the biological perspective

PSYCHOLOGYPSYCHOLOGYAN EXPLORATIONAN EXPLORATION

PSYCHOLOGYPSYCHOLOGYAN EXPLORATIONAN EXPLORATION

CHAPTER

Second EditionSecond Edition

Psychology: An Exploration, Second EditionSaundra K. Ciccarelli • J. Noland White

the biological perspective

2


why study the nervous system and the glands?How could we possibly understand any of our behavior, thoughts, or actions without knowing something about the incredible organs that allow us to act, think, and react? If we can understand how the brain, the nerves, and the glands interact to control feelings, thoughts, and behavior, we can begin to truly understandthe complex organism called a human being.


Learning Objectives

• LO 2.1What are the nervous system, neurons and nerves?• LO 2.2How neurons use neurotransmitters to communicate• LO 2.3How brain and spinal cord interact • LO 2.4Somatic and autonomic nervous systems • LO 2.5Hormones and Behavior• LO 2.6How psychologists study the brain and how it works• LO 2.7Structures and functions of the bottom part of the brain• LO 2.8Structures that control emotion, learning, memory, motivati

on• LO 2.9Parts of cortex controlling senses and body movement• LO 2.10Areas of the cortex involved in higher forms of thought• LO 2.11Left and Right brain differences


Overview of Nervous System

• Nervous system – Network of cells carrying information to

and from all parts of the body

• Neuroscience – Emphasis on structure and function of

neurons, nerves, and nervous tissue – Branch of life sciences

LO 2.1 What are the nervous system, neurons and nerves?


Structure of the Neuron

• Biological psychology (behavioral neuroscience)– Branch of neuroscience – Focuses on the biological bases of

psychological processes, behavior, and learning



Figure 2.1 An Overview of the Nervous System



• Neuron– Specialized cell in the nervous system– Sends and receives nervous system

messages

• Parts of the Neuron– Dendrites

Branch-like structures that receive messages from other neurons




• Parts of the Neuron– Soma

Cell body of the neuron Responsible for maintaining the life of the

cell

– Axon Long tube-like structure Carries the neural message to other cells



Figure 2.2 The Structure of the NeuronThe electronmicrograph on the left shows myelinated axons.


Other Types of Brain Cells

• Glial Cells – Provide support for the neurons to grow

on– Deliver nutrients to neurons– Remove waste products and dead

neurons– Types include oligodendrocytes and

Schwann cells– Produce myelin to coat axons



Myelin Sheath

• Fatty substances produced by glial cells • Coats the axons insulate, speed neural

impulse• Oligodendrocytes produce myelin for

brain and spinal cord• Schwann cells produce myelin for rest

of body• Multiple sclerosis

– Causes destruction of myelin sheath



Generating the Message: Neural Impulse

• Neurons are electrically charged with ions– Ions are located inside and outside of

the cell– More negatively charged inside the cell,

more positively charged outside the cell– Difference in charges creates an

electrical potential




• Resting potential – State of neuron when not firing a neural

impulse– Channels for sodium not open

• Action potential – Release of the neural impulse– Consists of reversal of electrical charge

within the axon




• All-or-none – Neuron either fires completely or does

not fire at all



Figure 2.3 The Neural Impulse Action PotentialIn the graph below, voltage readings are shown at a given place on the neuron over a period of 20 or 30 milliseconds (thousandths of a second). At first the cell is resting; it then reaches threshold and an action potential is triggered. After a brief hyperpolarization period, the cell returns to its resting potential.


Figure 2.3 (continued) The Neural Impulse Action PotentialIn the graph below, voltage readings are shown at a given place on the neuron over a period of 20 or 30 milliseconds(thousandths of a second). At first the cell is resting; it then reaches threshold and an action potential is triggered. After a brief hyperpolarization period, the cell returns to its resting potential.


Sending the Message to Other Cells

• Axon terminals – Branches at the end of the axon– Synaptic knob

Rounded areas on the end of axon terminals

Synaptic vesicles – Sack-like structures inside the synaptic

knob – Contain chemicals called

neurotransmitters

LO 2.2 Neuron communication



• Axon terminals – Neurotransmitters, when released,

affect neighboring cells



This electromicrograph shows a motor neuron making contact with muscle fibers.



• Synapse/synaptic gap – Fluid-filled space between end axon

terminals of one cell and surface of the next cell

• Receptor sites – Ion channels, proteins on dendrite

surface– Shaped to accept specific

neurotransmitter



Figure 2.4 The SynapseThe nerve impulse reaches the synaptic knobs, triggering the release of neurotransmitters from the synaptic vesicles. The molecules of neurotransmitter cross the synaptic gap to fit into the receptor sites that fit the shape of the molecule, opening the ion channel and allowing sodium ions to rush in.


Neuron Communication

• Neural cells can be turned either on or off– Excitatory synapses

Cause receiving cell to fire

– Inhibitory synapses Cause receiving cell to stop firing



Neuron Communication

• Chemical substances affect neural communication

• Agonists – Mimic or enhance the effects of a

neurotransmitter on the receptor sites

• Antagonists – Block or reduce a cell’s response to the

action of other neurotransmitters



Table 2.1 Some Neurotransmitters and Their Functions


Cleaning up the Synapse

• Reuptake – Neurotransmitters are taken back into

the synaptic vesicles– Acetylcholine does not go through

reuptake Needs to be available for quick muscle

activity– Reuptake too slow for process

Is instead broken down in the synapse by enzymatic degradation



Central Nervous System

• Part of the nervous system consisting of the brain and spinal cord– Brain

Interprets information from senses

– Spinal cord Long bundle of neurons Carries messages to and from the body to

the brain Also responsible for very fast, lifesaving

reflexes

LO 2.3 Brain and spinal cord


The Reflex Arc: Three Types of Neurons

• The reflex arc forms a connection between a sensory, a motor and an interneuron

• Sensory neuron – Carries messages from the senses to

spinal cord– Also called afferent neuron



This electronmicrograph shows a stem cell in the process of becoming a neuron.



• Motor neuron – Carries messages from spinal cord to

muscles and glands– Also called efferent neuron




• Interneuron– Found in spinal cord and brain– Receives information from sensory

neurons – Sends commands to muscles through

the motor neurons– Make up the bulk of the neurons in the

brain



Figure 2.6 The Spinal Cord ReflexThe pain from the burning heat of the candle flame stimulates the afferent nerve fibers, which carry the message up to the interneurons in the middle of the spinal cord. The interneurons then send a message out by means of the efferent nerve fibers, causing the hand to jerk away from the flame.


Neuroplasticity

• Is the ability to change both the structure and function of cell involved in trauma– Implanted nerve fibers from damaged

area– Damaged spinal nerves grow through

fiber “tunnels” • Possibility of transplanting stem cells to

repair damaged tissue being explored



Peripheral Nervous System

• Consists of nerves and neurons not contained in the brain and spinal cord– Nerves run through the organs and

extremities of the body – Divided into:

Somatic nervous system Autonomic nervous system

LO 2.4 Somatic and autonomic nervous systems


Figure 2.7 The Peripheral Nervous System


Somatic Nervous System

• Division of PNS • Consists of nerves carrying information:

– From the senses to CNS – From the CNS to voluntary muscles of

the body



These young soccer players are using their senses and voluntary muscles controlled by the somatic division of the peripheral nervous system. What part of the autonomic nervous system are these girls also using at this time?


Somatic Nervous System

• Division of PNS – Sensory pathway

Afferent neurons coming from sensory organs

– Motor pathway Efferent neurons coming from the CNS to

the voluntary muscles



Autonomic Nervous System

• Division of PNS • Functions automatically

– Sympathetic division (fight-or-flight system) Reacts to stressful events and bodily

arousal



Figure 2.8 Functions of the Parasympathetic and Sympathetic Divisions of the Nervous System


Autonomic Nervous System

• Division of PNS • Functions automatically

– Parasympathetic division Restores body to normal functioning after

arousal Responsible for the day-to-day

functioning of the organs and glands



Snowboarder Shaun White of the U.S.A. 2010 Olympics Team won the gold medal in the halfpipe competition in Vancouver. What part of the autonomic nervous system is likely to be working as Shaun flies through the air, as in this picture?


The Endocrine Glands

• Are glands that secrete chemicals called hormones directly into the bloodstream

• Endocrine communication is slower than synaptic communication– Hormones

Chemicals released into the bloodstream by endocrine glands

LO 2.5 How hormones interact with the nervous system and affect behavior



• Pituitary gland – Located in the brain– Secretes human growth hormone– Influences all other hormone-secreting

glands (also known as the master gland)



Figure 2.9 The Endocrine GlandsThe endocrine glands secrete hormones directly into the bloodstream, which carries them to organs in the body, such as the heart, pancreas, and sex organs.



• Pineal gland – Located near the base of the cerebrum – Secretes melatonin

• Thyroid gland – Found in the neck – Regulates growth and metabolism

• Pancreas – Controls the levels of sugar in the blood– Secretes insulin and glucagons



When the pancreas does not secrete enough insulin, the result is diabetes. Many diabetic people must give themselves insulin shots to supply enough of the hormone.



• Gonads – Sex glands – Secrete hormones that regulate sexual

behavior and reproduction Ovaries - female gonads Testes - male gonads




• Adrenal glands – Located on top of each kidney – Secrete over 30 different hormones

Deals with stress Regulates salt intake Provides secondary source of sex

hormones during adolescence



Looking Inside the Living Brain

• Lesioning studies– Deep lesioning

Insertion of a thin, insulated wire into the brain

Electrical current destroys brain cells at tip of wire

– Shallow Lesioning Cells are destroyed on the surface of the

brain

LO 2.6 Study of the brain


Looking Inside the Living Brain

• Electrical stimulation of brain (ESB)– Mild electrical current passed through

probe– Causes neurons to react as if had

received a message



Electrical Stimulation of Brain (ESB)

• Deep Brain Stimulation (DSB)– Electrodes inserted in brain are attached

to a pacemaker-like device– Helpful in treatment of Parkinson’s

disease



Electrical Stimulation of Brain (ESB)

• transcranial Direct Current Stimulation (tDCS)– Uses scalp electrodes to pass very low

amplitude direct currents to the brain – Changes the excitability of cortical

neurons directly below the electrodes



A researcher at the National Institute of Mental Health in Bethesda, Maryland, uses an electromagnet as part of an experimental treatment for depression. This treatment, called Repetitive Transcranial Magnetic Stimulation (rTMS), excites neurons in the brain, triggering activity.


Mapping Brain Structure

• Computed Tomography (CT) – Multiple X-rays of brain– Mapping with computer assistance– Can show stroke damage, tumors,

injuries, abnormal brain structure

• Magnetic Resonance Imaging (MRI)– More detail than CT scan– Uses radio waves and magnetic fields to

produce detailed images



Figure 2.10 Mapping Brain StructureFig 2.10a CT scan from an 8-year-old girl with a skull fracture (indicated by the red arrow); Fig 2.10b same CT scan depicting the brain and swelling associated with the head injury.


Figure 2.10 (continued) Mapping Brain StructureContrast the brain detail of Fig 2.10b with the MRI scan in Fig 2.10c (different, adult individual). Note the scans are in the horizontal plane, separating the brain into upper and lower portions.


Figure 2.10 (continued) Mapping Brain StructureFig 2.10d uses the same MRI data to provide an estimate of what the left external surface of the brain looks like. Fig 2.10a, b, & c images created with OsiriX software; 2.10d cortical reconstruction was performed with the Freesurfer image analysis suite. CT and MRI data courtesy of N. White.


Mapping Brain Structure

• Other techniques with MRI as basis:– MRI spectroscopy

Allows researchers to estimate concentration of chemicals and neurotransmitters in the brain

– Diffusion Tensor Imaging (DTI) Measure connectivity in brain by imaging

white matter tracts



Mapping Brain Function

• Electroencephalogram (EEG)– Electrical activity of brain is amplified

and output is displayed via computer– Output forms waves that reveal: stages

of sleep, seizures, presence of tumors– Event Related Potentials (ERPS)

Measures brain response to stimulus events

Allows for study of different stages of cognitive processing



Figure 2.11 Mapping Brain FunctionVarious methods for mapping brain function. An EEG record is shown in 2.11a



• Positron Emission Tomography (PET)– Person is injected with radioactive

glucose – Metabolism of glucose measured

• Single Photon Emission Computed Tomography (SPECT)– Similar to PET – Uses radioactive tracer to examine brain

blood flow



Figure 2.11 (continued) Mapping Brain FunctionVarious methods for mapping brain function. A PET scan image in 2.11b, and an image from an fMRI study in 2.11c.



• Functional Magnetic Resonance Imaging (fMRI)– Computer tracks changes in oxygen

levels of blood



The Brain Stem

• Medulla – First large swelling at top of spinal

column – Responsible for life-sustaining

functions such as breathing, swallowing, and heart rate

LO 2.7 Structures of the bottom part of brain


The Brain Stem

• Pons – Larger swelling above the medulla – Connects top of brain to bottom – Involved in sleep, dreaming, left–right

body coordination, and arousal



Figure 2.12 The Major Structures of the Human Brain


The Brain Stem

• Reticular formation (RF) – Runs through the middle of the medulla

and pons – Responsible for selective attention,

ignoring repetitive stimuli



The Brain Stem

• Cerebellum – Controls and coordinates involuntary,

rapid, fine motor movement.– Maintains posture, muscle co-ordination,

balance



This pitcher must count on his cerebellum to help him balance and coordinate the many fine motor commands that allow him to pitch the baseball accurately and swiftly. What other kinds of professions depend heavily on the activity of the cerebellum?


Structures Under the Cortex

• Limbic system– Brain structures located under the

cortex – Involved in learning, emotion, memory,

and motivation– Thalamus

Relays sensory information from the lower part of the brain to areas of cortex

Processes some sensory information

LO 2.8 Structures controlling emotion, learning, memory, and motivation



• Limbic system– Hypothalamus

Regulates body temperature, thirst, hunger, sleeping and waking, sexual activity, emotions

Controls pituitary gland



This young woman’s thirst is regulated by her hypothalamus.



• Limbic system– Hippocampus

Curved structure located within each temporal lobe

Responsible for the formation of long-term memories, storage of memory for location of objects




• Limbic system– Amygdala

Located near the hippocampus Responsible for fear responses and

memory of fear




• Limbic system– Cingulate Cortex

Important role in emotional and cognitive processing

Implicated in several psychological disorders such as ADHD, schizophrenia



Figure 2.13 The Limbic System


Cortex

• Outermost covering of the brain• Consists of densely packed neurons• Responsible for higher thought

processes and interpretation of sensory input– Corticalization

Wrinkling of the cortex Allows the large area of cortical cells to

exist in the small space inside the skull

LO 2.9 Parts of cortex controlling senses and movement


Cerebral Hemispheres

• Are the two sections of the cortex on the left and right sides of the brain.– Corpus callosum

Thick band of neurons connecting right and left cerebral hemispheres.



Figure 2.14 The Lobes of the Brain: Occipital, Parietal, Temporal, and Frontal


Four Lobes of the Brain

• Occipital lobes – Visual center of brain

Primary visual cortex – Processes visual information from the

eyes Visual association cortex

– Identifies, interprets visual information




• Parietal lobes – Contains centers for touch, taste, and

temperature sensations Somatosensory cortex

– Processes information from skin and internal body receptors for touch, temperature, body position, and possibly taste




• Temporal lobes – Hearing, meaningful speech– Primary auditory cortex

Processes auditory information from the ears

– Auditory association cortex Identifies, makes sense of auditory

information




• Frontal lobes – Higher mental processes, decision

making, production of fluent speech– Motor cortex

Sends motor commands to muscles



Figure 2.15 The Motor and Somatosensory CortexThe motor cortex in the frontal lobe controls the voluntary muscles of the body. Cells at the top of the motor cortex control muscles at the bottom of the body, whereas cells at the bottom of the motor cortex control muscles at the top of the body. Body parts are drawn larger or smaller according to the number of cortical cells devoted to that body part. For example, the hand has many small muscles and requires a larger area of cortical cells to control it. The somatosensory cortex, located in the parietal lobe just behind the motor cortex, is organized in much the same manner and receives information about the sense of touch and body position.


Figure 2.12 The Major Structures of the Human Brain


Association Areas of Cortex

• Are areas within each lobe of the cortex • Responsible for:

– Coordination and interpretation of information

– Higher mental processing

LO 2.10 Parts of cortex responsible for higher thought



• Broca’s Aphasia – Results from damage to Broca’s area – Usually in left frontal lobe – Causes affected person to be unable to

speak fluently Mispronounces words, speaks haltingly




• Wenicke’s Aphasia– Left temporal lobe damage – Speech is fluent but nonsensical

• Unilateral Spatial Neglect – Result of damage to the parietal lobe

association areas on one side of the cortex, usually the right side

– Person ignores information from opposite side of body or visual field



As this woman brushes the right side of her hair, is she really “seeing” the left side? If she has spatial neglect, the answer is “no.” While her eyes work just fine, her damaged right hemisphere refuses to notice the left side of her visual field.


Split Brain Research

• Robert Sperry (1968)– Demonstrated left and right

hemispheres of the brain specialize in different activities and functions

– Corpus callosum severed in patients to contain epileptic seizures

– Messages are sent to only one side of the brain Two hemispheres cannot coordinate

information

LO 2.11 Left side and right side of brain


Figure 2.16 The Split-Brain ExperimentRoger Sperry created this experiment to demonstrate the specialization of the left and right hemispheres of the brain.


Table 2.2 Specialization of the Two Hemispheres


Understanding ADHD

• Developmental disorder involving behavioral and cognitive aspects– Inattention, impulsivity, and

hyperactivity

• Some aspects of attention may be normal with ADHD (Nigg, 2010)



Understanding ADHD

• Problem areas for individuals with ADHD:– Vigilance– Staying on task– Maintaining effort – Self-control


the biological perspective

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