Unit 3 – Biology of the BrainModule 9 – Biological Psychology and Neurotransmission

Early Models

To think, feel or act without a body would be like running without legs

Biological Psychologists – Scientific study the links biology (genetics,

neural, hormonal) and psychological processes

Phrenology- study of bumps on skull could reveal mental abilities

and personality traits

Localization of Function – various brain regions have different

functions

Neural Communication

Neuron

Neural Communication

Dendrites Listen, Axons Speak

• Axons can be long, up to several feet long

• Axons encased in Myelin Sheath, a layer of fatty tissue insulates wiring and

speeds impulses

• Sheath is laid down until age 25, helping neural efficiency, judgement and self

control

• Multiple Sclerosis: degeneration of myelin sheath; communication to muscles

slows with eventual loss of muscle control

Transmission

Transmission

• Action Potential – neural impulse, a brief electrical charge that travels down the

axon (travel is between 2 and 180 mph)

• Neurons generate electricity from chemical events; chemistry to electricity process

• Ions (electrically charged atoms) are exchanged

• Outside axon is POSTIVE charge, inside axon is NEGATIVE charge

• Positive outside/negative inside state is called Resting Potential

• When resting the membrane of the axon is selectively permeable; allowing only

certain ions into its gates

• Once a neuron fires, gates open one after another allowing the positive ions to

flood into the axon

• Refractory Period is when the neuron pumps the positively charged sodium ions

outside

• Neural signals can be excitatory (accelerator) or inhibitory (slowing)

• Impulse must reach Threshold to signal action potential

• Level of stimulation needed to trigger response

• Increase stimulation above threshold will not increase neural response; its All or

Nothing Response system fires full strength or not at all

Transmission

Neurons Firing

Neurotransmitters, Motions and Emotions

• A brain pathway may use only one or two neurotransmitters

• Particular neurotransmitters affect specific behaviors and emotions

• They don’t operate in isolation, they interact and their effects vary with the

receptors they stimulate

• Endorphins - naturally occurring neurotransmitter similar to morphine

• Exercise releases “runner’s high”

• One problem with using opiates, the brain may stop producing its own natural

opiates

• Drugs and other chemicals affect brain chemistry at the synapses by exciting or

inhibiting neuron firing - molecules mimic natural neurotransmitter

Nervous System Information

•Travels through 3 types of neurons:

•Sensory Neurons – carries messages from body tissue and sensory receptors

inwards to the brain and spinal cord for processing

•Motor Neurons – carries messages from central nervous system out to the body’s

muscles and gland

•Interneurons– processes information between sensory input and motor output

40 Billion neurons, each connection with roughly 10,000 other neurons, we end up

with somewhere around 400 trillion synapses

A space equal to a grain of sand contains around 100,000 neurons and 1 billion

synapses

Neurons cluster into NEURAL NETWORKS

Neural pathways govern our Reflexes, our automatic responses to stimuli

Nervous System Endocrine System

Released from terminals

into synapses

Triggered by electric

impulses (nervous system)

Rapid and specific

delivery of message

Effect behavior,

digestion, reproduction,

mood and metabolism

Bind to specific receptor

sites

Chemical released inside

our bodies

Released by endocrine

glands into the

bloodstream

Chemical signals:

hormones

Take time to have an

effect; last longer than

messages sent with

nervous system

Studying the Brain, and Older Brain Structures

Tools of Discovery

Electroencephalogram (EEG)– amplified recording of the waves of electrical

activity sweeping across the brain surface – measured by electrodes places on

scalp

Computed Tomography (CT)– series of X-ray photographs taken from different

angles and combined for a composite representation of a slice of the brain

Positron Emission Tomography (PET)– visual display of the brain that detects

where a radioactive form of glucose goes when the brain is performing a

certain task

Magnetic Resonance Imaging (MRI)– uses magnetic fields and radio waves to

produce computer generated images of soft tissue

Older Brain Structures

The Brainstem – Oldest Part and Central CoreResponsible for automatic survival functions

Medulla – base of brainstem;

controls heartbeat and breathing

Pons – just above Medulla;

helps coordinate movement

Thalamus – at the top of the brainstem; sensory control center (hub of sensory

traffic), directs messages to sensory receiving area in the cortex and transmits

replies to cerebellum and medulla

The Reticular Formation – nerve network that travels through the brainstem and

thalamus and play important role in controlling arousal

The Cerebellum– extending from the rear of the brainstem “little brain”; non verbal

learning and memory, judge time, modulate emotion and discriminate sound and

textures; can coordinate voluntary movement

THE LIMBIC SYSTEMBetween the oldest and newest parts of the brain

Amygdala – two lima bean sized clusters linked to emotion; linked to

aggression and fear (includes perception of emotions and processing of

emotional memories

Hypothalamus – directs several maintenance activities: eating, drinking, body

temperature, endocrine system, linked to emotion and reward

• Reward Deficiency Syndrome– may be a the root of many addiction

disorders

Cerebral Cortex

Cerebral Cortex – thin surface layer of interconnected neural cells; thinking crown;

ultimate control center *compared to bark on a tree

- our ability to think and adapt, and not operate on rigid genetic instructions,

is a result of the larger cortex mammals have

Structure of the Cortex- contain around 20 to 23 billion nerve class and 300 trillion

synaptic connections.

Glial Cells - glue cells, or worker bees, that feed and sheath

these cells play a role in learning and thinking by “chatting” with neurons

they participate in information transmission and memory

Brain Computer Interface– use of electrodes to decode cognitive neural signals to

control an external device, such a robotic arm

Association Areas – all the cortical areas (visual, auditory, motor, sensory) occupy

about ¼ of the brain cortex

- intelligent animals have increased amounts of “uncommitted” space, called

association areas. These vast areas of the brain are responsible for

interpreting, integrating and acting on sensory information and linking it with

stored information

Broca’s Area–

controls speaking

Wernicke’s Area–

controls

comprehension

Brain Plasticity– the ability of the brain to reorganize and repair itself after damage

Research on brain damage has revealed two things:

- severed neurons usually do not regenerate

- some brain functions see preassigned to specific areas

Ability to repair itself relies on building new pathways or producing new brain cells

Neurogenesis- formation of new neurons