Presentation on theme: "Neurons & the Nervous System Chapter 2: The Brain and Behavior."— Presentation transcript:
Neurons & the Nervous System Chapter 2: The Brain and Behavior
The Nervous System Central Peripheral Autonomic SympatheticParasympathetic Somatic
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
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
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.
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
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)
Dendrites Cell body (soma) Axon Myelin sheath Terminal buttons
There are more neurons in the brain than stars in the Milky Way
Neuron Activity You will need: –1 black pipe-cleaner –2 white pipe-cleaners –1 blue or orange pipe-cleaner –2 white beads
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?
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
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
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
Axon of sending neuron Terminal button Synaptic cleft Receptor sites Dendrite of receiving neuron
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
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
Velocity of neural impulse is 250 mph Resting potential
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.
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? A B C D E
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
Neurotransmitters Excitatory NT: increases the likelihood that postsynaptic neuron will fire Inhibitory NT: decreases likelihood that postsynaptic neuron will fire