The Structures of the Brain

The brain is truly a remarkable organ; in fact, it is the single most complex object in the known universe. It consists of nerve cells (neurons) as well as support cells (astrocytes, oligodendrocytes, and microglia), and has the consistency in life of solidified jello. It lies suspended in fluid (called cerebrospinal fluid, or CSF for short) and is surrounded by several membranes (called the meninges) all of which are enclosed within a very solid and protective bony chamber, the skull.

To Begin

The Brainstem is the oldest part of the brain, beginning where the spinal cord swells and

enters the skull. It is responsible for

automatic survival functions.

The Old Brain - Brainstem

Brain Stem – MedullaThe Medulla is the base of the brainstem It controls autonomic functions and relays nerve signals between the brain and spinal cord.respirationblood pressure heart rate reflex arcs vomiting

Brain Stem – Pons and Reticular Formation

Pons - A nerve network involved in motor control and sensory analysis...

Information from the ear first enters the brain in the Pons.Certain parts are important for the level of consciousness and for sleep.

The Reticular Formation controls:Attention Cardiac Reflexes Motor Functions Regulates Awareness Relays Nerve Signals to the Cerebral Cortex Sleep ADHD Association

Brain Stem - ThalamusThe is the brain’s sensory switchboard, located on top of the brainstem. It directs messages to the

sensory areas in the cortex and transmits

replies to the cerebellum and medulla.- Not Smell

- The “little brain” attached to the rear of the brainstem. It helps coordinate voluntary movements and balance.

- Controls leg and arm movements- Damage causes awkward movement to the inability to

stand

Cerebellum

Large clusters of neurons that work with the cerebellum and cortex to control voluntary movements.

Determines course of action in movementHow you ride a bike, swim, or jump off a

bridge.Damage can lead to unwanted movement

(Parkinson's)

Basal Ganglia

The Limbic SystemProcesses information about

internal stateBlood pressureHeart rate Respiration

Smell, motivation, memoryEmotional centerFour focal areas:

ThalamusHypothalamusAmygdalaHippocampus

Limbic System - Amygdala

The Amygdala consists of two almond-shaped neural clusters linked Excitement,

Arousal, Fear.-Discriminates objects for

organisms survival-* Can I eat it?

-* Will it eat me?-* Can I have sex with it?

Determines what parts of information should be stored into durable, lasting, neural traces in the cortex

Helps us recall information by activating the parts of the brain we used for that activity

Extensive damage leads to an inability to retain long term memories

Limbic System - Hippocampus

HypothalamusThe Hypothalamus lies below

(hypo) the thalamus. -Directs several maintenance

activities like eating, drinking, body temperature,

and control of emotions. - It helps govern the

endocrine system via the pituitary gland.

- Monitors reward activities-Thirst, Hunger, Sex Motivation-Emotion, Stress, and Reward

Rats cross an electrified grid for

self-stimulation when electrodes are placed in their reward center

(hypothalamus, top picture). When the

limbic system is manipulated, a rat

will navigate fields or climb up a tree

(bottom picture).

Reward Center

Cerebral CortexThe Lobes

FrontalParietalOccipitalTemporal

FPOT

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The Frontal Lobe

Executive functioning

Motor cortexDifferent areas

control different parts of body

Prefrontal cortexThinking, planning,

languagePhineas GageBroca’s area

(language)

The Parietal Lobe

Somatosensory cortexPerception

Processing others’ actions

Numbers

The Temporal Lobe

Hearing, understanding language, storing memories

Auditory cortexHearing

Wernicke’s area (also part of parietal)Understanding

speech

The Occipital Lobe

Visual cortexSeeing

Humans especially dependent on vision

Functions of the CortexThe Motor Cortex is the area at the rear of

the frontal lobes that control voluntary movements. The Sensory Cortex (parietal

cortex) receives information from skin surface and sense organs.

More intelligent animals have increased “uncommitted” or association areas of the cortex. These integrate

sensory and motor information. (75% of cerebral cortex)

Association Areas

Speech Productio

n

Language Comprehensi

on

LanguageAphasia is an impairment of language,

usually caused by left hemisphere damage either to Broca’s area (impaired speaking)

or to Wernicke’s area (impaired understanding).

Specialization & IntegrationBrain activity when hearing, seeing, and

speaking words

Complex cable of nerves that connects brain to rest of the body

The spinal cord controls some protective reflex movements without any input from the brain

Carries motor impulses from the brain to internal organs and muscles

Carries sensory information from extremities and internal organs to the brain

400,000 people a year in US either partial or complete paralysis.

The Spinal Cord

Unit 2

Brain Hemispheres Study

Hemispheric Specialization

Corpus Callosum (Video)Fibers that connect the two hemispheres

Allow close communication between left and right hemisphere

Each hemisphere appears to specialize in certain function

Neural PlasticityThe brain can be changed, both structurally

and chemically, by experienceRat studies show that an “enriched”

environment leads to larger neurons with more connectionsHas also been shown in humans

Recent research has uncovered evidence of neurogenesis, or the production of new brain cells, in human brains

Neural PlasticityCollateral Sprouting – Process where healthy neurons will grow new branches when near damaged cells.

Substitution of Function – A damaged region of brain is taken over by another area

Neurogenesis – New neurons are generated within the brain

Fun with your Hemispheres

Rotate your dominant hand in one direction while at the same time rotating the opposite foot in the other direction.No problem since controlled by two hemispheres

Now, rotate your dominant hand in one direction while at the same time rotating the foot on the same side in the other direction.

Our Divided Brain

Our brain is divided into two hemispheres.

The left hemisphere

processes reading, writing, speaking, mathematics, and comprehension

skills. In the 1960s, it was termed as the

dominant brain.

Which face is happier?

Which face was happier?

Right Hemisphere

Hemispheric SpecializationPeople with intact brains also show left-right hemispheric differences in mental abilities.

A number of brain scan studies show normal individuals engage their right brain when

completing a perceptual task and their left brain when carrying out a linguistic task.

Splitting the BrainA procedure in which the two hemispheres of

the brain are isolated by cutting the connecting fibers (mainly those of the corpus

callosum) between them.Corpus Callosum

Split Brain PatientsWith the corpus

callosum severed, objects (apple)

presented in the right visual field can be named.

Objects (pencil) in the left visual field

cannot.

Brain Organization & Handedness

Is handedness inherited? Yes. Archival and historic studies, as well as modern medical

studies, show that the right hand is preferred. This suggests genes and/or prenatal factors influence handedness.

Is it Alright to be Left Handed?The percentage of left-handed individuals

decreases sharply in samples of older people (Coren, 1993).

Is it Alright to be Left Handed?

Being left handed is difficult in a right-handed world.