

Hypothalamus and amygdala.

86
Q

T or F: arteries return blood to the heart, carrying metabolic wastes (urea, CO2) away from tissues.

A

False - that is the job of veins.

Arteries carry blood away from the heart and deliver nutrients, hormones, and O2 to tissues.

87
Q

What are the three layers of the heart?

A

Epicardium: outer layer composed of connective tissue
Myocardium: middle layer composed of muscle tissue
Endocardium: inner layer composed of endothelial tissue.

88
Q

T or F: the blood inside of heart chambers feed the heart tissue.

A

False

Only contained in chambers to be pumped throughout the body. Blood is being fed to body through coronary arteries.

89
Q

What is myocardial ischemia?

A

A condition caused by a lack of oxygen due to blockage of blood.

90
Q

What is myocardial infarction?

A

Also known as a heart attack, a condition where heart tissue dies and begins to scar.

91
Q

What is ventricular fibrillation?

A

A condition in which there are unsynchronized contractions. Results in death.

92
Q

Which side of the heart contains the pulmonary circuit and what is its function?

A

Right side of the heart.

Receives deoxygenated blood from tissues and sends that blood to the lungs.

93
Q

Which side of the heart contains the systemic circuit and what is its function?

A

Left side of the heart.

Receives oxygenated blood from the lungs and sends that blood to the rest of the body.

94
Q

What structure in the heart ensures unidirectional blood flow?

A

Chordae tendinae - keep atrioventricular vales from prolapse.

95
Q

What is the main function of the Atrioventricular Valves?

A

Allow blood to flow from atrium to ventricle.

96
Q

What is the main function of Semilunar Valves?

A

Located between ventricles and arteries to push blood to the rest of the body.

97
Q

Both atria contract to help fill ventricles, 80% of the blood filling is based on ____________.

A

Venous return

98
Q

What are important characteristics of the SA node?

A

Site of initiation of electrical activity.
Autogenic (creates own electricity/pace) but autonomic nervous system can modulate rate.
Spontaneously depolarizes at 100 bpm.

99
Q

What are important characteristics of the AV node?

A

Slows/delays the electrical impulse before it reaches the ventricles (once received by the SA node).
40-60 bpm.

100
Q

What are the functions of gap junctions in cardiac muscle?

A

Rapidly disperse ions to nerighboring heart cells (Na+ and Ca++).
Allows heart muscle cells to contract in unison.
Allows efficient pumping/filling.

101
Q

What is the order of cooordinated electrical activity in the the heart?

A 
SA node
Gap channels
Atria contract
AV node slows
purkinje/gap channels
Ventricles contract
102
Q

What is indicated by the P wave?

A

Atrial depolarization

103
Q

What is indicated by the QRS complex?

A

Atrial repolarization and ventricular depolarization.

104
Q

What is indicated by the T wave?

A

Ventricular repolarization

105
Q

What are the two principal cell types in the heart?

A

Pacemaker cells (SA node) and contractile cells.

106
Q

What makes pacemaker cells different from contractile cells (in regard to membrane potential)?

A

Pacemaker cells have “funny” Na+ channels which open upon repolarization instead of opening upon threshold, like contractile cells.
Pacemaker cells have two types of Ca++ channels: T-type (short) and L-type (long)
Contractile cells have a long action potential, which plateaus because of Ca++ and K+ channels opening.

107
Q

What properties are the same in CARDIAC and SKELETAL muscle?

A

T-tubules, SR, and troponin-tropomyosin.

108
Q

What properties are the same in CARDIAC and SMOOTH muscle?

A

Gap junctions and extracellular calcium.

109
Q

Why is the heart unable to undergo summation and tetany?

A

The long-lasting action potential overlaps in time with muscle contraction events, so only one contraction can occur at a time.

110
Q

Sympathetic release of ____________ causes higher cardiac output (heart rate and stroke volume).

A

norepinephrine

111
Q

Parasympathetic release of ___________ causes lower cardiac output (lower heart rate).

A

acytylcholine

112
Q

How does the sympathetic NS increase cardiac output?

A

By affecting the “funny” Na+ channels and allowing the SA node cells to depolarize faster.
Releasing norepinephraine onto the Beta-1 adrenergic receptor leads to phosphorylation of Na+ and Ca++ channels - making them easier to open.

113
Q

How does the parasympathetic NS decrease cardiac output?

A

By hyperpolarizing the SA node.

114
Q

How does the sympathetic NS increase contractility?

A

Increases available Ca++.

Once nor/epinephrine is binded to Beta-1 adrenergic receptors, Ca++ channels open.

115
Q

How does the parasympathetic NS decrease cardiac output?

A

By binding ACh to the muscarinic receptor, G-protein supplements K+ channel opening and closes the Ca++ channel, causing hyperpolarization.

116
Q

What is the difference between systole and diastole?

A 
Systole = ventricle contraction
Diastole = ventricle filling
117
Q

The first heart sound, caused by AV valves closing is called…

A

Soft lubb

118
Q

The second heart sound, caused by semilunar valves closing is called…

A

Loud lubb

119
Q

When is ventricular pressure the highest?

A

Mid-ventricular systole.

120
Q

Aortic pressure increases during __________ and slowly dissipates during _________.

A

ventricular systole
diastole
(still remains high throughout).

121
Q

Stroke volume is the volume of blood….

A

ejected from the heart during a single beat.

SV = (end-diastolic volume) - (end-systolic volume)

122
Q

Roughly ____ of the ventricular blood volume is ejected per heartbeat.

A

half

123
Q

Stroke volume can be changed depending on the need via…

A

ANS and length tension.

124
Q

What is stated in Frank-starling’s law?

A

The more blood that enters the heart (venous return) the more blood that leaves.
Meaning that it is in control of the heart.

BIOL 310 (3 decks)

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