Human Physiology, 14th edition (2016)

The Central Nervous System 211

of the body. Typical maps of these regions ( fig.  8.7 ) show an

upside-down picture of the body, with the superior regions of

cortex devoted to the toes and the inferior regions devoted to

the head.

A striking feature of these maps is that the areas of cortex

responsible for different parts of the body do not correspond

to the size of the body parts being served. Instead, the body

regions with the highest densities of receptors are represented

by the largest areas of the sensory cortex, and the body regions

with the greatest number of motor innervations are represented

by the largest areas of motor cortex. The hands and face, there-

fore, which have a high density of sensory receptors and motor

innervation, are served by larger areas of the precentral and

postcentral gyri than is the rest of the body.

The temporal lobe contains auditory centers that receive

sensory fibers from the cochlea of each ear. This lobe is also

Figure 8.7 Motor and sensory areas of the cerebral cortex. ( a ) Motor areas that control skeletal muscles are shown in
yellow. This region is specifically known as the primary motor cortex (discussed later in this chapter). ( b ) Sensory areas that receive
somatesthetic sensations are shown in purple. Artistic license has been used in rendering part ( b ), because the left hemisphere
receives input primarily from the right side of the body.

Somatosensory cortex

Motor cortex

Insula

Salivation

Vocalization

Mastication

Facial

expression

Thumb,

fingers,

and hand

Lower

arm

Upper

arm Trunk

Pelvis

Upper leg

Lower leg

Foot

and toes

Tongue

and pharynx

Insula

Hand, fingers,

and thumb

Upper

arm

Upper PelvisTrunk

leg

Lower

leg

Foot

and toes

Genitals

Neck

Lower

arm

Upper

face

Lips

Teeth

and gums

Parietal lobes

Central sulcus

Frontal lobes

Motor cortex

(a) (b)

Somatosensory cortex

Central sulcus

Swallowing Longitudinal

fissure

Table 8.1 | Functions of the Cerebral Lobes

Lobe Functions

Frontal Voluntary motor control of skeletal muscles; personality;

higher intellectual processes (e.g., concentration,

planning, and decision making); verbal communication

Parietal Somatesthetic interpretation (e.g., cutaneous and

muscular sensations); understanding speech

and formulating words to express thoughts and

emotions; interpretation of textures and shapes

Temporal Interpretation of auditory sensations; storage (memory)

of auditory and visual experiences

Occipital Integration of movements in focusing the eye; correlation

of visual images with previous visual experiences and

other sensory stimuli; conscious perception of vision

Insula Memory; sensory (principally pain) and visceral integration