Blood Vessels
[Figure 1] How does blood travel around the body? Through blood vessels, of course. This image of veins is from William Harvey’s (1578-1657) Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus. Harvey was the first to describe in detail the systemic circulation and properties of blood being pumped to the brain and body by the heart. Blood Vessels Blood vessels form a network throughout the […]
Heart
[Figure 1] What’s the hardest working muscle in the body? The human heart. An absolutely remarkable organ. Obviously, its main function is to pump blood throughout the body. And it does this extremely well. On average, this muscular organ will beat about 100,000 times in one day and about 35 million times in a year. During an average […]
Endocrine System Diseases
[Figure 1] How tall can a person become? This may be an exaggeration, but the world’s tallest person, Robert Pershing Wadlow, stood almost nine feet tall when he died at the age of 22. Is growing that tall due to a problem with the endocrine system? Endocrine System Disorders Diseases of the endocrine system are relatively […]
Hormone Regulation
[Figure 1] On or off? Hormones alter conditions inside the cell, usually in response to a stimulus. That means they are activated at specific times. So they must be turned on and then turned back off. What turns these hormones and their responses on or off? Hormone Regulation: Feedback Mechanisms Hormones control many cell activities, so they are […]
Hormone
[Figure 1] Steroid hormones. How do they work? As hormones, they are the messengers of the endocrine system. Obviously they must change something in the cell. How Hormones Work Hormones are the messenger molecules of the endocrine system. Endocrine hormones travel throughout the body in the blood. However, each hormone affects only certain cells, called target cells. A target cell is the […]
Endocrine Glands
[Figure 1] What’s a hormone? This messenger pigeon is delivering a letter, making sure it gets to where it needs to go. It could be said that hormones are biological messengers, and they originate from the endocrine system. The nervous system isn’t the only message-relaying system of the human body. The endocrine system also carries messages. The endocrine system is a […]
Nervous System Diseases
[Figure 1] Ever had a headache that just won’t go away? We all get headaches. Headaches are a relatively minor problem associated with the nervous system. But what about more serious issues of the nervous system? As you can probably imagine, these can be extremely serious. Disorders of the Nervous System There are several different types […]
Drugs and the Nervous System
[Figure 1] Is coffee a drug? Maybe. But that doesn’t necessarily mean it is bad for you. Looks tasty, though. Other than taste, why do many people have a cup of coffee in the morning? Does it help them wake up? For many people, it does. Why? The caffeine in the coffee stimulates the central nervous system. This drug is one […]
Senses
[Figure 1] Name the five senses. Hearing, sight, taste, touch, and smell. But how do we hear, see, taste, touch and smell? It all has to do, obviously, with the nervous system. The Senses The sensory division of the peripheral nervous system (PNS) includes several sense organs—the eyes, ears, mouth, nose, and skin. Each sense organ has special cells, called sensory receptors, that respond to a particular type […]
Peripheral Nervous System
[Figure 1] How does the signal get to your toes? If the brain controls practically everything, how does the signal get to your toes? Or your legs? Or arms? By way of the peripheral nervous system, or all the nerves shown here other than the brain and spinal cord. Notice how they go everywhere. Peripheral Nervous System The peripheral nervous system […]
