Ch 3

Synapse

Structural Unit of info transmission between two nerve cells. it consists of presynatptic nerve terminal, synaptic cleft, a small area of the postsynaptic cell (usualy associated w a dendrite or region of the cell body) that receives the incoming signal

Second messenger

Substance that, when activated by signaling molecules bound to receptors in the cell membrane, will initiate biochemical processes within the cell.

Terminal Autoreceptors vs. Transporters

Terminal Autoreceptors modulate transmitter release but they dont transport the neurotransmitter. Transporters take up the transmitter from the synaptic cleft, but they are not autoreceptors.

Pituitary Gland

"Master Gland" endocrine gland secretes several hormones that control other glands in brain right under hypothalamus. made up of 2 separate glands w diff hormones that serve diff functions.

Structureof Metabotropic Receptors

1 Subunit

Structure of Ionotropic receptor

4 or 5 subunits that are assembled and then inserted inot the cell membrane

Adrenal Gland

Endocrine lie over each kidney.

Gases

Gaseous transmitters. non classical neurotransmitter. NO (nitric oxide(

Autoreceptor

a receptor on a particular neuron for the same neurotransmitter released by that neuron auto = self

1 protein subunit of metabotropic receptor

a single protein subunit that winds its way back and forth through the cell membrane 7 times. seven transmembrane domains (7-TM)

Mechanism of action of metabotropic receptor

activate G proteins in resonse to neurotransmitter or drug binding

the neurotransmitter molecule binds to a specific site on the receptor molecule which

activates teh receptor and produces a biochemical alteration in the recieving cell that may affect its excitability. (likelihood that cell will generate an AP)

Second messengers work by

activating specific enzymes called protein kinases within a cell

Active zones

area along teh axon terminal, near the postsynaptic cell, that is specialized for neurotransmitter realease. where exocytosis must occur. The vesicle "docks" at active zone

mechanism of action of ionotropic receptor

contain an intrinsic ion channel that opens in resonse to neurotransmiter or drug binding

Vesicle recycling

continuous release and reformation of vesicles. only happens w small vesicales w classical neurotransmittes

Receptor Subtypes

different varieties of receptors for the same transmitter are called receptor subtypes for that neurotransmitter.

Thyriod Gland

endocrine gland in throat. secretes thyroxine (T4) and triiodothyronine (T3)

Pineal gland

endocrine gland locatged over the brainstem and covered by the cerebral hemispheres. secretes the hormone melatonin

islets of Langerhans

endocrine gland w/in pancreas. secrete insulin and glucagon

Reducing a neurotransmitter inactivation -->

enhance action of neurotransmitter done by either: 1. levels of transmitter can be increased by blocking the enzyme involved in its breakdown 2.block transporters that reuptake the neurotransmitters out of the synaptic cleft

Enzymatic breakdown for neurotransmitter removal from synaptic cleft

enzymatic breakdown within or near the synaptic cleft. important for ACh.

Effector Enzymes

enzymes that are stimulated or inhibited by G proteins for Metabotropic receptors. they produce biochemical or physicological effects in the postsynaptic cell. most are involved in either the synthesis or the breakdown of small molecules called *second messengers*

Protein Kinases

enzymes that catalyze the phosphorylation of other proteins

How and where in nerve cell are neurotransmitters manufactored?

except for neuropeptides, transmitters are synathesized by enzymatic reactions taht can occur anywhere in the cell. typically, the enzymes required for producting a neurotransmitter are shipped out in large quantities to the axon terminals so the terminals are an important site for making transmitters. fast neuropeptides diff- lmade in cell body. slow to replenish them .

Tyrosine Kinase receptors

family of receptors that mediate neurotrophic factor signaling

speed of action for ionotropic receptors

fast

Ionotropic Receptor

fast acting receptor type comprised of several subunits that come together in the cell membrane. the receptor has an ion channel at its center which is regulated by neurotransmitters binding to specific sites on the receptor causing the channel to open. it may also be called a ligand-gated channel receptor.

insulin release is stimulated by

food intake

The phosphate groups added by kinases alter

funcitoning of the protein in some way

Glucocorticoids

hermone that belongs to class of molecules called steriods. main funct: to maintain normal blood glucose levels while helping to store excess glucose for future ues

Ovaries

hormone gland in females that secretes estrogen (female sex hromones) and progestins

glucagon

hormone secreted by islets of langerhans polypeptide hormone along w insulin, it regulates metabolic energy sources in the body

insulin

hormone secreted by islets of langerhans polypeptide hormone. regulates glucose and metabolic energy sources in teh body. regulates glucose uptake from the bloodstream into tissues and stimulates teh uptake of certain amino acids

melatonin

hormone secreted by pineal gland. control of rhythmic functions depending on the species humans -- sleep! sleep rhythms. take melatonin to make you sleepy

epinephrine

hormone that belongs to a group called catecholamines. it is screted by the chromaffin cells of the adrenal medulla, and it produces the "fight or flight" response by regulating teh diversion of energy and blood to msucles. also known as adrenaline.

T3 and T4

important for normal energy metabolism secreted in thyriod gland

A drug decreases levels of a neurotransmitter by

inhibiting a key enzyme needed for transmitter synthesis

Postsynatpic Cell

neuron at a synapse that receives a signal from teh presynaptic cell

Presynaptic Cell

neuron at a synapse that transmits a signal to the postsynaptic cell

norepinephrine

neurotransmitter that belongs to a group called catecholamines. functions as a hormone secreted by the chromafffin cells of the adrenal medulla. also known as noradrenaline.

are ionotropic receptors coupled to second messenger?

no

Neuropeptides

nonclassical neurotransmitter "peptides found in the nervous system"

Most neurotransmitter receptors are located

on the cell membrane (extraceullular)

Ca2+ signal comes in: Exocytosis

one or more proteins taht are sensitive to Ca2+ then cause the vesicle and axon terminal membranes to fuse --> allows versicle to open --> neurotransmitter is released into synaptic cleft

Adrenal Cortex

outer part of adrenal gland secretes hormones called glucocorticoids - we make cortisol

Desensitization

phemon which iontropic receptors can go thru. the channel remains closed even tho there may be ligand molecules bound ot the receptor. once this occurs, the channel must resensitize before it can be activated again

Volume Transmission

phenom characterized by teh diffusion of a chemical signal (neurotransmitter) through extracellular fluid to reach target cells at some distance from the point of release neuromodulators do this

Reuptake

proces that involves transport of neurotransmitters out of the synaptic cleft by the same cell that released them

Endocytosis

process that quickly retrieves the vesicle membrane from the terminal membrane.

psychoactive drugs can trigger

profound synaptic plasticity, especially under conditions of repeated drug exposure.

Transporters

proteins on cell membrane that remove neurotransmitters from the syanptic cleft.

Almost all neurotransmitter receptors are

proteins that are located on the plasma membrane of the cel.

Subunits

proteins that make up ionotropic receptor. are assembled to form the complete receptor before insertion into teh cell membrane. individ protein components that must jion in teh cell membrane to form a complete receptor.

Neurotrophic factors

proteins that stimulate the survival and growth of neurons during early development and are also involved in neuronal signaling.

Drugs can either increase or decrease the

rate of transmitter synthesis.

Priming step of exocytosis

readies the vesicle for exocytosis once it recieves the Ca2+ signal.

need to end the synaptic signal produced by each instanceo ftransmitter release so that the postsynaptic cell is free to respond to next release. this termination is accomplished by

removing neurotransmitter molecules from the synaptic cleft

Synaptic Vesicles

sac like structures located in teh axon terminal that are filled w molecules of neurotransmitter normally the source of neurotransmitter release

Testes

secrete male sex hormones called androgens (testosterone)

receptors

sensitive to to neurotransmitter signal on the membraneof teh postsynaptic cell. needed for chemical signalign to work

Presynaptic Facilitation

signaling by the presynaptic cell to increase neurotransmitter release by the axon terminal of the postsynaptic cell

Presynaptic Inhibition

signaling by the presynaptic cell to reduce neurotransmitter release by the axon terminal of the postsynaptic cell

Speed of action for metabotropic receptors

slow

G protein-coupled receptor

slow acting receptor type composed of a single large protein in the cell membrance that activates G proteins. AKA metabotropic receptor.

Synaptic Cleft

small gap, about 20 nm wide, btwn the presynaptic and postsynaptic cells gap must be traversed by neurotransmitter molecules after their release.

Endocrine Glands

specialized organ that secretes hormones into the bloodstream

G proteins

specific membrane proteins that are neceassary for neurotransmitter signlaing by metabotropic receptors. they operte by regulating ion channels or effector enzymes incolced in the synthesis or breakdown of second messengers, ultimately causing biochemical or physiological changes in the postsynaptic cell.

to respond to a given hormone, a target cell must possess

specific receptors for that hormone.

When a neuron fires an action potential, the depolarizing current

sweeps down teh length of teh axon and enters all of the axon terminals

Wave of depolarization effect within the terminals:

teh wave opens large numbers of voltage-sensitive calcium (Ca2+) channels, causing a rapid influx of Ca2+ ions into the terminals. the resulting increase in ca2+ concentration within the terminals is teh direct trigger for neurotransmitter release.

Neuromodulators

term used to describe substances that dont act exactly like typical neurotransmitters. the ymay regulate neurotransmitter activity or act at distant sites from their point of release. it may alter the action of a stanard neurotransmitter by enhancing, reducting, or prolonging the transmitter's effectiveness.

Neuromuscular Junction

the connection point btwn a neuron and a muscle. (instead of calling it a synapse)

if a drug blocks or inhibits the ability of the neurotransmitter to activate teh receptor,

the drug is called an antagonist

First messenger

the neurotransmitter or homrone

if the drug is a chemical precursor to the transmitter then

the rate of transmitter formation may be increased

Different method of cellular communication:

the release of chemical substances called hormones in to the bloodstream

epinephrine and norepinephrine in the bloodstream

these hormones mobilize glucose from the liber to provide immediate energy, and tehy also divet blood from the internal organs (ie the organs of digestion) to the muscles in case phsycial action is needed.

if a particular drug mimics the action of teh neurotransmitter in activating the receptor,

we say that the drug is an agonist at that receptor.

the characteristics of the ion channel controlled by an ionotropic receptor are the key factor in determining

whether that receptor excites the postsynaptic cell, inhibits the cell, or activates a second messenger system.

How a metabotropic receptor influences the postsynaptic cell depends on

which G protein(s) the receptor activates

second messenger

within the receiving cell. then carries out the biochemical change signaled by the first messenger.

Are metabotropic coupled to second messengers?

yes

Do almost all neurotransmitters have more than one kind of receptor?

yes!

chromaffin cells

cellsof the adrenal medulla. secrete hormones epinephrine and norepinephrine. both of which are monoamines.

2 glands that make up the pituitary gladn

1. Anterior Pituitary 2. Posterior Pituitary

Effect of receptor activation can be 2 things

1. Excitatory (incrase prob of action potiential) 2. Inhibitory (decrease prob of action potential)

2 types of autoreceptors

1. Terminal autoreceptors 2. Somatodentritic autoreceptors

3 Classical Neurotransmitter types:

1. amino acids 2. monoamines 3. acetylcholine

All G proteins work by 2 mechanisms

1. by stimulating or inhibiting the opening of ion channels in the cell membrane. 2. by stimulating or inhibiting certain enzymes in the cell membrane (effector enzymes)

2 other roles of testosterone:

1. during early development, this hormone acts within the brain to produce neural changes important for determine later gender based diffs in behavior. 2. later on, plays sig role in stimulating sex motivation in male and even in females

3 Different processes for neurotransmitter removal from synaptic cleft (neurotrans inactivation)

1. enzymatic breakdown 2. reuptake by axon terminal 3. uptake by nearby glial cells

Neurotransmitter receptors fall into 2 groups:

1. ionotropic receptors 2. metabotropic receptors

3 nonclassical neurotransmitters:

1. neuropeptides 2. lipids 3. gases

neurotransmitter release regulated by several diff mechanisms

1. rate of cell firing neuron rapid fire action potientials --> it will release muc hmore transmitter than when it is firing at a slow rate. 2. the probability of transmitter release from the termianl 3. presence of autoreceptors on axon terminals or cell bodies and dendrites

Acetylcholine

ACh classical neurotransmitter synthesized by teh cholingeric neurons

Synaptic Plasticity

Ability of synapses to change structurally (i.e. growth of new synapses or loss of existing ones) and functionally (i.e. increased or decreased strength of existing synapses) in the adult nervous system, synaptic plasticity is particularly important for learning and memory and for teh development of addiction following repeated exposure to abused drugs. axons can grow new terminals, dendrites can expand or contract their branches, and or grian or lose spoines. synapes can be created or lost.

Hormones

Chemical substance secreted by endocrine glands into the bloodstream, where it travels to target locations in the body

Axosomatic Synapses

Junction used for communication btwn a nerve terminal and a nerve cell body axon terminal + soma (nerve cell body)

Exocytosis

Process by which the synaptic vesicles (sacs that contian the neurotransmitters) make their way past the membrane of axon terminal and into the synaptic cleft. method by which vesicles release substances and neurotransmitters, characterized by fusion of the vesicle and the cell membrane, specifically the axon terminal membrane in teh case of neurotransmitters. the vesicle opens toward the synaptic cleft allowing neurotransmitter molecules to diffuse out. a fusion of vesicle membrance w the membrane of the axon terminal- which exposes the inside of the vesicle to the outside of the cell. --> vesicle is opened --> its transmitter molecules are allowed to diffuse into the synaptic cleft.

Gonads

Sex organs. ovaries for girls and testes for boys

Metabotropic receptors

Slow acting receptor type composed of a single large protein in the cell membrane that activates G proteins. It may also be called a G protein - coupled receptor.

Heteroreceptors

axon terminals may have receptors for other transmitters released at axoaxonal synapses. also differ from autoreceptors in that they may either enhance or reduce the amount of transmitter being released from the axon terminal.

second-messenger systems

biochemical pathways that use second messengers to mediate intercellular signaling

Hormones use various trypes of receptors -

both extracellular and intracellular

Monoamines

can be neurotransmitter classical each possesses a single (mono) amine group.

Amino acids

can be neurotransmitters. individ building blocks of proteins, play other metabolic roles as well. classicla

Lipids

can be nonclassical neurotransmitter fatty substance anandamide

Docking step of exocytosis

carried out by a cluster of proteins

Phosphorylate

catalyze the addition of one or more phosphate gropus (-PO42-) to the molecule molecule is a protein

adrenal medulla

inner part of adrenal gland. derived from nervous system tissue. receives input from the preganglionic fibers of the sympathetic nervous system.

Axodendritic Synapses

junction used for communication between the axon terminal of a presynaptic of a presynaptic neuron and a dendrite of a postsynaptic neuron most common synapses in the brain dendrite + axon terminal

Axoaxonic Synapses

junction used for communication btwn the axon terminals of two neurons, permitting the presynapttic cell to control neurotransmitter release from the postysynaptic cell at the terminals one axon synapsing on terminal of another axon. lets presynatpic cell to alter neurotrans release from teh postsynaptic cell directly at the axon terminal.s -presynatptic inhibition -presynaptic faciliation

terminal Autoreceptors

located on axon terminals. when activated by neurotransmitter they inhibit neurotransmitter release.

Somatodentritic Autorecptors

located on dendrites or on the cell body slow the rate of cell firing when activated which causes less neurotransmitter release bc fewer action potentials reach the axon terminals to stimulate exocytosis

Tyrosine kinase receptors and neurotrophic factors they serve gen participate more in regulation of

long term changes in gene expression and neuronal functioning than in rapid synaptic event sthat determine the rate of cell firing.