PowerPoint® Presentation by Jim Foley

© 2013 Worth Publishers

Chapter 2The Biology

of Mind

Surveying the Chapter: OverviewWhat We Have in Mind

Building blocks of the mind: neurons and how they communicate (neurotransmitters)

Systems that build the mind: functions of the parts of the nervous system

Supporting player: the slower-communicating endocrine system (hormones)

Star of the show: the brain and its structures

Searching for the biology of “self”

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Is our identity in the heart? In the brain? In the whole body?

Searching for the self by studying the bodyPhrenology

Phrenology yielded one big idea--that the brain might have different areas that do different things (localization of function).

Phrenology (developed by Franz Gall in

the early 1800’s):

the study of bumps on the skull and their relationship to mental abilities and character traits

Biological psychology includes neuroscience, behavior genetics, neuropsychology, and evolutionary psychology.

All of these subspecialties explore different aspects of: how the nature of mind and behavior is rooted in our biological heritage.

Our study of the biology of the mind begins with the “atoms” of the mind: neurons.

Today’s search for the biology of the self: biological psychology

Neurons and Neuronal Communication:The Structure of a Neuron

There are billions of neurons (nerve cells) throughout the body.

Action potential:a neural impulse that travels down an

axon like a waveJust as “the wave” can flow to the right in a stadium even though the people only move up and down, a wave moves down an axon although it is only made up of ion exchanges moving in and out.

The neuron receives

signals from other

neurons; some are

telling it to fire and some are telling it not to fire.

The neuron receives

signals from other

neurons; some are

telling it to fire and some are telling it not to fire.

When the threshold is reached, the action potential starts moving.

Like a gun, it either fires or it doesn’t; more stimulation does nothing.

This is known as the “all-or-none” response.

When the threshold is reached, the action potential starts moving.

Like a gun, it either fires or it doesn’t; more stimulation does nothing.

This is known as the “all-or-none” response.

The action potential

travels down the axon

from the cell body to the

terminal branches.

The action potential

travels down the axon

from the cell body to the

terminal branches.

The signal is transmitted to another

cell. However,

the message must find a

way to cross a gap

between cells. This gap is also called the synapse.

The signal is transmitted to another

cell. However,

the message must find a

way to cross a gap

between cells. This gap is also called the synapse.

How neurons communicate(with each other):

When does the cell send the action potential?...

when it reaches a threshold

The threshold is reached when excitatory (“Fire!”) signals outweigh the inhibitory (“Don’t fire!”) signals by a certain amount.

The synapse is also known as the “synaptic junction” or “synaptic gap.”

The SynapseThe synapse is a junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron.

NeurotransmittersNeurotransmitters are chemicals used to send a signal across the synaptic gap.

Reuptake: Recycling Neurotransmitters [NTs]

Reuptake: After the neurotransmitters stimulate the receptors on the receiving neuron, the chemicals are taken back up into the sending neuron to be used again.

Seeing all the Steps TogetherNeural Communication:

Some Neurotransmitters and Their FunctionsNeurotransmitter Function Problems Caused by Imbalances

Roles of Different Neurotransmitters

Serotonin Affects mood, hunger, sleep, and arousal

Undersupply linked to depression; some antidepressant drugs raise serotonin levels

Dopamine Influences movement, learning, attention, and emotion

Oversupply linked to schizophrenia; undersupply linked to tremors and decreased mobility in Parkinson’s disease and ADHD

Acetylcholine (ACh)

Enables muscle action, learning, and memory

ACh-producing neurons deteriorate as Alzheimer’s disease progresses

Norepinephrine Helps control alertness and arousal

Undersupply can depress mood and cause ADHD-like attention problems

GABA (gamma-aminobutyric acid

A major inhibitory neurotransmitter

Undersupply linked to seizures, tremors, and insomnia

Glutamate A major excitatory neurotransmitter; involved in memory

Oversupply can overstimulate the brain, producing migraines or seizures; this is why some people avoid MSG (monosodium glutamate) in food

Serotonin pathways

Networks of neurons that communicate with serotonin help regulate mood.

Networks of neurons that communicate with dopamine are involved in focusing attention and controlling movement.

Dopamine pathways

Hearing the messageHow Neurotransmitters Activate ReceptorsWhen the key fits, the site is opened.

Keys that almost fit:Agonist and Antagonist Molecules

An antagonist molecule fills the lock so that the neurotransmitter cannot get in and activate the receptor site.

An agonist molecule fills the receptor site and activates it, acting like the neurotransmitter.

The Inner and Outer Parts of the Nervous System

The central nervous system [CNS] consists of the brain and spinal cord.

The CNS makes decisions for the body.

The peripheral nervous system [PNS] consists of ‘the rest’ of the nervous system.

The PNS gathers and sends information to and from the rest of the body.

Types of NeuronsSensory

neurons carry messages IN

from the body’s tissues and sensory receptors to the CNS for processing.

Motor neurons carry

instructions OUT from the CNS out to the body’s tissues. Interneurons (in

the brain and spinal cord)

process information between the

sensory input and motor output.

The “Nerves” are not the same as neurons.

Nerves consist of neural “cables” containing many axons.

Nerves are part of the peripheral nervous system and connect muscles, glands, and sense organs to the central nervous system.

More Parts of the Nervous System

The Peripheral Nervous System

The Autonomic

Nervous System:

The sympathetic NS arouses

(fight-or-flight)

The parasympathetic

NS calms(rest and digest)

The Central Nervous System

The brain is a web of neural networks.

The spinal cord is full of interneurons that sometimes have a “mind of their own.”

Neural Networks

These complex webs of interconnected neurons form with experience.Remember: “Neurons that fire together, wire together.”

Interneurons in the SpineYour spine’s interneurons trigger your hand to pull away from a fire before you can say OUCH!

This is an example of a reflex action.

The Endocrine System

The endocrine system refers to a set of glands that produce chemical messengers called hormones.

The Body’s “Slow but Sure” Endocrine Message System The endocrine system

sends molecules as messages, just like the nervous system, but it sends them through the bloodstream instead of across synapses.

These molecules, called hormones, are produced in various glands around the body.

The messages go to the brain and other tissues.

1. The sympathetic “fight or flight” nervous system responds to stress by sending a message to adrenal glands to release the hormones listed above.

2. Effect: increased heart rate, blood pressure, and blood sugar. These provide ENERGY for the fight or flight!

Adrenal Glandsproduce hormones such as adrenaline/epinephrine, noradrenaline/norepinephrine, and cortisol.

Pancreas

Adrenal Glands

The Pituitary Gland The pituitary gland is the

“master gland” of the endocrine system.

It is controlled through the nervous system by the nearby brain area--the hypothalamus.

The pituitary gland produces hormones that regulate other glands such as the thyroid.

It also produces growth hormone (especially during sleep) and oxytocin, the “bonding” hormone.

Pituitary gland

The BrainWhat we’ll discuss:how we learn about the brainthe life-sustaining inner parts of the brain: the brainstem and limbic systemthe outer, wrinkled “bark”: the cortexleft, right, and split brainsQuestions about parts of the brain:Do you think that the brain is the sum of its parts, or is the brain actually about the way they are connected? What do you think might happen if a particular area of the brain was stimulated? What do you think might happen if a particular area of the brain was damaged or not working well?

Is it possible to ‘understand’ the brain?

“If the human brain were so simple that we could understand it, we would be so simple that

we couldn’t.”–Emerson M. Pugh

…but we can try.

Investigating the Brain and Mind:How did we move beyond phrenology?How did we get inside the skull and under the “bumps”?by finding what happens when part of the brain is damaged or otherwise unable to work properlyby looking at the structure and activity of the brain: CAT, MRI, fMRI, and PET scans

Strategies for finding out what is different about the mind when part of the brain isn’t working normally:case studies of accidents (e.g. Phineas Gage)case studies of split-brain patients (corpus callosum cut to stop seizures)lesioning brain parts in animals to find out what happenschemically numbing, magnetically deactivating, or electrically stimulating parts of the brain

Studying cases of brain damage

When a stroke or injury damages part of the brain, we have a chance to see the impact on the mind.

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Intentional brain damage:

performed on animals has yielded some

insights, especially about less complex brain structures

no longer necessary, as we now can chemically or magnetically deactivate brain areas to get similar information

Lesions (surgical destruction of brain tissue)

Split-Brain Patients

“Split” = surgery in which the connection between the brain hemispheres is cut in order to end severe full-brain seizures

Study of split-brain patients has yielded insights discussed at the end of the chapter

We can stimulate parts of the brain to see what happens

Parts of the brain, and even neurons, can be stimulated electrically, chemically, or magnetically.

This can result in behaviors such as giggling, head turning, or simulated vivid recall.

Researchers can see which neurons or neural networks fire in conjunction with certain mental experiences, and even specific concepts.

Monitoring activity in the brainTools to read electrical, metabolic, and magnetic

activity in the brain:

EEG: electroencephalogram

MRI: magnetic resonance imaging fMRI: functional MRI

PET: positron emission tomography

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An EEG (electroencephalogram) is a recording of the electrical waves sweeping across the brain’s surface.An EEG is useful in studying seizures and sleep.

EEG: electroencephalogram

The PET scan allows us to see what part of the brain is active by tracing where a radioactive form of glucose goes while the brain performs a given task.

PET: positron emission tomography

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MRI (magnetic resonance imaging) makes images from signals produced by brain tissue after magnets align the spin of atoms.The arrows below show ventricular enlargement in a schizophrenic patient (right).

MRI: magnetic resonance imaging

Functional MRI reveals brain activity and function rather than structures.Functional MRI compares successive MRI images taken a split second apart, and shows changes in the level of oxygen in bloodflow in the brain.

fMRI: functional MRI

Areas of the brain and their functions

The Brain: Less Complex Brain Structures

Our tour of the brain begins with parts of the human brain found also in simpler animals; these parts generally deal with less complex functions:

Brainstem (Pons and Medulla)

Thalamus

Reticular Formation

Cerebellum

Limbic System

The Brainstem: Pons and Medulla

The Base of the Brainstem: The Medulla

The medulla controls the most basic functions such as heartbeat and breathing.

Someone with total brain damage above the medulla could still breathe independently, but someone with damage in this area could not.

The Brainstem:

The Pons

The pons helps coordinate automatic and unconscious movements.

The Thalamus (“Inner Chamber”)

The thalamus is the “sensory switchboard” or “router.”

All sensory messages, except smell, are routed through the thalamus on the way to the cortex (higher, outer brain).

The thalamus also sends messages from the cortex to the medulla and cerebellum.

Reticular (“Netlike”) Formation

The reticular formation is a nerve network in the brainstem.

It enables alertness, (arousal) from coma to wide awake (as demonstrated in the cat experiments).

It also filters incoming sensory information.

The cerebellum helps coordinate voluntary movement such as playing a sport.

Cerebellum (“little brain”)

The cerebellum has many other functions, including enabling nonverbal learning and memory.

emotions such as fear and aggression.

basic drives such as hunger and sex.

the formation of episodic memories.

The hippocampus (“seahorse”) processes conscious, episodic

memories. works with the amygdala to

form emotionally charged memories.

The Amygdala (“almond”) consists of two lima bean-

sized neural clusters. helps process emotions,

especially fear and aggression.

The Limbic (“Border”) System The limbic system coordinates:

The Amygdala

Electrical stimulation of a cat’s amygdala provokes aggressive reactions.

If you move the electrode very slightly and cage the cat with a mouse, the cat will cower in terror.

lies below (“hypo”) the thalamus.

regulates body temperature and ensures adequate food and water intake (homeostasis), and is involved in sex drive.

directs the endocrine system via messages to the pituitary gland.

The Hypothalamus:Thalamus

Riddle: Why did the rat cross the grid? Why did the rat want to get to the other side?

The Hypothalamus as a Reward Center

Pushing the pedal that stimulated the electrode placed in the hypothalamus was much more rewarding than food pellets.

Review of Brain Structures

The Cerebral Cortex The lobes consist of:

300 billion synaptic connections

The brain has left and right hemispheres

outer grey “bark” structure that is wrinkled in order to create more surface area for 20+ billion neurons.

inner white stuff—axons linking parts of the brain. 180+ billion glial cells, which feed and protect neurons

and assist neural transmission.

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The Lobes of the Cerebral Cortex: Preview

Frontal Lobes

Parietal Lobes

Occipital Lobes

Temporal Lobes

involved in speaking and muscle movements and in making plans and judgments

include the sensory cortex

include the visual areas; they receive visual information from the opposite visual field

include the auditory processing areas

Input: Sensory cortex (Left hemisphere section receives input from the body’s right side)

Output: Motor cortex (Left hemisphere section controls the body’s right side)

Functions of the Brain: The Motor and Sensory Strips

Axons receiving motor signals FROM the cortex

Axons sending sensory

information TO the cortex

Using our knowledge of functions: Brain-computer interfaces and neural prosthetics

Here, a robotic arm is operated through controls embedded in the motor strip of the cortex.

We may soon be able to use computers to translate neural inputs into more commands and words than simply grabbing food.

Sensory Functions of the Cortex

The sensory strip deals with information from touch stimuli.

The occipital lobe deals with visual information.

Auditory information is sent to the temporal lobe.

The Visual Cortex

This fMRI scan shows increased activity in the visual cortex when a person looks at a photograph.

Association function of the cortexMore complex animals have more cortical space devoted to integrating/associating information

Association Areas:Frontal Lobes

The frontal lobes are active in “executive functions” such as judgment, planning, and inhibition of impulses.

The frontal lobes are also active in the use of working memory and the processing of new memories.

Phineas Gage (1823-1860)Case study: In a work accident, a metal rod shot up through Phineas Gage’s skull, destroying his eye and part of his frontal lobes. After healing, he was able to function in many ways, but his personality changed; he was rude, odd, irritable, and unpredictable.

Possible explanation: Damage to the frontal lobes could result in loss of the ability to suppress impulses and to modulate emotions.

Parietal Lobe Association AreasThis part of the brain has many functions in the association areas behind the sensory strip:managing input from multiple sensesperforming spatial and mathematical reasoningmonitoring the sensation of movement

Temporal Lobe Association Areas

Some abilities managed by association areas in this “by the temples” lobe:recognizing specific facesmanaging sensory input related to sound, which helps the understanding of spoken words

Whole-brain Association Activity

Whole-brain association activity involves complex activities which require communication among association areas across the brain such as:memorylanguageattentionmeditation and spiritualityconsciousness

Specialization and Integration Five steps in reading a word aloud:

This 6-year-old had a hemispherectomy to end life-threatening seizures; her remaining hemisphere compensated for the damage.

Plasticity: The Brain is Flexible

If the brain is damaged, especially in the general association areas of the cortex: the brain does not repair damaged neurons, BUT it can restore some functionsit can form new connections, reassign existing networks, and insert new neurons, some grown from stem cells

Our Two Hemispheres

Lateralization (“going to one side”)The two hemispheres serve some different functions.How do we know about these differences?Brain damage studies revealed many functions of the left hemisphere.Brain scans and split brain studies show more about the functions of the two hemispheres, and how they coordinate with each other.

Thoughts and logicDetails such as “trees”Language: words and definitionsLinear and literal CalculationPieces and details

Feelings and intuitionBig picture such as “forest”Language: tone, inflection, contextInferences and associationsPerceptionWholes, including the self

The intact but lateralized brainRight-Left Hemisphere Differences

Left Hemisphere Right Hemisphere

Brain Studies

Researchers have studied the impact of this surgery on patients’ functioning.

Split-

To end severe whole-brain seizures, some people have had surgery to cut the corpus callosum, a band of axons connecting the hemispheres.

Separating the Hemispheres:Factors to Keep in Mind

Each hemisphere controls the opposite side of the body AND is aware of the visual field on that opposite side.

Without the corpus callosum, the halves of the body and the halves of the visual field do not work together.

Only the left half of the brain has enough verbal ability to express its thoughts out loud.

Split visual field

Each hemisphere does not perceive what each EYE sees. Instead, it perceives the half of the view in front of you that goes with the half of the body that is controlled by that hemisphere.

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Divided Awareness in the Split Brain

Try to explain the following result:

The divided brain in action

Talent: people are able to follow two instructions and draw two different shapes simultaneously

Drawback: people can be frustrated that the right and left sides do different things

The Future of Brain ResearchCan these questions be answered?

Is every part of the mind’s functioning going to be found someday on some brain scan?

If so, have we found the mind, or is that still something separate from the brain?