The Biological Perspective
Chapter 2
What is Biological Psychology?
 Neuroscience – science that deals with the structure and
functioning of the brain and the neurons, nerves, and nervous
tissue that form the nervous system
 Biological Psychology or Behavioral Neuroscience –
branch of neuroscience that focuses on the biological bases of
psychological processes, behavior, and learning
 How the nervous system works provides information about
what is going on inside the body when you engage in a
specific behavior, feel an emotion, or have an abstract thought
Nervous system
nervous system
Central nervous
system (CNS)
Spinal cord
nervous system
Somatic nervous
Overview of the Nervous System
 Nervous system – a network of cells that carries information to
and from all parts of the body (4 levels)
 Central nervous system (CNS) – brain and spinal cord
 Brain – interprets and stores information and sends orders to muscles,
glands, and organs
 Spinal cord – pathway connecting the brain and the peripheral nervous
 Peripheral nervous system – transmits information to and from
the CNS
 Autonomic nervous system – automatically regulates glands, internal
organs and blood vessels, pupil dilation, digestion, and blood pressure
 Parasympathetic division – maintains body functions under ordinary
conditions; saves energy
 Sympathetic division – prepares the body to react and expend energy
in times of stress
 Somatic nervous system – carries sensory information and controls
movement of the skeletal muscles
Structure of the Neuron: The Nervous
System’s Building Block
 Neuron – the specialized cell in the nervous system that
receives and sends messages within that system
 One of the body’s messengers, therefore it has a very special
 3 main parts of a neuron
 Dendrites – branchlike structures that receive messages from
other neurons
 Soma – the cell body of the neuron responsible for maintaining
the life of the cell
 Axon – tube-like structure that carries the neural messages out
to other cells
Structure of the Neuron
Structure of the Neuron
 Neurons only make up 10% of cells in
the brain
 Other 90% is glial cells
 Glial cells – cells that provide structure
for the neurons to grow on and around,
deliver nutrients to neurons, and
produce myelin
 Myelin – fatty substances produced by
glial cells that coat the axons of neurons
to insulate, protect, and speed up the
neural impulse
Structure of the Neuron
 2 types of glial cells produce myelin for the neurons in the
nervous system
 Oligodendrocytes – produce myelin for the neurons in the brain and
spinal cord (CNS)
 Schwann cells – produce myelin for the neurons of the body (PNS)
 Axons travel all over the body like cables, carrying messages
 Myelin wraps around the axon forming a protective sheath
(myelin sheath)
 Nerves – bundles of axons coated in myelin that travel together
through the body
Structure of the Neuron
 How do neurons send messages?
 When a neuron is at rest (not firing an impulse or message) it is
actually electrically charged
 Inside and outside the cell, charged particles called ions are in a
semi-liquid (jelly-like) solution
 The relative charge of ions inside the cell is mostly negative
 The relative charge of ions outside the cell is mostly positive
Structure of the Neuron
 Cell membrane is “semipermeable” meaning that tiny
substances inside and outside the cell can pass through
channels in the membrane
 Inside the cell, there are smaller positively charged potassium
ions and larger negatively charged protein ions
 Negatively charged protein ions are too big to go through the
channels when the cell is at rest, leaving the inside of the cell
with a mostly negative charge
 Outside the cell, there are lots of positively charged sodium
ions and negatively charged chloride ions
 Unable to go into the cell when it is at rest because the channels
are closed
Structure of the Neuron
 Positively charged sodium ions cluster around the outside of
the cell because the inside of the resting cell is mostly
negatively charged and opposite charges attract
 This difference in charges creates an electrical potential
 Resting potential – the state of the neuron when not
firing a neural impulse
Structure of the Neuron
 When the cell receives a strong enough stimulation from another
cell (meaning the dendrites are activated) the channels in the cell
membrane open up all down the cell and allow the sodium ions
(positively charged) to rush into the cell
 Causes reversal in electrical charge - the inside of the cell becomes
mostly positive and the outside becomes mostly negative (because
many of the positive sodium ions are now inside the cell)
 Sodium ions begin entering the cell through the first channel that
opens up, the channel closest to the soma
 The rest of the ion channels open up all down the axon in a kind of
chain reaction
 Change in electrical charge is called the Action Potential because
the electrical potential is now in action, rather than at rest (like in
resting potential)
Structure of the Neuron
 During action potential, the cell becomes positive inside
and negative outside
 After the action potential passes, the cell has to return back
to its resting potential, meaning it has to get the positively
charged sodium ions out
 Ion channels close immediately after the action potential passes
 Then, the cell membrane literally pumps the positive sodium
ions out
 Meanwhile, small positively charged potassium ions inside the
neuron move out rapidly helping to restore the negative charge
inside the cell
Structure of the Neuron
 To start an action potential, the neuron must receive a signal
strong enough to break the threshold for firing
 Neurons are receiving “Fire!” and “Don’t Fire!” messages from
other neurons constantly
 When the “Fire!” messages are great enough to cancel out the
“Don’t Fire!” messages, the threshold is crossed and the neuron
 Neurons fire in a sort of “all-or-none” fashion, either firing at
full strength or not firing at all
 Like a light switch, when its on, its on and when its off, its
off…. No dimmer switch
Sending the Message to Other Cells:
The Synapse
 The end of the axon fans out into several short fibers that
have swellings or little knobs on the ends called synaptic
knobs or axon terminals
 The synaptic knobs are filled with little saclike structures called
synaptic vesicles
 Synaptic vesicles are filled with chemical substances called
neurotransmitters (the message carriers)
Sending the Message to Other Cells:
The Synapse
 Next to the synaptic knob is the dendrite of another neuron, in
between them is a fluid-filled space called the synapse or the
synaptic gap
 Remember, in the synaptic knob are vesicles full of
 The dendrite next to the synaptic knob contains ion channels
that have receptor sites
 Receptor sites – proteins that allow only particular molecules
of a certain shape to fit into it
Sending the Message to Other Cells:
The Synapse
 When the action potential reaches the synaptic knob, it
causes the vesicles to release their neurotransmitters into the
 The neurotransmitters float across the synapse and many of
them fit themselves into the receptor sites
 This opens the ion channels and allows sodium ions to rush
in, activating the next cell
 The next cell may be another neuron, or a cell on a muscle or
Sending the Message to Other Cells:
The Synapse
 When neurotransmitters bind to receptor sites they have one
of two possible effects (remember the “Fire!” and “Don’t
Fire!” signals?) which depend on what kind of synapse they
are release into
 Excitatory synapse – ion channels open causing the next cell
to fire
 Inhibitory synapse – ion channels close causing the next
neuron to stop firing
 Start a 1:07
Neurotransmitters: Messengers of the
 At least 50 – 100 different types of neurotransmitters in the
human body
 Acetylcholine - 1st neurotransmitter to be discovered
 Excitatory
 Causes muscles to contract
 Roles in cognition, particularly memory
 GABA (Gamma Amino Butyric Acid)
 Inhibitory
 Decreases the activity level of neurons in the brain
Neurotransmitters: Messengers of the
 Serotonin
 Both excitatory and inhibitory
 Linked with sleep, mood, and appetite
 Dopamine
Both excitatory or inhibitory
Involved in control of movement and sensations of pleasure
Low levels have been found to cause Parkinson’s disease
Increased levels linked to schizophrenia
 Endorphins
 Special type of neurotransmitter called a neural regulator
 Controls the release of other neurotransmitters
 When endorphins are released in the body, the neurons transmitting
information about pain are not able to fire action potentials
Neurotransmitters: Messengers of the
 Some chemicals not naturally found in the body can either
enhance or block the effects of neurotransmitters on
receptor sites
 Fit into receptor sites on target cells
 2 types
 Agonists – mimic or enhance the effects of a neurotransmitter
 Antagonists – block or reduce a cell’s response to the action
of a neurotransmitter
Neurotransmitters: Messengers of the
 Antagonist Example: Acetylcholine – neurotransmitter
found at the synapses between neurons and muscle cells,
causes muscles to contract
 If acetylcholine receptor sites on the muscle cells are
blocked, then the acetylcholine cant get to the site and the
muscle will be incapable of contracting (meaning the muscle
is paralyzed)
 Curare a drug used on poison blow darts is just similar
enough to fit into the receptor site without actually
stimulating the cell
 This blocks acetylcholine from its receptor sites causing
Neurotransmitters: Messengers of the
 Agonist Example: Acetylcholine causes most muscles to
contract, but actually slows the contraction of the heart
 Black widow spiders’ venom stimulates the release of
excessive amounts of acetylcholine and causes convulsions
and possible death
Reuptake and Enzymes
 After neurotransmitters are released into the synapse they
must be taken back into the axon they came from before the
next stimulation can occur
 Reuptake – process by which neurotransmitters are taken
back into the synaptic vesicles
 However acetylcholine which simulates muscles must be
cleared out of the synapse more quickly (no time for the
“sucking up” process)
 A special enzyme specifically designed to break apart
acetylcholine clears the synapse very quickly (called enzymatic
The Central Nervous System: The
“Central Processing Unit”
 CNS = brain and spinal cord
 Brain – core of the nervous system
 Spinal cord – long bundle of neurons
 Divided into 2 areas that serve 2 vital functions
 Outer area – composed mainly of myelinated axons and nerves
 “Message pipeline” - Carries messages from the body up to the brain and
from the brain down to the body
 Inner area – mainly composed of cell bodies separated by glial
 “Primitive brain” – responsible for certain reflexes, very fast, lifesaving
The Central Nervous System: The
“Central Processing Unit”
 Inside of the spinal cord contains 3 types of neurons that
make up the reflex arc
 Afferent (sensory) neurons – carry messages from the
senses to the spinal cord
 Ex. If you burn your finger, afferent neurons relay information about the
sharp pain in your finger
 Efferent (motor) neurons – carry messages from the spinal
cord to the muscles and glands
 Ex. Send command to pull your finger back from the painful stimulus
 Interneurons – connect the afferent (sensory) neurons to the
efferent (motor) neurons
 Help coordinate signals between sensory neurons and motor neurons
The Central Nervous System: The
“Central Processing Unit”
 Neuroplasticity – the ability of the brain and spinal cord to
change in structure and function
 Can change the structure and function of many cells in response
to experience and trauma
 Stem cells – cells that can become other cells (blood cells,
nerve cells, and brain cells)
 Facilitate neuroplasticity
 If stem cells can be successfully implanted into damaged areas in
the spinal cord, the newly developed neurons may be able to
assume the roles that the damaged neurons can no longer
The Peripheral Nervous System:
Nerves on the Edge
 Peripheral nervous system (PNS) – made up of all the
nerves and neurons that are NOT in the brain and spinal cord
 Includes all the nerves that connect to your eyes, ears, skin,
mouth, and muscles
 Allows the brain and spinal cord to communicate with these
sensory systems
 Divided into 2 major systems
 Somantic nervous system – controls the senses and
voluntary muscles
 Autonomic nervous system – controls organs, glands, and
involuntary muscles
The Somantic Nervous System
 2 parts
 Sensory pathway – all the nerves carrying messages from the
senses to the CNS (nerves containing afferent neurons)
 Nerves from the body going to the CNS to relay information
 Motor pathway – all the nerves carrying messages from the
central nervous system to the skeletal muscles of the body (nerves
containing efferent neurons)
 Nerves from the CNS going out to the body telling the body what to do
The Autonomic Nervous System
 2 systems
 Sympathetic division – turns on the body’s fight-or-flight
reactions, including increased heart rate, increased breathing, and
dilation of your pupils
 “fight-or flight system”
 Active during times of stress
 Parasympathetic division – controls the body when it’s in a state
of rest to keep the heart beating regularly, to control normal
breathing, and to coordinate digestion
 “eat-drink-rest system”
 Active most of the time
Distant Connections: The Endocrine
 Sort of the 2nd messenger system in the body
 Endocrine glands – have no ducts and secrete chemicals
called hormones directly into the blood stream
 Hormones are carried by the blood stream to organs in the
 Compared to communication between neurons, the
hormonal system is slower, and has more widespread effects
on the body and behavior
The Pituitary: Master of the Hormonal
 Pituitary Gland – master gland, controls or influences all
of the other endocrine glands
 located in the brain just below the hypothalamus
 Hypothalamus controls the glandular system by influencing the pituitary
 Secretes the hormones that control milk production and salt
levels in the body and growth from infancy to adulthood
The Pineal & Thyroid Glands
 Pineal gland
 Located in the brain, near the back,
directly above the brain stem
 Secretes melatonin – hormone that
helps track day length and contributes
to the regulation of the sleep-wake
cycle in humans
 Thyroid gland
 Located in the neck
 Secretes a hormone that regulates
metabolism (how fast the body burns
its available energy)
The Pancreas & Gonads
 Pancreas
 Controls the level of blood sugar in the body by secreting
insulin and glucagons
 Too little insulin = diabetes
 Too much insulin = hypoglycemia
 Gonads
 Sex glands, secrete hormones that regulate sexual behavior and
 Called ovaries in females
 Called testes in males
Adrenal Glands
 2 Adrenal glands - located on the top of each kidney
 Critical role in regulating the body’s response to stress
 Adrenal glands are divided into 2 parts
 Adrenal medulla – releases epinephrine and norepinephrine when
people are under stress and aids in sympathetic arousal
 Adrenal cortex – produces over 30 different hormones called
 Most important is cortisol – released when the body feels both physical and
psychological stress
Looking Inside the Brain: Deep
 How can psychologists find out about what parts of the brain
 In animals – deliberately damage a part of the brain then test
the animal to see what has happened to its abilities
 Deep lesioning - a thin wire, insulated everywhere except the
tip, is surgically inserted into the brain. Then an electrical
current strong enough to kill off the target neurons is sent
through the tip of the wire
 In humans – study and test people who already have brain
 Not ideal – no 2 injuries are exactly the same
Brain Stimulation
 Electrical stimulation of the brain (ESB)
 Less harmful than lesioning
 Temporarily disrupt or enhance the formal functioning of specific brain
areas through electrical stimulation
 Invasive techniques – deep brain stimulation (DBS)
 Surgically implant electrodes in specific deep-brain areas which are connected to
an impulse generator that is surgically implanted under the collar bone
 Used in treatment for Parkinson’s disease and seizure disorders
 Noninvasive techniques – repetitive transcranial magnetic stimulation (rTMS) and
transcranial direct current stimulation (tDCS)
 rTMS – magnetic pulses are applied to the cortex using special copper wire coils
positioned over the head
 tDCS – uses scalp electrodes to pass very low amplitude direct currents to the
Mapping Brain Structure
 Computed Tomography (CT) – series of brain x-rays
 Involves mapping slices of the brain using a computer
 Magnetic Resonance Imaging (MRI) – uses a magnetic
field to “take pictures” of the brain
 More detail than CT scans
CT scan
MRI scan
Mapping Brain Function
 Electroencephalogram (EEG) – provides a record of the electrical
activity of groups of neurons just below the surface of the skull
 Functional Magnetic Resonance Image (fMRI) – uses magnetic
fields in the same way as an MRI, but goes a step further and pieces the
pictures together to show changes over a short period of time
 Positron Emission Tomography (PET) – involves injecting a person
with a low dose of radioactive substance and then recording the activity
of that substance in the person’s brain
 Single Photon Emission Computed Tomography (SPECT) –
similar to PET but uses somewhat different radiotracer technique
From the Bottom Up: The Structures of
the Brain
 The brain can be roughly divided into 3 sections
 Brainstem – lowest part of the brain that connects to the
spinal cord
 Cortex – outer wrinkled covering of the brain
 Structures under the cortex (subcortical structures) –
includes everything between the brainstem and the cortex
 4 important structures
 Medulla – controls life-sustaining functions such as heart beat,
breathing, and swallowing
 Pons – influences sleep, dreaming, and coordination of
 Reticular formation – plays crucial role in attention and
arousal, such as attending to certain kinds of information in the
 Cerebellum – controls all involuntary, rapid, fine motor
movement (ex. People can sit upright in a chair because the
cerebellum controls all the little muscles that keep you from
falling out of the chair)
Structures Under the Cortex
 Limbic system – involved in emotions, motivation, memory, and learning
 Thalamus – round structure in the center of the brain
 Hypothalamus – just below the front of the thalamus
 Hippocampus – in the temporal lobes on each side of the brain
 Amygdala – near the hippocampus
 Cingulate cortex – in the cortex, right above the corpus callosum in the
frontal and parietal lobes
The Limbic System
 Thalamus – receives input from sensory systems, processes
it, and then passes it on to the appropriate area
 Every sensation passes through the thalamus except for smell
 Hypothalamus – interacts with the endocrine system to
regulate body temperature, thirst, hunger, sleeping, sexual
activity, and mood
 Hippocampus – critical in the formation of long-term
memories and for memories of the locations of objects
 Amygdala – involved in response to fear
 Cingulate cortex – important role in emotion and
The Cortex
 Cortex – outermost part of the brain (wrinkly part)
 Made up of tightly packed neurons and is actually only about 1/10 of an
inch thick
 Corticalization – refers to the fact that the cortex is wrinkled, allowing
a much larger area of cortical cells to exist in the small space inside the
 Divided into right and left sections called cerebral hemispheres
 Cerebral hemispheres communicate with each other through the
corpus callosum
 Corpus callosum – thick bank of neurons (axons)
The Cortex
 Each cerebral hemisphere can be roughly divided into 4
sections called lobes
 Occipital lobes
 Parietal lobes
 Temporal lobes
 Frontal lobes
Occipital Lobes
 Visual information
 Primary visual cortex – processes visual information
from the eyes
 Visual association cortex – helps identify and make sense
of the visual information from the eyes
 Example: a patient who had a tumor in the right occipital lobe
area in the visual association cortex could see and even describe
objects in physical terms but couldn’t identify them
 Described a rose as a “red inflorescence” with a green tubular projection
Parietal Lobes
 Process information regarding touch, temperature, body
position, and possibly taste
 Somatosensory cortex – processes information from the
skin and internal body receptors for touch, temperature, and
body position
Temporal Lobes
 Process auditory information
 Primary auditory cortex – processes auditory
information coming in from the ears
 Auditory association area - helps identify and make
sense of the auditory information from the ears
Frontal Lobes
 Responsible for higher mental functions such as planning,
personality, and decision making, as well as language and motor
 Motor cortex – band of neurons that control the
movements of the body’s voluntary muscles by sending
commands out to the somatic division of the peripheral nervous
 Mirror neurons – recent research: neurons that fire while
an individual is performing an action as well as when an
individual is watching someone else perform that same action
The Association Areas of the Cortex
 Association areas – made up of neurons in the cortex that
are devoted to making connections between the sensory
information coming into the brain and stored memories,
images, and knowledge
 In other words, help people make sense of incoming sensory
 2 important association areas
 Broca’s area – left frontal lobe
 Wernicke’s area – left temporal lobe
Association Areas of the Cortex
 Broca’s area – responsible for speech production
 Allows people to speak smoothly and fluently
 Broca’s aphasia - Damage to Broca’s area causes a person not to be
able to produce the words they want to speak
 Can understand what others say, but cannot speak fluently
 (teenage
 Wernicke’s area – involved in understanding the meaning of
 Wernicke’s aphasia – damage to Wernicke’s area causes a person to
use words that don’t make sense and sometimes have trouble making
sense of what others say
 Can still speak fluently, but will use the wrong words
 (dentist)
Specialization of the Cerebral
 Roger Sperry – discovered that the right and left
hemispheres are not identical
 Split-brain research – cut through the corpus callosum (the
communication point between the hemispheres)
 Right and left hemispheres cannot communicate with each
 This research has revealed that the right and left hemispheres
are lateralized, meaning that they specialize in different things
 Left hemisphere – processes information in a sequence
and is good at breaking things down into smaller parts for
 Right hemisphere – processes information all at once and
simultaneously, a more global or holistic style of processing
Left Hemisphere
Right Hemisphere
Controls the right hand
Controls the left hand
Spoken language
Written language
Visual-spatial perception
Mathematical calculations
Music and artistic processing
Logical thought processes
Emotional thought and recognition
Analysis of detail
Processes the whole
Pattern recognition
Facial recognition
Applying Psychology to Everyday Life
 Attention-deficit/hyperactivity disorder (ADHD) –
developmental disorder involving behavioral and cognitive aspects
of inattention, impulsivity, and hyperactivity
 Brain areas involved in ADHD are typically divided:
 Areas responsible for regulating attention and cognitive control
 Areas responsible for alertness and motivation
 Neuroimaging studies: Cortical areas involved in attention and
cognition are found to be smaller in people with ADHD
Prefrontal cortex (primarily right side)
Basal ganglia (involved in response control)
Corpus callosum
Applying Psychology to Everyday Life
 Most problematic aspects of attention and cognition in
people with ADHD:
 Vigilance (being able to “watch out” for something important)
 Being able to effectively control one’s own cognitive processes
such as staying on task, maintaining effort, or engaging in selfcontrol
 New research is examining the possibility that ADHD may
have multiple causes
Environmental factors (such as low-level lead exposure)
Genetic influences
The role of heredity and familial factors
Personality factors

The Biological Perspective