Class 10 Science Chapter 7 | Control and Coordination Class 10 Notes

The Nervous System:

The nervous system is a complex network of specialized cells called neurons (nerve cells) that transmits signals to control and coordinate bodily functions. It is divided into two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS).

Peripheral Nervous System:

Central Nervous System (CNS):

The CNS consists of the brain and spinal cord. The brain is the control center of the body, responsible for processing sensory information, coordinating movements, regulating emotions, and controlling thoughts. The spinal cord is the main communication pathway between the brain and the body. It transmits nerve impulses, controls reflexes, and supports the body.

Peripheral Nervous System (PNS):

The PNS connects the CNS to the rest of the body. It consists of cranial nerves and spinal nerves. Cranial nerves carry sensory information from the head and face to the brain and motor signals from the brain to muscles in the head and neck. Spinal nerves carry sensory information from the body to the spinal cord and motor signals from the spinal cord to muscles and glands throughout the body.

Neurons: The Basic Units of the Nervous System

The basic structural and functional units of the nervous system are neurons. Neurons are long, thin cells that transmit electrical and chemical signals to communicate with other neurons and effector cells, such as muscles and glands.

Types of Neurons:

There are three main types of neurons:

1. Sensory neurons: Carry sensory information from the body to the CNS
2. Motor neurons: Carry motor signals from the CNS to muscles and glands
3. Interneurons: Connect sensory neurons to motor neurons within the CNS

Nerve Impulse Conduction:

Nerve impulses are electrical and chemical signals that travel along the length of neurons. The conduction of nerve impulses involves several processes:

• Resting potential: The neuron is in a state of relative inactivity, with a negative charge inside the cell membrane and a positive charge outside.
• Action potential: When a stimulus triggers the neuron, a rapid change in electrical potential occurs, causing the charge inside the membrane to become positive. This wave of electrical depolarization travels along the axon.
• Refractory period: After the action potential, the neuron is in a brief refractory period, during which it cannot generate another action potential.

Reflex Actions:

Reflex actions are involuntary, rapid responses to stimuli. They do not involve conscious thought and are mediated by the spinal cord. Reflexes help to protect the body from harm and maintain homeostasis.

Central Nervous System (CNS):

The central nervous system (CNS) is the control center of the body, responsible for processing sensory information, coordinating movements, regulating emotions, and controlling thoughts. It consists of two main parts: the brain and the spinal cord.

Brain:

The brain is the most complex organ in the human body. It is made up of billions of neurons and is divided into several major regions, each with specific functions:

• Cerebrum: The largest part of the brain, responsible for higher-order functions such as consciousness, thought, memory, language, and emotion.
• Cerebellum: Coordinates movements, maintaining balance and posture.
• Brainstem: Controls essential functions such as breathing, heart rate, and blood pressure.
• Thalamus: Relays sensory information to the cerebrum and controls arousal and sleep.
• Hypothalamus: Regulates body temperature, hunger, thirst, and emotions.

Spinal Cord:

The spinal cord is a long, thin tube of nervous tissue that extends from the brain to the lower back. It serves as the main communication pathway between the brain and the body, transmitting nerve impulses and controlling reflexes.

Functions of the CNS:

The CNS has a wide range of functions, including:

• Processing sensory information: The CNS receives sensory information from the body through the PNS and interprets it to create a perception of the environment.
• Coordinating movements: The CNS sends signals to the muscles to control movement, allowing us to perform actions such as walking, talking, and writing.
• Regulating emotions: The CNS plays a role in regulating emotions, influencing our feelings and behaviors.
• Controlling thoughts: The CNS is responsible for higher-order cognitive functions such as thought, memory, and language.

Peripheral Nervous System (PNS):

The peripheral nervous system (PNS) is the part of the nervous system that lies outside the brain and spinal cord. It consists of nerves and ganglia, which are groups of nerve cells that are located outside the central nervous system (CNS). The PNS is responsible for connecting the CNS to the rest of the body, transmitting sensory information from the body to the CNS and motor signals from the CNS to muscles and glands.

Types of Nerves in the PNS:

There are two main types of nerves in the PNS: cranial nerves and spinal nerves.

• Cranial nerves (CN) are nerves that originate from the brain. There are 12 pairs of cranial nerves, each with a specific function. Some cranial nerves carry sensory information from the head and face to the brain, while others carry motor signals from the brain to muscles in the head and neck.
• Spinal nerves are nerves that originate from the spinal cord. There are 31 pairs of spinal nerves, each with a specific sensory and motor distribution. Spinal nerves carry sensory information from the body to the spinal cord and motor signals from the spinal cord to muscles and glands throughout the body.

Sensory Neurons and Motor Neurons in the PNS:

The PNS contains two main types of neurons: sensory neurons and motor neurons.

• Sensory neurons are specialized to receive information from the environment and transmit it to the CNS. They have receptors that can detect different types of stimuli, such as light, sound, touch, and pain.
• Motor neurons are specialized to transmit signals from the CNS to muscles and glands. They receive signals from other neurons in the CNS and then use these signals to activate muscles or glands.

Reflexes:

Reflexes are rapid, involuntary responses to stimuli that are mediated by the spinal cord. They do not involve conscious thought and are important for protecting the body from harm and maintaining homeostasis. For example, the knee-jerk reflex is a reflex that helps to protect the leg from injury. It involves a sensory neuron that detects a tap on the knee tendon, a motor neuron that activates the quadriceps muscle, and a connecting interneuron that relays the signal between the sensory neuron and motor neuron.

Autonomic Nervous System:

The autonomic nervous system (ANS) is a division of the PNS that controls involuntary functions, such as heart rate, blood pressure, digestion, and breathing. It is divided into two main branches: the sympathetic nervous system and the parasympathetic nervous system.

• The sympathetic nervous system is responsible for the “fight-or-flight” response, which is a physiological reaction to danger or stress. It causes an increase in heart rate, blood pressure, and breathing and prepares the body to take action.
• The parasympathetic nervous system is responsible for the “rest-and-digest” response, which is a physiological state of relaxation and conservation of energy. It decreases heart rate, blood pressure, and breathing and promotes digestion and other bodily functions that are important for rest and recovery.

The Endocrine System:

Alongside the nervous system, the endocrine system plays a crucial role in maintaining homeostasis in living organisms. It comprises a network of endocrine glands that secrete hormones, which are chemical messengers that travel through the bloodstream to target organs and tissues. Hormones regulate a wide range of bodily functions, influencing growth, development, metabolism, reproduction, and stress response.

Major Endocrine Glands:

The major endocrine glands in the human body include:

1. Pituitary Gland: Often referred to as the “master gland,” the pituitary gland sits at the base of the brain and controls the activity of other endocrine glands. It produces various hormones, including growth hormone, thyroid-stimulating hormone (TSH), and adrenocorticotropic hormone (ACTH).
2. Thyroid Gland: Located in the neck, the thyroid gland produces thyroid hormones, which regulate metabolism, growth, and development.
3. Parathyroid Glands: Found embedded in the thyroid gland, the parathyroid glands produce parathyroid hormone, which maintains calcium levels in the blood.
4. Pancreas: Situated behind the stomach, the pancreas functions as both an endocrine and exocrine gland. It produces insulin and glucagon, hormones that regulate blood sugar levels.
5. Adrenal Glands: Perched atop the kidneys, the adrenal glands produce a variety of hormones, including cortisol, adrenaline, and aldosterone. These hormones are involved in stress response, energy regulation, and blood pressure control.
6. Gonads: The gonads, consisting of the ovaries in females and the testes in males, are responsible for reproductive function. The ovaries produce estrogen and progesterone, while the testes produce testosterone.

Hormone Action and Regulation:

Hormones exert their effects by binding to specific receptors on target cells. Once bound, hormones trigger a cascade of events within the cell, leading to changes in cellular function. Hormone secretion is regulated by various factors, including feedback mechanisms that help maintain homeostasis.

Positive Feedback Mechanism: In a positive feedback loop, an increase in hormone levels stimulates further hormone production, amplifying the initial effect. This mechanism is often observed in short-term processes, such as blood clotting.

Negative Feedback Mechanism: In contrast, a negative feedback loop occurs when an increase in hormone levels triggers the release of another hormone or signal that inhibits further hormone production. This mechanism is more common and helps maintain stable hormone levels and prevent overproduction.

Integration with the Nervous System:

The endocrine and nervous systems work together to coordinate body functions. The nervous system can directly stimulate hormone secretion, and hormones can influence neural activity. This integration ensures a coordinated response to various stimuli and maintains the body’s internal balance.

Integration of Nervous and Endocrine Systems:

The nervous system and endocrine system work together to maintain homeostasis in the body. Homeostasis is the state of internal equilibrium in which an organism maintains a stable internal environment despite external changes. The two systems communicate with each other to regulate various body processes, such as growth, development, metabolism, and reproduction.

Nervous System Regulation of Hormone Secretion:

The nervous system can regulate hormone secretion in several ways. For instance, the hypothalamus, a part of the brain, directly controls the pituitary gland, often referred to as the “master gland” of the endocrine system. The hypothalamus releases hormones that stimulate or inhibit the release of hormones from the pituitary gland. These pituitary hormones, in turn, regulate the activity of other endocrine glands throughout the body.

Hormonal Influence on Neural Activity:

Hormones can also influence neural activity. Some hormones, such as cortisol and epinephrine (adrenaline), can increase alertness and enhance cognitive function. Other hormones, such as melatonin, can promote relaxation and sleepiness. Hormones can also influence mood and behavior.

Examples of Integrated Action of Nervous and Endocrine Systems:

• Regulation of blood sugar levels: The nervous system and endocrine system work together to maintain blood sugar levels within a narrow range. When blood sugar levels fall too low, the hypothalamus releases a hormone called glucagon, which signals the liver to release stored glucose into the bloodstream. Conversely, when blood sugar levels rise too high, the pancreas releases insulin, which helps cells take up glucose from the bloodstream.
• Stress response: The stress response, also known as the “fight-or-flight” response, is a coordinated effort by the nervous and endocrine systems to prepare the body for danger or stress. The sympathetic nervous system releases hormones such as epinephrine and norepinephrine, which increase heart rate, blood pressure, and breathing. Simultaneously, the adrenal glands release cortisol, a hormone that provides energy and helps the body cope with stress.
• Sleep-wake cycle: The sleep-wake cycle is regulated by the interaction of the nervous system and endocrine system. The hypothalamus releases melatonin, a hormone that promotes sleepiness, in response to darkness. Conversely, exposure to light suppresses melatonin production and promotes wakefulness.