Introduction to Physiology Homeostasis Dynamic Study Module

When blood glucose levels increase, the beta cells of the pancreas will sense this increase and release insulin, which will target the liver and cells of the body in order to bring glucose levels back down within homeostatic range. What role does the pancreas play in this homeostatic control pathway?

Effector only Sensor only Integrator, sensor, and effector Integrator only Integrator and sensor ---Answer Integrator and effector

Which of the following statements about homeostasis is false?

Internal changes can result in loss of homeostasis. Blood glucose regulation is not an example of homeostatic regulation.--Answer Integrating centers play a role in maintaining homeostasis. Failure to maintain homeostasis may result in a pathological condition.

The increased blood glucose concentrations that occur with diabetes can be detected or monitored by measuring __________.

levels of hemoglobin A1c blood glucose levels all answers are correct ---answer urine glucose levels

As a result of exercise training, which of the following decreases?

Muscle mass of the ventricle Resting heart rate ---Answer Bone density

Negative feedback info

Negative feedback moves a physiological variable back to its set point. Feedback is a very important aspect of homeostatic control. In order for the body to adjust for changes in physiological variables, the body must employ different types of feedback. Negative feedback will be employed when a physiological variable needs to be reestablished or brought back within its normal physiological range. For example, if blood pressure increases outside of the normal physiological range, then negative feedback will bring blood pressure back down to normal. It is true that negative feedback loops will move a physiological variable in the direction opposite of the error signal, thereby reducing the error signal. These changes, however, do not move the physiological variable past the set point. Instead, the physiological variable moves back toward the set point. Negative feedback loops will not increase the amplitude of the error signal. Instead, negative feedback will work to keep the error signal as small as possible. Only one of the above answers is correct with regard to negative feedback.

Secretion of pepsinogen into the stomach in response to an increase in stomach acidity is an example of what type of response?

Positive feedback ---answer Fast forward feedback Not a homeostatic response Negative feedback

__________ allows the body to predict that a change is about to occur and start the response loop in anticipation of the change.

Positive feedback loop Feed forward control ---answer Negative feedback loop Homeostatic imbalance

positive feedback info 2

Positive feedback loops are prevented from spiraling out of control because of all of the given answers. Eventually, all positive feedback loops will be stopped by certain factors that will make the feedback loop stop. These things can be other signals that prevent the positive feedback loops from continuing to run. Positive feedback loops can be stopped once the stimulus is removed. An example of this occurs in child birth. The initial stimulus for the release of oxytocin from the posterior pituitary is pressure on the cervix. As pressure on the cervix increases, the amount of oxytocin released increases further. Once the baby is delivered, the pressure on the cervix is no longer present and therefore the positive feedback loop that causes the increased release of oxytocin has now stopped. Factors that limit the system's ability to respond to the stimulus or events from outside the loop that remove the stimulus will eventually lead to the removal of the positive feedback loop. It is essential for this to occur in order to prevent the change in the variable from spiraling out of control.

Which of the following is true with regard to physiological control systems?

Positive feedback will always lead to excessive damage. Negative feedback loops are more common that positive feedback loops in living systems. Negative feedback loops are homeostatic; positive feedback loops are not. --Answer All of the body's variables are under the control of negative feedback loops. All variables will always be maintained at a constant value.

During exercise, blood flow to which of the following organs cannot be restricted without doing harm?

Skin Digestive tract Brain ---Answer Skeletal muscle

Which of the following represents the correct sequence of events from the stimulus to the target tissue?

Stimulus input (efferent) signal integrating center output (afferent) signal target response Stimulus input (afferent) signal output (efferent) signal integrating center target response Stimulus, input (afferent) signal, integrating center, output (efferent) signal, target response ---Answer Stimulus output (efferent) signal integrating center input (afferent) signal target response

Teleological study info

Teleological study of human physiology answers the "how" of the system is a false statement. A teleological explanation answers the why of a system. For example, why do we breath? The teleological answer to this question would be: because we need oxygen. The how answer would be the mechanistic explanation and would explain the steps involved with moving air into the lungs. A very large percentage of cells in the body are in contact with the external environment. All of your epithelial cells that line the body cavities as well as make up the integument touch the external environment. This would include all cells that line the lumens of the respiratory tract, digestive tract, urinary tract, and reproductive tract. Despite that, a relatively small percentage of your body's cells are in direct contact with the outside environment. Homeostasis is an important process in the body. Homeostatic control pathways ensure that physiological variables do not range outside of the set point. This prevents the development of pathologies. Cells of the body will communicate with the external environment through a biological membrane. Recall that all cells are surrounded by a phospholipid bilayer. In order for things to enter or leave the cell, the substances must first cross through these membranes. Cell-to-cell communication depends on chemical signaling molecules such as neurotranmitters or hormones. These processes are important in the regulation of homeostatic control pathways.

Which of the following statements is false?

Teleological study of human physiology answers the "how" of the system. --answer A large percentage of living cells of the body are in direct contact with the external environment. Homeostasis is an important process in the body. Most cell-to-cell communication uses chemicals. Communication of a cell to the outside world occurs across the cell membrane.

when glucose levels increase info

When blood glucose levels increase, the beta cells of the pancreas will sense this increase and release insulin, which will target the liver and cells of the body in order to bring glucose levels back down within homeostatic range. The beta cells of the pancreas are acting as both the integrator and sensor. Recall what the roles of the sensor and integrator are. The sensor is sensitive to changes in the physiological variable while the integrator will interpret signals delivered by the sensory pathways and generate an efferent signal. In this case the beta cells sense the change in blood glucose, integrate that blood glucose levels are high, and release insulin as the hormone that functions as the efferent pathway. It is true that the pancreas functions as an integrator because it produces an efferent signal in response to the change in blood glucose levels, but it is not the only role that the pancreas in playing. The pancreas does function as a sensor because it is sensitive to changes in blood glucose levels. The pancreas also responds to those changes in blood glucose levels, making it more than just the sensor. Effectors are target organs of the efferent pathways initiated by the integrator. These effectors are usually glands and organs that will produce responses in order to change the physiological variable. In this scenario, the pancreas is not functioning as an effector. It is true that the pancreas functions as an integrator because it produces an efferent signal in response to the change in blood glucose levels, but it is not functioning as an effector. Effectors are target organs of the efferent pathways initiated by the integrator. These effectors are usually glands and organs that will produce responses in order to change the physiological variable. The pancreas is functioning as a sensor and an integrator in this scenario, but it does not function as an effector. Effectors are target organs of the efferent pathways initiated by the integrator. These effectors are usually glands and organs that will produce responses in order to change the physiological variable

The organ system that provides the least contribution to maintaining organismal homeostasis is the __________ system.

cardiovascular renal digestive reproductive --Answer

Negative feedback __________.

does all of the given answers increases the amplitude of the error signal moves a physiological variable that has deviated from the set point back toward the set point --Answer moves a physiological variable past the set point, in a direction opposite to the error signal

Which of the following is the definition of a stimulus?

A detectable disturbance or change in the internal or external environment ---Answer Something that compares the input signal with the set point Electrical and/or chemical signal that travels to the target Something that monitors its environment for a particular variable

Drop in blood pressure info

A drop in blood pressure that occurs when a person stands up too quickly is an error signal. Error signals occur when the physiological variable ranges outside of its set point. Because blood pressure in this case is dropping below its normal value, an error signal will be initiated to activate negative feedback loops. All homeostatically controlled physiological variables have a set point, or a value which they fluctuate around. A regulated variable is any physiological variable that is controlled and maintained within or around a set point. Some examples of regulated variables include heart rate, blood pressure, body temperature, and blood pH.

Which of the following is the correct definition of positive feedback?

All answers are incorrect A.)A regulated variable increases, and the system responds by making it decrease. b)The response of the system goes in the same direction as the change that sets it in motion. ---Answer C)A response is carried out before the variable changes in anticipation of the change that will occur.

Integrators info

All of the given answers can function as integrators. Recall that an integrator is the portion of a homeostatic control pathway that will interpret the signals that come from sensory pathways. The integrator can be anything that functions to interpret signals and produce efferent pathways. The brain is an integrator that can release neurotransmitters that will stimulate efferent pathways. But it is not the only option listed that can function as an integrator. An endocrine gland can function as an integrator by initiating efferent pathways with the release of a hormone. It is not, however, the only option listed that functions as an integrator. Although a small structure, endocrine cells (like the beta cells in the pancreas) can function as integrators. This is not the only option, however, that functions as an integrator. Neurons are some of the smallest structures that can function as integrators. Integration occurs primarily at the cell body where sensory signals coming in are interpreted. It is not, however, the only option listed that functions as an integrator.

body's controlled variables info

All of the variables listed are controlled variables in the body. A normal body temperature is necessary for maintenance of metabolic rates. If body temperature increases above normal, metabolic processes could occur too quickly, leading to tissue toxicity. If body temperature is too low, metabolic rates will be so slow that cells and tissues will not be able to function properly. Heart rate will fluctuate depending on the metabolic needs of the body. For this reason, the body needs to be able to increase and decrease heart rate accordingly. If you are exercising, your working muscle will need more oxygen and this can be accomplished by increasing heart rate. Blood pressure is an important variable to maintain as it provides the driving pressure of the blood, allowing it to flow unidirectionally throughout the cardiovascular system. If blood pressure is too low, it is possible that the vital organs may not be receiving adequate amounts of blood for proper oxygenation and nutrient delivery. Although a high blood pressure may not pose an immediate threat to the body, it will lead to an increase in the risk of developing cardiovascular disease. Blood pH is maintained within very narrow limits. Any fluctuation in blood pH can be potentially lethal as it can lead to overexcitability or depression of the nervous system. Respiratory rate is altered to meet the metabolic demands of the body as well as to correct imbalances of gas concentrations in the blood and for regulating pH.

Which of the following represents the most complicated control pathway in homeostatic systems?

An efferent pathway that includes an endocrine organ as an integrator An efferent pathway that consists of one neuron An integrator having an effect on multiple target tissues An efferent pathway that includes a neuron, an endocrine gland functioning as an integrator, and a target tissue ---Answer An efferent pathway that includes a two-neuron relay before the target cell is stimulated

Which of the following can function as integrators?

An endocrine gland The brain A neuron All answers are correct --Answer An endocrine cell

as a result of exercise info

As a result of exercise training, resting heart rate can decrease. With aerobic training, the cardiac muscle can hypertrophy, leading to more forceful contractions. The higher blood volume accommodation coupled with an increase in contractile force results in higher stroke volumes. This allows the heart to produce the same cardiac output at a reduced heart rate when compared to the heart that is not trained. Weight-bearing exercises can increase bone density. This change in bone density is often necessary to provide the muscles with a strong frame to work with to accomplish the tasks that are being demanded of the body. Trained atheletes frequently develop ventricular hypertrophy (enlarged ventricles), which allow a greater stroke volume and increase in cardiac output. At least one of the options is correct.

Homeostasis info

Blood glucose regulation is not an example of homeostatic regulation is a false statement with regard to homeostasis. Blood glucose levels are controlled by negative feedback loops. When blood glucose levels increase, the pancreas will release insulin. Insulin is responsible for mediating glucose uptake by the liver and the tissues of the body, which will eventually reduce blood glucose levels and bring glucose levels back to their homeostatic set point. When feedback loops fail to correct a change in a physiological variable, the variable will continue to range outside of its set point and will eventually lead to pathology. This occurs when blood pressure fails to drop to its original set point after it has increased. Over time, a high, uncorrected blood pressure can lead to heart and renal failure. Internal changes can lead to a disruption in homeostasis. An example of this is a change that can occur in the extracellular fluid. More specifically, an increase in the sodium concentration within the plasma will disrupt the homeostatic balance of osmotic pressure across the body's fluid compartments. Integrating centers play an important role in maintaining homeostasis because they are able to integrate information coming in from a sensory neuron. Once this information is interpreted, the integrating center is responsible for initiating a response by sending signals out through efferent neurons.

Which of the following would be one of the body's controlled variables?

Body temperature Respiratory rate Heart rate All answers are correct --Answer Blood pH Blood pressure

infor relating to cannon postulate of homeostatic control

Cellular specificity plays a role in the maintenance and achievement of homeostasis is not one of Cannon's postulates describing the properties of homeostatic control systems. Although cellular specificity is important in the body's functions, it is not considered a property of homeostatic control. One of Cannon's postulates of homeostatic control is that the nervous system plays an important role in maintaining homeostasis. The nervous system is responsible for the detection, integration, and generation of a response when a physiological variable changes. Cannon's postulates of homeostatic control also state that some parameters are under tonic control, which allows the parameter to be increased or decreased. One example of this is the control over the smooth muscles of the blood vessels. These layers of smooth muscle are under the tonic control of the sympathetic nervous system. If sympathetic neurons increase their firing rate, the smooth muscle will contract, and if they decrease firing rate the smooth muscle will relax. Finally, Cannon's postulates of homeostatic control also state that some parameters are under antagonistic control in which, for example, one hormone increases the parameter while a second hormone decreases it. A classic example of this is the control that the autonomic nervous system has on the heart. The sympathetic nervous system increases heart rate and the parasympathetic nervous system decreases heart rate.

Which of the following is not one of Cannon's postulates describing properties of homeostatic control systems?

Cellular specificity plays a role in the maintenance and achievement of homeostasis. --Answer The nervous system plays an important role in maintaining homeostasis. Some parameters are under tonic control, which allows the parameter to be increased or decreased. Some parameters are under antagonistic control in which, for example, one hormone increases the parameter while a second hormone decreases it.

During exercise info + blood flow

During exercise, blood flow to the brain cannot be restricted, as this could harm the brain. The brain requires a substantial amount of oxygen to function properly. Although blood flow to certain organ groups does decrease during exercise in order to divert blood flow to the metabolizing organs, blood flow to the brain does not decrease. During exercise it is important to divert blood flow to the muscle groups that are working to complete the task that has been demanded by the body. One of the places where blood flow is dramatically reduced in order to provide the extra blood flow necessary to the working tissue is the digestive system. This is accomplished by vasoconstriction of the arteries that go to the digestive organs. Blood flow during exercise can be reduced to certain skeletal muscle groups without causing harm to those skeletal muscles. For example, if you are cycling, the skeletal muscles in the legs will need an increase in blood flow, but the skeletal muscles in the arms will not need an increase in blood flow. For this reason, blood flow to the arms will be reduced in order to divert blood to the legs. Blood flow to the skin is usually not reduced during exercise because it helps to provide an important avenue for the release of excess body heat. The dilation of blood vessels of the skin helps you to dissipate some of the heat that builds up because of the increased metabolism. However, if blood flow to the skin is reduced in order to divert some blood to the working tissue, it will not cause harm to the skin

Feed forward control info

Feed forward control allows the body to predict that a change is about to occur and start the response loop in anticipation of the change. All feed forward control pathways occur in anticipation of a change in the physiological variable that has not occurred yet. For example, when carbohydrates are being digested in the small intestine, various gastric hormones are released that will stimulate the pancreas to release insulin into the blood before blood glucose levels increase as a result of the digested meal. The release of insulin by the pancreas is an example of a feed forward control in anticipation of blood glucose levels that will increase once the digested meal is fully absorbed. Positive feedback loops are responsible for moving the physiological variable further from the set point in response to a stimulus. In this description, you are not responding to a stimulus and generating a change in the physiological variable. Reflex control pathways include all the components of the nervous system (afferent neurons, integrating center, and efferent neurons) as well as the sensors and effectors. Negative feedback loops are not anticipatory response loops. Instead, they are response loops that are responsible for making sure that the regulated variable does not range outside of its set point. The negative feedback response loop does not occur until after the physiological variable has changed, while an anticipatory response loop is a feed forward response. Homeostatic imbalance results when control mechanisms are unable to compensate for deviations of a controlled variable from its set-point range. Homeostatic imbalance is commonly referred to as disease.

positive feedback info

In positive feedback, the response of the system goes in the same direction as the change that sets it in motion. Positive feedback is a type of control pathway that is rarer than negative feedback. What this means is that the change in a variable is exaggerated or amplified by positive feedback. For example, if the stimulus is pressure on the cervix because of the head of the baby, the positive feedback pathway employed will produce effects that will provide further pressure on the cervix. Ultimately, the purpose of positive feedback in this example is to facilitate the steps that lead to delivery of the baby. Negative feedback occurs when a variable changes and the responses enacted by the control pathway reverse the change. In other words, if a variable increases, the homeostatic control pathway will elicit responses that will decrease the variable. Feed forward responses are those that occur before the variable changes. These are changes that happen in anticipation of the fact that the variable will change. An example of this would be salivating before eating any food. The stimulus would be the thought , sight, or smell of food, with the salivary glands secreting saliva before food enters the mouth. The secretion of the saliva is preparing the mouth for the food that it is about to receive and will have to digest.

when blood pressure decreases info

In the scenario provided there are three integrators: the hypothalamus, anterior pituitary, and the adrenal gland. There can be multiple integrators and the integrators in a pathway do not have to be the central nervous system or include a portion of the central nervous system. In each of these different integrators you release a different hormone that functions as a signaling molecule onto another integrator. The final efferent pathway is not initiated until an effector that can change the variable is stimulated. This occurs when the adrenal gland releases aldosterone, which acts on the kidney to eventually correct the decreased blood pressure. The scenario provided has more than one integrator. Keep in mind that integrators can include endocrine organs and that the homeostatic control pathway does not terminate until an effector is stimulated by an efferent pathway. The scenario provided has more than two integrators. Take into consideration the steps that have to lead up to the response of the effector. In complicated endocrine homeostatic control pathways such as this one, there can be multiple integrators before the response is initiated. There are fewer than four integrators in this scenario. Recall that an integrator is something that will interpret a sensory signal and then release a chemical that acts as the efferent pathway or activates an efferent neuron. Only when the released chemical goes to a target tissue that produces a response do you see the end of the pathway. If a chemical is released that goes to another organ, which releases a chemical to communicate with yet another organ but does not produce a response that changes the variable, both organs function as integrators.

increased blood glucose info

Increased blood glucose concentrations that occur with diabetes can be detected or monitored by measuring all of the given choices: blood glucose levels, levels of hemoglobin A1c, and urine glucose levels. When a person has diabetes, blood glucose levels will increase. This increase in blood glucose levels can be measured by drawing blood and measuring the amount of glucose in the blood directly. There are standard ranges that doctors follow to determine if blood glucose levels are too high. This is not, however, the only method for detecting elevated levels of blood glucose. Elevated levels of blood glucose concentrations associated with diabetes can be measured by measuring the levels of hemoglobin A1c. Hemoglobin A1c is a form of hemoglobin that becomes glycosylated. This measurement is different than measuring blood glucose concentrations because it gives insight to blood glucose levels over long periods of time as opposed to immediately when the blood sample is taken. This is not, however, the only method for detecting elevated levels of blood glucose. Testing urine concentrations of glucose is a helpful way of detecting if blood glucose levels are higher than normal. The kidneys have a capacity at which they can reabsorb glucose from the filtrate back into the blood. When the threshold for reabsorption (called the transport maximum) is surpassed due to increase levels of blood glucose, the excess glucose will not be reabsorbed and instead will pass into the urine and be excreted. This is not, however, the only method for detecting elevated levels of blood glucose.

When blood pressure decreases, the hypothalamus will release corticotropic releasing hormone (CRH) to the anterior pituitary. The anterior pituitary then releases adrenocorticotropic hormone (ACTH), which will enter the blood and travel to the adrenal gland. The adrenal gland will release aldosterone, which will travel to the kidneys in order to enhance the retention of Na+ and water in order to reestablish a normal blood pressure. When considering homeostatic control pathways, how many integrators are in the scenario provided?

One Three ---Answer Two Four

Secretion of pepsinogen info

Secretion of pepsinogen into the stomach in response to an increase in stomach acidity is an example of positive feedback. When acidity in the stomach increase, the amount of pepsinogen release will increase. If stomach acidity continues to increase, the amount of pepsinogen will also continue to increase. This feedback is causing the physiological variable to move father and father away from the set point, which is positive feedback. Negative feedback moves the physiological variable back toward the set point. If this were an example of negative feedback, the acidity of the stomach might still lead to pepsinogen release, but the role of the pepsinogen would be to reduce the acidity of the stomach, which would eventually result in a decreased release of pepsinogen. Instead, increase of stomach acidity increases the release of pepsinogen and if stomach acidity were to increase, then pepsinogen release would continue to increase. The release of pepsinogen in response to increased stomach acidity is an example of a homeostatic response. This response will help initiate the digestion of proteins in the stomach, which is an essential part of digestive function. Without this response, the digestion of proteins and ultimately the absorption of amino acids would be impaired. The body does not have any homeostatic control pathways that are classified as fast forward feedback. The type of feedback that the body has is negative feedback, positive feedback, and feed forward.

The chemoreceptors info

The chemoreceptors in blood vessels that sense oxygen and carbon dioxide levels in the blood are sensors. In order for homeostatic control mechanisms to be employed successfully, the body has many different reflex pathways. Neural reflex pathways provide communication between the afferent nervous system, an integrating center, and the efferent nervous system. The sensor is the portion of a reflex arc that is sensitive to changes in a physiological variable. The role that the sensor plays is to relay information about the physiological variable to the integrating center via an afferent neuron. In a reflex arc, the effector does not sense changes in the physiological variable. Instead, the role of the effector is to generate a response to bring the system back into homeostasis. Error signals are integral parts of reflex pathways. When an afferent signal is delivered from a sensor, it travels to an integrating center, where the stimulus that caused the reflex pathway to begin is interpreted by the integrating center. The integrating center, however, is not responsible for sensing the physiological variable directly.

correct sequence of events from the stimulus to the target tissue info

The correct sequence of events from the stimulus to the target tissue is: stimulus, input (afferent) signal, integrating center, output (efferent) signal, target response. Homeostatic control pathways depend on receptors that are sensitive to changes in a controlled physiological variable. Receptors communicate with afferent neurons. Afferent signals are those that deliver sensory information to the integrator, which then can result in the stimulus of a neuron, which will send an efferent signal. The efferent signal will then be sent to a target tissue, which will elicit a response that changes the regulated variable. With regard to homeostatic control pathways, the afferent signal will come before the efferent signal. Recall that afferent is defined as the sensory signal and efferent is defined as the motor signal. Before an afferent signal can be transduced onto an efferent signal, there needs to be integration. An integrator will take the information coming in from afferent pathways to determine if an efferent signal is needed in order to elicit a response. Although the steps leading up to the activation of the efferent signal are all in the correct order, the response needs to come after the target. The target is the organ that will create the response once it has received the efferent signal.

stimulus information

The definition of a stimulus is a detectable disturbance or change in the internal or external environment. When a physiological variable ranges outside of its set point, an error signal is generated so that homeostatic pathways can be initiated to correct the physiological variable and bring it back toward its set point. The error message functions as the stimulus. Monitoring a specific variable in its environment is a role of the sensor. Comparing the input signal with the set point and eventually making a decision on whether or not a response is needed is the role of the integrator. Efferent neurons or hormones that function as efferent signaling pathways are responsible for providing the electrical and/or chemical signal that travels to the target.

homeostatic systems info

The most complicated control pathway in homeostatic systems includes an efferent pathway that includes a neuron, an endocrine gland functioning as an integrator, and a target tissue. In this example there is more than one integrator that is stimulated in a chain of signals before a final response is generated by the target tissue. An efferent pathway that includes a two-neuron relay before the target cell is stimulated is one of the simplest homeostatic control pathways. In this example there is only one integrator, while there are other pathways that have more than one. An efferent pathway that consists of one neuron is a very simple efferent pathway. An integrator having an effect on multiple target tissues is a simple system because of the presence of only one integrator. This is part of a simple endocrine reflex. An efferent pathway that includes an endocrine organ as an integrator is another example of one of the more simple homeostatic control pathways. In endocrine reflexes, the endocrine organ frequently serves as sensor, integrating center, and producer of the output signal (a hormone). The efferent pathway described is part of a simple endocrine reflex.

reproductive system

The only organ system that does not have a primary role in maintaining homeostasis is the reproductive system. The reproductive system is primarily responsible for the production of gametes. The cardiovascular system is an important system in the maintenance of homeostasis because of the basic function of the system. The major homeostatic contribution of the cardiovascular system is its transport function. Examples include delivery of oxygen and nutrients to the tissues, delivery of waste products to sites of removal, distribution of heat, transport of ions, and delivery of hormones to target tissues. One example is the role that the cardiovascular system plays in the homeostasis of skeletal muscle. When skeletal muscle increases metabolic rate due to exercise, blood flow to those muscles must increase in order to ensure that the muscle has the oxygen and nutrients that it needs in order to maintain the metabolic rate demanded of muscle. The digestive system is an important system in the regulation of homeostasis. The digestive system breaks down ingested food products, absorbs them into the body, and eliminates some wastes.The digestive system releases many hormones that will help regulate not only digestive function but the feed forward mechanisms important in the release of insulin prior to glucose levels increasing in the blood. Additionally, the digestive system is a target for important hormones that help regulate blood calcium levels. The renal system is very important in regulating the fluid and electrolyte balance of the body. The kidneys can excrete excess K+ to help maintain the resting membrane potentials of your excitable tissues. Additionally, the kidneys can increase the rate of Na+ and water reabsorption to increase blood volumes and subsequently increase blood pressure when it falls below its set point. A major function of the renal system is eliminating nitrogenous wastes and toxins from the body.

Homeostatically controlled variable info

The proper description of the set point is the normal, "desired" value of the variable. All of the body's variables have a set point that they fluctuate around. The homeostatic control pathways are set into motion when a variable starts to fluctuate too far outside of its set point. If a variable ranges too far outside of its set point, then it will lead to the activation of the homeostatic pathway that controls that variable. This is known as the signaling value. In a homeostatic control pathway there are various different components that work together to convey information about a variable. Changes in a physiological variable controlled by a homeostatic pathway are detected by the receptor or sensor. In addition to having receptors, homeostatic control pathways must be able to convey the information from a receptor to an integrator so that the body can initiate an efferent pathway if necessary. The portion of a homeostatic control pathway that sends signals about the variable to the integrating center is the afferent neuron or the afferent pathway.

blood calcium level senario

The scenario provided is an example of negative feedback. Recall that negative feedback will reverse the change that occurs in a physiological variable. In this example the physiological variable is blood calcium levels. In the scenario, blood calcium levels have decreased, which leads to response loops that result in an increase in blood calcium. Positive feedback loops would not produce the response loop observed in the scenario provided. Positive feedback loops move a physiological variable further away from its set point. In the scenario, when blood calcium levels decrease, the response loop results in an increase in blood calcium. If it were a positive feedback loop, blood calcium levels would decrease further and further. Feed forward responses are anticipatory responses. In order for this scenario to be a feed forward response, the levels of parathyroid hormone would change before the blood calcium levels change. Instead, the parathyroid hormone levels are changing in response to the changes in blood calcium levels. Although the scenario does represent negative feedback, it does not represent feed forward loops. Feed forward responses are anticipatory responses. In order for this scenario to be a feed forward response, the levels of parathyroid hormone would change before the blood calcium levels change. The scenario provided does not represent either positive feedback or feed forward. Positive feedback loops would not produce the response loop observed in the scenario provided. Positive feedback loops move a physiological variable further away from its set point and feed forward responses are anticipatory responses. In order for this scenario to be a feed forward response, the levels of parathyroid hormone would change before the blood calcium levels change.

Threshold info

The term used to describe the minimum stimulus to trigger a response in a feedback loop is threshold. The threshold is the point at which a stimulus is significant enough to elicit response through feedback loops. This ensures that the body is able to respond to signals that are significant and ignore those that are not as intense or significant because they do not reach threshold. Homeostatic control pathways do not have affectors. Instead, there are portions of a homeostatic control pathway that are termed afferent because of the type of information and the direction that the signal travels. Afferent signals are sensory signals that travel from the periphery to an integrator and provide an avenue by which a sensory signal can be delivered All homeostatic control pathways will have an effector. The role of the effector is to change its function in response to the signals delivered from the integrator in order to cause a change in the physiological variable. Oscillate is not a term used to describe the minimum amount of stimulus needed in order to elicit a response from a feedback loop.

Which of the following is the proper description of a set point for a homeostatically controlled variable?

The value that a variable reaches that results in the activation of a homeostatic control pathway The factor that senses changes in the variable The normal, "desired" value of the variable------Answer The structures that will send signals about the variable to an integrating center

physiological control systems info

With regard to physiological control systems, negative feedback systems are more common than positive feedback systems. Negative feedback loops are homeostatic; positive feedback loops are not. Negative feedback is necessary in order for our bodies to maintain a healthy range of values for several physiological variables (i.e., body temperature, blood glucose levels, and heart rate). Whenever these variables increase or decrease, negative feedback loops are employed in order to bring this values back to their normal ranges. Positive feedback also has importance to it, but is specific to only a few physiological pathways and is not homeostatic. The body's physiological variables are rarely kept at a constant value. Even some of the most important regulated variables fluctuate around a set point. Some of these physiological variables fluctuate more than others, but there will always be a range. Positive feedback does amplify or exaggerate the change that occurs in a variable. These amplifying effects, however, are necessary for proper function and do not lead to excessive damage of the host. The variables of the body are under the control of both negative and positive feedback loops. Although the negative feedback loops are employed much more frequently than the positive feedback loops, both are used by the system.

A positive feedback mechanism is prevented from spiraling out of control by __________.

a factor that removes the stimulus all answers are correct --answer a factor that limits the system's ability to respond to the stimulus a factor that stops the feedback loop

The term used to describe the minimum stimulus to trigger a response in a feedback loop is __________.

affector oscillate threshold ---Answer effector

Blood calcium levels are very closely regulated due to calcium's importance in neurotransmission, blood clotting, and muscle contraction. When blood calcium levels decrease, the parathyroid glands will sense a decline in calcium concentrations and release parathyroid hormone. Parathyroid hormone is responsible for targeting bone, the small intestine, and the kidneys in order to increase blood calcium levels. This is an example of ___________.

feed forward feed forward and negative feedback feed forward and positive feedback positive feedback negative feedback ---Answer

The drop in blood pressure that can occur when a person stands up too quickly is a(n) __________.

regulated variable error signal ---Answer set point all answers are incorrect

The chemoreceptors in blood vessels that sense oxygen and carbon dioxide levels in the blood are __________.

sensors ---Answer part of the integration center effectors error signals