The Brain

The Brain

~35 billion neurons Adult brain contains almost 98% of neural

tissue in the body Weighs about 1.4 kg (3lbs) Volume of 1200 cc (71 in3) No correlation between brain size and

intelligence

Three Main Structures

1. Cerebrum 2. Cerebellum 3. Brain Stem

The Cerebrum

A. Conscious thought and intellectual function originate B. Outer Surface composed of:

a. Gyri- elevated ridges (increase surface area)b. Sulci- shallow depressionsc. Fissures- deep grooves

C. Two Cerebral Hemispheres covered by a cerebral cortex1. Right Hemisphere2. Left Hemisphere

~Hemispheres are united by a corpus callosum - major route of communication between the

hemispheres.

The Cerebrum

Hemisphere Control

Right Side  judging the position of things

in space knowing body position understanding and

remembering things we do and see

putting bits of information together to make an entire picture

controls the left side of the body

Left Side understanding and use of

language (listening, reading, speaking and writing)

memory for spoken and written messages

detailed analysis of information

controls the right side of the body

LEFT BRAIN DAMAGEProblems seen on the right side of the body.

RIGHT BRAIN DAMAGEProblems seen on the left side of the body.

                                               

                                          

                                                 

                                          

Cerebral Hemispheres

Separated by a deep longitudinal fissure (central sulcus extends laterally)

Divided into lobes named for bones of the skull:Frontal LobeTemporal LobeParietal LobeOccipital Lobe

Frontal Lobe

Primary Motor Cortex:

- voluntary motor function Frontal Lobe:

problem solving Spontaneity Memory Language Judgment impulse control Personality

Vulnerable to injury

Parietal Lobe

Primary Sensory Cortex:- sensory somatic information

Location for visual attention. Location for touch perception. Goal directed voluntary

movements. Manipulation of objects. Integration of different senses

that allows for understanding a single concept.

Temporal Lobe

Hearing ability Memory acquisition Some visual

perceptions Categorization of

objectsAuditory Cortex- hearingOlfactory Cortex- smelling

Occipital Lobe

Visual Cortex- Vision

~not particularly vulnerable to injury because of their location at the back of the brain

~although any significant trauma to the brain could produce subtle changes to our visual-perceptual system

The Limbic System

Contains several cerebral nuclei, gyri, and tracts that border the cerebrum and the diencephalon.

Contains cerebral centers concerned with:1. sense of smell2. long-term memory storage- Hippocampus3. emotional states (flight and fight)- Amygdaloid4. control of reflex movements that can be consciously activated

Diencephalon (Forebrain)

Central Core of the forebrain Switching and relay centers that integrate the

conscious and unconscious sensory and motor pathways.

Composed of the: 1. Thalamus 2. Hypothalamus3. Epithalamus

Thalamus

Constitutes the top of the brain stem Paired egg shaped masses Afferent impulses from all senses converge and synapse

in the thalamus Impulses are sorted out, edited, and relayed as a group Coordination of voluntary and involuntary motor

commands Plays an important role in mediating sensation, motor

activities, learning and memory.

Hypothalamus

Located between the thalamus Contains centers associated with emotions of rage, pleasure, pain,

thirst, hunger, and sexual arousal 1. Adjusts and coordinates the activities of autonomic centers in the

pons and medula oblongata 2. Coordinates neural and endocrine activities 3. Produces a variety of hormones including antidiuretic hormone

(ADH) and oxytocin 4. Coordinates voluntary and autonomic functions 5. Maintains normal body temperature 6. Regulates sleep, sleep cycle, hunger, blood pressure, heart rate,

breathing depth

Epithalamus

Pineal gland: extends from the posterior border and secretes melatonin- involved in sleep regulation, and mood

Choroid plexus- structure that secretes CSF (cerebrospinal fluid)

Midbrain

Located between the diencephalon and the pons Midbrain structures include:

1. various nuclei and buncles of ascending and descending nerve fibers.

2. control involuntary motor reflexes to sudden visual and auditory stimuli (loud noise, bright light)

Reticular Formation- network of interconnected nuclei that extend the length of the brain stem.

- regulation of involuntary functions-maintains position and posture

Pons (Hindbrain)

Bulging brainstem region between the midbrain and the medulla oblongata

Fibers of the pons:1. Connect higher brain centers and the spinal

cord

2. Relay impulses between the motor cortex and the cerebellum

Medulla Oblongata

Most inferior part of the brain stem Physically connects the brain with the

spinal cord Cardiovascular control center- adjusts

force and rate of heart contraction. Respiratory centers- control rate and

depth of breathing

Cerebellum

Makes rapid adjustments to muscle tone and position to maintain balance and equilibrium

Programs and fine-tunes voluntary and involuntary movements

Plays a role in language and problem solving Recognizes and predicts sequences of events Maybe permanently damaged by stroke or

temporarily affected by alcohol

Gray Matter

1. Adjusts the postural muscles of the body:1. Coordinates rapid automatic adjustments to

maintain balance and equilibrium

2. Programs and “fine-tunes” voluntary and involuntary movements

- refines learned movements patterns

White Matter

Arbor Vitae- (tree of life) which links Cerebellar cortex (gray matter) to the-1. Cerebellar Peduncles-

which link the cerebellum to the mesencephalondiencephaloncerebrum

2. Transverse fibers1. Like the commissural fibers in the cerebrum

- link the cerebellar hemispheres and extend into the pons and medulla oblongata.