Chapter 7 – Control and Coordination

1) Define Phytohormones & classify them accordingly.

Ans – Phytohormones (also known as plant hormones) are naturally happening organic compounds that monitor various physiological processes in plants, including growth, development & responses to environmental stimuli. These hormones are produced in small quantities & can impact plant functions.

The main variants of phytohormones have auxins, cytokinins, gibberellins, abscisic acid & ethylene.

2) Why does the brain gain importance during reflex action?

Ans – In a reflex action, the brain doesn’t directly control the response & still has a vital job. Reflex actions, like quickly pulling your hand away from something hot, happen extremely fast due to the signals going straight to the spinal cord before returning to your muscles without stopping at the brain initially. It ensures you react quickly to adverse situations.

However, the brain gets the information about what happened right after the reflex & you understand why you changed while remembering it for the next time. Also, the brain can often modify reflexes to make them stronger or weaker based on the situation.

3) How do control and coordination occur between the environment and plants?

Ans – Plants control and coordinate their actions in response to the environment using special chemicals called hormones. These are of two types –

• Growth dependant- happens due to cell divisions
• Growth independent- occurs due to change of water

These hormones help plants grow, move, and adapt to changes accordingly.

4) What role do endocrine glands play in maintaining feedback control?

Ans – Endocrine glands play a key role in maintaining feedback control in our bodies by producing hormones, which are special chemicals that act like messengers. These hormones travel through the bloodstream to different organs and tissues to help control various functions, like growth, metabolism, and mood.

There are two basic feedback systems –

• Positive feedback – This encourages a departure from the desired values’ means. For example, if your blood sugar is too high, the pancreas (an endocrine gland) releases insulin to help lower it.
• Negative feedback – This encourages a deviation from the ideal mean value. For example, If blood sugar is too low, the pancreas releases glucagon to raise it.

This feedback system ensures that our body’s internal environment stays balanced and stable, even when things change around us.

5) How does chemical coordination occur in animals?

Ans – Chemical coordination in animals happens through a special system called the endocrine system. Think of it like a messaging system in our bodies. Glands in the endocrine system, like the thyroid and adrenal glands, produce chemicals called hormones. These hormones travel through the bloodstream to different body regions, delivering important messages.

For example, if you’re scared, your adrenal glands release adrenaline to make your heart beat faster and give you energy. This chemical coordination helps our bodies respond to changes, grow, and stay healthy.

6) What do receptors do in our bodies? What happens when they stop working efficiently?

Ans – Receptors in our bodies act like sensors, helping us detect changes in our environment and within our bodies. They’re like the eyes and ears of our cells, sending messages to our brain so we can respond appropriately.

When receptors stop working efficiently, it can cause problems. For example, if the receptors in our eyes don’t work well, we might have trouble seeing clearly, and if the receptors in our taste buds aren’t working properly, food might not taste as good as it used to. Efficient receptors are crucial for our senses and overall health.

7) What role does the synapse play between two neurons?

Ans – The synapse between two neurons, like a tiny gap where messages jump from one neuron to another. When an electrical signal, called an action potential, reaches the end of the first neuron, it releases special chemicals called neurotransmitters into the gap.

These neurotransmitters travel across the gap and attach to receptors on the next neuron like a key fitting into a lock. This triggers the second neuron to fire its electrical signal or stop firing. Once the message is passed, the neurotransmitters are either broken down or taken back up by the first neuron to be used again. This process allows our brain and body to communicate and control everything we do, from moving to thinking.

8) List the differences between involuntary and reflex actions.

Ans – Here are the differences between involuntary and reflex actions.

Involuntary actions	Reflex actions
This refers to muscle movements that don’t require thinking.	Rapid & spontaneous action that occurs as a response to stimuli.
Controlled by the brain	Controlled by the stimuli.
E.g.: Breathing and digestion.	E.g.: When you touch something hot & instantly withdraw it.

9) What is a “nerve impulse”? Which neuron structure helps in a nerve impulse?

Ans – Also known as an action potential, the nerve impulse is an electrical signal transported along a neuron’s membrane. It’s like a wave of electricity that carries information from one part of the body to another.

1. Towards the cell body

Dendrites assist in conducting a nerve impulse toward the cell.

2. Away from the cell body

Axon assists in conducting a nerve impulse away from the cell.

10) List the distinctions between nervous & hormonal control mechanisms.

Ans – Check out the variations between them:

Nervous control	Hormonal control
Controlled by the nervous system	Controlled by hormones.
The response is short-termed	The response is long termed
Not specific	Highly specific
Composed of neurons	Composed of secretory cells
Messages are transferred in the form of electric impulses	Messages are transferred in the form of chemical signals
Messages are transferred via nerve fibers	Messages are transferred along the bloodstream
Messages are quick to travel	Messages travel slowly