Discussion Paper

Gillianrich

Hart16e_ppt_ch04-14.ppt

Home >Psychology homework help >Discussion Paper

Chapter 4

The Nervous System

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Humans maintain their internal environment within certain limits

Examples: body temperature, water content, glucose concentrations, etc

Psychoactive drugs influence homeostasis

Alcohol inhibits vasopressin release (antidiuretic hormone)

Thus, after a drink more urine is produced

Compared to light drinkers, heavy drinkers produce less urine after a drink

During alcohol withdrawal, heavy drinkers exhibit increased vasopressin release

Homeostasis

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Two major types of cells in the nervous system

Neurons (or nerve cells)

Glia (or glial cells)

Components of the Nervous System

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Major function:

primary elements of the nervous system that analyze and transmit information

Four defined regions:

Cell body

Contains the nucleus and other sustaining substances

Dendrites

Contains receptors which respond to chemical signals

Psychoactive drugs activate or inhibit neuron based on type of receptor

Axon

Conducts the action potential

Axon terminals

Contains synaptic vesicles which store neurotransmitters

Neurons

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Neuron Schematic

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Major functions:

Provide firmness and structure to the brain

Get nutrients into the system

Eliminate waste

Form myelin

Communicate with other glia & neurons

Glia also create the blood-brain barrier

Protects the brain from toxic chemicals

Psychoactive drug molecules must be able to pass the barrier

Glia

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Action potential

A brief electrical signal transmitted along the axon

Brief chain of events:

Resting potential is caused by uneven distribution of ions

The neuron is hyperpolarized

Ion channels open allowing electrically charged particles to move inside the cell

As a result, the neuron may become depolarized

“all-or-none” action potential occurs

Note: Blocking ion channels prevents the action potential and disrupts neuronal communication

Neurotransmitters are released

Neurotransmission

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Somatic nervous system

Sensory information into the CNS

Motor information back out

Voluntary actions

Autonomic nervous system (ANS)

Sympathetic branch

Parasympathetic branch

Involuntary functions of the body

Central nervous system (CNS)

Brain

Spinal cord

The Nervous System(s)

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Controls voluntary actions

Carries sensory information into the central nervous system

Carries motor (movement) information back out to the peripheral nerves

Acetylcholine is the neurotransmitter at neuromuscular junctions

Somatic Nervous System

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Monitors and controls the body’s internal environment and involuntary functions

Examples: heart rate and blood pressure

Many psychoactive drugs affect the brain and the autonomic nervous system

Two branches often act in opposition

Sympathetic branch

Example: norepinephrine is involved in increased heart rate

“Fight or flight”

Parasympathetic branch

Example: acetylcholine is involved in decreased heart rate

Autonomic Nervous System

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Consists of the brain and the spinal cord

Has many functions:

Integration of information

Learning and memory

Coordination of activity

Central Nervous System

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Dopamine

Mesolimbic dopamine pathway

From the ventral tegmental area to the nucleus accumbens

Proposed to mediate some psychotic behavior

Possible component of the “rewarding” properties of drugs

Nigrostriatal dopamine pathway

From the substantia nigra to the striatum

Substantial cell loss leads to Parkinson’s Disease

Chemical Pathways in the Brain

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Dopamine Pathways

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Norepinephrine

Multiple pathways:

Arising from the locus ceruleus in the brainstem and projecting to multiple brain areas

Regulates level of arousal and attentiveness

Plays a role in initiation of food intake (appetite)

Chemical Pathways in the Brain

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Serotonin

Multiple pathways:

Arising from the brainstem raphe nuclei and projecting to multiple brain areas

May have a role in impulsivity, aggression, depression, control of food and alcohol intake

Hallucinogenic drugs influence serotonin pathways

Example: LSD

Chemical Pathways in the Brain

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Acetylcholine

Arising from nucleus basalis and projecting widely throughout the cerebral cortex

Involved in Alzheimer’s disease and learning and memory

Endorphins

Found throughout the brain

Naturally occurring opioid-like chemicals

Play a role in pain relief and other functions

Chemical Pathways in the Brain

or distribution without the prior written consent of McGraw-Hill Education.

4-*

GABA (Gamma-amino butyric acid)

Found in most regions of the brain

Inhibitory neurotransmitter

Glutamate

Found in most regions of the brain

Excitatory neurotransmitter

Chemical Pathways in the Brain

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Common Neurotransmitters

or distribution without the prior written consent of McGraw-Hill Education.

Neurotransmitter

Type of effect

CNS changes

Drugs of abuse

dopamine

GABA

serotonin

acetylcholine

endorphins

inhibitory-

excitatory

inhibitory

excitatory-

inhibitory

excitatory-

inhibitory

euphoria

agitation

paranoia

sedation

relaxation

drowsiness

depression

sleep

relaxation

sedation

mild euphoria

excitation

insomnia

mild euphoria

block pain

slow respiration

amphetamines

cocaine

alcohol

barbiturates

LSD

nicotine

opioids

4-*

Major Brain Structures

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Neurotransmitter precursors are found circulating in the blood supply

Uptake:

Selected precursors are taken up by cells

Life Cycle of a Neurotransmitter

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Synthesis:

Precursors are synthesized into neurotransmitters through the action of enzymes

Schematic representation of the action of a synthetic enzyme.

Life Cycle of a Neurotransmitter

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Synthesis

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Storage:

Neurotransmitters are stored in small vesicles

Release:

When the action potential arrives, neurotransmitters are released into the synapse

Binding:

Released neurotransmitters bind with receptors on the membrane of the postsynaptic neuron

Neurotransmitters may have excitatory or inhibitory effects

Life Cycle of a Neurotransmitter

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Metabolism:

Once a signal has been sent, neurotransmitters are removed from the synapse; may return or be metabolized

Schematic representation of the action of a metabolic enzyme.

Life Cycle of a Neurotransmitter

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Alter neurotransmitter availability in the synapse

Through actions on: synthesis, storage, release, uptake, metabolism

Example: Many antidepressants block the reuptake of dopamine, serotonin and/or norepinephrine

Direct action on the receptor

Drug as agonist

Mimic neurotransmitters by activating the receptor

Drug as antagonist

Occupy neurotransmitter and prevent receptor activation

Examples of Drug Actions

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Many attempts to explain normal variations in behavior in terms of changes in brain chemistry

Historical precedents

Greek physician Hippocrates and the four humors

Chinese philosophy—yin and yang

Chemical Theories of Behavior

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Monoamine theory of mood

Dopamine, serotonin, noreprinephrine

Too little activity in monoamine systems can cause depression

Too much can cause mania

No single biochemical theory of mood or drug dependence has achieved sufficient experimental support

Chemical Theories of Behavior

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Brain Imaging Techniques: PET

Positron Emission Tomography

Benefit

Direct measure of brain activity

Limitations

Injection of radioactive materials

No information about brain structure

or distribution without the prior written consent of McGraw-Hill Education.

4-*

Brain Imaging Techniques: fMRI

Functional Magnetic Resonance Imaging

Benefits

Real-time changes in brain blood flow

Non-invasive

Limitation

No information about brain anatomy

or distribution without the prior written consent of McGraw-Hill Education.

Image source: National Cancer Institute Visuals Online