Transcript Neuroscience and Behavior (The Brain)

Neuroscience and
Behavior
(The Brain)
Ch. 2
Introduction
• Everything psychological is simultaneously
biological
• Your every idea, every mood, every urge is a
biological happening
• You think, feel, and act with your body
• Without your body, you are nobody
• Aristotle first thought the mind was in the
heart and not in the head *
Biological Psychologists
• A branch of psychology concerned with the
links between biology and behavior *
Neural Communications
• The building blocks of our body’s neural
information system are neurons
• Neuron- a nerve cell
• Each neuron consists of a cell body and its
branching fibers
• Dendrite(detect)- the bushy, branching
extensions of a neuron that receive messages
and conduct impulses toward the cell body *
Neural communications
• Axon(announce)- the extension of a neuron,
ending in branching terminal fibers, through
which messages pass to other neurons or to
muscles of glands
• Dendrites are short and axons can be up to
several feet in length *
Neural communications
• A neuron carrying orders to a leg muscle has a
cell body and axon on the scale of a basketball
attached to a rope 4 miles long
• Myelin sheath- a layer of fatty tissue segmentally
encasing the fibers of many neurons
– It enables vastly great transmission speed of neural
impulses as the impulse hops from one node to the
next
– A degeneration of the sheath can cause muscular
sclerosis
• Causes a slowing of all communication to muscles and the
eventual loss of muscle control
Neural communications
• Our brain is vastly more complex than a
computer, but not faster at executing simple
responses
• A neuron fires an impulse when it receives
signals from sense receptors stimulated by
pressure, heat, light, or by chemical messages
from neighboring neurons
• Action potential- a neural impulse- a brief
electrical charge that travels down an axon
Neural communications
• Neurons generate electricity from chemical
events
• Ions- electrically charged atoms
• The fluid interior of a resting axon has an
excess of negatively charged ions while the
fluid on the outside has more positively
charged ions
• This state is called resting potential
Neural communications
• The axon’s surface is selectively permeable
• This means that it is very selective about what it
allows in
• When a neuron fires, the first bit of the axon
opens its gates and the positively charged sodium
ions flood through the membrane channel
• This depolarizes that part of the axon causing the
axon’s next channel to open
• It leads to a chain reaction like dominoes falling
Neural communications
• During a resting pause called the refractory
period the neuron pumps the positively
charge sodium atoms back outside
• It can then fire again
• This electrochemical process can repeat up to
100 or even 1000 times a second
Neural communications
• Neurons can receive two types of signals from
other neurons
• Excitatory- like pushing a neuron’s accelerator
• Inhibitory- like pushing its brake
• If excitatory signals minus inhibitory signals
exceed a minimum intensity the combined signals
trigger an action potential
• This minimum intensity is called a threshold
• Threshold- the level of stimulation required to
trigger a neural impulse
Neural communications
• Increasing the stimulus above the threshold
will not increase the action potential’s
intensity
• The neuron’s action is an all-or-none response
• Neurons are like guns, either they fire or they
don’t
• Strong stimulus can trigger more neurons to
fire, and to fire more often
Neural communications
• Even under a microscope it is hard to see
where one neuron stops and the next starts
• There is a gap between the two neurons
• Synapse- the junction between the axon tip of
the sending neuron and the dendrite or cell
body of the receiving neuron
– The tiny gap at this junction is called the synaptic
gap or cleft
Neural communications
• When the action potential reaches the
knoblike terminals at an axon’s end, it triggers
the release of chemical messengers called
neurotransmitters
– When released by the sending neuron,
neurotransmitters travel across the synapse and
bind to receptor sites on the receiving neuron,
thereby influencing whether that neuron will
generate a neural impulse
Neural communications
• The neurotransmitter unlocks tiny channels a
the receiving site allowing ions to enter the
receiving neuron either exciting or inhibiting
the neuron to fire
• Excess neurotransmitters are reabsorbed by
the sending neuron in a process called
reuptake
– Many drugs increase the availability of selected
neurotransmitters by blocking their reuptake
Neural communications
• Acetylcholine- a neurotransmitter that, among
its functions, triggers muscle contraction
– Plays a role in learning and memory
– Is the messenger at every junction between a
motor neuron and skeletal muscle
– If ACh is blocked our muscles will not contract
• Endorphins- natural, opiatelike
neurotransmitters linked to pain control and
to pleasure
Neural communications
• Drugs can affect the production of
neurotransmitters
• Opiate drugs like heroin or morphine can
cause the brain to stop producing its own
natural opiates
• This would cause severe pain when there are
no drugs in the system
Neural communications
• Drugs can be agonists or antagonists
– Agonists- excite- it is similar enough to the
neurotransmitter to mimic its effects or that
blocks a neurotransmitter’s reuptake
– Antagonists- inhibit- can be a drug molecule that
inhibits a neurotransmitter’s release
The Nervous System
• Nervous system- the body’s speedy,
electrochemical communication system,
consisting of all the nerve cells of the
peripheral and central nervous systems
• Central nervous system- the brain and spinal
cord
• Peripheral nervous system- the sensory and
motor neurons that connect the central
nervous system to the rest of the body
The Nervous System
• Nerves- neural cables containing many axons
– Connect the central nervous system with muscles,
glands, and sense organs
• Sensory neurons(afferent neurons)- neurons that
carry incoming information from the sense
receptors to the central nervous system
• Interneurons- central nervous system neurons
that internally communicate and intervene
between the sensory inputs and motor neurons
• Motor neurons(efferent neurons)- neurons that
carry outgoing information from the central
nervous system to the muscles and glands
The Nervous System
• Our nervous system has a few million sensory
neurons, a few million motor neurons, and
billions and billions of interneurons
The peripheral nervous system
• The peripheral nervous system has two
components
– Somatic nervous system- controls the body’s
skeletal muscles
– Autonomic nervous system- controls the glands
and the muscles of the internal organs
• Can be consciously overridden but it usually operates
on its own
The peripheral nervous system
• The autonomic nervous system is broken up into
two parts
– Sympathetic nervous system- arouses the body,
mobilizing its energy in stressful situations
• If something alarms you, it will accelerate your heart rate,
slow your digestion, raise your blood sugar, dilate your
arteries, and cool you with perspiration
• Ready for action
– Parasympathetic nervous system- calms the body,
conserving its energy
• Reverses the changes made by the sympathetic system
Dating Game
• I will divide the class into groups of 6
• Each group member will take on the role as one
of the following neurotransmitters:
– Acetylcholine, Dopamine, Serotonin, Norepinephrine,
GABA, Glutamate
• Each member will research the following about
their neurotransmitter:
– What are your likes, what is your personality like,
what are things that you do not like or cause you
problems, and any other interesting things dealing
with your neurotransmitter
• Each member will take turns going around introducing
themselves to another person. Make sure to write down
things for each person you meet.
The central nervous system
• The central nervous system connects the
peripheral nervous system with the brain
• Reflexes- a simple, automatic, inborn response
to a sensory stimulus, such as the knee-jerk
response
– A headless warm body could still show reflexes
like the knee-jerk response
– Even if the spinal cord was severed below where it
meets the brain, the person would feel no
sensations but still show certain reflexes
The central nervous system
• Neural networks- interconnected neural cells
– With experience, networks can learn, as feedback
strengthens or inhibits connections that produce
certain results
– Practice of a certain skill can build neural networks
– Neurons will network with other nearby neurons
to allow for fast communication with each other
Studying he brain
• Lesion- tissue destruction- can be naturally or
experimentally caused
• EEG- an amplified recording of the waves of
electrical activity that sweep across the brain’s
surface- the waves are measured by electrodes
placed on the scalp
• CT scan- a series of x-ray photographs taken from
different angles and combined by computer into
a composite representation of a slice through the
body
Studying the brain
• PET scan- a visual display of brain activity that
detects where a radioactive form of glucose
goes while the brain performs a given task
• MRI- a technique that uses magnetic fields
and radio waves to produce computergenerated images that distinguish among
different types of soft tissue- allows us to see
structures within the brain
Lower level brain structures
• Brainstem- the oldest part and central core of
the brain, beginning where the spinal cord
swells as it enters the skull
– Responsible for automatic survival functions
• Medulla- the base of the brainstem that
controls heartbeat and breathing
– If the top of a cat’s brainstem is severed from the
rest of the brain above it, the animal will still
breathe, live, run, climb, and groom but it wont
purposefully run or climb to get food
Lower level brain structures
• The brainstem is the crossover point for the brain
– Where most nerves to and from each side of the brain
connect with the body’s opposite side
• Reticular formation- a nerve network in the
brainstem that plays an important role in
controlling arousal
– Electrically stimulating the reticular formation of a
sleeping cat almost instantly produced an awake, alert
animal
– Severe the same part and the cat immediately went
into a coma and never awoke
Lower level brain structures
• Thalamus- the brain’s sensory switchboard
– Located on top of the brainstem
– It directs messages to the sensory receiving areas in
the cortex and transmits replies to the cerebellum and
medulla
– Receives messages from all senses except smell
• Cerebellum- the “little brain”
– Attached to the rear of the brainstem
– It helps coordinate voluntary movement and balance
– If injured, you would have a hard time walking,
keeping your balance, and shaking hands
– Your movement would be jerky and exaggerated
Lower level brain structures
• These lower level functions all occur without
any conscious effort
• Is evidence that our brain processes most
information outside of our awareness
• Whether we are asleep or awake, our
brainstem manages its life-sustaining
functions allowing us to dream, think, talk, or
enjoy a memory
Lower level brain structures
• Limbic system- a doughnut-shaped system of
neural structures at the border of the
brainstem and cerebral hemispheres
– Associated with emotions such as fear and
aggression and drives such as those for food and
sex
– Includes the hippocampus, amygdala, and
hypothalamus
Quiz- 9/8
1. Draw a diagram of the nervous system
and peripheral nervous system. Make
sure to describe the function of each
part.
2. List and describe three methods for
studying the brain
3. What are the functions of the medulla,
reticular formation, and thalamus
Lower level brain structures
• Hippocampus- processes memory
– If injured, people become unable to form new
memories of facts and episodes
• Amygdala- two almond shaped neural clusters
that are components of the limbic system and are
linked to emotion
– Influence aggression and fear
– If lesioned, an ill tempered monkey becomes mellow
– If stimulated in one part a cat becomes very
aggressive and in another part it becomes terrified of
a small mouse *
Lower level brain structures
• Hypothalamus- a neural structure lying below
the thalamus
– It directs several maintenance activities like
eating, drinking, and body temperature
– Helps govern the endocrine system via the
pituitary gland and is linked to emotion
– Exerts control by triggering autonomic nervous
system activity
– When stimulated it can provide a pleasurable
reward
• Pleasure center or reward center*
The cerebral cortex
• Cerebral Cortex- the intricate fabric of
interconnected neural cells that covers the
cerebral hemispheres
• It is the body’s ultimate control and informationprocessing center
• It forms a thin surface layer on your cerebral
hemispheres
• The larger cortex of mammals offers increased
capacities for learning and thinking allowing them
to be more adaptable*
The cerebral cortex
• 80 percent of the brain’s weight lies in the left
and right cerebral hemispheres
• The hemispheres are filled with mostly axon
connections between the brain’s surface and its
other regions
• The cerebral cortex is about 1/8 of an inch thick
and contains 20 to 23 billion nerve cells
• Supporting the nerve cells are 9 times as many
glial cells
– Glial cells- cells in the nervous system that support,
nourish, and protect neurons*
The cerebral cortex
• Glial cells guide neural connections, provide
nutrients and insulating myelin, and mop up
ions and neurotransmitters
• They are often referred to as neural nannies
• The folds in the cerebral cortex greatly
increase the brain’s surface area
• If flattened, the brain’s surface would be
roughly the size of a large pizza
• In lower mammals the cortex is smoother*
The cerebral cortex
• Each brain hemisphere is divided into four regions or
lobes
• Frontal lobe- the portion of the cerebral cortex lying
just behind the forehead
– Involved in speaking and muscle movements and in
making plans and judgments
• Parietal Lobe- located at the top of the head and
toward the rear
– Includes the sensory cortex
• Occipital Lobe- located at the back of the head
– Includes the visual areas
• Temporal Lobe- located roughly above the ears
– Includes auditory areas, each of which receives auditory
information primarily from the opposite ear*
The cerebral cortex
The cerebral cortex
• A television would go dead with its power
cord cut
• Does this mean that the picture comes from
the cord?
• Our cortex’s are similar to this analogy
• It is difficult to localize brain functions
• Things like speaking, drawing, and shooting
pool involve many brain areas*
The cerebral cortex
• Simpler brain functions have been localized though
• By using electrical stimulation to the cortexes of dogs,
scientists have discovered that they could make
different limbs move
• Stimulation caused movement only when applied to an
arch-shaped region at the back of the frontal lobe
– Motor cortex- controls voluntary movement
– The motor cortex as been mapped out to show what parts
of the cortex control the different parts of the body
– This research is being used in trying to allow paralyzed
people to move a robotic limb*
The cerebral cortex
• There has also been a cortical area identified that
specializes in receiving information from the skin
senses and from the movement of body parts
• Sensory cortex- the area at the front of the parietal
lobes that registers and processes body sensations
• Stimulate a part of the cortex and a person may report
being touched on the shoulder
• The more sensitive a body region, the greater the area
of the sensory cortex devoted to it
• Our lips have a larger area on the cortex than our toes
• If we lose a limb, the region associated with that limb
will branch to receive sensory input from other limbs*
The cerebral cortex
• Other areas where the cortex receives input
from the other senses
– Visual cortex- located in the occipital lobe
– Auditory cortex- located in the temporal lobe*
The cerebral cortex
• Association Areas- areas of the cerebral cortex
that are not involved in primary motor or sensory
functions
– They are involved in higher mental functions such as
learning, remembering, thinking, and speaking
– Associate various sensory inputs with stored
memories
– If you stimulate these areas, there will be no
noticeable reaction
– This is where the falsehood of humans only using 10
percent of their brain came from *
The cerebral cortex
• The association areas interpret, integrate, and
act on information process by the sensory
areas
• Association areas in the frontal lobe enable us
to judge, plan, and process new memories
– people with damage to this region may be able to
bake a cake but cannot plan ahead to begin baking
the cake
– Phineas Gage*
Phineas Gage
Phineas Gage
Phineas Gage
The cerebral cortex
• Some parts of our parietal lobe are involved in
mathematical and spatial reasoning
• Parts of the temporal lobe enable us to recognize
faces
– If damaged you will be able to describe facial features
and to recognize someone’s gender and approximate
age, but be unable to identify the person
• Most of our complex mental functions are spread
throughout our brain- damage to one area wont
totally wipe out these functions *
The cerebral cortex
• Aphasia- impairment of language, usually
caused by left hemisphere damage either to
Broca’s area or to Wernicke’s area
– Some people with aphasia can speak clearly but
cannot read
– can read but cannot speak
– can write but not read or read but not write
– can read numbers but not letters
– can sing but not speak*
The cerebral cortex
• These puzzling discoveries can be explained with
our Broca and Wernicke areas
– Broca’s area- control language expression
•
•
•
•
Part of the frontal lobe
Usually in the left hemisphere
Directs the muscle movements involved in speech
Could not form words but could sing familiar songs and
comprehend speech
– Wernicke’s area- controls language reception
•
•
•
•
Involved in language comprehension and expression
In the left temporal lobe usually
Can speak meaningless words
Example pg. 82*
The cerebral cortex
• Aphasia to the Broca
– https://www.youtube.com/watch?v=f2IiMEbMnPM
– https://www.youtube.com/watch?v=6zNKz7YoUao
• Aphasia to the Wernicke
– https://www.youtube.com/watch?v=aVhYN7NTIKU
– https://www.youtube.com/watch?v=dKTdMV6cOZw
The cerebral cortex
• To sum it all up, the mind’s subsystems are
localized in particular brain regions, yet the brain
acts as a unified whole
• Moving your hand, recognizing faces, and
perceiving color all depend on specific neural
networks
• Complex functions such as language and learning
involve the coordination of many brain areas
• The brain uses specialization and integration*
The cerebral cortex
• Plasticity- the brain’s capacity for
modification, as evident in brain
reorganization following damage(especially in
children) and in experiments on the effects of
experience on brain development
– Most severed neurons will not regenerate
– Neural tissue can reorganize in response to
damage
– If blind, the sense of touch will invade the brain
area normally used for sight*
The cerebral cortex
• Our brain’s our most plastic when we are
young children
• Children are born with a surplus of neurons
• If an injury destroys one part of a child’s brain,
the brain will compensate by putting other
surplus areas to work
• A child can adapt if they lose half of their brain
much easier than an adult*
Half a brain video
• https://www.youtube.com/watch?v=2MKNsI5
CWoU
• https://www.youtube.com/watch?v=eK6gmZ
NdKNo
• https://www.youtube.com/watch?v=VaDlLD9
7CLM
Our divided brains
• For more than a century, evidence has shown
that the brain’s two sides serve differing
functions
• Accidents, strokes, and tumors in the left
hemisphere generally impair reading, writing,
speaking, arithmetic reasoning, and
understanding
• Lesions to the right side of the brain seem to
not have as much of an effect*
Our divided brains
• By the 1960s, the left hemisphere was
thought of as the dominant or major
hemisphere and the right as subordinate or
minor
• Through research, we have learned though
that the right hemisphere is not as limited as
we thought*
Our divided brains
• In 1961, two scientists speculated that epileptic
seizures were the result of abnormal brain
activity going back and forth from the two
hemispheres
• They then wondered whether they could reduce
the amount of seizures by cutting the
communication between the two hemispheres
• Corpus Callosum- the large band of neural fibers
connecting the two brain hemispheres and
carrying messages between them *
Our divided brains
• To stop the communication between the two
hemispheres the scientists decided to cut the
corpus callosum
• They did not feel this would be incapacitating for
the patient
• The result was that the seizures were all but
stopped
• Split brain- a condition in which the two
hemispheres of the brain are isolated by cutting
the connecting fibers between them *
Our divided brains
• Split brain patients were found to be normal
for the most part
• Their personalities and intellect was not
affected much
• Example of results on pg. 87 *
Our divided brains
• Some people that have had a split brain
operation deal with an unruly independent
left hand
• The left hand might unbutton a shirt while a
right hand buttoned it
• The left hand may put grocery store items
back on the shelf after the right hand put
them in the cart *
Our divided brains
• After a split brain operation its as if each
hemisphere was thinking on its own
• Split brain operations do leave people with
two independent brains
• When the two minds are at odds, the left
hemisphere seems to act as the brain’s press
agent, working to rationalize reactions it does
not understand
• Examples pg. 87 *
Our divided brains
• The left hemisphere is an interpreter that
instantly constructs theories to explain our
behavior
• The right hemisphere understands simple
requests and easily perceives objects
• With a split brain, both hemispheres can
comprehend and follow in instruction to copy
different figures with the left and right hands at
the same time
• What does it tell us about the function of the
hemispheres if it is thought that the left side of
our face is more expressive of emotions than the
right?*
Our divided brains
• Hemispherical specialization on pg. 88
• Right vs left handed- pg. 89 *
The Endocrine System
• Interconnected with the nervous system is the
second of the body’s communication systems,
the endocrine system
– The body’s “slow” chemical communication
system
– A set of glands that secrete hormones into the
bloodstream *
The Endocrine System
• Hormones- chemical messengers, mostly those
manufactured by the endocrine glands, that are
produced in one tissue and affect another
• When hormones act on the brain, they influence
our interest in sex, food, and aggression
• Some hormones are chemically identical to
neurotransmitters
• The messages sent by the endocrine system are
much slower than those sent by the nervous
system *
The Endocrine System
• Several seconds or more may elapse before the
bloodstream carries a hormone from an
endocrine gland to its target tissue
• The effects of the endocrine messages may take
longer to get to their intended destination but
their effects seem to outlast those of the neural
messages
• Hormones work to keep everything in balance
while we respond to stress, exertion, and our
own thoughts *
The Endocrine System
• In a moment of danger, the autonomic nervous
system orders the adrenal glands on top of the
kidneys to release epinephrine and
norepinephrine
– Also called adrenaline and noradrenaline
– Adrenal glands- help to arouse the body in times of
stress
– These hormones released help to increase heart rate,
blood pressure, and blood sugar providing us with a
surge of energy
– When the emergency passes, the hormones and the
feelings associated with them linger a while *
The Endocrine System
• The most influential endocrine system is the
pituitary gland
– Under the influence of the hypothalamus, the
pituitary regulates growth and controls other
endocrine glands
– It is a pea sized structure at the base of the brain
– It is considered a master gland
– The pituitary, under the brain’s influence, trigger
your sex organs to release sex hormones *
The Endocrine System
• Because the nervous system and endocrine
system work so closely, the lines between the
two are often blurred *