Brain & Cranial Nerves

The BrainRanges 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

CortexWhere 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