The Nervous System

The Nervous and Endocrine SystemsUnit 3, Part 21The Nervous SystemRapid Response System2The NeuronBasic functional unit of nervous systemNerves bundles of neurons3 basic parts:Dendrites receptors that receive stimuli; one neuron may have many dendrites and branches of dendritesCell body contain nucleus and organellesAxon long fiber that transmits impulse away from cell body; only one per neuronTrillions of neurons in body transmit information in the form of electrical and chemical impulses

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4The Resting NeuronNot transmitting an impulseOutside of the cell - a net positive chargeInside of the cell - a net negative chargeElectrical charge across the cell membrane of a resting neuron is called the resting potentialThese charges come from the Sodium Potassium Pump in cell membraneNa+ ions pumped out of cell; K- ions pumped into cell by active transport

5The Moving ImpulseA neuron remains in its resting state until it receives an impulseAn impulse begins when a neuron is stimulated by another neuron or the environment Na+ ions flow into the neuron and the inside of the cell temporarily becomes more positive than the outsideThe change from negative to positive is called a nerve impulse or an action potential

6The Moving ImpulseThe impulse travels down the axon away from the cell bodyAs impulse passes Na+ flows out of the neuron and the resting impulse is restoredThe neuron has a negative charge on the inside and a positive charge on the outsideThreshold minimum amount of stimulus needed to trigger impulse7The Moving ImpulseSynapse - the location at which a neuron can transfer an impulse to another cell

Neurotransmitters chemical messengers that transmit impulse across synapse

8Classification of NeuronsSensory neurons detect stimuli and transmit info from:SkinMusclesJointsSensory organsInternal organsSensory stimuli include:TasteTouchSmellHearingVision

Sensory impulses go to the spinal cord and brain9Classification of NeuronsMotor Neurons send impulses from spinal cord and brain to the muscles or glandsInterneurons found in the spinal cord; connect sensory and motor neurons in reflex arc

Myelin lipid-based substance that surrounds axon and acts as an insulatorIncreases speed of impulseNot found on neurons in the brain10

11The Reflex ArcReflex arc specialized nerve pathway that does not require conscious thoughtExamples:Pupil constriction/expansion response to lightPulling back hand from hot surfaceKicking foot out when certain tendon is hitPathway:Sensory neuron Interneuron Motor Neuron

12Anatomy of the Nervous SystemFunctions:Control and coordinate functions throughout the bodyRespond to internal and external stimuli2 Subsystems:Central Nervous System (CNS)BrainSpinal CordPeripheral Nervous System (PNS)Attach rest of body to CNS13

Anatomy of the Nervous System14Parts of Central Nervous System:Brain:Cerebrum - responsible for voluntary activities of the bodyCerebellum - responsible for coordination and balance of the actions of the musclesHelps the body to move gracefully and efficientlyBrain Stem - regulates information flow between the brain and the rest of the bodyControls basic life process breathing and heartbeatSpinal Cord: major communication link between brain ad rest of body

Anatomy of the Nervous System15Parts of the Peripheral Nervous System:Somatic Nervous System regulates activities under conscious controlAutonomic Nervous System controls automatic or involuntary responsescontributes to homeostasis by managing other body systemsSympathetic nervous system responds to internal and external demands; fight or flightParasympathetic nervous system returns the body to a balanced state; rest and digest

The Endocrine SystemNot So Rapid Response System16Hormones17Hormones - chemicals that travel the circulatory system to specific organs or cellsSteroid HormonesLipid-based (cholesterol)Able to diffuse across the cell membrane of target cellInside cell, hormone attaches to receptor protein and is taken to the nucleusInfluences DNA to produce specific proteinsNon-steroid HormonesAmino acid-basedAttach to receptor on cell membraneInside cell, hormone triggers chemical reactions in cellEndocrine Glands18Gland an organ that produces and secretes chemicalsMajor glands:Pituitary master gland; controls other glandsThyroid controls metabolismParathyroid maintains calcium levels in blood/boneAdrenal fight or flight; regulates sodium/potassium levels; anti-inflammatoryPancreas controls blood glucoseOvaries produces eggs; hormones estrogen and progesteroneTestes produces sperm; hormone testosterone

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Hypothalamus Center of brain;Communication between nervous andendocrine Systems

Pineal Gland Regulates body clockFeedback Mechanisms20All of your body systems work together to maintain homeostasisThe nervous and endocrine systems have the most control over this processThese systems use feedback loops to accomplish this

Feedback loop:Hypothalamus & pituitary monitor hormone levels in bloodLevel drops: message sent to increase production of hormoneLevel rises: message sent to cancel first messageFeedback Mechanisms21Feedback inhibition (negative feedback) is the process in which a stimulus produces a response that opposes the original stimulus

Feedback Mechanisms22Examples:Shivering and sweating are responses triggered by the nervous system to try to bring the body back to a set pointEating when you are hungry/stopping when you are full

Feedback Mechanisms23Most feedback mechanisms are negative; childbirth is an example of positive feedbackOxytocin and the prostaglandins cause uterine contractions that, in turn, stimulate the release of more oxytocin and prostaglandins. This is partially due to pressure of the babys head against the cervix that both dilates the cervix and acts on cervical nerve endings to stimulate the production of oxytocin

Diabetes24Sometimes the negative feedback loop does not work properlyToo much or not enough hormone is madeDiabetes-disease in which production of insulin by pancreas is inadequate for homeostasisFunctions of insulin:Allow glucose to diffuse across membrane into cell where it is converted to ATPStores excess ATP made by the cell as glycogen in skeletal muscle & liver cellsAlso stores excess ATP as triglycerides in fat tissue

Diabetes25Function of Pancreas:Secrete insulin to reduce total blood sugar levelSecrete glucagon to increase total blood sugar level from stored supplies of glycogen and triglycerides

Diabetes26Types of Diabetes:Type 1- usually diagnosed in people under 30, including children; hereditary;Cannot produce insulinMust take insulin multiple times/dayCannot be prevented/reversedType 2 Typically occurs in adults; seeing more in younger people; result of dietProduce insulin but body has developed a resistance to its effectMust take more insulin to get same effectCan be prevented/reversedEffects of Uncontrolled Diabetes27Body cells cannot access and adequate supply of cellular energy to carry out normal functionBlindnessKidney failureHeart attacksCirculatory issuesTissue death