Brain & Cranial Nerves
The Brain
 Ranges
from 750 cc to 2100 cc
 Contains
almost 98% of the body’s
neural tissue
 Average
weight about 1.4 kg (3 lb)
6 Major Regions of the
Brain

Cerebrum

Cerebellum

Diencephalon

Mesencephalon

Pons

Medulla oblongata
The Brain
Cerebrum

Largest part of brain

Controls higher mental functions

Divided into left and right cerebral
hemispheres

Surface layer of gray matter (neural
cortex)
Cerebral Cortex
3 Functional Principles of
the Cerebrum

1. Each cerebral hemisphere receives
sensory information from, and sends
motor commands to, the opposite
side of body
3 Functional Principles of
the Cerebrum

2. The 2 hemispheres have different
functions although their structures are
alike
3 Functional Principles of
the Cerebrum

3. Correspondence between a specific
function and a specific region of
cerebral cortex is not precise
Motor & Sensory Areas of
the Cerebral Cortex
 Where
are the motor,
sensory, and association
areas of the cerebral cortex, and
what are their functions?

Central sulcus separates motor and sensory areas
Motor Areas

Precentral gyrus of frontal lobe:
 directs voluntary movements

Primary motor cortex:
 is the surface of precentral gyrus

Pyramidal cells:
 are neurons of primary motor cortex
Sensory Area

Postcentral gyrus of parietal lobe:
 receives somatic sensory information
(touch, pressure, pain, vibration, taste,
and temperature)

Primary sensory cortex:
 surface of postcentral gyrus
Special Sensory Cortexes

Visual cortex:
 information from sight receptors

Auditory cortex:
 information from sound receptors

Olfactory cortex:
 information from odor receptors

Gustatory cortex:
 information from taste receptors
Sensory Association Areas

Somatic sensory association area:
 interprets input to primary sensory cortex
(e.g., recognizes and responds to touch)

Visual association area:
 interprets activity in visual cortex

Auditory association area:
 monitors auditory cortex
Other Integrative Areas

Speech center:
 is associated with general interpretive area
 coordinates all vocalization functions

Prefrontal cortex of frontal lobe:
 integrates information from sensory
association areas
 performs abstract intellectual activities
(e.g., predicting consequences of actions)
Hemispheric
Lateralization

Functional
differences between
left and right
hemispheres

Each cerebral
hemisphere performs
certain functions not
performed by the
opposite hemisphere
The Left Hemisphere

In most people, left brain (dominant
hemisphere) controls:
 reading, writing, and math
 decision-making
 speech and language
The Right Hemisphere

Right cerebral hemisphere relates to:
 senses (touch, smell, sight, taste,
feel)
 recognition (faces, voice inflections)
Cerebellum

Second largest part of brain

Coordinates repetitive body
movements

2 hemispheres

Covered with cerebellar cortex
The Cerebellum

An autonomic processing center
Functions of the
Cerebellum
1.
Adjusts postural muscles
2.
Fine-tunes conscious and
subconscious movements
Structures of the
Cerebellum
Structures of the
Cerebellum

Folia:
 surface of cerebellum
 highly folded neural cortex

Anterior and posterior lobes:
 separated by primary fissure
Structures of the
Cerebellum

Cerebellar hemispheres:
 separated at midline by vermis

Vermis:
 narrow band of cortex

Flocculonodular lobe:
 below fourth ventricle
Purkinje Cells

Large, branched cells

Found in cerebellar cortex

Receive input from up to 200,000
synapses
Arbor vitae

Highly branched, internal white
matter of cerebellum

Cerebellar nuclei:
 embedded in arbor vitae
 relay information to Purkinje cells
The Peduncles

Tracts link cerebellum with brain
stem, cerebrum, and spinal cord:
 superior cerebellar peduncles
 middle cerebellar peduncles
 inferior cerebellar peduncles