Biological Psychology Biological Psychology

Neural and Hormonal Systems – Module 3Neural and Hormonal Systems – Module 3

How the Brain Governs Behavior – Module 4How the Brain Governs Behavior – Module 4 NeurotransmittersNeurotransmitters – Module 3 – Module 3

General Psych 1

February 8-10, 2005Classes #5-6

““So why do we have to study So why do we have to study biology in a psych class?”biology in a psych class?”

Let me use Phineas Gage to help answer this question…

““He was no longer Gage…”He was no longer Gage…”

Several different angles of where the rod passed through his skull

There is a Phineas Gage display in the Warren There is a Phineas Gage display in the Warren Medical Museum at Harvard UniversityMedical Museum at Harvard University

This is what went through his brain (see below)…

Biological Roots of BehaviorBiological Roots of Behavior

Franz Gall (1758-1828) – Austrian physicist who invented phrenology

He felt that bumps on the skull could reveal our mental abilities and character traits.

Introduced as being scientific but its use was exploited by quacks on gullible individuals

Biological Roots of BehaviorBiological Roots of Behavior

Became similar to that of astrology, palm-reading and tarot

Although, ill-fated theory was laughed at by scientific community of that day – it may have had some validity

Localization of brain functions somehow hit the mark

The Nervous SystemThe Nervous System

Electrochemical communication system that enables us to think, feel, and behave

Complex beyond comprehension Although, human brains are more complex

our nervous systems and those of animals operate in a similar fashion – advantage of this is experimentation

Major ComponentsMajor Components

Neurons: – Rapidly respond to signals and quickly

send signals of their ownGlial cells:

– Help neurons to communicate, keep chemical environment stable, secrete chemicals to help restore damage, and respond to signals from neurons – enable neurons to function

AxonsAxons

Function: – Carries signals away from the cell body– Pass information along to other nuerons, or

to muscles or glandsType of Signal Carried:

– The action potential, an all-or-nothing electrochemical signal that shoots down the axon to vesicles at the tip of the axon, releasing neurotransmitters

SynapseSynapse

Very small gap between neurons For communication to occur between

cells, the signal must be transferred across this gap

Function: – Provides an area for the transfer of signals

between neurons, usually between axon and dendrite

DendriteDendrite

Function: – Detects and carries signals to the cell body

Type of Signal Carried: – The postsynaptic potential, which is an

electrochemical signal moving toward the cell body

ReceptorsReceptors

Function: – Proteins on the cell membrane that receive

chemical signalsType of Signal Carried:

– Recognizes certain neurotransmitters, thus allowing it to begin a postsynaptic potential in the dendrite

Okay, so how do neurons actually Okay, so how do neurons actually transmit information?transmit information? A neuron:

– Receives signals form other neurons through its branching dendrites and cell body

– Then combines these signals in the cell body

– And then transmits an electrical impulse down its axon

Transmitting information…Transmitting information…

The impulse is called the action potential which is a brief electrical charge that travels down the axon like a line of dominoes falling, each one tripping up the next

This is real electricity as a handful of neurons produce enough power to light up a flashlight

When electrical signals reach the end of the axon, they stimulate the release of chemical messengers – neurotransmitters

NeurotransmittersNeurotransmitters

Function: – A chemical released by one cell that binds

to the receptors on another cellType of Signal Carried:

– A chemical message telling the next cell to fire or not to fire its own action potential

The Nervous SystemThe Nervous System

Allows researchers to study simple animals such as squids and sea slugs to help us better understand the organization of our own brains

Divisions of the Nervous SystemDivisions of the Nervous System

Consists of two systems– Central Nervous System

• Brain and spinal cord– Peripheral Nervous System

• Which connects the CNS to the rest of the body

Organization of the Nervous SystemOrganization of the Nervous SystemOrganization of the Nervous SystemOrganization of the Nervous System

Peripheral Nervous SystemPeripheral Nervous System

Two components: – Somatic Nervous System

• Transmits sensory input to the CNS from the outside world and directs motor output

– Autonomic Nervous System• Controls glands and muscles of our

internal organs – “automatic pilot”

Autonomic Nervous SystemAutonomic Nervous System

Dual system:– Sympathetic Nervous System

• Arouses the body– Parasympathetic Nervous System

• Calms us down

NeuronsNeurons

Nerve cells (building blocks) – essentially identical to animals – Small samples of brain tissue from a

person and a monkey are basically indistinguishable

Endocrine System: Taking the slow laneEndocrine System: Taking the slow lane

Unlike the speedy nervous system which zips messages from eyes to brain to hand in a fraction of a second, endocrine messages use the slow lane

May take several seconds or more as bloodstream carries a hormone from an endocrine gland to its target tissue

Endocrine SystemEndocrine System

Hormones are chemical messengersInfluence all aspects of our lives –

growth, metabolism, reproduction, moods, etc.

Strives for homeostasis (balance) by responding to stress, exertion, internal thoughts, etc.

The BrainThe Brain

Studying the brain:– Clinical observations– Manipulating the brain

How does the brain govern How does the brain govern behavior?behavior?3 Principle layers of the brain:

(1) Brainstem

(2) Limbic System• Hippocampus• Amygdala• Hypothalamus

(3) Cerebral Cortex

Brainstem (or Hindbrain)Brainstem (or Hindbrain)

The brain’s innermost region…– Begins where the spinal cord enters the

skull and swells slightly forming the medulla

– Towards the rear of the brainstem is the cerebellum – this is linked to memory and its major function is muscular control

Limbic SystemLimbic System

Hippocampus – This structure plays a key role in allowing

us to store new information– Problems here may cause Alzheimer's –

these individuals have trouble processing declarative memories

– Milner (1968): the classic case of H.M.

Limbic SystemLimbic System

Amygdala– Emotional control center of the brain –

major influence on aggression and fear– Emotional memories as well– Alzheimer’s ???

Kluver and Bucy (1939) Demasio (1994)

Limbic SystemLimbic System

Hypothalamus– Major influence on hunger, thirst, body

temperature, and sexual behavior• Olds and Milner (1954)

Cerebral CortexCerebral Cortex

Makes us distinctively human – much higher developed than in animals– Motor Cortex – involved in the conscious initiation

of voluntary movements in specific parts of the body including hand, knee, foot and head

Fritsch and Hitzig (1870) Delgado (1969a) Delgado (1969b) Penfield (1975)

Cerebral CortexCerebral Cortex

Sensory Cortex – receives information from our senses– Visual cortex

• visual info– Auditory cortex

• auditory info– Somatosensory cortex

• info from skin Association cortex

– involved in complex cognitive tasks associating words with images

• Broca’s area (aphasia)• Wernicke’s area (aphasia)

NeurotransmittersNeurotransmitters

Neurotransmitters are chemicals made by neurons and used by them to transmit signals to the other neurons

A chemical message telling the next cell to fire or not to fire its own action potential

More than 200 in our body all with different functions

Lets briefly discuss some of the most important ones…

SerotoninSerotonin

Facilitates a relaxed, sleepy feeling Tryptophan which is an amino acid

found in dairy products and turkey is converted into serotonin in the body

So, insomnia sufferers may be smart to listen to grandmother’s suggestion to drink a warm glass of milk before going to bed

Some Illnesses Associated With SerotoninSome Illnesses Associated With Serotonin

Too low levels in depression and anxiety sufferers

Obesity may also be associated with low levels

Linked to aggression as well -- low levels in the brains of suicide victims

DopamineDopamine

High levels lead to pleasure

– Makes person feel happy and activeDopamine raises the body's temperature and

increases metabolic rateGives you euphoric feelings and allows you to

be activeDrug and alcohol abuse will block dopamine

receptors and therefore a person needs to take more to get the same effect

Illnesses Associated With DopamineIllnesses Associated With Dopamine

Parkinson’s Disease – too low levelsSchizophrenia – too high levelsTourette’s disorder – too high levelsHuntington’s disease – too high levels

NorepinephrineNorepinephrine

Plays a role in attention and arousalUsed by sympathetic nervous system to

prepare us for action

Illnesses Associated With NorepinephrineIllnesses Associated With Norepinephrine

Depression – chronic stress depletes this

neurotransmitter and can lead to depression

Note:– Aerobic Exercise is found to protect the

brain from this depletion – so go out and run a mile or two if your down in the dumps

EpinephrineEpinephrine

Involved in energy and glucose metabolism

Illnesses Associated With EpinephrineIllnesses Associated With Epinephrine

Depression – too low levels

AcetylcholineAcetylcholine

Involved in voluntary movement, learning, memory, and sleep

Helps parasympathetic nervous system to slow our heart rate

Illnesses Associated With AcetylcholineIllnesses Associated With Acetylcholine

Alzheimer’s disease – too low levelsNote:

– Unfortunately, drugs used to increase acetylcholine to help restore normal levels appear to have small effects on improving memory

GABAGABA

Inhibits excitation and anxietyAppears directly related to anxiety

reduction

Illnesses Associated With GABAIllnesses Associated With GABA

Anxiety disorders – too low levelsHuntington’s Disease – too low levels

– GABA systems aren’t working and this allows dopamine systems to run wild

– Huntington's disease is a hereditary disorder characterized by memory loss, abnormal movement and premature death• It affects 1 in 10,000 people, and children with an

affected parent have a 50 percent chance of developing the disease

Epilepsy – too low levels

GlutamateGlutamate

Main excitatory neurotransmitter in the brain

Very important in learning and memory

Illnesses Associated With GlutamateIllnesses Associated With Glutamate

Alzheimer’s disease – too low levels in hippocampus

Strokes – too high levels can cause neurons to die

ALS (Lou Gehrig’s Disease) – causes death in neurons in the spinal cord and brainstem

EndorphinsEndorphins

Involved in pain reduction and pleasure They enhance the release of dopamineThese natural opiates are released in

response to pain and vigorous exercise

Illnesses Associated With EndorphinsIllnesses Associated With Endorphins

Use of artificial opiates can cause body to stop manufacturing its own – this can lead to drug addiction