Honors Biology
Guided Notes: Chapter 28 – Nervous System
Name _________________________________
Animation link: Transmission Across a Synapse (McGraw Hill)
28.6 – 28.9 Signaling BETWEEN Neurons: Synaptic Transmission
THE SYNAPSE
Define:
Example of receiving cell:
Electrical Synapse
Example in Humans:
Chemical Synapse
Example in Humans:
STRUCTURE OF THE CHEMICAL SYNAPSE
Label Diagram and Indicate the Order of Events that Occur During Synaptic Transmission of a Nerve Signal by
a Chemical Synpase (Google: Transmission Across a Synapse mcgraw hill to see an animation)
1.
2.
3.
4.
5.
6.
HOW DOES A SYNAPSE ENSURE THAT SIGNALS PASS ONLY IN ONE DIRECTION, FROM A SENDING NEURON TO A
RECEIVING ONE?
INTEGRATING MULTIPLE SYNAPTIC INPUTS
Excitatory Synaptic Inputs
Inhibitory Synaptic Inputs
What ion channels do excitatory neurotransmitters
open?
What ion channels do excitatory neurotransmitters
open?
What would this do to the membrane potential of the
post-synaptic neuron?
What would this do to the membrane potential of the
post-synaptic neuron?
NEUROTRANSMITTERS
Give the functions and locations each neurotransmitter
Acetylcholine
Epinephrine
Serotonin and dopamine
NEUROTOXINS AND NEURON FUNCTION (Not in your book – but see if you can figure out what is happening in each case)
1. Botulinum toxin (Botox) inhibits release of acetylcholine in motor neurons. What is likely to happen to
nervous transmission in cells exposed to this type of toxin?
2. The pufferfish (fugu) contains the poison tetrodotoxin, which blocks the Na+ channels in neurons. What
specific effect could this toxin have on neuron function?
3. The funnel-web spider produces a toxin that block the Ca+ channels.
a. Can a neuron exposed to this toxin fire an action potential? Explain.
b. Can a neuron transmit a signal across the synapse using neurotransmitters? Explain.
REVIEW QUESTIONS
1. What role do neurotransmitters play in neuron communication? (28.6)
a. Neurotransmitters are chemical signals that carry information across a gap called the synaptic
cleft and may or may not generate an action potential in neighboring neurons.
b. They regulate rhythmic muscle contractions, such as those that occur in the small intestine.
c. They relay electrical signals from one axon to the next axon.
d. They are accepted into the receiving cell, where they initiate more action potentials.
2. Which of the following statements about the transmission across a typical chemical synapse is FALSE?
(28.6)
a. Neurotransmitter molecules bind to receptors in the receiving neuron's plasma membrane.
b. Vesicles containing neurotransmitter molecules diffuse to the receiving neuron's plasma
membrane.
c. Neurotransmitter molecules are stored in vesicles in the axon.
d. Action potentials trigger chemical changes that make the neurotransmitter vesicles fuse with the
plasma membrane of the receiving neuron.
3. How are neurons structurally adapted to chemically transmit impulses to neighboring neurons? (28.6)
a. They have Schwann cells that surround axons.
b. They have numerous dendrites.
c. They have multiple synaptic termini containing containing neurotransmitter substances within
synaptic vesicles.
d. They have numerous nodes of Ranvier.
4. A nerve poison that blocked neurotransmitter receptors on the dendrites would _____. (Module 28.6)
a. inhibit the regeneration of the neurotransmitter for use by the sending neuron
b. inactivate the enzyme that degrades the neurotransmitter
c. cause continued stimulation of the membrane of the receiving neuron
d. prevent binding of the neurotransmitter to its receptor and possibly prevent transmission
across the synaptic cleft
5. Which of the following statements about chemical synapses is FALSE? (28.7)
a. Neurotransmitters that bind to receptors controlling excitatory membrane channels increase the
tendency to develop action potentials in the neighboring neuron.
b. Release of neurotransmitter from presynaptic neuron occurs when K+ ions trigger exocytosis.
c. Receiving neurons receive either inhibitory or excitatory signals.
d. Neurotransmitters that bind to receptors controlling inhibitory membrane channels decrease the
tendency to develop action potentials in the neighboring neuron.
6. Acetylcholinesterase is the enzyme that degrades acetylcholine. What effect on nerve transmission to a
skeletal muscle would occur following the administration of a chemical that inhibited
acetylcholinesterase? (28.8)
a. Synaptic transmission would not be terminated and continued muscle contraction would occur.
b. There would be no effect.
c. It would be identical to giving an anesthetic, but it would last permanently.
d. Extra excitatory signals would occur in the muscle.
7. Many neurotransmitters also function as _____ in a different body system. (28.8)
a. endorphins
b. biogenic amines
c. hallucinogens
d. hormones
8. In humans, making more serotonin available to brain cells typically _____. (28.9)
a. increases the stimulatory effects of caffeine
b. causes the heart to beat faster
c. produces an effect on mood
d. depresses the central nervous system