Class 8th Science Chapter 1, Human Organ System

HUMAN ORGAN SYSTEM

Human Organ System human body, physical substance of the human organism, composed of living cells and extracellular materials and organized in tissues, organs and system.

HUMAN ORGAN SYSTEM

Human anatomy and physiology are covered in many different articles. For detailed information on specific tissues, organs, and system, see Human Blood; Cardiovascular systems; human digestive system; endocrine system, human; Renal System; skin; human muscular system; nervous systems; human reproductive system; human respiration; human sensory reception; skeletal systems, human. For a description of how the body develops, from conception to old age, see aging; increase; prenatal development; human development.

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Class 8th Science Chapter 1, Human Organ System 6

HUMAN ORGAN SYSTEMS

For detailed coverage of the body’s biochemical components, see Proteins; carbohydrate; nucleic acid lipid; vitamin; and hormone. For information on the structure and function of the cells that make up the body, see cell.

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Class 8th Science Chapter 1, Human Organ System 7

UNIT:1

HUMAN ORGAN SYSTEM

SHORT ANSWERS

Q1. Define (a) excretion (b) reflex action (c) neuron.

Ans. (a) Excretion

The process of removing waste material from the body is called excretion.

(b) Reflex action

The sudden and automatic response of the body for certain stimuli is called reflex action

(c) Neuron

Neuron is the basic unit of nervous system that carries electrical impulses.

Q2. Skin is considered as excretory organ, why?

Ans. Skin is considered as excretory organ because extra salt comes out of the pores in the skin in the form of sweat.

Q3. Draw and label the structure of a neuron.

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Q4. Differentiate between.

Receptors and effectors

Receptors are the organs that receive information from the environment while effectors are the organs that show response to stimuli.

Voluntary and in voluntary actions

Voluntary actions are under the control of an organism. For example, you pick and throw something. Involuntary actions occur without the control of an organism. For example, you touch a hot stove.

Lithotripsy and dialysis

Lithotripsy is the process that breaks stones in kidney, gall bladder or urethra while dialysis is the process that removes harmful material from the blood of those people whose kidneys do not work properly.

Q5. Explain the central neuron system.

Ans. Central nervous system controls most of the actions of the body. It consists of brain and spinal cord.

DETAILED ANSWERS

Q1. Explain reflex action with the help of an example and diagram.

Ans. Those actions that occur without the conscious control of an organism are called reflex actions. These are the immediate and involuntary response to a stimulus.

Example: If a person accidentally touches a hot stove. Sensory neuron in skin brings this impulse to spinal cord. Inter neuron of the spinal cord processes and transmits it to motor neuron. The motor neuron carries the impulse to the arm muscles. The arm muscles contract and the hand is pulled back.

FB_IMG_1560779971814.jpgQ2. Describe the role of kidneys in excretion of waste.

Ans. Kidneys play an important role in excretion of waste. Blood brings waste material into kidneys. Excess of water and waste material is filtered from the blood. This waste material goes out of the body in the form of urine while the clean blood goes back to the circulatory system.

Q3. Compare the advantages dialysis and kidney transplant and how long does a transplanted kidney last?

word image 7Ans. Advantages of:

Extra fluids and waste products are removed through this process.

Dialysis involves less risk of life than kidney transplant.

Advantages of kidney transplant:

Successful kidney transplantation can improve the quality of life and reduce risk of dying. People who undergo kidney transplantation do not require hours of dialysis treatment. Kidney transplant usually lasts for about 12 to 15 years.

Q4. What are the advantages and disadvantages of kidney transplant?

Ans. Advantages of transplant:

Successful kidney transplantation can improve the quality of life and reduce risk of dying. People who undergo kidney transplantation do not require hours of dialysis treatment.

Disadvantages of transplant:

Kidney transplant may cause infection, bleeding and damage the surrounding organs. Death can occur in rare cases. After transplantation regular medication and monitoring is needed the entire life.

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