Biology and Behavior

Psychology: Chapter 3, Section 1

Journal Question• Answer 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 learned

• How 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?

Objective of this Lesson

• We will find out how messages are transmitted by neurons and describe the functions of the peripheral nervous system

Neural transmission is like a row of falling dominoes

• They transmit in only one direction• The messages keep the same strength throughout

the process, just like dominoes don’t slow down or pick up speed as they fall down

The Nervous System• When we think, dream, learn, feel, and move, we

are involving the nervous system• Our nervous system regulates how much our heart

beats and other internal functions, as well as how we react to the outside world

• When we learn something new, our nervous system registers it and actually changes in order to remember it

Two Main Parts of the Nervous System: Central and Peripheral Nervous System

• Central Nervous System• Consists of Brain and Spinal Cord

Two Main Parts of the Nervous System: Central and Peripheral Nervous System

• Peripheral Nervous System• Sends messages from Central Nervous System

(CNS) to all other parts of the body

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 brain

• Some neurons reach from the lower spine down to the toes, so, yes, there are cells in our body that are several feet long

Components of a Neuron• Neurons are kind of like trees, with parts that look like

branches, roots, or trunks.• The main parts are called the axon, cell body, and

dendrites• The 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.

Diagram of a Neuron

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.)

dendrite

Class Activity• Students stand close together in a line around the

room• Hold hands to form a chain• The chain is one of sensory neurons, coming from a

hand that just grabbed an object• The last person in the chain is the brain• One squeeze of the hand means cold, two means

hot, three means soft, four means hard• See if the brain correctly interpreted the sensation

that was sent• Then the brain sends back a message over the

motor neurons: one squeeze means drop the object, two squeezes means hold on to it

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 neurons• Sensory neurons take senses from the peripheral

nervous system to the central nervous system• Then the central nervous system signals motor neurons

to move certain muscles, in this case, you might pull up your foot and rub it

• Other neurons in his brain enabled him to think over the matter and decide to forgive the person who just stepped on your toe

Three Types of Neurons• Sensory neurons• Collect information from an

animal’s environment• Dendrites respond to

external stimulation such as temperature, touch, taste, smell, light or sound

• Interneurons• interpret signals coming in

from sensory neurons and relay them to motor neurons

• Located only in the brain and the spinal cord

• Motor Neurons• Initiate an animal’s

response to stimuli• Stimulate action by

conveying signals to muscles or glands

Concussions

• If 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.

CTE

•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 level•They 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.

Neurotransmitters: Chemical Messengers

• In the sacs of the axon terminals are chemicals called neurotransmitters

• A 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 bottle

• Neurons can fire hundreds of times per second

Neurotransmitters are sprayed out of the axon sacs like water out of a spray bottle

Neurotransmitters: Chemical Messengers

• There are several different kinds of neurotransmitters

• Each 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 neuron

• The electrical impulse then triggers the neurotransmitters at the end of that neuron

• All these transfers from neuron to neuron happen so fast, it seems almost instantaneous

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.

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

A lack of dopamine

may lead to Parkinson’s

Watch “How Parkinson’s Disease Affects the Body,” https://youtube.com/watch?v=hu4eTijdIv0

Chemistry is a Balancing Act• People who have too much or too little of

norepinephrine and/or serotonin often suffer from depression

• Doctors may prescribe antidepressant drugs to regulate these neurotransmitters

• These 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 correctly

• An alternative to drug therapy for depression is psychological therapy and counseling.

While antidepressants can be helpful for those with a genuine chemical imbalance, they are often overprescribed when

counseling could have been a better option

The Central Nervous System• The spinal cord extends from the brain down the

back• It is about as thick as your thumb• It is protected by the bones of your spine, called the

vertebrae • It transmits messages between the brain and the

muscles and glands throughout the body• If someone injures the spinal cord below the neck,

he or she may become paraplegic • If the injury is in the neck, quadriplegia may be the

result

The spinal cord is encased and protected by the vertebrae

The Central Nervous System• The spinal cord is also involved in spinal reflexes,

which is a simple automatic response to something• For 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.

Like the brain, areas of the spinal cord specialize in certain organs of the body

The Peripheral Nervous System

• The peripheral nervous system transmits messages from the central nervous system to all other parts of the body

• The peripheral nervous system is further divided into two systems: the somatic nervous system and the autonomic nervous system

The Somatic Nervous System• The somatic nervous system transmits sensory

messages to the central nervous system• It 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 down• Also called skeletal nervous system, since it

deals with skeletal muscles that we can control (voluntary muscles).

The Somatic Nervous System consists of sensory and motor neurons

(in blue in this diagram)

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.

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 that

• The sympathetic nervous system deals with stress, and the parasympathetic nervous system deals with peace

The autonomic nervous system handles both sympathetic (stress) and parasympathetic (peace) duties

The Sympathetic Nervous System• Activated when someone is going into action

mode, often because of some stressful event• Sometimes called “fight or flight” mode, a person

(or animal) must decide whether to fight or run away from some tiger chasing after them

• Suppresses digestion, increases heart and respiration rates, and elevates blood pressure

• If 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.)

When you need to decide in a hurry whether to fight or flight, the sympathetic nervous system kicks in

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

The autonomic nervous system balances between “fight or flight,” and “rest and digest”

Assessment

• Copy the chart from page 58 • Answer the three questions on page 59