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AnSci 214 Exam 2 Review
Nervous, Muscle, CV System
Nervous System
• 1) Explain how summation, EPSPs and IPSPs work to influence events at the
post-synaptic neuron.
– What is an EPSP? IPSP?
– What is temporal summation and how are EPSP’s/IPSP’s involved?
– What is spatial summation and how are EPSP’s/IPSP’s involved?
• Figure 11.19.
EPSP: Excitatory, stimulus leaves postsynaptic neuron at a more positive state (easier to reach threshold)
IPSP: Inhibitory, stimulus leaves post synaptic neuron at a more negative state (harder to reach threshold)
Temporal: At same location, different time/frequency of stimulus
Spatial: At different location, at same time and postsynaptic neuron
Nervous System
• 2) Trace the initiation and propagation of an action potential from a presynaptic
neuron and the transfer of a signal to the postsynaptic neuron. Be sure to
include refractory periods and neurotransmitters in your discussion.
• Figure 11.11.
1) Resting State: Membrane
Potential at steady -70mV
2) Depolarization: Na+ channels
open, quick influx of Na+, cause
cell to become positive
3) Peak of AP: Na+ channels close
quickly
1) Repolarization: K+ channels
open, efflux K+, allows cell to
become more negative (protein
carries – charge)
2) Hyperpolarization: K+ channels
slow to close, allows cell to
become over negative, need
Na/K pump to restore
Nervous System
• 2) Trace the initiation and propagation of an action potential from a presynaptic
neuron and the transfer of a signal to the postsynaptic neuron. Be sure to
include refractory periods and neurotransmitters in your discussion.
• Figure 11.14.
ARP: CANNOT
produce another AP
while currently
firing–not
dependent on
strength of stimulus
RRP: An AP has the
potential to fire–
depends heavily on
strength of
stimulus.
Nervous System
• 2) Trace the initiation and propagation of an action potential from a presynaptic
neuron and the transfer of a signal to the postsynaptic neuron. Be sure to
include refractory periods and neurotransmitters in your discussion.
• Figure 11.17.
1) AP arrives at Axon
Terminal
2) Stimulates (Voltage
gated) Ca2+ channels
open, Ca2+ influx
3) Ca2+ stimulates
synaptic vesicles
(containing
neurotransmitter) to
undergo exocytosis
(fuse to synapse)
4) Neurotransmitter
diffuse across to
receptors on PSN
5) Binding leads to
graded AP
6) Reuptake diminish
signal
• 3) Explain the role of myelination in signal conduction.
– What is the myelin sheath? What is it made of?
– What are the nodes of Ranvier?
• Figure 11.15
Distinguish between
CNS and PNS
Oligodendrocytes: CNS
Schwann Cells: PNS
Nodes of Ranvier: gaps
Between myelination
Conduct Impulse and
Channel openings.
Nervous System
Muscular System
• 1) Explain the events that take place at the neuromuscular junction that
leads to an action potential.
– Figure 9.8 and Figure 9.9.
• 2) Explain what is meant by excitation-contraction coupling and trace the
events involved.
– Figure 9.11.
Muscular System
• 3) Explain what events must occur on the myofibril level in order for a
muscle contraction and relaxation to take place.
– Explain Power Stroke Process
• Figure 9.12.
1) Cross Bridge Detachment: Myosin
bound to ATP–Myosin at low
energy state (3)
1) Cocking of Myosin: ATP hydrolysis
(ADP+P)–release energy free for
myosin use (4)
1) Cross Bridge Formation: Myosin is
in high energy state–attach to
actin (1)
2) Power Stroke: Myosin and ADP+P
dissociate–allow for ratcheting
movement (2)
Muscular System
• 4) Explain what is meant by the 'graded' nature of muscle response.
– Distinguish fused and unfused tetanus
• Figure 9.15.
Observe:
1) Frequency of stimuli
2) Relaxation ability
Unfused: temporal summation, high
frequency of stimuli, allow for moderate
relaxation but not complete
Fused: even higher frequency of stimuli, do
not allow for any relaxation of muscle
• 5) Explain the length-tension theory.
• Figure 9.22
Actin is overlapped,
cannot pull inward any
further  sarcomere is
too short
Muscular System
NO contact between Actin
and Myosin  too much
stretch in sarcomere
Cardiovascular System
• 1) Trace the electrical events involved in cardiac contraction. Be able to
explain what would happen if one part was extracted.
– What would happen if you had a defective SA node?
– What would happen if you had a defective AV node?
• Figure 18.14.
Defective SA node:
Ectopic focus–AV
takes over and leads
to junctional rhythm
Defective AV node:
Partial to total heart
block–few, if any SA
impulses reach
ventricles
Cardiovascular System
• 2) Explain electrocardiography by drawing a normal EKG and explaining its
elements, and then giving examples of cardiac abnormalities that can be
detected using this diagnostic tool.
– What happens in Junctional Rhythm? Second-degree Heart Block? Ventricular Fibrillation?
• Figure 18.16/18.17
• Figure 18.18
P Wave: Atrial depolarization
(depolarization of SA node)
QRS Complex: Ventricular
Depolarization
T Wave: Ventricular
repolarization
Cardiovascular System
Normal Rhythm
Second-degree Heart Block
Majority of P wave (impulse) is
not sent to the AV node
Which wave is effected?
Junctional Rhythm
SA node is nonfunctional
What wave is absent?
Ventricular Fibrillation
When is this case observed?
Cardiovascular System
• Compare the action potentials between the Nervous, Muscular, and
Cardiovascular Systems.
– What ions are moving and from where?
– When are these ions moving?
– What are the pre- and post-synaptic structures?
– What are the resting membrane potentials?
• Be able to explain differences between Figures 11.11, 9.9/9.10, and 18.12
1) Depolarization: Influx Na+
and rapid fire of AP
2) Plateau: Due to Ca2+ influx
through slow opening Ca2+
channels–cell remains
depolarized very few K+
channels open
3) Repolarization: Ca2+
channels deactivate, K+
channels open, allow K+
efflux to bring cell back to
resting potential