AP Biology
Nervous System
Notes Ch.
Organization of Nervous Systems
Page 1012, Fig. 48.2
Information Processing
p. 1013, fig. 48.3
Reflexes: Sensory neuron to spinal cord to motor neuron.
1. The reflex is initiated by tapping the tendon connected to the
quadriceps (extensor) muscle.
2. Sensors detect a sudden stretch in quadriceps.
3. Sensory neurons convey the information to the spinal cord.
4. The sensory neurons communicate with motor neurons that
supply the quadriceps. The motor neurons convey signals
to the quadriceps, causing it to contract and jerking the
lower leg forward.
5. Sensory neurons from the quadriceps also communicate with
interneurons in the spinal cord.
6. The interneurons inhibit motor neurons that supply the
hamstring (flexor) muscle. This inhibition presents the
hamstring from contracting, which would resist the action
of the quadriceps.
Neuron Structure
p. 1014, fig 48.5
Know parts and functions.
Schwann Cells
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Action Potentials
Varying force of sensory input is transmitted as greater or fewer numbers of
action potentials.
The amplitude of the A.P. does not change.
The action potential is “All or None.”
Conduction of an Action Potential
The movement of the ion channels to send the action potential along the
length of the neuron is like a stadium wave.
To participate in a stadium wave you:
1. remain sitting until the wave reaches you.
2. the person next to you begins to stand and you follow just after
3. you stand and throw up your hands
4. bring your hands down, sit down
5. watch the wave move around the stadium
6. wait for another wave.
Use the following events to align with the analogy.
a) Na+/K+ pump returns ions to original position, repolarizing the axon.
b) Na+ ions flood in, a local change (permeability to ions)
c) triggering depolarization of neighboring membrane
d) Impulse moves along axon to synaptic terminals
e) Resting membrane potential X 2
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How do Schwann cells improve the speed of conduction of an action potential? Describe saltatory conduction.
A Chemical Synapse
Be able to narrate the diagram. p. 1022
How are neurotransmitters involved?
Neurotransmitters are secreted from the presynaptic membrane into the synaptic gap where they diffuse to the postsynaptic
membrane and bind to receptors there. This may open ion channels that can trigger an action potential (Na+ is excitatory) or
open channels for ions that decrease the tendency to develop action potentials (Cl- or K+ are inhibitory). Alcohol, nicotine,
and caffeine are drugs that alter the effects of neurotransmitters.
Neurotransmitter
Acetylcholine
Functional Class
Excitatory to vertebrate
skeletal muscles;
excitatory or inhibitory at
other sites
Gases
Amino
Acids
Biogenic
Amines
Epinephrine
Notes
Most common
neurotransmitter in verts
and inverts.
Drugs
Nicotine
Also a hormone
Norepinephrine
excitatory or inhibitory
Dopamine
Generally excitatory
Also a hormone
Affect sleep, mood,
attention, and learning.
Serotonin
Generally inhibitory
GABA
Inhibitory
Ritalin is chemically similar to
norepinephrine and dopamine. Block
the reuptake of these transmitters.
LSD, mescaline produce hallucinatory
effects by binding brain receptors for
serotonin and dopamine.
Schizophrenia drugs block receptors
for dopamine.
Prozac treats depression by enhancing
the effect of serotonin by inhibiting its
uptake after release into synaptic gap.
Tranquilizers activate the receptors
increasing its effect at inhibitory
synapses.
NO,
CO
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