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The Nervous System I. Response to Stimuli A. your body responds to changes in the environment and adjusts itself B. stimulus: _________________________________________________________________ C. Internal control systems respond to maintain ______________________ D. The nervous system controls and coordinates function throughout the body and responds to internal and ________________ stimuli II. Neurons A. definition: B. receptors: located in skin and sense organs, these transmit stimuli (nerve impulses) to different types of neurons C. types1. ________________________: receive info from sense organs and send impulses to the brain and spinal cord 2. interneurons: relay the impulses from the sensory neurons once they reach the brain or spinal cord to the ________________ neurons (most numerous) 3. _______________________: conduct impulses from the brain or spinal cord to muscles or _____________ throughout the body D. structure: 1. cell body: _______________________________________ 2. dendrite: i. receives messages and sends them to the ___________________ ii. many branched extensions 3. ________________: i. long fiber that carries messages ___________ from the cell body ii. single branched end have swellings called __________________ iii. may have a myelin sheath: insulating membrane which increases the speed at which __________________ can travel E. nerve: clusters of dendrites and axons III. The Nerve Impulse: A. Definition: electrical signals carried by a neuron depending on the movement of negatively charged electrons (e-) B. Resting Potential in a neuron: the difference in electrical charge across a membrane 1. there are more ________________ ions (K+) inside the cell than outside 2. there are more ______________ ions (Na+) outside of the cell than inside 3. these concentrations must be maintained by _________________________ 4. negative charge builds up inside the cell as more K+ ions diffuse out than Na+ diffuse in C. The Moving Impulse 1. a nerve impulse is caused by the movement of ______ across a membrane and begins when a neuron is stimulated by another neuron or its environment 2. a neuron’s cell membrane has 1000’s of _________ channels that allow ions to pass through when the “gates” are opened 3. as an impulse moves down a neuron, the “gates” are opened and ______ flows _______ the cell 4. the cell membrane gains a “+” charge inside and a “–“ charge outside creating an ________________________ 5. as the impulse passes, the K+ gates open and these ions move _________ of the cell and the ______________________ is re-established D. Threshold 1. the strength of the __________ is always the same (you respond or you don’t) 2. the __________ must be of adequate strength to cause an impulse = threshold E. ________________: location at which a neuron can transfer an impulse to another cell 1. a small cleft (gap) separates the ______________________ from the dendrites of the adjacent cell 2. the terminals contain tiny sacs filled with __________________________ (chemicals used by a neuron to transmit impulses across a synapse) 3. when an action potential arrives at the axon terminal, the sacs release the neurotransmitter into the ____________ 4. neurotransmitter diffuses across the cleft and attach themselves to ___________________ on the membrane of the adjacent cell 5. this stimulus causes ___________ to rush across the membrane 6. if the threshold is met, then the impulse begins an action potential in the next cell IV. Central Nervous System (CNS) A. made of the ____________ and __________________________ B. job: relay messages, processes information, and analyzes information C. brain 1. made up of 100 billion neurons (mainly ______________________) 2. divided into 3 major sections i. _____________________ (largest) - responsible for conscious/voluntary activities of the body - divided into 2 sections called ______________________, controlling the opposite side of the body - the _________ hemisphere may control creativity and artistic ability - the left hemisphere may control analytical and mathematical ability - site of learning, judgment, and _____________________ - the cerebral ___________ (outer layer) consists of grey matter with densely packed nerve cell bodies (______________) which process info from the sense organs and control body movements - the inner surface of the cerebrum consists of white matter made up of _____________________________ of the axons ii. ______________________ - behind and under the cerebrum - coordinates _________________ muscle movement - maintains balance and muscle tone iii. brain stem - extends out from the cerebrum and connects the brain to the spinal cord - made up of the midbrain, the pons, and medulla oblongata: these regulate the flow of info to the brain from the rest of the body - controls ___________________, breathing, and blood pressure by coordinating involuntary muscle movements iv. ________________________: - found between the brain stem and cerebrum - receives messages from the _______________________ and relay info to the proper section of the cerebrum v. _________________________ - found between the brain stem and cerebrum - control center for recognition of _____________, hunger, fatigue, _____________, and body temp D. spinal cord 1. extension of the brain stem 2. processes _____________________ 3. made of bundles of neurons that carry impulses from all parts of the body to the brain and from the brain to all parts of your body E. protection 1. the _________________ protects the brain 2. the ___________________ protect the spinal cord 3. both are wrapped in three layers of connective tissue called the meninges 4. space between these layers is filled with _____________________________ that acts as a shock absorber V. Peripheral Nervous System (PNS) A. all of the nerves outside of the central nervous system including the spinal and cranial nerves which connect the brain and spinal cord to other body parts B. made up of 1. 12 pairs of cranial nerves (from brain) 2. 31 pairs of spinal nerves (from cord) which are bundles of sensory and motor neurons C. 2 divisions 1. _________________: transmits impulses from sense organs to the CNS 2. motor: i. transmits impulses from the CNS to __________________________ ii. further divided into the somatic and autonomic system - _________________: cranial and spinal nerves that go from the CNS to your skeletal muscles; voluntary movements and reflex arcs - _________________: controls heart rate, breathing, digestion, and gland functions; involuntary movements; sympathetic and parasympathetic systems V. Reflexes A. definition: _________________________________________________________________ B. involves a simple nerve pathway called a _____________________ Example – touching a hot pan i. sensory receptors in fingers respond to the hot metal ii. an impulse relaying this information is sent via sensory neuron to the spinal cord iii. iv. the impulse passes to an interneuron in the spinal cord impulses are immediately sent to the motor neurons in your arm causing you to move your hand C. reflexes are controlled by your ______________________ D. your brain acts after reflexes occur to help you figure out how to stop the pain, calm heart beat, slow breathing, etc = maintain __________________________ VI. The Senses A. Your senses enable you to hear, see, taste, touch, and smell whatever comes into your environment. B. The energy that stimulates your sense organs may be in the form of light rays, heat, sound waves, chemicals, or pressure. C. Five categories of sensory receptors: 1. ____________________________: throughout body (except brain) that respond to chemicals released by damaged cells 2. thermoreceptors: in ______________________________________________ 3. _____________________________: in skin, skeletal muscles, and inner ears 4. chemoreceptors: ________________________________ 5. ____________________________: in eyes VII. Vision A. Light travels in straight lines/rays and is bent by the ______________ and ___________ B. lens: convex lens that directs the rays onto the retina C. retina: 1. tissue at the back of the eye that is sensitive to light energy 2. contains _________: cells that respond to dim light used to detect shapes and movement 3. contains _______________: cells that respond to bright light and color D. How you see: 1. Light rays are focused by the cornea and lens onto the ______________ and a sharp image is formed 2. Light energy stimulates impulses in the retinal cells which pass impulses to the ________________________ then to the brain. 3. The brain interprets theses impulses = you “see” the image E. Convex lens: 1. thicker in the _______________ and thinner on the _________________ 2. causes parallel light rays to come together at a focus point F. Concave lens: lens that is thicker on the edges and thinner in the middle G. Correcting vision 1. _______________________ i. if the eyeball is too ______________, light from distant objects is focused just in ____________ of the retina and a blurred image is formed ii. _________________ lenses are used to correct 2. farsightedness i. if the eyeball is too ____________, light from nearby objects is focused ________________ the retina and a blurred image is formed ii. __________________ lenses are used to correct VIII. Hearing A. How you hear: 1. When objects vibrate, they cause the air around them to vibrate creating energy in the form of sound waves. 2. When the waves reach your ears they stimulate nerve cells deep in the ear. 3. impulses are sent from these cells to the brain 4. the brain responds and you hear a sound B. the ear is divided into 3 sections 1. ________________ i. traps sound waves and funnels them into the ear canal and middle ear ii. the sound waves cause the eardrum (membrane) to vibrate like a drum 2. ____________________ i. vibrations from the eardrum cause little bones (__________, __________, ____________________) to vibrate ii. the stirrup bone rests against a second membrane on the opening of the inner ear 3. inner ear i. _____________: fluid filled structure like a snail’s shell that vibrates from the stirrup’s vibrations causing nerve endings to send impulses to the brain via the ________________________ nerve ii. high-pitch sounds make the nerve endings move differently than lowpitched sounds iii. balance is also controlled here - special structures and fluids in the _________________________ are constantly adjusting to the position of your head - this stimulates impulses to the brain which interprets the position to help you adjust and maintain your balance IX. Smell A. Food gives off gas molecules into the air which are taken into the nasal passage B. _____________________cells are moistened; specialized nerve cells that are stimulated by the gas molecules when these molecules dissolve in the moisture C. If enough molecules are present, am impulse starts in these cells and travels to the brain and you “smell” the item X. Taste A. Taste buds on your tongue are the major chemical sensory receptors for taste B. 10,000 taste buds in your mouth C. In order to taste something, the food must be dissolved in ______________, therefore the nervous system triggers salivation when it is time to eat D. The solution of saliva and food molecules wash over your taste buds and an impulse is sent to the brain E. The brain interprets the impulse and you can taste the food. F. Four basic areas of taste buds: ____________________________________ G. When you are sick, you have trouble tasting food because the gas molecules are blocked from dissolving in the moist membranes of the nasal passage. XI. Touch, Pressure, Pain and Temperature A. Receptors in the skin (_____________) pick up changes in touch, pressure, and temperature and transmit impulse to the brain or spinal cord B. The body will respond to maintain homeostasis