Class 10 Science Chapter 6 MCQ

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

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.

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.

There are two adrenal glands in our body one on top of each kidney. The adrenal glands make adrenaline hormones when we are faced with any dangerous situation, then our nervous system stimulates the adrenal glands to secrete more adrenaline hormone into our blood, then we can react according to the situation.

Pituitary gland is known as “master gland” and adrenal glands are often called “glands of emergency”

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”.

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.

Abscisic acid is responsible for the formation of layer of abscission. This layer disconnects the living tissue of leaf from the other parts.

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.

The growth of a pollen tube towards ovule is in induced by a chemical (sugar) substance secreted by the ripened stigma of flower into the style towards ovary. It is an example of chemotropism, pollen grain response to a stimulus by growing a pollen tube in downward direction, towards ovule for fertilization.

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

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).

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.

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