Chemical Substance and Behavior Test 1

Structure and Function of the nervous system

Neurons

The principle function is to transmit information in the form of electrical signaling over long distances

Glial Cells

Glue that holds the whole system together. Provide metabolic support, protection, and insolation for neurons

Schwann Cells

Produce myelin sheath on the neuronal axons in the peripheral nervous system

Oligodendroglia

Produce myelin sheath on the neuronal axons in the central nervous system

Soma “Cell body”

Possess nucleus. Metabolic center of the neuron. Synthesizes proteins that are needed for growth and maintenance

Dendrites

Receive as much information from other cells

Axon

Designed to gather the information from the dendrites and continue the message to the other group of cells

Axon Hillock

Where action potential is first generated

Axon Terminals

Bottom of the neuron where synaptic vesicles are containted

Synaptic Vesicles

Sac-like Structures located in the axon terminal that are filled with molecules of neurotransmitter

Neurotransmitters

Chemical substances packed in synaptic vesicles and released by neurons to communicate across the synapse with other neurons, muscle cells, secretory cells, or cells comprising of other tissues/organs. Exert their influence by binding to receptors

Presynaptic

The cell releasing the transmitter. The axon terminal

Postsynaptic

The cell receiving the transmitter. Dendrites that receive the information contains receptors

Synaptic Cleft

The space between neurons at a nerve synapse across which a nerve impulse is transmitted by a neurotransmitter

Resting Membrane Potential

Membrane potential when the neuron is not being disturbed -70mv

Myelin

The fat insulating the neuron around the axon created by layers of glial cells (is very conductive)

Extracellular Fluid

salty fluid that takes oxygen, nutrients and drugs, into which they secrete metabolic waste products that reach the blood and are filtered out by the kidneys

Concentration Gradience (Diffusion)

Molecules move from high concentration to low concentration

Electrical Gradients (Electrostatic Pressure)

Opposite charges attract and alike charges repel

Equilibrium Potential

When inward electrical gradient and outward concentration gradience are balanced

Polarization

The separation of electrical charge, the inside of the neuron is more negative than the outside

Depolarization

Change in the membrane potential that making the inside of the cell more positive, increasing the likelihood that the cell will have action potential

Repolarization

Change in membrane potential that returns it to a negative value just after the depolarization phase of an action potential has changed the membrane potential to a positive value

By temporary changes in ion movement into and out of the neuron. (Channels)

How is electrical signal produced?

Separation of Charge

Membrane potential is created by a

Cell Membrane

Two Layers of fat imbedded with protein

The permeability of some ions to the membrane or the number of ion channels present

What Determines Resting Membrane Potential?

Sodium and Chloride

What is more concentrated outside the cell?

Potassium and Organic Anions

What is more concentrated inside the cell?

They want to go from low to high concentration and attract to the opposite charge

What determines if a particular ion will move in or out of the cell?

The membrane is not permeable to sodium.

 Both diffusion and electrostatic pressure are pulling Na+ in the cell, yet it remains in its highest concentration outside the cell.  How?

Na and K pump

Controls when potassium and sodium are pumped in and out of the cell. For every three Na ions leaving the cell two K ions go in

Membrane Permeability

Ions and bacteria cannot pass through

Action Potential (Nerve Impulse)

A change in membrane permeability that allows sodium to pass through. Occurs in 1-2 milliseconds

Voltage-Gated Ion Channels

Opens to allow cell to become permeable to sodium. The action potential occurs from and influx of sodium. Time sensitive and close automatically

Threshold

Opening of voltage sensitive sodium channels. 50mv for action potential to fire

1-2 milliseconds

How long does action potential last?

Basic Law of Action Potential 1

All or None. Either it goes through the channel and fires, or it does not.

Basic Law of Action Potential 2

The signal is always depolarization. The inside of the cell gets positive

Basic Law of Action Potential 3

Action potentials do not vary and are always consistent

Ion

Charged particles

Force

Capacity to work or cause change

Intensity and Speed of Action Potential are Created by

Frequency and time between action potentials

Frequency

The Number of action potentials

Passive Conductance

Small localized short-lived change in voltage across the cell membrane following the opening of ligand gated channels

Active Conductance

Movement of the signal down the axon by doing action potentials

Saltatory Conductance

Mode of action potential conduction along a myelinated neuron characterized by jumps from one node of ranvier to the next

Nodes of Ranvier

Gaps in the myelin sheath that expose the axon to extracellular fluid. Cites where action potential is regenerated during conduction of the electrical signal along the length of the axon

Two Advantages of Saltatory Conduction

Pumps are only needed at nodes of ranvier and it is very fast at a speed of 150 ms

Neural Integration

Referring to the net sum of all input on the postsynaptic membrane

Excitatory Postsynaptic Potentials

Depolarizations of a postsynaptic neuron that result from neurotransmitters binding to specific receptors that open ion channels. They move the membrane closer to the threshold for firing. Meaning it allows sodium in so the neuron activates

Inhibitory Postsynaptic Potentials

Hyper-polarization, the cell membrane goes away from zero or it is neutralizing potassium and chloride

Spatial Summation

A number of neurons that are converging in a small space on a neuron

Temporal Summation

A lot of signals coming in in a close amount of time

Exocytosis

Release of transmitter

Synaptic Vesicles, release of transmitters, regulation of calcium

What are the presynaptic characteristics?

Receptors are the lock and neurotransmitter is the key

What are the postsynaptic characteristics?

Ionotropic and Metabotropic

Two types of postsynaptic receptors?

Receptors

Protein molecules. Determine if it is EPSP or IPSP.

Ionotropic

They mediate ion channels. As long as neurotransmitter is present, the Ion stays open, once they bind the channel opens

Metabotropic

Involved in protein synthesis. How we create memories

Re-uptake

Protein transporter on presynaptic membrane, take neurotransmitter back up into the cell to be recycled and reused

Enzymatic Deactivation

Break down receptor so it does not work anymore

Autoreceptors

Located presynaptically, do not produce membrane potentials, function as the feed back system

Axo-dendritic, Axo-somatic, Axo-axonic, Dendro-dendritic

Four Types of Synaptic Connections?

Criteria for Neurotransmitters

\*Substance exists in presynaptic axon terminals

\*Is synthesized in presynaptic cells

\*Is released when action potentials reach axon terminals

\*Receptors for the substance exist on postsynaptic membrane

\*When experimentally applied , substance produce changes in postsynaptic cells

\*Blocking substance release prevents change in postsynaptic cell

Ionotropic Recepters

Change shape

Metabotropic Receptors

Alter chemical reactions in the target cell

Ligand

A substance that binds to receptor molecules

Agonist

Any substance that facilitates or enhances synaptic transmission

Antagonist

Any substance that disrupts, inhibits, or blocks synaptic transmission

Endogenous

From Within the body for example - endorphines, enkephalins, and dynorphins

Exogenous

From Without the body - morphine and codine

Neuromuscular Junction

Where neurons meet muscle

Nucleus

Cluster of cells bodies in the central nervous system

Ganglia

Cells in the peripheral nervous system

Nervous System

Contains the central nervous system and the peripheral nervous system

Central Nervous System

Made up of the brain and the spinal cord

Acetylcholine

Is an antagonist

Synthesis of Acetylcholine

acetalCoA = Choline → Acetylcholine

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Choline Acetyltrousferase (Rate Limiting)

Rate Limiting Step

Part of the reaction that determines the rate of synthesis

Autonomic Nervous System

In the PNS. Controls involuntary actions (breathing). Contains Sympathetic Nervous system and the Parasympathetic nervous system

Basal Forebrain

Nucleus and Ganglia

Peripheral Nervous System

Contains the somatic, cranial nerves (12), and the autonomic nervous system

Sympathetic Nervous System

Where fight or flight takes place

Fight or Flight

The reaction our body has when trying to survive. Brain Blood drains from stomach into the brain and muscles, acetylcholine decreases

Parasympathetic Nervous System

Where rest and digest takes place

Rest and Digest

When the blood from the brain drains to the stomach so we can digest food. Acetylcholine increases. Heart rate decreases.

Nicotinic

Caused by nicotine in the neuromuscular junctions. contracts the muscle and finally results in relaxation (ACh Receptor)

Muscarinic

poisonous mushroom toxin. In our brain and internal organs. (An ACh Receptor)

Two Types of Monoamines

Catecholamines and Indolamines

Examples of Catecholamines

Dopamine

Norepinephrine

Epinephrine

Examples of Indolamines

Serotonin

Melatonin

Blood Brain Barrier

Barrier between blood in the brain and blood in the circulatory system. Molecules have to be small enough to get through the barrier. IE: Dopa is small enough and treats parkinsons

Area Postrea

Vomit out toxins and it is weak

Tyrosine Hydroxylase

Rate-limiting enzyme

Tyrosine

Amino Acid

Tryptophan

Amino Acid

Tryptophan Hydroxylase

Rate-Limiting Enzyme

Monoamine Oxidase

Compound that breaks down monoamines and indolamines