Homeostasis and Feedback Control Flashcards
Define homeostasis
ability to upkeep relatively constant internal conditions and environment, despite external environment fluctuating
does homeostasis have any impact on humans? how so?
when homeostasis is disrupted, disease and death may occur. the external environments are changing constantly, and if our body becomes sensitive to every change, then we cannot remain healthy
the concentration of what materials in the body can be regulated
nutrient molecules, wastes, water, salt, CO2, O2, and other electrolytes
which internal condition factors are regulated through homeostasis
pH, temperature, volume, pressure, and concentration
define regulated variable
a variable that stays within a narrow range (i.e. maintained)
define set point
the anticipated or “normal” value of the regulated variable within a range
define normal range
a restricted set of values that is optimally healthy and stable
Explain the difference between the set point and normal range through a real life example, such as driving a car on the highway
- set point: middle of lane
- normal range: within one lane
how does homeostatic regulation occur?
through feedback systems (positive, negative)
list the 3 basic components of feedback systems
sensor/receptor, integrating center, and effector
explain the sensor/receptor stage of homeostatic feedback systems
the monitors change in controlled variable and sends information to the integrating center
explain the integrating center stage of homeostatic feedback systems
detects changes from set point and generates output
explain the effector stage of homeostatic feedback systems
receives output from integrating center
explain what negative feedback is
a way to reverse a deviation from a set point
- if regulated variable increases, the system can decrease it (vice versa)
- minimizes changes to physiological variables
give a real life example of negative feedback loop
maintaining body temperature through shivering and sweating
what are antagonistic effectors
more than one effector working in opposite directions to maintain homeostasis (blood glucose levels)
explain what positive feedback is in homeostasis
further drives a change in physiological condition, resulting in a change in status of body rather than return to homeostasis
- this type of feedback is only normal when there is a clear endpoint
give a real life example of a positive feedback loop
childbirth
- head of baby pushes against cervix
- nerve impulses from the cervix go to the brain
- brain stimulate pituitary gland to release oxytocin
- oxytocin travels through bloodstream into uterus
- oxytocin stimulates contractions and pushes the baby towards the cervix
are positive feedback loops safe? how so?
- only when there is a definite end point
- often this process works to remove the original stimulus or limit the systems ability to respond to the stimulus
define runaway positive feedback
positive feedback results in body moving very far from homeostasis, where death or medical procedures stops the loop
how do symptoms of heatstroke relate to failure of feedback mechanism
- profuse sweating, strong pulse, dry or damp skin
- instead of a normal amount of this happening to cool the body down, this further worsens through the heat and makes the individual more hot
what are the two general categories of regulatory mechanisms to maintain homeostasis
intrinsic and extrinsic
homeostatic regulation occurs through ________ and _________ body systems. explain.
neural; endocrine
- endocrine system regulated by hormones and specific organs responding to that hormone are called target organs
- nerve fibres innervate the target organs they regulate
give an example of neural and endocrine regulation. what type of feedback control is this?
blood pressure falling whilst going from lying down to standing up (stimulus) –> negative
- blood pressure receptors respond (sensor), sending information to the brain (integrating center)
- heart rate increases (effector) through the motor nerve fibers
- blood pressure rises (response) and the person may lie down again
why are hormones released
response to chemical stimuli
an example of negative feedback inhibition (or a closed loop control system) may be?
blood glucose
- eating increases blood glucose which increases insulin and cellular uptake of glucose to bring it down
- fasting decreases blood glucose, which decreases insulin and increases glucagon. this decreases cellular uptake of glucose but increases its secretion into the blood through the liver. this all in turn, brings the blood glucose levels back up
what is the fundamental difference between negative and positive feedback?
negative feedback generally works to bring the body back to a balanced (homeostatic) state, whereas positive feedback further drives the result in one direction, regardless of whether homeostasis occurs or not
Blood glucose levels decrease, alpha cells in pancreas secrete glucagon causing breakdown of glycogen and release
of glucose into bloodstream and blood glucose levels increase to set point. Is this an example of positive, negative, or runaway positive feedback. Why?
negative feedback - the goal is to get back to homeostatic conditions
A person experiences severe trauma and loses a large amount of blood resulting in a drop in blood pressure. Loss of blood means less oxygen and nutrients getting to the heart muscle, so the heart beats faster and stronger to try to deliver more oxygen/nutrients but pressure drops further with more blood loss. Not enough oxygen delivered to heart causes heart damage which lowers blood pressure. This causes heart to beat faster and stronger to try to compensate causing more heart damage which further lowers blood pressure until person expires. What type of feedback mechanism is this?
runaway positive feedback - this situation was further driving a factor in the same direction but there was no control or limit. this led to death
While slicing onions in the kitchen you accidently cut your finger and begin bleeding. Blood pressure and blood flow decreases at the site of the cut and platelets accumulate at the cut site. Platelets release clotting factors which recruit more platelets which release more clotting factors until a clot forms over the wound. What type of feedback mechanism is this?
positive feedback - the reaction was driving in one direction even further but there is an endpoint to which the result cannot go further
Glands are an example of which component of feedback systems
effector
what fluid compartment contains the most water found in the human body
intracellular fluid
Which of the following statements about homeostasis is FALSE?
A) The extracellular fluid is maintained in a state compatible for life.
B) The primary mechanism to maintain homeostasis is positive feedback.
C) The organ systems work together to maintain homeostasis.
D) Illness can result if homeostasis is disrupted.
E) Homeostasis is the maintenance of the internal environment
The primary mechanism to maintain homeostasis is positive feedback
Generally, it is negative feedback (so that the system balances back to normal)
what homeostatic regulatory systems are the endocrine and nervous systems considered
extrinsic
explain the process of feedback systems briefly
sensors detect a change in a regulated variable; and send that information to integrating centres; this relays to effectors, which are usually muscles or glands
When people cut themselves, they have clotting factors in their blood that will be released continuously in a cascade until their blood clots and terminates the bleeding. What mechanism caused their blood to clot?
positive feedback control
T/F: The internal and external environments are separated by the selectively permeable membranes of epithelial cells
True
T/F: The homeostatic mechanisms of the body are unlimited in their ability to respond to changes in the external environment
False
T/F: Positive feedback loops are impossible to stop once they have begun
False
T/F: Blood glucose is a regulated variable
True
