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PART 3 Integration and Control Systems

blood vessels.

32. What part of the CNS stimulates ANS reflexes and integratesthoughts and emotions to produce ANS responses?

33. What is a local reflex? How is it different from otherautonomic reflexes? How does the ENS produce localreflexes?

Predict 6

Important sensory receptors that monitor blood pressure are located inarteries in the chest above the heart and in arteries in the head. WhenSarah does a headstand, gravity causes the blood in her arteries to flowtoward her head, and the blood pressure in the arteries of her chest andhead increases. When Sarah crouches for a short time and then standsup rapidly, gravity causes the blood in her arteries to flow away from herneck and head and toward her feet, and the blood pressure in the arteriesof her chest and head decreases. How do the sympathetic reflexes thatcontrol blood vessels respond when Sarah does a headstand, and howdo the sympathetic reflexes that control blood vessels respond if Sarahsuddenly stands up after crouching for a short time?

16.6 Functional Generalizations About

the Autonomic Nervous System

LEARNING OUTCOME

TABLE 16.4

Cerebrum and limbicsystem

Hypothalamus

Higher Parts of the CNSInfluencing Autonomic Functions

Thoughts and emotions can influence ANSfunctions through the hypothalamus

ANS integrating center that interacts withthe cerebrum, limbic system, brainstem,and spinal cord; also regulates bodytemperature

ANS reflex centers for controlling pupilsize, accommodation, tear production,salivation, coughing, swallowing, digestiveactivities, heart rate and force of contrac-tion, blood vessel diameter, and respiration

ANS reflex centers for regulating defecation,urination, penile and clitoral erection, andejactulation

After reading this section, you should be able to

A. Explain opposite effects, cooperative effects, andgeneral versus localized effects for the ANS.

Several generalizations can be made about the influence of the ANSon effector organs. However, bear in mind that most of the followinggeneralizations have exceptions.

Stimulatory Versus Inhibitory Effects

Both divisions of the ANS produce stimulatory and inhibitory effects.For example, the parasympathetic division stimulates contraction ofthe urinary bladder, causing urination, but inhibits the heart, causing adecrease in heart rate. The sympathetic division stimulates smoothmuscle contraction in blood vessel walls, causing vasoconstriction,but inhibits smooth muscle contractions in the lungs, causing dilationof lung air passageways. Thus, it is not true that one division of theANS is always stimulatory and the other is always inhibitory.

Brainstem

Spinal cord