Abnormal Psychology

Understanding Psychological Disorders: The Neuropsychosocial Approach 35

Not surprisingly, such complexity leads to many opportunities for the function-

ing of the brain to go awry. The brain is the organ of thinking, feeling, and behavior,

and thus it must play a key role in psychopathology. In the following sections, we

discuss the brain so that you can begin to understand the neurological aspects of

specifi c psychological disorders that we consider later in the book. We start with the

big picture by considering the overall structure of the brain and its organization into

large systems. Then we turn to increasingly more detailed components, considering

how individual brain cells interact within these systems.

A Quick Tour of the Nervous System

Psychopathology involves defi cits in how a person thinks, feels, and behaves.

The brain, of course, is ultimately responsible for all of these functions. Let’s

briefl y consider how different parts of the brain contribute to cognitive and

emotional capacities when the brain is structured and functions normally. In

later chapters, when we need to know more to understand a specifi c psychologi-

cal disorder, we’ll look more closely at specifi c parts of the brain and how they

can malfunction.

The Central Nervous System and the Peripheral Nervous System

The central nervous system (CNS) has two parts: the brain and the spinal cord. The

CNS is the seat of memory and consciousness, as well as perception and voluntary

action (Smith & Kosslyn, 2006). However, the CNS is not the only neurological

foundation of our internal lives. The peripheral nervous system (PNS) also plays an

important role and is of particular interest in the study of psychopathology.

The Autonomic Nervous System

Like the CNS, the PNS is divided into two parts,

in this case the sensory-somatic nervous system and

the autonomic nervous system (see Figure 2.1). The

sensory-somatic nervous system is involved in con-

necting the brain to the world, via both the senses

(inputs) and the muscles (outputs). The autonomic

nervous system (ANS) is probably of greater rele-

vance to psychopathology, in part because it plays a

key role in how we respond to stress (as we’ll discuss

shortly). The ANS controls many involuntary func-

tions, such as those of the heart, digestive tract, and

blood vessels (Goldstein, 2000; Hugdahl, 2001).

The ANS itself has two major components: the sym-

pathetic nervous system and the parasympathetic

nervous system. Thesympathetic nervous system

revs you up so that you can respond to an emer-

gency: It speeds up the heart (providing more blood

and oxygen to the limbs) and dilates the pupils of

the eyes (making you more sensitive to light). The

sympathetic system also slows down functions that

are not essential in an emergency, such as those in-

volved in digestion. The sum result of the sympa-

thetic nervous system’s being activated is called the

fi ght-or-fl ight response, (or the stress response, be-

cause it occurs when people experience stress).

As part of the fight-or-flight response, the

hypothalamic-pituitary-adrenal axis (HPA axis)

manages the production of the hormone cortisol,

which readies the muscles for physical exertion by helping the body release fuel

more effectively. Under chronic stress, a person’s level of cortisol often doesn’t

2.1 • The Nervous System The autonomic nervous

system (ANS) is part of the peripheral nervous system (PNS), and

malfunctioning of the ANS can produce abnormal responses to stress.

Figure 2.1

21 Th N S t hi

g

Spinal cord Brain Sensory-somatic

nervous system

Autonomic

nervous system

Nervous system

Central

nervous system

Peripheral

nervous system

Sympathetic

nervous system

Parasympathetic

nervous system