Neurons & the Nervous System

1. Neurons & the Nervous System Chapter 2: The Brain and Behavior

3. Central v. Peripheral Central contains brain & spinal cord In a computer, this is your central processing unit (CPU) Peripheral – sensory & motor neurons that transmit messages between brain and muscles & glands In a computer, this includes your keyboard, mouse, CD-ROM, printer, etc. Spinal cord is about 43 cm long in women and 45 cm long in men; ¾ inches thick

4. Autonomic v. Somatic Somatic – voluntary - controls purposeful body movements, movements for balance & posture Consciously perceived sensations Autonomic – involuntary – automatic activities such as heartbeat, respiration, digestion, dilation of pupils, etc. Some can be under conscious control (i.e. respiration) Smooth & cardiac muscle, some glands

5. Sympathetic v. Parasympathetic Sympathetic = “Fight-or-flight” response Uses energy reserves to cope with stress or emergency Adrenaline! Parasympathetic = “Rest and digest” Conserves & builds up stored energy reserves The Sympathetic & Parasympathetic systems work together to maintain homeostasis.

7. http://www.youtube.com/watch?v=Y5nj3ZfeYDQ

8. Today’s Goal  You will be able to…. • Identify the parts of a neuron and their functions in creating & sending neural messages.

9. http://www.youtube.com/watch?v=sX87g3AHIbc • http://www.youtube.com/watch?v=5uQZfaURU_Y&feature=related • http://www.youtube.com/watch?v=Y5nj3ZfeYDQ • http://www.youtube.com/watch?v=NqVeH26i7Kg&feature=related

10. Parts of the Neuron • Neurons: nerve cells • Dendrites: branch-like end of neuron which receives messages • Cell body (soma): contains nucleus • Axon: long tail-like end of neuron which transmits (sends) messages There are 100 billion neurons in the human brain There are 300 billion neurons in the octopus brain

11. Myelin: fatty substance that speeds up transmission of impulse • Terminal buttons: bulb-shaped structure at end of axon The longest axon of a neuron belongs to what animal? Giraffe – 15 feet! (from toe to neck)

12. Dendrites Cell body (soma) Axon Myelin sheath Terminal buttons

13. There are more neurons in the brain than stars in the Milky Way

14. Neuron Activity • You will need: • 1 black pipe-cleaner • 2 white pipe-cleaners • 1 blue or orange pipe-cleaner • 2 white beads

15. Neuron Activity • Which part of the neuron do the white pipe-cleaners represent? • Which part of the neuron does the blue pipe-cleaner represent? • Which part of the neuron does the black pipe-cleaner represent? • Which part of the neuron do the white beads represent?

16. Types of Neurons • Afferent (sensory) neurons: send messages from sensory receptors to the spinal cord & brain • Efferent (motor) neurons: relay messages from brain & spinal cord to muscles & glands • Interneurons: transmits neural stimulus between sensory & motor neurons

17. Today’s Goal  You will be able to…. • Describe how a neural impulse is generated and how neurons communicate in the brain and throughout the body. • http://www.youtube.com/watch?v=90cj4NX87Yk&feature=related • http://www.youtube.com/watch?v=DF04XPBj5uc

18. The Synapse • Synapse (synaptic cleft): gap between dendrites of one neuron and axon of another • Receptor sites: parts of dendrite which receive neurotransmitters • Neurotransmitters: chemical substances involved in sending neural impulses Average neuron makes about 1,000 synapses and receives 10,000 synapses

20. Axon of sending neuron Terminal button Synaptic cleft Receptor sites Dendrite of receiving neuron

21. Neural Impulse: electrochemical firing of a nerve cell • Resting potential: electric potential when neuron not firing (-70 millivolts) • Depolarization: neuron reduces resting potential by becoming positively charged

22. Action Potential: neuron fires when it reaches +30-40 millivolts • Repolarization: internal charge becomes more negative • Refractory period: phase after firing an impulse, neuron will not fire • All-or-none principle: neuron will fire or not fire, no in-between

23. Velocity of neural impulse is 250 mph Resting potential

25. Today’s Goal  You will be able to… • Discuss how the major neurotransmitters affect the body and one’s behavior Learning Target: Describe neural communication and discuss the impact of neurotransmitters.

26. Review • Which nervous system is most active during stress or a “fight-or-flight” situation? Sympathetic NS In the graph… • When is the neuron insensitive to incoming messages? • When is the neuron depolarizing? • When is the neuron at its resting potential? • When is the neuron at its action potential? • When is the neuron repolarizing? C B D A E

27. Substances that Affect Neurotransmitters • Agonist: similar to the NT, mimics its effects • Antagonist: inhibits the release of NT by sending neuron, or blocks receptor site for NT on receiving neuron

28. Neurotransmitters • Excitatory NT:increases the likelihood that postsynaptic neuron will fire • Inhibitory NT: decreases likelihood that postsynaptic neuron will fire

29. Neurotransmitters • Acetylcholine (ACh) Function: Muscle contractions, learning, memory EXCITATORY (sometimes inhibitory) Malfunctions: Alzheimer’s Disease

30. Neurotransmitters • Dopamine (DA) Function: Voluntary movement, sensations of pleasure & reward Malfunctions: Too little  Parkinson’s, Too much --> Schizophrenia • Agonists  cocaine & amphetamines • Antagonists  Ritalin, alcohol

31. Neurotransmitters • Serotonin Function: Mood, appetite, sleep, impulsivity, concentration Malfunctions: Depression, Eating Disorders • Agonists  LSD, Prozac

32. Neurotransmitters • Norepinephrine Function: Alertness, arousal, mood, heart rate/appetite Inhibitory & excitatory Malfunctions: Depression • Agonists  Cocaine, amphetamines

33. GABA (most prevalent inhibitory NT) Function: Anxiety, sleep, seizures Malfunctions: Anxiety disorders, tremors, insomnia • Glutamate (main excitatory NT) Function: Memory & learning Malfunctions: Migraines, seizures, addictions • Endorphins Function: Pain control Malfunctions: None

34. Neurotransmitter Song • Choose a popular camp song or rhyme • Change the lyrics to describe a neurotransmitter or several neurotransmitters