Download Exam 2 Review Essay KEY

Practice Exam 2
Nervous, Muscle, & Cardiovascular Systems
Supplemental Instruction
Iowa State University
Leader:
Course:
Instructor:
Date:
Kristina
AnS 214
Selsby
3/5/2014
NERVOUS SYSTEM:
1) Explain how EPSPs and IPSPs work to influence events at the post-synaptic neuron. Also,
give examples of synaptic relationships and whether they are generally EPSP’s or IPSP’s.
EPSP
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IPSP
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Neurotransmitters bind to open ligand gated Na+ and K+ channels
Depolarizes the membrane – graded potential moves through cell
Triggers action potential at axon hillock
Opens voltage-gated channel
Axodendritic
Neurotransmitters bind to open ligand gated Na+ and K+ channels
Hyperpolarizes the membrane – more K+ moving out than Na+ moving in
Reduces the potential for an action potential – must have a greater positive potential to
overcome hyperpolarization
Axosomatic
Axoaxonic
2) Graph and describe an action potential. Be sure to include refractory periods, Na release, and
K release in your answer.
Supplemental Instruction
1060 Hixson-Lied Student Success Center  294-6624  www.si.iastate.edu
*Be sure to know refractory periods as well
3) Explain the role of myelination in signal conduction. Also, note a difference between the CNS
and the PNS in your answer.
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Fat cells wrap plasma membranes around axon of neuron
Speeds up conduction by not allowing Na+ out or K+ in at high levels under myelinated
areas
Low concentration of ion channels under myelination keeps ion concentrations fairly
constant
CNS – oligodendrocytes, one wraps around many nerves
PNS – schwann cells, one schwann cell per nerve
4) Describe how an action potential is propagated from the pre-synaptic neuron to the postsynaptic neuron.
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Starts at the presynaptic axon terminal
Synaptotagmin protein binds Ca+2 and promotes fusion of synaptic vesicles with the
axon membrane
Exocytosis of neurotransmitter
Neurotransmitter binds to receptors on postsynaptic neuron
Causes IPSP or EPSP
MUSCLE SYSTEM:
1) Explain the events that take place at the neuromuscular junction generating an action
potential. Explain how that potential is propagated along the muscle cell in relation to the
triad (t-tubule and two terminal cisternae).
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ACh released from neuron binds to receptors on muscle to cause an EPSP
Opens ligand gated channels that release Na+ and K+
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Generates an action potential if threshold is reached
Action potential moves on the outside of the muscle cell into the t-tubule (still outside the
cell)
Positively charged action potential attracts electron dense feet away from the opening to
the sarcoplasmic reticulum/terminal cisternae
Ca+2 released into the cell and the cross bridge cycle can take place
2) Explain what is meant by excitation-contraction coupling. Compare and contrast the steps
involved in EC coupling in skeletal muscle and cardiac muscle.
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Action potential leads to sliding of myofilaments and contraction of the sarcomere
Action potential propagates to t-tubules along muscle cells
Electron dense feet move allowing the release of Ca+2 into the muscle cell
Ca+2 binds to TNc
Troponin changes shape to physically move tropomyosin away from the active sites
Myosin can bind to actin on the uncovered active sites and the muscle contracts
May be a Ca+2 surge in muscle, but definitely in cardiac cells
3) Explain what events must occur on the myofibril level in order for a muscle contraction and
relaxation to take place. In your answer draw the four stages of the cross-bridge cycle.
Indicate which stage is high or low energy.
4) What happens to motor units with age and what are the implications of this?
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Motor neurons begin to die from non-use
This leaves muscle fibers in the muscle without any innervation
They are then recruited by other motor neurons effectively increasing the size of the
smallest motor units in the muscle
Lose the mosaic pattern of muscle and fine motor skills as the motor units get larger
CARDIOVASCULAR SYSTEM:
1) Trace the electrical events involved in cardiac contraction. Be able to explain what would
happen if one part was extracted.
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SA node depolarizes – pacemaker of a normal heart
Conducts signal to AV which connects the atrium to the ventricle
Signal is then conducted to the AV bundle/bundle of His
Continues into the bundle branches in the septum of the heart, carries the signal to the
apex of the heart
Purkinje fibers in the apex and outer walls of the ventricles carry the signal from the
bottom up
Remove SA node – AV node takes over, ectopic focus, heart rate around 40-60 bpm
Remove AV node – ventricles will not contract, not compatible with life
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.
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P wave – atrial depolarization
QRS complex – ventrical depolarization, atrial repolarization
T wave – ventrical repolarization
Fibrillation
Arrhythmia
Premature ventricular contraction
Defective SA node
3) Describe the relationship between exercise and cardiac output. What other factors can affect
CO?
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Exercise increases heart rate due to sympathetic activity
This increases the venous return of blood to the heart and an increase in stroke volume as
the heart fills with more blood
Increase in stroke volume and heart rate increase cardiac output
Can cause hypertrophy of cardiac cells – larger stroke volume with a stronger muscle
contraction, lower heart rate for same cardiac output
Age, gender, body temperature
4) Compare the action potentials between the Nervous, Muscular, and Cardiovascular Systems.
Nervous
 Na+ and K+ movement
 EPSP or IPSP
 Many neurotransmitters
Muscles
 Na+ and K+ movement
 ACh for muscle contractions
 Ca+2 thought to be part of de/repolarization process
Cardiac
 Na+ and K+ movement
 Ca+2 definitely moves during action potential propagation
 Slower repolarization due to Ca+2
 Long absolute refractory period due to Ca+2