2 CNS vs. PNSCNS: Central Nervous SystemBrain and the spinal cord
3 PNS: Peripheral Nervous System Nerve cells that send messages between central nervous system and other parts of the body
4 NeuronsNerve cells that run through our entire body and communicate with each otherMessages relate to certain eventsEx.: memories, learning a new skill, injury
5 In case of injury or disease, the brain can reorganize itself by altering connection between neurons Ability to reorganize neurons in brain = neuroplasticity
6 Parts of a neuron:Cell body: produces energy to fuel neural activity
7 Dendrites: receive information from other neurons and pass the message through the cell body Cell bodies have many dendrites; one axon
8 Axons: transmit messages away from the cell body Vary in length: smaller than an inch to a several feetMyelin: fatty sheath that covers and protects the axonSpeeds transmission of messages sent from neuronsAxon Terminals: fibers holding the axons
9 Communication between Neurons Flow of message:Axon Terminals DendritesMessages move in one direction
10 Synapse: junction between the axon terminal of one cell and the dendrites of the next
11 Sensory Neurons: information received by senses to the CNS Motor Neurons: nerve cells that carry information from the CNS to muscles and glands
12 NeurotransmittersNeurotransmitters: chemicals that are stored in sacs in the axon terminals.Chemical message between two neuronsConverted into an electrical impulse that travels through the neuron, triggers another release of neurotransmitter to go the next neuron, etc.Process takes a fraction of a second
13 Numerous types of neurotransmitter each serves a different purpose Each has its own structure; fits into receptor site on the next neuronImbalance of neurotransmitter can lead to certain diseases or mental disorders
14 Ex.: acetylcholine involved in memory; too little can impair the formation of new memories (possibly tied to Alzheimer’s)Ex.2: dopamine involved in motor behavior; too little can cause trembling hands, problems with balance, and uncoordinated movements (Parkinson’s)
16 Spinal cord: column of nerves; extends from brain down the back Protected by the spineTransmits messages between brain and the muscles and glands
17 Spinal reflexes: automatic response to a trigger without input from the brain Occurs when nerve impulses are received from the body’s sensory organs (eyes, ears, etc.)Message is passed along to the brain but the reflex is carried out without direct input from the brainEx.: touching a hot stove; blinking; tapping the kneecap
18 Peripheral Nervous System Transmits messages between CNS and everywhere else in your bodyDivided between the somatic nervous system (SNS) and the autonomic nervous system (ANS)
19 Somatic Nervous System Transmits sensory messages to the CNSCarry messages from voluntary muscles and sense organs
20 Activated by touch, pain, temperature changes, and body position Allows experiencing of heat/cold, pressure, painEx.: Fuzzy Puppy—feeling warmth from sitting on your lap, soft fur, and pain if the puppy bites you
21 Alerts brain which parts of the body moved; maintains balance and posture
22 Autonomic Nervous System “autonomic” = occurring involuntarily
23 Regulates body’s vital functions like heartbeat, breathing, digestion, blood pressure, etc. Regulates involuntary muscles and internal organs
24 Two divisions: Sympathetic: Parasympathetic: Prepares body for action under stress; “fight or flight”Parasympathetic:Restores body’s reserves of energy after intense activity; body returns to normal“rest and digest”
25 Example of the communication: You see a tiger outside of its cage at the zoo.
26 Sensory neurons relay message to the CNS Sensory neurons relay message to the CNS. “I see a tiger outside of the cage! It’s almost like in nature!”
27 Brain processes the situation Brain processes the situation. The tiger looks pretty cool outside its cage. You’re in a zoo so there has to be an employee near by, but you’re still a bit nervous—this is a new situation. CNS tells you to watch the tiger and look for the employee.
28 You see the employee. He’s laying on the ground, mauled by the tiger You see the employee. He’s laying on the ground, mauled by the tiger. You panic. CNS freezes.
29 PNS (autonomic nervous system) kicks your adrenal glands into overdrive (fight or flight) and your legs begin to break into a run. OR your adrenal glands go into overdrive, you tackle a scared zoo employee, take his/her tranquilizer gun and stop the tiger.
30 After successfully fleeing or fighting the tiger, you feel a bit weak After successfully fleeing or fighting the tiger, you feel a bit weak. Your adrenal glands have slowed down. You feel a need to sit down and eat. The gift shop is nearby; you walk in, get some ice cream and sit on a bench. Your body returns to normal (parasympathetic nervous system).