Thinking About Psychology:

The Science of Mind and Behavior 2e

Charles T. Blair-BroekerRandal M. Ernst

As before, with much thanks to:

Neuroscience and Behavior

Neuroscience – scientific study of the

nervous system

• Nervous system- body’s primary communication network

• The nervous system is closely linked to the endocrine system – system of glands that secrete hormones into the blood stream.

Nervous System

• The electrochemical communication system of the body

• Sends messages from the brain to the body for movement

• Brings information to the brain from the senses

Neurons: The Building Blocks of

the Nervous System

Neuron• A nerve cell; the basic building block of the

nervous system• There may be as many as 100 billion

neurons in the brain• Neurons perform three basic tasks

–Receive information–Carry the information–Pass the information on to the next neuron

Parts of the Neuron

Parts of the Neuron - Dendrites

Dendrite – The branching extensions of a neuron that receive information and conduct impulses toward the cell body

Parts of the Neuron - Soma

Soma – The cell body of a neuron, which contains the nucleus and other parts that keep the cell healthy

Parts of the Neuron - Axon

Axon – The extension of a neuron through which neural impulses are sent

Parts of the Neuron – Myelin Sheath

Parts of the Neuron - Terminals

Axon terminals – The endpoint of a neuron where neurotransmitters are stored

• Glial Cells– Specialized support cells for the neurons – More numerous (10x) than neurons

• Structural support• Nutrition• Remove waste• Perhaps involved in communication between

neurons, enhances speed

Types of Neurons• Sensory Neurons (aka afferent neurons)

– Tell us about the environment; share information from specialized receptor cells (in various sense organs) with the brain; also carry info from skin and organs to the brain

• Motor Neurons (aka efferent neurons)– Gets us moving; sends info to the muscles

and glands• Interneurons (aka relay or connector neurons)

– Share info between neurons (there are more of these than the previous two)

Quick question?

What’s the longest axon in your body? {Remember most neurons are terribly

small}

It’s found on the motor neuron that works your big toe.

For a basketball player (7’) it’s 4 feet long; for most people it’s about 3 feet long.

How Neurons Communicate:

The Neural Impulse

Module 6: The Nervous System and the Endocrine System

Action Potential

• A neural impulse; a brief electrical charge that travels down the axon of a neuron

• Considered an “on” condition of the neuron

Changes in charge across the membrane causes ion channels to open and close. In response todepolarization, Na+ channels open quickly andclose slowly. While K+ channels open slowly and close slowly in response to depolarization.

A neuron has to re-set itself after every reaction for the next reaction. Na+ is moved back out while K+ ismoved back in. One protein pumps both potassium and sodium out with the use of energy because both are moving against the concentration gradients. Thenerve re-sets itself by pumping 3 Na+ out and 2 K+ in,which is not an equal exchange. Active transport proteins in the membrane are responsible for pumping Na+ out and K+ in. These proteins require a great deal of energy, or ATP

• Each neuron requires a minimum level of stimulation from other neurons to be activated (stimulus threshold). – While waiting to be stimulated it is said the neuron is

polarized.– In this state the axon’s interior is more negatively

charged than the exterior fluid surrounding the axon.• This condition is due to primarily to different ions:

potassium and sodium.• While the neuron is at resting potential (-70 mv), the

fluid surrounding the fluid surrounding the axon contains a larger concentration of sodium ions than does the fluid within the axon. The fluid within contains a larger concentration of potassium.

• Once stimulated by other neurons or sense receptors, neuron depolarizes beginning action potential…Na+ rush in and K+ rush out and charge of axon is momentarily changed to +30mv (this is the action potential) it happens at each segment of the axon and it goes through the whole process at each segment until it reaches the end and it goes from start to finish through the neuron due to the all-or-nothing principle. After the action potential there is a refractory period where the neuron repolarizes and makes it negative inside and positive outside again(another progressive segment by segment movement) and we’re back at the resting potential.

Action Potential

Refractory Period

• The “recharging phase” during which a a neuron, after firing, cannot generate another action potential

• Once the refractory period is complete the neuron can fire again

Refractory Period

Resting Potential

• The state of a neuron when it is at rest and capable of generating an action potential

• The neuron is set and ready to fire

Resting Potential

All-or-None Principle

• The principle stating that if a neuron fires it always fires at the same intensity

• All action potentials are of the same strength.

• A neuron does NOT fire at 30%, 45% or 90% but at 100% each time it fires.

What’s the speed of Neuron Communication?

• The fastest neural messages zoom around at 270 mph

• The slowest neural messages creep by at 2 mph

• These speeds are based on:– the size of the axon (the greater the

diameter, the faster it moves)– the myelin sheath (myelinated neurons are

faster than non)

A Neural Chain

A Neural Chain

A Neural Chain

A Neural Chain

A Neural Chain

How Neurons Communicate:

Communication Between Neurons

Module 6: The Nervous System and the Endocrine System

Types of Neural Communication

• Electrical – almost instantaneous; only 1% ‘talk’ this way

• Chemical– involves neurotransmitters; 99% of neurons

engage in this 1-way conversation

• Chemical communication occurs when the presynaptic neuron (message sending) creates a chemical substance (neurotransmitter) that diffuses across the synaptic gap and is detected by the postsynaptic neuron (receiving neuron).

Synapse• The point of communication between two

neurons• The tiny, fluid filled gap between the axon

terminal of one neuron and the dendrite of another neuron, synaptic gap.– The action potential cannot jump the gap

1. Presynaptic neuron is activated, it generates an action potential that travels to the end of the axon.

2. The end of the axon has several small branches called axon terminals.

3. Floating in the interior fluid of the axon terminals are tiny sacs called synaptic vesicles.

4. The synaptic vessels hold special chemical messengers manufactured by the neuron called neurotransmitters.

5. NT cross the synaptic gap and attach to the receptor sites on the dendrites surrounding neurons, synaptic transmission.

6. They will then detach and are reabsorbed by the presynaptic neuron so they are recycled and reused, reuptake.

Neurotransmitters

3. After attachment, what happens? Usually - reuptake - the neuro-transmitters, detach and are reabsorbed by the presynaptic neuron, to be used again

NT communicates either an excitatory message or an inhibitory message.

Excitatory Effect

• A neurotransmitter effect that makes it more likely that the receiving neuron will generate an action potential or “fire”.

Inhibitory Effect

• A neurotransmitter effect that makes it less likely that the receiving neuron will generate an action potential or “fire”

• The effect of the NT depends on the receptor site on to which it binds, could have an excitatory effect on one and an inhibitory on another.

• On average, each neuron in the brain communicates directly with 1,000 other neurons. Thus, there are up to 100 TRILLION synaptic interconnections.

• There are nearly a thousand times more synaptic connections in your brain than there are stars in the entire galaxy!!

NT and Their Effects• Physical functioning• Psychological functioning• Too much or too little can have devastating effects

Yet they are present in extremely tiny amount in our brains!

• Effects can be the result of complex interactions of different NT and NT have different effects in different areas of the brain.

Acetylcholine• 1st neurotransmitter discovered• Present in all motor neurons• Stimulates muscles to contract (heart and stomach

too)• Also useful in learning, memory & general thinking• Patients with Alzheimer’s have very little Ach as well

as a depletion of other NT• Nerve gas causes Ach to be continuously released

causing severe muscle spasms that suffocate the victim. Atropine blocks Ach receptor sites saving victims from the nerve gas.

• http://www.psychologytoday.com/blog/brain-babble/201208/paralyze-your-face-fight-depression

Dopamine• Useful in movement, attention, learning and pleasurable

sensations• Addiction to drugs (e.g. nicotine and cocaine) related to

how the drugs increase dopamine’s activity in the brain• Parkinson’s is caused – in part – by deterioration of

dopamine producing neurons in the brain; counteracted some by L-dopa

• Too much dopamine is associated with hallucinations in schizophrenia (drugs work to block dopamine receptors and decrease levels in the brain)

• http://www.psychologytoday.com/blog/greaseless/201112/score-dopamine-repeat-or-not

Serotonin & Norepinephrine• Sleep, moods,

emotions, hunger• Prozac makes

serotonin more available

• Learning & memory retrieval

• Get ready to fight… or RUN!

• (aka noradrenalin)• Involved with

depression and other woes

• http://www.psychologytoday.com/blog/the-antidepressant-diet/201008/serotonin-what-it-is-and-why-its-important-weight-loss

• http://www.psychologytoday.com/blog/psychology-writers/201104/triggering-the-warrior-gene-in-villain-or-hero

• http://www.psychologytoday.com/blog/youth-and-consequences/201001/why-teens-addict-the-elusive-search-happiness

GABA: gamma-aminobutyric acid

• Primarily in the brain• Inhibits neurons, helping to balance and offset

excitatory messages• But very delicate• Too much GABA and learning, motivation and

movement are adversely affected• Too little GABA can cause seizures• Alcohol works by activating GABA relaxation• Same with valium and xanax Too bad ?! oral GABA doesn't cross the blood brain barrier or even make it out of the digestive tract into the bloodstream.

• http://www.psychologytoday.com/blog/brain-sense/201207/new-study-reveals-levels-brain-neurotransmitter-may-be-key-in-adhd

Endorphins (aka endogenous morphines)

• Pert & Snyder (1973) discovered brain’s opiate (morphine, heroine, codeine –derived from the opium poppy) receptor sites, which led to the discovery of endorphins, the body’s own painkillers (100x more potent)

• Released in response to stress or trauma and lower pain perception

• http://www.psychologytoday.com/blog/brain-bootcamp/201009/can-exercise-cure-depression

Neurotransmitters

Neurotransmitters (cont.)

Neurotransmitter Functions ProblemsNorepinephrine arousal depression, stress

learningmemory

GABA inhibition of anxiety disorders

brain activity

Endorphins pain perception opiate addictionpositive emotions

The Structure of the Nervous System

Module 6: The Nervous System and the Endocrine System

The Nervous System

As many as 1 trillion neurons comprise the nervous system

Neurons and nerves are notthe same thing: Nerves are comprised of bundles ofaxons.

The Nervous System

• Central Nervous System & The Peripheral Nervous System

Central Nervous System (CNS)• The brain and spinal cord• Both of which are protected by bone, skull or spinal

column and buoyed by the CSF: cerebrospinal fluid• The brain is the location of most information

processing.• The spinal cord is the main pathway to and from the

brain.• The Neuron is the most important message carrier.

• All thoughts, feelings, and sensations go through the CNS.

• Brain is the command center.• Spinal cord is like a old fashioned, switch board sending

messages and receiving messages.– Sensory receptors send messages along sensory

nerves to the spinal cord and then up to the brain.– To activate muscles the brain sends signals down the

spinal cord to motor nerves to the muscles.– Most behaviors are controlled by the brain.

Spinal Reflex Arcsimple behavior without brain involvement

In a simple reflex arc, such as the knee jerk, a stimulus is detected by a receptor cell, which connects with a sensory neuron. The sensory neuron carries the impulse from thesite of the stimulus to the central nervous system (spinal cord), where it connects with an interneuron. The interneuron connects with a motor neuron, which carries the nerve impulse to an effector, (a muscle), which responds by contracting.

Divisions of the Nervous System

Divisions of the Nervous System

Peripheral Nervous System (PNS)• The sensory and motor nerves that connect the brain and the

spinal cord to the rest of the body• Peripheral means “outer region”

– Communication occurs along bundles of nerves.• The system is subdivided into the somatic and autonomic

nervous systems.

Divisions of the Nervous System

Somatic Nervous System• The division of the peripheral nervous system that controls

the body’s skeletal muscles.• Contains the motor nerves needed for the voluntary muscles.• Communicates sensory information from sensory receptors

along sensory nerves to the CNS.

Divisions of the Nervous System

Autonomic Nervous System• The division of the peripheral nervous

system that controls the glands and muscles of the internal organs

• Monitors the autonomic functions• Controls breathing, blood pressure, and

digestive processes• Sub-divided into the sympathetic and

parasympathetic nervous systems• Not fully automatic, tensing or relaxing

muscles or being very active can raise or lower autonomic functions, also mental imagery can work in the same way.

Divisions of the Nervous System

Sympathetic Nervous System• The part of the autonomic nervous system that

arouses the body to deal with perceived threats• Fight or flight response

– Heart rate increases, digestion stops,and the bronchial tubes in your lungsexpands…increasing the amount of oxygen to the brain and muscles. Pupil dilate to increase vision, your mouthbecomes dry. Sweating occurs due to the increasein energy and heat. This happens to help you deal with the situation but can lead to exhaustion.

• Emotional arousal involves your sympathetic nervous system.

• Heightened arousal can also work against you.

Divisions of the Nervous System

Parasympathetic Nervous System

• The part of the autonomic nervous system that calms the body

• Brings the body back down to a relaxed state

The Sympathetic and Parasympathetic Divisions of the Autonomic Nervous System

The Sympathetic and Parasympathetic Divisions of the Autonomic Nervous System

The Sympathetic and Parasympathetic Divisions of the Autonomic Nervous System

The Sympathetic and Parasympathetic Divisions of the Autonomic Nervous System

The Sympathetic and Parasympathetic Divisions of the Autonomic Nervous System

The Sympathetic and Parasympathetic Divisions of the Autonomic Nervous System

The Sympathetic and Parasympathetic Divisions of the Autonomic Nervous System

The Endocrine System

Module 6: The Nervous System and the Endocrine System

Endocrine System

• One of the body’s two communication systems

• A set of glands that produce hormones-- chemical messengers that circulate in the blood until they reach the appropriate receptor sites at destination organ or tissue

Hormone• Chemical messengers produced by the endocrine

glands and circulated in the blood• Similar to neurotransmitters in that they are also

messengers • Slower communication system, but with longer

lasting effects• Regulate metabolism, growth rate, digestion, blood

pressure, and sexual development and reproduction.• Also involved in emotional response and your

response to stress.

• Release of hormones may be stimulated or inhibited by parts of the nervous system (flight or fight).

• Hormones can promote or inhibit nerve impulses.

• Some hormones and neurotransmitters are chemically identical.

Pituitary Gland• The endocrine system’s gland that, in

conjunction with the brain, controls the other endocrine glands

• Called the “master gland”• Located at the base of the brain and & &

connects to the hypothalamus• Hypothalamus is the liaison between the endocrine and nervous system• Pituitary gland produce growth hormone

and also prolactin & oxytocin

Endocrine System – Pituitary Gland

Adrenal Gland• Endocrine glands that help to arouse the body in times of stress• Located just above the kidneys• Releases epinephrine (adrenaline) and norepinephrine

– During emergencies, when the body needs to be alert, responsive, and self-preserving, epinephrine sends chemical hormonal messages throughout the body to allow for greater muscle strength, stronger lung functions, greater blood volume, and enhanced senses.

– Norepinephrine works like epinephrine in that it also increases blood pressure and stimulates respiration and gastrointestinal contractions, but the two chemicals balance each other. Norepinephrine decreases heart rate and increases the actions of the peripheral nervous system by constricting blood vessels. It also constricts blood vessels in the muscles and skin, and decreases stimulation of the bronchial airways in the lungs to return the body to a state of homeostasis or of basic daily functioning.

Thyroid Gland

• Endocrine gland that helps regulate the energy level in the body

• The thyroid secretes several hormones, collectively called thyroid hormones. The main hormone is thyroxine, also called T4. Thyroid hormones act throughout the body, influencing metabolism, growth and development, and body temperature. During infancy and childhood, adequate thyroid hormone is crucial for brain development.

Endocrine System – Thyroid Gland

Endocrine System – Adrenal Gland

Pancreas• Regulates the level of blood sugar in the blood and

impacts hunger and eating• Two of the main pancreatic hormones are insulin,

which acts to lower blood sugar, and glucagon, which acts to raise blood sugar. Maintaining proper blood sugar levels is crucial to the functioning of key organs including the brain, liver, and kidneys.

Endocrine System – Pancreatic Gland

Sex Glands (aka gonads)

• Ovaries (females) and testes (males) are the glands that influence emotion and physical development.

• Testosterone – primary male hormone• Estrogen – primary female hormone• Males and females have both estrogen

and testosterone in their systems.