THE NERVOUS SYSTEM HOW DOES IT WORK? Video:

Purpose: Controls and coordinates the body’s response to changes in the environmentControls and coordinates the body’s response to changes in the environmentWhy? Failure to respond may result in disease or deathFailure to respond may result in disease or deathHow? Uses neurons to send electrical messages (impulses)

A. Stimulus and Response i. stimuli is a change in the internal or external environment of the body –Receptors are used to detect stimuli (sensory organs) (ie. Ears, skin, nose, mouth) ii. response is the way you react to a certain stimuli Effectors are organs that produce the response (ie. muscles or glands)

StimuliResponse Bright light Blink, squint hunger Salivate, stomach growls Wasp or bee Swat, move away

Neurons: (nerve cells) nerve cells specialized for receiving and transmitting impulses/signals functioning units of the nervous system

Axon terminals Myelin sheath Nodes Cell body Axon Nucleus Dendrites Section 35-2 A Neuron

1. Nerve cell (neuron) “DCATS” – order of impulse 1 = dendriteDetects stimulus Starts impulse 2 = cyton (cell body) Has nucleus 3 = axon (covered by myelin sheath) Carries nerve impulses sheath insulates axon 4 = endbrushesTerminal branches Release neurotransmitters across synapse to another neuron 5 = synapseThe space between neurons where impulses “jump” from one neuron to the next 5 D C A T S

Neurotransmitter –Chemicals used to help transfer the impulse across the synapse –Found in tiny sacs (vesicles) at the axon terminals

 Sensory  From sense organs (eyes, nose, skin, ears, tongue) to brain/spinal cord  Interneurons  Interconnect other two types  Found in brain and spinal cord  Motor  From brain/spinal cord to muscles/glands – 3. Nerves – bundle of neurons that transmits impulses 4. Types of neurons

Reflex Arc (Loop) Quick involuntary action that doesn’t involve the brainQuick involuntary action that doesn’t involve the brain Neurons may release chemicals to stimulate each other, or these chemicals may be released to stimulate a muscle or gland. An example of a muscle being stimulated by a neuron appears after the reflex path pictured in number four in the diagram. Receptor Effector

“RSIME”- order of stimulus R- RECEPTOR (DETECTS STIMULUS)- SENSORY ORGAN S- SENSORY I- INTERNEURON M- MOTOR NEURON E- EFFECTOR (RESPONDS TO STIMULI)- MUSCLE OR GLAND

The Nervous System How is it made up? us-System-how-it-works

Divisions of the Nervous System The nervous system is divided into 2 main parts:The nervous system is divided into 2 main parts: –The Central Nervous System (CNS) –The Peripheral Nervous System (PNS)

CNS cerebrum: center for voluntary activity interprets sensory impulses, initiates some motor activities, and responsible for memory, thinking and reasoning cerebellum: coordinates motor activities and aids in maintaining balance medulla: controls involuntary activities such as breathing, heartbeat, blood pressure and peristalsis (is part of the brain stem) Brain stemBrain stem –Connects brain to spinal cord –Consists of Medulla oblongata (heart rate, etc)Medulla oblongata (heart rate, etc) SPINAL CORD

1.Central Nervous System (CNS) Consists of the brainConsists of the brain & spinal cord & spinal cord 2. Peripheral Nervous System (PNS) Includes all the spinal nerves TWO FUNCTIONS a) TRANSFER IMPULSES FROM SENSE ORGANS  CNS b) TRANSFER IMPULSES FROM CNS  MUSCLES OR GLANDS

D. Nervous System Disorders Very serious: the nervous system CANNOT repair itselfVery serious: the nervous system CANNOT repair itself 1. Stroke – cerebral bleeding or clot 2. Parkinson’s disease – missing dopamine (neurotransmitter); movement related problems (ie. Shaky) 3. Alzheimer’s – interference w/ brain neurons causing cognitive problems (memory loss, recognition, etc) 4. Meningitis – bacterial or viral

Pons Pituitary gland Hypothalamus Cerebrum Medulla oblongata Spinal cord Cerebellum Pineal gland Thalamus Section 35-3 The Brain

Disorders  Stroke Results from a cerebral hemorrhage or blood clot in a cerebral BV blocking blood flow to brain  Parkinson’s Disease Loss of the functioning of a particular group of nerve cells in brain  May be due to a shortage of dopamine  Scientific American Frontiers - Season 3 Prescription poison Scientific American Frontiers - Season 3

Parkinson’s Disease  Symptoms Shaking Poor balance Lack of coordination Stiffening of Muscles  Cause Triggered by by environmental factors  Genetic tendency

Disorders  Alzheimer’s  Progressive degenerative disease that advances over time  Symptoms Memory loss Inability to think, speak or care for oneself  Multiple Sclerosis  Cells in the brain and spinal cord do not function properly due to destruction of myelin sheath  Symptoms Shaking of hands Blurred vision Slurred speech Muscle weakness Loss of bladder control