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Biology Anatomy and Physiology The Nervous System Basics Function of the Nervous System Mediates (coordinates) communication between different parts of the body and the body’s interactions with the environment The Neuron specialized cells within the nervous system Nucleus Axon terminals Cell body Myelin sheath Nodes Axon Dendrites Neurons transmit messages • Nerve impulse = Message Dendrites- pick up message from environment or other neurons. Sends message to cell body Cell body-performs normal cell tasks for cell, relays message to next neuron through the axon Axon- Carries message from the cell body to the next neuron. myelin sheeth-coating that insulates and speeds up message. axon terminal- releases chemicals, “neurotransmitters” to stimulate the next neuron to “fire” or continue the nerve impulse. threshold- the minimal amount of stimulus required to cause the next neuron to “fire” or continue the impulse Nerve Impulses Are Electrical As They Travel Through The Neuron Outside of cell Cell membrane Resting Potential-When a neuron is ready “fire” if it is hit with a “threshold” stimulus High Potassium Ion (K+)Concentration Inside Low Potassium Ion (K+)Concentration Outside High Sodium Ion (Na+) Concentration Outside Low Sodium Ion (Na+)Concentration Inside 1)Sodium is pumped out by a protein pump *ATP needed 2)Potassium ions leak through cell membrane creating a negative charge inside cell and positive charge outside cell Inside of cell RESTING POTENTIAL NOW REACH WHEN INSIDE HAS BECOME NEGATIVE Movement of the “Action” Potential Action Potential = A electrical charge moving through a neuron CAUSED BY SODIUM GATES OPENING ALLOWING Na+ IN Action Potential As the action potential passes, potassium gates open, allowing K+ ions to flow out. At rest. Action Potential Action Potential At the leading edge of the impulse, the sodium gates open. The membrane becomes more permeable to Na+ ions and an action potential occurs. The action potential continues to move along the axon in the direction of the nerve impulse. Once Action Potential Passes Na + Gates Close and Na+ Pumped Back Out and Resting Potential Restored Types of Neurons Sensory Neurons-detect stimulus send a nerve impulse to brain (sensation) Interneurons-located in the brain, process information received and formulate responses (thought) Motor Neurons- carry an “action” or response impulse from the brain back to the body (response) REFLEX ARC What is the pathway of nerve impulse as your hand touches a hot stove? SENSORY NEURONINTERNEURONMOTOR NEURON This is called the a reflex or reflex arc? This process can also occur with conscious control. Can you think of an example of this? The Central Nervous System • Consists of the brain and spinal cord • Both the brain and spinal cord is wrapped in 3 layers of connective tissues called the meninges. – dura mater, arachnoid, pia matter • Between the meninges and the brain/spinal cord is cerebrospinal fluid – Bathes brain and spinal cord – Shock absorber – Exchange of nutrients and waste between blood and nervous tissue The Brain • http://kidshealth.org/misc/movie/bodybasic s/bodybasics_brain.html – Cerebrum – Cerebellum – Pons – Medulla Oblongata – Thalamus – Hypothalamus – Pituitary Gland – KNOW WHAT EACH DOES!!! The Spinal Cord • Like a “major telephone line” • 31 pairs of spinal nerves branch out from the spinal cord to the rest of the body. – Reflexes may be processed directly by the spinal cord The Peripheral Nervous System • The peripheral nervous system lies outside the central nervous system. • The peripheral nervous system consists of the peripheral nerves throughout the body (outside of spinal cord) and the sensory organs The Peripheral Nervous System Sensory vs Motor Divisons • Sensory Division – transmits sensory impulses from the sense organs to the central nervous system • Motor Division – transmits response impulses from the central nervous system to the muscles and glands – The motor division is further divided into the somatic and autonomic division The Sensory Division Sense Organs • • • • • Nose=Smell Mouth=Taste Ears=Sound Eyes=Sight Skin=Touch – All have specialized sensory neurons to pick up or detect stimulus that transmit impulses to the brain for processing Types of Sensory Receptors • Pain receptors- respond to chemicals released by damaged cells • Located everywhere except brain, essential to bodies ability to detect injury or illness • Thermoreceptors- detect changes in temperature • Located in skin, body core, and hypothalamus • Mechanoreceptors- sensitive to touch, pressure • Found within skin, skeletal muscles, and ears • Chemoreceptors- sensitive to chemical in external environment entering the body • Located in nose and taste buds • Photoreceptors- sensitive to light • Located on the retina within the eye Motor Division Somatic Nervous System • Regulates activities that are under conscious control such as movement of the skeletal muscles. Motor Division Autonomic Nervous System • The autonomic nervous system regulates activities that are automatic or involuntary control – Heart beat, blood pressure, sweating ect… – sympathetic vs parasympathetic • Sympathetic-speed up systems (like a gas pedal) • Parasympathetic- slow down systems (like a brake)
