Exam 2 Flashcards
1
Q
what is the main function of the nervous system
A
coordinates body functions
2
Q
when is nervous system control used
A
when speed or complex integration is required
3
Q
what kind of specificity does the nervous system have
A
anatomical specificity
4
Q
what determines target cells of nervous system
A
the “wiring”
5
Q
what kind of signals is information carried by in the nervous system
A
electrical and chemical
6
Q
what does the input region of a neuron do
A
receives incoming signals
7
Q
where is the input region
A
dendrites (and soma)
8
Q
what is another name for the integrative region
A
the trigger zone
9
Q
where is the trigger zone located
A
at the axon hillock (initial segment of axon)
10
Q
what does the trigger zone do
A
combines inputs from different dendrites and the soma
11
Q
what is the function of the conductive region
A
long-distance propagation
12
Q
where is the conductive region located
A
axon
13
Q
what does the output region do
A
transmits signal to the target cell
14
Q
where is the output region located
A
axon terminal
15
Q
can the membrane potentials be different at different regions of the cell
A
yes
16
Q
what are the two types of electrical signal in neurons
A
graded and action potentials
17
Q
what are graded potentials
A
local signals
18
Q
what is the purpose of a graded potential
A
to carry information from the input region (transduction site or synapse) to the trigger zone
19
Q
what is an action potential
A
long distance signal (spikes)
20
Q
what is the purpose of an action potential
A
to carry information from the trigger zone to the axon terminal
21
Q
what types of electrical signals can occur at the trigger zone
A
both graded and action potentials
22
Q
what are electrical signals
A
temporary changes in membrane potential
23
Q
how does the cell accomplish temporary changes in membrane potential to produce an electrical signal
A
there is a temporary change in membrane permeability (conductance) via gated ion channels
24
Q
do electrical signals appreciably change ion concentrations
A
no
25
what do electrical signals change
the charge separation across the membrane (membrane potential)
26
where do graded potentials originate
in input region
27
how do graded potentials start
due to opening of gated channels
28
do graded potentials increase or decrease in amplitude as they travel
decrease
29
where do graded potentials carry information to
the integrative region
30
are graded potentials excitatory or inhibitory
can be either depending on ion flow
31
what happens to a cell with an excitatory graded potential
the cell depolarizes
32
what is the effect on APs when the cell depolarizes
it is easier to produce an AP
33
what happens to the cell with an inhibitory graded potential
the cell hyperpolarizes
34
what is the effect on APs when the cell hyperpolarizes
it is harder to produce an AP
35
what is the graded potential called when it occurs on a sensory neuron
a receptor potential
36
are receptor potentials excitatory or inhibitory
always excitatory
37
what is the graded potential called when it occurs on an interneuron or a motor neuron
postsynaptic potential
38
what are the different types of postsynaptic potentials
excitatory (EPSP)
inhibitory (IPSP)
39
what is the graded potential called when it occurs on a skeletal muscle
end-plate potential (EPP)
40
are end-plate potentials excitatory or inhibitory
always excitatory
41
what two qualities are graded
amplitude and duration
42
what two qualities are directly proportional to triggering stimulus
amplitude and duration
43
what does it mean to 'summate at the trigger zone'
all of the neurons inputs are integrated at the trigger zone to determine whether action potentials are produced
44
what are the two types of summation
temporal and spatial
45
what is temporal summation
summation of graded potentials from the same source at different times
46
what is spatial summation
summation of graded potentials from two or more sources (locations)
47
what happens is summed activity is subthreshold
no AP produced
48
what happens if summed activity is suprathreshold
AP is produced
49
what type of potentials can occur at the trigger zone
both graded and action potentials
50
where can graded potentials occur on the neuron
soma, dendrites, trigger zone
51
where is the transition from local to long-distance signal
at the trigger zone
52
what kind of signals are APs
long-distance signals
53
where do AP carry information
from trigger zone to axon terminal (at synapse)
54
what happens to the polarization of a cell during an AP
rapid depolarization followed by repolarization
55
do APs increase or decrease in amplitude as they travel
neither, they are regenerated
56
what is the all-or-none part of an AP
APs don't summate and are not graded
57
what can vary an AP
drugs/diseases that alter ion flow
58
what does the frequency of AP code for
stimulus amplitude (intensity)
59
what does the duration of the spike train of an AP code for
stimulus duration
60
what are action potentials produced by
sequential opening and closing of voltage-gated ion channels
61
what are the two types of ion channels related to APs
voltage-gated K+ channels
voltage-gated Na+ channels
62
what are the two states of the voltage-gated K+ channel
closed (resting) and open
63
what are the states of the voltage-gated Na+ channel
closed (resting)
open
inactivated (refractory)
64
what are the orientations of the activation and inactivation gates in the voltage-gated Na+ channel during the closed (resting ) state
activation gate: closed
inactivation gate: open
65
what are the orientations of the activation and inactivation gates in the voltage-gated Na+ channel during the open state
activation gate: open
inactivation gate: open
66
what are the orientations of the activation and inactivation gates in the voltage-gated Na+ channel during the inactivated (refractory) state
activation gate: open
inactivation gate: closed
67
what is the resting membrane potential
-70 mV
68
what are the steps in the rising phase of the generation of an AP
1. depolarization past the threshold and all 3 gates start to transition
2. Na+ gates open more rapidly allowing Na+ influx
3. Na+ influx depolarizes the inside of the cell more
4. more gates open (positive feedback)
69
what are the steps in the falling phase of an AP
1. Na+ gates close
2. K+ channels open
3. K+ efflux which repolarizes the cell
4. all 3 gates begin transitioning to resting state
70
what are the steps in the hyperpolarization phase of an AP
1. K+ channels remain open
2. cell begins to hyperpolarize
71
how does the cell return to Vrest after an AP is generated
the K+ channels will close
72
what are the two different refractory periods
absolute and relative
73
is it possible to generate another AP during the absolute refractory period
no
74
is it possible to generate another AP during the relative refractory period
AP initiation is possible but the threshold is higher
75
when does the absolute refractory period begin
when Vm exceeds threshold and the AP begins
76
when does the absolute refractory period end
when some Na+ channels have reset
77
does the relative refractory period come before or after the absolute refractory period
after
78
what are the Na+ and K+ channels doing during the relative refractory period
some Na+ channels have reset
K+ channels still open
79
what are the steps to an AP propagating from the trigger zone
1. Na+ influx spreads to the neighboring region
2. neighboring region reaches the threshold and a new AP begins
3. the recently active region is refractory, preventing backward propagation
80
where do AP propagate to
over long distances to the output region
81
when is the speed of propagation the fastest
for axons with a large diameter and myelin
82
what is the purpose of myelin
insulated axon and causes the signal to conduct more effectively
83
what kind of conduction do myelinated axons have
saltatory conduction
84
what is located at the nodes of Ranvier
gaps in myelin with voltage-gated channels
85
what happens at the nodes of Ranvier
the AP is regenerated
86
what do action potentials convey
information to synapses where it is then passed along to the target cell
87
what are the two types of synapses
electrical and chemical
88
what kind of junctions are electrical synapses
gap junctions
89
what do electrical synapses do to activity
synchronize activity
90
what kind of signal conduction does an electrical synapse have
rapid, potentially bidirectional signal conduction
91
what kind of synapses are the majority of synapses
chemical synapses
92
where are most NT stored
in vesicles
93
how are most NT released
they are exocytosed due to an action potential
94
where does the NT diffuse after it is released
diffuses across synaptic cleft
95
what kind of signal conduction does a chemical synapse have
slower but more flexible
allows for amplification
96
what is the purpose of an AP
open voltage gated Ca2+ channels for exocytosis
97
what is an example of a neurocrine
neurotransmitters
98
what does it mean to say that neurocrine secretion is graded
there can be any number of neurotransmitters released
99
what does the amount of neurocrine released depend on (2 things)
frequency of APs
duration of spike train
100
what are the three major neurocrines of the PNS
ACh
norepinephrine
epinephrine
101
what happens when a NT is released
it diffuses across the synaptic cleft and binds to a receptor
102
what are the two types of postsynaptic receptors
ionotropic and metabotropic
103
how are ionotropic receptors gated
directly gated (receptor channel)
104
what is the speed of an ionotropic receptor
fast
105
how are metabotropic receptors gated
indirectly gated (GPCR or receptor enzyme)
106
what is the speed of a metabotropic receptor
slow
107
what are the two types of postsynaptic responses
excitatory (EPSP)
inhibitory (IPSP)
108
what are the three ways to terminate neurotransmitter activity
inactivate
reuptake
diffuse away
109
what is signal transduction
information is conserved at each transduction step (as information changes form)
eg: as information changes from chemical to electrical signals etc, the information is conserved
110
what is the function of sensory receptors
to perform sensory transduction
111
what is sensory transduction
conversion of stimulus into receptor potential (or graded potential)
112
where is the postsynaptic response excitatory (sensory/afferent) division
in most senses
113
where is the postsynaptic response inhibitory (sensory/afferent) division
vision
114
what does the receptor look like for most general senses (touch, pressure, temp)
receptive nerve ending of sensory neuron
115
what does the receptor look like for most special senses (hearing, vision, taste)
a receptor cell
- which then releases NT onto sensory neuron
116
what are the three sensory transduction types
1. directly gated
2. indirectly gated
3. direct depolarization
117
what type of receptors are directly gated (ionotropic)
thermoreceptors
mechanoreceptors
118
what type of receptors are indirectly gated (metabotropic)
vision
olfaction
gustation (bitter, sweet, umami)
119
how are indirectly gated receptors usually gated
by GPCR
120
how does direct depolarization occur
through leakage channels
121
what type of receptors are stimulated by direct depolarization through leakage channels
gustation (salty, sour)
122
what are the two different motor divisions of the PNS
somatic motor
visceral motor
123
what type of muscle does the somatic motor system control
skeletal muscle
124
is the somatic motor system voluntary or involuntary
voluntary
125
what type of neuron is involved in the somatic motor system
single motor neuron
126
where is a neuron of the somatic motor system found
extending from the CNS to a muscle cell
127
what is a neuromuscular junction
the synapse between axon terminal or somatic motor neuron and motor end place of skeletal muscle fiber
128
what are the two basic steps that occur after a neuronal action potential
1. voltage gated Ca2+ channels open
2. exocytosis of ACh from axon terminal
129
what kind of receptors are located in the sarcolemma (skeletal muscle fiber membrane)
nicotinic acetylcholine receptors (nAChR)
130
are nicotinic ACh receptors excitatory or inhibitory
excitatory - tonic control
131
what kind of receptor is a nAChR
receptor channel
132
what are the two steps that occur after the binding of ACh to a nAChR
1. binding of ACh allows ion flow
2. depolarization of sarcolemma
133
is the nAChR an ionotropic or metabotropic receptor
ionotropic
134
what kind of potential is an end plate potential (EPP)
graded potential
135
what are the three steps that occur after an EPP is produced
1. voltage gated Na+ channels open
2. sarcolemmal action potential (always produced)
3. muscle contraction
136
what are the four steps in the ACh lifecycle at a neuromuscular junction
1. ACh made from choline and acetyl CoA
2. ACh broken down by acetylcholinesterase (AChE) in the synaptic cleft
3. choline is transported back into the axon terminal
4. choline is reused to make ACh
137
what kind of effectors are controlled by the visceral motor (autonomic) system
involuntary
- cardiac and smooth muscle
- glands
138
what kind of neuron(s) is involved in the visceral motor system
two motor neurons in a series
139
where are the neurons in the visceral motor system found
extending from the CNS to the effector cell
140
what are the two branches of the visceral motor system
sympathetic and parasympathetic
141
what kind of control do the sympathetic and parasympathetic nervous systems have
antagonistic control
142
what kind of effects do the sympathetic and parasympathetic nervous systems have
excitatory and inhibitory
143
do the EPSP and IPSP work separate or simultaneously in the visceral motor system
simultaneously
144
why do the sympathetic and parasympathetic systems work together
to balance shifts with physiological and mental state
145
what is autonomic tone
normal balance between the branches (sympathetic and parasympathetic)
146
what is the difference between a graded potential and an action potential
both are changes in membrane potential but graded potentials can vary in size as opposed to being all-or-none
147
what are the autonomic control centers of the CNS
pons
medulla
hypothalamus
148
what are the three different types of responses that are integrated under CNS control
autonomic
endocrine
behavioral
149
what are the CNS control responses influenced by (2)
cerebral cortex
limbic system
150
are most internal organs under tonic or antagonistic control
antagonistic control
151
what happens to the pupil under sympathetic and parasympathetic control
S: dilates
P: constricts
152
what happens to the heart under sympathetic and parasympathetic control
S: tachycardia (increase)
P: bradycardia (decrease)
153
what happens to the lung bronchioles under sympathetic and parasympathetic control
S: dilate
P: constrict
154
what happens to the GI tract motility/secretion under sympathetic and parasympathetic control
S: decrease
P: increase
155
what happens to the exocrine pancreas under sympathetic and parasympathetic control
S: decrease
P: increase
156
what happens to insulin secretion under sympathetic and parasympathetic control
S: decreases
P: increases
157
if a system is only innervated by the sympathetic branch, what kind of control is it under
tonic
158
what are the two systems only innervated by the sympathetic branch
sweat glands
smooth muscle of most blood vessel
159
what NT is released by the preganglionic neuron
ACh
160
what kind of receptor is on the post ganglionic neuron
nicotinic AChR
161
what kind of receptor is the nicotinic AChR
ionotropic (fast response)
162
what kind of NT is released at the post ganglionic neuron
S: NE
P: ACh
163
what kind of receptor is on the target/effector
S: adrenergic receptors
P: muscarinic AChR
164
what kind of receptors are the adrenergic and muscarinic receptors
GPCR (slow response)
165
what are the 4 adrenergic receptor subtypes
alpha 1
alpha 2
beta 1
beta 2
166
what is the function of alpha 1 receptors
vasoconstriction
167
what is the function of alpha 2 receptors
inhibit digestive system function
168
what is the function of beta 1 receptors
cardiac muscle (excitatory)
169
what is the function of beta 2 receptors
vasodilation
bronchodilation
170
what do autonomic postganglionic neurons end in
varicosities
171
what do varicosities do
store and release NT
172
what is NE synthesized from
tyrosine
173
where is NE stored
in vesicles
174
what are the 3 steps to the release of NE
1. AP
2. voltage gated Ca2+ channels open
3. exocytosis of NE
175
after NE is released, where is it transported back into
back into varicosity
176
what happens after NE is transported back into the varicosity (2)
repackaged in vesicle
broken down by monoamine oxidase (MAO)
177
what is the adrenal medulla an example of
a modified sympathetic ganglion
178
what pathway is produced by the adrenal medulla
sympathoadrenal pathway
179
what are the postganglionic neurons called in the sympathoadrenal pathway
chromaffin cells
180
what do chromaffin cells do
release epinephrine into the blood
181
what is epinephrine
stress neurohormone that activated "fight or flight" response
182
what receptor is present at the first synapse at all 4 motor pathways
nAChR
nicotinic AChR
183
what are the two different types of reflexes
autonomic reflexes
skeletal muscle reflexes
184
what do autonomic reflexes involve
autonomic neurons and effectors
185
what neurons are involved in skeletal muscle reflexes
somatic motor neurons
186
what is the muscle spindle organ
proprioceptors scattered among contractile muscle fibers
187
what does the muscle spindle organ monitor
muscle length (stretch)
188
what kind of channels are in the muscle spindle organ that produce graded (receptor) potentials
mechanically-gated channels
189
what does the muscle spindle (stretch) reflex mediate
postural corrections
190
what is the reflex response of the muscle spindle organ due to
unexpected changes in length
191
what is an example of a reflex due to the muscle spindle organ
patellar reflex
192
what are the two efferent pathways of the muscle spindle organ
contract agonist
relax antagonist
193
what kind of pathway is the contract agonist
monosynaptic pathway
194
what kind of pathway is the relax antagonist
polysynaptic pathway
195
is the relax antagonist excitatory or inhibitory
inhibitory interneuron
196
what does it mean to say that motor neurons tonically control skeletal muscle
there is no inhibitory, just excitatory
197
what does more excitation of the muscle spindle organ lead to
contraction
198
what does less excitation of the muscle spindle organ lead to
relaxation
199
where does the EPP (end plate potential) occur
at the motor end plate of the sarcolemma
200
what is the sarcolemma
membrane of muscle cell
201
what does an EPP cause
sarcolemmal action potential
202
what will each AP of the sarcolemma evoke
a single twitch
203
what is excitation-contraction coupling
the sequence of muscle action potentials and Ca2+ release that initiates contraction
204
where do sarcolemmal AP propagate
along t-tubules
205
what are t-tubules
inward extensions of sarcolemma
206
what part of the SR are t-tubules associated with
terminal cisternae of sarcoplasmic reticulum
207
what does the AP in a skeletal muscle activate
the DHP receptor in the t-tubule (voltage-gated)
208
what does the DHP receptor do
mechanically opens (directly attached to) the ryanodine receptor (RyR) in sarcoplasmic reticulum
209
what happens when the RyR receptor is opened
stored Ca2+ from the SR is released
210
what is a contraction cycle
the contraction/relaxation cycle
211
what does Ca2+ bind to to move tropomyosin
troponin
212
what happens Ca2+ binds to troponin
tropomyosin moves out of the way of the actin binding sites
213
what happens as the actin and myosin filaments slide
muscle shortens
214
what is bound to myosin in the resting state
ADP and Pi
*weakly bound to actin
215
what is the power stroke activated by
Ca2+
216
what causes the myosin head to swivel toward the M line
Pi released
217
what causes myosin to enter the rigor state
ADP is released
218
what causes myosin to release actin
ATP binds to myosin
219
what causes myosin to move back to the "cocked" starting position
ATP hydrolysis
220
what are the steps of muscle contraction in skeletal muscle
1. myosin starts in resting state with ADP and Pi bound (weakly bound to actin)
2. Pi is released and the myosin head swivels toward the M line (strongly bound to actin)
3. ADP is released and myosin enters rigor state (bound strongly to actin)
4. ATP binds to myosin (releases actin)
5. hydrolysis of ATP moves myosin back to resting position (weakly bound to actin)
221
how is the contraction cycle terminated in skeletal muscle
Ca2+ is pumped back into the sarcoplasmic reticulum by Ca2+-ATPase
222
what kind of transporter is Ca2+-ATPase
uniporter
223
what are the three types of skeletal muscle
type 1 - slow oxidative
type 2a - fast oxidative-glycolytic
type 2b - fast glycolytic
224
which type of skeletal muscle is the fastet/slowest
fastest: type 2b
slowest: type 1
225
which type of skeletal muscle has the fastest/slowest myosin ATPase activity
fastest: type 2a and 2b
slowest: type 1
226
which type of skeletal muscle has the smallest/largest diameter
smallest: type 1
largest: type 2b
227
which type of skeletal muscle is the most/least fatigue resistant
most: type 1 and 2a
least: type 2b
228
which type of skeletal muscle is aerobic
type 1
229
which type of skeletal muscle is anaerobic
type 2b
230
which type of skeletal muscle has high/low capillary density, mitochondria, and myoglobin content
high: type 1
low: type 2b
231
do muscles have both type 1 and type 2 fibers
yes
232
what type of muscle fibers mostly make up postural muscles
mostly type 1
233
what type of muscle fibers mostly make up muscles used in short bursts
mostly type 2
234
when is the optimal force generated in skeletal muscles
with moderate initial fiber length (moderate filament overlap)
235
what can increase force
summation
236
what increases to produce summation
stimulus frequency
237
what happens when stimulus frequency increases
there is insufficient time to pump Ca2+ back into the sarcoplasmic reticulum between twitches
238
what does the continuing contraction do to the series elastic elements
allows them to be pulled taut
239
what happens when the series elastic elements are pulled taut
more tension (force) is produced
240
what is tetanus
state of maximal contraction
241
what is unfused tetanus
muscles relax slightly between stimuli
242
what is fused tetanus
sustained maximal tension of the muscles
243
what is a motor unit
somatic motor neuron and all the muscle fibers it innervates
244
are all the muscle fibers in a motor unit the same type
yes
245
how many motor neurons innervate each muscle fiber
one
246
what is motor unit force dependent on
the number of fibers
247
what kind of movements are produced from MUs with few fibers
fine movements, slow twitch
248
what kind of movements are produced from MUs with 1000s of fibers
gross movements, fast twitch
249
what are two ways that muscles can vary force
MU recruitment
frequency coding
250
what kind of motor unites are recruited first
small, slow-twitch units
251
what kind of motor units are held in reserve
large, fast twitch units
252
what happens with increased AP frequency
summation --> increased force
253
is the adaptive response of muscle reversible or irreversibe
reversible
254
what happens with hypertrophy
muscle fibers thicken
(increased myosin and actin so more cross bridges can form)
255
what happens with muscle disuse
atrophy - muscle fibers get thinner
(body uses energy elsewhere)
256
what is isotonic contraction
any contraction in which the muscle changes length
257
what is isotonic contraction used for
body movements and moving objects
258
what are the two types of isotonic contraction
concentric contraction
eccentric contraction
259
how does the muscle force compare to the load in concentric contraction
muscle force is greater than the load
260
what happens to the muscle in concentric contraction
muscle shortens
261
how does the muscle force compare to the load in eccentric contraction
load is greater than the muscle force
262
what happens to the muscle in eccentric contraction
muscle lengthens
263
what does the muscle force do in eccentric contraction
slows muscle lengthening
264
what is isometric contraction
muscle contracts but does not change length
265
how does the muscle force compare to the load in isometric contraction
they are equal
266
what is isometric contraction used for
posture and supporting objects
267
why is length constant in isometric contraction
the sarcomeres shorten but the series elastic elements (CT) stretch
268
what happens to the velocity of muscle shortening when the load increases
the velocity decreases
269
what happens to the velocity when the load=0
maximal velocity of concentric contraction
270
what are the two causes of excitation in cardia muscle cells
spontaneous (rhythmic)
via gap junctions from other cardiac muscle cells
271
what are the cardiac muscle contraction rate and force influenced by
autonomic input
272
where is the AP propagated from in the contraction of a cardiac contractile cell
propagated from adjacent cell
273
in cardiac muscle cell, what does the AP result in
voltage-gated Ca2+ channels in t-tubule open
274
in cardiac muscle cell, what causes extracellular Ca2+ to enter cytosol
voltage gated Ca channels opening
275
in cardiac muscle cell, what is the result of the extracellular Ca entering the cell (cytosol)
the RyR on the SR opens
276
in cardiac muscle cell, what happens when the RyR is opened
Ca2+ from the SR enters cytosol
(Ca2+ induced Ca2+ release)
277
in cardiac muscle cell, what does the Ca2+ that was released from the SR do
binds to troponin
278
how do cardiac muscles relax
Ca2+ is pumped back into the SR and out of the cell
279
what are the 5 causes of contraction in smooth muscle
autonomic neurons
hormones/paracrines
stretch
via gap junctions from other smooth muscle cells
spontaneous (rhythmic)
280
what does a smooth muscle contraction result in
increased cytosolic Ca2+ from
1. SR (IP3 activated receptor)
2. extracellular fluid (cell membrane channels)
281
in smooth muscle, what causes the contraction mechanism to start
increased Ca2+ in cytosol
282
in smooth muscle, what does Ca2+ bind to
calmodulin (CaM)
283
in smooth muscle, what does Ca2+-CaM activate
myosin light chain kinase (MLCK)
284
in smooth muscle, what does MLCK do
phosphorylates myosin
285
in smooth muscle, what happens when myosin is phosphorylated
myosin ATPase activity increases
286
does smooth muscle contraction use cross bridges like skeletal muscle
yes
287
where does Ca2+ come from in smooth muscle
extracellular fluid and SR
288
is an AP required for Ca2+ release in smooth muscle
no
289
how does Ca2+ initiate smooth muscle contraction
through cascade and phosphorylation
290
how does smooth muscle relax
1. myosin light chain phosphatase (MLCP) dephosphorylates myosin
2. Ca2+ is pumped back out of cell and into SR
291
in smooth muscle, what happens when myosin is dephosphorylated
myosin ATPase activity decreases
292
what happens to the cytosolic Ca in smooth muscle when Ca is pumped back into the SR
it decreases
293
in smooth muscle, what happens to Ca2+-CaM when Ca2+ is pumped back into the SR
Ca unbinds from CaM
294
in smooth muscle, what happens to MLCK activity when Ca is pumped back into the SR
it decreases
295
in smooth muscle, what happens to myosin ATPase activity when Ca is pumped back into the SR
it decreases
296
in smooth muscle, what determines the contraction rate
MLCK/MLCP ratio
(kinase/phosphatase ratio)
297
what are cardiomyocytes
cardiac muscle cells
298
what are the two kinds of cardiomyocytes
autorhythmic cells (fibers)
contractile cells (fibers)
299
how do autorhythmic cells generate APs
spontaneously generate AP
300
how do autorhythmic cells conduct APs
via gap junctions
301
are autorhythmic cells contractile
no (have no myosin/actin to generate force)
302
how do contractile cells conduct APs
via gap junctions
303
what is a pacemaker potential in autorhythmic cells
unstable membrane potential (no resting potential)
304
in a pacemaker potential, what kind of channels open at -60mV
special ion channels (If)
305
what are If channels permeable to
both Na+ and K+
306
does Na+ or K+ movement predominate in an If channel? why?
Na+ influx predominates due to stronger driving force
307
does a pacemaker potential have a slow or fast depolarization
slow
308
what happens to If channels as they approach threshold
the If channels close
309
what triggers an AP in autorhythmic cells
the pacemaker potential reaches threshold so the voltage-gated Ca2+ channels open
310
in autorhythmic cell AP, what happens when the Ca2+ channels open
depolarization phase of AP
311
in autorhythmic cell AP, what causes the repolarization phase of the AP
delayed closing of Ca2+ channels and opening of voltage-gated K+ channels
312
how are contractile cells depolarized to the threshold for an AP
by adjacent cells via gap junctions
313
in a contractile cell AP, what causes the depolarizing phase
Na+ channels open
314
in a contractile cell AP, what causes the initial repolarizing phase
Na+ channels close
fast K+ channels open
315
in a contractile cell AP, what causes the plateau phase
balance between Ca2+ channels and slow K+ channels
316
in a contractile cell AP, what causes the final repolarizing phase
Ca2+ channels close
slow K+ channels fully open
317
what kind of channels are all of the channels involved in the contractile cell AP
voltage-gated
318
what are the 4 phases of contractile cell AP
1. depolarizing phase
2. initial repolarizing phase
3. plateau phase
4. final repolarizing phase
319
what is the length of a cardiac AP compared to neuronal and skeletal muscle AP
cardiac AP is very long
320
what part of the cardiac contractile cell AP is long
the refractory period
321
what does the long refractory period in a cardiac contractile cell allow for the heart to do
relax between contractions
322
can cardiac contractile AP summate
no (because of long refractory period)
323
what is the pacemaker of the heart
sinoatrial node (SA node)
324
why is the SA node the pacemaker
because it has the fastest intrinsic rhythm
325
what is the conduction pathway comprised of
autorhythmic cells
326
where do the autorhythmic cells of the conduction pathway spread conduction to
contractile cells
327
do electrical or mechanical events come first
electrical events trigger and precede mechanical events
328
which node has slower conduction
AV node (AV node delay)
329
why is the AV node delay present in the heart
to allow the ventricles to fill before they contract
330
what part of the heart contracts first? second? third?
apex --> base of heart --> arteries
331
what is the contraction of the heart coordinated by
purkinje fibers
332
what does an electrocardiogram reflect
the electrical activity of the heart
333
where is the ECG/EKG recorded from
the body surface
334
what does the ECG?EKG represent
summed electrical activity of all heart cells
(NOT a single AP)
335
what are the three different things that electrical activity is divided into
waves
segments
intervals
336
what are the waves of the heart
PQRST
deflections above/below baseline
337
what are the segments of the heart
P-R, S-T
sections between 2 waves that are zero/electroneutral
338
what are the intervals of the heart
PR, QT
combination of waves and segments
339
what does the P wave correspond to
atrial depolarization
340
what does the P-R or P-Q segment coorespond to
conduction time through AV node and AV bundle
atrial contraction occurs
341
what does the QRS complex coorespond to
ventricular depolarization
342
what does the S-T segment correspond to
most of the ventricular contraction occurs
343
what does the T wave correspond to
ventricular repolarization
344
what does the T-P segment correspond to
heart electrically silent between cycles
345
what are four things that are provided by the ECG
heart rate
heart arrhythmias
extra beat (PVCs)
heart block
346
what is the heart rate
time between 2 P or R waves
347
what is the normal resting heart rate
60-100bpm
348
what is tachycardia
above normal heart rate
349
what is bradycardia
below normal heart rate
350
what is a type of heart arrhythmia
fibrillation
351
what is fibrllation
disorganized contraction
352
what happens with an extra beat/PVC
one part of the conducting circuit fires too early and is out of sync with the rest
353
what happens with a heart block
conduction through the AV node is disrupted
354
where does blood flow in correspondence to pressure
blood flows from area of higher pressure to area of lower pressure
355
what is systole
contraction
356
what is diastole
relaxation
357
what does systole do to pressure
increases pressure
358
what does diastole do to pressure
decreases pressure
359
what are the five stages of the cardiac cycle
1. late atrial and ventricular diastole
2. atrial systole
3. isovolumic ventricular contraction (part of ventricular systole)
4. ventricular ejection (part of ventricular systole)
5. isovolumic ventricular relaxation (part of ventricular systole)
360
when does the late atrial and ventricular diastole stage begin
when ventricular pressure drops below atrial pressure
361
what happens to AV valves during the first step in the cardiac cycle
they open
362
where does blood flow in the first step in the cardiac cycle
into the ventricles
363
what happens to the atria during the first step in the cardiac cycle
the atria fill with blood from the veins
364
what happens to atrial pressure during atrial systole
atrial pressure rises
365
what ends during atrial systole
ventricular diastole
366
what is the end-diastolic volume (EDV) at the end of ventricular diastole
~135mL
367
what does end-diastolic volume mean
the volume of blood in either ventricle at the end of ventricular diastole
368
when is there the greatest ventricular volume in the cardiac cycle
at the end of atrial systole
369
when does isovolumic ventricular contraction begin
when ventricular pressure exceeds atrial pressure
370
what happens to AV valves during step 3 of the cardiac cycle
AV valves close
371
when does the first heart sound (lub) occur
S1 occurs during isovolumic ventricular contraction (step 3)
372
are all 4 valves open or closed during step 3 of the cardiac cycle
closed
373
what happens to the EDV during step 3
it continues
374
what happens to the ventricular pressure during step 3 of the cardiac cycle
it increases
375
as the atria begin to relax in step 3 of the cardiac cycle, what happens to blood
it begins to flow from veins into atria
376
when does ventricular ejection begin
when ventricular pressure exceeds pressure in aorta
377
what happens to SL valves and blood when ventricular ejection starts
SL valves open and blood flows into arteries
378
does al blood leave ventricles during step 4 of cardiac cycle
no
379
what is the end systolic volume (ESV) during ventricular ejection
~65mL
380
what is the end systolic volume (ESV)
volume of blood in either ventricle at the end of ventricular systole
381
when is the minimum ventricular volume in cardiac cycle
at the end of ventricular systole
382
when does the isovolumic ventricular relaxation step of the cardiac cycle begin
when ventricular pressure drops below the pressure in the aorta
383
what happens to the SL valves during the 5th step in the cardiac cycle
SL valves close
384
when does the second heart sound (dub) occur in the cardiac cycle
during step 5 (S2 heart sound)
385
what occurs in the fifth step of the cardiac cycle due to rebound
dicrotic notch
386
are the four valves open or closed during the fifth step of the cardiac cycle
closed
387
what happens to ESV during isovolumic ventricular relaxation
it continues
388
what does wiggers diagram integrate
mechanical and electrical events
389
what does the crossing of pressure lines on wiggers diagram indicate
reversal in pressure gradient
390
what is cardiac output
volume of blood pumped by one ventricle per minute
heart rate x stroke volume
391
what is stroke volume (SV)
mL of blood pumped by a ventricle per contraction
392
what is heart rate (HR)
number of beats per minute (bpm)
393
what is the average cardiac output (CO) at rest
5 L/min
394
what is the average stroke volume (SV) at rest
70 mL/beat
395
what is the average heart rate (HR) at rest
72bpm
396
what happens to CO if SV or HR change
CO will also be affected
397
what can lead to a change in HR (therefore affecting CO)
autonomic nervous system can alter heart rate at SA node
398
what are the steps leading to decreased heart rate
(parasympathetic NS (dominates at rest))
1. ACh binds to mAChR receptor
2. higher K+ efflux and lower Ca2+ influx
3. hyperpolarizes membrane potential (Vm) of the autorhythmic cells and slows pacemaker depolarization
4. HR decreases
399
what are the steps leading to increased heart rate
(sympathetic NS)
1. NE and Epi bind to beta-1 receptor
2. higher Na+ and Ca2+ influx
3. depolarizes membrane potential (Vm) of autorhythmic cells and speed up pacemaker depolarization
4. HR increases
400
what are the three factors that influence stroke volume (SV)
1. contractility
2. end-diastolic volume (EDV)
3. afterload
401
what is the stroke volume equation
SV= EDV - ESV
402
what is the stroke volume (mL/beat) related to
the force of contraction
403
what is contractility
intrinsic forcefulness (independent of fiber length) due to Ca2+ interaction with troponin
404
what does end-diastolic volume (EDV) affect (muscular)
affects contraction force via muscle fiber length at start of contraction
405
what is afterload
force a ventricle must overcome in order to eject blood
406
what will increase contractility (therefore increasing force of contraction)
catecholamines (epi and NE)
407
is the increased force of contraction of the heart considered a positive or negative ionotropic effect
positive
408
are the contractile cells innervated by the parasympathetic or sympathetic NS
sympathetic innervation of contractile cells only
409
when NE and epi bind to a beta-1 receptor, what happens (in reference to contractility)
phosphorylation of
1. Ca2+ channels: more Ca2+ entry from extracellular fluid (more Ca2+ entry into the cell)
2. phospholamban: Ca2+ is pumped into the SR faster
410
what happens when phospholamban is phosphorylated
1. Ca2+ is pumped into SR faster
2. higher stored Ca2+ --> stronger contractions
3. less Ca2+ - troponin binding time --> briefer contractions
411
what is the frank-starling law
stroke volume increases as EDV increases
412
what happens when there is more blood in the heart
fibers stretch more and a more forceful contraction occurs
413
what is preload
degree of stretch
414
what is EDV normally determined by
venous return
415
what is venous return
amount of blood entering heart from the veins
416
what three factors increase venous return
skeletal muscle pump
respiratory pump
venoconstriction (vasoconstriction of veins)
417
how does the skeletal muscle pump increase venous return
active skeletal muscles squeeze veins
418
how does the respiratory pump increase venous return
1. diaphragm lowers during inspiration
2. increased abdominal pressure and decreased thoracic pressure
419
how does venoconstriction increase venous return
from sympathetic innervation of smooth muscle in veins
420
what is afterload
force a ventricle must overcome in order to eject blood
421
what is afterload due to
arterial blood pressure
422
what does increased afterload lead to
decreased stroke volume and increased ESV
423
what can prolonged high blood pressure lead to? why?
heart failure because heart is unable to keep pace with body's demands
