SEE Science (Stimulation and Reaction) Notes

        Stimulation and Reaction

1.    What 'Reflex action'? Explain with examples.

Ans: An involuntary action performed by muscles under the direction of the spinal cord in     response to stimulus is called reflex action.

Example:

a) Immediate withdrawal of hand after touching a hot object or pin.

b) Shivering when there is cold.

c) Watering of mouth at the sight of tasty food.

d) Narrowing of pupil when strong rays of light fall on it.

A reflex action is an automatic response to a stimulus. In a reflex action, we are unaware that anything is going to happen to us.

2.    What is 'endocrine system'?

Ans: The glands which do not have any duct and pour their secretion directly into the            blood are called endocrine system.

3.    What are hormones?

Ans: Hormones are the chemical substances which control, co-ordinate and integrate the     functions of various organs of the body.

4.    Differentiate between endocrine and exocrine glands in any two points.

Ans: Any two differences between endocrine gland and exocrine gland are given below:

Endocrine gland	Exocrine gland
1. Endocrine gland does not contain duct.	1. Exocrine gland contains duct.
2. They secrets hormones.	2. They secrets enzymes.
3. They pour their secretion directly into the blood.	3. They pour their secretion through ducts into related organs.

5.    Give reason:

a) Hormones are called chemical messengers.

           Ans: Hormones are called chemical messengers because they are those chemicals who serve as means of communication among various parts of our body in a co-ordinate way.

b) Pituitary gland is called master gland.

           Ans: Pituitary gland secrets a number of hormones that controls and guides the activities of other glands. So it is also called master gland.

6.    In which part of the body the thyroid gland is found? Write name of the hormone secreted by this gland and its one function. What symptom is seen due to over secretion of that hormone?

Ans: Thyroid gland is located in the neck region in front of the trachea just below the           larynx.

The hormone produced by thyroid gland with its function is given below:

Hormone produced by Thyroid gland	One function
1. Thyroxin	* It regulated growth and development of body.                                                                                     * Ossification of bones and mental development. * It also regulate general metabolism.
2. Calcitonin	* It encourages the calcium deposition in the bone. * It also regulates the level of calcium and phosphate in blood.

Hyper secretion (over secretion) of thyroxin may cause a goiter called exophthalmic goiter. A person suffering from this disorder shows increased metabolic rate, excessive sweating and hunger, short breathing rate, rapid heartbeat, etc.

7.    Where is medulla oblongata located? Write any two function of it.

Ans:  It is the lowermost part of the brain which is located between pons-varoli and upper end of vertebral column.          

 Functions of it are

a)    Connects the body with brain.

b)   Controls the function of involuntary organs like heart, lungs, stomach etc.

8.    Write the example of chemotropism.

Ans: Growth of root towards the minerals is positive chemotropism.

        Withering of leaves is negative chemotropism.

9.    Where is pituitary gland located? Write the hormones secreted by this gland. Write their function.

Ans: It is located in the depression of sphenoid bone in the skull.

              The hormones secreted by pituitary gland are:

a)     Growth hormone – It helps in growth and development of the body.

b)     Stimulating hormone – It stimulates the development and activities of other endocrine glands.

10.  When we touch a hot iron rod, we remove our hand immediately. How does this process occur in our body? Explain.

Ans: In this event, skin is receptor, the stimulus received by the receptor organ initiates the sensory nerve impulses. The sensory nerve carries the impulses to the spinal cord through the dorsa root of spinal nerve. Now, from the spinal cord the sensory impulses changes into motor impulses. Then motor nerve carries impulses from spinal cord to effector organ i.e. muscles of hand. After getting the impulses, effector react and we remove our hand immediately.

11.  Differences between positive phototaxis and positive phototropism with example.

Positive phototaxis	Positive phototropism
1. The movement of an organism towards the stimulus of light is called positive phototaxis.	1. The movement of parts of plant towards the stimulus of light Positive phototropism.
2. It occurs both in plant and animal.	2. It occurs only in plant.

12.  Pancreas is called mixed gland, why?

Ans: Pancreas contains exocrine parts as well as endocrine parts. Exocrine part secretes enzyme which helps in the digestion and endocrine parts secrets hormone which regulates the body activity. Therefore, it is called mixed gland. 

13.  What happens if there is the lack of hormones produced by adrenal gland?

Ans: The lack of hormones produced by adrenal gland causes weakness, low blood pressure, nausea, unconsciousness and less sugar content in the blood.

14.  'Endocrine glands are very important even they are small size.' Give two reasons.

Ans: Endocrine glands are very important even they are small size because

a)     They secrete various hormones to stimulate and regulate various activities of a body.

b)     They secret sex hormones which develop secondary sexual character in male and female.

15.  Differences between sensory and motor nerve.

S.N	Sensory nerve	S.N		Motor nerve
a)	It carries impulses from sense organs to brain or spinal cord.	a)	It catties impulses from brain or spinal cord to the effector organs.
b)	Impulses carried by sensory nerve result in sensation.	b)	Impulses carried by motor nerve result in some movement or action.

16.  Root of plant grows inside soil, why?

Ans: Root of plant grows inside soil because root of plant shows positive geotropism or negative phototropism.

17.  Name the type of movement of the following:

a)     Euglena moves towards the light – Positive phototaxis

b)     Mosquito moves away from anti mosquito net – Negative chemotaxis

c)     Earthworm goes inside the soil – Negative phototaxis

d)     Cockroach moves towards dark – Negative phototaxis

e)     Antherozoids moves towards malic acid secreted by archegonium – Positive chemotaxis

18.  Which part of nervous system conduct reflex action?

Ans: Spinal cord conducts reflex action.

19.  Differences between taxis and tropism.

S.N	Taxis	S.N	Tropism
a)	The movement of an organism or their parts by changing location in response to the stimulus such as light, chemical etc.is called taxis.	a)	The movement of parts of a plant without changing their location in response to the stimulus is called tropism.
b)	It occurs both in plant and animal.	b)	It occurs only in plant.

20.  Name the hormone secreted by male and female gonads.

Ans: Hormone secreted by male gonads is Testosterone and female gonads are Oestrogen and Progesterone.

21.  An earthworm when kept on a soil it moves inside the soil, why?

Ans: An earthworm when kept on a soil it moves inside the soil because it shows negative phototaxis.

22.  Write any four effects of hypo secretion of insulin.

Ans: Any four effects of hypo secretion of insulin are:

i)  High level of sugar content in blood.

ii) Thirst and hunger.

iii) Appearance of sugar in urine.

iv) Delay in wound healing.

23.  What is tropism?

Ans: The movement of parts of a plant without changing their location in response to the stimulus is called tropism.

24.  Give an example of each of phototropism and hydrotropism.

Ans: 

Phototropism – Shoots of plants grow towards sunlight.

Hydrotropism – Roots of plants grow towards water.

25.  What is taxis?

Ans: The movement of an organism or their parts by changing location in response to the stimulus such as light, chemical etc.is called taxis.

26.  What is chemotaxis? Define positive and negative chemotaxis with examples.

Ans: The movement of an organism in response to the stimulus of chemical substances is called chemotaxis.

Positive chemotaxis: The movement of an organism towards the stimulus of chemical substance is called positive chemotaxis.

Example: The movement of antherozoids of fern plant towards the malic acid released by ovum.

Negative chemotaxis: The movement of an organism away from the stimulus of chemical substances is called negative chemotaxis.

Example: Movement of mosquito, cockroach, fly away from the insect repellants like coils, king mats, etc.

27.   Write one function each of Insulin and Progesterone hormone.

Ans:

Function of insulin:

a)     It controls the amount of sugar in the blood.

Function of progesterone:

a)     It plays an important role in ovulation and maintenance of pregnancy.

28.  Root of plants tends to move towards water. What is the type of this tropism

Ans: Root of plant tends to move towards water. It is positive hydrotropism.

29.   Give the name of glands that produce thyroxin and insulin.

Ans: The gland that produces thyroxin is thyroid gland and that produces insulin is pancreas.

30.   Give one example of positive and negative phototaxis.

Ans: Positive phototaxis – Movement of algae towards light.

       Negative phototaxis – Cockroach moves away from the source of light.

31.   What is spinal cord found? What is the function of adrenaline hormone secreted by adrenal gland? When a vase containing small plant of a flower is turned upside down and kept for few days, what effect is seen in the growth of root and stem of the plant?

Ans: Spinal cord is found in the neural canal of the vertebral column.

Function of adrenaline hormone:

a)     It maintains blood pressure and prepares body to face emergency situations like          fight, fright and flight.

                     When a vase containing small plant of a flower is turned upside down and kept for few days, the shoot grow in upward direction because shoot shows negative geotropism or positive phototropism whereas the roots grow in downward direction because root shows positive geotropism or negative phototropism.

32.   Write down any one function of cerebrospinal fluid and write where it is found.

Ans: Cerebrospinal fluid is found in the space between arachnoid and piamater.

Function of Cerebrospinal fluid:

a)     It serves as a shock absorbing medium and protects the brain and the spinal cord from jerks and shocks.

b)     It covers the brain and spinal cord.

c)     It passes nutrients to spinal cord and brain and removes wasters from there.

33.  Label the parts indicated by A, B and C in the following diagrams, write the function of A.

Ans: In the given figure,

A – Motor nerve

B- Sensory nerve

C- Receptor

Function of A: Motor nerve transmits messages from spinal cord to the effectors organs.