Human Anatomy and Physiology II

In this lesson, we will explore the topic of sensation as you learn about the sensations of touch, pressure, temperature, and pain. You will discover the differences between free nerve endings, Merkel disks, Meissner corpuscles, root hair plexuses, and Pacinian corpuscles. We will also talk about sensory adaptation and referred pain. You will learn where in the brain messages from sensory receptors end up. We will end the lesson by discussing three disorders of cutaneous sensation—tactile defensiveness, congenital insensitivity to pain, and peripheral neuropathy. 

In this lesson, you will learn about sensory receptors (muscle spindles, Golgi tendon organs, and joint proprioceptors) that tell your brain how much tension is in your muscles and the position of your body parts. You will learn why accurate information from these receptors is essential and how the brain uses it to help you plan your movements. We will also discuss the sense of equilibrium—that sense that lets you know if you're upright and if you're in danger of falling. You will study the structures of the vestibular system and learn how they contribute to both static and dynamic equilibrium. The end of the lesson will let you know what happens when a person experiences proprioceptive or vestibular dysfunction. 

Now it's time to learn about the physics of light and color and find out how light is bent and focused. In this lesson, you will learn about the composition of the eyes, including their three coverings and the structures inside the eyeballs. We will talk about special sensory receptors called rods and cones and how the information they receive is sent to the brain and analyzed. We will end this lesson by discussing three common eye disorders—glaucoma, cataracts, and macular degeneration. 

In this lesson, you will discover the physics of sound. You will learn why sounds differ in pitch and loudness, and you will find out about a quality of sound called color. We will then talk about the different structures that make up the outer ear, middle ear, and inner ear. You will learn what happens when sound waves enter the ear and how information from the ear travels to the brain for analysis. We will end this lesson with a discussion of hearing loss. 

In this lesson, we will finish our study of the senses by discussing the senses of smell and taste. You will learn about the structures that respond to chemicals of smell and taste and how the brain perceives smell and taste sensations. We will also talk about disorders of both of these senses, and you will have an opportunity to perform a fun experiment to test the importance of smell to the perception of flavor. 

In this lesson, we will go over the fascinating topic of cellular metabolism—the chemical reactions that occur in your body's cells. We will review the essential concepts of homeostasis and negative feedback. You will learn that homeostasis is maintained by thousands of chemical reactions that occur every second. Those chemical reactions either build larger molecules from smaller ones or break apart larger molecules into smaller ones, so we will discuss what happens in those two major types of reactions. You will also learn about the capture and storage of energy, the role of enzymes in metabolic pathways, and disorders of cellular metabolism. 

In this lesson, we will continue our study of essential chemicals in the human body. We will start by reviewing the differences between atoms and ions and between ionic and covalent bonds. We will then move on to a study of water, its unique properties, and its essential functions. You will learn that water breaks apart molecules called electrolytes and that the three major types of electrolytes include acids, bases, and salts. We will discuss the pH scale—a way to measure a substance's acidity degree; you will learn about the conditions called acidosis and alkalosis. We will finish the lesson by discussing imbalances of three essential ions—sodium, potassium, and calcium. 

In this lesson, you will go over the wonders of prenatal development. You will learn about the roles both parents play in the creation of the zygote—the very first cell that starts a new human life. You will then follow that new creature through the amazing changes that happen during the first eight weeks after fertilization (the embryonic period). The lesson will also discuss significant events that occur during the rest of the pregnancy (the fetal period). At the end of this lesson, you will learn about some common causes of infertility.

In this lesson, you will learn about pregnancy from the childbearing parent's point of view. The lesson will start with a discussion about the placenta and then talk about the way pregnancy affects the pregnant parent's different organ systems. It will also discuss the events of childbirth and what occurs during the postpartum period. Many childbearing parents choose to breastfeed (lactate), so this lesson will also tell you how breasts prepare for lactation, how milk is produced, and how it's secreted. You will end this lesson with a discussion of a complication of pregnancy called gestational diabetes.

This lesson will focus on the neonatal period, infancy, and childhood. We will start with a discussion of the normal circulation of blood in children and adults and compare that to circulation in the fetus. This will help you understand the significant changes in the heart, blood vessels, and lungs as soon as babies take their first breaths. We will then talk about other changes in the first four weeks after birth (the neonatal period), and we will discuss reflexes and brain maturation during the first year. We will also discuss some significant changes that occur during childhood. At the end of this lesson, you will learn about a common developmental disorder in children called cerebral palsy. 

In our final lesson, we will go over puberty, adulthood, and late adulthood. You will learn how hormones work during puberty and what physical changes occur. We will also discuss changes that occur during the young adulthood and middle age years and then spend some time on menopause. We will devote a chapter to senescence—the aging process for those 65 and over. In that chapter, you will learn why getting older causes age-related changes. We will end this lesson by discussing ways to slow the aging process.