Class 10 Science Chapter 6 MCQ

Here, all these statements are correct. Hence, your answer will be option [D].

In human beings, nervous system and endocrine system work together to control and coordinate all the activities. Both these systems consist of a number of organs that work together in a systematic way.

Hormones are a kind of chemical messengers. A hormone is produced in one part of the body but it acts on some other part of the body. The hormones are of different types and perform different functions as per need in the body.

There are two adrenal glands, one on top of each kidney that make adrenaline hormone. Testes are paired glands present in males, secretes male sex hormone. Pituitary grand is present just below the brain and is unpaired. It is also called master gland as it secretes a number of hormones. Ovaries are paired glands present in females, secretes female sex hormones.

Testosterone is the male sex hormone. It regulates male accessory sex organs. It is responsible for secondary sexual characters like moustache, beard, etc. thus, increasing fertility in males.

Deficiency of growth hormone in childhood cause dwarfism while excessive secretion causes gigantism. Deficiency of thyroxine cause goitre. Adrenaline is secreted in small amounts all the time but is secreted in large amount to prepare our body for action during fight or flight.

Iodine is necessary for the synthesis of thyroxine hormone, deficiency of it in the diet of a person produces less thyroxine hormone and causes a disease known as goitre. The main symptom of goitre is that the neck of the person appears to be swollen (due to the enlargement of thyroid gland situated in the neck).

During cold, mucus in nasal passage becomes too thick, so that order molecules can’t reach the olfactory receptor cells. Thus, brain receives no signal identifying the odour, and so the smell of a perfume cannot be differentiating from that of an “Agarbatti”.

Involuntary action are those actions that are not under our direct control such as heartbeat, breathing, Peristatic movement etc. These are controlled by medulla. Chewing is under voluntary control and controlled by lobes present in “Cerebral cortex”.

The nervous system is made up of the longest special cell called neurons.

There are mainly two types of nerves in our body, “Cranial nerve” and “Spinal nerves”. The “Cranial nerves” connect all the parts in the head directly to brain. The “Spinal nerves” connect all the remaining parts of the body like muscles and skin to the spinal cord. But there is a also third type of nerves, called visceral nerves. Most of the visceral nerves connect the internal organs of the body to spinal cord though some also connect to “Brain”.

The pathway or route taken by nerve impulse in a reflex action is called reflex arc. Reflex arcs allowed “Rapid response”.

Tendrils are the thin thread-like groups on the stem or leaves of climbing plants. These are sensitive to touch of other parts objects (i.e. thigmotropic). When a tendril touches an object, then the site in contact with object grows slowly than its other side, (i.e. rapid cell divisions in cells that are away from the support). This causes the tendril to bend towards the object by growing towards it, wind around object and cling to it.

The shape of guard cells changes due to amount of water in them. The guard cell swell when water flows into them, causing the stomatal pore to open. Similarly, the pore closes if the guard cells shrink, due to the loss of water in them.

Here, all these statements are correct. Hence, your answer will be option [D].

The plant stem response to light and bends towards it due to the action of “Auxin hormones”.

Abscisic is a growth inhibitor hormone. It reverses the growth promoting effects of auxins and gibberellins. It causes dormancy of seeds, wilting of leaves, closing of stomata etc.

Cerebellum controls the voluntary action e.g. posture. The cerebrum (part of forebrain) is the main thinking part of the brain. It coordinates the voluntary action of the body. It has different areas for performing different functions such as centres of hearing, smell, memory etc. The hindbrain consists of pons (takes part in regulating respirations), cerebellum (helps in maintaining posture and balance the body) and medulla that controls involuntary actions such as breathing etc. The midbrain controls reflex movements.

The cerebrum (part of forebrain) is the main thinking part of the brain. It coordinates the voluntary actions of the body. It has different areas for performing different functions such as centres of hearing, smell, memory, etc. The hindbrain consists of pons (takes part in regulating respiration), cerebellum (helps in maintaining posture and balance of body) and medulla that controls involuntary actions such as breathing etc. The midbrain controls reflex movements.

The statement is false as sensory neuron carry signals from receptors to spinal cord. The statement is false as motor neurons carry signals from spinal cord to effectors. The pathway taken by nerve impulse in a reflex action is called the reflex arc. A reflex action is involuntary action in response to a stimulus e.g. coughing, sneezing, etc. It follows a specific pathway as given below: Stimulus → Receptors → Spinal cord → Effector → Response