Nervous+System+Reading+-+Rachel

Nervous System Reading (How does the body respond to a stimulus?) Answer the following questions in complete sentences and on the wiki (and note that question tells you where to find the answer). A question may need several sentences to answer completely and in such way that you understand the answer. WRITE THE QUESTION TOO.: p. 17 #2 What is homeostasis, and how is it maintained? Give some examples that show how systems work together to maintain homeostasis. (pg 4-5) Homeostasis is defined as the maintenance of normal internal conditions in a cell or an organism by means of self-regulating mechanisms. For example all the systems in the body work together like a cycle to maintain homeostasis; the digestive system gathers the nutrients while the respiratory exchanges environmental gases. The nutrients and oxygen are then distributed to the cells and the waste is collected by the cardiovascular system. Then the urinary system collects the metabolic waste, the proper functioning of this cycle is extremely dependent on the both the nervous and endocrine systems. Another examples of the how the body maintains homeostasis is its ability to maintain a normal internal temperature either by shivering or sweating.

p. 83 #7, 11 7. Explain why the skin is sometimes referred to as the integumentary system. (pg71) An organ is composed of two or more types of tissues performing particular functions within the body. Skin if comprised of four different tissue types epithelial, connective, muscle, and nervous. Hair, nails, sweat glands, and sebaceous glands are considered accessory organs explaining why skin is sometimes referred to as the integumentary system.

11. Why is homeostasis defined as the "relative constancy of the internal environment?" Does negative feedback or positive feedback tend to promote homeostasis? Explain. (pg 78-81) All systems of the body contribute to maintain homeostasis or the normal internal conditions. Homeostatic mechanisms have two components: a senor and a control center. Negative feedback is the primary mechanism that keeps a variable to a set point, they are present when the output of the system dampens the original stimulus. Positive feedback can be harmful because it brings about greater change in the same direction. For example when a fever causes metabolic changes the positive feedback will push the fever higher. But sometimes such as during childbirth a positive feedback can assist the body in completing a process that has a definite cut-off point.

p. 245 #9 9. How does the muscular system help maintain homeostasis? (pg 242-43) Movement is essential to maintaining homeostasis. Body movement of this sort allows us to respond to certain types of changes in the environment. Simply put every movement the body makes is through the muscular and skeletal systems everything from contraction of the jaw and tongue (in order to eat food), to the muscles used for digestion, to bones producing red blood cells, to heat production allowing the body to stay at a constant temperature, to even breathing.

p. 271 #1, 2 1. What are the three functions of the nervous system? (pg248) The nervous system has two major divisions the central nervous system (CNS) and the peripheral nervous system (PNS). The three specific functions of the nervous system are reception of input, integration of data, and generating motor outputs.
 * The nervous system receives sensory input - sensory receptors respond to external and internal stimuli by generating nerve impulses that travel by way of the PNS to the CNS.
 * The CNS performs integration, summing up the input it receives from all over the body.
 * The CNS generates motor output - nerve impulses from the CNS go by way of the PNS to the muscles and glands.

2. What are the functions performed by the three types of neurons? Describe the structure and functions of the three parts of a neuron? (pg249) Neurons are the cells that transmit nerve impulses between parts of the nervous system, there are three types: sensory, interneurons, and motor. Varying in appearance, neurons all have the same three parts: a cell body which contains the nucleus and other organelles; dendrites recieve signals from sensory receptors on many short extensions; and an axon produces the nerve impulses that the dendrites receives. Sensory neurons take nerve impulses from sensory receptors, which detect changes in the environment to the CNS. Interneurons are located within the CNS and receive input from sensory neurons and other interneuron in which they sum up and send to the motor neurons. Finally the motor neurons take the nerve impulses away from the CNS to an effector (muscle fiber or gland), which carry out the initial response to the environmental changes (made by the sensory neurons).

p. 293 #1, 4 1. Contrast exteroceptors and interoceptors. (pg274) Exteroceptors are sensory receptors that detect stimuli from outside the body, such as taste, smell, vision, hearing, and equilibrium. However those in the eyes and ears are not directly involved in homeostasis are are constantly communicating with the central nervous system in regards to environmental changes. Interoceptors receive stimuli from inside, such as pressoreceptors which respond to blood pressure these are directly involved in homeostasis and are regulated by a negative feedback mechanism.

4. List the cuntaneous receptors and the type of stimulus each responds to. (page 276-77) Skin is made of two layers the epidermis and the dermis. Within the dermis are cutaneous receptors, making the skin sensitive to touch, pressure, pain, and temperature. There are three types of receptors sensitive to touch: Receptors sensitive to pressure are the Pacinian corpuscles located deep in the dermis and Ruffini endings contain lacy networks of nerve fibers which are encapsulated by connective tissue. Free nerve endings in the epidermis are temperature receptors, cold and warm receptors have the same structure but there are more cold ones than warm. Pain receptors or nocieptors are sensitive to chemicals released by damaged tissues (pain receptors are not solely within skin, but throughout many internal organs).
 * 1) The Meissner corpuscles (or Krause end bulbs) located in the fingertips, palms, lips, tongue, nipples, penis, and clitoris.
 * 2) The Merkel disks located at the joining of the epidermis and dermis.
 * 3) Root hair plexus which are around the base of hair follicles (and are flammable).