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.
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?
(a) Name the two main constituents of the Central Nervous System in human beings.
(b) What is the need for a system of control and coordination in human beings?
(a) What does a plant root do in response to water ? What is this phenomenon known as ?
(b) What happens to the moonflower (i) during daytime, and (ii) at night ? What is this phenomenon known as ?
Which halogen element is necessary for the making of thyroxine hormone by the thyroid gland ?
(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.
What is the function of insulin hormone ? What type of patients are given insulin injections ?
What are meanings? What are their functions? Name the fluid, which is filled in between meanings.
What is synapse ? In a neuron cell how is an electrical impulse created and what is the role of synapse in this context ?
Which part of the brain controls involuntary actions? Write the function of any two regions of it.
Name and explain the function of the hormone secreted by the pituitary gland in humans.
Plant parts show two types of movements, one dependent on growth and the other independent of growth. Give one example of the movement in plant parts :
which depends on growth
which does not depend on growth
(a) What does a Mimosa pudica plant do in response to touch ? What is this phenomenon known as ?
(b) What happens to the dandelion flower (z) during daytime, and (ii) at night ? What is this phenomenon known as ?
Name the plant organs which are :
(a) positively phototropic (b) positively geotropic
(c) negatively geotropic (d) positively hydrotropic
What are the scientific names for the following receptors in animals ?
(a) receptors for light
(b) receptors for heat
(c) receptors for sound
(d) receptors for smell
(e) receptors for taste
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.
(a) What substances are made by endocrine glands ?
(b) What is the function of receptors and effectors in our body ?
(a) The human brain can be broadly divided into three regions. Name these three regions.
(b) What is cranium ? What is its function ?
In what ways are puberty and adolescence result of the activity of some glands in the human body ?
What does CNS stand for ? Which part of CNS : (a) consists of two cerebral hemispheres, and (b) has spinal nerves attached to it ?
Which hormone :
(a) prepares the body for action ?
(b) controls the amount of glucose in blood ?
(c) gives boys a deep voice ?
(d) gives girls soft skin ?
Nervous and hormonal system together perform the function of control and coordination in human beings. Justify the statement.
State how concentration of auxin stimulates the cells to grow longer on the side of the shoot which is away from light ?
(a) How is brain protected from injury and shock?
(b) Name two main parts of hind brain and state the functions of each.
What is chemotropism? Give one example. Name any two plant hormones and mention their functions.
(a) Name the two main constituents of the Central Nervous System in human beings.
(b) What is the need for a system of control and coordination in human beings?