Chapter 4

Which morphological adaptions of neurons make them suitable for the transmission of nerve impulse?

Neurons are well suited for the transmission of nerve impulses because short extensions, dendrites, receive impulses from other neurons, while a long tail extension, an axon, carries electrical impulses away from the cell to other neurons.

Why does an injury to cartilage, especially hyaline cartilage, heal much more slowly than a bone fracture?

A layer of dense irregular connective tissue covers cartilage. No blood vessels supply cartilage tissue. Injuries to cartilage heal very slowly because cells and nutrients needed for repair diffuse slowly to the injury site.

Discuss changes that occur in a cell as a person ages.

All cells experience changes with aging. They become larger, and many cannot divide and regenerate. Because of alterations in cell membranes, transport of oxygen and nutrients into the cell and removal of carbon dioxide and waste products are not as efficient in the elderly. Cells lose their ability to function, or they begin to function abnormally, leading to disease and cancer.

What are the functions of astrocytes?

Astrocytes regulate ions and uptake and/or breakdown of some neurotransmitters and contribute to the formation of the blood-brain-barrier.

One of the main functions of connective tissue is to integrate organs and organ systems in the body. Discuss how blood fulfills this role.

Blood is a fluid connective tissue, a variety of specialized cells that circulate in a watery fluid containing salts, nutrients, and dissolved proteins in a liquid extracellular matrix. Blood contains formed elements derived from bone marrow. Erythrocytes, or red blood cells, transport the gases oxygen and carbon dioxide. Leukocytes, or white blood cells, are responsible for the defense of the organism against potentially harmful microorganisms or molecules. Platelets are cell fragments involved in blood clotting. Some cells have the ability to cross the endothelial layer that lines vessels and enter adjacent tissues. Nutrients, salts, and waste are dissolved in the liquid matrix and transported through the body.

The structure of a tissue usually is optimized for its function. Describe how the structure of individual cells and tissue arrangement of the intestine lining matches its main function, to absorb nutrients.

Columnar epithelia, which form the lining of the digestive tract, can be either simple or stratified. The cells are long and narrow. The nucleus is elongated and located on the basal side of the cell. Ciliated columnar epithelium is composed of simple columnar epithelial cells that display cilia on their apical surfaces.

Aspirin is a non-steroidal anti-inflammatory drug that inhibits the formation of blood clots and is taken regularly by individuals with a heart condition. Steroids such as cortisol are used to control some autoimmune disease and severe arthritis by down-regulating the inflammatory response. After reading the role of inflammation in the body's response to infection, can you predict an undesirable consequence of taking anti-inflammatory drugs on a regular basis?

Since NSAIDs or other anti-inflammatory drugs inhibit the formation of blood clots, regular and prolonged use of these drugs may promote internal bleeding, such as bleeding in the stomach. Excessive levels of cortisol would suppress inflammation, which could slow the wound healing process.

What is the function of synovial membrane?

Synovial membranes are a type of connective tissue membrane that supports mobility in joints. The membrane lines the joint cavity and contains fibroblasts that produce hyaluronan, which leads to the production of synovial fluid, a natural lubricant that enables the bones of a joint to move more freely against one another.

You are watching cells in a dish spontaneously contract. They are all contracting at different rates; some fast and some slow. After a while, several cells link up and they begin contracting in synchrony. Discuss what is going on and what type of cell you are looking at.

The cells in the dish are cardiomyocytes, cardiac muscle cells. They have an intrinsic ability to contract. When they link up, they form intercalating discs that allow the cells to communicate with each other and begin contracting in synchrony.

Identify the four major types of tissue in the body, and describe the major functions of each tissue.

The four types of tissues in the body are epithelial, connective, muscle, and nervous. Epithelial tissue is made of layers of cells that cover the surface of the body that come in contact with the exterior world, line internal cavities, and form glands. Connective tissue the cells and organs of the body together and performs many functions, especially in the protection, support, and integration of the body. Muscle tissue, which responds to stimulation and contracts to provide movement, is divided into three major types: skeletal (voluntary) muscle, smooth muscle, and cardiac muscle in the heart. Nervous tissue allows the body to receive signals and transmit information as electric impulses from one region of the body to another.

As an individual ages, a constellation of symptoms begins the decline to the point where an individual's functioning is compromised. Identify and discuss two factors that have a role in factors leading to the compromised situation.

The genetic makeup and the lifestyle of each individual are factors which determine the degree of decline in cells, tissues, and organs as an individual ages.

The zygote is described as totipotent because it ultimately gives rise to all cells in your body including the highly specialized cells of your nervous system. Describe transition, discussing the steps and processes that lead to these specialized cells.

The zygote divides into many cells. As these cells become specialized, they lose their ability to differentiate into all tissues. At first they form the three primary germ layers. Following the cells of the ectodermal germ layer, they too become more restricted in what they can form. Ultimately, some of these ectodermal cells become further restricted and differentiate in to nerve cells.

Why is it important to watch increased redness, swelling, and pain after a cut or abrasion has been cleaned and bandaged?

These symptoms would indicate that infection is present.

Why does muscle tissue look striated?

Under the light microscope, cells appear striated due to the arrangement of the contractile proteins actin and myosin.