Control and Coordination-QnA

Q1: What is a reflex action?

An automatic, quick response to a stimulus, often protective in nature.

Q2: Name the main control center of the human body.

The brain.

Q3: What hormone does the thyroid gland release?

Thyroxine.

Q4: Which part of the brain controls balance?

Cerebellum.

Q5: Give an example of a plant hormone.

Auxin.

Q6: What is phototropism?

Growth movement of plants towards light.

Q7: Which system coordinates voluntary actions?

Nervous system.

Q8: Name a chemical used in iodised salt.

Iodine.

Q9: What is the function of insulin?

It reduces blood glucose level.

Q10: Which part of brain regulates heartbeat?

Medulla oblongata.

Q11: What structure transmits messages from nerves to the brain?

Spinal cord.

Q12: Name the gland called 'master gland.'

Pituitary gland.

Q13: Which hormone is responsible for 'fight or flight'?

Adrenaline.

Q14: What is geotropism?

Movement of plant parts in response to gravity.

Q15: State one difference between voluntary and involuntary actions.

Voluntary actions are under conscious control, involuntary are automatic.

Q1: Why is the use of iodised salt advisable?

It prevents thyroid problems like goitre by ensuring thyroid hormone synthesis.

Q2: How does our body respond when adrenaline is secreted into the blood?

Heart rate increases, blood supply to muscles increases preparing body for emergencies.

Q3: What are plant hormones? Name two.

Chemicals regulating growth and responses; e.g., auxin, gibberellins.

Q4: Mention the components of a neuron.

Cell body, dendrites, axon.

Q5: State the function of the cerebral cortex.

Controls thinking, intelligence, memory, and voluntary actions.

Q6: Why is coordination necessary in living organisms?

To integrate body functions for survival and response to stimuli.

Q7: How are involuntary actions and reflex actions different?

Involuntary actions are automatic (e.g., heartbeat); reflex actions are quick responses (e.g., hand withdrawal).

Q8: What is the role of sensory neurons?

Carry messages from receptors to brain/spinal cord.

Q9: Compare nervous and hormonal coordination in animals.

Nervous is fast, electrical; hormonal is slower, chemical, long-lasting.

Q10: What is chemical coordination?

Control via hormones acting as chemical messengers.

Q1: Explain the structure of the human brain.

The brain has three main parts:

1. Forebrain
   • Main role: Thinking and voluntary actions.
   • Components:
     • Cerebrum: The largest part, responsible for activities such as reading, speaking, reasoning, memory, and voluntary movement. Separate areas handle sensory information (hearing, smell, sight, touch, taste) and their interpretation.
     • Hypothalamus: Controls hunger, thirst, and body temperature.
     • Pituitary gland: Known as the “master gland” because it regulates many bodily functions through hormones.
2. Midbrain
   • Main role: Acts as a communication link.
   • Functions: Controls reflex actions related to vision and hearing. It coordinates visual and auditory information and helps regulate movement of the eyes and eyelids.
3. Hindbrain
   • Main role: Controls involuntary actions (actions automatic to survival).
   • Components:
     • Cerebellum: Maintains balance, coordinates precise movements, and helps posture.
     • Pons and Medulla oblongata: Together called the brainstem. They control vital involuntary functions like breathing, heartbeat, blood pressure, and digesting food.

Protection and Support

• Skull: Bony case protecting the brain.
• Meninges: Three protective membranes covering the brain.
• Cerebrospinal Fluid (CSF): Cushions the brain and supplies nutrients.

Q2: Describe reflex action pathway and its importance.

Reflex action is a quick, automatic response to a stimulus that does not involve conscious thought. It helps protect us from sudden or dangerous situations, like pulling your hand away from a hot object before you even realize it’s hot.

Reflex Pathway (Reflex Arc)

The pathway taken by a nerve impulse during a reflex action is called a reflex arc. Here’s how it works step-by-step:

1. Stimulus and Receptor:
   A stimulus (e.g., touching something sharp or hot) is detected by receptor cells in the skin (sense organ).
2. Sensory Neuron:
   The receptor generates a nerve impulse that travels via a sensory neuron towards the spinal cord.
3. Spinal Cord and Relay Neuron:
   In the spinal cord, the sensory neuron passes the signal to a relay neuron (interneuron), which connects to the motor neuron without involving the brain for immediate action.
4. Motor Neuron:
   The relay neuron passes the impulse to a motor neuron.
5. Effector:
   The motor neuron carries the signal to an effector organ (usually a muscle or a gland), producing a rapid response, such as muscle contraction to withdraw the hand.

Q3: How does nervous system help in control and coordination?

Q4: How do plants respond to stimuli?

Plant Responses to Stimuli

Plants cannot move from place to place like animals, but they do respond to changes in their environment—such as light, gravity, water, chemicals, and touch—by changing how they grow or move specific parts. This ability is part of their control and coordination system.

Mechanisms of Response

1. Tropisms (Growth-Based Responses)
   • Phototropism: Shoots grow towards light to maximize photosynthesis. The hormone auxin moves to the shaded side, causing those cells to elongate and the stem to bend towards the light.
   • Geotropism: Roots grow downward, following gravity, which helps anchor the plant and absorb water/minerals. Shoots usually grow upward, away from gravity.
   • Hydrotropism: Roots grow towards areas with more water.
   • Thigmotropism: Some plants respond to mechanical touch, e.g., tendrils of climbers curl around supports.
   • Chemotropism: Parts of the plant grow in response to chemicals; for example, pollen tubes growing towards ovules.
2. Nastic Movements (Non-Growth Movements)
   Not linked to growth or direction of stimulus. A classic example is the Mimosa pudica (Touch-me-not plant), which instantly folds its leaves when touched. This is due to changes in water content in certain cells, not growth.
3. Hormonal Control
   Plants use chemical messengers called hormones (e.g. auxins, gibberellins, cytokinin, abscisic acid) instead of nerves. These hormones help plants coordinate growth and responses to stimuli.

Importance of Plant Responses

• Survival: Helps plants survive harsh conditions (e.g., growing roots towards water, shoots towards sunlight).
• Defense: Some responses protect against injury (Mimosa folding leaves, Venus flytrap closing).
• Reproduction: Growth towards ovule or sunlight supports healthy reproduction and development.

Q5: Difference between voluntary, involuntary, reflex actions with examples.

Q1: Describe the human brain's major parts and their functions.

Forebrain controls intelligence & voluntary actions, midbrain relays signals, hindbrain manages balance and involuntary actions.

Q2: Explain how plants coordinate their growth and responses using hormones.

Plant hormones like auxin regulate tropic movements such as bending towards light or roots growing downward in response to gravity.

Q3: Describe the pathway of a reflex action and its significance in human survival.

Reflex arc allows fast, automatic response bypassing brain to protect from injury (e.g., withdrawing hand from hot object).

Q4: Compare nervous and endocrine systems in animals emphasizing their control mechanisms.

Nervous system uses fast electrical signals for immediate response; endocrine system uses slower chemical hormones for sustained regulation.

Q5: Discuss feedback mechanisms in hormone regulation with examples of insulin and thyroxine.

Hormones regulate processes via feedback: insulin lowers blood sugar when high; thyroxine controls metabolism, adjusting to body needs.

Q1: What is the difference between a reflex action and walking?

A reflex action is an immediate, involuntary, and automatic response to a stimulus that does not involve thinking and is often controlled by the spinal cord. It is meant for protecting the body from sudden changes in the environment (for example, withdrawing the hand when touching something hot).

Walking, on the other hand, is a voluntary action. It is done consciously with thought and planning, and is controlled by the brain, especially the cerebrum. Walking involves learning, coordination, and repeated action under the control of our will, rather than an immediate reaction to a stimulus.

Q2: What happens at the synapse between two neurons?

At the synapse between two neurons, the electrical impulse generated at the end of the axon of one neuron is converted into a chemical signal using neurotransmitters (such as acetylcholine). These neurotransmitters cross the synaptic gap and bind to the membrane of the next neuron’s dendrite, where they are converted back into electrical impulses. This process allows the nerve signal to be transmitted in one direction from one neuron to another.

Q3: Which part of the brain maintains posture and equilibrium of the body?

The cerebellum is the part of the brain that maintains posture and equilibrium (balance) of the body.

Q4: How do we detect the smell of an agarbatti (incense stick)?

We detect the smell of an agarbatti when its molecules diffuse through air and enter our nose, where they stimulate specific olfactory receptors present in the nasal cavity. These receptors generate nerve impulses, which are transmitted through sensory neurons to the olfactory region of the brain. The brain then interprets these signals as the specific smell of the agarbatti.

Q5: What is the role of the brain in reflex action?

In reflex actions, the brain does not play the primary role in generating the immediate response. Reflex actions are mainly controlled by the spinal cord, which enables the body to react quickly to stimuli without waiting for signals to reach the brain. However, the brain may be informed about the reflex action after it occurs so that voluntary control or further responses can be coordinated if needed.

Q6: What are plant hormones?

Plant hormones are chemical substances produced in plants that regulate growth, development, and responses to stimuli. They help control various physiological processes such as cell division, elongation, flowering, fruiting, and responses to light and gravity.

Q7: How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?

The movement of leaves of the sensitive plant (Mimosa pudica) is a nastic movement, which occurs in response to touch and is independent of the direction of the stimulus. It is a rapid response caused by changes in turgor pressure within cells.

In contrast, the movement of a shoot towards light is a tropic movement, specifically phototropism, which is directional and occurs due to the plant's growth response towards the source of light, regulated by plant hormones.

Q8: Give an example of a plant hormone that promotes growth.

Auxin is an example of a plant hormone that promotes growth by stimulating cell elongation in stems and roots.

Q9: How do auxins promote the growth of a tendril around a support?

When a tendril touches a support, auxins accumulate on the side of the tendril that is away from the contact. This higher concentration of auxins causes the cells on that side to elongate more than the cells on the side touching the support. As a result, the tendril bends and coils around the support.

Q10: How does chemical coordination take place in animals?

Chemical coordination in animals occurs through hormones. These are chemical messengers secreted by endocrine glands directly into the bloodstream. Hormones reach specific target organs and regulate various physiological processes such as growth, metabolism, reproduction, and homeostasis, ensuring proper coordination and functioning of the body.

Q11: Why is the use of iodised salt advisable?

Using iodised salt is advisable because it provides the body with a small but essential amount of iodine, a mineral required for the normal functioning of the thyroid gland.

Without enough iodine, the thyroid cannot produce sufficient thyroid hormones, leading to disorders such as goitre (swelling of the neck), fatigue, and impaired growth and brain development, especially in children.

Therefore, adding iodine to common salt — something we consume daily — is a simple, effective, and inexpensive way to prevent iodine deficiency diseases and maintain overall metabolic and hormonal balance.

Q12: How does our body respond when adrenaline is secreted into the blood?

Q13: Why are some patients of diabetes treated by giving injections of insulin?

Some patients of diabetes are treated by giving insulin injections because their pancreas does not produce enough insulin or stops producing it altogether.

Insulin is the hormone responsible for regulating the blood sugar level by helping body cells absorb glucose from the blood.

When insulin is absent or insufficient, glucose cannot enter the cells and remains in the bloodstream, leading to high blood sugar levels.

Therefore, such patients are given insulin injections to maintain normal glucose levels in the blood and ensure that body cells receive energy for proper functioning.