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Ch. 2 The Biological Basis of Behavior and Ch.3 Nature vs. Nurture
Link: Unit Two Charts and Diagrams
#1: History of, Biopsych Research Methods, Biopsych Tools
Introduction Statement: As technology has improved, scientists have used a wide range of
techniques to learn about brain and neural function
I. Greek philosophers and physicians linked the mind with the brain.
A. Hippocrates (460-377 B.C.) said that emotions, thought and mental health arise from the brain (Plato agreed
427-347 B.C.).
B. Galen (circa 130-200 A.D.) thought that fluids of the brain in ventricles were responsible for sensations,
reasoning and judgment, memory and movement.
II. Phrenology
A. Although Franz Gall (1758-1828) and Johann Spurzheim (1776-1832) incorrectly related bumps and
depressions on the surface of the skull with personality traits and moral character, phrenology encouraged others to
seek empirical evidence for brain localization.
III. Studying patients with brain damage linked loss of structure with loss of function.
A. Phineas Gage was the level-headed, calm foreman of a railroad crew (1848) until an explosion hurled a
tamping iron through his head. After the injury severed the connections between his limbic system and frontal
cortex, Gage became volatile. His lesions (destruction of tissue) where the limbic system is connected to the
frontal lobes related frontal lobes with mediation and control of emotional behavior.
B. Paul Broca (1824-1880) performed an autopsy on the brain of a patient named Leborgne (a.k.a. Tan) who had
lost the capacity for speech with no paralysis of the articulatory tract and no loss of verbal comprehension or
intelligence. Tan’s brain showed deterioration of part of the frontal lobe of the left cerebral hemisphere as did the
brains of several similar cases relating destruction of "Broca’s area" to expressive aphasia (1861). Carl Wernicke
(1848-1905) similarly found a second brain area involved in processing language in the temporal lobe of the left
cerebral hemisphere.
C. Gunshot wounds, tumors, "strokes" (e.g. a blood clot obstructs an arteriole in the brain blocking supply of
oxygen and nutrients to region, causing that region to die), Alzheimer’s disease, Korsakoff’s syndrome, etc.
enabled further mapping of the brain.
IV. Producing lesions at specific brain sites (also called ablation) enabled systematic study of loss of function resulting
from surgical removal, severing of neural connections, or destruction by chemical or electrical applications.
V. Examination of neural tissue led to understanding of the neuron as the unit of structure and function of the nervous
system. Santiago Ramon y Cajal (1852-1934) perfected a selective silver staining technique developed by Camillo Golgi
(1843-1926) to examine single neurons. Cajal described the structure of a neuron and noted a small space (synapse)
between adjacent neurons.
VI. Direct electrical stimulation of the brain tests the results of stimulating specific sites.
A. Wilder Penfield (1952) used a fine wire electrode to localize the origin of seizures in a patient. Stimulating
different cortical areas such as the back of the frontal cortex at particular sites caused body movement for different
body parts enabling mapping of the motor cortex, etc.
B. Walter Hess (1955) inserted electrodes more deeply into the brain relating start/stop functions with specific
brain structures. An example is the "start eating and stop eating" functions associated with areas of the
hypothalamus.
VII. EEG (Electroencephalogram)
A. An EEG is an amplified tracing of the activity of a region of the brain produced when electrodes positioned
over the scalp transmit signals about the brain’s electrical activity ("brain waves") to an electroencephalograph
machine. The amplified tracings are referred to as evoked potentials when the recorded change in voltage is the
result of a response to a specific stimulus presented to the subject. EEGs have been used to study the brain during
states of arousal such as sleeping and dreaming to detect abnormalities (such as deafness and visual disorders in
infants), and to study cognition.
VIII. Imaging Techniques: in widespread use, have enabled neuroscientists to observe the mind as it functions.
A. CAT scans (also called CT)--computerized axial tomography
1. Creates a computerized image of x-rays passed through various angles of the brain showing twodimensional "slices" that can be arranged to show the extent of a lesion
2. Procedure may involve injection of a contrast dye, but involves shorter period of scanning than MRI
and can be used with patients who have pacemakers or metallic implants
B. MRI--magnetic resonance imaging
1. Magnetic field causes usually random spin of hydrogen nuclei in water of cells to orient in single
direction. Pulses of radio waves jar the hydrogen nuclei which emit faint radio frequency signals when
they rebound that depend upon the density of the tissue. The computer constructs images based on
varying signals that is more detailed than CAT or PET scans, involves no contrast dye, and can be
produced for any plane of view.
2. Functional MRI or fMRI may soon provide more detailed information than PET scans capitalizing on
the ability of MRI scanners to detect an increase in oxygen that occurs in an area of heightened neuronal
activity.
C. PET scans--positron emission tomography. When neurons are active, an automatic increase in blood flow to
the active region of the brain brings more oxygen and glucose necessary for respiration. Blood flow changes are
used to create brain images when tracers (such as radioactively-tagged water) injected into the blood of the subject
emit particles called positrons which are converted into signals detected by the PET scanner. The concentration of
labeled substances taken up by brain tissue (revealed in colored computer graphics) depends on the amount of
metabolic activity in the imaged brain region. Tracks complex series of interactions in different brain areas
associated with specific mental processes.
IX. Other advances in technology have enabled neuroscientists to learn more about the relationship of neurological
function to behavior.
A. BEAM--brain electrical activity mapping Feeds EEG information from numerous recording sites into a
computer which constructs an image of the brain showing areas with different gradations of voltage in different
colors or shades to make more accurate diagnoses of brain tumors, epilepsy and learning disorders
B. MEG--magnetoencephalography and SQUID--superconducting quantum interference device Based on the
concept that whenever an electrical current is present there is an accompanying magnetic field, MEG detects
neural activity too brief to be detected by PET or MRI. This technique has been used to locate seizure-producing
regions in epileptic patients.
C. PRONG--parallel recording of neural groups . Electrodes that can measure many individual neurons in close
proximity have uncovered information about communication among neurons in a region.
D. SPECT--single-photon emission computerized tomography
Tracks cerebral blood flow as indicator of neural activity in specific brain regions during performance of various
tasks.
#2 : Neural Anatomy, Neural Communication, Action Potential, Neurotransmitters,
Drugs.
Introduction Statement: The entire basis for biopsychology, and subsequently Human Behavior,
is the neuron
I. The neuron or nerve cell is adapted for receiving and sending signals.
A. Three major regions of the neuron enable the cell to communicate with other cells.
1. The cell body (a.k.a. cyton or soma) contains cytoplasm and the nucleus which directs synthesis of such substances as
neurotransmitters.
2. The dendrites are branching tubular processes capable of receiving information.
3. The axon emerges from the soma as a single conducting fiber (longer than a dendrite) which branches and ends in tips
called terminal buttons (a.k.a. axon terminals, synaptic knobs or end feet). Neurotransmitters are stored in structures of the
terminal buttons called synaptic vesicles.
4. The axon may be covered by an insulating myelin sheath (made of specialized cells such as oligodendrocytes or
Schwann cells categorized as glial cells). Spaces between segments of myelin are called nodes of Ranvier.
B. Dozens of neurotransmitters have been identified that have a variety of chemical structures and perform
different functions.
1. Acetylcholine (ACh) causes contraction of skeletal muscles, helps regulate
heart muscles and also transmits messages between the brain and spinal cord. Interference and/or depletion of ACh is
associated with Alzheimer’s disease and myasthenia gravis.
2. The amino acids Glutamate and Aspartate stimulate receptors associated with learning and memory.
3. The amino acids Glycine and Gamma-Aminobutyric Acid (GABA) inhibit firing
of neurons. Benzodiazepine (Valium) and anticonvulsant drugs increase activity of GABA. Huntington’s disease is
associated with insufficient GABA-producing neurons in parts of the brain involved in coordination of movement.
4. Dopamine and Norepinephrine are catecholamines. Dopamine stimulates the hypothalamus to synthesize hormones.
Depletion of dopamine in the substantia nigra of the brain is associated with Parkinson’s disease.
5. Serotonin is associated with sexual activity, concentration and attention, moods and emotions.
6. Opioid peptides such as enkephalin and Endorphins are often considered the
brain’s own pain killers. (These are considered neuromodulators rather than neurotransmitters when they are produced in
other than the presynaptic neuron.)
II. The nature of the neural impulse is electrical. A very thin wire with a recording electrode inserted into a neuron
would record a series of very short uniform bursts of activity on a voltmeter because a neuron either "fires" or it
doesn’t "fire." ("All-or-nothing principle")
A. An impulse along the axon is axonal transmission.
1. The neuron at rest is more negative inside the cell membrane relative to
outside of the membrane. This resting neural membrane potential is about -70mV.
2. The resting potential results from the selective permeability of the membrane, the presence of electrically charged
particles called ions near the inside and outside surfaces of the membrane and resulting concentration and electrical
gradients. The sodium-potassium pump and blocking of ionic channels by calcium ions help maintain the resting potential.
3. When sufficiently stimulated (to threshold) a net flow of sodium ions into the cell occurs (along with a movement of
potassium ions out ). The potential rapidly reverses its polarity to typically +40mV very briefly. This brief change in
potential is called the action potential. This neural impulse travels down the length of the axon to the axon terminals.
4. The more intense a stimulus, the more frequently a neuron fires.
5. When the axon is myelinated, conduction speed is increased since depolarization occurs at the nodes of Ranvier. This is
called saltatory conduction.
6. A brief period of time, called the refractory period, follows the polarization changes during which the neuron is resistant
to a retriggering of an action potential.
III. Neurons signal by transmitting chemical messages to adjacent neurons, gland cells or muscle cells
A. Synaptic Transmission
1. Tiny gaps between neurons are called synaptic clefts. A particular terminal button of an axon, the synaptic cleft itself,
and the receiving portion of another neuron, gland cell or muscle cell together constitute the synapse.
2. When a neuron is sufficiently excited, voltage changes along the axon trigger the release of neurotransmitter molecules
from synaptic vesicles into the synaptic cleft.
3. A signal is transmitted from one neuron to the next when neurotransmitter molecules from the presynaptic neuron bind to
receptor sites (molecules) of the postsynaptic neuron much like a "lock and key" and stimulate the postsynaptic neuron to
fire (excitatory).
4. If the binding of the neurotransmitter to the postsynaptic receptor site
prevents or lessens the likelihood of the firing of the neuron, the effect is called inhibitory.
5. Excitation by a neural impulse can cause a muscle to contract or a gland to secrete.
IV. Reflexes and Neurons:
A. The simplest form of behavior, called a reflex, involves impulse conduction over a few neurons. The path is called
a reflex arc.
1. Sensory or afferent neurons transmit impulses from sensory receptors to the spinal cord or brain.
2. Interneurons, located entirely within the brain and spinal cord, intervene between sensory and motor neurons.
3. Motor or efferent neurons transmit impulse from sensory or interneurons to muscle cells that contract or gland cells
that secrete. The muscle and gland cells are called effectors.
4. Examples of reflexes include the pupillary reflex, knee jerk (patellar) reflex and blinking reflex.
#3 : Organization of the Nervous System
Introduction Statement: The Nervous System is Composed of Several Smaller Systems
I. Patterns of behavior are generally related to the functioning of structures of neural tissue or regions within the
brain rather than single or small groups of neurons. Neural tissue can be categorized in a variety of ways.
A. Appearance by shade/color of neural tissue
1. Gray Matter: is composed of neural cell bodies which may be mixed with capillaries. A large number of cell bodies
grouped together constitute a nucleus (within the central nervous system) or ganglion (in the peripheral nervous system).
2. White Matter: is composed of myelinated fibers. A large collection of myelinated axons constitutes a fiber pathway, or
tract (within the central nervous system), or nerve (within the peripheral nervous system).
3. Reticular Matter: is composed of cell bodies and axons mixed together giving a netlike appearance.
B. Description by location in the organism with respect to three axes.
1. From the back or dorsal portion to the belly or ventral portion. With respect to the human brain, superior is synonymous
with dorsal and inferior is synonymous with ventral.
2. From the head or anterior portion to the tail or posterior portion.
3. From the midline or medial portion to the side or lateral portion.
II. General divisions of the nervous system are anatomical and physiological.
A. The peripheral nervous system lies outside the midline portion of the nervous system carrying sensory
information to and motor information away from the central nervous system via spinal and cranial nerves.
1. One subdivision is the Somatic (Voluntary) Nervous System whose motor neurons innervate skeletal muscle.
2. The other subdivision is the Autonomic (Involuntary) Nervous System whose motor neurons innervate glands or
smooth or cardiac muscle.
a. Autonomic fibers emerge from the central nervous system and synapse with a second neuron. All synapses and cell
bodies in an autonomic nerve are at about the same location causing a bulge in the nerve called an autonomic ganglion.
b. The autonomic nervous system is subdivided into the antagonistic sympathetic and parasympathetic nervous systems.
b1: Sympathetic stimulation results in responses that help the body deal with stressful events. (SEE BELOW)
dilation of pupils
dilation of bronchi
acceleration of heart rate
acceleration of breathing rate
release of glucose from liver
inhibition of digestive functions
secretion of adrenalin from adrenal glands
inhibition of secretion of tear glands
b2:. Parasympathetic stimulation results in maintenance of homeostasis, digestive processes and calming following
sympathetic stimulation (SEE BELOW)
return to normal pupil size
normal bladder contractions
return to normal breathing rate
stimulation of tear glands
return to normal heart rate
stimulation of digestive functions
(salivation, peristalsis, enzyme secretion)
The Parasympathetic and Sympathetic Nervous Systems
B. The central nervous system consists of the spinal cord and the brain. (No correlation exists between brain size
and intelligence.)
1. The spinal cord, protected by membranes called meninges and the spinal column of bony vertebrae, starts at the base of
the back and extends upward to the base of the skull where it joins the brain.
a. Sensory fibers enter dorsally and motor fibers exit ventrally.
b. The cord itself is an H-shaped area of gray cell bodies surrounded by transverse, ascending and descending white
myelinated fibers.
c. The cord itself is composed mainly of interneurons and glial cells which are bathed by cerebrospinal fluid produced by
the glial cells.
2. The brain that has the consistency of soft-serve yogurt or semi-soft cheese, covered by protective membranes (dura,
arachnoid and pia mater collectively called the meninges) and housed in the skull, is studied from different approaches.
a. The Comparative Approach describes the brain’s evolution from more primitive organisms reasoning that new types of
behavior developed as each new layer evolved (correlating behavior and structure). According to one comparative view (the
Triune Brain model), the human brain has three major divisions that are overlapping layers.
a.1. The R-complex or Reptilian Brain roughly corresponds to the central core or brainstem (which usually is said to
include the medulla, pons and cerebellum). This "brain" is associated with maintaining homeostasis and instinctive
behaviors.
a.2. The Old Mammalian Brain roughly corresponds to the limbic system (which usually is said to include the septum,
hippocampus, the amygdala and the cingulate cortex), the hypothalamus and the thalamus, believed to b e important in
controlling affective/emotional behavior, some aspects of memory and vision.
a.3. The New Mammalian Brain or Neocortex, synonymous with the cerebral cortex, is associated with higher functions of
judgment, decision making, abstract thought, foresight, hindsight and insight, language and computing.
b. The Developmental Approach describes changes in structure and relates that to changes in function during the
development of an individual, and looks at the immature brain as a simplified model of the adult brain.
b.1. The embryonic spinal brain, across-brain, midbrain and between-brain give rise to the medulla oblongata, pons,
cerebellum, pineal body, hypothalamus and thalamus. Behaviorists call this the Brainstem.
b.2. The embryonic endbrain (also called forebrain) gives rise to the neocortex, basal ganglia, limbic system, and olfactory
bulb.
#4: Localization of function of the human brain
Introduction Statement: Multiple representations of information can be located within different areas of the
human brain, yet specific regions of the brain seem most critical in handling particular functions. This localization
of structure and function has been identified for numerous regions.
I. Areas below the neocortex are called subcortical areas.
A. The Medulla Oblongata lies immediately anterior to the spinal cord.
1. Where ascending and descending tracts of many fibers cross resulting in contralateral control
2. Site of nuclei of cranial nerves
3. Regulates heart rate and force of contraction
4. Regulates distribution of blood flow
5. Sets the pace of respiratory movements
6. Controls vomiting
7. Sensory and motor nuclei of five cranial nerves
B. The Pons lies immediately anterior to the medulla.
1. Ascending and descending tracts and nuclei of cranial nerves
2. Portion of reticular formation or ascending reticular activating system in pons is critical for EEG arousal
3. "Bridge" to cerebral hemispheres from medulla
4. "Bridge" between cerebral cortex and cerebellum
C. The Cerebellum is dorsal to the medulla and the pons.
1. Represents 1/8 the mass of the brain
2. Cerebellum coordinates motor function based upon the integration of motion and positional information from the inner
ear and individual muscles
3. Does not initiate muscle movement
4. Helps maintain balance and posture
D. The midbrain lies anterior to the pons.
1. Ascending and descending tracts and nuclei of cranial nerves
2. Involved in control of eye movement
3. Reflexive responses during vision
4. Involuntary control of muscle tone
5. Portion of reticular formation important in sleep-wake cycle
E. The thalamus lies anterior to the midbrain.
1. Relays for sensory pathways carrying visual, auditory and somatosensory
information to appropriate regions of the cerebral cortex (neocortex)
2. Contains pineal gland that secretes melatonin
3. Some nuclei are involved in emotion
F. The hypothalamus lies underneath the thalamus.
1. Controls autonomic functions such as body temperature and heart rate via control of sympathetic and parasympathetic
centers in the medulla
2. Sets appetitive drives (such as thirst, hunger, sexual desire) and behaviors
3. Sets emotional states with the limbic system
4. Integrates with endocrine system by secretion of peptide hormones that regulate the secretion of tropic hormones from
the anterior pituitary
5. Also produces ADH and oxytocin which are stored in and released from the posterior pituitary.
G. The limbic system consists of a number of structures sheathing the periphery of the brainstem. These include the
septum, amygdala and hippocampus. (Functionally, nuclei of the hypothalamus and thalamus interact with parts of
the limbic system and thus are often considered part of the limbic system.) The limbic system is focused on emotional
states and related behavioral drives and provides a link between the intellectual functions of the cerebral cortex and
the autonomic functions of the brain stem.
1. The septum may be associated with rageful behavior and hypersensitivity.
2. The amygdala may be associated with feeding, fighting and other behaviors involved in self-preservation as well as
facilitating formation of emotion-laden memories.
3. The hippocampus is important in storage of long-term memories and involved in aspects of learning.
II. The convoluted neocortex contains about 10 billion of our 100 billion nerve cells, accounts for approximately
80% of the volume of our brain, and is responsible for "higher functions" such as thought and planning.
A. Convolutions increase the surface area of the brain and provide a means of mapping regions.
1. Gyri (rolls) form the folding out portion of the neocortex.
2. Sulci are valleys in the convolutions.
3. Fissures are deeper than sulci extending to ventricles or cavities in the brain.
B. Lobes are four large regions of the cerebral cortex of each of the two hemispheres.
1. The left and right frontal lobes are anterior to the central sulcus and supe-rior to the lateral sulcus.
2. The left and right temporal lobes are inferior to the central sulcus.
3. The left and right parietal lobes are posterior to the central sulcus, anterior to the parietal-occipital fissure and superior
to the lateral sulcus.
4. The left and right occipital lobes are posterior to the parietal-occipital fissure.
C. Regions in each of the lobes receive information related to sensations and process the information.
1. The occipital lobes process visual information
2. The somatosensory region is the anterior strip of both parietal lobes where information regarding stimulation of various
body parts is received
3. The motor cortex is located in the posterior area of the frontal lobes just anterior to the somatosensory cortex. The motor
cortex is concerned with integration of activities performed by skeletal muscles and initiates movements.
4. The auditory cortex is partially buried within the lateral sulcus in the tempo ral lobes. Sensations of smell and taste are
processed anteriorly in the temporal lobes.
5. Multiple representations of information can be illustrated with respect to speech. While visual speech is represented in
the occipital cortex, auditory speech is represented in the temporal cortex and motor speech is represented in the frontal
cortex.
6. Association areas are not specifically localized involving integration of information from other areas with respect to
thinking, memory, learning, etc.
#5: Lateralization of Function of the Human Brain (Split Brain)
Introduction Statement: Although similarly located regions in both cerebral hemispheres generally have
similar functions, differences or lateralization of function has been shown to exist.
I. Different techniques have yielded information regarding brain lateralization.
A. Electrical stimulation of the brain can be accomplished with an alert patient so that accurate reports can be made.
B. PET scans reveal information regarding brain activity during different tasks
C. Deficits resulting from cerebral vascular accidents ("strokes"), injury or lesioning
D. Brain wave patterns
E. Split brain (corpus callosum transection or commisurotomy) patients
F. Drugs that affect activity of half of the brain (sodium amytal in carotid artery)
G. Dichotic listening
II. Left hemisphere specialization
A. The left hemisphere is specialized for speech and language function
1. Receptive auditory language function is localized in a region of the left temporal lobe called Wernicke’s area. Damage
to this area results in Wernicke’s aphasia characterized by the outward form of normal speech without coherence
resulting from the inability to comprehend written and spoken language.
2. Expressive language function is localized in a region of the left frontal lobe called Broca’s area. Damage to this area
results in Broca’s aphasia characterized by inability to convert ideas, perceptions and intended messages into smoothly
articulated patterns of speech with appropriate syntax.
3. Almost all right handed people and about 2/3 left-handed people show this specialization of function in their left
hemispheres
B. Contralateral (opposite-side) representation
1. Left somatosensory cortex registers tactile (touch) sensations from the right side of the body.
2. Left motor cortex initiates movements in the right side of the body.
3. Left temporal cortex receives auditory information from the right ear.
4. Left occipital cortex processes visual information from the right visual field from both retinas.
C. Some psychologists characterize the left hemisphere as predisposed to deal with auditory materials,
particularistic elements, focal representation.
III. Right hemisphere specialization
A. The right hemisphere is specialized for spatial functions.
1. Right hemisphere plays role in pattern recognition, processing visual configurations.
2. Right hemisphere plays dominant role in making fine discrimination among colors.
3. Patients with right hemisphere lesions may exhibit left side neglect.
B. The right hemisphere is specialized for musical functions.
1. Variation in intonation--right temporal damage can result in monotone speech.
2. Discrimination and memory of musical passages is right hemisphere function.
C. Contralateral representation
1. Right somatosensory cortex registers tactile (touch) sensations from the left side of the body
2. Right motor cortex initiates movements in the left side of the body
3. Right temporal cortex receives auditory information from the left ear
4. Right occipital cortex processes visual information from the left visual field from both retinas
D. Some psychologists characterize the right hemisphere as predisposed to deal with visual materials, totalities or
organized wholes (Gestalt), diffuse representation.
#6: The Endocrine System
Introduction Statement: Integration and control is achieved through interaction of the nervous system with the
endocrine system of glands that secrete chemical messengers called hormones which is its primary function.
I. Comparison of endocrine and nervous system regulation
A. Endocrine gland cells secrete hormones directly into the blood stream whereas neurons transmit signals over a
neural network, in general.
B. Endocrine transport may take minutes to hours whereas in nervous control the process may take a fraction of a
second to minutes.
C. Endocrine effects are typically long-lasting whereas neural effects are short-lived.
D. Both hormones and neurotransmitters interact with specific receptors on or in the target cells.
E. Overlap between systems is evidenced by neurotransmitters which are chemically identical to hormones (such as
noradrenaline), neurons which are neurosecretory cells that release signal molecules intro the bloodstream and
neurosecretory cells in endocrine glands (such as the adrenal medulla) which transmit signals through the blood and
to neurons.
II. Hormones are the signal molecules of the endocrine system.
A. Hormones are of three general chemical types: steroids, peptides or proteins, and amino acid derivatives.
B. Hormones are active in very small amounts.
C. Hormones themselves are under tight negative feedback control.
D. Hormones are rapidly degraded in the body.
1. Steroids, peptides and proteins are broken down by the liver.
2. Amino acid derivatives are broken down by enzymes in the blood.
III. As in the brain, endocrine glands are specialized in function.
A. The pineal gland lies in the thalamic region of the brain.
1. Produces melatonin which is involved in the regulation of circadian rhythms
2. Controlled by light-dark cycles
3. Associated with seasonal affective disorder
B. The hypothalamus anterior to the pituitary gland has endocrine gland properties.
1. Secretes at least nine hormones that stimulate (such as thyrotropin-releasing hormone and gonadotropin-releasing
hormone) or inhibit (such as somatotropin) the secretion of hormones by the anterior pituitary
2. Secretes ADH (antidiuretic hormone) which controls water excretion and oxytocin which stimulates uterine contractions
and milk ejection. Both hormones are transmitted to the posterior lobes of the pituitary through nerve fibers.
3. Negative feedback systems link the hypothalamus and pituitary with the thyroid, adrenal cortex and gonads maintaining
homeostasis and permitting response to changing conditions.
C. The pituitary gland is located at the base of the brain in the geometric center of the skull inferior to the
hypothalamus.
1. Once considered the master gland because it is the source of hormones that stimulate reproductive organs, the adrenal
cortex, thyroid.
2. Hypothalamus stimulates or inhibits production of pituitary hormones
3. Produces growth hormone also called somatotropin which stimulates growth of bone, inhibits oxidation of glucose,
promotes breakdown of fatty acids and is controlled by the hypothalamus.
4. Produces prolactin which stimulates milk production and secretion con trolled by hypothalamus.
5. Produces TSH also called thyroid-stimulating hormone and thyrotropin regulated by hypothalamus and concentration
of thyroxine in blood.
6. Produces ACTH also called adrenocorticotropic hormone which stimulates the adrenal cortex to secrete cortisol and
other steroids regulated by hypothalamus and cortisol in blood.
7. Produces FSH also called follicle-stimulating hormone that stimulates egg production or sperm production regulated by
hypothalamus and estrogen in blood.
8. Produces LH also called luteinizing hormone which stimulates ovulation and corpus luteum in female and cells of
testes in male regulated by progesterone or testosterone in blood and hypothalamus.
9. Releases oxytocin.
10. Releases ADH, vasopressin regulated by osmotic concentration of blood, blood volume and nervous system
D. The thyroid gland is an H-shaped gland in the neck.
1. Produces iodine-containing thyroxine which stimulates and maintains metabolic activities and is regulated by
hypothalamus.
2. Lack of iodine results in goiter
3. Produces calcitonin that inhibits release of calcium from bone and is regulated by the concentration of calcium ions in
the blood.
E. The parathyroid glands are pea-sized glands generally embedded in the thyroid.
1. Produce parathyroid hormone also called parathormone which is regulated by the concentration of calcium ions in the
blood
2. Helps maintain calcium ion level in blood necessary for normal functioning of neurons by stimulating release of calcium
from bone, stimulates conversion of vitamin D to active form that promotes calcium uptake from gastrointestinal tract and
inhibits calcium excretion
F. The adrenal glands lie atop the kidneys.
1. The adrenal cortex, the outer layer, is the source of a number of steroid hormones.
a. Glucocorticoids such as cortisol affect carbohydrate, protein and l lipid metabolism and are regulated by ACTH.
b. Mineralcorticoids such as aldosterone affect salt and water balance and are regulated by potassium ion concentration in
the blood and kidney processes.
2. The adrenal medulla, the core, is essentially a large cluster of neurosecretory cells.
a. Secrete adrenaline (epinephrine) and oradrenaline (norepinephrine) which increase blood sugar by influencing the
breakdown of glycogen to glucose, dilate or constrict specific blood vessels, increase rate and strength of heartbeat,
stimulate respiration, dilate respiratory passages
b. Reinforces sympathetic nervous system effects and is stimulated by sympathetic nerve fibers
G. The pancreas, dorsal to the stomach, regulates blood sugar.
1. Some secretory cells called islet cells or Isles of Langerhans release insu lin that lowers blood sugar and increases storage
of glycogen which is controlled by the concentration of glucose and amino acids in blood and somatostatin.
2. Other islet cells secrete glucagon that stimulates breakdown of glycogen to glucose in the liver which is controlled by the
concentration of glucose and amino acids in blood and somatostatin.
3. Other islet cells secrete somatostatin (also secreted by hypothalamus) that helps regulate the rate at which glucose and
other nutrients are absorbed into the bloodstream and may control synthesis of insulin and glucagon.
4. Imbalances associated with diabetes and hypoglycemia can affect behavior because the brain metabolizes glucose almost
exclusively and is immediately affected by low blood sugar.
H. The ovaries and testes are the gonads in females and males respectively necessary for reproduction and
secondary sex characteristics.
1. Estrogens secreted by ovarian follicles develop and maintain sex characteristics in females and initiate buildup of uterine
lining and is regulated by FSH.
2. Progesterone secreted by the corpus luteum in the ovary promotes continued growth of the uterine lining and is
regulated by LH.
3. Androgens such as testosterone secreted by testis support spermatogenesis, develop and maintain sex characteristics of
males and are regulated by LH.
4. Smaller quantities of estrogens and androgens are produced by gonads of opposite sex.
I. Prostaglandins are fatty acids produced by cell membranes in organs of the body. They act like hormones in very
low concentrations stimulating contractions in smooth muscle (especially uterus) and are associated with
dysmenorrhea.
#7: Behavior Genetics
Introduction Statement: The nature-nurture controversy deals with the extent to which heredity and the
environment influence our behavior. Behavioral genetics studies the role played by inheritance in mental ability,
temperament, emotional stability, etc.
I. Transmission of hereditary characteristics is achieved by biological processes (including gametogenesis,
fertilization, embryonic development and protein synthesis).
A. Chromosomes carry information stored in genes to new cells during reproduction.
1. Human body cells have a constant number of chromosomes = 46 in normal cells.
2. Cells of the ovaries and testes produce eggs (ova) and sperms (spermatozoa) which normally have 23 chromosomes each
by a process (gametogenesis) that involves the disjunction of pairs of chromosomes which have genes for the same traits.
3. Of the 23 pairs of chromosomes in human body cells, 22 pairs are non-sex chromosomes (autosomes) and one pair
constitutes the sex chromosomes.
a. A female has 22 pairs of autosomes and two X sex chromosomes. Thus normal eggs have 22 autosomes + X.
b. A male has 22 pairs of autosomes and one X and one Y sex chro mosome. Thus normal sperms have 22 autosomes +
either X or Y.
4. At fertilization the chromosomes from the egg and sperm recombine to form a zygote (fertilized egg) with 46
chromosomes that will develop into a new individual.
5. The sex of the new individual is determined by the sperm that fertilizes the egg.
a. If the sperm carries an X chromosome, the baby will be a female.
b. If the sperm carries a Y chromosome, the baby will be a male.
c. Zygotes develop into females without the presence of a Y chromosome.
6. The new individual gets approximately half his/her hereditary material from the mother and half from the father, one
chromosome from each pair.
7. Genes, carried by chromosomes, are the units of inheritance which are sequences of DNA (deoxyribonucleic acid) that
indirectly produce proteins such as enzymes, hormones and structural proteins.
a. DNA is a molecule shaped like a double stranded helix that looks like a twisted ladder.
a.1. The two uprights (strands) of the DNA "ladder" are com posed of phosphate and sugar.
a.2. The rungs are composed of pairs of nitrogenous bases (either adenine (A) and thymine (T) or guanine (G) and cytosine
(C).
b. The sequence of bases along a strand constitutes the genetic code which gives instructions to perform a specific function
such as to manufacture a particular protein.
b.1. Because of the huge number of possible base sequences, DNA can specify almost unlimited genetic messages for
characteristics of organisms.
b.2. Except for sex cells, cells in the body carry the same genes.
b.3. Only a fraction of the genes in any given cell are active.
II. Transmission of an incorrect number of chromosomes can result from nondisjunctional errors.
A. Chromosomes from a normal body cell can be photographed and arranged in pairs numbered from largest to
smallest (1=largest, 22=smallest, sex chromosomes not numbered).
B. Sperms and eggs with the wrong number of chromosomes can be produced as a result of the failure of pairs of
chromosomes to disjoin during gametogenesis.
1. Eggs can be produced with 21 or 23 autosomes plus an X chromosome.
2. Eggs can be produced with 22 autosomes without an X or with two X chromosomes.
3. Sperms can be produced with 21 or 23 autosomes plus an X or a Y chromosome.
4. Sperms can be produced with 22 autosomes without a sex chromosome or with two X, two Y or both X and Y
chromosomes.
C. Fertilization that includes a gamete with the wrong number of chromosomes results in a zygote and subsequently
an individual with chromosomal abnormalities.
1. Most nondisjunctional fertilizations result in spontaneous abortion (miscarriages), with only a small number of
nondisjunctional individuals involving the smallest autosomes or sex chromosomes surviving.
2. Trisomy-21 (the presence of 3 copies of autosome 21) results in expression of Down syndrome.
a. Down syndrome individuals are typically mentally retarded with a mean IQ of 50 at age 5 and a mean life expectancy of
23 years at age one.
b. Down syndrome individuals typically have a round head, flat nasal bridge, protruding tongue, small round ears, spots in
the iris of the eye and an epicanthal fold in the eye lid, poor muscle tone and coordination.
3. Sex chromosome nondisjunctional conditions are more common than autosomal ones.
a. The XXX condition is not a true syndrome. Only a small percentage express one or more clinical/behavioral problems
such as irregularity in menstruation, retardation, sterility or disturbed personalities.
b. The XYY condition is probably not a true syndrome. XYY males are typically over six feet and have acne beyond
adolescence. Prison studies conducted in the 1960s which indicated that XYY males tend to be aggressive/violent, sterile,
below normal in intelligence and tend to have behavioral disorders have not been substantiated. Some XYY males are
sterile and some mentally retarded.
c. Turner syndrome females have only one X sex chromosome (XO). Girls with Turner’s syndrome are typically short
with a webbed neck, lack ovaries and fail to develop secondary sex characteristics at puberty. Although usually of normal
intelligence, they evidence specific cognitive deficits in arithmetic, spatial organization and visual form perception.
d. Klinefelter syndrome males arise from an XXY zygote. Although the XXY male may have a small penis at birth, the
syndrome is not evident until puberty when male secondary sex characteristics such as development of chest hair,
deepening of voice, and further development of the testes and penis etc. fail to occur. Breast tissue does develop and fat
distribution characteristic of females becomes evident. Klinefelter’s is characterized by sterility. Some XXY males are
mentally retarded and often have mental disturbances such as passivity.
III. The genetic make-up of an individual is called its genotype. The expression of the genes is called its phenotype.
Basic principles of genetics are applicable to human inheritance and expression of genes.
A. Pairs of chromosomes (homologous chromosomes) each have a gene for the same trait at the same locus on each
of the chromosomes (alleles).
1. For traits determined by one pair of genes, if the alleles are the same, the individual is homozygous for the trait and
expresses that phenotypic characteristic.
a. Whether both genes are dominant genes or both genes are recessive genes, the alleles will be expressed.
a.1. Numerous recessive genes are responsible for syndromes in the homozygous condition.
*Tay-Sachs syndrome produces progressive loss of nervous function in a baby which becomes obvious from about six
months of age when the baby fails to sit up, becomes blind, suffers seizures, becomes paralyzed, dies (usually by age 5).
*Albinism arises from a failure to synthesize or store melanin and also involves abnormal nerve pathways to the brain
result ing in quivering eyes and the inability to perceive depth or three-dimensionality with both eyes.
*Phenylketonuria (PKU) results in severe, irreversible brain damage unless the baby is fed a special diet low in
phenylalanine within 30 days of birth because the infant cannot digest this amino acid which can build up and poison cells
of the nervous system. The gene can be tested for.
*Most recessive disorders involve enzyme defects of metabolism.
a.2. A small number of dominant genes are responsible for syndromes and will be expressed in the homozygous or
heterozygous condition. They are usually involved in tissue development. Huntington’s disease is an example that involves
degeneration of the nervous system. Progressive symptoms involve forgetfulness, tremors, jerky motions, loss of the ability
to talk, personality changes such as temper tantrums or inappropriate accusations, blindness and death. A marker for the
gene has been identified that can be tested for. The onset of the disease occurs after 30.
b. For alleles on the X chromosome, with no corresponding allele on the Y chromosome, the allele on the X chromosome
will be expressed in males whether it is dominant or recessive. Recessive genes for color blindness, hemophilia, and LeschNyhan syndrome are located on the X chromosome with no corresponding allele on the Y chromosome. As a result, males
show sex-linked traits much more frequently than females.
b.1. Color blindness affects about 6% males in the population by affecting the cones of the retina so that in most cases red
and green cannot be discerned clearly.
b.2. Hemophilia affects the ability of the blood to clot.
b.3. Lesch-Nyhan is a metabolic disorder that results in self- mutilation. It affects a very small number of males.
b.4. For females to show the sex-linked recessive trait, they would need two recessive genes, one on each X chromo some.
b.5. Females with one allele for a sex-linked trait are carriers and can pass the gene on to sons who will express the trait, or
to daughters who could be carriers or in the ho mozygous condition express the trait.
2. For traits determined by one pair of genes, if the alleles are different, the individual is heterozygous for the trait.
a. The dominant gene is the one that is expressed when alleles are different and only one of the genes is expressed.
b. The recessive gene is the one that is masked when alleles are different and only one of the genes is expressed. An
individual who is heterozygous for a trait is called a carrier (for the recessive trait).
c. For some traits, both genes may be expressed as for type AB blood.
d. For some traits, an intermediate form of inheritance may be ex pressed as for the sickle-cell trait.
3. Most human traits are polygenic, influenced by more than one pair of genes. All complex behavioral characteristics such
as musical, artistic, athletic and intellectual aptitudes are influenced by more than one pair of genes and show continuous
variation rather than distinct categories. What happens to genetic potential depends upon environmental conditions.
4. Phenotypic characteristics may change over time such as hair color or may be modified by environmental factors.
5. Behaviors and diseases may have variations only some of which are genetically based. A form of familial Alzheimer’s
disease has been attributed to a gene on chromosome 21, but not all cases of Alzheimer’s disease are associated with that
gene.
IV. Behavioral genetics research is accomplished by a variety of techniques.
A. Extrapolation from selective breeding experiments in rats, dogs and other animals has yielded information regarding
the genetic and environmental contributions to excitability, aggression, intelligence, etc. Animals showing the highest value
of a given trait are bred and animals showing the lowest value of the given trait are selectively bred. With environmental
conditions held constant, if two different "strains" develop after several generations, a genetic component for the
characteristic under study has been established.
B. Twin studies have been conducted to assess the influence of heredity on expression of a behavior or constellation of
behaviors.
1. Monozygotic (MZ) or identical twins develop from a single fertilized egg that has split to form two embryos early in
development. Thus they share the same heredity.
2. Dizygotic (DZ) or fraternal twins develop from two different fertilized eggs. Thus, like other siblings, or each parent and
child, they share about 50% of their genes.
3. In twin studies a particular trait is studied for appearance in sets of identical twins and sets of fraternal twins. If there is
more similarity in identical twins than in fraternal twins, researchers infer a genetic component for the trait. Such
constellations of behaviors as schizophrenia and general intelligence have shown greater similarity in identical twins than in
fraternal twins, for example. These studies are not controlled experiments.
C. Adoption studies assess genetic influence by comparing resemblance of adopted children to both their adoptive and
biological parents. The children must have been adopted as infants without contact with their biological parents. If the
children resemble their biological parents, but not their adoptive families, with respect to a given trait, researchers infer a
genetic component for that trait. Such constellations of behaviors as alcoholism, schizophrenia and general intelligence
have shown both genetic and environmental components.
D. The Human Genome Project is an international effort to map the loci of all of the genes on the twenty-three chromosome
pairs in humans. Techniques of biotechnology have been employed to close in on locations for genes for Alzheimer’s,
Huntington’s, Duchenne muscular dystrophy. The DNA sequence for some genes has already been established.
E. Social values, prejudices and fallacies are imposed on our biological understanding of race and other polygenic
inheritances.
Unit Two: CRITICAL THINKING QUESTIONS
1. Progress in understanding the mind and treating brain disorders has advanced with the creation of new and better
technology. Modern technology is costly. If you could choose just one piece of expensive equipment for a neuroscience
laboratory, which would you choose? Why?
2. Laboratory research with rats has shown that dendrites develop more complex and intricate branching when subjects are
exposed to enriched and variable external stimulation. What could this mean for many children reared in deprived or
limited socioeconomic environments? What should we do to enable individuals to develop their potential?
3. The nature of messages sent by the nervous system is electrochemical. Describe the electrical nature of axonal
transmission and the chemical nature of synaptic transmission.
4. If we accidentally touch a hot pot on the stove, we immediately retract our hand, even before saying, "Ouch!" Discuss
specifically what is involved in this behavior. Be sure to include the following:
a. a description of reception and transmission of an impulse by a neuron
b. the path of the reflex
c. an explanation of why the hand in retracted before the exclamation is emitted
5. In a television commercial, a man loses his sight over the course of a few weeks. Which parts of the brain would you
suspect might be affected? Give reasons to support your answer. What medical procedures would you advise in order to
find out more?
6. After the railroad spike entered his brain and exited through his cheek, Phineas Gage, who had been emotionally stable
and well organized, became disorganized, angered easily and could not plan ahead. Describe the parts of the brain that you
think were affected and support your hypothesis.
7. A person suffering from severe psychomotor epilepsy is surgically treated by corpus callosum transection (split-brain
surgery). Describe how a psychologist would be able to tell behaviorally that the patient’s corpus callosum had been
severed.
8. Medical science has developed to the point where heart, liver and lung transplants are almost routine. Tissue transplants
for Parkinson’s patients have already been successful. Perhaps brain transplants will soon be a reality. With the transplant
of what brain structures would a person cease to be that person? Where in all the brain’s structures do you think the mind
might be found? What is the relationship of the brain to the mind?
9. A frail old woman who had saved money for a large-screen television for a long time manages to push it out of her
burning apartment. After the fire is extinguished, two strong firemen are needed to push the TV back in. Account for the
woman’s ability to push the set out. In your answer include reference to the endocrine system and autonomic nervous
system.
10. The pituitary gland used to be called, "the master gland." Why did scientists think this was an appropriate name? Why
do neuroscientists no long use that term for the pituitary?
11. Give an example of a negative feedback control cycle involving hormones in humans. Why is it considered negative?
Why don’t we find positive feedback control cycles in humans?
12. The publication of another book dealing with intelligence of groups of people has revived a controversy. Can we fully
separate "nature and nurture" in a study of intelligence? Why can’t we design an experiment to isolate the hereditary
component of intelligence ?
13. If a genetic factor is found to play a part in mental illness, such as manic depression, should individuals be tested for the
factor? If it is found, then what?