Download Biological Impact

Biological Psychology
….explaining human behavior
through biology
Remember from class our list of the
“biological events” that might be
involved in (i.e., might help explain)
human behavior?
• Genetic make-up—the genetic inheritance
we receive from our biological parents
• Nervous system functioning
• Hormones—endocrine system
• Brain structure & function—the size and
shape of different brain areas & how these
different areas “work”
First, let’s review the function of
the nervous system…one of the
two communication systems
within the body
The nervous system is made up
of …
• Central nervous system (CNS)—the brain & the
spinal cord
• Peripheral nervous system (PNS)—everything
else. The PNS can be broken down into two subparts
– Skeletal, somatic nervous system—skeletal muscles for
voluntary movement
– Autonomic nervous system—non-skeletal muscles
found in organs, typically operate without voluntary
control
Autonomic nervous system
includes….
The CNS & PNS work together
in executing behavior…
e.g., information from our senses (PNS) are sent to
the brain (e.g., the “sound” of a teacher asking a
question in class) and our brain (CNS) sends
messages to tell our skeletal muscles (PNS) what
to do (e.g., raise your hand because you have
something to say!)
Messages are sent via…..
NEURONS!!!!
Neurons…
• …allow for communication within the
body.
• There are networks of neurons throughout
the body—somewhere in the vicinity of 100
billion neurons throughout the body
• No two neurons are exactly alike in size or
shape. They range in length from a
millimeter to several feet.
Neurons
• No two neurons are alike….
• ..but all have the same basic parts:
– Soma (cell body) –contains cell nucleus
– Dendrites—receive information from
other neurons
– Axon—transmits info from dendrites to
other neurons
– Terminal buttons—at the end of the
axon—their job is to transmit info to the
dendrites or cell body of next neuron
Neurons—Make sure you can
label the different parts on the
neuron on the next slide
(You can use your book if you need
help--& ask in class if you need more
help!)
Communication within neurons
is electrical
• Communication within neurons happens through
the process of conduction
• An electrical signal is sent down the length of the
axon. This electrical signal is called an “action
potential”
• Some axons are myelinated (i.e., covered with a
fatty tissue called the myelin sheath)—myelinated
axons allow for quicker transmission of the
electrical impulse.
Communication between neurons
is chemical
• When the electrical impulse reaches the terminal
buttons, they release chemicals called
neurotransmitters into the synapse.
• These neurotransmitters connect with receptor
sites (located mostly on the dendrites, but also
some on the soma) of nearby neurons. The
neurotransmitters “fit in” to these receptor sites
like locks into keys
Communication between neurons
is chemical
• In this “lock & key” fashion, neurotransmitters
unlock tiny channels at the receiving sites on
nearby neurons, and electrically charged atoms
enter the receiving neuron.
• These electrically charged atoms—through
altering the electrical charge of the receiving
neuron—either excite or inhibit its readiness to
fire an electrical impulse down it’s axon
Communication within neurons
is electrical
• Neurons fire when their electrical charge
reaches what is called the threshold of
excitation.
• When this threshold is reached, they send
an electrical charge or impulse down their
axons. This electrical impulse is called (as I
mentioned earlier) “an action potential.”
Communication between neurons
is chemical and within neurons is
electrical…
• Through binding with receptor cells,
neurotransmitters alter the likelihood of the
receiving neurons reaching the threshold of
excitation, thus they are either inhibitory
(make the firing of the receiving neuron
LESS likely) or excitatory (make the firing
of the receiving neuron MORE likely).
Neurotransmitters…
• …are chemicals that are released into the
synapse by neurons.
• These neurotransmitters are “taken back up”
into the terminal buttons of neurons through
the process of reuptake
Neurotransmitters…
• ..and the balance of neurotransmitters in the
body have been implicated in a number of
conditions that are very interesting to
psychologists, such as depression or
schizophrenia (a mental disorder in which
an individual loses touch with reality and
e.g., may hear voices or see things that
aren’t there—called hallucinations)
Psychotropic drugs
• (drugs used to treat psychological
conditions)
• …work through altering neurotransmitter
balances in the body
Psychotropic drugs
• Agonists mimic the neurotransmitter by binding to
the receptor sites just as the neurotransmitters do
and having the same effect on the receiving
neuron. Agonists are used when it is believed that
there is not enough neurotransmitter
• Antagonists BLOCK the neurotransmitter by
binding to the receptor sites without affecting the
receiving neuron in the same way. Because they
“fill” the receptor sites, the neurotransmitters can’t
bind to the neuron. Antagonists are used when it
is believed that there is TOO much of the
neurotransmitter in the body.
Psychotropic drugs
• When there is TOO LITTLE neurotransmitter
in the body, drugs may also help by blocking
reuptake and thus increasing the amount of
neurotransmitter that remains in the synapse
• Prozac is an example of this sort of drug.
Prozac falls in a class of drugs called SSRI’s
(Selective Serotonin Reuptake Inhibitor) and
by inhibiting reuptake of serotonin, they
increase the levels of this neurotransmitter in
the brain.
The two communication systems
for your body are:
• The nervous system (which we’ve just been
discussing) AND
• The endocrine system—Read the section in
your textbook on the endocrine system on
pp. 48-49 of your textbook
THE BRAIN
THE BRAIN
• The cerebral cortex is a higher-level brain
structure…it’s responsible for higher-level
cognitive processes
• The cerebral cortex covers the two hemispheres of
the brain with wrinkled folds (sort of like a
cauliflower)….these “wrinkles” increase the entire
surface area of the cortex.
• The cerebral cortex consists of 30 billion nerve
cells and around 300 trillion synaptic connections!
The cerebral cortex
• For convenience sake, each hemisphere of the
brain is often subdivided into four different
lobes—or four different geographic regions..
• The cerebral cortex provides many functions for
the body—some of these functions have been
“localized” (i.e., the particular part of the cortex
that carries the functions out have been identified)
but it is important to realize that multiple areas of
the brain work together for most complex human
behaviors.
Functions of the cerebral cortex
• Motor functions—the motor cortex is located at
the rear of the frontal lobe.
• Sensory functions—the sensory cortex is located
in the front of the parietal lobe (right behind the
motor cortex)
• Note that each hemisphere of the brain controls
and receives info from the OPPOSITE side of the
body. So the command for moving your left arm
originates from the motor cortex in your right
hemisphere.
Functions of the cerebral cortex
• Sensory functions (continued)
– Information from the optic nerve is sent to the
visual cortex located in the occipital lobe
– Information from the sensory organs in our ears
are sent to the auditory cortex located in the
temporal lobes
Functions of the cerebral cortex
• Associational functions—
– Our brain does lots of organizing and interpretation of
information. This organization and interpretation is
accomplished by association areas in the brain
– Association areas are believed to make up ¾ of the area
of the brain
– Association areas of the brain used for planning ahead
are believed to be located in the frontal lobes of the
brain
Functions of the cerebral cortex
• Motor functions
• Sensory functions
• Associational functions
• Language functions—Two important brain areas
for language are:
– Wernicke’s area—located in the left temporal lobe—
important for our understanding of language
– Broca’s area—located in the left frontal lobe—
important for spoken language
A mnemonic (memory) device that you
can use to remember some of the
locations of these functions…
• Frontal: forethought—thinking &
planning ahead (associational areas)
• Occipital: observing –vision (visual cortex)
• Temporal: twanging –sound (auditory
cortex)
• Parietal: prickling—sensation (sensory
cortex)