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BIOL 2010 > Homeostasis and Feedback Control > Flashcards

Homeostasis and Feedback Control Flashcards

1
Q

Define homeostasis

A

ability to upkeep relatively constant internal conditions and environment, despite external environment fluctuating

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2
Q

does homeostasis have any impact on humans? how so?

A

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

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2
Q

the concentration of what materials in the body can be regulated

A

nutrient molecules, wastes, water, salt, CO2, O2, and other electrolytes

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2
Q

which internal condition factors are regulated through homeostasis

A

pH, temperature, volume, pressure, and concentration

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3
Q

define regulated variable

A

a variable that stays within a narrow range (i.e. maintained)

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4
Q

define set point

A

the anticipated or “normal” value of the regulated variable within a range

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5
Q

define normal range

A

a restricted set of values that is optimally healthy and stable

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6
Q

Explain the difference between the set point and normal range through a real life example, such as driving a car on the highway

A
  • set point: middle of lane
  • normal range: within one lane
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7
Q

how does homeostatic regulation occur?

A

through feedback systems (positive, negative)

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8
Q

list the 3 basic components of feedback systems

A

sensor/receptor, integrating center, and effector

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9
Q

explain the sensor/receptor stage of homeostatic feedback systems

A

the monitors change in controlled variable and sends information to the integrating center

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10
Q

explain the integrating center stage of homeostatic feedback systems

A

detects changes from set point and generates output

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11
Q

explain the effector stage of homeostatic feedback systems

A

receives output from integrating center

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12
Q

explain what negative feedback is

A

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
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13
Q

give a real life example of negative feedback loop

A

maintaining body temperature through shivering and sweating

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14
Q

what are antagonistic effectors

A

more than one effector working in opposite directions to maintain homeostasis (blood glucose levels)

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15
Q

explain what positive feedback is in homeostasis

A

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
16
Q

give a real life example of a positive feedback loop

A

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
17
Q

are positive feedback loops safe? how so?

A
  • 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
18
Q

define runaway positive feedback

A

positive feedback results in body moving very far from homeostasis, where death or medical procedures stops the loop

19
Q

how do symptoms of heatstroke relate to failure of feedback mechanism

A
  • 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
20
Q

what are the two general categories of regulatory mechanisms to maintain homeostasis

A

intrinsic and extrinsic

21
Q

homeostatic regulation occurs through ________ and _________ body systems. explain.

A

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
22
Q

give an example of neural and endocrine regulation. what type of feedback control is this?

A

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
23
Q

why are hormones released

A

response to chemical stimuli

24
Q

an example of negative feedback inhibition (or a closed loop control system) may be?

A

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
25
Q

what is the fundamental difference between negative and positive feedback?

A

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

26
Q

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?

A

negative feedback - the goal is to get back to homeostatic conditions

27
Q

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?

A

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

28
Q

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?

A

positive feedback - the reaction was driving in one direction even further but there is an endpoint to which the result cannot go further

29
Q

Glands are an example of which component of feedback systems

A

effector

30
Q

what fluid compartment contains the most water found in the human body

A

intracellular fluid

30
Q

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

A

The primary mechanism to maintain homeostasis is positive feedback

Generally, it is negative feedback (so that the system balances back to normal)

30
Q

what homeostatic regulatory systems are the endocrine and nervous systems considered

A

extrinsic

31
Q

explain the process of feedback systems briefly

A

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

32
Q

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?

A

positive feedback control

33
Q

T/F: The internal and external environments are separated by the selectively permeable membranes of epithelial cells

A

True

34
Q

T/F: The homeostatic mechanisms of the body are unlimited in their ability to respond to changes in the external environment

A

False

35
Q

T/F: Positive feedback loops are impossible to stop once they have begun

A

False

36
Q

T/F: Blood glucose is a regulated variable

A

True

BIOL 2010 (18 decks)

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