Positive and Negative feedback

Explain how high or low blood pressure affects capillary blood flow.

A decrease in pressure would decrease pressure in the capillary and therefore reduce flow providing an inadequate amount of blood; high pressure may overstretch the capillary wall and cause bursting.

How is homeostasis maintained under cold stress? (include: heat-producing center, capillary constriction, shivering)

A neuron group in the anterior portion of the hypothalamus controls heat balance. Neurons in the per-optic area of the hypothalamus integrate signals that arise from thermoreceptors. The skeletal muscles receive signals to shiver which will produce additional heat. Blood vessels in the skin receive signal to constrict decreasing blood flow of warm blood to the body's periphery. Heat production is increased while heat loss is minimized and temperature homeostasis is restored.

Explain the negative feedback control of body temperature using thermoreceptors, the hypothalamus, and the temperature control center.

A neuron group of the anterior portion of the hypothalamus controls heat balance. Neurons in the pre-optic areas of the hypothalamus integrate signals that come from thermoreceptors. The control center in the pre-optic area propagates control signals to other areas in the hypothalamus that control heat loss and heat production. When overheating occurs the control center in the pre-optic area inhibits the heat-promoting center and stimulates the heat loss center.

Describe the importance of homeostatic body temperature maintenance?

Temperature that rises too high or drops too low causes different disorders like cardiac arrhythmias. Temperature is maintained by balancing the loss to the environment with the rate that is produced by the body.

Explain the negative feedback loop between baroreceptors, the cardiovascular (CV) center, and the heart. Address: dropping blood pressure, heart stimulation, and hormonal vessel constriction. How do these all work together to achieve homeostasis?

The baroreceptors (sensor), cardiovascular center (control center) and the heart (effector) is part of a negative feedback mechanism controlling blood pressure. A drop in blood pressure is sensed by baroreceptors which send impulses to the the cardiovascular center in the brain. The brain then sends signals to increase heart rate and constrict blood vessels, resulting in an increase in blood pressure. A response that decreases or eliminates the original stimulus is a negative feedback system.

How is this positive feedback loop terminated?

The birth of the child reduces and eliminates the stimuli to the pressure sensitive receptor cells. Without any stimuli impulses cease to the hypothalamus and there is no longer a production of Oxytocin.

What is the function, and locations, of thermoreceptors?

Thermoreceptors are found throughout the body detecting changes in body temperature. They detect increases and decreases in temperature and send this information to the brain via impulses.

How is homeostasis maintained under heat stress? (Include heat-losing center, capillary dilation, and sweat production.)

Thermoreceptors sense the increased temperature and send signals to the hypothalamus. Upon receiving signals from the temperature control centers in the hypothalamus, blood vessels in the skin dilate and more blood is channeled to regions near the skin surface where it can be cooled. Sweat glands are also stimulated to produce perspiration that cools the skin when it evaporates.

What is the function of baroreceptors

These structures are receptors that monitor pressure and are located in the aortic arch and carotid arteries. They sense the stretching of the vessel and upon stimulation will send impulses to the regulatory centers in the brain.

What starts the positive feedback loop of childbirth labor?

This cycle begins when the child enters the cervix and stretches the muscle wall..

Describe the positive feedback loop between cervical stretch receptors, neurosecretory cells in the hypothalamus, Oxytocin, and the uterine smooth muscle.

When the child enters the cervix it stretches, or dilates, and labor begins. Pressure sensitive receptor cells of the cervix detect the stretch and send impulses to the brain. These impulses go to the neurosecretory cells of the brain where a hormone called oxytocin is released into the capillaries of the pituitary gland. The blood then carries the hormone to the uterine tissue. Oxytocin causes the smooth muscle tissue of the uterine wall to contract more forcefully and pushes the child further into the cervix. This stretches the cervical wall further and sends more impulses to the hypothalamus. The cycle is continued with greater speed until the cervix is fully dilated and the child is born.