Townsend Ch 2 Biological Implications

Psychobiology

The study of the biological foundations of cognitive, emotional, and behavioral processes

Recently, a greater emphasis has been
placed on the study of the biological
foundations of _ and called psychobiology

Cognitive processes
Emotional processes
Behavioral processes

Forebrain consists of the

Cerebrum

Diencephalon

Midbrain

Mesencephalon

Hindbrain consists of the

Pons

Medulla

Cerebellum

Frontal

Temporal

Occipital

Parietal

lobes are found in the

Cerebrum

Cerebrum

Largest part of the brain. Composed of two hemispheres connected by a band of nerve tissue that houses a band of 200 million axons called the corpus callosum. The outer layer is called the cerebral cortex. It is extensively folded and consists of billions of neurons. The left hemisphere appears to deal with logic and solving problems. The right hemisphere may be called the “creative” brain and is associated with affect, behavior, and spatial-perceptual functions

Frontal lobe

Voluntary body movement, including movements that permit speaking, thinking and judgment formation, and expression of feelings

Parietal lobe

Perception and interpretation of most sensory information (including touch, pain, taste, and body position)

Temporal lobe

Hearing, short-term memory, and sense of smell; expression of emotions through connection with limbic system

Occipital lobe

Visual reception and interpretation

Diencephalon

Connects cerebrum with lower brain structures

Thalamus

Integrates all sensory input (except smell) on way to cortex; some involvement with emotions and mood

Hypothalamus

Regulates anterior and posterior lobes of pituitary gland; exerts control over actions of the autonomic nervous system; regulates appetite and temperature. Regulates visceral responses to emotional situations and body rhythms such as mood changes and sleep–wake cycles

Mesencephalon (midbrain)

Responsible for visual, auditory, and balance (“righting”) reflexes

Pons

Regulation of respiration and skeletal muscle tone; ascending and descending tracts connect brainstem with cerebellum and cortex

Medulla

Pathway for all ascending and descending fiber tracts; contains vital centers that regulate heart rate, blood pressure, and respiration; reflex centers for swallowing, sneezing, coughing, and vomiting

Cerebellum

Regulates muscle tone and coordination and maintains posture and equilibrium

What does the hypothalamus regulate?

Regulation of the pituitary gland

Direct neural control over the actions of the autonomic nervous system

Regulation of appetite, temperature, blood pressure, thirst, and circadian rhythms (sleep and wakefulness)

Regulation of blood pressure

The Limbic system

a group of structures including the amygdala, mammillary body, olfactory tract, hypothalamus, cingulate gyrus, septum pellucidum, thalamus, hippocampus, and fornix, that, through communication with the hypothalamus, controls several autonomic, endocrine, and somatic functions. This system has been called the “emotional brain” because of its association with feelings of fear and anxiety; anger, rage, and aggression; and love, joy, and hope and with sexuality and social behavior

Neuron

composed of a cell body, an axon, and dendrites

Cell body

contains the nucleus and is essential for the continued life of the neuron

Dendrites

are processes that transmit impulses toward the cell body

Axon

transmits impulses away from the cell body

The axons and dendrites are covered by

layers of cells called neuroglia that form a coating, or “sheath,” of myelin

Myelin

a phospholipid that provides insulation against short-circuiting of the neurons during their electrical activity and increases the velocity of the impulse

White matter of the brain and spinal cord

so called because of the whitish appearance of the myelin sheath over the axons and dendrites

Gray matter

composed of cell bodies that contain no myelin

Neuron classes

include afferent (sensory), efferent (motor), and interneurons

Afferent naurons

carry impulses from receptors in the internal and external periphery to the CNS, where they are then interpreted into various sensations

Efferent neurons

carry impulses from the CNS to effectors in the periphery, such as muscles (that respond by contracting) and glands (that respond by secreting)

Interneurons

exist entirely within the CNS, and 99% of all nerve cells belong to this group. They may carry only sensory or motor impulses, or they may serve as integrators in the pathways between afferent and efferent neurons. They account in large part for thinking, feelings, learning, language, and memory

Synapse

The junction between two neurons

Neurotransmitters

stored in the axon terminals of the presynaptic neuron. An electrical impulse through the neuron causes the release of this neurotransmitter into the synaptic cleft. The neurotransmitter then diffuses across the synaptic cleft and combines with receptor sites that are situated on the cell membrane of the postsynaptic neuron

Autonomic Nervous System

considered part of the peripheral nervous system. Its regulation is modulated by the hypothalamus, and emotions exert a great deal of influence over its functioning. For this reason, the ANS has been implicated in the etiology of a number of psychophysiological disorders

Autonomic Nervous System divisions

sympathetic and the parasympathetic

Sympathetic nervous system

is dominant in stressful situations and prepares the body for the fight-or-flight response. The fight-or-flight response causes an increase in heart rate and respirations and a decrease in digestive secretions and peristalsis. Blood is shunted to the vital organs and to skeletal muscles to ensure adequate oxygenation

Parasympathetic nervous system

when an individual is in a relaxed, nonstressful condition. The heart and respirations are maintained at a normal rate, and secretions and peristalsis increase for normal digestion. Elimination functions are promoted

Cholinergic Neurotransmitter

Acetylcholine

Acetylcholine

It is a major effector chemical in the ANS, producing activity at all sympathetic and parasympathetic presynaptic nerve terminals and all parasympathetic postsynaptic nerve terminals. It is highly significant in the neurotransmission that occurs at the junctions of nerve and muscles. Acetylcholinesterase is the enzyme that destroys acetylcholine or inhibits its activity. In the CNS, acetylcholine neurons innervate the cerebral cortex, hippocampus, and limbic structures. The pathways are especially dense through the area of the basal ganglia in the brain

Functions of acetylcholine

include sleep, arousal, pain perception, motor control, learning, and memory.

Possible implications in mental illness: Cholinergic mechanisms may have some role in certain disorders of motor behavior and memory, such as Parkinson’s disease, Huntington’s disease, and Alzheimer’s disease

Monoamines

Norepinephrine, dopamine, serotonin, histamine

Norepinephrine

produces activity at the sympathetic postsynaptic nerve terminals in the ANS, resulting in the fight-or-flight responses in the effector organs. In the CNS, norepinephrine pathways originate in the pons and medulla and innervate the thalamus, dorsal hypothalamus, limbic system, hippocampus, cerebellum, and cerebral cortex

Norepinephrine functions

include the regulation of mood, cognition, perception, attention, vigilance, memory, cardiovascular functioning, and sleep–wake cycles.

Possible implications in mental illness: The activity of norepinephrine has been implicated in certain mood disorders such as depression and mania, in anxiety states, and in schizophrenia

Dopamine function

Movement and coordination, emotions, voluntary judgment, release of prolactin

Decreased levels- Parkinson’s disease, depression, Tourette syndrome, and ADHD

Increased levels- Mania, schizophrenia, and addictions

Serotonin functions

Sleep and arousal, libido, appetite, mood, aggression, pain perception, coordination, judgment

Decreased levels- Depression, anxiety

Increased levels- Anxiety states

Histamine functions

Wakefulness; pain sensation and inflammatory response

Decreased levels- Depression

Increased levels- Sleep disorders, anxiety, Alzheimer’s disease, psychosis

Amino acids

Inhibitory amino acids, excitatory amino acids

Gamma-Aminobutyric Acid (inhibitory)

Inhibitory neurotransmitters, such as GABA, prevent postsynaptic excitation, interrupting the progression of the electrical impulse at the synaptic junction. This function is significant when slowdown of body activity is advantageous. Enhancement of the GABA system is the mechanism of action by which the benzodiazepines produce their calming effect.

Possible implications in mental illness- Alterations in the GABA system have been implicated in anxiety disorders, depression, movement disorders (Huntington’s disease), and various forms of epilepsy. GABA levels, in a complex interaction with other neurotransmitters such as dopamine, have also been implicated in substance use disorders and addiction

Glycine (inhibitory)

Glycine appears to be the neurotransmitter of recurrent inhibition of motor neurons within the spinal cord and is possibly involved in the regulation of spinal and brainstem reflexes.

Possible implications in mental illness- Glycine has been implicated in the pathogenesis of certain types of spastic disorders and in “glycine encephalopathy,” which is known to occur with toxic accumulation of the neurotransmitter in the brain and cerebrospinal fluid

Glutamate and Aspartate (excitatory)

Glutamate and aspartate function in the relay of sensory information and in the regulation of various motor and spinal reflexes. Glutamate also plays a role in memory and learning.

Possible implications in mental illness- Alterations in these systems have been implicated in the etiology of certain neurodegenerative disorders, such as Huntington’s disease, temporal lobe epilepsy, and spinal cerebellar degeneration. Increases in glutamate have been associated with neuron degeneration in Alzheimer’s disease. Problems in making or using glutamate have been linked to many mental disorders, including autism spectrum disorder (ASD), obsessive-compulsive disorder (OCD), schizophrenia, and depression

Neuropeptides

Opioid peptides, substance P, somatostatin

Opioid peptides

With their natural morphine-like properties, opioid peptides are thought to have a role in pain modulation. They are released in response to painful stimuli and may be responsible for producing the analgesic effect following acupuncture. Alter the release of dopamine and affect the spontaneous activity of the dopaminergic neurons.

Possible implications in mental illness - Modulation of dopamine activity by opioid peptides may be associated with addiction and some symptoms of schizophrenia, and a growing body of research supports that opioid system dysregulation may contribute to depression

Substance P

Substance P plays a role in sensory transmission, particularly in the regulation of pain.

Possible implications in mental illness- Substance P levels have been associated with depression and post-traumatic stress disorder (PTSD). Studies have demonstrated that people with depression and PTSD had elevated levels of substance P in their cerebral spinal fluid

Somatostatin

Somatostatin has been shown to stimulate dopamine, serotonin, norepinephrine, and acetylcholine and to inhibit norepinephrine, histamine, and glutamate. It also acts as a neuromodulator for serotonin in the hypothalamus, thereby regulating its release (controlling whether it is stimulated or inhibited)

Possible implications in mental illness- High concentrations of somatostatin have been reported in brain specimens of clients with Huntington’s disease and low concentrations in those with Alzheimer’s disease and depression

Neuroendocrinology

is the study of the interaction between the nervous system and the endocrine system, and the effects of various hormones on cognitive, emotional, and behavioral functioning

The hypothalamus has direct control over the

posterior pituitary

Posterior pituitary consists of

vasopressin (antidiuretic hormone) and oxytocin

Antidiuretic Hormone (ADH)

conserves body water and maintain normal blood pressure. The release is stimulated by pain, emotional stress, dehydration, increased plasma concentration, and decreases in blood volume.

An alteration in the secretion of this hormone is related to the polydipsia seen in patients with diabetes and may be one of many factors contributing to the polydipsia, or water intoxication, patients with severe mental illness, particularly those with schizophrenia.

Other factors correlated with excessive thirst include adverse effects of psychotropic medications and features of the behavioral disorder itself. It is important to note that severe polydipsia can result in electrolyte imbalance and death

Oxytocin

Contraction of the uterus for labor; release of breast milk

releases stimulated by end of pregnancy; stress; during sexual arousal

Anterior pituitary consists of

Growth hormone
Thyroid-stimulating hormone
Adrenocorticotropic hormone
Prolactin
Gonadotropic hormones
Melanocyte-stimulating hormone

Growth hormone

responsible for growth in children as well as for continued protein synthesis throughout life. During periods of fasting, it stimulates the release of fat from the adipose tissue to be used for increased energy. The release is stimulated in response to periods of hyperglycemia. Stimulated in response to hypoglycemia and to stressful situations. During prolonged stress, GH has a direct effect on protein, carbohydrate, and lipid metabolism, resulting in increased serum glucose and free fatty acids to be used for increased energy. Deficiency has been noted in many patients with major depressive disorder, and several GH abnormalities have been noted in patients with anorexia nervosa

Altered secretion of ADH can cause

Polydipsia; altered pain response; modified sleep pattern

Altered secretion of growth hormone can cause

Anorexia nervosa

Thyroid-stimulating hormone

Stimulation of secretion of needed thyroid hormones for metabolism and regulation of temperature

release stimulated by thyrotropin-releasing hormone from hypothalamus

Decreased secretion of TSH can lead to

Fatigue, depression

Increased secretion of TSH can lead to

Insomnia, anxiety, emotional lability

Adrenocorticotropic hormone (ACTH)

Stimulation of secretion of cortisol, which plays a role in response to stress

release stimulated by corticotropin-releasing hormone from hypothalamus

Adrenal cortex

Altered secretion of Adrenocorticotropic hormone (ACTH) can cause

Decreased levels: Depression, apathy, fatigue

Increased levels: Mood disorders, psychosis

Prolactin

Stimulation of milk production

release stimulated by prolactin-releasing hormone from hypothalamus

Increased levels of prolactin can lead to

Depression, anxiety, decreased libido, irritability

Gonadotropic hormones

Stimulation of secretion of estrogen, progesterone, and testosterone; role in ovulation and sperm production

release stimulated by gonadotropin-releasing hormone from hypothalamus

Ovaries and testes

Melanocyte-stimulating hormone

release stimulated by onset of darkness

Pineal gland

Increased levels of Melanocyte-stimulating hormone can lead to

depression

Hyperthyroidism s/s

irritability, insomnia, anxiety, restlessness, weight loss, emotional lability, and, in some instances, progression to delirium or psychosis

Chronic hypothyroidism s/s

fatigue, decreased libido, memory impairment, depression, and suicidal ideations

Addison’s disease is the result of

hyposecretion of the hormones of the adrenal cortex

Hypersecretion of cortisol results in

Cushing’s disease

Gonaditropins

follicle-stimulating hormone (FSH) and luteinizing hormone (LH)

Follicle-stimulating hormone (FSH)

initiates sperm production in the testes

Luteinizing hormone (LH)

increases secretion of testosterone by the interstitial cells of the testes

Most of the biological rhythms of the body operate over a period of about

24 hours

Genotype

refers to the total set of genes present in an individual and coded in the DNA

Phenotype

eye color, height, blood type, the characteristics of one’s voice, and hair type. As evidenced by the examples presented, phenotypes are not only genetic but may also be acquired (influenced by the environment) or a combination of both

Genetics

is the study of the biological transmission of certain characteristics
(physical and/or behavioral) from parent to offspring

Psychoneuroimmunology

is the study of the relationship between the immune system, the nervous system, and psychological processes

Cytokines

are active when an individual is fighting an infection or any other condition that creates inflammation in the body. Research has demonstrated that cytokines are part of an essential and complex system of responses that are crucial for reducing inflammation and bolstering the immune response, and they are active in mood disorders such as depression and bipolar disorder

Nonspecific immune reactions

include neutrophils, monocytes, and macrophages. They work to destroy the invasive organism and initiate and facilitate healing of damaged tissue. If these cells are not effective in accomplishing a satisfactory healing response

Specific immune mechanisms

If these nonspecific immune reaction cells are not effective in accomplishing a satisfactory healing response, this immune mechanism takes over

Implications of the Immune System in Psychiatric Illness

Increased susceptibility following exposure to a
stressful stimulus

Effects of hormones and neurotransmitters

Electroencephalography (EEG)

Electrodes are placed on the scalp in a standardized position. Amplitude and frequency of beta, alpha, theta, and delta brain waves are graphically recorded on paper by ink markers for multiple areas of the brain surface

Electroencephalography (EEG) purpose

Measures brain electrical activity; identifies dysrhythmias, asymmetries, or suppression of brain rhythms; used in the diagnosis of epilepsy, neoplasm, stroke, metabolic or degenerative disease

Computerized EEG mapping

are summarized by computer-assisted systems in which various regions of the brain are identified and functioning is interpreted by color coding or gray shading

Computerized EEG mapping purpose

Measures brain electrical activity; used largely in research to represent statistical relationships between individuals and groups or between two populations of subjects (patients with schizophrenia vs. control subjects)

Psychopharmacology

remains a primary treatment modality for mental disorders

CT scan

may be used with or without contrast medium. X-rays are taken of various transverse planes of the brain while a computerized analysis produces a precise reconstructed image of each segment

CT scan purpose

Measures accuracy of brain structure to detect possible lesions, abscesses, areas of infarction, or aneurysm.

Has also identified various anatomical differences in patients with schizophrenia, organic mental disorders, and bipolar disorder

MRI

Within a strong magnetic field, the nuclei of hydrogen atoms absorb and reemit electromagnetic energy that is computerized and transformed into image information. No radiation or contrast medium is used

MRI purpose

Measures anatomical and biochemical status of various segments of the brain; detects brain edema, ischemia, infection, neoplasm, trauma, and other changes such as demyelination.

Morphological differences have been noted in brains of patients with schizophrenia as compared with control subjects

Positron emission tomography (PET)

The patient receives an IV injection of a radioactive substance (type depends on brain activity to be visualized). The head is surrounded by detectors that relay data to a computer that interprets the signals and produces the image