UNIT 3 - THE NERVOUS SYSTEM - DIVISIONs - THE NEURON
CHARACTERISTICS COMPLEXITY: nerve cells connecting allow you to do EVERYTHING you will ever do INTEGRATION: brain pulls all information you get together and makes sense of it ADAPTABILITY: the brain and nervous system serve to help us adapt to all the changes going on around you PLASTICITY: brain s capacity for change ELECTROCHEMICAL TRANSMISSION: information is transmitted using electricity
TYPES OF NERVES AFFERENT NERVES: sensory nerves Carry information TO the brain and spinal cord Communicate about the external environment (sunlight) and internal conditions (hunger) EFFERENT NERVES: motor nerves Carry information OUT of the brain and spinal cord Communicate information to the other parts of the body (muscles, glands, organs)
DIVISIONS IN THE NERVOUS SYSTEM 2 main divisions 1. CENTRAL NERVOUS SYSTEM a. Brain and spinal cord b. 99% of all nerve cells are located in the CNS 2. PERIPHERAL SYSTEM a. Everything else but the brain and spinal cord b. Functions to bring info to the PNS c. 2 major divisions
2 DIVISIONS OF THE PNS 1. SOMATIC Nervous System a. Controls voluntary movements b. EX: writing with a pen 2. AUTONOMIC Nervous System a. Controls involuntary movements b. EX: breathing, heart pumping, eye blinking c. Divided into 2 parts
2 DIVISIONS OF THE AUTONOMIC SYSTEM 1. SYMPATHETIC Nervous System a. Prepares the body for action b. Fight or Flight c. Ex: heart rate quickens, hands sweat 2. PARASYMPATHETIC Nervous System a. Calms the body down after an emergency b. Typically tired and lethargic as you calm down
DA NEURON SMALLEST ELEMENT OF THE NERVOUS SYSTEM 100 BILLION IN THE BRAIN
PARTS OF A NEURON 1. Cell Body: contains the nucleus - Directs the manufacturing of substances needed to grow and maintain the neuron 2. Dendrites: on the end of the neuron - Detects messages from other neurons 3. Axon: carries the messages away from the cell body a. Myelin Sheath: layer of fatty cells that insulate the axon - Speeds up transmission - Thicker sheath = faster the speed - Urgency Cells : fastest - M.S. = degenerative disease of the myelin sheath (myelin sheath hardens) 4. Terminal Buttons: relay messages to the next neuron - Release the neurotransmitters
FUNCTIONING OF A NEURON ELECTRIC IMPULSE Only goes in one direction 1/10 th of a volt of electricity Travels from the cell body, down the axon via the myelin sheath and gets relayed from the terminal buttons to the next neuron Picked up by the dendrites of the next neuron
FIRING OF A NEURON ALL OR NOTHING principle Fires or doesn t (like a gun) Resting State When it isn t firing Negative charge Absolute Refectory Period: neuron cannot fire again during this period Relative Refectory Period: can fire again but it needs more stimulate
SYNAPSE Space between the neurons Chemical messages pass through the synapse Neurotransmitters: 2 major types: chemical messages 1. Excitatory tells the next neuron to fire (Excites) 2. Inhibitory tells the next neuron not to fire Reuptake: reabsorption of the neurotransmitters by a terminal button Next neuron picks up the transmission through the dendrites
NEUROTRANSMITTERS Most neurons secrete only one type of neurotransmitter Different neurons are simultaneously secrete different N.T. At any given time, a neuron can be receiving in a mixture of messages More than 50 transmitters have been identified Each have a different chemical makeup.
MAJOR NEUROTRANSMITTERS ACETYLCHOLINE: (ACh) Black widow venom causes a huge release in ACh Too much: muscle spasms and weakness Botox: botulin destroys ACh (paralyzes facial muscles) Alzheimer disease: ACh deficiency NOREPINEPHRINE: stress stimulated (EPI) Inhibits the firing of neurons in the CNS Excites the heart muscles (given to patients whose heart isn t pumping) Too little: associated with depression Too much: triggers agitated state Cocaine = increases amounts of EPI Works with acetylcholine to regulate states of sleep and wakefulness
MORE NEUROTRANSMITTERS DOPAMINE: helps control voluntary movement Affects mood, sleep, attention, and learning Stimulant drugs: (cocaine and amphetamines) activate dopamine receptors Parkinson disease: low levels of dopamine Schizophrenia: associated with HIGH levels SEROTONIN: regulates sleep, mood, attention and learning Low levels: associated with depression Antidepressants: (Prozac) slows down the reuptake of serotonin (increases brain levels)
MORE NEUROTRANSMITTERS ENDORPHINS: natural opiates (depress the nervous system and eliminate pain) Shield the body from pain and elevate feelings of pleasure Ex: Morphine
ASSIGNMENTS NEURON COLORING SHEET NEUROTRANSMITTER ACTIVITY