Unit 2 overheads: Biological psychology
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Biological Bases of Behaviour
Neuron: cell specialized to receive, process, and transmit
information to other cells: Soma, Dendrites, Axon
● myelin
sheath: insulating material, speeds up transmission
of signals
● terminal
buttons secrete neurotransmitters: chemical
messengers
● synapses:
the junction where information is transmitted
from one neuron to another
neural impulse: a complex electrochemical event
 positively charged sodium and potassium ions, and
negatively charged chloride ions, flow across the cell
membrane at different rates
 neuron’s resting potential is about -70 millivolts
when stimulated, channels in cell membrane open
and positively charged sodium ions rush in.
 creates an action potential: a very brief shift in the
neuron’s electrical charge that travels down the axon
 the channel closes back up very quickly
for a brief time the neuron cannot “fire” again: the
absolute refractory period is the minimum length of
time after an action potential during which another
action potential cannot begin (1 or 2 milliseconds)
 firing is “all-or-none”
 stronger stimuli make a cell fire more rapidly
Unit 2 overheads: Biological psychology
● neurons
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communicate here they meet: the synapse
● separated by the synaptic cleft: a microscopic gap
● presynaptic neuron and postsynaptic neuron
● neurotransmitters: stored in terminal button’s vesicles
● neurotransmitters diffuse across the cleft to the membrane
of the receiving neuron
● bind with special molecules at receptor sites on the
receiving neuron
● causes a postsynaptic potential (PSP)
●PSPs are graded potentials: increase/decrease the
probability of that neuron firing in proportion to the amount
of voltage change
● excitatory PSP: positive voltage shift, increases likelihood
that the neuron will fire
● inhibitory PSP: negative voltage shift, decreases
likelihood that the postsynaptic neuron will fire
● neurotransmitter is either reabsorbed via reuptake or
broken down by enzymes
● 15 to 20 neurotransmitters have been identified so far
● lock and key system: neurotransmitter has to fit to bind to
a site
Neurotransmitters
Acetylcholine (ACh)
●found throughout the nervous system
● motor movements
● attention, arousal, and memory
●nicotine is an Ach agonist
● curare is an antagonist for ACh
Unit 2 overheads: Biological psychology
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Monoamines
dopamine (DA), norepinephrine (NE), serotonin (5-HT)
●dopamine: voluntary movements
 degeneration of DA pathways causes Parkinsonism
●serotonin: sleep & waking, eating, aggression, impulsive
behavior
 depression: low NE, low 5-HT
 schizophrenia: high DA
● amphetamines increase release of DA and NE from
presynaptic neurons & slow reuptake
Endorphins
●endogenous morphines: internally produced opiates
●widely distributed throughout the body
● contribute to modulation of pain, experiences of euphoria
Nervous System
CNS
PNS
Somatic N.S.
Brain
Spinal
Cord
- skeletal
muscles
- afferent and
efferent
pathways
Autonomic N.S.
- basic life processes
Sympathetic
Parasympathetic
Unit 2 overheads: Biological psychology
PNS: nerves outside the brain and spinal cord.
● Nerves: bundles of neuron fibers (axons) routed
together in the PNS
● PNS divides into somatic n.s. and autonomic n.s.
Somatic N.S.
●nerves connecting to voluntary skeletal muscles and
sensory receptors
● info from receptors in skin, muscles, joints to the CNS
● commands from CNS to the muscles
●needs 2 pathways to do this
1) afferent nerve fibers: axons carrying information
inward to the CNS from the periphery of the body
2) efferent nerve fibers: axons carrying info outward
from the CNS to the periphery of the body
Autonomic N.S.
● nerves connecting to heart, blood vessels, glands, smooth
muscles
● involuntary functions (heart rate, digestion, perspiration)
●physiological arousal (fight or flight response)
● chronic autonomic arousal  stress, disease
● 2 branches: sympathetic and parasympathetic divisions
● sympathetic division: fight-or-flight response (slows
digestion, drains blood from the periphery, signals
adrenal glands to release hormones like adrenaline
● parasympathetic division: conserves bodily
resources (slows heart rate, lowers b.p., promotes
digestion)
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Unit 2 overheads: Biological psychology
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CNS: brain and spinal cord
● encased in sheaths called meninges
● cerebrospinal fluid (CSF)nourishes & protects
Spinal cord: connects the brain to rest of body through
the PNS
 bundles of axons carrying brain’s commands to
peripheral nerves & receiving information from
peripheral nerves to take back to brain
Brain: weighs 3 lbs, containing billions of cells
 integrates information from outside and inside the
body, coordinates the body’s actions, enables us to talk,
think, remember, plan, create, dream
4 techniques to Study the Living Brain
1) Electrical Recordings
 EEG (electroencephalogram): electrodes on surface of
head record patterns of electrical activity
 line tracings called brain waves
 different patterns associated with different states of
mental activity
 patterns of brain activity for specific behaviors and
specific emotions (e.g. anxiety)
 studying stages of sleep
Unit 2 overheads: Biological psychology
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2) Lesioning: selectively disable specific brain areas in
animals
 high-frequency electric current through an electrode
to burnt tissue
 stereotaxic instrument: used to implant electrodes at
precise locations
3. Electrical Stimulation of the Brain (ESB)
 weak electric current stimulates (activates) brain areas
4. Brain Imaging Procedures
 CT scan (computerized tomography): X-rays at different
angles, provides an image of a brain “slice”; can also
visualize the whole brain by assembling a series of images
representing successive slices of the brain
● permits us to examine brain structure
 PET scan (positron emission tomography): uses
radioactive substances to portray brain function
● can map brain activity
● radioactively tagged chemicals serve
as markers for blood flow or metabolic activity
● indicates what parts are more active than others
when performing specific tasks or feel specific
emotions
 MRI (magnetic resonance imaging): magnetic fields &
radio waves to map brain structure.
● better images that CT scans can give
● 3-D pictures of the brain with very high resolution
Unit 2 overheads: Biological psychology
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 functional MRI (fMRI): both functional and structural
information in the same image
Brain Structures and Their Functions
3 major regions: the hindbrain, the midbrain, and the
forebrain.
Hindbrain
● cerebellum, medulla, pons
 medulla: attaches to the spinal cord, in charge of
largely unconscious vital functions like circulation,
breathing, maintaining muscle tone, reflexes like
sneezing, coughing, salivating
 pons: a bridge of fibers that connects the brain stem
to the cerebellum; also clusters of cell bodies (called
nuclei) involved in sleep and arousal
 cerebellum (“little brain”): coordination of
movement, equilibrium, physical balance; also
coordinates sensory information that guides
movements
Midbrain
● lies between the forebrain and the hindbrain
●sensory processes (e.g. turning head in direction of a noise)
● voluntary movements (dopamine pathways).Parkinsonism
is due to degeneration in this area
● reticular formation runs through the hindbrain and the
midbrain: contributes to muscle reflexes, breathing, pain
perception, and regulation of sleep and arousal
Unit 2 overheads: Biological psychology
Forebrain
● largest and most complex region
● includes thalamus, hypothalamus, and limbic system at
its core, and above them, the cerebrum and its outer layer,
the cerebral cortex
 Thalamus: a way-station
● a number of clusters of cell bodies, or somas, each
concerned with relaying sensory info to a particular
part of the cortex
 Hypothalamus: a regulator of biological needs
● near base of the forebrain, under the thalamus
● controls the ANS, the endocrine system via the
pituitary gland
● “Four Fs”: fighting, fleeing, feeding, fornicating
 Limbic System: the seat of emotion
● includes parts of the thalamus, hypothalamus,
hippocampus, amygdala
● hippocampus: memory processes: spatial memory,
consolidation of new info into long term memory
● amygdala: fear response, rage response
●pleasure centers: e.g. where the medial forebrain
bundle passes through the hypothalamus
● opiates and stimulants work by exciting this
dopamine system
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Unit 2 overheads: Biological psychology
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 Cerebrum: the seat of complex thought
●largest and most complex part of the human brain
●learning, remembering, thinking, consciousness
●cerebral cortex: the thin outer layer
● 2 hemispheres connected by the corpus callosum
● each hemisphere has 4 lobes
1) occipital lobe: includes the primary visual
cortex, where visual information gets processed
2) parietal lobe: registers the sense of touch, called
the primary somatosensory cortex
3) temporal lobe: includes the primary auditory
cortex
4) Frontal lobe: includes the primary motor cortex
 amount of cortex for each body area reflects
its complexity, not its actual size
 prefrontal cortex: portion in front of the
motor cortex, contributes to higher-order
functions: memory, reasoning, executive
control (planning, paying attention,
organization)
Left Hemisphere
● frontal lobe: Broca’s area (language generation)
● temporal lobe: Wernicke’s area (language
comprehension)
Right Hemisphere
● visuo-spatial tasks, recognizing faces
Unit 2 overheads: Biological psychology
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Split Brain Research
● corpus callosum is cut to reduce epileptic seizures
● each hemisphere controls the motor & sensory
functions to and from the opposite side of the body
● visual system: stimuli in the right half of the visual
field in both eyes goes to the LH; stimuli in the left half
of the visual field in both eyes goes to the RH
● auditory system: inputs to each ear go to both
hemisphere, but connections to the opposite
hemisphere are stronger or more immediate
Gazzaniga, Bogen, & Sperry (1965)
●presented visual stimuli in a single visual field
● stimuli only lasted a fraction of a second
● pictures flashed to the right visual field: subjects were
able to name what they were seeing
● pictures flashed to the left visual field: not able to
name what they were seeing
● but RH did process information
- People could point out a picture of an object they
had held in their left hand
- people could point out pictures of things flashed
to their left visual field
● RH is superior for assembling puzzles & copying
drawings, even when the person is right handed
Unit 2 overheads: Biological psychology
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Specialization of the Hemispheres in an Intact Brain
● perceptual asymmetries: left/right imbalances in the
speed of visual or auditory processing
- in normal people the input sent to one hemisphere is
quickly shared with the other
- but subtle differences can be detected by measuring
how long it takes subjects to recognize different kinds
of stimuli
● findings: the 2 hemispheres are specialized (LH- language,
logical thinking; RH – visual-spatial, recognizing emotions,
expressing emotions, classical conditioning.)
the endocrine system  a system of glands that secrete
chemicals called hormones into the blood stream to help
control body functioning.
Hormones: chemicals released by endocrine glands
● long-term regulation of basic bodily processes
● glands are like synapses but with distant receptors
● some chemicals act as neurotransmitters in CNS and
as hormones in the endocrine system
● 30 different hormones; some have specific targets and
some have targets all over the body
hypothalamus pituitary gland  stimulates other endocrine glands
●pituitary  gonadotropins, affecting the gonads (prebirth formation of external sex organs; increased levels
of sexual hormones at puberty to develop secondary
sex characteristics (female breasts, male facial hair, etc.)
Unit 2 overheads: Biological psychology
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Genetics and Behavior
Behavioural genetics: studies the influence of genetic factors
on behavioural traits.
Principles of genetics
chromosomes: strands of DNA molecules carrying genetic
information
●every cell (except sperm & egg) contains 46
chromosomes
genes: DNA segments, the key functional units in hereditary
transmission
- homozygous condition: 2 genes in a pair are the same
- heterozygous condition: the 2 genes in a pair are
different
single gene inheritance: a single pair of genes determines a
trait (e.g. attached versus detached earlobes)
 dominant gene: expressed when paired genes differ
 recessive gene: masked when paired genes differ
genetic relatedness
with each parent, 50%
with siblings, 50%
with identical twin, 100%
Genotype: a person’s genetic makeup
Phenotype: genotype’s manifestation in observable
characteristics
Unit 2 overheads: Biological psychology
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Polygenic Inheritance: influenced by more than one pair of
genes.
Studies to Assess Genes versus Environment
Family Studies: examining blood relatives to see how much
they resemble one another on a specific trait.
 Problem: doesn’t tease out the impact of a shared
environment
Twin Studies: comparing the resemblance of identical twins
and fraternal twins on a specific trait.
● identical (Monozygotic) twins are 100% identical
●fraternal (Dizygotic) twins are no more similar than
any 2 siblings (50%)
● if identical twins exhibit more similarity on a trait
than fraternal twins, this is likely due to heredity
Adoption studies: examining the resemblance between
adopted kids and both their biological and adoptive parents.
● adopted in infancy, raised without contact with
biological parents
●if adopted kids resemble their biological parents on a
trait more than they resemble their adoptive parents,
then this suggests a genetic influence on that trait
● if adopted kids resemble their adoptive parents more,
this show it was more influenced by environment than
genes
“We inherit dispositions, not destinies.”
Unit 2 overheads: Biological psychology
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Parental Investment and Mating Systems
● parental investment what each sex has to invest to
produce and nurture offspring.
● in most mammalian species, males don’t have to
invest much more than their sperm to pass their genes
on to the next generation. So, males’ reproductive
potential is maximized by mating with as many as
possible. Males will compete with each other for mating
opportunities.
● females typically have to invest a lot more: time
carrying the developing fetus, danger in giving birth,
nourishing and caring for the offspring once born. They
have a limited number of offspring they can produce,
regardless of how many males they mate with. So,
females don’t have an incentive to mate with many
males. They optimize their reproductive potential by
being picky in terms of good genes and/or access to
material resources.
● polygyny: where each male seeks to mate with
multiple females, who in turn only mate with him.
o natural selection favors males who compete
aggressively for copulation opportunities
o females mate with the winners who presumably
have “better genes”
Unit 2 overheads: Biological psychology
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● polyandry: each female seeks to mate with as many
males as possible, whereas each male mates with only
one female
o emerges when parental investment is high for
males and low for females (e.g. female spotted
sandpipers)
o relatively rare
● monogamy: where one male and one female mate
exclusively, or almost exclusively, with each other
o when male and female investment is about even,
and both parents raise the young (many bird
species, some mammals, like wolves and foxes)
o sometimes even here they mate outside their pair
bond (cheating!)
Hemispheric Specialization and Handedness
● the
superiority of one hemisphere over another for tasks
like recognizing letters, words, faces, and melodies, is only
modest.
● in normal people, the hemispheres never work alone
● some people display very little specialization
● others reverse the usual specialization
● especially common in left-handed people
● Rasmussen & Milner (1977): bilateral representation of
speech for 15% of left-handers (versus 0% of right-handers);
reversal of specialization in another 15% of left-handers
(versus about 5% of right-handers)