(3)

The amount of water in guard cells causes change in their shape. When water enters into the guard cell, it causes the stomatal pore to open. Similarly, if the guard cells shrink as a result of water loss, the pore closes.

(3)

Statements (ii) and (iii) are wrong in their sense because sensory neurons carry signals from receptors to spinal cord and motor neurons carry signals from spinal cord to the muscles. Thus, statement (i) and (iv) are true

(4)

Cytokinin is a plant hormone that playe an important role in plant growth and development In plants, it aids embryogenesis, ell division chloroplast differentiation, and a variety of other processes

(2)

Cretinism is a condition arising from the deficiency of thyroid hormone, which causes stunted physical and mental growth. This deficiency, particularly during infancy or childhood, leads to reduced secretion of thyroxine (T4) hormone, which is critical for normal development. It is not related to the secretion levels of growth hormone or adrenaline but specifically to thyroxine produced by the thyroid gland.

(4)

The cerebellum of the brain is involved in muscle coordination, muscle tone, and balance. The medulla oblongata regulates heartbeat and controls consciousness and arousal. The cerebrum is the centre of brain for higher-order thinking functions such as learning, memory, language, and speech.

(3)

The involuntary activities are controlled by the medulla oblongata in the hind brain. Involuntary movements have a slower speed than voluntary movements. The beating of the human heart is the best example of this.

(1)

Pons is involved in respiratory control, communication between different areas of the brain, and perceptions including hearing, taste, and balance, but not in overall consciousness. The brain stem controls consciousness.

(4)

The nervous and endocrine systems in humans work together to control and coordinate all activities. Both of these systems are made up of a number of organs that work in coordinated manner.

(2)

Growth hormone is a peptide hormone that promotes growth, cell reproduction, and regeneration. Insulin is made in the pancreas by beta cells found in the Islets of Langerhans. It is essential for the absorption of blood sugar by the cells. Along with glucagon, it regulates blood sugar levels.

(1)

The adrenal glands produce adrenaline, which activates the body’s fight-or-flight response. The testes, which are responsible for the development of male sexual traits, produce testosterone. The ovaries, which are responsible for the development of female sexual traits, produce oestrogen. Thyroxine is a hormone generated by the thyroid gland to accelerate the production of oxidative metabolism in cells.

(2)

The pineal gland is a tiny gland located in the brain. Melatonin, a hormone that helps regulate sleep and wakefulness, is produced by this gland.

(4)

Iodine, not iron, is required for the synthesis of thyroxine. It controls the glucose, protein, and fat metabolism of the body. The thyroid gland produces thyroxine, which is also known as thyroid hormone.

(2)

Lack of insulin production is primarily the cause of type 1 diabetes. It occurs when insulin-producing cells are damaged or destroyed and stop producing insulin. Insulin is needed to move blood sugar into cells throughout the body. Thus the levels of the blood sugar increase drastically.

(3)

The release of oestrogen and testosterone is associated to puberty changes. In females, oestrogen is secreted from the ovary, while testosterone is secreted from the testes in males.

(4)

The central nervous system consists of the brain and spinal cord. The spinal cord is a long, tubular bundle of neurons that connects the brain to the rest of the body and transmits information.

(1)

The olfactory neurons have olfactory receptors on their surfaces. Their primary function is to detect odours.

(2)

The pituitary gland, also known as the hypophysis, is a pea-sized endocrine gland. It is a protrusion at the base of the brain, at the bottom of the hypothalamus. It is a gland which is not paired. Adrenal, ovary and testes are paired glands.

(3)

Receptor cells, which are specialised cells that produce electrical impulses in response to certain stimuli, are found in the sense organs.

(2)

Mucus in the nasal passages thickens during a cold, preventing scent molecules from reaching the olfactory receptor cells. As a result, the brain receives no information identifying the odour, making it impossible to distinguish the smell of a perfume from that of an agarbatti.

(2)

Neurons are the structural and functional unit of nervous system. They generate electrical signals called action potentials that allow them to quickly send information over large distances.

(3)

The neuroendocrine system, which consists of the nervous and endocrine systems, keeps the body coordinated. The nerve impulse generated by the neurological system activates the endocrine glands.

(4)

A cell body (also known as a soma), dendrites, and an axon are all parts of a neuron. Nerve fibres have axons and dendrites. Nissl granules, as well as other cell organelles, are found in the cytoplasm of the cell body of neurons. Myelin sheath is not a part of the neuron.

(1)

Cranium is related to head. Cranial bones (bones that surround and protect the brain) and facial bones make up the cranium (bones that form the eye sockets, nose, cheeks, jaw, and other parts of the face).

(3)

The brain is protected by cranial meninges, which are made up of three layers: an outside layer called duramater, a very thin middle layer called arachnoid, and an inner layer called piamater (which is in contact with the brain tissue).

(1)

The hypothalamus is a small region at the base of the brain within the diencephalon, lying just above the brain stem and below the thalamus. The hypothalamus plays a crucial role in many important functions, including releasing hormones, regulating body temperature, maintaining daily physiological cycles, controlling appetite, and managing sexual behaviour and emotions.

(2)

Reflex action is an automatic (involuntary) neuromuscular activity triggered by specific stimuli. Knee jerk, coughing and eyelid closing are reflex actions. Boxing is not a reflex action.

(3)

When a receptor is triggered, it sends a signal to the brain, which coordinates the response. However, sometimes a speedy response is required that does not need the use of the brain. This is referred to as a reflex action. In a simple reflex action: Sensory neuron -> Relay Neuron -> Motor neuron.

(3)

The reflex movements are controlled by the spinal cord and the brain stem in a reflex action. The glands and muscles that respond to stimuli are known as effector organs.

(3)

When the stimulus is gained, a nerve impulse is produced. The electrical and chemical changes in the cell are triggered by this stimulation.

(4)

The Autonomic Nervous System (ANS) controls visceral activity in the body, such as blood pressure, urinary bladder action, and body temperature regulation, etc. The autonomic nervous system causes involuntary responses such as breathing. Writing, talking and walking are voluntary actions that we do when we are aware of what we are doing.