Digital Text

DIGITAL TEXT BOOK Submitted by Jomol P. Joseph Department of Natural science Sobha college of Teacher education submitted to Savithakumari S.S Assistant professor , Department of Natural science











CONTENT  Part 1 Chapter 1 Sensations And Responses



NEURONS

Observe the picture children and other organisms have a variety of experiences. What are they? *a child tasting a mango *a snail withdrawing its body in to the shell when it is touched. *……………………………

What are the factors to which children and other organisms respond here ? *taste *touch *……… *……….  The senses that evoke responses in organisms are called stimuli  Hunger and thirst are stimuli formed inside the body aren’t they?

There are specialized cells in the sense organs and other parts of the body to receive stimuli. These cells are known as receptors.

Responses occur when the impulses generated by the receptors on receiving the stimuli reach the brain the nervous system controls and coordinates theses actions. Fig (1)

Analyse the figure (1) and find out the major parts of the nervous system.  *Brain  *………  *………





Fig 1.2

(Fig 1.3) *Analyse the illustration 1.3 and tabulate the main parts of neuron, its characteristics and function in your science dairy

(Fig 1.4)

Axons of most of the neurons are repeatedly encircled by myelin, a membrane containing lipid. This is called myelin sheath  Analyse the figure (1.4),(1.5)and significance of myelin sheath and prepare a note on the basis of the indicators given.

(Fig 1.5)

The myelin sheath is a greatly extended and modified plasma membrane wrapped around the nerve axon in a spiral fashion [1]. The myelin membranes originate from and are a part of the Schwann cells in the peripheral nervous system (PNS) and the oligodendroglial cells in the central nervous system (CNS)

Myelin sheath has a shiny white in colour , the part of the brain and spinal cord where myelinated and the spinal cord where myelinated nerve cells are present in abundance called white matter and the part where the non-myelinated nerves are presesent is called grey matter INDICATORS *Formation of myelin sheath *Grey matter, white matter *Functions of myelin sheath

Importance of myelin sheath  Myelin is an insulating layer, or sheath that forms around nerves, including those in the brain and spinal cord. It is made up of protein and fatty substances. This myelin sheath allows electrical impulses to transmit quickly and efficiently along the nerve cells. If myelin is damaged, these impulses slow down.

Myelin sheath is important in the structure of neuron is’nt it? What is your opinion discuss and write in your science dairy.

OLIGODENDROCYTES AND SCHWANN CELLS Oligodendrocytes and Schwann cells are engaged in myelin production, maintenance and repairing respectively in the central nervous system (CNS) and the peripheral nervous system (PNS).

synapse impulses generated in the receptor cells reach the brain. The brain analysis it and gives direction for proper response. To make this possible, how does this become possible? Analyse the figure( 1.6) and prepare a note based on indicators. Fig (1.6)

 The space between the end of a nerve cell and another cell. Nerve impulses are usually carried to the neighboring cell by chemicals called neurotransmitters, which are released by the nerve cell and are taken up by another cell on the other side of the synapse. Indictors *Structure of synapse *Transmission of impulses through synapse

DIFFERENT TYPES OF NEURON Fig(1.8) Analyse the figure (1.8) ,(1.9) and discuss the types of neuron

Fig (1.9)

Nerves  Do you know that nerves are group of axons or nerve fibers. They are covered by connective tissue(1.10)  Nerves are classified into three on the basis of their functions. Analyse fig (1.10)and prepare the notes in your science dairy.

(Fig 1.10)

 Sensory nerves carry signals to your brain to help you touch, taste, smell and see. Motor nerves carry signals to your muscles or glands to help you move and function.  Motor nerves are the nerves responsible for all voluntary skeletal and somatic movement such as moving the leg or arm.  A mixed nerve is any nerve that contains both sensory (afferent) and motor (efferent) nerve fibres. All spinal nerves are mixed nerves.

Nervous system The nervous system consists of two parts namely the central nervous system and the peripheral nervous sysytem. The nervous system has two main parts: The central nervous system is made up of the brain and spinal cord. The peripheral nervous system is made up of nerves that branch off from the spinal cord and extend to all parts of the body.

Analyse the flow chart and prepare the notes In your science dairy. (Fig 1.11)

BRAIN (Fig 1.12) The brain is the most complex part of the human body. This three-pound organ is the seat of intelligence, interpreter of the senses, initiator of body movement, and controller of behavior. Lying in its bony shell and washed by protective fluid, the brain is the source of all the qualities that define our humanity.

Cerebrospinal fluid (CSF, shown in blue) is made by tissue that lines the ventricles (hollow spaces) in the brain. It flows in and around the brain and spinal cord to help cushion them from injury and provide nutrients. Indicators *protection of the brain *nourishment of the brain

 Cerebrum: Your cerebrum interprets sights, sounds and touches. It also regulates emotions, reasoning and learning. ...  Cerebellum: Your cerebellum maintains your balance, posture, coordination and fine motor skills. ...  Your thalamus is your body's information relay station. All information from your body's senses (except smell) must be processed through your thalamus before being sent to your brain's cerebral cortex for interpretation. Your thalamus also plays a role in sleep, wakefulness, consciousness, learning and memory.

 Your hypothalamus, a structure deep in your brain, acts as your body's smart control coordinating center. Its main function is to keep your body in a stable state called homeostasis. It does its job by directly influencing your autonomic nervous system or by managing hormones.  Medulla oblongata is the bottom-most part of your brain. Its location means it's where your brain and spinal cord connect, making it a key conduit for nerve signals to and from your body. It also helps control vital processes like your heartbeat, breathing and blood pressure.

Aren’t you convinced of the importance of the brain? Discuss the necessity of wearing helmets while riding two wheelers.

SPINAL CHORD  The spinal cord is a long, tube-like band of tissue. It connects your brain to your lower back. Your spinal cord carries nerve signals from your brain to your body and vice versa. These nerve signals help you feel sensations and move your body.  Any damage to your spinal cord can affect your movement or function. The spinal cord is protected by bones, discs, ligaments, and muscles. The spine is made of 33 bones called vertebrae. The spinal cord passes through a hole in the center (called the spinal canal) of each vertebra. Between the vertebrae there are discs that act as cushions, or shock absorbers for the spine.

 The three primary roles of the spinal cord are to send motor commands from the brain to the body, send sensory information from the body to the brain, and coordinate reflexes. Indicators *Protection of the spinal cord *Functions of spinal cord (Fig.1.13)

Autonomous nervous system  There are many instances in your life when you felt sudden fear or sadness. Write down some of those experiences.  ……..  ……..  …….. Activities that takes place beyond the conscious level are controlled by the autonomous nervous sysytem.

The sympathetic and parasympathetic system together form the autonomous nervous sysytem. Analyse the fig (1.14)and write the notes in your science dairy.

Follow up activity construct a model of the human brain using suitable scrap materials and exhibit in the class

THANKYOU