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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 computer-generated 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 information-processing 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=2MKNsI5CWoU
• https://www.youtube.com/watch?v=eK6gmZNdKNo
• https://www.youtube.com/watch?v=VaDlLD97CLM
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 *
