2 Journal QuestionAnswer these questions as best as you can in your journal. You will refer back to your answers when have completed chapter 3 to see how much you have learnedHow closely are biology and psychology related?What do biology and psychology have in common?How do biology and psychology differ?Do biologists and psychologists use the same medical terms? Why or why not?
3 Objective of this Lesson We will find out how messages are transmitted by neurons and describe the functions of the peripheral nervous system
4 Neural transmission is like a row of falling dominoes They transmit in only one directionThe messages keep the same strength throughout the process, just like dominoes don’t slow down or pick up speed as they fall down
5 The Nervous SystemWhen we think, dream, learn, feel, and move, we are involving the nervous systemOur nervous system regulates how much our heart beats and other internal functions, as well as how we react to the outside worldWhen we learn something new, our nervous system registers it and actually changes in order to remember it
6 Two Main Parts of the Nervous System: Central and Peripheral Nervous System Central Nervous SystemConsists of Brain and Spinal Cord
7 Two Main Parts of the Nervous System: Central and Peripheral Nervous System Sends messages from Central Nervous System (CNS) to all other parts ofthe body
8 Neurons Nerve cells are called neurons. Neurons run through our entire bodies and communicate with each other.Each of us has as many as 10,000,000,000,000 (10 trillion) neurons in our body, most of which are in our brainSome neurons reach from the lower spine down to the toes, so, yes, there are cells in our body that are several feet long
9 Components of a NeuronNeurons are kind of like trees, with parts that look like branches, roots, or trunks.The main parts are called the axon, cell body, and dendritesThe dendrites of one neuron intermingle with the axon terminals of another.The dendrites carry information into the cell, and the axon carries it to the dendrites on the next neuron.Many axons are covered with the myelin sheath, made of a white fatty substance, which helps speed up the transmission of the message.If these sheaths are damaged, then you have Multiple Sclerosis.
11 The Communication Process Messages go from the axon terminals of one neuron to the dendrites of another neuron.The message must cross a gap called the synapse.Messages only travel in one direction.New synapses can develop between neurons that were not connected before, as we learn something new. (Some synapses were just formed right there, as we said this.)
13 Class Activity Students stand close together in a line around the room Hold hands to form a chainThe chain is one of sensory neurons, coming from a hand that just grabbed an objectThe last person in the chain is the brainOne squeeze of the hand means cold, two means hot, three means soft, four means hardSee if the brain correctly interpreted the sensation that was sentThen the brain sends back a message over the motor neurons: one squeeze means drop the object, two squeezes means hold on to it
14 Sensory and Motor Neurons How does your body know when someone has stepped on your toe?The pain in your toe is transmitted to your brain through sensory neuronsSensory neurons take senses from the peripheral nervous system to the central nervous systemThen the central nervous system signals motor neurons to move certain muscles, in this case, you might pull up your foot and rub itOther neurons in his brain enabled him to think over the matter and decide to forgive the person who just stepped on your toe
15 Three Types of Neurons Sensory neurons Collect information from an animal’s environmentDendrites respond to external stimulation such as temperature, touch, taste, smell, light or soundInterneuronsinterpret signals coming in from sensory neurons and relay them to motor neuronsLocated only in the brain and the spinal cordMotor NeuronsInitiate an animal’s response to stimuliStimulate action by conveying signals to muscles or glands
16 ConcussionsIf the brain hits too hard against the skull, it can get bruised. This is called a concussion.When this happens, the message sending system can be interrupted.Football players who suffer a concussion often talk about remembering being at a game, but not being able to remember any details about this game.This shows that memory is a biological process.
17 The effects of concussion were first medically described in 1928, in “punch drunk” boxers. These are the atrophied brains of various ex-football players, including those who just played at the high school levelThey have abnormal deposits of a protein called tau, which shows up as brown spots on the brain.That’s the hallmark of a neurodegenerative brain disorder called chronic traumatic encephalopathy, or CTE.Tau is the glue that holds the microtubules together — the cells’ backbones if you will.When neurons are wrenched apart by a concussion, tau forms into tangles – just as it does in soldiers exposed to bomb blasts, just as it does in people with Alzheimer’s. CTE is where you can end up after multiple concussions, especially if you’re not given time to recover from them.Hallmarks include short-term memory problems, loss of planning/organizational skills and judgment, dementia, irritability, aggressiveness, paranoia and depression/suicidality.CTE
18 Neurotransmitters: Chemical Messengers In the sacs of the axon terminals are chemicals called neurotransmittersA neuron fires its message by releasing these chemicals from the axon to the dendrite across the synapse.Neurotransmitters are sprayed out of the axon sacs like water out of a spray bottleNeurons can fire hundreds of times per second
19 Neurotransmitters are sprayed out of the axon sacs like water out of a spray bottle
20 Neurotransmitters: Chemical Messengers There are several different kinds of neurotransmittersEach has its own structure and fits into the receptor site like a key fits into a lock.The message is then converted from a chemical to an electrical impulse that travels the length of the neuronThe electrical impulse then triggers the neurotransmitters at the end of that neuronAll these transfers from neuron to neuron happen so fast, it seems almost instantaneous
21 Neurons are regulated by their receptors (lock) binding to neurotransmitter molecules (keys) in the brain. In some cases, multiple keys with similar structures can activate the same lock.
22 Kinds of Neurotransmitters Acetylcholine (ACh): Motor Neurons use this to control muscles. It also helps the brain remember.Dopamine: Motor behavior. Too little and you may have Parkinson’s Disease (and shake a lot, or have rigid muscles). Too much and you may have schizophrenia.Serotonin: Emotional arousal and sleep
23 A lack of dopamine may lead to Parkinson’s Watch “How Parkinson’s Disease Affects the Body,”
24 Chemistry is a Balancing Act People who have too much or too little of norepinephrine and/or serotonin often suffer from depressionDoctors may prescribe antidepressant drugs to regulate these neurotransmittersThese drugs can be profitable for drug companies, but their effect is often modest and the side effects can be harmful, as it can be hard to balance the chemicals correctlyAn alternative to drug therapy for depression is psychological therapy and counseling.
25 While antidepressants can be helpful for those with a genuine chemical imbalance, they are often overprescribed when counseling could have been a better option
26 The Central Nervous System The spinal cord extends from the brain down the backIt is about as thick as your thumbIt is protected by the bones of your spine, called the vertebraeIt transmits messages between the brain and the muscles and glands throughout the bodyIf someone injures the spinal cord below the neck, he or she may become paraplegicIf the injury is in the neck, quadriplegia may be the result
27 The spinal cord is encased and protected by the vertebrae
28 The Central Nervous System The spinal cord is also involved in spinal reflexes, which is a simple automatic response to somethingFor example, if someone touches a hot stove, he or she will immediately pull the hand away. The person does not have to think about it. There may be pain, but in many cases, the pain comes after the immediate reflex.Since the person did not waste any time sending this message all the way to the brain, but only to the spinal cord, the chance of getting seriously burned is lessened.Other reflexes are blinking or sneezing.
29 Like the brain, areas of the spinal cord specialize in certain organs of the body
30 The Peripheral Nervous System The peripheral nervous system transmits messages from the central nervous system to all other parts of the bodyThe peripheral nervous system is further divided into two systems: the somatic nervous system and the autonomic nervous system
32 The Somatic Nervous System The somatic nervous system transmits sensory messages to the central nervous systemIt is activated by touch, pain, change in temperature, and change of body position.It also sends messages to our muscles regarding our balance, so we don’t fall downAlso called skeletal nervous system, since it deals with skeletal muscles that we can control (voluntary muscles).
33 The Somatic Nervous System consists of sensory and motor neurons (in blue in this diagram)
34 The Autonomic Nervous System Autonomic basically means the same thing as automatic, so the autonomic nervous system handles the involuntary functions– heartbeat, breathing, digestion, etc. (You don’t have to remember to beat your heart.)When someone encounters something stressful, that affects the autonomic nervous system.
36 The Autonomic Nervous System The autonomic nervous system is basically divided into two systems: the sympathetic nervous system and the parasympathetic nervous system.There are some other divisions, like enteric, which helps with digestion, but we won’t worry too much about thatThe sympathetic nervous system deals with stress, and the parasympathetic nervous system deals with peace
37 The autonomic nervous system handles both sympathetic (stress) and parasympathetic (peace) duties
38 The Sympathetic Nervous System Activated when someone is going into action mode, often because of some stressful eventSometimes called “fight or flight” mode, a person (or animal) must decide whether to fight or run away from some tiger chasing after themSuppresses digestion, increases heart and respiration rates, and elevates blood pressureIf you feel a little sick to your stomach when you get a pop quiz, that is because your sympathetic nervous system has suppressed your digestion. (So anxiety can cause indigestion.)
39 When you need to decide in a hurry whether to fight or flight, the sympathetic nervous system kicks in
40 The Parasympathetic Nervous System The parasympathetic nervous system calms your body down.Heart rate, blood pressure, respiration rate, and digestion are all restored to normal
41 The autonomic nervous system balances between “fight or flight,” and “rest and digest”