Chapter 6

Body and Behavior

Section 1

The Nervous System:

The Basic Structure

How the nervous system works

• Central nervous system (CNS)- the brain and spinal cord

• Spinal cord- nerves that run up and down the length of the back and transmit most messages between the body and brain

• Peripheral nervous system (PNS)- nerves branching beyond the spinal cord into the body

Neurons

• The long, thin cells of nerve tissue along which messages travel to and from the brain

• Transmission occurs whenever cells are stimulated past a minimum point and emit a signal.

• Either fires or does not fire

Parts of a neuron

• Dendrites- short, thin fibers that protrude from the cell body– Receive impulses or messages and send

them to the cell body

• Axon- carries the impulses from the cell body to the axon terminals

• Axon terminals- release neurotransmitters to stimulate dendrites of the next neuron

Parts of a neuron

• Myelin sheath- insulates and protects the axon for some neurons– speeds the transmission of impulses– In cases of multiple sclerosis, the myelin

sheath is gone.

The Neuron Connection

• Synapse- the gap that exists between individual nerve cells

• Neurotransmitters- the chemicals released by neurons which determine the rate at which other neurons fire

• Examples of neurotransmitters– Norepinephrine- is involved with memory and

learning– Endorphine- inhibits pain

Neuron Activity

• Intensity of neurons depends on how many other neurons are acting on it

• Afferent neurons- sensory neurons that relay messages from the sense organs to the brain (eyes, ears, nose, skin)

• Efferent neurons- motor neurons that send messages from the brain to the glands and muscles

• Interneurons- process signals, connecting only to other neurons, not to sensors or muscles

Voluntary and Involuntary activities

• Somatic nervous system (SNS)- the part of the peripheral nervous system that controls voluntary movement of skeletal muscles

• Autonomic nervous system (ANS)- the part of the peripheral nervous system that controls internal biological functions

Autonomic Nervous System

• Sympathetic nervous system– Prepares the body for dealing with

emergencies or strenuous activity

• Parasympathetic– Works to conserve energy and to enhance the

body’s ability to recover from strenuous activity

Section 2

Studying the Brain

Three parts of the Brain

• Hindbrain- a part of the brain located at the rear base of the skull that is involved in the basic processes of life.

• Midbrain- a small part of the brain above the pons that arouses the brain, integrates sensory information, and relays it upward

• Forebrain- a part of the brain that covers the brain’s central core, responsible for sensory and motor control and the processing of thinking and language

Hindbrain

• Includes the following parts:• Cerebellum

– Helps control posture, balance and voluntary movements

• Medulla– Controls breathing, heart rate, and reflexes

• Pons– Bridge between the spinal cord and brain– Produces chemicals the body needs for sleep

Forebrain

• Includes the following parts:• Thalamus

– Integrates sensory input– “relay station” for all info that travels to and

from the cortex

• Hypothalamus– Controls functions of hunger, thirst, and

sexual behavior– Controls the bodies reaction to temperature

Forebrain

• Includes the following parts:

• Cerebral cortex– Outer layer of the forebrain

• Cerebrum– Inner layer of the forebrain– Gives you the ability to learn and store

complex and abstract information

Forebrain

• Limbic system– Includes various structures that regulate our

emotions and motivations– Amygdala- controls violent emotions like rage

or fear– Hippocampus- is important for the formation

of memories

The Lobes of the Brain

• Corpus callosum- a band of fibers that joins the two sides or hemispheres of the cerebrum

• Lobes- are the different regions into which the cerebral cortex is divided

Lobes of the Brain

• Occipital lobe- visual signals are sent

• Pariental lobe- concerned with various information from the senses

• Temporal lobe- concerned with hearing, memory, emotion, and speaking

• Frontal lobe- concerned with organization, planning, and creative thinking

Left and Right Hemispheres

• Right and left sides of the brain complement each other

• Left hemisphere of the brain controls the right side of the body– Mathematical ability, where speech is located

• Right hemisphere of the brain controls the left side of the body– Controls visual and spatial relations– Perceptual tasks

How Psychologists Study the Brain

• Recording– Electroencephalograph (EEG)- is a machine

used to record electrical activity of large portions of the brain

– Overall electrical activity can be measured and the rhythms of the brain differ depending on whether a person is awake, drowsy, or asleep

How Psychologists Study the Brain

• Stimulation– Electrodes may be used to set off the firing of

neurons as well as record it– Has been used with terminal cancer patients

to relieve their pain– Used to control violent emotional behavior

Images

• Computerized axial tomography (CT)– An imaging technique used to study the brain

to pinpoint injuries and brain deterioration– Radiation is absorbed depending on the

density of the brain tissue– Computers measure the amount of radiation

absorbed and then transformed into 3-D images

Images

• Positron Emission Tomography (PET)– Is an imaging technique used to see which

brain areas are being activated while performing tasks

– Injects radioactive solution into the blood and measuring the amount of radiation absorbed by the blood cells

– Show activity in different areas of the brain when a person is thinking, speaking, or looking at objects

Images

• Magnetic Resonance Imaging (MRI)– A measuring technique used to study brain

structure and activity– Combines the features of CT and PET scans

• fMRI- observes both the functions of different structures of the brain and which structures participate in specific functions

Section 3

The Endocrine System

The Endocrine Glands

• Endocrine system- a chemical communication system, using hormones, by which messages are sent through the bloodstream.

• Hormones- chemical substances that carry messages through the body in blood

The Endocrine Glands

• Hormones have effects on your behavior

• Hormones can also influence your moods and drives

• Duct glands– Release their contents through small holes on

the surface of the body• Sweat glands, tear glands, salivary glands

Pituitary Gland

• Is the center of control of the endocrine system that secretes a large number of hormones

• Controls growth and reproduction including ovulation and lactation

Thyroid Gland

• Produces thyroxine

• Stimulates certain chemical reactions that are important for all tissues of the body

• Hyperthyroidism- too much thyroxine which causes overactivity

• Hypothyroidism- too little thyroxine makes people feel lazy

Adrenal Glands

• Become active when angry or frightened

• Release epinephrene and norepinephrine which cause heartbeat and breathing to increase

• Secrete cortical steroids which help muscles develop

Sex Glands

• Testes– Testosterone (male sex hormone)

• Important in physical development• Helps decide sex of the fetus

• Ovaries– Produce estrogen and progesterone

• Important in the development of female sex characteristics

• Vary throughout the menstrual cycle

Hormones v.s. Neurotransmitters

• Both work to affect the nervous system

• When a chemical is used as a neurotransmitter:– It is released right beside the cell that it is to

excite or inhibit

• When a chemical is used as a hormone:– It is released into the blood, which defuses

into the body

Section 4

Heredity and Environment

Heredity and Environment

• Heredity- the genetic transmission of characteristics from parents to their offspring

• Inherited factors and environmental conditions always act together in different ways

Nature versus Nurture

• Nature refers to characteristics that a person inherits– Family, culture, education, individual

experiences

• Genes are the basic units of heredity– Can be reproduced and passed from

generation to generation – For example, musical talent

Twin Studies

• Identical twins- twins who come from one fertilized egg; twins having the same heredity

• Genes- the basic building blocks of heredity

• Fraternal twins- twins who come from two different eggs fertilized by two different sperm

Twin Studies

• Twins growing up in the same house share the same environment as well as the same genes

• Twins growing up in different environments have common behaviors despite different social, cultural, or economic backgrounds

Sources:

• Kasschau, Richard, A. Understanding Psychology. McGraw-Hill, Glencoe, New York, New York, 2008.