Neuroscience and Behavior

Chapter 2: part 1

Everything psychological is simultaneously……

biological.

Neuroscience

Deals with the structure and function of neurons, nerves, and nervous tissue.

Especially focuses on their relationship to behavior and learning.

Fundamental questions we will be looking at in this module:

How does the brain work? How does our brain organize itself? How does our brain communicate within

itself?

How does the brain process the information we need to:

Recognize our best friend. Play a musical instrument. See color. Identify our first memory. Shoot a basketball. Write a paper.

How does brain chemistry factor in for things like: depression, aggression, multiple sclerosis, Parkinson’s disease, addictions, or sexual attraction?

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Overview of the Nervous System (Figure 2.1)

The Neuron

A nerve cell that makes up the nervous system and that receives and sends messages within that system.

The Neuron

orsoma

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LO 2.1 What are the nervous system, neurons and nerves

Nerves

Bundles of axons coated in myelin that travel together through the body.

(Similar to a telephone cable made up of thousands of small wires.)

Glial Cells:

Grey fatty cells in the brain that… provide support for the neurons to grow on and around deliver nutrients to neurons produce myelin to coat axons clean up waste products and dead neurons, influence

information processing during prenatal development, influence the generation of new

neurons.

Brain is made up off 10% neurons, 90% glial cells.

Action Potential: a brief electrical charge that travels down an axon.

How do neurons communicate?

Threshold: The level of stimulation required to trigger a neural impulse.

Synapse: The junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron. The tiny gap of this junction is call the synaptic gap.

Synaptic vesicle

Synaptic knob

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Neurotransmitters

Chemical messengers that traverse the synaptic gaps between neurons.

When released by the sending neuron, neurotransmitters travel across the synaptic gap and bind to receptor sites on the receiving neuron, thereby influencing whether that neuron will generate a neural impulse.

Neurotransmitters…

Different neurons will produce only certain kinds of neurotransmitters as well as receive only certain kinds of neurotransmitters.

Outside chemicals introduced into the human system can substitute, mimic or block these neurotransmitters.

Cleaning up the Synapse

Reuptake - process by which neurotransmitters are taken back into the synaptic vesicles.

Enzyme - a complex protein that is manufactured by cells.– One type specifically breaks up acetylcholine

because muscle activity needs to happen rapidly, so reuptake would be too slow.

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How do neurotransmitters affect behavior?

All neural pathways use neurotransmitters, therefore neurotransmitters play a part in all behaviors and mental processes in some way.

Acetylcholine

Enables muscle action, learning, and memory. The major neurotransmitter controlling muscles.

With Alzheimer’s disease, ACH-producing neurons deteriorate.

In Parkinson’s disease, ACH is overproduced, contributing to tremors and stiffness.

Dopamine

Influences movement, learning, attention, and emotion.

Associated with the pleasure system of the brain, providing feelings of enjoyment.

Dopamine….

Drugs of abuse (alcohol, cocaine) alter the release of dopamine.

Amphetamines cause the over release of dopamine from the vesicles.

Other drugs mimic dopamine and cause rush of pleasure.

Dopamine and addiction…

The body adjusts to the higher level of dopamine by shutting down receptor sites.

Even when the chemicals causing the high dopamine levels are no longer in the system, the receptor sites for the dopamine have been reduced.

Now, normal levels of dopamine can’t fire the neurons effectively, because there aren’t sufficient numbers of dopamine receptors!

Symptoms of Dopamine deficiency

Reduced ability to feel pleasure Flat, bored, apathetic and low enthusiasm Depressed Low drive and motivation Difficulty getting through a task even when interesting Difficulty paying attention and concentrating Slowed thinking and/or slow to learn new ideas Low libido or impotence Mentally fatigued easily and physically fatigued easily

Dopamine and addictions….

In order to feel better again, people return to their substance of choice (or another) which will increase coveted dopamine levels back to high levels again.

People may need increasing amounts of their drug just to feel normal!

Dopamine Pathways

Dopamine pathways are involved with diseases like

schizophrenia and Parkinson’s

disease.From Mapping the Mind, Rita Carter, © 1989 University of California Press

Dopamine and disease

Excess dopamine receptor activity is linked to schizophrenia.

Decreased dopamine is also linked to Parkinson’s disease.

Serotonin

Affects mood, hunger, sleep, and arousal. Undersupply is linked to depression and anxiety. Many drugs available to help raise the serotonin

levels. SSRI – Selective serotonin reuptake inhibitors.

These drugs allow serotonin to remain in the synaptic gap longer and help the neurons to function more efficiently.

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Serotonin

Serotonin pathways are involved with mood regulation.

From Mapping the Mind, Rita Carter, © 1989 University of California Press

Two types of chemicals

1. Agonists: chemical substances that mimic or enhance the effects of a neurotransmitter on the receptor sites of the next cell increasing or decreasing the activity at that cell.

--nicotine, cocaine, certain pain killers, MSG.

2. Antagonists: chemical substances that block or reduce a cell’s response to the action of other chemicals or neurotransmitters.

---Alcohol, caffeine, some kinds of anesthesia. Botulin poisoning.

The Nervous System

Central Nervous System

Central nervous system (CNS) - part of the nervous system consisting of the brain and spinal cord.– Spinal cord: a long bundle of neurons that carries

messages to and from the body to the brain that is responsible for very fast, lifesaving reflexes.

LO 2.3 Brain and spinal cord

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The Reflex Arc: Three Types of Neurons

Sensory neuron - a neuron that carries information from the senses to the central nervous system.

– Also called afferent neuron. Motor neuron - a neuron that carries messages from the

central nervous system to the muscles of the body.– Also called efferent neuron.

Interneuron - a neuron found in the center of the spinal cord that receives information from the sensory neurons and sends commands to the muscles through the motor neurons.

– Interneurons also make up the bulk of the neurons in the brain.

Neural Networks

Interconnected neural cells. With experience, networks can learn, as feedback strengthens or inhibits connections that produce certain results.

Peripheral Nervous System

Peripheral nervous system (PNS) - all nerves and neurons that are not contained in the brain and spinal cord but that run through the body itself.

Peripheral Nervous System - 2 parts

1. Somatic –voluntary

2. Autonomic – involuntary, self-regulated

(i.e. eye blinking, stomach digesting breakfast, breathing, etc…)

Autonomic Nervous System - 2 parts

Sympathetic (arousing, fight-or-flight system): Part of the ANS that is responsible for reacting to stressful events and bodily arousal.

Parasympathetic (calming): Part of the ANS that restores the body to normal functioning after arousal and is responsible for the day-to-day functioning of the organs and glands.

The Endocrine System

Endocrine Glands secrete chemicals called hormones directly into the bloodstream.

Hormones: chemicals released into the bloodstream by endocrine glands.

Hormones

Pituitary gland – growth hormones.– Pea-size structure in the brain.– THE MASTER GLAND — helps to regulate all

other endocrine glands. Adrenal gland – adrenaline- increase heart rate,

BP, and blood sugar. Pancreas gland – insulin – regulate blood sugar Pineal gland – located near the base of the cerebrum;

secretes melatonin for the sleep-wake cycle.

The Endocrine System—glands producing hormones and other chemicals.

The master gland