Describe the central nervous system in human beings.
The central nervous system in human beings is highly developed. It consists of (i) brain and (ii) spinal cord. Brain is the highest coordinating centre in the body. It is protected by a bony box in the skull called the cranium. Brain is covered by three membranes, called meninges. The space between the membranes is filled by cerebrospinal fluid that protects the brain from mechanical shocks.
The brain is broadly divided into three regions (i) Fore brain (ii) Mid brain and (iii) Hind brain.
Each region of the brain consists of various centers. The fore brain includes cerebrum and olfactory lobes.The cerebrum is the most complex and specialized part of the brain. It consists of two cerebral hemispheres.The cerebrum has sensory areas where information is received from sense organs. Similarly, there is the motor area from where impulses are sent to the muscle or effectors organs. In the cerebrum, specific regions for each kind of stimulus and its response are located. Pairs of cranial nerves arise from the brain. The hind brain consists of three centers, cerebellum, pons and medulla oblongata. Medulla oblongata is the regulating centre for swallowing, coughing, sneezing and vomiting. The pons takes part in regulation of respiration. Coordination and the adjustment of movement and posture are under the control of cerebellum.
Spinal cord is a part of the central nervous system, which lies in the vertebral canal. It is a downward continuation of the medulla oblongata. In the spinal cord, the arrangement of white and grey matter is reverse of that of the brain. The grey matter containing cytons is the inner region and white matter containing myelinated axons is the outer. In the centre of the spinal cord runs a small central canal. This central canal, which runs the entire length of the spinal cord, is continuous with the ventricles of the brain. The spinal cord in transverse section has H-shaped structure because it has fissures on the ventral and the dorsal sides. The dorsal fissure almost reaches the gray matter while the anterior median fissure falls short of it. Spinal cord gives off 31 pairs of nerves.
Give the scientific terms used to represent the following :
(a) Bending of a shoot towards light.
(b) Growing of roots towards the earth.
(c) Growth of a pollen tube towards ovule.
(d) Bending of roots towards water.
(e) Winding of tendril around a support
A potted plant is made to lie horizontally on the ground. Which part of the plant will show
(i) positive geotropism?
(ii) negative geotropism?
Which part of the brain controls involuntary actions? Write the function of any two regions of it.
When you smell a favourite food your mouth begins to water (that is, you secrete saliva). Write down what the following are examples of :
(a) the smell of the food
(b) the cells in your nasal passages which perceive the smell
(c) the gland which is stimulated to secrete saliva.
Name the plant hormones which help/promote (i) cell division (ii) growth of
the stem and roots?
Name the plant hormones which are responsible for the following effects :
(a) falling of leaves
(b) opening of stomata
(c) bending of stem towards light (d) closing of stomata
(a) Name the hormones secreted by the following endocrine glands :
(i) Thyroid gland (ii) Parathyroid glands (iii) Pancreas (iv) Adrenal glands
(b) Write the functions of testosterone and oestrogen hormones.
Answer the following:
(a) Which hormone is responsible for the changes noticed in females at puberty?
(b) Dwarfism results due to deficiency of which hormone?
(c) Blood sugar level rises due to deficiency of which hormone?
(d) Iodine is necessary for the synthesis of which hormone?
Which one term in each of the following includes the other three ?
(a) thyroid, ductless gland, thymus, pituitary, ovary
(b) adrenalin, insulin, hormone, thyroxine, estrogen
Smita's father has been advised by a doctor to reduce his sugar intake.
Give one example of the movement of a plant part which is caused by the loss of water (or migration of water).
Why is the folding up of the leaves of a sensitive plant on touching with a finger not a tropism ?
Which halogen element is necessary for the making of thyroxine hormone by the thyroid gland ?
Fill in the following blanks with suitable words :
(a) The two examples of effectors are…………. and………………
(b) Our…………. system allows Us to react to our surroundings. Information from receptors passes
along…………. neurons to our brain. Our brain sends impulses along………… neurons to our muscles.
(c) A neuron which carries an impulse to the brain is called a……………….
(d) The neuron which carries a message for action to a muscle or gland is known as a……………….
State the functions of the following hormones :
(a) Thyroxine (b) Adrenaline (c) Growth hormone
A person walks across a room in barefeet and puts his foot on a drawing pin lying on the floor. He lets out a cry. Explain what happens in his nervous system in bringing about this response.
Nervous and hormonal system together perform the function of control and coordination in human beings. Justify the statement.
What is chemotropism? Give one example. Name any two plant hormones and mention their functions.
Name the plant hormones which help/promote (i) cell division (ii) growth of
the stem and roots?
What is the stimulus in : (a) phototropism ? (b) geotropism ? (c) chemotropism ? (d) hydrotropism ? (e) thigmotropism ?
Which of the following is a growth movement and which is not ?
(a) folding up of leaves of sensitive plant on touching with hand.
(b) folding up of petals of dandelion flower when light fades.
(a) What does a root do in response to gravity ? What is this phenomenon known as ?
(b) What does a stem (or shoot) do in response to light ? What is this phenomenon known as ?
Name the plant organs which are :
(a) positively phototropic (b) positively geotropic
(c) negatively geotropic (d) positively hydrotropic
(a) What is meant by ‘tropisms’ (or tropic movements) ? Explain with an example.
(b) What are the different types of tropisms ? Define each type of tropism. Write the name of stimulus in each case.
(c) How do tropisms differ from nasties (or nastic movements) ?
Name one gland each :
(a) which acts only as an endocrine gland.
(b) which acts only as an exocrine gland.
(c) which acts both as an endocrine gland as well as an gxocrine gland.
Write the names of all the major endocrine glands present in the human body. Which of these glands also function as exocrine glands ?
(a) Draw the structure of neuron and label cell body and axon.
(b) Name the part of neuron:
(i) where information is acquired
(ii) through which information travels as an electrical impulse.
Name any three endocrine glands in human body and briefly write the function of each of them.
What are 'hormones'? State one function of each of the following hormones:
(i) Thyroxine (ii) Insulin
A young green plant receives sunlight from one direction only. What will happen to its shoots ?