Midterm Exam Flashcards
Why is a cell can depolarize ?
Because the cell receives signal from other cells.
What is the concept that is happening at +40 mV when sodium ions rushing in equals potassium ions rushing out of the cell ?
Equilibrium potential
On which ion those action potentials depends on and why ?
Sodium because at -40 mV, the voltage-gated sodium channels open.
The resting membrane potential is dependent of which ion and why ?
Potassium because at rest, it is only potassium that goes in and out of the cell (the other doors are locked)
What are the two kinds of refractory period and describe them ?
Absolute refractory period: Complete insensitivity to stimuli (no more action potential).
Relative refractory period: A period of reduced sensitivity during which only strong stimulation produces an action potential.
The conduction velocity in the axon varies with what ?
The diameter of the axon and the myelin sheathing
myelination is better than bigger diameter
Where does the action potential is taking place and is regenerated ?
Nodes of Ranvier
How is the phenomena named in which action potential flies through the other node of Ranvier ?
Saltatory conduction
Why does a neuron generated action potentials ?
To communicate with other neurons.
True or false.
At the axon terminal, the chemical signal of the action potential is usually converted into a electrical signal (neurotransmitter).
False.
At the axon terminal, the electrical signal of the action potential is usually converted into a chemical signal (neurotransmitter).
How does the electrical signal is converted into a chemical signal ? (Synaptic Transmission)
When the action potential arrives in the axon terminal, it depolarize the region and then voltage-gated calcium channels open and calcium (Ca2+) rushing in by diffusion (because there are less calcium inside the cell than outside).
Because of the influx of calcium, synaptic vesicles migrates to the presynaptic membrane.
With v-SNAREs that are attached to the vesicle and t-SNAREs attached to the presynaptic membrane, the vesicle docks to the presynaptic membrane promoting exocytosis, the fusion of vesicles with the presynaptic membrane, which releases transmitter into the cleft.
Transmitter molecules cross the cleft to bind to special receptor molecules in the postsynaptic membrane, leading to the opening of ion channels in the postsynaptic membrane.
This ion flow creates a local EPSP or IPSP in the postsynaptic neuron.
Synaptic transmitter is either degraded by enzymes or removed from the synaptic cleft by transports.
Synaptic transmitter may also activate presynaptic autoreceptors, regulating future transmitter release.
What are the two types of release ?
Kiss and run
Full release
What are the two prompt cessation of transmitter ?
Degradation: transmitter is broken down by a special enzyme (acetylcholinesterase)
Reuptake: transmitter is taken up into the presynaptic cell via transport
What is the role of autoreceptors ?
They inform the presynaptic cell about the net concentration of neurotransmitters in the cleft.
The message comes from the neurotransmitters that didn’t cross the cleft.
What are the two types of ligands ?
Endogenous ligand: neurotransmitters or hormones
Exogenous ligand: drugs, toxins from outside the body
When activated by a neurotransmitter, ionotropic receptors may… ?
Change shape
When activated by a neurotransmitter, metabotropic receptors may… ?
Alter chemical reactions in the target cell
What are the two types of postsynaptic potentials ?
Excitatory postsynaptic potential (EPSP)
Inhibitory postsynaptic potential (IPSP)
*work the same but have opposite effects on postsynaptic neurons
In which case a postsynaptic neuron will generate an action potential ?
If the integration of these postsynaptic potentials depolarizes the axon hillock enough.
What are the two types of summation ?
Spatial summation: summing potentials from different locations
Temporal summation: summing potentials across time
What is a chemical substance made within the body ?
Endogenous ligand
What are the six criteria of a substance to be considered a classic neurotransmitter ?
1) The substance exists in presynaptic axon terminals
2) The presynaptic cell contains appropriate enzymes for synthesizing the substance.
3) The substance is released in significant quantities when action potentials reach the terminals
4) Specific receptors that recognize the released substance exist on the postsynaptic membrane
5) Experimental application of the substance produces changes in postsynaptic cells
6) Blocking release of the substance prevents presynaptic activity from affecting the postsynaptic cell
Where does the raw material are produced ?
It is produced in the nuclei and transport by anterograde.
What are the three big families of transmitters
Amino Acids: GABA, glutamate
Amines: Acetylcholine (ACh), norepinephrine, epinephrine, dopamine
Neuropeptides: Oxytocin, nitric oxide (gas)
What is co-release ?
The appearance of ore than one neurotransmitter in a given vesicle.
What are the most abundant neurotransmitters in the brain ?
Amino Acids
True or false.
Glutamate and aspartate are the most prevalent inhibitory neurotransmitters in the brain.
False.
Glutamate and aspartate are the most prevalent EXCITATORY neurotransmitters in the brain.
Glutamate is also associated with which phenomena ?
Excitotoxicity. The property by which neurons die when overstimulated, as with large amount of glutamate.
What glutamatergic transmission employs ?
Ionotropic receptor (AMPA, kainate, NMDA), Fast-acting
Metabotropic receptor (mGluR’s), slow-acting
*the names of these receptor subtypes refer to drugs that activate them
What is making NMDA receptors different from AMPA or kainate receptors ?
Magnesium is blocking the way. So, the postsynaptic cell’s inside needs to depolarize to pop out the Mg2+. The magnesium is popped out by electrostatic repulsion. (Magnesium is a positive ion and the inside of the cell is more positive)
How can a postsynaptic cell can depolarize if channels are closed ?
There are other receptors that can allowed a depolarization.
Which amino acids have an inhibitory effect ?
GABA and glycine
What GABA-ergic transmissions employs ?
Ionotropic receptors: (GABAa, GABAc) Fast-acting
Metabotropic receptors: (GABAb) Slow-acting
Why some receptors are fast-acting and others are slow-acting ?
Because the fast-acting receptors are ionotropic, which means that they allow need a ligand to bind to the receptor and then, the channel will open.
Slow-acting receptors are metabotropic, which means that they work through a second messenger.
What happened when channels are opened by GABA knowing that they have a inhibitory effect ?
Channels let negatively charge ions to go through (chloride). They go through the channel by diffusion because there is a higher concentration of chloride outside the cell than inside.
What are the two types of ACh receptors ?
Nicotinic: mostly ionotropic and excitatory, important in muscle contraction
Muscarinic: metabotropic, ionotropic or excitatory
What are the two main classes of amines ?
Catecholamines: dopamine, norepinephrine and epinephrine
Indoleamines: serotonin and melatonin
True or false.
Dopamine can be a neurotransmitter or an hormone
True.
What is the amino acid that all catecholamines synthesized from ?
Tyrosine
The indoleamine neurotransmitters derived from which amino acid ?
Tryptophan
What are the two main indoleamines neurotransmitters ?
Melatonin and serotonin
What happen if we don’t have the enzyme that synthesized dopamine ?
We don’t have a dopamine and the other neurotransmitters synthesis.
What are the main catecholamine neurotransmitters ?
Dopamine, norepinephrine and epinephrine
What is cholinergic cell ?
Cell that use acetylcholine as their synaptic transmitter.
What is common with both muscarinic and nicotinic cells ?
They both respond to their specific chemical response and acetylcholine
Which dopamine receptors activates the second messenger ?
D1 and D5 receptors.
Which dopamine receptors inhibit the second messenger ?
D2, D3, D4 receptors
When we talk about dopamine, the second messenger is involved. What is the first messenger ?
The first messenger is the neurotransmitter (dopamine)
What are the names of the two pathways that dopaminergic neurons projected ?
Mesolimbocortical pathway
Mesostriatal pathway
Norepinephrine receptors are ionotropic or metabotropic ?
Metabotropic
What do we need to synthesize serotonin ?
Tryptophan
True or false.
Serotonin can be both excitatory and inhibitory.
True.
What is the abbreviation of serotonin ?
5-HT
What are exogenous ligands ?
Drugs, toxins (outside the body)
What are the roles of nitric oxide (NO) ?
Stimulates the production of second messengers.
Serves as retrograde transmitters (diffuses from the postsynaptic neuron back to the presynaptic neuron)
True or false.
Drugs can’t affect stages of neural conduction and synaptic transmission.
False.
Drugs can affect stages of neural conduction and synaptic transmission.
True or false.
Presynaptic events can be modified by drugs.
True.
What are the three effects of drugs on Transmission Production ?
Inhibition of transmitter synthesis
Blockade of axonal transport
Interference with the storage of transmitters
What are the three effects of exogenous ligands on Transmission Release ?
Prevention of synaptic release: by blocking voltage-gated Na+ channels
Alteration of synaptic transmission release: by blocking Ca+ influx
Alteration of transmitter release through modulation of presynaptic activity: via autoreceptors
Where autoreceptors are located ?
In the presynaptic cell membrane.
In a neural transmission context, what happen when we drink coffee ?
The caffeine blocks the autoreceptors effects of adenosine. By blocking adenosine, caffeine increases catecholamine release, resulting in the arousal.
Adenosine acts as a neuromodulator; it is normally co-released with primary transmitters to control synaptic activity by inhibiting transmitter release.
What is the role of transporters ?
They take back excess neurotransmitters to the presynaptic terminal.
What are the three effects of drugs on Transmitter Clearance ?
Inactivation of transmitter reuptake: by blocking transporters
Blockade of transmitter degradation: by inhibiting specific enzymes that normally break down neurotransmitters molecules in the axon terminal or in the synaptic cleft. As a result, transmitter remains active longer and to greater affect.
What is the mechanisms that make the movement of substances from blood vessels into brain cells more difficult than exchanges in other body organs and affording the brain greater protection from exposure to some substances found in the blood ?
Blood-brain barrier
What is the difference between affinity and efficacy ?
Affinity: The degree of chemical attraction between a ligand and a receptor. Even at low doses, high affinity drugs will bind to the receptor. Lower affinity drugs will bind fewer receptor molecule.
Efficacy: The extent to which a drug activates a response when it binds to a receptor.
Neurotransmitters are high-affinity ligands or low-affinity ligands ?
Low-affinity ligands because it allows them to rapidly dissociate from receptors.
What is a ligand that initiates the normal effects of the transmitter on a receptor.
Agonist ligand
What is a ligand that binds to the receptor but does not activate it ?
Antagonist ligand
Can a ligand be agonist and competitive ?
Yes.
What is a substance that directly competes with the endogenous ligand for the same binding site on a receptor molecule ?
Competitive ligand.
What is a substance that alters the response to an endogenous ligand without interacting with the endogenous ligand’s binding site
Noncompetitive ligand.
'’Some substances bind to receptors but do not activate them. Instead, they simply block agonists from binding to the receptors.’’ How are they classified ?
Competitive antagonist ligands.
True or false.
Agonists have low-efficacy. Antagonists have high-efficacy.
False.
Agonists have high-efficacy. Antagonists have low-efficacy.
Why is the combination of affinity and efficacy is important ?
Because it determines the overall action of a drug.
What is up-regulation ?
Increase in the number of receptors.
What is down-regulation ?
Decrease in the number of receptors.
What are the 6 types of chemical communication that organisms use ?
Endocrine communication
Synaptic communication
Autocrine communication
Paracrine communication
Phrenomone communication
Allomone communication
Tip: ESAPPA
What are the two types of communication that are considered Ectocrine communications ?
Phrenomone communication
Allomone communication
What is an autocrine communication ?
A released chemical acts on the releasing cell itself and thereby affects its own activity (autoreceptors)
What is a paracrine communication ?
The released chemical signal diffuses to nearby target cells. The strongest impact is on the nearest cells.
What is the difference between phrenomone communication and allomone communication ?
Phrenomone: Chemical signal that is released outside the body of an animal and affects other members of the SAME species.
Allomone: Chemical signal that is released outside the body by one species and affects the behavior of OTHER species.
True or false.
Neural messages are slower that hormonal messages
False.
Neural messages are faster that hormonal messages
What is a neuroendocrine cell ?
A neuron that release hormones into the blood.
In ancient civilizations, how did we learn that testes are important in the production and the release of testosterone ?
By the effects of castration.
What is an endocrine gland ?
A gland that secretes hormones into the bloodstream to act on distant targets.
True or false.
Hormones act as a on-off switch on target cells
False.
Hormones act by changing the probability or intensity of a behavior. It takes more time than neural messages.
Some hormones can be controlled by what ?
Circadian clock
True or false.
Hormones can only affects cells with a receptor protein for that hormone.
True.
What are the three main classes of hormones ?
Peptide/Proteins hormones
Amines hormones
Steroid hormones
What is a hormone that is composed of string of amino acids ?
Peptide/ Proteins hormones
What is the difference between a peptide hormone and a protein hormone ?
Peptide is small protein - a short string of amino acids (less than 50)
Protein hormone (more than 50)
What is a hormone composed of modified version of single amino acid ?
Amine hormone
What are the two classes of amine hormones ?
Catecholamines and indoleamines
What hormone is derivate of cholesterol ?
Steroid hormone
What hormone can easily pass through cell membrane ?
Steroid hormone because they can dissolve easily in lipids.
Which type of hormones are binding to receptors that are on the surface of the target cell membranes ?
Peptide hormones and amines hormones.
Which type of hormones that will pass through the cell membrane and will bind to specific receptors inside the cell ?
Steroid hormone
What happen when adrenocorticotropic hormone (ACTH) interacts with receptors on the membrane of cells in the adrenal gland ?
An increase in cAMP leads to the synthesis and release of other hormones.
Which type of hormones act faster ?
Peptide/protein hormones
Named one specific characteristic of steroid hormones regarding their receptors.
They can pass through the cell membrane (dissolve readily in lipids)
How do we named the binding between a steroid hormone and his receptor ?
Steroid-receptor complex
How do we named steroid hormones that act on more than one receptor ?
Receptor isoforms
What are two feedback systems ?
Positive feedback: Produced more !
Negative feedback: Stop producing !
What are the two main parts of the pituitary gland ?
Anterior pituitary (adenohypophysis)
Posterior pituitary: (neurohypophysis)
Which part of the pituitary gland connected the anterior and posterior gland ?
Pituitary stalk
*The axons extend only to the posterior pituitary
How does the posterior pituitary is working ?
Neuroendocrine cells bodies in the hypothalamus produce oxytocin and vasopressin.
Axons from these neurons pass through the pituitary stalk and terminate on capillaries of the posterior pituitary
When action potential arrives at terminal, hormones directly released into bloodstream.
What is the major role of vasopressin ?
Inhibits the formation of urine (ADH). This action helps conserve water.
What is the major role of oxytocin ?
Triggers the milk letdown reflex, the contraction of mammary gland cells that ejects milk into the breast ducts.
What type of hormones are produced in the anterior pituitary ?
Tropic hormones
What is the name of tropic hormones released by the anterior pituitary ?
By the release of various hormones from the hypothalamus, the anterior pituitary releases:
ACTH (adrenocorticotropic hormone)
TSH (Thyroid-stimulating hormone)
LH (Luteinizing hormone)
FSH (Follicle-stimulating hormone)
Prolactin
GH (growth hormone)
Which gonadotropic hormone (GnRH or GnIH) inhibits gonadotropin secretions ?
GnIH
What is the releasing hormone that is involved in adrenocorticotropic hormone (ACTH) production and secretion ?
Corticotropin releasing hormone (CRH)
What is the releasing hormone that is involved in production and secretion of Follicle stimulating (FSH) and Luteinizing Hormone (LH) ?
Gonadotropin releasing hormone (GnRH)
What is the role of adrenocorticotropic hormone (ACTH) ?
Controls production and release of adrenal cortex steroid hormones
True or false.
FSH triggers ovulation and development of corpus luteum in female and testosterone produce in mens
LH stimulates growth of egg-containing follicles in females and the production of sperm in mens
False.
FSH stimulates growth of egg-containing follicles in females and the production of sperm in mens
LH triggers ovulation and development of corpus luteum in female and testosterone produce in mens
What tropic hormones are stimulating mostly ?
The adrenal glands, the gonads
Where adrenal glands are located in the body ?
On top of kidney
What is the name of the subgroup involved with glucose metabolism ?
Glucocorticoids (ex: cortisol)
What is the name of the subgroup that affect ion concentration in tissue ?
Mineralocorticoids
What hormones adrenal medulla is releasing ?
Catecholamines (epinephrine and norepinephrine)
What is uncommon about the releasing hormones of the adrenal medulla ?
They are controlled by the sympathetic nervous system NOT tropic hormones.
What are the two gonads ?
Ovaries and testes
What are the two subcompartments of gonads ?
Sex steroids that produce hormones
Egg and sperm that produce gametes
Why gonadal hormones are important ?
Because they are triggering both reproductive behavior and gamete production.
What are the 4 ways that endocrine and neural systems work together ?
Neural-to-neural
Neural-to-endocrine
Endocrine-to-endocrine
Endocrine-to-neural
