The small intestine is divided into duodenum, jejunum, and ileum, with the duodenum and jejunum being the major site of digestion and absorption. Chyme takes 2 to 4 hours to move through the 5 m of the small intestine. Segmentation, which mixes intestinal contents and enhances contact of the chyme with the intestinal microvilli, is [...]
The peripheral nervous system (PNS) consists of cranial and spinal nerves that connect the CNS to other portions of the body, along with sensory receptors and ganglia. A nerve consists of axons that are bound together by connective tissue. Motor nerves contain mostly axons of motor neurons; sensory nerves contain only axons of sensory neurons; [...]
The colon reabsorbs salts and water. About 1500 mL of fluid enters the colon each day, but only 50 to 100 mL of fluid is excreted in feces. Anatomically, the colon is divided into the cecum, ascending colon, transverse colon, and descending colon. Segmental contraction of the circular smooth muscle divides the colon into numerous [...]
The ANS is a major mechanism for neural control of physiologic functions. The autonomic nervous system (ANS) consists of portions of the central and peripheral nervous systems and functions without conscious control. Discussions of ANS usually take one of three perspectives: An anatomic perspective based on structure, A physiologic perspective based on function, A pharmacologic [...]
During the latter stages of pregnancy, the blood concentration of estrogens become increasingly greater than that of progesterone, as noted earlier. Whereas progesterone inhibits uterine contractions, estrogens promote them. Therefore, there is an increasing tendency toward the onset of uterine contractions as the pregnancy approaches full term. These uterine contractions are often referred to as [...]
Inflammatory Disorders Meningitis (men-in-ji '-tis) results from a bacterial, fungal, or viral infection of the meninges. Bacterial meningitis cases are the most serious, with about 20% being fatal. If the brain is also involved, the disease is called encephalitis. Some viruses causing encephalitis are transmitted by bites of certain mosquitoes. Neuritis is the inflammation of [...]
CSF = cerebrospinal fluid It is quite similar to blood plasma and interstitial fluid. It's present in the ventricular system inside the CNS and in the subarachnoid space surrounding the CNS. It gives a protective cushion between the CNS and the neighboring bones and bathes both the external and internal surfaces of the brain and [...]
Homeostasis, a term presented by W. B. Cannon, describes the mechanism by which the constancy of the internal environment is maintained and ensured Homeostasis is the maintenance of a fairly steady internal environment by self-regulating physiological processes Homeostasis keeps body temperature and the structure of blood and interstitial fluids within their regularrange This fairly steady [...]
Sensory receptors for the general senses are widely distributed in the skin, muscles, tendons, ligaments, and visceral organs. Temperature Two types of thermoreceptors are located in the skin. Warm receptors are free nerve endings, which are sensory neuron dendrites, in the deep dermis that are most sensitive to temperatures above 25 °C (77°F). Cold receptors [...]
Neurons come in numerous sizes. For instance, a single sensory neuron from your fingertip has an axon that spreads out the length of your arm, while neurons within the brain may extend just a couple of millimeters. They also have different shapes depending upon their functions. Motor neurons that regulate muscle contractions have a cell [...]