CH-14+PART+1.pdf CH-14+PART+1.pdf CH-14+PART+1.pdf
- 1. CHAPTER 14 Dr. Mona Elkhatieb
- 3. • How can his leg muscles know when to stretch and when to relax to produce those movements? Brain is sending them information • How can the brain know that now it is time to jump, to bend the left leg….? By the information collected from the player’s eyes, ears (sound and balance) and muscle stretch receptors “sensory information”
- 4. Coordination • Coordination is the way all the organs and systems of the body are made to work efficiently together. • If, for example, the leg muscles are being used for running: What do they need? they will need extra supplies of glucose and oxygen. Who can help them meet this demand? the lungs and heart The lungs breathe faster and deeper to obtain the extra oxygen & the heart pumps more rapidly to get the oxygen and glucose to the muscles more quickly. Who told the heart and lungs to do that? The brain detects changes in the oxygen and carbon dioxide content of the blood and sends nervous impulses to the diaphragm, intercostal muscles and heart. In this example, the nervous system coordinates the systems. It works by sending electrical impulses along nerves.
- 5. OBJECTIVES
- 7. Coordination • Coordination is the way all the organs and systems of the body are made to work efficiently together. • Coordination involves 2 major body systems: - Nervous system - Endocrine system • Nervous system works by sending electrical impulses along nerves. • A nerve impulse is an electrical signal that passes along nerve cells called neurons.
- 8. Human nervous system • The human nervous system consists of: 1) the central nervous system (CNS) – the brain and spinal cord 2)the peripheral nervous system (PNS) – nerve cells that carry information to or from the CNS (connect the body to the CNS).
- 10. Human nervous system • Nerves carry electrical impulses from the central nervous system to all parts of the body, making muscles contract or stimulating glands to produce enzymes or hormones. • Electrical impulses are electrical signals that pass along nerve cells (neurones). • Glands and muscles are called effectors because they act when they receive nerve impulses or hormones. • Examples : ✓The biceps muscle is an effector that flexes the arm. ✓The salivary gland is an effector that secretes saliva when it receives a nerve impulse from the brain.
- 11. • The nerves also carry impulses back to the central nervous system from receptors in the sense organs of the body. These impulses from the eyes, ears, skin, etc. make us aware of changes in our surroundings or in ourselves. • Nerve impulses from the sense organs to the central nervous system are called sensory impulses. • Those from the central nervous system to the effectors, resulting in a response, are called motor impulses.
- 12. The central nervous system & are made up of nerve cells called neurones. the peripheral nerves
- 13. THE THREE TYPES OF NEURONES: (Sensory neurones - Relay neurones - Motor neurones) A B C
- 15. THE THREE TYPES OF NEURONES
- 16. - Motor neurones (also called effector neurones) carry impulses from the central nervous system to muscles and glands. - Sensory neurones carry impulses from the sense organs to the central nervous system. - Relay neurones (also called connector or multipolar neurones) are neither sensory nor motor. They make connections to other neuron inside the central nervous system.
- 17. Nerve cells (neurones) • They are adapted to carry electrical impulses from one place to another. • Each neurone consists of: 1) a cell body consisting of a nucleus surrounded by cytoplasm. 2) The axon (nerve fibre) is a long filament of cytoplasm, surrounded by an insulating sheath, runs from the cell body of the neurone. It is an extended cytoplasmic thread like structure along which electrical impulses travel. 3) Axons of sensory & motor neurons are coated by a layer of myelin called myelin sheath, this is an electrically insulating layer which is essential for the proper functioning of the nervous system. 4) Dendrites are fibres, which branch from the cell body to make contact with other neurones. 5) In motor neurones, motor end plate passes the electrical impulses from the neurone to the muscle fibres.
- 18. Importance of myelin sheath
- 20. Identify the 3 types of neurones
- 21. The electrical impulse always travels in this route:
- 22. Synapses Junctions where neurones connect with each other are called synapses.
- 23. What are nerves? • The cell bodies of the neurones are mostly found in the brain or in the spinal cord. • The nerve fibres run in the nerves. • A nerve is easy to see. It is white, tough and stringy, and consists of hundreds of microscopic nerve fibres bundled together. Most nerves will contain a mixture of sensory and motor fibres, so a nerve can carry many different impulses. These impulses will travel in one direction in sensory fibres and in the opposite direction in motor fibres. • Some of the nerve fibres are very long (up to 1 m). The cell bodies of the nerve fibres are found in the spinal cord. Those fibres connected to the foot run inside the nerves continuously to the skin of the toes or the muscles of the foot.
- 25. Synapses • A synapse is a junction between two nerve cells (neurons), consisting of a minute gap across which impulses pass by diffusion of a neurotransmitter
- 26. The small gap between the two neurons is called the synaptic cleft. The ends of the two neurons on either side of the cleft plus the cleft itself is called the synapse.
- 27. Transmission of impulses across synapses • Vesicles (containing neurotransmitter) move and fuse with the cell membrane . • Neurotransmitters are released and diffuse across synaptic cleft (synaptic gap). • Neurotransmitter binds to protein receptor on cell surface of the other neuron, resulting in an impulse in the next neuron. • Neurotransmitters are then recycled or destroyed to avoid continuous stimulation.
- 28. How do impulses travel only in one direction? • Synapses control the direction of impulses because neurotransmitter molecules are only synthesised on one side of the synapse and receptor proteins are only present on the other side. At a synapse, a branch at the end of one fibre is in close contact with the cell body or dendrite of another neurone
- 30. OBJECTIVES
- 31. Can you think of examples of reflex actions?
- 32. Reflex actions • A reflex action is an automatic response to a stimulus (A stimulus is a change in the external or internal environment of an organism). • Examples: When a particle of dust touches the cornea of the eye → you will blink; you cannot stop yourself blinking. A particle of food touching the lining of the windpipe → will set off a coughing reflex that you cannot stop. When a bright light shines in the eye → the pupil contracts. You cannot stop this reflex and you are not even aware that it is happening. • All of these reflex actions are automatic; you do not need to think or decide. • The nervous pathway for reflexes like these is called a reflex arc.
- 33. • Reflex actions are rapid and happen without us thinking. For example, you would pull your hand away from a hot flame without thinking about it. • Reflex actions are useful because the message gets from the receptor to the effector very quickly and are said to be involuntary actions. • Involuntary actions start at the sense organ heading to the effector. You don’t waste time in thinking about what to do.
- 34. Reflex arc • A reflex arc describes the pathway of an electrical impulse in response to a stimulus
- 35. Reflex arc • Sensory neurons detect stimuli and transmit signals to the brain and spinal cord, which are both made of relay neurons.
- 36. • Relay neurons receive signals from sensory and relay them within the brain and spinal cord. • They process signals and pass signals to motor neurons.
- 37. • Motor neurons pass messages from the nervous system to other tissues in the body such as muscles.
- 38. Reflex arc (Sensory neurons - Relay neurons - Motor neurons) A B C
- 41. Knee jerk reflex
- 42. Example
- 43. On the picture below, the stimulus is a drawing-pin sticking in the finger. The response is the withdrawal of the arm due to contraction of the biceps.
- 44. Reflexes of the eye involve the brain not the spinal cord
- 45. HW