CoverModule 1.0. Homeostasis, Membranes, Electrophysiology and ANS (Essay Questions)1.1. Homeostasis1.1.1. Homeostasis Defined1.1.2. Homeostatic Control Systems1.1.3. Feedback Response Loop1.2. Cell Transport; Water & Solutes1.2.1. Fluid Compartments1.2.2. Osmosis1.2.3. Diffusion of Solutes1.2.4. Active Transport1.2.5. Bulk Transport1.3. Electrophysiology1.3.1. Ions and Cell Membranes1.3.2. Membrane Potentials1.3.3. Graded Potential1.3.4. Action Potentials1.3.5. Refractory Periods1.3.6. Propagation of an Action Potential1.4. THE SYNAPSE1.5. THE AUTONOMIC NERVOUS SYSTEM1.5.1. Organization of the Nervous System1.5.2. Structural Organization of the ANS1.5.3. The SNS and the PNS1.5.4. The Enteric Nervous System1.5.5. Physiology of the ANS1.5.6. Neurotransmitters of the ANS1.5.7. Receptors of the ANS1.5.8. Actions of the Autonomic Nervous System1.5.9. Table of Actions for the SNS and PNS and Some Common DrugsModule 2.0. Skeletal Muscle and Special Senses2.1. Structural Organization of Skeletal Muscle2.2.1. Neuromuscular Junction, Excitation-Contraction Coupling2.2.2. Muscle Contractures and Cramps2.3. Whole Muscle Contraction, Fiber Type, Fatigue and Muscle Pharmacology2.3.1. Motor Units2.3.2. Factors that Influence the Force of Contraction2.3.3. Energy Source for Muscle Contraction2.3.4. Skeletal Muscle Fiber Types2.3.5. Fatigue2.3.6. Muscle Pharmacology2.4. Smooth Muscle2.4.1. Smooth Muscle Contraction2.5. Control of Body Movement2.5.1. Voluntary Control of Muscle2.5.2. Reflexes2.6. Taste and Smell2.6.1. Taste2.6.2. The Sense of Smell2.7. Vision2.7.1. Structure of the Eye2.7.2. Focusing Light on the Retina2.7.3. Converting Light to Action Potentials2.7.4. The Retina2.7.5. Phototransduction2.7.6. Receptive Fields2.8. Hearing and Equilibrium2.8.1. The Nature of Sound2.8.2. The Hearing Apparatus2.8.3. Sound Vibrations to Action Potentials2.8.4. The Sense of Balance and EquilibriumModule 3.0. Cardiovascular System3.1. Structure of the Heart3.1.1. Chambers and Circulation3.2. Cardiac Cell Action Potentials3.2.1. Action Potentials in Cardiac Muscle Cells3.2.2. Action Potentials in Cardiac Autorhythmic cells3.2.3. Cellular Mechanisms of Inotropy and Chronotropy3.3. Electrophysiology of Heart Muscle3.3.1. Heart Conduction System3.3.2. Electrocardiogram (ECG)3.3.3. Abnormal ECG - Current of Injury3.4. The Cardiac Cycle3.4.1. Cardiac cycle3.4.2. Cardiac Measurements and Pressure Volume Loops3.5. Blood vessels and Blood Pressure3.5.1. Arteries and Veins3.5.2. Capillaries3.5.3. Blood Pressure Regulation and Shock3.5.4. Capillary Exchange3.5.5. Myogenic and Paracrine Regulation of Vasoconstriction and Vasodilation3.6. Blood3.6.1. Composition of Blood3.6.2. Hematopoeisis3.6.3. Breaking Down Red Blood Cells3.6.4. HemostasisModule 4.0. Urinary and Respiratory Systems4.1. Function and Structure of the Kidney4.1.1. Urinary System Function4.1.2. Functional Anatomy of the Urinary System4.1.3. The Nephron: Functional Unit of the Kidney4.1.4. The Renal Corpuscle: Bowman's Capsule4.2. Physiology of Urine Production4.2.1. Filtration4.2.2. Renal Clearance4.2.3. Tubular Reabsorption4.2.4. Urine Concentration and Dilution4.2.5. Hormonal Regulation of Urine Production4.3. Acid/Base Balance4.3.1. Buffers4.3.2. Acid/Base Disturbances4.4. The Respiratory System4.4.1. Respiratory System Structure and Function4.4.2. Respiratory Membrane4.4.3. Respiratory pressures and Inspriation/Expiration4.4.4. Alveoli and Surfactant4.4.5. Pneumothorax4.5. Gas Exchange and Transport4.5.1. Gas Laws4.5.2. Partial Pressure Gradients in the Lung4.5.3. Alveolar Gas Equation4.5.4. Oxygen and Carbon Dioxide Transport in the Blood4.5.5. Alveolar Ventilation4.5.6. Ventilation/Perfusion Ratio4.6. Chronic Bronchitis and Emphysema4.6.1. Respiratory Control by the Medulla Oblongata4.6.2. Chemicals that Regulate VentilationModule 5.0. Digestive, Endocrine and Reproductive Systems5.1. Functional Anatomy of the Digestive System5.1.1. Layers of the Digestive Tract5.1.2. Enteric Nervous System5.1.3. Organs of the Digestive System5.2. Digestion5.2.1. Carbohydrates5.2.2. Proteins5.2.3. Lipids5.2.4. Lipoproteins5.3. Regulation of Digestive Secretions5.4. Endocrine System5.4.1. Overview of the Endocrine System5.4.2. Hormone Receptors5.4.3. Hormones of the Body5.4.4. Other Hormones: Melatonin and Pheromones5.5. The Hypothalamus and Pituitary Gland5.5.1. Structure and Function of the Hypothalamus and Pituitary Gland5.5.2. The Posterior Pituitary5.5.3. The Anterior Pituitary5.5.4. Growth Hormone5.5.5. Prolactin5.5.6. Thyroid Hormones5.5.7. Adrenal Hormones5.6. Pancreas5.6.1. Insulin and Glucagon5.6.2. Diabetes Mellitus5.7. Reproductive System Anatomy5.7.1. Female Reproductive Anatomy5.7.2. Male Reproductive Anatomy5.7.3. Sexual Development at Puberty5.7.4. Male Reproductive Endocrine Axis5.7.5. Spermatogenesis5.7.6. Female Reproductive System: Oogenesis5.7.7. Ovulation and Fertilization5.7.8. The Ovarian Cycle5.7.9. The Uterine Cycle5.7.10. PregnancyAppendix A. GenderAppendix B. The Placebo EffectB.2.1. The Placebo EffectB.2.2. Examples of the Placebo EffectB.2.3. How do Placebos Work?B.2.4. Are Placebos Ethical?B.2.5. How do we validate actual effectiveness of placebosB.2.6. Tips for evaluating scientific evidenceB.2.7. What about Faith Healings

The Posterior Pituitary

Recall that the posterior pituitary is not composed of glandular tissue, rather it is an extension of the hypothalamus. Rather than produce hormones, its function is to store neurohormones that are produced in the hypothalamus. The connection between the hypothalamus and the posterior pituitary is the hypothalamo hypophyseal tract. Neurons in specialized nuclei in the hypothalamus produce neurohormones. The axons of these neurons pass down the hypothalamo hypophyseal tract to the posterior pituitary. The neurohormones are transported in vesicles down the axons to the posterior pituitary where they are stored in the axon terminals. When these same neurons receive the proper signal, they send action potentials down those same axons which stimulate release of the neurohormones in the same way that action potentials in other neurons stimulate the release of neurotransmitters.

The posterior pituitary doesn't actually make any hormones (note: every standardized test will have something like this: true or false, vasopressin is made by the posterior pituitary gland. Don’t choose true!); however, it stores and releases two neurohormones that are synthesized in the hypothalamus. Certain neuron cell bodies located in the hypothalamus produce the hormones which are then transported down the neuron axon the axon terminal located in the posterior pituitary (hypothalamo hypophyseal tract). These neurohormones are then released into the blood in response to the proper stimulus. The two hormones released from the posterior pituitary are antidiuretic hormone (ADH) and oxytocin. Both are small peptides composed of only nine amino acids.

Antidiuretic Hormone
Antidiuretic hormone (ADH), also called vasopressin, is important in regulating the concentration of the body’s extracellular fluids. It is released when the osmolarity of the blood is elevated and stimulates the kidneys to reabsorb water (conserves body water). The role of ADH is discussed in the unit on the kidneys, however, you are responsible to know the actions and effects in this material.


Oxytocin plays a major role in both child birth and milk let down, both of which represent beneficial positive feedback mechanisms. Its role in child birth is to stimulate the uterine smooth muscle to contract. As labor begins and the baby’s head begins to push against the cervix of the uterus stretch receptors are stimulated that signal oxytocin release from the posterior pituitary. The oxytocin stimulates stronger uterine contractions which results in further stretch of the uterus and increased oxytocin release. This results in a positive feedback loop. The cycle is stopped when the baby is born and the cervix is no longer being stretched. Oxytocin's role in release of milk from the mammary glands is similar. Stimulation of the nipples by the nursing baby triggers oxytocin release which results in expulsion of milk from the mammary glands. The stimulus is removed when the baby stops nursing. 

Recent studies suggest that oxytocin plays major roles in both women and men with regard to orgasm, social recognition, pair bonding, anxiety and maternal behaviors. Oxytocin is sometimes referred to as the "bonding hormone". In female rats it has been demonstrated that oxytocin is responsible for triggering maternal behaviors in the new mothers. Additionally, investigators have recently demonstrated a role of oxytocin in moral behavior, showing that oxytocin release increased when people did moral things like: praying, giving money away or serving others. However, other studies have shown that oxytocin release increases during amoral behavior as well, providing the behavior benefits the group the individual belongs to. In the study if a person lied, but the lie benefited the group, oxytocin release increased. Together these results may indicate that oxytocin is not so much a moral hormone, but that it is released during activities that strengthen social ties, be they positive or negative actions. It would appear that there is more to be learned about the precise role of oxytocin as it relates to human behavior.

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