LAB PRACTICAL 2 Flashcards
1
Q
electromyography
A
a recording of the electrical activity of muscle tissue using electrodes attached to the skin or inserted into the muscle
2
Q
surface EMG
A
electrodes placed on skin surface
3
Q
intramuscular EMG
A
electrodes inserted into muscle; provides more insight
4
Q
why do EMG signals look noisy?
A
EMG signals look noisy because motor units fire asynchronously
5
Q
Nerve conduction study
A
detects neuropathies and can help with diagnosis of nerve compression or injury (carpal tunnel, sciatica)
6
Q
signal conditioning
A
done by PowerLab; signal is modified by amplification and filtering
7
Q
digital conversion
A
after signal conditioning, the analog voltage is sampled at regular intervals and converted from analog to digital before transmission to the attached computer
8
Q
Raw EMG
A
records the potential difference detected at the electrode; often looks noisy when muscles are contracting
9
Q
Integrated EMG
A
records the potential difference detected at the electrode, often looks noisy when muscles are contracting
10
Q
reciprocal activation
A
activation of the agonist muscle and inactivation of antagonist muscle during goal-oriented movements
11
Q
co-activation
A
during contraction of the agonist muscle, the antagonist muscle is slightly contracted as well for joint stability
12
Q
co-contraction
A
activation of an antagonist and agonist muscle around a joint to maintain a given posture
13
Q
What happens to your EMG signal when you increase the contraction strength?
A
when you increase the contraction strength, the EMG amplitude increases
14
Q
During reciprocal activation, why is the antagonist muscle not completely silent?
A
during reciprocal activation, the antagonist muscle is not completely silent because of a phenomenon called co-activation, which simultaneously slightly contracts the antagonist muscle to stabilize the joint
15
Q
Why is the electromyogram waveform irregular?
A
The EMG is irregular because it is recording asynchronous electrical activity because signals from multiple muscle fibers are being recorded. This contrasts electrocardiograms because the cardiac muscles fire synchronously to maintain a steady heartbeat.
16
Q
Brett ate poisonous wild mushroom, which partially paralyzed his motor unit. What would a normal EMG trace look like?
A
A normal EMG from Brett would have higher amplitudes. If his motor unit was partially paralyzed, its functions would be inhibited and therefore it would be less efficient at propagating action potentials and stimulating muscle fibers. With decreased electrical signaling from the motor unit, the EMG trace has smaller amplitudes
17
Q
When we placed electrodes on the bicep and tricep, what data were we collecting?
A
electrical activity of the muscle via electromyograms
18
Q
Transduction
A
the process of converting one energy type to another
19
Q
force transducer
A
converts an input mechanical force into an electrical output signal
20
Q
raw input of data inquisition
A
analog signal
21
Q
powerlab
A
data inquisition hardware that measures electrical signals
22
Q
muscle used in frog lab
A
gastrocnemius
23
Q
muscle twitch
A
a single contraction-relaxation cycle in a muscle fiber
24
Q
twitch
A
response to a single threshold stimulus; can vary in height, duration, and rising slope
25
recruitment
multiple motor unit summation; if a stronger stimulus is applied, a graded response results from the summation of contractile forces from multiple muscle fibers
26
recruitment
refers to twitches in all of the fibers of several motor units
27
maximum excitation voltage
stimulus voltage that will recruit all muscle fibers
28
supramaximal excitation voltage
1.5X the maximal stimulus; ensures all motor units are recruited
29
threshold stimulus
the force (mV) at which the first muscle twitch is observed
30
summation
an increase in contractile force with multiple stimuli in a short period of time, especially when effects from previous stimuli have not completely subsided
31
tetanus
a sustained muscle contraction evoked when the motor nerve that innervates a skeletal muscle emits action potentials at a very high rate; as stimuli frequency increases and tension remains fairly constant
32
incomplete tetanus
where each stimulus causes a contraction to be initiated when the muscle has only partly relaxed from the previous contraction
33
complete tetanus
when muscle has reached a state of maximal sustained contraction
34
why is tetanic tension much greater than twitch tension?
In a twitch action potential: release of Ca2+ saturates troponin and exposes active sites with one stimulus. Because there is a single stimulus, Ca2+ availability is small.
During tetanus: continuations of action potentials provide enough Ca2+ to saturate troponin at all times.
35
Three mechanisms of fatigue
conduction failure
lactic acid buildup
buildup of ADP and inorganic phosphate
36
Conduction failure
action potentials repeatedly fire in muscle and extracellular potassium levels increase in the T-Tubule from repeated depolarization, upsetting ion concentration balance and leading to failure of another action potential
37
lactic acid buildup
during anaerobic respiration, muscle proteins may be altered
38
buildup of ADP and Pi
inhibits cross bridge cycling and delaying cross bridge attachment on actin
39
why is calibration of the force transducer essential?
this process zeros out the transducer by removing any tension on the string that is not the result of muscle contraction and allows measurements following this procedure to be comparable
40
as you increase the voltage to the muscle, how does it respond to the increased stimulus?
as the voltage increases from threshold to maximum:
- Greater force in the muscle contraction
- Once maximal voltage reached, further increase in stimulus will show no effect on force of muscle contraction
41
how does the isolated muscle respond as the stimulus interval was decreased progressively?
summation of stimuli and stronger contractile forces in the isolated muscle
42
How did the isolated muscle respond as it was stretched progressively?
as the gastrocnemius was stretched, the muscle contracted with greater force and the strength of contraction increased up to a certain length
43
how did the muscle respond to high frequency stimulation?
the isolated muscle experienced complete tetanus and its contractile force progressively declined until 35 seconds when it failed and gave out
44
how can you explain the graded response in light of the "all-or-none" law of muscle contraction?
the all or none law of muscle contraction refers to individual muscle fibers contracting. the graded response refers to the number of motor units that have been recruited to contract.
45
at which stimulus interval did you observe tetanus?
tetanus is a sustained muscle contraction elicited from frequent stimuli. With continuous and frequent stimuli, APs are generated in the muscle at a similar rate, preventing the muscle from relaxing in between these stimuli. The muscle is unable to relax because with frequent action potentials, calcium ions are released in the cell which continuously bind to troponin and expose the actin binding site. Without enough time to pump the Ca2+ ions out of the cytoplasm, the muscle continuously contracts
46
what stretch resulted in the highest contraction force?
when the muscle was stretched to 2mm, it generated the highest contractile force because actin and myosin filaments had optimal overlap. As it was increasingly stretched, its ability to contract and generate force decreased because the actin and myosin filaments had less overlap and therefore contracted with less force
47
rigor mortis
lack of ATP in a corpse does not allow myosin heads to unbind from actin binding sites
48
resting membrane potential
the electrical membrane potential difference between the exterior and interior of the cell
49
resting membrane potential is determined by
a difference in ion concentrations
relative permeability of the cell membrane to the different ion species
50
equilibrium potential
each ion has a unique voltage when they are at equilibrium
51
characteristics of action potentials
regenerative, brief, stereotyped, all or none with refractory period, directional conduction of signals
52
nerve program
examines the generation and propagation of action potentials
53
setup of nerve
- stimulus electrode and one recording electrode are fixed
- other two recording electrodes can be moved up and down the axon
- different colored action potentials correspond to different nerves being stimulated
54
white matter
myelinated nerve fibers
55
grey m atter
nerve cell bodies, unmyelinated nerve fibers
56
corpus callosum
axons that connect the two hemispheres of the brain; roof of lateral ventricles
57
fornix
floor of lateral ventricles, output tract of hippocampus to mammillary body
58
choroid plexus
lines ventricles, produces CSF
59
aqueduct of sylvius
mesencephalic aqueduct
60
diencephalon
relays sensory information and connects nervous system structures with endocrine system
61
brainstem
midbrain, pons, medulla oblongata
62
frontal lobe
behavior, personality, learning, motor control
63
parietal
sensory information
64
temporal
hearing and sound, language and understanding
65
occipital
vision
66
central sulcus
divides frontal lobe from parietal
67
lateral sulcus
divides frontal lobe from temporal
68
olfactory
smell (sensory)
69
optic
vision (sensory)
70
oculomotor
eye movement and focusing; elevates eyelid (motor)
71
trochlear
nerve supply to eye muscle; superior oblique (motor)
72
trigeminal
3 main branches:
maxillary
mandibular
ophthalmic nerves
chewing, sensation from forehead, eyes, teeth, tongue, gums, nose, lips (sensory and motor)
73
abducens
eye movement; lateral rectus (motor)
74
facial
facial expression, tongue, taste buds, salivary glands (sensory and motor)
75
vestibibulocochlear
posture, heraing (sensory)
76
glossopharyngeal
taste sensation and back of tongue, swallowing, visceral sensory from carotid bodies (sensory and motor)
77
vagus
most pharyngeal and laryngeal muscles; visceral sensory information from pharynx, larynx, carotid bodies, heart, lungs, abdominal organs; general sensory information from external acoustic meatus, eardrum, and pharynx (sensory and motor)
78
accessory
head movement (sternocleidomastoid and trapezius muscles) (motor)
79
hypoglossal
speech, swallowing (tongue muscles) (motor)
80
cerebral cortex
6 layers
giant pyramidal cells and Betz cells are most numerous in layer 5
axons leave the cortex via tracts of white matter (cerebral corpuscles) and run caudally to spinal cord via corticospinal or pyramidal tract
betz cell dendrites are different from purkinje cell dendrites
81
cerebellum
3 layers
molecular layer
purkinje layer
granule layer
82
molecular layer
close to the surface, contains axons from many sensory systems; dendrites of purkinje cells extend to this layer
83
purkinje cell layer
somas of purkinje cells located here
84
granule cell layer
cell bodies of interneurons whose axons make up molecular cell layer
85
differences between human and sheep brain
olfactory bulb: sheep has larger
mammillary bodies: human has 2, sheep has large one
size: human is 3-4lbs, sheep isi 140-180 grams
sulci: human has more which increases surface area and complexity
86
how does the relative size of the fornix in the sheep brain compare with the human fornix?
the fornix is larger in the sheep because it connects the hippocampus to mammillary body which connects their sense of smell to their emotions, allowing them to sense food and danger
87
How does Vrest change in response to concentration changes of K and Na?
Na: increase intracellularly, membrane is more hyperpolarized
K: increase intracellularly, membrane hyperpolarizes
88
does K+ or Na+ have a bigger effect on Vrest?
K+ dominates at rest with potassium leak channels and has a greater conductance so changing its concentration has a bigger effect
89
MetaNeuron: Vrest = -64.81
Experimental data: Vrest = -73.06
WHY?
the data calculation was different from MetaNeuron because the data calculation included the involvement of Cl- anions in the membrane resting potential in addition to Na+ and K+
90
When conductance is shown on the graph, why are both traces positive?
both traces are positive because both ion channels have opened and increased the permeability to the ions
91
when ionic currents are shown on the graph, why is the K+ trace positive while the Na+ trace negative?
The K+ trace is positive because it is going outside of the cell (up) whereas the Na+ trace is negative because it is going inside the cell (down)
92
When TTX is applied to the neuron, there is still a small depolarization. Why?
the cell can still depolarize but it cannot initiate an action potential because the sodium voltage gated channels are blocked.
93
what is the cause of the blip in the Na+ trace for currents?
When the membrane is depolarizing, the membrane voltage reaches closer to ENa. When closest to ENa, the driving force for Na+ is the least and the Na+ current starts decreasing in response to the lowered driving force. This slowdown of the current causes the upward deflection. When K+ channels open, the membrane returns to its resting conditions and results in an increase in the driving force and subsequent increase in Na+ current.
94
what is the maximum temperature to generate and action potential? what trends do you notice as temp decreases?
Maximum temp: 22 degrees (C)
as temperature decreases, the cellular action potential response time decreases. This occurs because colder temperatures tend to slow down most cellular processes, so a neuron firing slows down as well
95
TTX symptoms
numbness in lips, tongue, face, neck
pains in stomach and throat, nausea and vomiting
difficulty breathing, complete paralysis and irregular heartbeat
96
Mechanism of TTX
blocks the acetylcholine receptors on the muscle fiber so acetylcholine does not depolarize the cell and initiate a contraction --> paralysis
97
batrachotoxin symptoms
numbness in fingers, lips, mouth
98
batrachotoxin mechanism
causes a conformational change that prevents voltage gated sodium channels from closing
99
ventral nerve cord
nerve that runs the length of the worm on the inner ventral surface
100
three giant axons
one medial fiber and two lateral fibers
101
lateral fiber characteristics
have higher stimulus thresholds, require increased voltages
conduct slower than medial fiber, so longer latent period
102
intracellular recordings
measures single transmembrane potential by inserting a glass pipette into one cell and recording potential changes
103
extracellular recording
small potential differences recorded by placing an electrode in living tissue in close proximity to an excitable cell; no direct access to membrane potentials
104
biphasic extracellular recording
AP propagation:
passes under first electrode (negative), region is more negative in relation to second electrode; - and - makes a positive deflection
as it recovers, the region under the second electrode (positive) becomes negative; + and - records a negative deflection
105
extracellular recording characteristics
size and shape of waveform depend on the distance between the two recording electrodes, the length of the axon segments, and the conduction velocity of the axon
106
conduction velocity
speed at which an electrochemical impulse propagates down a neural pathway
107
absolute method (conduction velocity)
determined by distance and latency period
108
difference method (conduction velocity)
determined from both original set up and when both recording electrodes are moved away or closer to the stimulus
109
refractory period
longest interpulse interval at which a second action potential cannot be evoked
110
what is the relationship between stimulus strength and response amplitude in a single axon?
the stimulus strength does not influence response amplitude because it is all or nothing
111
an intracellularly recorded nerve action potential approximates 80 mV. Why is your action potential smaller?
because extracellular recordings detect small potential differences to indicate an action potential has occurred as opposed to intracellular recordings that measure single transmembrane potentials. Extracellular electrodes do not access these intracellular electrical signals
112
cockroach legs
locomotion and sensory receptors for tactile, auditory, and vibratory stimuli
113
sensory spine action potential
when the spine moves, the dendrite of the neuron is distorted, opening mechanically gated ion channels in the dendrite which creates a receptor potential and triggers an action potential
114
femoral spines
less abundant than tibial, two rows on ventral surface
115
tibial spines
highly abundant, diverse orientation
116
femoral tactile spine
single large spine that projects dorsally, contains a single bipolar sensory neuron
117
cell body
size of body and nucleus increases linearly with the axonal diameter of the tactile spine
118
spontaneous firing
observed in a small population of axons
119
extracellular triphasic action potentials
movement of spine produces burst of action potentials and demonstrates fast adaptation
120
setup of cockroach leg
positive: femur
ground: coxa
negative: coxa
121
large bin size
many spikes into one bin, false impression they originate from a single axon
122
small bin size
variability of AP combined with background noise from recording system distributed across several bins
123
hormone
chemical messenger produced by an organ that is released into circulation and targets cells on distant organs
124
endocrine glands
pancreas, thyroid, parathyroid, pituitary, adrenal, gonads, placenta
125
endocrine tissues within other glands
heart, liver, kidney, GI, adipose
126
tissues that modify hormones
lungs, skin, liver, kidney
127
pineal gland
secretes melatonin
128
hypothalamus
produces hormones that control secretions in anterior pituitary; produces ADH and oxytocin
129
thyroid
bilobed, pyramidal lobe
thyroid follicles and parafollicular/ c cells
130
thyroid follicles
lined with cuboidal epithelial cells
follicular colloid
131
follicular colloid
iodinated glycoprotein; fluid of lumen that produces thyroid hormones T3 and T4
132
T3 and T4
increase metabolic processes
133
parafollicular (c cells)
produces calcitonin
134
calcitonin
decreases blood calcium by depositing it into bones
135
pancreas
exocrine and endocrine tissue
136
exocrine tissues of pancreas
synthesizes and secretes digestive proenzymes and enzymes
137
endocrine tissues of pancreas
acinar cells, islets of langerhans, venule
138
acinar cells
secretes digestive enzymes
139
islets of langerhans
clusters of cells responsible for secreting different hormones
alpha cells and beta cells
140
alpha cells
produce glucagon
141
beta cells
produce insulin
142
glucagon
releases glucose by stimulating glycogenolysis in liver
143
insulin
increases glucose uptake and promotes protein synthesis
144
venule
drains pancreatic islet of langerhans secretions, provides blood supply to pancreatic acini
145
parathyroid
chief cells, oxyphil cells
146
chief cells (principal cells)
most numerous, produces parathyroid hormone (PTH)
147
parathyroid hormone (PTH)
increases level of calcium in the blood
148
oxyphil cells
larger cell type, abundant mitochondria, unknown function
149
adrenal gland
cortex and medulla
150
adrenal cortex
zona glomerulosa
zona fasciculata
zona reticularis
151
zona glomerulosa
produces mineralocorticoids
152
mineralocorticoids
maintain homeostasis by stimulating reabsorption of Na+ by kidney
153
zona fasciculata
most active; produces glucocorticoids
154
glucocorticoids
promote normal metabolism and body to resist stress; cortisol, cortisone, corticosterone
155
zona reticularis
produces sex hormones
156
adrenal medulla
produces epinephrine and norepinephrine
157
epinephrine
vasodilation
158
norepinephrine
vasoconstriction
159
pituitary gland
hypophysis; secretes hormones that regular other endocrine glands
160
anterior pituitary
adenohypophysis;
pars distalis
pars intermedia
pars tubercle
161
pars distalis
secretory portion; acidophils, basophils, chromophobes
162
pars intermedia
vesicles with colloid that separate anterior from posterior
163
acidophils
red / pink
somatotropin, prolactin
164
somatotropin
growth hormone, STH
165
prolactin
lactotropic hormone, LTH
166
basophils
blue / purple; least abundant
thyrotropin (TSH) and gonadotropic hormones
167
thyrotropin (TSH)
controls production of thyroid hormones
168
gonadotropic hormones
FSH and LH
169
follicle stimulating hormone (FSH)
stimulates development of the follicle, production of estrogen
170
luteinizing hormone (LH)
works with FSH to stimulate ovary follicle maturation, controls development and maintenance of interstitial cells of the testes
171
chromophobes
uniform, lightly stained cytoplasm, most abundant, smaller
ACTH and MSH
172
adrenocorticotropin (ACTH)
stimulates adrenal cortex which synthesizes and releases glucocorticoids
173
melanocyte-stimulating hormone (MSH)
stimulates pigment changes
174
posterior pituitary
neurohypophysis; composed of hypothalamic axons of unmyelinated nerve fibers, herring bodies, pituicytes, capillary network
stores and releases hormones produced by the hypothalamus
175
infundibulum
connects hypothalamus and pituitary
176
herring bodies
terminal ends of axons that store hormones
177
pituicytes
specialized glial cells in posterior pituitary
178
antidiuretic hormone (ADH)
vasopressin; stimulates reabsorption of water from urine in the distal tubules of the kidney
179
oxytocin
stimulates myometrium of the uterus during pregnancy; stimulates contraction of myoepithelial cells in the mammary gland, resulting in milk secretion
180
PTU
interferes with thyroid hormones by inhibiting synthesis of T3 and T4 which decreases metabolic processes
