Unit 2 nervous system
- 1. 1 University of Hail College of Nursing Physiology PHYL281 Dr Jupiter V. Cajigal Assistant Professor, University of Hail UNIT 2 The Nervous System
- 2. Objectives : At the end of this lecture, the student will be able to: Describe the functions of the nervous system Describe the parts of a neuron cell and identify how they transmit electrochemical impulses. Compare and contrast the central and peripheral nervous systems Identify and explain different areas of the brain and their functions. Explain how the nervous system passes information between the external environment and the many parts of the body.
- 3. FOUR PRIMARY FUNCTIONS OF NERVOUS SYSTEM • Sensing the world • Vision, Hearing, Smell, Taste, Touch • Transmitting information • Processing information • Producing a response
- 6. NEURONS • a specialized cell transmitting nerve impulses; a nerve cell.
- 7. NEURONS Glial cells surround neurons and provide support for and insulation between them. Glial cells are the most abundant cell types in the central nervous system. Types of glial cells include oligodendrocytes, astrocytes, ependymal cells, Schwann cells, microglia, and satellite cells.
- 8. Parts of nerve cell & Function of each part: • Dendrites : receive chemical signals from neighboring cells. • Dendrites are the structures on the neuron that receive electrical messages. These messages come in two basic forms: excitatory and inhibitory.
- 9. Parts of nerve cell & Function of each part: • Cell Body: contains the nucleus & organelles • It also contains the cell's DNA, which is essentially the neuron's blueprint. The nucleus is another organelle that serves a vital purpose to the functioning of the neuron. It nucleolus produces ribosomes, which are essential to protein production.
- 10. Parts of nerve cell & Function of each part: Axon: long extension that carries electrical messages away from the body to the terminal axons. An axon, is a long, slender projection of a nerve cell, or neuron, that typically conducts electrical impulses away from the neuron's cell body. Myelinated axons are known as nerve fibers. The function of the axon is to transmit information to different neurons, muscles and glands.
- 11. Parts of nerve cell & Function of each part: the somewhat enlarged, often club-shaped endings by which axons make synaptic contacts with other nerve cells or with effector cells (muscle or gland cells). Axon terminals contain neurotransmitters of various kinds, sometimes more than one.
- 12. Parts of nerve cell & Function of each part: main purpose of myelin is to increase the speed at which electrical impulses propagate along the myelinated fiber. In unmyelinated fibers, electrical impulses (action potentials) travel as continuous waves, but, in myelinated fibers, they "hop" or propagate by saltatory conduction.
- 13. Parts of a neuron Nerve Cell
- 14. Types of Neurons 3 main types of neurons: Sensory neuron = detect stimuli Interneurons = relay sensory signals to brain then return message back to motor neurons. Motor neuron = pass message from brain to rest of body for muscle response. This coordinated pathway is known as the REFLEX ARC
- 16. Reflex Arc “ what happens when you step on a nail”? Reflexes are automatic The Stimulus (nail ) is received by the sensory neurons in the foot This info travels to the spine, where the interneuron is triggered The interneuron transmits signal to brain (through the spinal cord)and carries message back and stimulates the motor neuron, to move the foot
- 17. Nerve Impulse A progressive wave of electric and chemical activity along a nerve fiber that stimulates or inhibits the action of a muscle, gland, or other nerve cell
- 18. Nervous System(Central Nervous System) • the part of the nervous system which in vertebrates consists of the brain and spinal cord, to which sensory impulses are transmitted and from which motor impulses pass out, and which coordinates the activity of the entire nervous system — compare peripheral nervous system.
- 19. NervousSystem(PeripheralNervousSystem) • The nerves in the PNS connect the central nervous system (CNS) to sensory organs, such as the eye and ear, and to other organs of the body, muscles, blood vessels, and glands.
- 22. Nervous System Has two main divisions 1. Central Nervous System ( CNS) brain, spinal cord 2. Peripheral Nervous System ( PNS) all other nerves
- 23. The Nervous system is: • A physically connected network of cells, tissues and organs that allow us to communicate with and react to the environment and perform life activities.
- 24. 2 main divisions: Central Nervous System (CNS) • Receives, interprets and sends signals to peripheral nervous system (PNS). • Has 2 main parts: • Brain – main control center • Spinal Cord – connects and relays nerve impulses to the brain
- 25. Peripheral Nervous System (PNS) Connects CNS to all organ systems Made up of: Sensory Neurons: detect stimuli Motor Neurons: carry signal to stimulate response 2 major subsystems: Somatic – voluntary movement (balance, movement) Autonomic – involuntary movement (digestion, fight or flight)
- 29. The Brain
- 30. Cerebrum
- 31. • Large front part of the brain FUNCTIONS: – Voluntary activity – Memory – Language – Receives and responds to sensory signals – Controls motor functions
- 32. Cerebellum
- 33. THE CORTEX
- 34. Top layer of the brain Stores: experiences and/or learning Frontal- behavior & emotion Temporal- memory & emotion, speech and hearing Occipital- vision Parietal- Sensory info concerning touch
- 35. Brain Stem BRAIN STEM swallowing, coughing, sneezing, and vomiting Includes the Medulla Oblongata
- 36. Brain Stem PONS Breathing Heart rate Internal Organs
- 37. “controls: emotions and memories” Damage to these areas can lead to amnesia or emotional disturbances
- 38. The Autonomic Nervous System • Divided into: I-Sympathetic: Originate from: The lateral horn cells of all thoracic & upper 3 lumbar Segments of the spinal cord . II – Parathempathetic Nervous system(cranio-sacral Outflow): The cranial outflow: The sacral outflow: - 2 , 3 & 4 sacral spinal nerves . Oculomotor nerve (3). Facial (7) Glossopharyngeal (9) Vagus (10)
- 40. Innervation of Body Organs -In the body there are organs which are innervated by both sympathetic and parasympathetic systems: - Heart - Digestive tract - Pupil of the eye - Salivary glands There are organs with only sympathetic innervation: Adrenal medulla Sweat glands Most blood vessels
- 41. Functions of 1- Sympathetic system: Excitation of sympathetic centers will cause: - Increase in heart rate. - Increase in blood pressure, - Blood glucose is elevated - Increase in the rate of metabolism
- 42. Function of Parasympathetic system 2-parasympathetic system: usually has opposite effects to those of sympathetic system. Excitation of parasympathetic causes: Decrease in heart rate, Increase blood flow to the digestive system, Increase activity of the digestive system.
- 44. Nerves Function : A nerve is a fiber that connects the brain and spinal cord with various parts of the body. Nerves conduct impulses from the brain/spinal cord to these receptor organs as well as conducting impulses from the receptor organs back to the brain/spinal cord.
- 45. SYMPATHETIC NERVOUS SYSTEM • Cause vasoconstriction by activation of a-adrenergic receptors on vascular smooth muscle by norepinephrine. • Vasoconstriction of arterioles increased vascular resistance and redistribution of blood flow • Vasoconstriction of veins increased circulating blood volume, increased venous return leads to increased ventricular filling and stroke volume. • Increase in the activity of the heart (heart rate and contractility) • There are also sympathetic vasodilator fibers which release epinephrine acting on β-adrenergic receptors.
- 46. PARASYMPATHETIC SYSTEM • 75% of all parasympathetic nerve fibers are in the vagus nerves (cranial nerve X) • Pass to the entire thoracic and abdominal regions of the body , including the heart. • Preganglionic nerves pass all the way to the organ. • Postganglionic nerves are very short and located entirely in the wall of the organ. • Play a role in the regulation of circulation. • Mainly control heart rate • Stimulation of vagus nerves results in a decrease in heart rate and contractility