The Biology of Mind

Chapter 2

Biological Psychologists

• Study links between biological activity and behavior

• Also called neuroscientists, neuropsychologists, biopsychologists, physiological psychologists, behavior geneticists

• Cells brain behavior environment• Environment behavior brain cells

Neural Communication

• Neurobiologists and other investigators understand that humans and animals operate similarly when processing information.

Note the similarities in the above brain regions, which are all engaged in information processing.

Building Blocks of the Nervous System

• Neurons: cells specialized to receive and transmit information in the nervous system

• Brain is more complex than a computer but a little slower!

•

Parts of a Neuron • Cell Body: Life support center of the neuron.

• Dendrites: Branching extensions at the cell body. Receive messages from other neurons.

• Axon: Long single extension of a neuron, covered with myelin sheath to insulate and speed up messages through neurons.

• AWAY

• Axon speaks, cell body interprets, dendrites listen

• Terminal Branches of axon: Branched endings of an axon that transmit messages to other neurons.

Kinds of Neurons

• Sensory Neurons carry incoming information from the sense receptors to the CNS.

• Motor Neurons carry outgoing information from the CNS to muscles and glands.

• Interneurons located within the brain and spinal chord; they connect the two neurons.

Building Blocks of the Nervous System

• Neurons receive energy from the environment (i.e., light, sound, touch, heat) and change it to an electrical energy.

• Transduction– Process in which neurons transform energy from the

environment into electrical energy.

• Action potential– The electrical signals that contain information about

the experience (i.e., hearing a sound; looking at a cat).– Information travels down the axon of that neuron to

the dendrites of another neuron.

Action Potential

• A neural impulse. A brief electrical charge that travels down an axon and is generated by the movement of positively charged atoms in and out of channels in the axon’s membrane.

• The action potential propagates down the axon, without decreasing in size.

How to measure an action potential?

• The size of action potential remains consistent.– “all or none” release of electric charge

• The intensity of an action potential remains the same throughout the length of the axon.

• The rate of firing is measured (i.e., frequency)– Low stimuli intensities: slow firing and/or triggers

less neurons to fire– High stimuli intensities: fast firing and/or triggers

more neurons to fire

Rate of action potential

How Neurons Communicate

• Information passes from neuron to neuron in the brain.

• An electrical signal travels down the axon and then is transmitted to the dendrite of another neuron.

• Neurons are not connected with each other. The synapse is a gap between the axon of a neuron and the dendrite of another neuron.

• When the action potential reaches the end of the axon, synaptic vesicles open and release neurotransmitters which are picked up by the receiving dendrites.

Synapse • Synapse a junction between the axon tip of the sending

neuron and the dendrite or cell body of the receiving neuron.

• This tiny gap is called the synaptic gap or cleft.

Neurotransmitters

• Neurotransmitters are made by the brain or can be consumed artificially through Rx.

• Excitatory: increases neuron firing

• Inhibitory: decreases neuron firing

Reuptake

• Neurotransmitters in the synapse are reabsorbed into the sending neurons through the process of reuptake.

• This process applies the brakes on neurotransmitter action.

Neurotransmitters

For Fun!

• What happens if you flood the brain with acetylcholine?– What drug does this? (bwsv)

• What happens if you flood the brain with endorphins?– What drug does this? Natural? Artificial?

• What happens if you block the re-update of seratonin?– What drug does this?

• What happens if you block acetylcholine?– What drug does this?

Lock & Key Mechanism

• Neurotransmitters bind to the receptors of the receiving neuron in a key-lock mechanism.

Nervous Systems

CentralNervousSystem(CNS)

PeripheralNervousSystem(PNS)

The Nervous System

• Nervous System: Consists of all the nerve cells. It is the body’s speedy, electrochemical communication system.

• Central Nervous System (CNS): the brain and spinal cord.

• Peripheral Nervous System (PNS): the sensory and motor neurons that connect the central nervous system (CNS) to the rest of the body.

The Nervous System

Peripheral Nervous System

• Somatic Nervous System: The division of the peripheral nervous system that controls the body’s skeletal muscles.– Under the individual’s control

• Autonomic Nervous System: Part of the PNS that controls the glands and other muscles.– Not under the individual’s control – Think automatic

Autonomic Nervous System (ANS)

• Sympathetic Nervous System: Division of the ANS that arouses the body, mobilizing its energy in stressful situations.

• Parasympathetic Nervous System: Division of the ANS that calms the body, conserving its energy.

Autonomic Nervous System (ANS)

• Sympathetic NS “Arouses”

(fight-or-flight)

• Parasympathetic NS “Calms” (rest and digest)

• Think parachute –brings you down

Central Nervous System

• Interconnected neurons form networks in the brain.

• These networks are complex and modify with growth and experience.

Complex Neural Network

The Spinal Cord and Reflexes

• Certain reflexes are simple and do not involve the brain in order to respond. – These reflexes travel to the spinal cord, only.

The Endocrine System

• The Endocrine System is the body’s “slow” chemical communication system.

• Communication is carried out by hormones synthesized by a set of glands.

Hormones

• Hormones are chemicals synthesized by the endocrine glands that are secreted in the bloodstream. Hormones affect the brain and many other tissues of the body.

• For example, epinephrine (adrenaline) increases heart rate, blood pressure, blood sugar, and feelings of excitement during emergency situations.

Cognitive Processes and the Brain

• Cerebral cortex – External regions of the brain, about 3mm deep– Contains mechanisms responsible for most of our

higher mental functions.

Cognitive Processes and the Brain

• Temporal lobe: language, memory, hearing, perceiving forms

• Occipital lobe: vision

• Parietal lobe: touch, vision, attention

• Frontal lobe: language, thought, memory, motor functioning

The Cerebral Cortex• It is the body’s ultimate control and information

processing center.

Cognitive Neuroscience

• Cognitive psychology + neuroscience

• To study how the brain functions and gives rise to mental processes. – To correlate brain regions with specific processes.

• Use of technology to study brain regions. – Brain imaging techiniques.

Electroencephalogram (EEG)

Magnetic Resonance Imaging machine

Magnetic Resonance Imaging (MRI)

3 dimensional image of brain

Positron Emission Tomography (PET)

PET (positron emission tomography) Scan is a visual display of brain activity that detects a radioactive form of glucose while the brain performs a given task .

Functional Magnetic Resonance Imaging (fMRI)

Measures ratio of oxygenated blood to deoxygenated blood.Iron in blood is detected by the magnet in the scanner. Areas in yellow indicate more activation (more blood flow).

Language

Aphasia 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 & Integration• Brain activity when hearing, seeing, and speaking

words.

• Several brain regions are used simultaneously for certain mental functions.

Nervous System Interacts with Environment

• Brain adapts to environment– Brain can change to respond best to what is commonly

encountered.

• Plasticity– refers to the brain’s ability to modify itself after some

types of injury or illness.

• Brains exposed to different environmental experiences, injury, hormonal levels or genetic abnormalities, are molded in different ways. – Ex: right handed vs. left handed individuals young brain vs. older brain

Splitting the Brain

• A 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

Ma

rtin M

. Ro

the

r

Courtesy of T

erence William

s, University of Iow

a

Split Brain Patients

• With the corpus callosum severed, objects (apple) presented in the right visual field can be named. Objects (pencil) in the left visual field cannot.

Divided Consciousness

Right-Left Differences in the Intact Brain

• People 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.

• Right-handed people more likely process speech in the left hemisphere.

• Left-handed people more likely process speech in both hemispheres.