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Lecture

BIOL 111 Lecture Notes - Aposematism, Chitin, Trachea


Department
Biology (Sci)
Course Code
BIOL 111
Professor
Multiple

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Bio 111 Alanna Houston
October 30, 2007
-All action potentials have the same magnitude for a given neuron
-Depolarization, repolarization, hyperpolarization
-Impulse travels along axon as ions channels open and close
-At the end of the axon, there is a synapse (junction between the
axon terminal and the next neuron)
-2 types:
oElectrical Synapse
oChemical Synapse
Neurotransmitters are released (can have an
excitatory synapse or inhibitory synapse)
Neurotransmitters:
-released into the synaptic cleft
-Neurotransmitters bind to receptors:
oOn the next neuron
oOr a muscle cell or gland
-Can be excitatory (ex. Acetylcholine)
oCause depolarization
-Can be inhibitory (ex. GABA)
oCause hyperpolarization
Synapse:

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Bio 111 Alanna Houston
-If acetylcholinesterase is lacking, with ATP muscle keeps
contracting. Without ATP, it would only contract once
Drugs interacting with excitatory neurotransmitters:
-nerve gases (ex. Sarin)
oinhibit acetylcholinesterase
oacetylcholine is not broken down and remains in synapse
oskeletal muscles contract uncontrollably causing paralysis
-Antidepressants
oBlock the reuptake of excitatory neurotransmitters (ex.
Seratonin)
oNeurotransmitters remain in synapse longer
oImpulses transmitted more frequently
Drugs causing inhibitory effects at synapses:
-anti-anxiety drugs (ex. Xanax)
omimic the actions of natural inhibitory neurotransmitters
(ex. GABA)
oOpen Cl- channels causing hyperpolarization (more negative
interior)
oGreater stimulus needed to reach threshold
-Tetrodoxin
oBlock Na+ channels and prevent depolarization
oFound in a wide variety of animals
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Bio 111 Alanna Houston
oDeath by diaphragm paralysis
-Anesthetics (ex. Novocain)
oInhibit local movement of Na+ through channels
oPrevent depolarization
Neuromuscular Junctions
MUSCLE TISSUE
-present in all animals except sponges
-composed of proteins
-contractions triggered by motor neuron depolarization
-3 types
-Smooth muscle is found lining internal organs
-Cardiac muscle is able to generate its own action potential (called
the pacemaker)
-
-Skeletal muscle cells:
oContractile unit = sarcomere (actin – thin filaments, myosin
– thick filaments)
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