Brain Function

Copyright 2010:PEER.tamu.edu

• How the brain operates.

• What nerve cells (neurons) are and what they do.

• What the different parts of the brain do.

• How the brain creates “three minds”.

• Healthy Brain

We Will Discuss:

How The Brain Operates

Brains are designed as a control system for the body. As with any control system, it has to have sensors to know what is going on and has to have ways of evaluating information making decisions and then issuing commands.

Class Discussion:

What are some things you think your brain tells you to do?

The Brain is an InformationProcessor:

(subconscious processing)

Internal vs. External Stimulus

What Is a Stimulus???1. 2. 3.

4.

5.

6.

Neuron FunctionNerve Cells are Called Neurons

When neurons are active, as they almostalways are even when you sleep, they dotwo things: 

– generate electrical pulses – release chemical secretions

cell body and nucleus

axon

dendrites (terminal)dendrites

(input)

Direction of impulse and information flow

How NEURONS Take in Information and Process it!

Neuron Signaling is the term used to describe the process of neurons passing information back and forth to one another.

Neurons have the ability to pass intracellular information (within the cell) and intercellular information (from one cell to another cell).

Speedy Processing Continued:

• Neurons pass information from cell to cell (intercellular) at synapses through neurotransmission.– communication between neurons is accomplished

by the movement of chemicals or electrical signals across a synapse.

– A synapse occurs where a axon of one neuron passes information to an dendrite of another neuron.

How Neurons Have Evolved for Speedy Processing:

• Neurons communicate within the cell (intracellular) through conduction.– Conduction is when an electrical

signal generated near the cell body of a neuron moves along the axon to the axon terminals.

– Ions are the electrically charged particles moving within the neuron.

Electrical signals are used to represent, distribute and process

information.

Above: This picture shows 3 different neurons all transmitting information. Yellow axon to blue dendrite, blue axon to pink dendrite is one way to look at it.

An axon to dendrite passage of information represents the passing of chemical signals.

Chemical signals help form memories.

Chemical Signals:

Neurons Excrete Chemicals• Some neurons excrete chemicals called hormones into the blood stream

• Most neurons secrete chemicals directly on each other or on muscle cell targets. – The chemicals acts as messengers

(neurotransmitters) to convey information from one neuron to others.

• Chemicals released vary with different parts of the brain.

• Over 100 chemical secretions have been found in nerve tissue

Brain Chemicals

• Neurotransmitters– excite

– inhibit

– modulate (create a bias for being excited or inhibited)

• Hormones– Excite neurons (make them fire impulses)

– Inhibit neurons (reduce impulse firing)

– Change the sensitivity of neurons (make them more or less responsive to other chemicals or electrical input)

Neurochemical TransmissionPackets of chemicals are released at the axon terminal.

Drugs that affect the brain typically act on one or more of these processes.

Neurochemical Transmission

Receptors

Nervous System vs. Electricity How It is Different

• Current carried by ions, not electrons.• Current flows as pulses, not continuous. • Current is continuous in the junctions between

neurons.• Can travel in many different directions at once.• Chemical and electrical transmitters specifies

different kinds of information being passed.• Not rigid like solid electrical curcuits.

Lets Discuss:

Can you think of some advantages of a processing and communicating system (the brain) operating this way?

How does the brain differ from how computers work? That is, how is the transfer of communication different between elements in a computer and

neurons in the brain?

Brains Operate on the Nerve-impulse Representation of the World, Not the World Itself

Think about that!

Function of Different Parts of the Brain

Spinal Cord

There is a central "H" zone containing millions of neurons

• It is surrounded by white substance, which is many nerve fibers (axons).

• Some fiber bundles go to the brain, while others are bringing information to the spinal cord from the brain. 

Spinal Cord• Two Way Wiring: Like electrical wiring in your car or your house,

neurons in the spinal cord communicate with the brain by insulated cables.

• Example: pain information excites neurons to activate muscles that flex the hip and knee of the leg on the same side as the stimulus.

Pain information is carried in fiber bundles in the lateral part of the cord. The pathway has relays in the brainstem and thalamus before reaching the cortex. Common pain killer drugs act at different levels of the pathway.

BrainstemNote that human brainstem is about the diameter of a pencil.

Functions: Breathing,Heart Rate, Swallowing,Reflexes to seeing and hearing (startle response),Controls sweating, blood pressure, digestion, temperature (autonomic nervous system),Affects level of alertnessAbility to sleep,Sense of balance (vestibular function).deep in the brain – leads to the spinal

cord

Cerebrum The biggest part of the brain is the cerebrum.

The cerebrum makes up 85% of the brain's weight, and it's easy to see why.

The cerebrum is the thinking part of the brain and it controls your voluntary muscles — the ones that move when you want them to.

So you can't dance — or kick a soccer ball — without your cerebrum.

Your memory lives in the cerebrum — both short-term memory (what you ate for dinner last night) and long-term memory (the name of that roller-coaster you rode on two summers ago).

When you're thinking hard, you're using your cerebrum.

You need it to solve math problems, figure out a video game, and draw a picture.

Cerebrum Continued:The cerebrum also helps you reason, like when you figure out that you'd better do your homework now because your mom is taking you to a movie later.

The cerebrum has two halves, with one on either side of the head.

The left half is said to be more analytical, helping you with math, logic, and speech.

Scientists do know for sure that the right half of the cerebrum controls the left side of your body, and the left half controls the right side

Some scientists think that the right half helps you think about abstract things like music, colors, and shapes.

Frontal Lobe:

Functions: How we know what we are doing within our environment (consciousness)

How we initiate activity in response to our environment

Judgments we make about what occurs in our daily activities

Controls our emotional response

Controls our speaking language

Memory for habits and motor activities

Most anterior, right under the forehead

Parietal Lobe:Functions:

Location for visual attention and touch perception.

Goal-directed, voluntary movements.

Manipulation of objects.

Integration of different senses that allows for understanding a single concept.

Near the back and top of the head

Occipital Lobe:

Functions: Vision

Temporal Lobe:

Functions:

Hearing ability

Memory acquisition

Some visual perceptions

Categorization of objects

Side of head above ears

Most posterior, at the back of the head

Cerebellum

Gold colored area Gold colored area located at the base of the skull.

Functions: Coordination of voluntary movementBalance and equilibriumSome memory for reflex motor acts

The Brain Makes Us Aware

• Humans have detector cells for:

– Light waves (eyes) – Sound waves (ears) – Chemicals that we smell (sensors in the nose) – Chemicals that we taste (tongue sensors) – Physical forces (touch, pressure, cold, heat) (skin sensors) – Muscle tone and limb position (sensors in muscles)

Humans can be consciously aware of many of these stimuli. We not only know this information, we are

aware that we are aware of it.

The “Reptilian” Brain

“Reptilian” Brain Functions

• Mostly controlled by brainstem structures found in all animals (even fish)

• Interaction with spinal reflexes

• Control over neurohormone systems (pituitary gland)

• Control over automated movements

• Activation of the rest of brain in response to stimulation

The Brain Makes Us Feel Emotions

• Some of the same structures used in emotions are also involved in memory formation.

The Limbic System• Controls emotions• Controls formation of certain kinds of long-term

memories• The limbic system is a complex set of structures that lies

on both sides of the thalamus, just under the cerebrum.  It includes the hypothalamus, the hippocampus, the amygdala, and several other nearby areas. 

In primitive mammal brain, most of the brain is the limbic system.

OB = olfactory bulb, HIP = hippocampus, AC = anterior commissure (fiber tract connecting olfactory structures), V – ventricles (cavity), NC = neocortex, but most of this is really limbic cortex.

Memory• Memories are stored widely in the brain.

• The medial temporal lobe and nearby structures, are responsible for converting temporary memories into more permanent form.

Ventral view of brain. Temporal lobe is outlined in white. * indicates the visible part of hippocampus.

Hippocampus Consolidates Memory

• Located in area beneath the ears (medial temporal lobe)

• Consolidation: temporary memories into more permanent form.

Memory “Consolidation”

• This conversion has certain requirements:– The brain needs to pay attention so that the

information actually registers in the first place – Motivation to remember helps – Time must elapse (seconds to minutes) – Distractions and other stimuli should be kept to a

minimum, because they will otherwise interfere with the conversion process

Class Discussion: how do these ideas apply to learning effectively in school?

Cool Link Break!The following link is helpful and useful for kids to see and hear about the brain:

http://kidshealth.org/misc/movie/bodybasics/bodybasics_brain.html

What Sets Us Apart?The cerebral cortex or neocortex is what makes us human.

It is this outer layer that gives us the ability to think, to make choices, and to reflect on our emotions rather than unthinkingly act on them.

The human cerebral cortex is 2–4 mm (0.08–0.16 inches) thick.

The cerebral cortex is the layer of the brain often referred to as gray matter.

The cortex (thin layer of tissue) is gray because nerves in this area lack the insulation that makes most other parts of the brain appear to be white.

The cortex covers the outer portion the cerebrum and cerebellum.

“Wiring Diagramof Cerebral CortexThis is what makes us different

• Six layers of cells surrounding the rest of brain. – Other mammals have such

cells, but not as many layers and not so many.

– Cells organized vertically, as columns

Area A and B, outer layer 6: mostly all fibers. Circles labeled L are cell bodies in different layers. “Thal” and “Sub” refer the cells in the thalamus and subthalamus that send inputs to the columns.

Circuit diagram of one column… connects with adjacent columns.

Humans Are Unique

• What motivates you? – The desire for pleasurable sensations and

experiences – The desire to avoid unpleasant sensations and

experiences • Laughter is one clear difference humans have from

animals  

• Likewise, emotion-based crying seems unique to humans.

The Brain Is the Organ of Personality

• Teenage brains are rapidly changing, sculpted by experience

• Social environment and thoughts will affect that sculpting.

• The most profound changes occur in the front of the brain, the part that is crucial for advanced functions such as critical thinking, self-control, and judgment.

• The frontal cortex does not mature until about age 25.

Importance of Technology:The Oscilloscope

The electricity in a nerve involves such a small amount of current that it has to be made bigger and displayed by a TV-like instrument called

an oscilloscope.

Voltage changes deflect the beam

moving across the screen

Brain Waves• Currents in the part of the brain nearest to the scalp are large

enough to be detected with electrodes • This electrical activity is small (on the order of 10 to 50

millionths of a volt).

Brain Creates MindActually Three Minds

• Unconscious: spinal and brainstem reflexes, hormone controls

• Subconscious: emotions, well-established memories

• Conscious: newly forming memories, self awareness

Your brain has a mind of its own

Brain affects mind. Mind affects brain. 

Brain affects behavior and hormone release. 

Where Does Consciousness Come From? 

It comes from the interaction between:– the cerebral cortex (outer part of the brain) – a cluster of cells in the core of the brainstem

• Lower animals have many fewer cells in their cortex than us.

• Therefore, they cannot operate at the same high level of consciousness as we do.

Improving Your Mind

• You can train your brain to have certain attitudes, beliefs, capabilities.

• You can abuse your brain by feeding it bad ideas, unhealthy ideas, or drugs that affect the mind.

• Feeding junk ideas, information, and feelings to your brain can affect your brain and behavior permanently.

Improving Your Mind, cont.

• Brains affect behavior.

• But behavior (and thoughts that control behavior) affect the brain.

Let’s Discuss:

Can we blame our bad brains for our bad behavior and thoughts?

Or is that just an excuse for our failure to make better behavior choices?

Be Good to Your BrainWhat can you do for your brain?

• Eat healthy foods.

– They contain potassium and calcium, two minerals that are important for the nervous system.

• Get a lot of playtime (exercise).

• Wear a helmet when you ride your bike or play other sports that require head protection.

• Don't drink alcohol, take drugs, or use tobacco.

• Use your brain by doing challenging activities\

– such as puzzles, reading, playing music, making art, or anything else that gives your brain a workout

Do you want your brain to look like this?

or

This?

Brain Function: Conclusion• Remember, mistreating your brain can permanently

alter the way you learn, feel rewarded, and store memories.

• Keep your brain healthy through proper nutrition to support neuron development and by training yourself to have positive attitudes, beliefs, capabilities!