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Neural Control and Coordination NCERT Textbook With Solutions PDF Free Download
Chapter 21: Neural Control and Coordination
As you know, the functions of the organs/organ systems in our body must be coordinated to maintain homeostasis.
Coordination is the process through which two or more organs interact and complement the functions of one another. For example, when we do physical exercises, the energy demand is increased for maintaining an increased muscular activity.
The supply of oxygen is also increased. The increased supply of oxygen necessitates an increase in the rate of respiration, heartbeat, and increased blood flow via blood vessels.
When physical exercise is stopped, the activities of nerves, lungs, heart, and kidneys gradually return to their normal conditions.
Thus, the functions of muscles, lungs, heart, blood vessels, kidneys, and other organs are coordinated while performing physical exercises.
In our body, the neural system and the endocrine system jointly coordinate and integrate all the activities of the organs so that they function in a synchronized fashion.
The neural system provides an organized network of point-to-point connections for quick coordination. The endocrine system provides chemical integration through hormones.
In this chapter, you will learn about the neural system of humans, mechanisms of neural coordination like transmission of nerve impulses, impulse conduction across a synapse, and the physiology of reflex action.
21.1 Neural System
The neural system of all animals is composed of highly specialized cells called neurons that can detect, receive and transmit different kinds of stimuli.
The neural organization is very simple in lower invertebrates. For example, Hydra is composed of a network of neurons.
The neural system is better organized in insects, where a brain is present along with a number of ganglia and neural tissues. The vertebrates have a more developed neural system.
21.2 HUMAN NEURAL SYSTEM
The human neural system is divided into two parts :
(i) the central neural system (CNS)
(ii) the peripheral neural system (PNS)
The CNS includes the brain and the spinal cord and is the site of information processing and control. The PNS comprises all the nerves of the body associated with the CNS (brain and spinal cord). The nerve fibers of the PNS are of two types :
(a) afferent fibers
(b) efferent fibers
The afferent nerve fibers transmit impulses from tissues/organs to the CNS and the efferent fibers transmit regulatory impulses from the CNS to the concerned peripheral tissues/organs.
The PNS is divided into two divisions called somatic neural system and autonomic neural system.
The somatic neural system relays impulses from the CNS to skeletal muscles while the autonomic neural system transmits impulses from the CNS to the involuntary organs and
smooth muscles of the body.
The autonomic neural system is further classified into the sympathetic neural system and parasympathetic neural system.
The visceral nervous system is the part of the peripheral nervous system that comprises the whole complex of nerves, fibers, ganglia, and plexuses by which impulses travel from the central nervous system to the viscera and from the viscera to the central nervous system.
| Author | NCERT |
| Language | English |
| No. of Pages | 16 |
| PDF Size | 4.9 MB |
| Category | Biology |
| Source/Credits | ncert.nic.in |
NCERT Solutions Class 11 Biology Chapter 21 Neural Control and Coordination
2. Compare the following:
(a) Central neural system (CNS) and Peripheral neural system (PNS)
(b) Resting potential and action potential
(c) Choroid and retina
Solution:
The comparison is as shown below:
(a) Central neural system (CNS) and Peripheral neural system (PNS)
| Central neural system (CNS) | Peripheral neural system (PNS) |
| Consists of the spinal cord and the brain | It consists of the spinal nerves and the cranial nerves |
| The spinal column is protected by the vertebral column whereas the brain is protected by the skull | No protective structures |
| No subdivisions | It is divided into the autonomic nervous system and the somatic nervous system |
| Processes information and regulates the responses to impulses. | The nerves of PNS pass impulses to the CNS and responses from the CNS to various structures of the body |
| A Group of neurons is known as nuclei | A Group of neurons is known as ganglia |
(b) Resting potential and action potential
| Resting potential | Action potential |
| When the neuron is at the resting phase, it is the potential difference across the membrane | When the neuron is triggered it is the potential difference across the membrane |
| The exterior side of the neuron is positively charged while the interior side is negatively charged | The exterior side of the neuron is negatively charged and the interior side of the neuron is positively charged |
| Permeability of K+ ions is observed to be more by the plasma membrane of neurons | Permeability of Na+ ions is observed to be more by the plasma membrane of the neurons |
| To maintain the resting potential, the sodium-potassium ATPase pump is activated, sending Na+ ions outside the neuron | It functions in a reverse pattern wherein the sodium-potassium ATPase pump sends Na+ ions to the neuron. |
(c) Choroid and retina
| Choroid | Retina |
| Forms the mid-coat of the eyeball | Forms the inner coat of the eyeball |
| Forms the vascular layer of the eyeball | Forms the neurosensory layer of the eyeball |
| Has no photoreceptor cells | Has two kinds of photoreceptors – rods and cones |
| Prevents the reflection of light in the eye and nourishes the retina | Imparts vision |
NCERT Class 11 Biology Textbook Chapter 21 Neural Control and Coordination With Answer PDF Free Download