Biology 12

CHAPTER

6

Reflecting

Questions

The Endocrine System

166

When a gymnastic performer

entertains us with a display of

prolonged, intense physical activity,

the performer’s body is being pushed

to the limits of its capabilities. During

the performance, homeostatic

mechanisms work to maintain the

body’s internal environment within

tolerance limits — the narrow range

of conditions within which cellular

processes are able to function at a

normal level.

The endocrine system works in

parallel with the nervous system to

maintain homeostasis. It does so by

releasing chemical substances —

hormones – which in turn trigger

actions in specific target cells. For

example, vigorous exercise triggers

endocrine glands in the brain and

elsewhere to release several different

hormones. These hormones regulate

oxygen consumption, basal metabolic

rate, and the metabolizing of

carbohydrates and fat for energy. As a

result, the rate and depth of breathing

increase, as do heart rate and muscle

contraction. In addition, energy stores

are quickly mobilized. These changes

ensure that fuel is readily available

for an increase in skeletal muscle,

heart, and brain activity, while at the

same time maintaining normal

physiological processes.

In this chapter, you will learn

about the components of the

endocrine system. You will examine

how the nervous system and the

endocrine system interact to regulate

physiology, and how these systems

affect each other’s functions. You will

also explore how, in addition to

maintaining homeostasis, the

endocrine system regulates a wide

range of other biological processes.

These processes include thecontrol

of blood sugar, metabolism, growth,

reproductive development and

function, and other physiological

activities. You will discover how the

body responds to stress, and how

abnormal endocrine function can

result in disease. Finally, you will see

how some major endocrine disorders

can be treated.

Endocrine glands within the brain

secrete hormones to influence

metabolism in other target glands.

This positron emission tomography

(PET) scan relies on a radioactive

tracer, injected into the bloodstream,

to reveal the brain’s metabolic activity.

How does the nervous

system interact with and

regulate endocrine activity?

How do endocrine

hormones maintain

homeostasis in the body?

What are some of the

major treatable diseases

of the human endocrine

system?

Prerequisite

Concepts

and Skills

Before you begin this chapter,
review the following concepts
and skills:

distinguishing between

the structure and

properties of protein and

lipid molecules (Chapter 1,

section 1.2),

explaining the concepts of

homeostasis and dynamic

equilibrium (Chapter 4,

section 4.1),

explaining the difference

between negative and

positive feedback loops

(Chapter 4, section 4.1).

explaining how the

kidneys control water

balance in the body

(Chapter 4, section 4.2),

describing the function of

the parasympathetic and

sympathetic nervous

systems (Chapter 5,

section 5.1), and

describing the nature of

nerve impulses (Chapter 5,

section 5.2 ).