Chapter 4: The Nervous System

What are the two main ways in which drugs can interact with neurotransmitter systems? (hint: on/between neurons)

1. Alter neurotransmitter availability in the synapse (action on: synthesis, storage, release, uptake, or metabolism) 2. Direct action on the receptor (agonist: activate receptor or antagonist: prevent activation of receptor)

Life Cycle of a Neurotransmitter

1. precursors found in the blood (based on diet) 2. uptake of precursors by the cell 3. synthesis (enzymes are the frame for assembly) 4. storage (in vesicles within the axon terminal) 5. release (into synapse by action potential) 6. binding (receptors on the postsynaptic neuron) 7. metabolism or reuptake

Agonist vs. Antagonist

Agonist: works with a neurotransmitter to activate receptors by mimicking the neurotransmitter chemically Antagonist: works against the neurotransmitter by preventing activation of the receptor, even in the presence of the neurotransmitter

Describe the process of neurotransmitter release and receptor interaction.

An action potential allows release of neurotransmitters from the axon terminal. The neurotransmitters then float around in the synapse until they fit into a receptor, are metabolized, or are reabsorbed by the axon terminal.

Pathways of Serotonin

Arises from RAPHE NUCLEI in brainstem -pathways to multiple areas of the brain -may have role in impulsivity, aggression, food & alcohol intake control, and depression -Hallucinogens influence these pathways -inhibitory/excitatory

Pathways of Norepinephrine

Arises from the LOCUS CERULEUS in brainstem -pathways to multiple areas of brain -plays role in appetite -regulates arousal and attentiveness

Pathways of Acetylcholine

Arises from the NUCLEUS BASALIS -projects throughout the cerebral cortex -involved in Alzheimer's disease & memory fxn -inhibitory/excitatory

Name the nervous systems:

Autonomic Central Somatic

Cerebellum

Balance and coordination *Automatic tasks [classical conditioning]

Central nervous system

Brain & spinal cord Functions: -integration of info -learning and memory -coordination of activity

PET and MRI are two examples of what technology?

Brain imaging

PET Scan

Brain imaging Benefit: direct measure of brain activity Limitation: injection of radioactive materials; no info about brain structures

fMRI

Brain imaging Benefits: real-time changes in blood flow; non-invasive Limitations: no info about brain anatomy

Enzyme Degregation

Breaking down of neurotransmitter into metabolites (these are what are tested by drug tests)

Somatic nervous system:

Bring sensory info into the CNS Puts motor information back out Voluntary action ACETYLCHOLINE is the neurotransmitter at the neuromuscular jxn.

Draw a neuron:

Contains: Nucleus Cell body Dendrites Myelin sheath Axon Axon terminals Direction of electrical movement

Hypothalamus

Controls homeostasis -releases neurotransmitters and hormones

Sympathetic branch (ANS)

Fight of flight reaction -norepinephrine increases HR

Glutamate

Found in most regions of the brain -excitatory fxn

GABA

Found in most regions of the brain -inhibitory fxn

Endorphins

Found throughout he brain -opioid-like naturally occurring chemicals that play role in pain relief & other fxns -inhibitory fxn

Chemical theories of behavior

Four humors Yin and yang Monoamine theory of mood: too little activity in monoamine system (dopamine, serotonin, norepinephrine) can cause depression and too much can cause mania, NONE HAVE SUFFICIENT SCIENTIFIC SUPPORT

Action potential

From a resting potential, the ion channels open allowing charged particles to move inside the cell. As a result, neurotransmitters are released. (Note: blocking the ion channels stops the action potential from taking place)

What neurotransmitter seems to have only inhibitory receptors?

GABA

Glia

Gives brain firmness Brings in nutrients Eliminates waste Produces myelin Communicates with other glia cells and neurons forms BLOOD BRAIN BARRIER

Autonomic nervous system

Involuntary functions of the body -Sympathetic branch -Parasympathetic branch Many psychoactive drugs affect the ANS

What is the proposed role of the mesolimbic dopamine system in drug dependence?

It is proposed to act as a reward system for drug use, reinforcing the positive feedback of use.

Alzheimer's disease produces a loss of which neurotransmitter from which brain structure?

Loss of acetylcholine in the nucleus basalis [within forebrain]

Difference in Neurotransmitters and Hormones

N travels a shorts distance through the synapse to communicate H travels long distance through bloodstream to communicate

Give some examples of opposing actions of the sympathetic and parasympathetic branches of the autonomic nervous systems. What is the neurotransmitter for each branch?

Norepinephrine from the SB increases HR, while acetylcholine from the PB decreases HR.

What is the function of the basal ganglia, and which neurotransmitter is involved?

One function is the maintain muscle tone. Dopamine is the neurotransmitter involved.

Neuron

Primary element of nervous system that analyzes and transmits info Four parts: 1. Cell body - contains nucleus, etc. 2. Dendrites - contains receptors that activate or inhibit neuron based on signal received 3. Axon - conducts action potential 4. Axon terminals - contains synaptic vesicles which store neurotransmitters

Pituitary gland

Sends signals via neurons to release hormones

What are some examples of homeostasis in the human body?

The body shivering, sweating, or altering blood flow to the skin in order to maintain the right temperature

What are the similarities and differences between glia and neurons?

They are both major types of cells in the brain that have some communicative function, however the neuron's main function is to analyze and pass signals, while the glia's main functions are to give firmness, bring in nutrients, eliminate waste, and form the insulatory coating around the neurons called myelin

After a neurotransmitter is synthesized , where is it stored while awaiting release?

Vesicles within the axon terminal

Resting potential

When a neuron is hyperpolarized (more negative)

Mesolimbic Dopamine Pathway

[FRONTAL LOBE] runs from the VENTRAL TEGMENTAL AREA to the NUCLEUS ACCUMBENS -proposed to mediate psychotic behavior -possible "rewarding" property of drug use

Nigrostriatal Dopamine Pathway

[MIDBRAIN] runs from SUBSTANTIA NIGRA to STRIATUM -substantial cell loss along pathway leads to Parkinson's -inhibitory/excitatory

Medulla

affected indirectly through the midbrain

Parasympathetic branch (ANS)

has effects associated with relaxed psychological state -acetylcholine slows HR

Pons

helps 2 halves of medulla communicate (sleep/arousal)