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SYMPATHETIC PARASYMPATHETIC
Figure 1.2-2 NERVOUS SYSTEM NERVOUS SYSTEM
The dual functions of the (arousing) (calming)
autonomic nervous system
Pupils: Pupils:
The autonomic nervous system dilate Brain contract
controls the more autonomous (or
self-regulating) internal functions.
Its sympathetic division arouses
the body and expends energy. Its Heart:
parasympathetic division calms accelerates Spinal Heart:
slows
the body and conserves energy, heartbeat cord heartbeat
allowing routine maintenance
activity. For example, sympathetic
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stimulation accelerates a Stomach,
person’s heartbeat, whereas pancreas, and Stomach,
parasympathetic stimulation duodenum: pancreas, and
slows it. inhibit duodenum:
digestion stimulate
digestion
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Liver:
stimulates
glucose release Gallbladder:
stimulates
bile release
Adrenal glands:
stimulate
secretion of
epinephrine and
norepinephrine Bladder:
contracts

Bladder:
relaxes
Genitals:
Genitals: allows
stimulates blood flow
ejaculation in
males

®
AP Science Practice Check Your Understanding
Examine the Concept
▶ ▶Match the type of neuron (i–iii) to its description (a–c).
Type: Description:
i. Motor neurons a. Carry incoming messages from sensory receptors to the CNS.
ii. Sensory neurons b. Communicate within the CNS and process information between incoming and outgoing
iii. Interneurons messages.
c. Carry outgoing messages from the CNS to muscles and glands.

Ballistic stress In 2018, Hawaiians
received this terrifying alert, amid
concerns about the launch of North
Korean nuclear warheads. “We fully
felt we were about to die,” reported
one panicked mother (Nagourney
et al., 2018). Thirty-eight minutes later,
the alert was declared a false alarm.
▶ ▶Explain how the ANS was involved in Hawaiians’ terrified responses, and in calming their bodies once they realized it was a false alarm.

(continued )
24 Unit 1 Biological Bases of Behavior

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