Class 10 Science Chapter 6 MCQ

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

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.

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

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.

Pituitary gland is present just below the brain. The gland secretes a number of hormones. One of the hormone secreted by pituitary gland is growth hormone. The growth hormone controls the growth of the human body.

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.

The brain is broadly divided into three regions: forebrain, midbrain and hindbrain. The forebrain consists mainly of cerebrum. The midbrain does not have any further division. The hindbrain consists of 3 centres called, pons, cerebrum and medulla.

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 information acquired at the end of the dendritic tip of a neuron causes a chemical reaction that produces an electrical impulse. This impulse travels from dendrite to cell body and then along axon to its end.

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

Synapses actually act like one-way valves. This is because the chemical substance is present on only one side of the gap. Due to this, the nerve impulses or messages through a particular set of neurons can go across only from one side which contains the chemical substance. In this way, synapses ensure that nerve impulses travel in only one direction through a particular set of 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.

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).

A growth movement of a plant part in response to an external stimulus, towards or away from it is called tropism. Common stimuli in environment are given. Such as: Light is the type of phototropism, gravity is the type of geotropism, touch is the type of thigmotropism, chemical is a type of chemotropism, and water is a type of hydrotropism.

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.

A microscopic gap between a pair of adjacent neurons over which nerve impulses pass when going from one neuron to the next is called synapse. The neurons carry messages in the form of electrical signals called “electrical impulses” or “nerve impulses”. The dendrites pick up the impulses from receptor and pass them to the cell body, and then along the axon to its end. At the axonal end, electrical impulses set off release of some chemicals that crosses the gap or synapse and start a similar impulse in dendrite of the next neuron.

The neurons carry messages in the form of electrical signals called “electrical impulses” or “nerve impulses”. The dendrites pick up the impulses from receptor and pass them to the cell body, and then along the axon to its end. At the axonal end, electrical impulses set off release of some chemicals that crosses the gap or synapse and start a similar impulse in dendrite of the next neuron.