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8th Grade Science Notes | Q/A Unit No.1 HUMAN ORGAN SYSTEM (75 Questions)

Notes-Science-Grade-8
Unit No. 1 HUMAN ORGAN SYSTEM

8th Grade Science Notes | Q/A Unit No.1 HUMAN ORGAN SYSTEM


1. What is the function of the nervous system? Or Define the nervous system.
Ans: A system that carries messages from one part of the body to another part of the body is called the nervous system. It coordinates the functions of the body.
2. Write the names of major parts of the nervous system?
Ans: Two major parts of the nervous system

  • Central Nervous System (CNS) 
  • Peripheral Nervous System (PNS)

3. What is meant by CNS?
Ans: CNS stands for Central Nervous System. It consists of the brain and spinal cord.
4. What is meant by PNS?
Ans: PNS stands for Peripheral Nervous System. It consists of a network of nerves. It connects the CNS to all parts of the body.
5. What is meant by neuron or nerve cell?
Ans: The neuron or nerve cell is the nervous system’s basic structural and functional unit.
6. Draw a diagram of a neuron and label its parts.

8th Grade Science Notes | Q/A Unit No.1 HUMAN ORGAN SYSTEM  (75 Questions)


7. What is the function of dendrites?

Ans: Dendrites receive messages.
8. What is the function of the axon?
Ans: Axon conducts messages away from the cell body.
9. How many types of neurons? Write names.
Ans: Neurons are of three types.

  1. Sensory neurons
  2. Interneurons
  3. Motor neurons

10. What is the function of sensory neurons?
Ans: Sensory neurons carry nervous impulses from sense organs to the central
nervous system (CNS).
11. Where are interneurons present and what is the function of inter-neurons?
Ans: Interneurons are present in the brain and spinal cord (CNS). They form a link
between sensory neurons and motor neurons
12. What is the function of motor neurons?
Motor neurons carry nerve impulses from CNS to effectors (muscles and glands).
13. What is nerve impulse? Or How does a neuron carry messages?
Ans: Neurons carry messages in the form of electrochemical waves that are called nerve impulses.
14. What is the speed of impulses in our body?
Ans: Impulses may travel as fast as 150 m/s or as slow as 0.2 m/s.

15. What is meant by nerve?

Ans: A nerve is a cable-like bundle of axons present side by side in a sheath.
16. What is the function of nerves in your body?
Ans: The nerve conveys the messages carried by the neuron from one body part to another.
17. In how many parts brain is divided? Or name the parts of the brain.
Ans: Human brain is divided into three parts.
i. Forebrain ii. Midbrain iii. Hindbrain
18. Which is the largest part of the brain?
Ans: Forebrain is the largest part of the human brain.
19. Write the names of the main parts of the forebrain.
Ans: Forebrain has three parts.
i. Cerebrum ii. Thalamus iii. Hypothalamus
20. Which types of actions are controlled by the cerebrum? Or write functions of the cerebrum.
Ans: The cerebrum controls many actions like thinking, feelings, emotions, seeing, hearing, speech, memory, and decision making.
21. What is the function of the thalamus?
Ans: It controls many sensory functions.
22. Make a diagram of the brain and label its different parts.
23. What are the functions of the hypothalamus?
Ans: It controls body temperature, hunger, and thirst.
24. Where is the midbrain situated?
Ans: It is present below the cerebrum. It is a small part of the brain.

25. What is the function of the midbrain?

Ans: It receives messages from sense organs and sends them to the appropriate part of the brain.
26. How many parts are the hindbrain?
Ans: Hindbrain consists of three parts.
    i. Cerebellum      ii. Pons      iii. Medulla Oblongata
27. Which part of the brain maintains the balance of our body? Or What is the function of the cerebellum?
Ans: Cerebellum maintains our body balance and accurate movement of our body.
28. What is the function of Pons?
Ans: It controls many functions like the taste, swallowing, equilibrium, and sleep. It is present below the midbrain.
29. Where is medulla oblongata present and what are the functions of the medulla?
Ans: It forms the posterior part of the brain. It is connected to the spinal cord.
It controls heartbeat, breathing, and digestion. It keeps on working when the rest of the brain goes to sleep.
30. What is the weight of an adult man’s brain?
Ans: The weight of the human brain is about 1.5 kg.
31. How many neurons are present in the human brain?
Ans: It consists of about 100,000,000,000 neurons.
32. What is the spinal cord? And where is it present?
Ans: Spinal cord is an extension of the medulla. It is also made up of inter-neurons.
It runs inside the backbone up to its lower end.

33. What is the function of the spinal cord?

Ans: Spinal cord creates a link between the brain and different body parts. It also controls reflex actions and some other involuntary actions.
34. Which nerves are called cranial nerves?
Ans: The nerves which arise from the brain are called cranial nerves.
35. Which nerves are called spinal nerves?
Ans: The nerves which arise from the spinal cord are called spinal nerves.
36. How many pairs of cranial nerves are in the human body?
Ans: There are 12 pairs of cranial nerves in the human body.
37. How many pairs of spinal nerves are in the human body?
Ans: There are 31 pairs of spinal nerves in the human body.
38. What is meant by stimulus?
Ans: Any change in the environment that can be detected by a receptor to initiate a nerve impulse is called a stimulus. Heat, cold, pressure, and sound waves are examples.
39. What is meant by receptors?
Ans: Organs that can detect stimuli are receptors. The ear, nose, tongue, skin, and eyes are receptors.
40. Name at least two effectors.
Ans: Muscles and glands are effectors. They produce responses according to an impulse of motor neurons.
41. What are voluntary actions? Give examples.
Ans: The body actions that are performed under conscious control are called voluntary actions. Speaking, eating, reading, writing, walking, running, etc. are examples of voluntary actions.
42. What are involuntary actions? Give some examples.
An: The involuntary actions which are performed without involvement in the thinking process are called involuntary actions. Heartbeat, breathing, blinking of eyes, and digestion are examples of involuntary actions.

43. What is meant by reflex action? Give some examples.

Ans: An immediate and involuntary response to a stimulus is called reflex action.
44. What is meant by the reflex arc and what is its path?
Ans: The path of nerve impulses that complete a reflex action is called the reflex arc.
It consists of a receptor, a sensory neuron, an interneuron, a motor neuron, and effectors.
45. What is the difference between receptors and effectors?
Ans: Receptors detect stimuli and send messages to inter-neuron.
Effectors produce responses according to an impulse of motor neurons.
46. What is the difference between neurons and nerves?
Ans: The neuron or nerve cell is the nervous system’s basic structural and functional unit.
A nerve is a cable-like bundle of axons present side by side in a sheath.
47. What is the difference between voluntary actions and involuntary actions?
Ans: Voluntary actions: The body actions which are performed under conscious control are called voluntary actions.
Involuntary actions: The involuntary actions which are performed without involvement in the thinking process are called involuntary actions. Heartbeat, breathing, blinking of eyes, and digestion are examples of involuntary actions.
48. What is the difference between kidneys and lungs?

Kidneys:

Kidneys remove nitrogenous materials and salts from the body through urine.
Its functional units are nephrons.

Lungs:  
Lungs remove carbon dioxide gas during respiration
Its functional units are alveoli.
49. What is the difference between lithotripsy and dialysis?

Lithotripsy:

Shock waves break the stones into small pieces which are passed out of the body through urine.

It is a permanent treatment.

Dialysis:

  1. It is an artificial process that is used to clean blood and remove waste material from the body.
  2. It is a temporary treatment.

50. Why is the motorcyclist advised to wear the helmet?
Ans: Human brain is a very sensitive part. It controls all the body’s actions, so, it is very necessary to protect the brain by using a helmet.
51. A person met an accident in a car. When he was brought to the hospital he did not know even his name. What would have happened to him? Relate your answer concerning your nervous system.
Ans: He would get an injury in his forebrain which results in the loss of memory.
52. What is meant by excretion?
Ans: Removal of extra products (nitrogenous waste material) from the body is called excretion.
53. What is the excretory system?
Ans: Nitrogenous material, extra water, and salts are removed by the excretory system.
It consists of a pair of kidneys and associated structures, two ureters, a urinary bladder, and a urethra.
Some extra salts are removed through the skin during perspiration. Lungs are also excretory organs.
54. Where are kidneys present in the human body?
Ans: Kidneys are present in the lower abdominal region on both sides of the vertebral column.
55. What is the function of kidneys?
Ans: The kidney filtrate extra salts and waste material from the blood and remove them from the body.
56. Which structures are associated with kidneys?
Ans: Two ureters, a urinary bladder, and a urethra are associated with kidneys.
57. What is the internal structure of the human kidney? Draw a diagram of the human kidney and label its parts.
Ans: 

The Structure of Kidney

The kidney is divided into three regions.
i. Renal Cortex: It is the outermost region
ii. Renal Medulla: It is the middle region. It is divided into two conical masses called renal pyramids.
iii. Renal Pelvis is an inner area where urine is drained. The urine from the renal pelvis moves into the ureter.
58. What is a nephron? What is the basic unit of the excretory system or kidney?
Ans: Nephrons are the basic functional units of the kidney.

Structure of Nephron

59. What is the structure of the nephron? Make a diagram of the nephron and label its parts.
Ans: Nephrons are the tubules where urine is formed. Each nephron has two parts.

  1. Renal Corpuscle
  2. Renal Tubule.

1. Renal Corpuscle:

 This part has two structures.
  • a. Glomerulus: It is a tuft of blood capillaries
  • b.  Bowman’s capsule: It is a cup-shaped structure.

ii. 2. Renal Tubule: This part has three structures

  1. The first coiled part is called the proximal tubule.
  2. Second part is U-shaped and it is called the Loop of Henle.
  3. The last part renal tubule is also coiled and it is called the distal tubule.

60. In which part of nephron filtration of blood occurs?
Ans: The filtration of blood occurs in Bowman’s capsule.
61. Draw a diagram of Bowman’s capsule and label its parts.
62. Where does re-absorption take place?
Ans: During its passage towards the collecting duct, 99% of the filtrate is reabsorbed into the blood capillaries around the renal tubule.
63. What is the composition of urine?
Ans: 

In 100 cm3 urine there is:

  •  Water = 96 g 
  •  Urea = 2 g
  • Mineral salts (mainly NaCl) = 1.8 g
  • Other nitrogenous substances 0.2 g

64. What is the common cause of stones in kidneys?
Ans: Accumulation of salts in kidneys results in kidney stones.
65. How can we remove a stone from our kidneys?
Ans: Kidney stones can be removed by using more water, by lithotripsy, or by surgery.
66. What is meant by lithotripsy?
Ans: It is a treatment that is used to remove medium-sized stones from the kidney.
Shockwaves break the stones into small pieces which are passed out of the body through urine. It is a permanent treatment.

Renal Failure

67. What is renal failure?
Ans: Renal failure is the complete or partial failure of kidneys to work.
68. What are the main causes of renal failure?
Ans: The main causes of renal failure are long-term infections, diabetes mellitus, and hypertension.
69. What are the treatments for renal failure?
Ans: Dialysis and kidney transplant are the treatments for renal failure.
70. What is dialyzer?
Ans: A machine that is used to clean blood is called a dialyzer.
71. What is dialysis? What is its procedure?
Ans: Cleaning blood by artificial methods is called dialysis.
It is done by a machine called a dialyzer. The blood of the patient is passed through the dialyzer which contains dialysis fluid. Blood flows through the tubes of the dialyzer and dialysis fluid flows around these tubes. The waste materials move from blood to the dialysis fluid. The cleaned blood is returned to the body.

72. What do you mean by a kidney transplant?

Ans: In this method, a healthy kidney is grafted into the body of the patient. The donor of the kidney may be a close relative. This method is used at the last stage of kidney failure.
73. Why a motorcyclist is advised to wear a helmet?
Ans: Human brain is a very sensitive part. A small accident may hurt the brain which may result in loss of memory or madness. That is why it is advised to wear a helmet while riding the motorcycle.
74. A person met an accident in a car. When he was brought to the hospital he did not know even his name. What would have happened to him? Relate your answer concerning your nervous system.
Ans: Speaking, thinking, and memory are controlled by the forebrain. He got an injury in his forebrain and his memory was affected.
75. The table below shows the list of your daily activities. Write the name of that part of the brain which is controlling this activity.

  1.  Sleeping Hindbrain                          (Pons)
  2.  Brushing your teeth Forebrain        (Cerebrum)
  3. Taking the breakfast Forebrain      ( Hypothalamus)
  4. Balancing your body.                      Hindbrain (Cerebellum)
  5. Taking deep breaths                       Hindbrain (Medulla Oblongata)

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