3 The nervous system Need for communication Communication is required for coordinationGather informationProcess informationRespond accordingly
4 The nervous systemNervous system has two parts (central and peripheral)Central nervous system (CNS) – brain and spinal cordPeripheral nervous system (PNS) – other parts of the nervous systemThe CNS processes and responds to all messages coming from the peripheral nervous systemThe PNS connects all parts of the body to the CNSIt uses specialized structures called nerves to carry information between body and CNS
9 Peripheral nervous system Sensory neurons – gather informationSpecial nerve endings called as receptorsMotor neurons – send impulses from brain and spinal cord to other parts of the body e.g. muscle, sweat glands etc.
10 Peripheral nervous system PNS has two types of motor neurons – somatic and autonomicSomatic - under conscious control (voluntary movements such as writing, talking, smiling, or jumping)Autonomic - controls body functions that you do not think about, such as digestion and heart rateMaintain body’s functions in balanceDepending on the situation, the autonomic nervous system can speed up or slow down these functionsThe autonomic nervous system has two divisions: the sympathetic nervous system and the parasympathetic nervous system
12 Central nervous system The central nervous system receives information from the sensory neuronsThen it responds by sending messages to the body through motor neurons in the PNSMade up of brain and spinal cord
13 Brain Largest organ in the nervous system Different parts perform different functionsCerebrumLargest part of the brainControls voluntary movementsIt also allows to sense touch, light, sound, odors, taste, pain, heat etc.The cerebrum is made up of two halves, called hemispheres.The left hemisphere directs the right side of the body, and the right hemisphere directs the left side of the body
15 BrainCerebellumThe second largest part of your brain and lies beneath the back of the cerebrumThe cerebellum processes sensory information from the body, such as from skeletal muscles and jointsThis allows the brain to keep track of the body’s position
16 Brain Medulla The medulla connects brain to the spinal cord Controls involuntary processes such as involuntary breathing, the regulation of blood pressure and heart rateMedulla constantly receives sensory impulses from receptors in blood vessels and uses this information to regulate blood pressureThe medulla also sends impulses to the heart to make the heart beat faster or slower
18 Spinal cord Spinal cord It is made of neurons and bundles of axons that pass impulses to and from the brainThe spinal cord is surrounded by protective bones called vertebraeThe axons in spinal cord allow the brain to communicate with PNSThe axons of sensory neurons in skin and muscles carry impulses to the spinal cordThe spinal cord relays these impulses to the brainThe brain interprets these impulses as pain, temperature, or other sensations and responds to the situation
22 Sense of touchSkin – integumentary system (which includes hair, skin, nails)Protect body from damageGlands and receptorsReflexSkin and feedback mechanism(Body temperature)
23 Sense of sight Eyes detect light and brain forms visual images Cornea and retinaMechanism of vision
24 Sense of sightReacting to light – role if irisFocusing light
25 Sense of hearing Sound and vibrations Ear – outer, middle and inner Outer earPinna and ear canalMiddle earTympanic membrane or ear drumBones (hammer, anvil and stirrup)Inner earCochlea and auditory nerveFluid and balancing body
27 Sense of tasteTaste is the sense that detects chemicals and to distinguish flavorsThe tongue is covered with tiny bumps called papillae which contain taste budsTaste buds contain clusters of taste cells, the receptors for taste . They respond to dissolved-food moleculesTaste cells react to five basic tastes: sweetness (sugar), sourness (lemon), saltiness (salt), savoriness (meats and cheeses), and bitterness (some medicines)When the brain combines information from all of the taste buds, you taste a “combination” flavor
29 Sense of smellThe receptors for smell are located on olfactory cells in the upper part of your nasal cavityAn olfactory cell is a nerve cell that responds to chemical molecules in the air. You smell something when the receptors react to molecules that have been inhaledThe molecules dissolve in the moist lining of the nasal cavity and trigger an impulseOlfactory cells send those impulses to the brain, which interprets the impulses as odorsTaste buds and olfactory cells both detect dissolved moleculesThe brain combines information from both senses to give sensations of flavor.