THE-NERVOUS-SYSTEM science 10 powerpoint

THE-NERVOUS-SYSTEM science 10 powerpoint

1. The nervous system

2. How does the nervous system coordinates and regulate feedback mechanisms to maintain homeostasis? Our nervous system helps us receive information about what is happening inside and around us and directs us to respond appropriately to a given situation. This concrete example below shows that the body has the ability to control and coordinate the activities of all its parts. This characteristics is due to the presence of two organ systems, the nervous and endocrine systems. The nervous system enables the body to gather information from the outside environment and respond quickly. The endocrine system on the other hand, although slow in terms of response, produces longer-lasting effects due to the hormones. These systems interact to coordinate the body’s activities.

3. Functions of the nervous system The nervous system controls and interprets all the activities that happen within the body. It enables us to move, think, laugh, feel pain, or enjoy the taste of food. It makes the body respond quickly to changes in the environment by accomplishing four basic functions.

4. Neuron: The message-carrying unit of the nervous system The nervous system is constantly alive with activity. It buzzes with messages that run to and from all parts of the body. Every second, hundreds of these messages are carried by strings of special cells called neurons or nerve cells. Neurons are the basic functional units of structure and function of the nervous system. They carry information through the nervous system in the form of nerve impulses. Neurons are unique because, unlike most other cells in the body, they do not reproduce. Once damaged, neurons cannot be replaced. This is not a cause for concern, however, because the neurons we are born with are more than enough for a lifetime.

5. PARTS OF A Neuron The cell body contains the nucleus (a large dark structure), which controls all the activities of the cell. Think of the cell body as switchboard of the messages-carrying neuron. Running into this switchboard are one or more tiny, branching, threadlike structures called dendrites , which receive and carry information toward the cell body. A long, tail-like fiber that extends from the cell body, called axon , carries messages away from the cell body. The myelin sheath covers the axon, which speeds up the travel of the nerve impulses. Each neuron has only one axon, but it can have many dendrites. The axon splits into many featherlike fibers, called axon terminals (ends), at the far ends. Axon terminals pass on messages to the dendrites of other neurons.

6. types OF Neurons Sensory Neurons are also called afferent neurons because their function is to receive initial stimuli from the sense organs, where most receptors are located. The sensory neuron’s goal is to transmit the nerve impulses to the spinal cord and ultimately, to the brain so an action can be taken. Interneurons are called connector neurons or association neurons . They read impulses received from sensory neurons. When an interneuron receives an impulse from a sensory neuron, the interneuron determines what response should be generated. If a response is required, the interneuron passes the impulse on to the motor neurons. Motor neurons are also called efferent neurons , transmit impulses from the brain and spinal cord to the effector cells, which may be those of muscles, organs or glands. When motor neurons receive a signal from the interneuron, they stimulate the effector cells to generate the reaction for the stimulus.

7. NERVE IMPULSES A nerve impulse is a wave of chemical and electrical change that is conducted along the membrane of a neuron. It travels from sensory neuron to interneuron to motor neuron. When a nerve impulse travels along a neuron or from one neuron to another, it does so in the form of electrical and chemical signals. The nerve impulse enters the neuron through the dendrites and travels along the length of the axon. The way in which a nerve impulse travels from one neuron to another is a bit complex. Neurons do not touch each other, neither do they touch effector organs. Instead, there is a tiny gap called a synapse between two adjacent neurons, and also between neurons and effectors.

8. NERVE IMPULSES A nerve impulse is “ferried” across the synapse by a chemical signal. This happens when an impulse reaches the end of the axon, sending information across the synapse in the form of chemical messengers called neurotransmitters , which are stored in small sacs. When a nerve impulse reaches the axon terminal, the sacs fuse with the axon’s membrane and releases its neurotransmitter molecules into the synapse. The molecules then diffuse across the synapse and bind to receptors on the next neuron or effector cell.

9. DIVISIONS OF THE NERVOUS SYSTEM

10. DIVISIONS OF THE NERVOUS SYSTEM The nervous system is divided into two main parts: the central nervous system and the peripheral nervous system. The two divisions of the nervous system working together as a team that monitors, coordinates, and controls the activities of the entire body.

11. CENTRAL NERVOUS SYSTEM

12. CENTRAL NERVOUS SYSTEM The central nervous system is the command center for the entire body; it processes information and sends instructions to other parts of the body. All the information gathered by sensory receptors is delivered to the central nervous system in the form of nerve impulses. The CNS processes the information and responds by sending nerve impulses to the motor nerves of the PNS.

13. CENTRAL NERVOUS SYSTEM Interpreting the information that pours in from all parts of the body and issuing the appropriate commands to these very same parts are the responsibility of the two parts of the central nervous system: the brain and the spinal cord. The brain is the main control center of the central nervous system. It transmits and receive messages through the spinal cord. The spinal cord provides the link between the brain and the rest of the body.

14. THE BRAIN Being a very important and delicate organ, the brain is well protected and encased in a bone called skull . The brain is bathed with a watery fluid that cushions it against sudden impact, such as when one bumps the head or experience a nasty fall. It appears gray because of the presence of the cell bodies of approximately 100 billion neurons . Despite the presence of billions of neurons, the mass of the brain is about 1.4 kilograms only.

15. THE BRAIN The brain is divided into three main parts: the cerebrum , cerebellum and brain stem.

16. THE CEREBRUM It makes up 85% of the human brain. The surface of the cerebrum is called the cerebral cortex, which is lined with the deep, wrinkled grooves that increase the surface area so that more thinking activities can occur. This is the area where learning, intelligence and judgment occur. Aside from the this enormous task, the cerebral cortex also controls all the voluntary activities in the body.

17. THE CEREBRUM The CEREBRAL HEMISPHERES

18. THE CEREBELLUM The cerebellum is the second largest part of the brain and is located behind the brain stem. It coordinates the actions of the muscles and maintains balance so that the body can move smoothly, steadily and effectively. Balance, equilibrium and posture are made possible by the cerebellum.

19. THE BRAIN STEM The brain stem connects the spinal cord to the rest of the brain. It coordinates many survival functions of the body such as breathing, heart rate, sleep and wakefulness. Three distinct regions make up the brain stem: the midbrain , the pons and the medulla oblongata .

20. THE BRAIN STEM The medulla oblongata controls involuntary actions such as heartbeat, breathing and blood pressure. The midbrain processes visual and auditory reflexes. The pons helps control respiratory functions.

21. THE BRAIN STEM The thalamus serves as a relay station by directing incoming messages from the spinal cord to the appropriate parts of the brain. The hypothalamus monitors internal conditions such as water content and temperature. It acts as the link between the endocrine and nervous systems.

22. THE SPINAL CORD The spinal cord is a tube-like organ of neurons and blood vessels. Located inside the backbone, or spine, the spinal cord is about 1.8 cm wide , nearly the same size as a garden hose. Aside from the bones of the spine, three membranes called meninges , cushions of fluid, protect the spinal cord.

23. THE SPINAL CORD The spinal cord relays nerve impulses to and from the brain. Impulses from the peripheral nervous system are conducted to the spinal cord, which then brings the message to the brain. The brain, in turn, sends impulses down the spinal cord to the motor nerves of the peripheral nervous system.

24. THE SPINAL CORD The neurons, in a pathway called the reflex arc , carry the nerve impulses for an automatic response. A reflex that does not involve the brain is called a spinal reflex , which enables us to respond quickly because we do not have to think about it.

25. THE SPINAL CORD The reflex arc when we remove our hand from a hot object.

26. PERIPHERAL NERVOUS SYSTEM

27. PERIPHERAL NERVOUS SYSTEM The Peripheral Nervous System is the link between the central nervous system (brain and spinal cord) to the rest of the body. It is made up of a network of bundled ropelike structures called nerves , which extend or branch out from the central nervous system to the different organs of the body. The PNS gathers and delivers information to and from the central nervous system.

28. PERIPHERAL NERVOUS SYSTEM The Peripheral Nervous System consists of 43 pairs of nerves that arise from the brain and spinal cord, leading to organs throughout the body. Many of the nerves in the PNS are under the direct control of the conscious mind. The PNS is divided into two parts: the Somatic Nervous System and the Autonomic Nervous System.

29. SOMATIC NERVOUS SYSTEM The part of the PNS that stimulates skeletal muscles under our conscious control is called the somatic nervous system. Its main parts are the cranial nerves and the spinal nerves .

30. AUTONOMIC NERVOUS SYSTEM The autonomic nervous system controls body activities that are involuntary; that is, those that happen automatically, without our thinking about them. It directs motor nerve fibers in smooth muscles, cardiac muscles and the glands. Contractions of the heart muscle and movement of smooth muscles surrounding the small intestine are activities under the control of autonomic nervous system.

31. DIVISIONS OF THE AUTONOMIC NERVOUS SYSTEM The autonomic nervous system can be further divided into two groups that have opposite effects on the organs they control. These two divisions- the parasympathetic and the sympathetic – maintain stability in the body by working against each other to keep body activities in balance.

32. DIVISIONS OF THE AUTONOMIC NERVOUS SYSTEM The parasympathetic division is most active under normal conditions; it keeps the body functioning even when the person is not active. It controls the “fight-or-flight” response during a stressful situation like the nervousness we experience when speaking before an audience or taking a surprise quiz.

33. DIVISIONS OF THE AUTONOMIC NERVOUS SYSTEM The sympathetic division increases blood pressure, heart rate, and breathing rate. Such an increase may be necessary if extra energy and strength are needed to deal with the stressful situation. But when the situation is over, the parasympathetic nerves bring the blood pressure, breathing rate and heartbeat back to normal.