brains, bodies, and behavior

Brains, Bodies, and Behavior

Brains, Bodies, and Behavior

• The Neuron Is the Building Block of the Nervous System• Our Brains Control Our Thinking, Feeling, and Behavior• Psychologists Study the Brain Using Many Different Methods• Putting It All Together: The Nervous System and the Endocrine System

The Neuron Is the Building Block of the Nervous System


• Learning Objectives1. Describe the structure and functions of the neuron 2. Draw a diagram of the pathways of communication within and between

neurons.3. List three of the major neurotransmitters and describe their functions.


Major Parts of a Neuron

Soma (Cell Body)contains the cell’s nucleuskeeps the cell alive

Dendritecollects information from other cellssends the information to the soma

Axontransmits information away from the cell body, toward other neurons or muscles and glands


• Specialized parts of an axon– myelin sheath – layer of fatty tissue surrounding the axon

• insulates the axon• speeds the transmission of the electrical signal

– terminal button – branching toward the end of an axon

• Image of a motor neuron, with dendrite, axon and cell body labeled and described

Neurons Communicate Using Electricity and Chemicals

• Communication is electrical, taking the form of a charge called an action potential

• Communication is chemical, via neurotransmitters which travel across the gap between two neurons

Within a Neuron Between Neurons


Resting Potentialthe interior of a neuron is negatively charged relative to the area outside the neuron

Action Potentialwhen an electrical signal is passed from the dendrites, the neuron’s charge changes from negative to positive

Refractory Periodfollowing an action potential, a neuron cannot fire again for a brief time


• The myelin sheath wraps around the axon, but also leaves small gaps called the Nodes of Ranvier.

• The action potential jumps from node to node as it travels down the axon

Neurotransmitters: The Body’s Chemical Messengers

• areas where the terminal buttons at the end of an axon nearly touch another neuron’s dendritessynapse

• chemicals that relay signals across the synapses between neuronsneurotransmitter

• neurotransmitters in the synapse are reabsorbed into the transmitting terminal buttonsreuptake


action potential reaches terminal

button

neurotransmitter release

neurotransmitters travel across

synapse

neurotransmitters bind to receptor sites on dendrite

neurotransmitter reuptake

• When the nerve impulse reaches the terminal button, it triggers the release of neuro-transmitters into the synapse.

• The neuro-transmitters fit into receptors on the receiving dendrites in the manner of a lock and key


Excitatory neurotransmitters – increase the likelihood that a neuron will fire

Inhibitory neurotransmitters – decrease the likelihood that a neuron will fire

• Drug that mimics or enhances the influence of a given neurotransmitter

– e.g., cocaine is a dopamine agonist

• Drug that blocks or inhibits the activity of a given neurotransmitter

– e.g., curare is an acetylcholine antagonist

Agonist Antagonist


• Key Takeaways– The Central Nervous System (CNS) is the collection of neurons that make up the

brain and the spinal cord. – The Peripheral Nervous System (PNS) is the collection of neurons that link the

CNS to our skin, muscles, and glands.– Neurons are specialized cells, found in the nervous system, which transmit

information. Neurons contain a dendrite, a soma, and an axon.


• Key Takeaways, continued– Some axons are covered with a fatty substance known as the myelin sheath

which surrounds the axon acting as an insulator, allowing faster transmission of the electrical signal

– The dendrite is a treelike extension that receives information from other neurons and transmits electrical stimulation to the soma.

– The axon is an elongated fiber that transfers information from the soma to the terminal buttons.


• Key Takeaways, continued– Neurotransmitters relay information chemically from the terminal buttons and

across the synapses to the receiving dendrites using a type of lock and key system.

– The many different neurotransmitters work together to influence cognition, memory, and behavior.

– Agonists are drugs that mimic the actions of neurotransmitters, whereas antagonists are drugs that block the action of neurotransmitters.

Our Brains Control Our Thinking, Feeling, and Behavior


Learning Objectives:1. Describe the structures and function of the “old brain,” and its influence on

behavior.2. Explain the structure of the cerebral cortex (its hemispheres and lobes) and the

function of each area of the cortex.3. Define the concepts of brain plasticity, neurogenesis, and brain lateralization.


• The “Old Brain”– Includes the brain structures nearest the spinal cord– Regulates basic survival functions, such as breathing, moving, resting, and

feeding– Contributes to experiences of emotion

• In addition to the old brain, humans have a large and highly developed outer brain layer known as the cerebral cortex.

• The cortex provides humans with excellent memory, outstanding cognitive skills, and the ability to experience complex emotions.

The Old Brain: Wired For Survival

Brainstemincludes the medulla,

pons, and reticular formation

cerebellumcoordinates

voluntary movement

thalamusfilters sensory information

from spinal cord; relays information to cortex

Limbic Systemincludes the amygdala,

hippocampus, and hypothalamus


The BrainstemMedullanearest the spinal cordcontrols heart rate and breathing

Ponshelps control movement; plays a major role in balance and walking

Reticular Formationfilters stimuli from spinal cordplays a role in eating, walking, sexual activity, and sleeping


The Limbic System

Amygdalaregulates our perceptions of and reactions to aggression and fear

Hippocampushelps store information in long-term memory

Hypothalamuslinks the nervous system to the endocrine system via the pituitary glandhelps regulate body temperature, thirst, hunger, and sexual motivation

The Cerebral Cortex Creates Consciousness and Thinking

• cerebral cortex – the outer, bark-like layer of the human brain that allows us to use language, acquire complex skills, create tools, and live in social groups

– contralateral control – the left side of the cortex responds to and controls the right side of the body, and vice versa

• The brain is divided into two hemispheres -- left and right.

• Each hemisphere has four lobes -- temporal, frontal, occipital and parietal.


Frontal Lobesthinking, planning,

memory, and judgment; contain motor cortex

Parietal Lobesprocess touch

information; contain somatosensory cortex

Temporal Lobeshearing and

language; contain auditory cortex

Occipital Lobesprocess visual

information and contain visual cortex


• In addition to its motor and sensory areas, the cortex contains association areas.• In the association areas, sensory and motor information is combined and related to

our stored knowledge.

The Brain is Flexible: Neuroplasticity

• neuroplasticity – the brain’s ability to change its structure and function in response to experience or damage

• neurogenesis – the forming of new neurons

The Left and Right Hemispheres

• Brain Lateralization– The left and right hemispheres are specialized to perform different functions.– The corpus callosum is a band of fibers connecting the two hemispheres.– Sperry’s research on split brain patients contributed to our understanding of

brain lateralization.

The Left and Right Hemispheres

Corpus Callosumconnects left and right hemispheresLeft Hemisphere

-- language-- mathematics-- judging time and rhythm--sequencing complex movements

Right Hemisphere-- perceptual skills-- recognizing objects and faces-- recognizing patterns and melodies-- drawing pictures


• Key Takeaways– The old brain, including the brainstem, medulla, pons, reticular formation,

thalamus, cerebellum, amygdala, hypothalamus and hippocampus regulates basic survival functions such as breathing, moving, resting, feeding, emotions and memory.

– The cerebral cortex, made up of billions of neurons and glial cells, is divided into the right and left hemispheres and into four lobes.

– The frontal lobes are primarily responsible for thinking, planning, memory and judgment. The parietal lobes are primarily responsible for bodily sensations and touch. The temporal lobes are primarily responsible for hearing and language. The occipital lobes are primarily responsible for vision. Other areas of the cortex act as association areas, responsible for integrating information.


• Key Takeaways, continued– The brain changes as a function of experience and potential damage in a process

known as plasticity. The brain can generate new neurons through neurogenesis.– The motor cortex controls voluntary movements. Body parts requiring the most

control and dexterity take up the most space on the motor cortex.– The sensory cortex receives and processes bodily sensations. Body parts that are

the most sensitive occupy the greatest amount of space on the sensory cortex. – The left cerebral hemisphere is primarily responsible for language and speech in

most people, whereas the right hemisphere specializes in spatial and perceptual skills, visualization, and the ability to recognize patterns, faces, and melodies.


• Key Takeaways, continued– The severing of the corpus callosum, which connects the two hemispheres,

creates a “split brain patient,” with the effect of creating two separate minds operating in one person.

– Studies with split-brain patients as research participants have been used to study brain lateralization.

– Neuroplasticity allows the brain to adapt and change as a function of experience or damage.

Psychologists Study the Brain Using Many Different Methods


• Learning Objective:1. Compare and contrast the techniques that scientists use to view and

understand brain structures and functions.


• Cadaver Approach– The most direct approach to

understanding the structure of the brain

Advantagebrain can be fully studied

Disadvantage the brain is no longer active

Lesions Provide a Picture of What is Missing

• Lesions– In living humans, lesions are areas of brain damage resulting from accidents,

strokes, gunshots, or other injuries.– Lesions may also be created intentionally in animals.– Lesions allow scientists to observe the loss of function that results.

Lesions Provide a Picture of What is Missing

• Areas in the frontal lobes of Phineas Gage were damaged when a metal rod was blasted through it.

• Gage’s personality, emotions, and moral reasoning were influenced.

• The accident helped scientists understand the role of the frontal lobes in these processes.

http://upload.wikimedia.org/wikipedia/commons/2/28/Phineas_gage_-_1868_skull_diagram.jpg

Recording Electrical Activity in the Brain

• In animals, detectors can be placed in the brain to study the electrical activity caused by the firing of specific neurons.

• In living humans, the electrical activity of the brain’s neurons can be studied using scalp electrodes – this is electroencephalography, or EEG.

Recording Electrical Activity in the Brain

• Useful in understanding brain abnormalities such as epilepsy

• Participants can move around during recordings

• Allows changes to brain activity to be tracked very quickly

• Does not provide a clear picture of the brain’s structure

Advantages of EEG Disadvantage of EEG

Peeking Inside the Brain: Neuroimaging

• Functional Magnetic Resonance Imaging (fMRI)– a type of brain scan that uses a magnetic field to create images of the activity in

each brain area– detects the blood flow in each brain region– currently the most common method of learning about brain structure


Advantages of fMRIprovides detailed pictures of brain structuresnon-invasive

Disadvantage of fMRIscanners are expensive


• Transcranial Magnetic Stimulation (TMS)– procedure in which magnetic pulses are applied to a living person’s brain to

temporarily and safely deactivate a small brain area– allows cause-and-effect conclusions about the influence of brain structures on

thought and behavior


• Key Takeaways– Studying the brains of cadavers can lead to discoveries about brain structure,

but are limited due to the fact that the brain is no longer active.– Lesion studies are informative about the effects of different brain regions.– Electrophysiological recording may be used in animals to directly measure brain

activity.


• Key Takeaways, continued– Measures of electrical activity in the brain, such as electroencephalography

(EEG) are used to assess brainwave patterns and activity.– Functional Magnetic Resonance Imaging (fMRI) measures blood flow in the brain

during different activities, providing information about the activity of neurons and thus the functions of brain regions.

– Transcranial Magnetic Stimulation (TMS) is used to temporarily and safely deactivate a small brain region, with the goal of testing the causal effects of the deactivation on behavior.

The Nervous System and The Endocrine System


• Learning Objectives:1. Summarize the primary functions of the CNS and of the subsystems of the PNS. 2. Explain how the electrical components of the nervous system and the chemical

components of the endocrine system work together to influence behavior.

Electrical Control of Behavior: The Nervous System

• Nerves– bundles of interconnected neurons

that fire in synchrony

sensory (afferent) neurons

carry information from the sensory receptors

motor (efferent) neurons

transmit information to the muscles and glands

interneuronscommunicate

information among neurons


CentralNervous System

Brain Spinal Cord


• Reflexes – involuntary, nearly instantaneous movements in response to stimuli

• Triggered when powerful sensory information allows spinal cord interneurons to send a message back through the motor neurons without relaying the information to the brain


Peripheral Nervous System connects CNS to sense receptors, glands, and muscles

Autonomic Nervous Systemgoverns bodies internal activities

Sympathetic Nervous System

Parasympathetic Nervous

System

Somatic Nervous Systemcontrols external aspects of the body


• Prepares the body for action, especially in response to stress

• Activates the organs and the glands in the endocrine system

• Calms the body• Slows heart rate and respiration• Allows the body to recover from action

Sympathetic Nervous System Parasympathetic Nervous System

The Body’s Chemicals Help Control Behavior: The Endocrine System

• Endocrine System– glands – cell groups– hormones – chemicals circulating

in the body to regulate emotion and behavior

• The endocrine system interacts with the nervous system.

hormonessecreteglands


• Pituitary Gland– small gland in the center of the

brain– the “master gland”– secretes hormones that influence

responses to pain – secretes hormones that signal the

ovaries and testes to make sex hormones

– controls ovulation and the menstrual cycle in women

• Adrenal Glands– located on top of the kidneys– produce hormones that regulate

body’s salt and water balance– involved in metabolism, the

immune system, and sexual development and function

– secrete the hormones epinephrine and norepinephrine when we are excited or threatened

• Epinephrine and norepinephrine stimulate the sympathetic nervous system


pancreassecretes hormones to

supply body with energy

pineal glandsecretes melatonin to regulate sleep cycle


• Secrete Testosterone– Testosterone regulates body

changes related to sexual development.

– Testosterone levels are positively associated with aggressive behavior in both men and women.

• Secrete Estrogen and Progesterone– Estrogen is involved in the

development of female sexual features.

– Both hormones are involved in pregnancy and the regulation of the menstrual cycle.

Testes (Male Sex Glands) Ovaries (Female Sex Glands)


• Key Takeaways– The body uses both electrical and chemical systems to create homeostasis.– The CNS is made up of bundles of nerves that carry messages to and from the

PNS– The Peripheral Nervous System is comprised of the Autonomic Nervous System

(ANS) and the Peripheral Nervous System (PNS). The ANS is further divided into the sympathetic (activating) and parasympathetic (calming) nervous systems. These divisions are activated by glands and organs in the endocrine system.

– Specific nerves, including sensory neurons, motor neurons, and interneurons, each have specific functions.


• Key Takeaways, continued– The spinal cord may bypass the brain by responding rapidly using reflexes.– The pituitary gland is a master gland affecting many other glands.– Hormones produced by the pituitary and adrenal glands regulate growth, stress,

sexual functions, and chemical balance in the body.– The adrenal glands produce epinephrine and norepinephrine, the hormones

responsible for our reactions to stress.– The sex hormones, testosterone, estrogen, and progesterone play an important

role in sex differences

brains, bodies, and behavior

Documents

nervous systemthe neuron

building block

axon neurotransmitters

behaviorthe neuron

motor neuron

nervous systemour brains

collection of neurons

endocrine systemthe