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Module 1.3a

This feedback system (brain ‡ pituitary ‡ other glands ‡ hormones ‡ body and brain)
reveals the intimate connections between the nervous and endocrine systems. The nervous
system directs endocrine secretions, which then affect the nervous system. Conducting and
coordinating this whole electrochemical orchestra is that flexible maestro we call the brain.

®
AP Science Practice Check Your Understanding

Examine the Concept Apply the Concept
▶ ▶Explain the relationship between the nervous and endocrine ▶ ▶Compare and contrast the nervous and endocrine systems.
Distributed by Bedford, Freeman & Worth Publishers. Not for redistribution.
systems. ▶ ▶Do you remember feeling the lingering effects of a hormonal
response, such as anger, after some particularly aggravating
event? Describe how it felt. How long did it last?
Answers to the Examine the Concept questions can be found in Appendix C at the end of the book.
Copyright © Bedford, Freeman & Worth Publishers.

Module 1.3a REVIEW

1.3-1 What are neurons, and how do they transmit • If incoming signals are strong enough, the receiving neu-
information? ron generates its own action potential and relays the mes-
sage to other cells.
• Neurons are the elementary components of the nervous sys-
tem, the body’s speedy electrochemical information system. 1.3-3 How do neurotransmitters influence behavior,
• A neuron consists of a cell body and its branching fibers. and how do drugs and other chemicals affect
It receives signals through its often bushy, branching den- neurotransmission?
drites and sends signals through its axons. • Neurotransmitters travel along designated pathways in the
• Some axons are encased in a myelin sheath, which enables brain and may influence specific behaviors and emotions.
faster transmission. • Acetylcholine (ACh) affects muscle action, learning, and
• Glial cells support, nourish, and protect neurons and also memory.
play a role in learning, thinking, and memory. • Endorphins are natural opioids released by the body in re-
• If the combined signals received by a neuron exceed a sponse to pain and exercise.
minimum threshold, the neuron fires, transmitting an • Drugs and other chemicals affect brain chemistry at synapses.
electrical impulse (the action potential) down its axon by
means of a chemistry-to-electricity process. • Agonists increase a neurotransmitter’s action, and may do
• Neurons need a short rest called the refractory period, after so in various ways.
which they can fire again. The neuron’s reaction is an • Antagonists decrease a neurotransmitter’s action by block-
all-or-none response. ing its production or release.

1.3-4 How does the endocrine system transmit
1.3-2 How do nerve cells communicate with other
nerve cells? information and interact with the nervous system?
• The endocrine system secretes hormones into the blood-
• When action potentials reach the end of an axon (the stream, where they travel throughout the body, enabling
button-like axon terminals), they stimulate the release them to affect other tissues, including the brain.
of neurotransmitters. These chemical messengers carry a
message from the sending neuron across a synapse to re- • In an intricate feedback system, the brain’s hypothala-
ceptor sites on a receiving neuron. mus influences the endocrine system’s pituitary gland,
• The sending neuron, in a process called reuptake, then which influences other glands, which release hormones,
which in turn influence the brain.
normally reabsorbs the excess neurotransmitter mole-
cules in the synaptic gap.

The Neuron and Neural Firing: Neural Communication and the Endocrine System Module 1.3a 37

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