Homeostasis - Week 1

Question 1

What is Homeostasis?

Answer 1

Homeostasis is the ability of the body (organs and systems) to maintain a stable internal environment in response to a changing external environment.

It continually regulates different variables such as body temperature, blood sugar level, blood pressure, and pH.

When something disturbs this balance, our body works to restore it and return to normality

Example, fluctuations to the temperature of the external environment, the body maintains a relatively constant internal temperature of approximately 98.6°F (37°C).

Question 2

What are the Homeostatic Controls?

Answer 2

The body functions within a narrow range of tolerance limits and maintains its internal environment by monitoring and regulating:

1. Temperature
2. Salinity
3. Ion Concentration
4. Oxygen Levels
5. pH

Question 3

What is the Set Point and Set point Range of Homeostasis?

Answer 3

The set point is the normal value of a controlled condition i.e. Body Temperature is 37 degrees

The set point range (upper and lower values) of the normal limits.

Question 4

How is Homeostasis achieved?

Answer 4

Homeostasis is achieved by feedback systems in place throughout the body.

These systems monitor and respond to changes in the condition of the body i.e. glucose levels, temperature, blood pressure.

Feedback systems involve both nervous and hormonal regulation

Question 5

What are the two feedback loops in Homeostasis?

Answer 5

A negative feedback system - reverses or negates any potentially harmful change in a controlled condition, bringing it back to within the normal limits of its set point range.

A positive feedback system - reinforces or promotes any change from a previous state, advancing the controlled condition to its optimal required state.

Question 6

What are feedback loops?

Answer 6

Feedback loops are biological mechanisms that work to support/maintain homeostasis under different conditions.
They are classified by two major forms:
(1) Positive feedback
(2) Negative feedback

Question 7

What is a negative feedback loop?

Answer 7

Negative feedback provides stability. The effector activated by the control centre opposes or negates the original stimulus. It generally minimises change, keeping variation in key body systems within limits.

• If the response counteracts the stimulus, the response is halted.
• If the response is not strong enough to counteract the stimulus, the feedback loop begins again.
• Negative feedback repeats until the controlled condition is brought back to within the normal limits of its set point range.

Question 8

What is a positive feedback system?

Answer 8

Positive feedback produces a response that exaggerates or enhances the change in the original conditions, rather than opposing it.

The positive feedback repeats, often increasing deviation from the set point or ideal normal value, until the original stimulus is removed.

Question 9

How does the feedback system function?

Answer 9

1. Stimulus – Produces change in the environment
2. Receptor – Sensors change and sends information along Afferent
   pathway to Control Centre
3. Control Centre – Brain receives information, decides what action
   to take and sends this information along the Efferent pathway
4. Effector – The structure within the body (cell, tissue, organ or
   system) that will carry out the response.
5. Response – Either Negative feedback (response to counteract or
   negate stimulus) or Positive feedback (promote the stimulus)
6. Feedback- The feedback loop.

   - If Negative feedback loop then response is halted or feedback 
     loop repeats until back to normal limits.
   
   - If Positive feedback loop then response is to repeat to increase 
     deviation from normal value until original stimulus is removed.

Question 10

What is the Stimulus in the Feedback loop?

Answer 10

A disruption or change in a controlled environment i.e. Change in temperature, salinity, ion concentration, oxygen levels, or pH.

Question 11

What is the Receptor in the Feedback loop?

Answer 11

A sensor that monitors the environment and responds to a stimulus by sending information, in the form of either a chemical or electrical signal, to a control centre body
i.e. Senses mechanical force, Chemical Composition, Change in Tempreture or Change in Light.

Question 12

What is the Afferent Pathway in the Feedback loop?

Answer 12

Input of Information from the Receptor sent along the Afferent pathway to the Control Centre

Question 13

What is the Control Centre in the Feedback loop?

Answer 13

Region of the brain that receives information about the stimulus from the receptor, determines the appropriate response and relays information about the response to the effector.

It is the control centre that determines the set point around which the controlled condition is maintained i.e. Hypothalamus and pituitary gland.

Question 14

What is the Efferent Pathway in the Feedback loop?

Answer 14

Output of Information from the Control Centre sent along the Efferent Pathway to the Effector

Question 15

What is the Effector in the Feedback loop?

Answer 15

An Effector is a structure within the body such as a cell, tissue, organ, or system that provides the means for carrying out the response.
i.e. Muscles, glands, and organs.

Question 16

What is the Response in the Feedback loop?

Answer 16

Will be either Negative feedback or Positive feedback

• Negative feedback: A response is elicited to counteract or negate the stimulus.
• Positive feedback: A response is elicited to promote the stimulus.

I.e. Dilation/constriction of blood vessels, sweating, shivering, milk ejection, change in breathing rate, in/decreased muscle contraction, in/decreased hormone secretion, and in/decrease in heart rate.

Question 17

What is the Feedback in the Feedback loop?

Answer 17

Negative Feedback
- If the response counteracts the stimulus, the response is halted.
- If the response is not strong enough to counteract the stimulus, the feedback loop begins again.
- Negative feedback repeats until the controlled condition is brought back to within the normal limits of its set point range.

Positive Feedback
The positive feedback repeats, often increasing deviation from the set point or ideal normal value, until the original stimulus is removed.

Question 18

Describe the process of Thermoregulation (Temperature Increase) as a Negative Feedback Loop

Answer 18

A change in body temperature may be triggered by a Change in External environment or Metabolic activity of cells within the body.

1. Stimulus – An Increase in body temperature above the normal set point of 37 degrees
2. Receptor – Peripheral thermoreceptors (sense change in temp) in the skin detect the increase in body temperature
3. Control Centre – Information in the form of electrical signals (nerve impulses) is sent from peripheral thermoreceptors to a region in the brain called the hypothalamus
4. Effector – Information is relayed from the hypothalamus to blood vessels around the body and sweat glands in the skin.
5. Response – Blood vessels respond with vasodilation to increase heat loss, while the sweat glands respond by secreting sweat to increase heat loss. Vasodilation and sweating lead to a drop in body temperature
6. Feedback - The cooling then negates the original stimulus and reduces the response, in a negative feedback loop

Question 19

Describe the process of Lactation (Breastfeeding) as a Positive Feedback Loop

Answer 19

Lactation is regulated by a homeostatic mechanism through which milk ejection is stimulated by a suckling child.

Milk ejection intensifies and increases through positive feedback until the child stops suckling.

1. Stimulus – Mechanical stimulation of the nipple by a suckling child.
2. Receptor – Peripheral mechanoreceptors (Sense mechanical force) in the nipple detect a child suckling.
3. Control Centre – Information in the form of electrical signals (nervous impulses) is sent from peripheral mechanoreceptors to a region in the brain called the hypothalamus, which in turn relays information in the form of chemical signals (hormones) to an endocrine organ in the brain called the posterior pituitary.
4. Effector – The hormone oxytocin is released from the posterior pituitary gland and acts as a chemical signal, stimulating the effector cells surrounding the milk-producing glands of the breast.
5. Response – Cells surrounding the milk-producing glands of the breast contract, triggering milk ejection.
6. Feedback - The milk production then reinforces the original stimulus and promotes the original milk ejection response, in a positive feedback loop, until the stimulus is removed (the child stops suckling).

Question 20

What happens when there is uncontrollable disruptions to Homeostasis?

Answer 20

When systems within the body are unable to sustain a normal set point or set range, the abnormal functioning results in symptoms to a condition or disease.

When numerous disruptions to homeostasis occur simultaneously, negative feedback systems are overwhelmed and positive feedback systems operate at potentially harmful levels, leaving the body weak, vulnerable and susceptible to death.