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class 10 coordination and control full chapter reviews | human nervous system  class 10th

 Chapter 12

COORDINATION AND CONTROL

We know that, various physiological actions and reactions are happening in our body. These activities need to be  coordinate. This chapter deals with the centrel system that are responsible for coordination.

coordination and control

Coordination means imtergatting  Different parts of the body and to responding to stimuli. Coordination helps to keep harmony with the environment.


12.1-Types of coordination


coordination occurs in all multicellular organisms. There are two types of coordination i.e. chemical coordination and nervous coordination In animals, endocrine system produces hormones for chemical coordination while nervous system produces electrical signals for nervous coordination. Plants show only chemical coordination but they do not have endocrine system. Specialized cells in plant body produce hormones for chemical coordination.



Coordination Action


A coordinated action has five components;


1-Stimulus (Plural: stimuli)


Any factor in  external or internal environment, which can initiate a response in the body, is called a stimulus.Examples of heat, light, and sound stimuli. Whenever the body receives a stimulus, it responds according to needs. Other examples of stimuli are cold, pressure, microbial infections, etc.


2-Receptor


The organ, tissue or cell which receives stimuli is called the receptor. For example, ears are the receptors for the stimulus of sound, eyes are the receptors for light, and the nose contains receptors for chemicals in air. After receiving the stimuli, receptors send the messages to coordinators.


3-Coordinator


la coordinator receives messages from receptors and then sends messages to particular organs for proper action.In chemical coordination, endocrine glands are the coordinators. They receive information in the form of chemicals and send messages by secreting hormones in blood.


4-Effector


The messages of coordinators are received by special parts of the body called effectors.On receiving the coordinator's message, the effectors do actions according to their specialization. In neural coordination, muscles and glands are  effectors. During  chemical Synthesis Vrious  of the body act as influencers.


5-Response


A response is the action performed by effectors, on receiving the message from coordinator. For example, pulling our hand away from something very hot and the movement of sunflowers towards light are responses. In nervous coordination, responses are quick but short-living. In chemical coordination responses are usually slow but long-lasting.


12.2-Human Nervous System


The nervous system of humans consists of two major components i.e. (CNS) And (PNS) Central nervous system and peripheral nervous system . The CNS consists of coordinators i.e. brain and spinal cord. The PNS consists of nerves that arise from brain and spinal cord and spread in different parts of body.


All these components are made of neurons and supporting cells.


Nerve cell or Neuron


Neurons are the units of nervous system. These are the cells that are specialized to conduct messages in the form of nerve impulses among various body parts. A nerve impulse is a wave of electrochemical changes that travels through neurons.


Structure of Neuron


A neuron consists of three major parts i.e. cell body, dendrites and axon.


The cell body contains the nucleus, other organelles and most of the cytoplasm. Small branches which project from the cell body are called dendrites. They transmit nerve impulses towards cell body. The axon is a long branch from cell body. Its terminal end is further branched. 

Neurons are supported by special cells, called neuroglia.Schwann cells is a type of Neuroglia. These cells produce myelin sheaths over the axons of some neurons. Myelin sheath is an insulating covering.


There are small gaps in the myelin sheath. These gaps are called nodes of Ranvier. In myelinated neurons, nerve impulses 'jump' from node to node. This speed up the Nervous System.


Types of Neuron


There are three types of neuron, on the basis of their functions.


1:- Sensory neurons transmit nerve impulses from receptors to the CNS.


2. Inter-neurons are present in brain and spinal cord. They receive nerve impulses from sensory neurons and transmit them to motor neurons.


3. Motor neurons transmit nerve impulses from inter-neurons to effectors (muscle or glands).


Nerve


A nerve is collection of axons that are enveloped by a covering. Nerves arise from brain and spinal cord and make the PNS. There are three types of nerves, on the basis of axons present in them. There are only a sensual Neurons in the sensual nerves.Motor nerves contain the axons of motor neurons only Mixed nerves contain the axons of sensory and motor neurons.


Divisions of the Nervous System


1-Central Nervous System


The Central Nervous system contains of backbone and the brain.


A-Brain 


All of the animals are in control of brain activity.

The structure of the brain is conducive to this function. Brain is present inside cranium (part of skull). 


Inside cranium, brain is covered by three layers of membranes, collectively called meninges.Their job is to protect the brain from harmful substances. Brain contains fluid filled ventricles.


 The ventricles of brain are continuous with the central canal of spinal cord.Fluid within ventricles and central canal is called cerebrospinal fluid (CSF). three Parts of Brain :

  1. forebrain, 

  2. midbrain

  3. hindbrain.



1- Forebrain


It is the largest area of brain. It is most highly developed in humans.


1:- Cerebrum is the largest part of forebrain.This  thinking controls emoticons and adornment. A longitudinal fissure divides the cerebrum into right and left cerebral hemispheres.The upper layer of both hemispheres is highly folded and is called cerebral cortex. It is made of grey matter (which has cell bodies and non myelinated axons). The material beneath cortex is white matter (containing myelinated axons).


They  hemisphere is divided into four parts: the frontal, parietal, temporal, and occipital lobes.The frontal lobe controls problem solving, judgment, speaking, and movements. The parietal lobe controls language and touch! The temporal lobe controls memory, learning, feelings, and hearing.The occipital lobe controls vision and color perception.


2:- Thalamus is a structure wrapped by the cerebrum. It conveys messages coming from receptors to the cerebrum.It also modifies messages (except from nose) before conveying them to the cerebrúm. The Thalamus is also involved in The perception and awareness of pain.


3:- The Hypothalamus is above the midbrain and below the thalamus. In humans, it is about the size of an almond) (It controls body temperature, hunger, thirst, sleep, and emotional states it also controls the secretions of the major endocrine gland i.e. pituitary gland.


2-Midbrain


The midbrain is located between forebrain and hindbrain. So, it is a bridge between these two parts and conveys messages between them. It also enables the body to make adjustments to movements. It is also responsible for sleep/wake, alertness and temperature control.



3- Hindbrain


Hindbrain controls all automatic body functions. It consists of three major parts. 


  1.  Cerebellum also has highly folded surface. It coordinates muscle movements.

  2. Pons is present on top of the medulla. It makes connections between the spinal cord and cerebellum, and between cerebrum and cerebellum. It also controls alertness, sleep, and wakefulness.

  3. Is is located at the top of the backbone.It transmits messages between spinal cord and the parts of brain. It also controls autonomic functions such as heartbeat, heart rate, breathing and blood pressure. It also controls reflexes such as vomiting, coughing, sneezing etc.


B-Spinal Cord


It is a tubular bundle of nerves that starts from the brain and extends to lower back. It is located in vertebral column and is also covered by meninges. Spinal cord transmits impulses from body parts to brain and from brain to body parts. It also acts as a coordinator for some simple reflexes.


Structure of Spinal cord: The outer region of spinal cord is made of white matter.The central region is butterfly shaped that surrounds the central canal.It is made of grey matter.There are thirty one pairs of spinal nerves that arise from the spinal cord.All spinal nerves are "mixed" nerves because each contains axons of both sensory and motor neurons.






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