Stress

Stress

Homeostasis ensures survival. When danger is sensed, the hypothalamus triggers physiologic responses, which include increased sympathetic activity and increased secretion of adrenal and other hormones. A factor stim-ulating this type of response is a stressor and the condi-tion it produces is stress. Many stresses are opposed by specific homeostatic changes. For example, when body temperature declines, it leads to shivering and changes in the pattern of blood flow. This can restore normal body temperature.

The body also has a general response to stress that occurs while other, more specific responses are under way. When exposure to a wide variety of stress-causing factors occurs, it produces the same general pattern of hormonal and physiologic changes. These responses are part of the general adaptation syndrome that is also known as the stress response.

Physical factors and psychological factors both can produce stress. Physical factors include tempera-ture changes, decreased oxygen concentration, infec-tions, injuries, prolonged exercises, and loud sounds. Physiological factors include real or imagined dangers, personal loss, and unpleasant social situations. Psy-chological stressors also include anger, fear, anxiety,­ depression, grief, and guilt. Positive stimuli can also be stressful in certain situations.

The hypothalamus controls the stress response as part of the general adaptation syndrome. Reac-tions occur in either the immediate “alarm” stage or the longer term “resistance” stage. The hypothalamus­ first prepares the body for the fight-­ or-flight syndrome by raising blood glucose, glyc-erol, and fatty acids and by increasing heart rate, blood ­pressure, and breathing rate. It dilates the air passages, moves blood from the skin and diges-tive organs to the skeletal muscles, and increases epinephrine­ secretion from the adrenal medulla (FIGURE 16-19).

The resistance response involves the release of CRH to stimulate the secretion of ACTH, which stim-ulates cortisol secretion. This increases blood amino acids, release of fatty acids, and glucose formation. The body is being prepared for physical action to alleviate the stress. Energy sources are mobilized and blood volume is increased, which is important during bleeding or heavy sweating.

The hypothalamus controls the stress response as part of the general adaptation syndrome. Reac-tions occur in either the immediate “alarm” stage or the longer term “resistance” stage. The hypothalamus­ first prepares the body for the fight-­ or-flight syndrome by raising blood glucose, glyc-erol, and fatty acids and by increasing heart rate, blood ­pressure, and breathing rate. It dilates the air passages, moves blood from the skin and diges-tive organs to the skeletal muscles, and increases epinephrine­ secretion from the adrenal medulla (FIGURE 16-19).

The resistance response involves the release of CRH to stimulate the secretion of ACTH, which stim-ulates cortisol secretion. This increases blood amino acids, release of fatty acids, and glucose formation. The body is being prepared for physical action to alleviate the stress. Energy sources are mobilized and blood volume is increased, which is important during bleeding or heavy sweating.

1. What hormones are secreted by the placenta, thymus gland, and stomach?

2. List the hormones produced from the adipose tissue, skin, heart, and skeleton.

3. What are the functions of glucagon?

4. What hormones are released by the digestive glands (stomach and small intestine)?