Biological Implications PDF

Biological implication  Objective Recalling the major functions controlled by various areas of the brain  Cerebrum Frontal lobes – voluntary body movement – movements that control speaking, thinking, and judgment formation Parietal lobes – perception & interpr...

Biological implication  Objective Recalling the major functions controlled by various areas of the brain  Cerebrum Frontal lobes – voluntary body movement – movements that control speaking, thinking, and judgment formation Parietal lobes – perception & interpretation of most sensory information – touch, pain, taste, and body position Temporal lobes – auditory functions – short-term memory Occipital lobes – visual reception and interpretation  Diencephalon Thalamus – integrates all sensory input except smell Hypothalamus – regulates the pituitary gland – regulates appetite and temperature Limbic system – associated with fear, anxiety, anger, aggression, love, joy, hope, sexuality, and social behavior  Mesencephalon – integration of reflexes (visual, auditory, righting) Pons – respiration – skeletal muscle tone Medulla – regulates heart rate, blood pressure, and respiration – swallowing, sneezing, coughing,  Cerebellum – involuntary movement, such as the coordination/maintenance of posture Neurotransmitters – essential functions of human emotion and behavior – many psychotropics work here – categories of neurotransmitters include cholinergics, monoamines, amino  Neurotransmitters (cont’d) Cholinergics Acetylcholine – 1st chemical to be identified as neurotransmitter – involved in disorders of motor behavior and memory Monoamines Norepinephrine – fight-or-flight syndrome Dopamine – physical activation of the body Serotonin – levels dictate heightened or lowered sense of arousal  Neurotransmitters (cont’d) Amino Acids Gamma-aminobutyric acid (GABA) – decreased levels in anxiety and movement disorders – Huntington’s disease, epilepsy Glutamate – decreased receptor activity can induce psychotic behavior Neuropeptides Somatostatin – low concentrations in Alzheimer’s disease  Autonomic Nervous System Sympathetic nervous system – dominant during stressful situations – fight-or-flight response – increases cardiac and respiratory activity, and decreases GI functioning – involves acetylcholine and norephinephrine Parasympathetic nervous system – dominant in the nonstressful or relaxed state – promotes efficient GI functioning – maintains heart and respirations at The Endocrine System Overview of the Endocrine System System of ductless glands that secrete hormones – Hormones are “messenger molecules” – Circulate in the blood – Act on distant target cells – Target cells respond to the hormones for which they have receptors – The effects are dependent on the programmed response of the target cells – Hormones are just molecular triggers Basic categories of hormones – Amino acid based: modified amino acids (or amines), peptides (short chains of amino acids), and proteins (long chains of amino acids) – Steroids: lipid molecules derived from 11 cholesterol  Endocrine Organs Purely endocrine organs – Pituitary gland – Pineal gland – Thyroid gland – Parathyroid glands – Adrenal: 2 glands Cortex Medulla Endocrine cells in other organs – Pancreas – Thymus – Gonads – Hypothalamus 12  Sits in hypophyseal fossa: depression in sella The Pituitary turcica of sphenoid bone Pituitary secretes 9 hormones Two divisions: 1. TSH The first four are “tropic” 2. ACTH hormones, they regulate 3. FSH the function of other Anterior 4. LH ________ hormones pituitary 5. GH 6. PRL (adenohypophysi 7. MSH s) _________________________________________________________________ 8. ADH (antidiuretic hormone), or vasopressin Posterior 9. Oxytocin pituitary (neurohypophysis ) 13  What the letters stand for… TSH: thyroid-stimulating hormone ACTH: adrenocorticotropic hormone FSH: follicle-stimulating hormone LH: luteinizing hormone GH: growth hormone PRL: prolactin MSH: melanocyte-stimulating hormone ADH: antidiuretic hormone Oxytocin 14  So what do the pituitary hormones do? The four tropic ones regulate the function of other hormones TSH stimulates the thyroid to produce thyroid hormone ACTH stimulates the adrenal cortex to produce corticosteroids: aldosterone and cortisol FSH stimulates follicle growth and ovarian estrogen production; stimulates sperm production and androgen-binding protein LH has a role in ovulation and the growth of the corpus luteum; stimulates androgen secretion by interstitial cells in testes 15  The others from the anterior pituitary… GH (aka somatrotropic hormone) stimulates growth of skeletal epiphyseal plates and body to synthesize protein PRL stimulates mammary glands in breast to make milk MSH stimulates melanocytes; may increase mental alertness 16  From the posterior pituitary (neurohypophysis) structurally part of the brain ADH (antidiuretic hormone AKA vasopressin) stimulates the kidneys to reclaim more water from the urine, raises blood pressure Oxytocin prompts contraction of smooth muscle in reproductive tracts, in females initiating labor and ejection of milk from breasts 17  The Thyroid Gland Anterior neck on trachea just inferior to larynx Two lateral lobes and an isthmus Produces two hormones – Thyroid hormone: tyrosine based with 3 or 4 iodine molecules T4 (thyroxine) and T3 – Calcitonin involved with calcium and phosphorus 18 Some Effects of Thyroid Hormone (Thyroxine) Increases the basal metabolic rate – The rate at which the body uses oxygen to transform nutrients (carbohydrates, fats and proteins) into energy Affects many target cells throughout the body; some effects are – Protein synthesis – Bone growth – Neuronal maturation – Cell differentiation 19  The Effects of Calcitonin Secreted from thyroid parafollicular (C) cells when blood calcium levels are high Calcitonin lowers Ca++ by slowing the calcium-releasing activity of osteoclasts in bone and increasing calcium secretion by the kidney Acts mostly during childhood 20  Function of PTH (parathyroid hormone or “parathormone”) Increases blood Ca++ (calcium) concentration when it gets too low Mechanism of raising blood calcium 1. Stimulates osteoclasts to release more Ca++ from bone 2. Decreases secretion of Ca++ by kidney 3. Activates Vitamin D, which stimulates the uptake of Ca++ from the intestine Unwitting removal during thyroidectomy was lethal Has opposite effect on calcium as calcitonin (which lowers Ca++ levels) 21  Adrenal Gland Adrenal cortex – Secretes lipid-based steroid hormones, called “corticosteroids” – “cortico” as in “cortex” MINERALOCORTICOIDS – Aldosterone is the main one GLUCOCORTICOIDS – Cortisol (hydrocortisone) is the main one Adrenal medulla – Secretes epinephrine and norepinephrine 22  Aldosterone, the main mineralocorticoid Secreted by adrenal cortex in response to a decline in either blood volume or blood pressure (e.g. severe hemorrhage) – Is terminal hormone in renin-angiotensin mechanism Prompts distal and collecting tubules in kidney to reabsorb more sodium – Water passively follows – Blood volume thus increases 23  Cortisol, the most important glucocorticoid (Glucocorticoid receptors are found in the cells of most vertebrate tissues) It is essential for life Helps the body deal with stressful situations within minutes – Physical: trauma, surgery, exercise – Psychological: anxiety, depression, crowding – Physiological: fasting, hypoglycemia, fever, infection Regulates or supports a variety of important cardiovascular, metabolic, immunologic, and homeostatic functions including water balance People with adrenal insufficiency: these stresses can cause hypotension, shock and death: must give glucocorticoids, eg for24 surgery or if have infection, etc.  Cortisol, continued Keeps blood glucose levels high enough to support brain’s activity – Forces other body cells to switch to fats and amino acids as energy sources Catabolic: break down protein Redirects circulating lymphocytes to lymphoid and peripheral tissues where pathogens usually are In large quantities, depresses immune and inflammatory response – Used therapeutically – Responsible for some of its side effects 25  Hormonal stimulation of glucocorticoids HPA axis (hypothalamic/pituitary/adrenal axis) With stress, hypothalamus sends CRH to anterior pituitary (adenohypophysis) Pituitary secretes ACTH ACTH goes to adrenal cortex where stimulates glucocorticoid secretion – Sympathetic nervous system can also stimulate it Adrenal cortex also secretes DHEA (dehydroepiandrosterone) – Converted in peripheral tissues to testosterone and estrogen (also steroid hormones) – Unclear function in relation to stress 26  The Pineal Gland At the end of a short stalk on the roof of the diencephalon Pinealocytes with dense calcium particles Can be seen on x-ray (because of Ca++) Melatonin helps regulate the circadium rhythm – The biological clock of the diurnal (night/day) rhythm – Complicated feedback via retina’s visual27  The Pancreas Exocrine and endocrine cells Acinar cells (forming most of the pancreas) – Exocrine function – Secrete digestive enzymes Islet cells (of Langerhans) – Endocrine function 28  The Gonads (testes and ovaries) main source of the steroid sex hormones Testes – Interstitial cells secrete androgens – Primary androgen is testosterone Maintains secondary sex characteristics Helps promote sperm formation Ovaries – Androgens secreted by thecal folliculi Directly converted to estrogens by follicular granulosa cells – Granulosa cells also produce progesterone – Corpus luteum also secretes estrogen and progesterone 29  Endocrine cells in various organs continued The heart: atrial natriuretic peptide (ANP) – Stimulates kidney to secrete more salt – Thereby decreases excess blood volume, high BP and high blood sodium concentration GI tract & derivatives: Diffuse neuroendocrine system (DNES) The placenta secretes steroid and protein hormones – Estrogens, progesterone – CRH – HCG The kidneys – Juxtaglomerular cells secrete renin Renin indirectly signals adrenal cortex to secrete aldosterone – Erythropoietin: signals bone marrow to increase RBC production The skin – Modified cholesterol with uv exposure becomes Vitamin D precursor 30 – Vitamin D necessary for calcium metabolism: signals intestine  Implication for psychiatric illness Schizophrenia – Anomalies of the Brain Some studies have shown a significant enlargement in cerebral ventricular size in the brains. Dilation of cortical sulci and fissures were also observed. Temporal lobe size may also be decreased abnormal cerebral asymmetry, reduced cerebellar volume, and brain density changes. Neuropathology in the limbic system, thalamus, basal ganglia, hippocampus, and frontal cortex.  Cont.. Neurotransmitter Hypothesis – Excess of dopamine-dependent neuronal activity in the brain – Abnormalities in the neurotransmitters norepinephrine, serotonin, acetylcholine, and GABA and the neuro-regulators, such as prostaglandins and endorphins, have been suggested.  Possible Endocrine Correlation The exact mechanism is unknown – However, there may be some correlation between decreased levels of the hormone prolactin and schizophrenia. – The neurotransmitter dopamine, which is elevated in schizophrenia, acts as the prolactin-inhibiting factor. – Some studies with non-medicated schizophrenic patients have shown an inverse relationship between prolactin concentrations and symptoms of schizophrenia.  Mood Disorders Neuroanatomical Considerations – pathology of the prefrontal cortex and the limbic system (particularly the hippocampus, the amygdala, the hypothalamus, and the cingulate gyrus). – The limbic system plays a major role in the discharge of emotions. Stooped posture, motor slowness, and the minor cognitive impairment of depression indicate involvement of the basal ganglia. – Dysfunction of the hypothalamus is suggested by alterations in sleep, appetite, and sexual behavior.  Cont… Neurotransmitter Hypothesis – Depression: deficiency of norepinephrine and dopamine, and mania with a functional excess of these amines. – The neurotransmitter serotonin appears to remain low in both states. – Norepinephrine has been identified as a key component in the mobilization of the body to deal with stressful situations.  Possible Endocrine Correlation – In clients who are depressed, the normal system of hormonal inhibition fails, resulting in a hypersecretion of cortisol. – This elevated serum cortisol is the basis for the dexamethasone suppression test that is sometimes used to determine if an individual has somatically treatable depression.  Anxiety Disorders Neuroanatomical Considerations – The limbic system has been the focus of study in the correlation of brain pathology to anxiety disorders. – The locus coeruleus has also been implicated as a pathophysiological site in anxiety disorders, particularly with panic disorder.  Neurotransmitter Hypothesis – norepinephrine, serotonin, and GABA. – Norepinephrine causes hyperarousal and anxiety, and elevated levels are implicated in the etiology of panic disorder. – Serotonin may play a role in the behaviors associated with obsessive- compulsive disorder.  Possible Endocrine Correlation – Increased levels of TSH and prolactin have been observed in individuals with anxiety disorders. – Some individuals with obsessive- compulsive disorder exhibit increased cortisol levels (similar to those seen in depressive disorder). – The role of neuroendocrinedys regulation in the etiology of anxiety disorders has not as yet been determined.  Anorexia Nervosa – Neuroanatomical Considerations: enlarged cerebrospinal fl uid (CSF) spaces (enlarged sulci and ventricles) during the starvation period in individuals with anorexia nervosa.  Neurotransmitter Hypothesis – Preliminary studies have indicated that there is probably a dysregulation of dopamine, serotonin, and norepinephrine in individuals with anorexia nervosa. – A decrease in serotonin turnover has been found in clients with both bulimia and anorexia, and low norepinephrine levels were discovered.  Possible Endocrine Correlation – elevated cortisol levels and a possible impairment of dopaminergic regulation in people with anorexia. Diagnostic procedures  Electroencephalography (EEG) – measures brain electrical activity – detects dysrhythmias, asymmetries, and suppression of brain rhythms – epilepsy, metabolic disorder, degenerative disease Computed tomographic (CT) scan – measures accuracy of brain structure – identifies anatomical differences – schizophrenia, organic mental disorders, bipolar disorder  Magnetic resonance imaging (MRI) – measures anatomical and biochemical status of various segments of the brain – detects changes in myelination – schizophrenia Positron emission tomography (PET) – measures specific brain activity and functioning – identifies problems with blood flow, oxygen utilization, glucose metabolism, and neurotransmitter/receptor interaction  Discussing commonly used physiological and psychological tests utilized in evaluating the function of the brain  Physiological Tests Basic Metabolic Profile (BMP) – electrolytes – glucose Complete Blood Chemistry (CBC) Thyroid Panel Urinalysis  Mental Status Examination (MSE) Describes all areas of mental functioning: Appearance Mood and affect Speech and language Thought content Perceptual disturbances Insight and judgment Sensorium Memory and attention General intellectual level