4 Neuroscience And Behavior Chpt 2

Neuroscience and Behavior Chapter 2 57-97

Introduction to Neuroscience 

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Everything psychological is physiological. In the early 1800’s phrenology was the beginning of neuroscience. Phrenology was the idea that you could tell about a person’s personality or mental skills from the shape of their head.

Biological Psychologists 

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Scientists who study the relationship between biological activity and behavior call themselves many things, behavioral neuroscientists, physiological psychologists, or biopsychologists. Humans have the highest brain to body weight ratio of any animal. Most of that is due to our large cerebral cortex or cerebrum.

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Neural Communication (p58Neurons are 65) the most basic building block of all psychology and the nervous system. Neurons are a specialized cell. Cells are the building blocks of all living things, the smallest unit of life that can exist.

Neurons 

Each Neuron has a cell body, from which branches of dendrites receive messages from other neurons. Then the large axon fiber transmits the message to other neurons or muscles or glands. Axons can actually be several feet long. A myelin sheath covers the axon and helps speed along the messages, finally the message is released from terminal branches at the end of the axon.

5 Special Proteins 

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In addition to normal cell activities neurons make some special types of proteins that help them in their job. Ion pumps (provide active transport of certain ions in the cell membrane) Ion channels (passive transport) Messenger proteins (neurotransmitter) Receptor proteins (are used to receive chemical signals) Enzymes (proteins) that degrade neurotransmitters

Types of Neurons 

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Sensory neurons – Input: vision, audition, smell, taste, touch, balance, proprioception Interneurons – most numerous, make up most of the brain and allow internal communication within the nervous system. Motor neurons – Output: movement, behavior

The Action Potential 

Neurons are connected not to just one other neuron but to hundreds or even thousands of other neurons.

Action Potential 

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Every millisecond a neuron will be receiving messages from these other neurons. Neurons receive only one of two messages: - EPSP (excitatory post synaptic potential) FIRE! - IPSP (inhibitory post-synaptic potential) Don’t Fire! The neuron will calculate all the messages it gets, if it gets more excitatory messages than inhibitory messages it will reach its threshold and fire the action potential. The action potential goes down the axon away from the cell body only. Action potentials are an all or nothing action, there are no partial action potentials.

Action Potential 

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The action potential is an electrical charge created by chemical reactions This is done by electrically charged atoms called ions. The interior of an axon has an excess of negatively charged ions making it negative. The outside of an axon has an excess of positively charged ions making it positive. This normal state is called the resting potential

Action Potential 

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When an neuron receives enough EPSPs it changes the polarity of the selectively permeable axon membrane closest to the cell body and allows positive sodium ions to rush in. This depolarizes the next part of the axon and so on. After the reaction the axon goes back to normal in a short amount of time called the refractory period. This process can repeat 100 or even 1000 times a second.

Active and passive ion movement 

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Ions are moved in and out of the selectively permeable membrane by ion pumps and channels in the cell membrane http://www.brookscole.com/chemistry_d/templates/student_resourc

Ion pump – uses energy

Ion channel – doesn’t need energy

The Synapse and  Action Potentials cause the release of Neurotransmitters neurotransmitters from axon terminals into the

synapse, or a tiny space between where one neuron ends and another begins.

Neurotransmitter release 

Within 1/10,000th of a second neurotransmitters cross the synaptic gap and bind to receptor cells on the other neuron, like the action potential this lets ions enter the receiving neuron making either EPSPs or IPSPs

Reuptake 

Reuptake is a process by which neurotransmitters are reabsorbed by the neurons who sent them. This is important because if it did not happen the neurotransmitters would continue to trigger EPSPs as long as they were in the synapse.

Neurotransmitters Acetylcholine (ACH)

Enables muscle action, learning and memory

Undersupply causes Alzheimer’s

Dopamine

Influences movement, learning, attention, and emotion

Excess receptors = schizophrenia, lack of = Parkinson’s

Serotonin

Affects mood, hunger, sleep, arousal

Undersupply = depression

Norepinephrine

Helps control alertness and arousal

Undersupply = seizures, insomnia

Glutamate

Major excitatory neurotransmitter; involved in memory

Oversupply can over stimulate brain; migraines; seizures

Neurotransmitters continued Undersupply linked to GABA (gamma- Major inhibitory aminobutyric acid)

neurotransmitter

seizures, tremors and insomnia

Endorphins - are naturally occurring neurotransmitters that act as opiates. They are released usually in times of great pain or vigorous exercise. Because of the body has receptors for these transmitters this is why opiates (morphine, vicodin, oxy-contin, heroin, etc.) are so effective at producing a pleasurable, pain relieving feeling in humans. Because endorphins are not normally occurring in great quantities its very easy to flood the body with them but then its very hard to replace them naturally – this is why opiates are so addictive.

How Drugs and other Chemicals affect Neurotransmission 

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Drugs affect neurotransmission in one of three ways: Agonists – excite…are shaped enough just like a regular neurotransmitter to trigger the same effect. Antagonists – inhibit… may be shaped enough like a neurotransmitter to rest on a receptor site blocking other transmitters but it itself does not trigger a response at the site.

The Nervous System The three types of neurons, sensory, interneurons, and motor neurons make up the Nervous System which is categorized into these major divisions:

The Nervous System Central (brain and spinal cord)

Peripheral

Autonomic (controls self regulated Actions of internal organs And glands)

Somatic (controls voluntary movements Of skeletal muscles)

Sympathetic (arousing) Parasympathetic (calming)

The Peripheral Nervous System 

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As the chart indicates the peripheral nervous system is made of 2 parts the autonomic and somatic systems. The somatic nerves control your voluntary muscles, your movement. The automatic system controls all the rest of the things your body does constantly to keep you alive that you don’t think about, like beating your heart.

The Autonomic Nervous System controls the glands and internal organs. The Sympathetic system is responsible for the arousal of this system for defensive action. The Parasympathetic system is responsible for calming this system, together they work to regulate your body’s internal functions to your everyday needs.

Central Nervous System: Spinal Cord 

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The spinal cord is an information highway connecting the brain and the peripheral nervous system. The spinal cord is responsible for various reflexes from sensation and pain such as yanking your hand away from a flame. These reflexes are usually caused by an interneuron connecting the sensory and motor neurons from a particular area.

Diagram of a reflex – a sensory and motor neuron connected by an interneuron in the spinal cord

Reflexes 

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While reflexes could happen in a headless warm body any interpretation of sensation or voluntary movement originates in the brain. Therefore, people who have had their spinal cord damaged or cut often cannot feel or move below that portion of their body, but they could have reflexive reactions.

Neural Networks A grain of sand size speck of your brain contains 100,000 neurons with a billion talking synapses. Neurons form connections with other neurons nearby them to make work groups that can carry out specific tasks, like learning the piano. Practice, repetition of using certain neuro-pathways strengthens them, and makes you better at that task.

The Brain (tools of discovery) 

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Lesion method – destroying a part of an animals brain and recording the results in behavior. Clinical Observation – observing someone who has had brain damage. Manipulation – stimulating part of the brain and using modern instruments to record the results, such as an EEG.

The Brain (tools of discovery) 

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Electroencephalogram (EEG) – records the overall electrical activity of neurons in the brain by recording the waves of energy that appear. Like studying a car by listening to the engine – not very precise. Computed tomography (CT or CAT scan) – using a series of x-rays a computer makes a map of your brain internally – used to see brain damage.

The Brain (tools of discovery) 

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Positron Emission Topography (PET scan) – by injecting users with radioactive glucose (food) this machine sees which areas of the brain are most active during certain stimuli by measuring how much food is being used by active neurons. Great for telling us what different parts of the brain do. Magnetic Resonance Imaging (MRI) – The MRI puts the brain in a strong magnetic field and then distorts very briefly atoms with a pulse of radio waves, by recording the movement of atoms you can create a computerized picture of the brain and of blood flow (active areas) into the brain.

The Brain: The Brainstem 

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The brainstem is the oldest part of the brain and is well developed in animals as well as humans. The bottom of the brainstem is called the medulla – it controls your breathing and heart rate The reticular formation helps organize sensation nerves to go different parts of the brain as well as affects arousal.

Thalamus 

Atop the brainstem is the brain’s primary switchboard for sensory neuron’s. The thalamus relay’s all senses except smell to the higher brain and transmits replies to the cerebellum and medulla. • Nearby the Cerebellum is in charge of coordination all voluntary movement and balance as well as some learning and memory functions

The Limbic System 

A system of neural structures right above the brain stem that influence emotions such as fear and aggression and basic drives like hunger and sex. Includes the hypothalamus hippocampus, and amygdala.

Limbic System 

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Amygdala – primarily influences aggression and fear Hypothalamus – directs several maintenance activies like eating, drinking, body temp., has links to emotion and influences the endocrine system via the pituitary gland. Around this organ on many animals is a distinct “reward center” that can be stimulated to make the animals feel pleasure.

Cerebral Cortex 

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The cerebral cortex is what people usually think of as “the brain.” It’s the wrinkled top of the Brain. The reason for the folds is that it increases surface area and allows for more neurons. Glial Cells – take care of neurons, they help guide their connections, give them nutrients, help cover axons with myelin sheaths, and they can clean up ions and excess neurotransmitters

4 Regions of the Brain 

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The Frontal Lobe speaking, movement, making plans, judgment. Temporal Lobes – auditory or hearing Occipital Lobes – Visual area Parietal – Sensory cortex

Functions of the Cortex 

While we may separate regions of the brain to help us study it we always have to keep in mind that the brain is a very complex organ. There is hardly ever just one region of the brain that is being used for a particular task, usually several areas at once are being used for even the most simple things, like typing.

Motor Cortex 

At the back of the frontal lobe is the motor cortex which is in charge of muscle movement

Sensory Cortex 

Right behind the Motor Cortex is the Sensory Cortex where your touch sensations are processed.

Plasticity 

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The brain has the amazing ability to reorganize itself. If brain damage occurs, neurons do not grow back, however neurons can change their function to allow the brain to repair itself. Thus if your middle finger were cut off, the fingers next to it would become more sensitive because that part of your brain that used to process sensation from the middle finger will now be used to process more sensation from the other fingers nearby.

The Divided Brain 

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Your brain is divided into two hemispheres. The left side of your brain controls the right side of your body and vice versa. The left side of your brain includes most speech areas while the right includes a lot of visual areas. Each side talks to the other side via the Corpus Callosum so they can work together.

Hemisphere Specializations 

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Perceptual tasks are performed more in the right side of the brain (recognizing faces, pictures, art, subtle interpretation) Speaking or calculating are preformed more in the left side of the brain. (recognizing words, Handedness is probably genetic, 95% of all humans are right-handed. Left handed people on average live 3 years shorter for unknown reasons

The Endocrine System 

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The Endocrine system is a system of communication via chemicals called hormones that it releases into the blood stream. Hormones are chemical messengers mostly manufactured by the endocrine glands that affect other parts of the body. Many hormones act just like neurotransmitters but are slower and have longer lasting effects.

• Adrenal Glands – Secrete epinephrine (adrenaline) and norepinephrine which arouse the body in times of stress • Pituitary Gland – the “master gland” under the influence of the hypothalamus it regulates growth and controls other endocrine glands. •Thyroid – affects metabolism •Parathyroid – affects calcium levels •Pancreas – regulates blood sugar levels •Ovary – secrets estrogen (female sex hormone) •Testis – secrets testosterone (male sex hormone)

Remember: Everything psychological is physiological!