Homeostasis : Control, Feedback System, Homeostatic Imbalance and MCQs for NEET, GPAT, CSIR NET JRF

INTRODUCTION :-

” The mechanism by which the constancy of the internal environment is maintained and ensured is called the homeostasis.”

1.] Homeostasis is an dynamic condition.

2.] Each structure, from the cellular level to the systemic level, contributes in some way to keeping the internal environment of the body within the normal limits.

CONTROL OF HOMEOSTASIS :-

1.] Homeostasis in the human body is continually being distributed sometimes from the external environment in the form of physical insults such as intense heat.

2.] Other disruptions originates in the internal environment, such as blood glucose level that falls too low when you skip breakfast.

3.] In most cases the disruption of homeostasis is mild and temporary, and the responses of body cells quickly restores balance in the internal environment.

FEEDBACK SYSTEM :-

” A feedback system or feedback loop is a cycle of events in which the status of a body condition is monitored, evaluated, changed, remonitored, reevaluated and so on.”

• Controlled condition : Each monitored variable, such as body temperature, blood pressure, or blood glucose level.
• Stimulus : Any disruption that changes a controlled condition.

1.] The body can regulate its internal environment through many feedback systems.

2.] A feedback system includes three basic components :-

• Receptors : A receptor is a body structure that monitors changes in a controlled conditions and sends input to a control center.
• Control Center : A control center in the body, for example the brain, sets the range of values within which a controlled condition should be maintained, evaluates the input it receives from receptors and generate output command when they are needed. Output from the control center typically occurs as nerve impulse, or hormones or other chemical signals.
• Effector : An effector is the body structure that receives output from the control center and produces a response or effect that changes the controlled conditions.

3.] In a feedback system the response of the system “feed back” information to change the controlled condition in some way, either negating it (negative feedback) or enhancing it (positive feedback).

A.] NEGATIVE FEEDBACK SYSTEM : A negative feedback system reverses a changes in a controlled condition.

B.] POSITIVE FEEDBACK SYSTEM : A positive feedback system tends to strengthen or reinforce a change in one of the body’s controlled condition.

HOMEOSTATIC IMBALANCE :-

• When one or more components of the body lose their ability to contribute to homeostasis, however, the normal equilibrium among body processes may be disturbed.
• If the homeostasis imbalance is moderate, a disorder or disease nay occur, if it is severe, death may be the result.

MULTIPLE CHOICE QUESTIONS [MCQs] :-

1.] Which of the following statement best describe the homeostasis ?

a. Keeping the body in a fixed or unaltered state

b. Dynamic equilibrium

c. Maintaining a near – constant internal environment

d. Altering the external environment to accommodate the body needs

2.] Which of the following feature of a system is unlikely to lead to a stable homeostatic system ?

a. Negative feedback

b. Positive feedback

c. Redundancy

d. Complexity

3.] Which of the following strategies would not help restore a high body temperature to normal?

a. Non – shivering thermogenesis

b. Sweating

c. Flattening of skin hair

d. Redistribution of blood flow to the periphery

4.] Which of the following hormone is not important in calcium homeostasis ?

a. Calcitonin

b. Parathyroid hormone

c. 1 , 25 – dihydroxycholecalciferol

d. Glucagon

5.] Which of the following word means a change in environment ?

a. Neuron

b. Reflex

c. Stimulus

d. None of the above

6.] Give two examples of effector. Select the two correct answers ?

a. Glands

b. Muscles

c. Neurons

d. Synapse

7.] Which of the following is not a homeostatic mechanism ?

a. Hormonal regulation

b. Thermoregulation

c. Oxygen regulation

d. Water regulation

8.] Homeostasis is classified under which of the following ?

a. Transcription

b. Cell regulation

c. Cell respiration

d. Photosynthesis

9.] Helps maintain cellular homeostasis by modifying, sorting and packaging protein to transport ?

a. Nucleus

b. Golgi apparatus

c. Endoplasmic reticulum

d. Cell membrane

10.] The secretion of hormone is an example of homeostatic feedback loop. The basic function of a feedback loop is to ?

a. Regulate a process

b. Create substance

c. End the process

d. Destroy substance

SOLUTIONS :-

1.] (c) Maintaining a near – constant internal environment

2.] (b) Positive feedback

3.] (a) Non – shivering thermogenesis

4.] (d) Glucagon

5.] (c) Stimulus

6.] (a) and (b) Glands and Muscles

7.] (a) Hormonal regulation

8.] (b) Cell regulation

9.] (b) Golgi apparatus

10.] (a) Regulate a process

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REFERENCES :-

1.] Textbook Of Pathology By Harsh Mohan; 7th edition; Page no. 78

2.] Gerard J Tortora- Principles of Anatomy and Physiology; 12th edition; page no. 8 – 11