The Brain:Our Control Center

Unit II

The Three Brains

• Hindbrain – Found at the rear base of the brain & involved in the basic processes of life.– Responsible for automatic and survival functions– Three Parts• Medulla• Pons• Cerebellum

The Three Brains• Midbrain – Located just above the hindbrain

and relays sensory information (vision & hearing) upward.– Contains the Reticular Activating System

• Forebrain – Located at the front of the brain and controls complex emotions, thoughts, and movements.– Most highly developed portion of the brain– 4 Parts• Thalamus, Hypothalamus, Cerebrum, & Limbic System

Three Brains

Hindbrain• Medulla – controls breathing, heart rate,

swallowing, digestion – vital life functions• Pons – Involved in regulating body movement,

attention, sleep, alertness, and facial expressions.• Cerebellum – Involved in balance and

coordination.– Effected by alcohol (DUI test)

Midbrain• Reticular Activating System (RAS) – Stretches

from the hindbrain through the midbrain into the lower part of the forebrain.– The “ignition” system of the brain– Coordinates basic sensory information involving

attention, sleep, & arousal (heart rate/blood pressure)– Damage to the RAS can result in a permanent coma.– “Adapts” to sounds (ex. Sounds in the city)– Alcohol reduces activity

Midbrain

Forebrain• Thalamus – Relay station for sensory stimulation– Sorts & sends messages from the sense organs to the

cerebral cortex for interpretation.• Hypothalamus – regulates vital functions – body

temperature (homeostasis), storage of nutrients, motivation, and emotion– Hunger, thirst, sexual behavior, caring for offspring and

aggression are regulated.– Controls the release of hormones from the pituitary

gland.

Forebrain• Cerebrum – 70% of the brain’s weight– Receives sensory information– Transmits voluntary (conscious) motor information– Cerebral Cortex – the thinking center of the brain• Wrinkled surface of the brain• Involved in memory, language, emotions, complex motor

functions, perception, etc.

– Corpus Callosum – Connects the two brain hemispheres of the cerebral cortex

Forebrain

• Limbic System – Located in the core of the forebrain on the inner edge of the cerebrum– Involved in learning & memory, emotion, hunger,

sex & aggression– Two Structures:• Amygdala

– Memory during emotional events– Fear & Aggression

• Hippocampus– Memory Formation

Brain Lobes• Occipital Lobe (Back Of The Brain)– Main center for visual processing– Enables experiencing shapes, color, and motion.– Damage can cause blindness

• Parietal Lobes (Top & Rear)– Involved in touch sensation (integrates sensory

systems)– Touch, Temperature, & Pressure– Damage can destroy sense of touch

Brain Lobes• Temporal Lobe (Side, Behind Ears)– Hearing/Auditory Area• Wernicke’s Area

– Involves the understanding of written & spoken language– Damage results in difficulty understanding written/spoken language– Can speak quickly & easily but speech often makes no sense

• Broca’s Area– Involves the production of speech– Damage involves difficulty speaking

• Damage to areas causes “aphasia”– Trouble understanding/Producing Language

Brain Lobes

• Frontal Lobe (behind forehead)– Executive Center – Higher Mental Processes• Planning, Social Skills, Emotional Control, Problem

Solving & Abstract Thinking

– Motor Skills - Involved in the coordination of movement

Cerebral Hemispheres

• Corpus Callosum – Collection of nerve bundles that carries messages between the two hemispheres

• Each hemisphere controls the opposite side of the body.– Ex. Left hemisphere controls right side of the body

Cerebral Hemispheres• Lateralization – Specialization of a

hemisphere in a particular function– Left Hemisphere – Generally

handles verbal processing, language, speech, reading & writing

– Right Hemisphere – Generally handles nonverbal processing, spatial relations, music, and visuals

– People often thought of as “right or left-brained”• Misconception

• Primary sensory & motor areas are symmetrical.

“Left-Brained” Or “Right-Brained”

Split Brain Patients

• Patients who suffer from severe epileptic seizures have their corpus callosum severed

• Epileptic Seizures – Bursts of abnormal neuron firings that generally occur in one hemisphere and then spread to the other

• Subtle effects on brain functions– Ex. Able to describe verbally an

object in their left hand but not in their right hand.

Accidents

• Phineas Gage– 3.5 foot rod shot through his skull– Survived but extreme personality change– Shows that certain parts of the brain control

certain aspects of our personality

Studying The Brain

–Computerized axial tomography (CAT Scan)• X-rays beam around the head (3D view)• Pinpoints injuries and brain deterioration

Studying The Brain

– Position Emission Topography (PET Scan)• Can see which areas

of the brain are activated when performing tasks• A radioactive solution

is injected into the body• Shows activity vs

snapshot

Studying The Brain

– Magnetic Resonance Imaging (MRI)• Can see structures in detail, hard to see areas• Magnetic fields and radio waves • More powerful than CAT scan, “slice images”

Studying The Brain

• Electroencephalograph (EEG)– Measures electrical activity of brain using small

electrodes pasted to you scalp– The rhythmical patterns produced are “brain

waves”

Brain Lobes

• Frontal Lobe (behind forehead)– Executive Center – Higher Mental Processes• Planning, Social Skills, Emotional Control, Problem

Solving & Abstract Thinking

– Motor Skills - Involved in the coordination of movement