 Need for communication  Communication is required for coordination  Gather information  Process information  Respond accordingly

 Nervous system has two parts (central and peripheral)  Central nervous system (CNS) – brain and spinal cord  Peripheral nervous system (PNS) – other parts of the nervous system  The CNS processes and responds to all messages coming from the peripheral nervous system  The PNS connects all parts of the body to the CNS  It uses specialized structures called nerves to carry information between body and CNS

 Nervous system is made up of cells known as nerve cells or neurons  Cell body, axon and dendrites  Nerve cells are connected to each other

 A nerve is a collection of axons bundled together with blood vessels and connective tissue  Nerves are found everywhere in the PNS  Most nerves have axons of both sensory neurons and motor neurons

 Sensory neurons – gather information  Special nerve endings called as receptors  Motor neurons – send impulses from brain and spinal cord to other parts of the body e.g. muscle, sweat glands etc.

 PNS has two types of motor neurons – somatic and autonomic  Somatic - 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 rate  Maintain body’s functions in balance  Depending on the situation, the autonomic nervous system can speed up or slow down these functions  The autonomic nervous system has two divisions: the sympathetic nervous system and the parasympathetic nervous system

 The central nervous system receives information from the sensory neurons  Then it responds by sending messages to the body through motor neurons in the PNS  Made up of brain and spinal cord

 Largest organ in the nervous system  Different parts perform different functions  Cerebrum  Largest part of the brain  Controls voluntary movements  It 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

 Cerebellum  The second largest part of your brain and lies beneath the back of the cerebrum  The cerebellum processes sensory information from the body, such as from skeletal muscles and joints  This allows the brain to keep track of the body’s position

 Medulla  The medulla connects brain to the spinal cord  Controls involuntary processes such as involuntary breathing, the regulation of blood pressure and heart rate  Medulla constantly receives sensory impulses from receptors in blood vessels and uses this information to regulate blood pressure  The medulla also sends impulses to the heart to make the heart beat faster or slower

 Spinal cord  It is made of neurons and bundles of axons that pass impulses to and from the brain  The spinal cord is surrounded by protective bones called vertebrae  The axons in spinal cord allow the brain to communicate with PNS  The axons of sensory neurons in skin and muscles carry impulses to the spinal cord  The spinal cord relays these impulses to the brain  The brain interprets these impulses as pain, temperature, or other sensations and responds to the situation

 Spinal cord injury  May block information flow to and from the brain  Paralysis

 Skin – integumentary system (which includes hair, skin, nails)  Protect body from damage  Glands and receptors  Reflex  Skin and feedback mechanism (Body temperature)

 Eyes detect light and brain forms visual images  Cornea and retina  Mechanism of vision

 Reacting to light – role if iris  Focusing light

 Sound and vibrations  Ear – outer, middle and inner  Outer ear  Pinna and ear canal  Middle ear  Tympanic membrane or ear drum  Bones (hammer, anvil and stirrup)  Inner ear  Cochlea and auditory nerve  Fluid and balancing body

 Taste is the sense that detects chemicals and to distinguish flavors  The tongue is covered with tiny bumps called papillae which contain taste buds  Taste buds contain clusters of taste cells, the receptors for taste. They respond to dissolved-food molecules  Taste 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

 The receptors for smell are located on olfactory cells in the upper part of your nasal cavity  An 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 inhaled  The molecules dissolve in the moist lining of the nasal cavity and trigger an impulse  Olfactory cells send those impulses to the brain, which interprets the impulses as odors  Taste buds and olfactory cells both detect dissolved molecules  The brain combines information from both senses to give sensations of flavor.