PSC 101 Midterm #1
Describe afferent vs. efferent
*Afferent* describes input to the neuron, and *Efferent* describes output from the neuron. It is important to note that in the spinal cord, sensory inputs are Afferent, and motor outputs are Efferent. For example, cell bodies of touch neurons are on our hands, therefore they must bring info IN (thus think afferent).
Describe astrocytes
*Astrocytes*, or star cells, are a type of glial cell. Astrocytes provide physical support to neuron (i.e. they are the nerve glue that holds them together). In addition, when neurons die, astrocytes engulf the dead neurons and clean up debris within the brain. They also control the chemical composition of fluid surrounding the neurons and provide nourishment to them. Furthermore, astrocytes wrap processes around capillaries, and metabolize glucose into lactate, which is used by neurons to generate energy. Astrocytes also store glycogen, which can be used later in glucose metabolism
Describe barbituates
*Barbiturates* are still used as sedatives today but are also used to treat insomnia and epilepsy. Note that barbiturates are are also indirect agonists of GABA receptors. They are also very addictive and can lead to death.
What are the current uses for benzodiazepines
*Benzodiazepines* are indirect agonists of GABA receptors and are effective anxiolytics (which means that they are "anxiety dissolving" drugs). Today, benzodiazepines are used for hypnotic, anxiolytic, anticonvulsant, amnesic and muscle relaxing reasons. 1.) *hypnotic* uses of benzodiazepines act as short term treatments for insomnia 2.) *anxiolytic* uses of benzodiazepines act as short term anxiety treatment 3.) *anticonvulsant* uses of benzodiazepines are for short term epilepsy treatment 4.) *amnesic* uses of benzodiazepines are more premedication before surgury 5.) and lastly, benzodiazepines are used for muscle relaxing for painful muscle spasms.
Describe damage to the association cortex?
*Damage to the association cortex* can result in *hemispatial neglect*. People who suffer from hemispatial neglect can not seem to pay attention to portions of their visual field. In other words, they fail to notice.
Describe the drug effectiveness dose response curve
*Dose response curves* represent a drug's effectiveness. A little bit of a drug doesn't do anything and at some point, adding more of a drug doesn't make the effect any stronger.
How do drugs manipulate neural activity
*Drugs manipulate neural activity* by acting like neurotransmitters and neuromodulators. Drugs bind to receptors and then either act as an agonist or antagonist. If the drug induces the same effects as the endogenous ligand the drug is an AGONIST. But, if the drug blocks the effects of the endogenous ligand, then it is an ANTAGONIST.
Describe Extracellular Fluid
*Extracellular Fluid* is the fluid outside of the cell and is the fluid between neurons and glia. The extracellular fluid is mostly composed of water dissolved with salts and other chemicals
Describe G-protein coupled receptors
*G-protein coupled receptors* are present in metabotropic receptor types and involve an internal and an external component. When a signal binds to the receptor (externally), a conformational change activates the G-protein in a process that involves energy (internally). This results in a intracellular signaling cascade which is the activation of downstream enzymes triggering signaling cascades. G-protein coupled receptors can function to open nearby receptors BUT can also function to close nearby receptors, as well. Just like ionotropic receptors, metabotropic G-protein receptors can be inhibitory or excitatory
Describe GABA
*GABA* is one of the major inhibitory neurotransmitters in the brain. It is capable of binding to both ionotropic and metabotropic receptor types. Alcohol serves as a AGONIST at GABA receptors. GABA is produced from glutamic acid (by the action of the enzyme GAD aka glutamic acid decarboxylase). There are two GABA receptor types which are GABA-A and GABA-B. 1.) *GABA-A* receptors are ionotropic and are responsible for opening Cl-channels 2.) *GABA-B* receptors are metabotropic and control K+ channels Binding sites for GABA include one for tranquilizing drugs which are known as *benzodiazepines*. An example of a benzodiazepine drug is Valium. Benzodiazepines are indirect agonists and effective anxiolytics (which means that they are "anxiety dissolving" drugs). *Barbiturates* are also indirect agonists of GABA receptors.
What are glial cells
*Glial cells* are support cells that have important effects on neural transmission. There are four types of glial cells which are astrocytes, microglia, oligodendrocytes (which are only in the central nervous system) and Schwann cells (which are only in the peripheral nervous system).
Describe glutamate
*Glutamate* is one of the major excitatory neurotransmitters in the brain. It is capable of binding to both ionotropic and metabotropic receptor types. It is important to note that too much glutamate activity can induce excitotoxicity. There are four major types of glutamate receptors which are NMDA, AMPA, Kainate and Metabotropic. 1.) NMDA is ionotropic and has multiple ligand binding sites which is important because it allows both sodium and calcium to enter the cell. Calcium can serve as a second messenger and initiate intracellular signaling cascades. Alcohol acts as an antagonist of NMDA receptors by suppressing neural activity. 2.) AMPA is also ionotropic 3.) Kainate is ionotropic 4.) The Metabotropic receptors have 8 subtypes
Describe ionotropic vs. metabotropic receptors
*Ionotropic receptors* allow a molecule of a neurotransmitter to attach to a binding site which then opens the ion channel to allow ions into the cell. Ionotropic receptors allow the neurotransmitter to directly open the ion channel. With *metabotropic receptors*, the molecule of the neurotransmitter attaches to the binding site and indirectly opens an ion channel. When the neurotransmitter binds to the metabotropic binding site, a *G-Protein* is activated which then opens the ion channel. Metabotropic receptors demonstrate intracellular effects. Also metabotropic is slower than ionotropic.
Describe ligands
*Ligands* fit on receptors to either activate or block them. *Endogenous ligands* are inside the body and consist of neurotransmitters and hormones while *exogenous* ligands are outside the body and include drugs and toxins.
Describe lipids
*Lipids* are another type of neurotransmitter. For example, *endocannabinoids* are "endogenous cannabis-like substances"
Describe microglia
*Microglia* are very small glial cells that regularly move around within the brain, migrate to sites of injury or disease and function as the immune system of the brain, protecting the brain from invading microorganisms and is responsible for the inflammatory reaction in response to brain damage
How is multiple sclerosis related to oligodendrocytes
*Multiple sclerosis* is characterized by loss of function in the visual, motor, and sensory systems as a result of oligodendrocytes being destroyed, usually by the immune system (might be attacked by microglia). In addition, multiple sclerosis disrupts intra-neuron communication (aka communication within neurons). Multiple sclerosis isn't specific to any one system because myelin isn't specific to neurons in any one system!
Describe conduction (of an action potential) along myelinated axons
*Myelination* helps make action potentials faster by decreasing the rate of decay of the signal. The action potential is able to regenerate at each Node of Ranvier. Electrical signals move FASTER down the myelinated axon than the unmyelinated axon.
What is neural integration
*Neural integration* describes how excitatory and inhibitory post synaptic potentials affect each other. If several excitatory synapses are active at the same time, the EPSPs they produce summate/accumulate as they travel toward the axon, and the axon fires. Remember that excitatory post synaptic potentials lead the post-synapse to be depolarized which makes it likely for an action potential to fire. However, if several inhibitory synapses are active at the same time, the IPSPs they produce diminish the size of the EPSPs and prevent the axon from firing
Describe neurotransmitters
*Neurotransmitters* have 2 general effects which are excitation or inhibition and the specific action of a neurotransmitter depends on the receptor subtype to which it binds. Most synaptic communication in the brain is accomplished by 2 neurotransmitters which are glutamate and GABA. Glutamate is an excitatory neurotransmitter that depolarizes neurons while GABA is an inhibitory neurotransmitter that hyperpolarizes neurons.
Who is Otto Loewi
*Otto Loewi* discovered electrochemical transmission by concluding that some chemical substances must be involved in the electrical slowing of the heart, thus he provided the first evidence of electro-chemical transmission. Did this by dissecting two frog hearts and running tests on them.
Describe Ribosomes
*Ribosomes* are present in the cytoplasm or the rough ER. Ribosomes translate the instructions sent from the nucleus (and carried by mRNA) and produces proteins
Describe the function of signal cascades
*Signaling cascades* are slow and complex. Each stage of a signaling cascade can activate multiple effectors (i.e. allows one signal to do many things) and the end product can be varied. One benefit of the metabotropic g-protein signaling cascade is that the end product can be long-lasting change due to altering gene expression. This metabotropic g-protein signaling cascades also allows for complex modulations of other input. In metabotropic receptors, there is amplification and long lasting change.
Describe cations vs. anions
*cations* are positively charged and are mostly outside the cell while *anions* are negatively charged and are mostly inside the cell. Amount of cations and anions control resting membrane potential.
Describe diffuse modulatory systems
*diffuse modulatory systems* are neurotransmitters that are synthesized by a relatively small set of neurons. These neurons have diffuse projections from this central core to multiple regions of the brain. Examples include acetylcholine, dopamine, norepinephrine, and serotonin. 1.) *Acetylcholine* activates the cerebral cortex and facilitates learning 2.) *Dopamine* generally activates voluntary movements 3.) *Norepinephrine* increases vigilance and enhances readiness to act when a signal is detected 4.) and lastly, *serotonin* suppresses certain categories of species-typical behaviors and reduces the likelihood an animal will act impulsively
Describe excitatory vs. inhibitory post synaptic potentials
*post-synaptic potentials* can be either excitatory or inhibitory. 1.) With *excitatory post-synaptic potentials*(or EPSP), stimulation of the neuron leads the resulting post-synapse to be DEPOLARIZED and this is often a result of NA+ going into the cell. 2.) On the other hand, with *inhibitory post-synaptic potentials* (or IPSP), stimulation of the neuron leads the resulting post-synaptic region to be HYPERPOLARIZED and this is often a result of Cl- going into the cell. It is important to note that the terms *excitatory* and *inhibitory* get their name for their effects on other neurons, NOT their behavior. The effect of a neurotransmitters can be excitatory or inhibitory but it depends on the type of neurotransmitter released and what types of receptors are present on the post-synaptic neuron.
Describe how proteins are a product of a cell and how the are important for cell function
*proteins* are products of the cell. DNA is *transcribed* into mRNA in the nucleus. The resulting mRNA leaves the nucleus and is then *translated* into a protein in the ribosome (which is in the ER). The protein then folds into complex shapes that determine its eventual function. Proteins are important in order for the cell to function. Proteins provide structure for the cell and serve as enzymes (by controlling chemical reactions). Additionally, ion channels and neurotransmitter receptors are membrane spanning proteins and the transcription factors that bind to DNA to turn on genes are also proteins.
What are the effects of repeated administration of a drug
*repeated administration of a drug* can lead to tolerance or sensitization. 1.) *tolerance* occurs when a drug becomes less effective and oftentimes also leads to withdrawal 2.) *sensitization* occurs when a drug becomes more effective
Briefly describe the important directional terms
-Anterior/rostral means toward the head -posterial/caudal mean toward the tail (or feet if human) -lateral means toward the side -medial means toward the middle -dorsal mean on the back side/upside (*think dorsal fin) -ventral means on the stomach or bottom side -contralateral means opposite side -ipsilateral means same side note: coronal also means transverse
Where are the cell bodies of the afferent and efferent axons
1.) *afferent axons* carry sensory information to the spinal cord. Note that the cell bodies that give rise to axons that bring somatosensory information to the spinal cord reside in the dorsal root ganglia. Also note that these sensory neurons are UNIPOLAR. 2.) *efferent axons* carry information away from the spinal cord. Note that the cell bodies that give rise to the ventral root are located in the gray matter of the spinal cord. Also note that these motor neurons are MULTIPOLAR
Describe a membrane potential
A *membrane potential* is a difference in electrical voltage across the membrane of a neuron. When a neuron is at rest (aka the neuron is not firing an action potential), we call this *resting membrane potential*. Resting membrane potential is usually in the range of -40 to -90 mV (which we calculate by using a volt meter). The resting membrane potential of a neuron is usually in the range of -40 to -90 mV because there are more anions in the cytoplasm (intracellular) and more cations in the extracellular matrix and this is largely because Na+ stays outside while the neuron rests.
Describe a drugs binding affinity
A drug's *binding affinity* is the degree of chemical attraction between the ligand and the receptor. In other words, if a drug has a high affinity then it means you need less of a drug to bind the SAME amount. Note that the *efficacy* (or the intrinsic activity) is the ability of a bound ligand to activate the receptor.
What is an action potential
An *action potential* is a form of electrical communication within a neuron. Remember that communication WITHIN a neuron is intracellular communication. Action potentials, or nerve impulses, are brief but large changes in membrane potential that communicate information WITHIN the cell. Action potentials are all or nothing and patterns of action potentials carry information to target cells.
Describe hyper-polarization vs. depolarization
An action potential is generated due to either hyperpolarization or depolarization 1.) *Hyperpolarization* occurs when the inside of the cell becomes even MORE NEGATIVE than it is at rest. This increase in negative charge decreases the probability that the neuron will fire an action potential. In other words, the more negative the polarization=hyperpolarization Hyperpolarized 2.) *Depolarization* occurs when the inside of the cell becomes LESS NEGATIVE. This decrease in negativity increases the probability that the neuron will fire an action potential. In other words, the more positive the polarization=depolarization Note that a threshold must be reached for an action potential to be triggered
How is an action potential generated?
An action potential is generated due to hyperpolarization or depolarization. An action potential is more likely to fire when cell is depolarized.
Describe antagonist vs. agonist
An agonist is a ligand that binds a receptor and activates the receptor (in other words, an *agonist* leads to more activation) while an antagonist is a ligand than binds a receptor and prevents activation of the receptor (in other words, an *antagonist* leads to less activation by BLOCKing receptors). Direct means they directly bind with the receptor while indirect means the drug attaches to an alternative site (i.e. not the site that the neurotransmitter binds) to either prevent or facilitate a reaction. 1.) a direct agonist mimics the effect of a neurotransmitter. Molecules of the drug attach to the binding site to which the neurotransmitter normally attaches 2.) a direct antagonist occupies the receptor binding site preventing from the neurotransmitter from activating it. 3.) an indirect agonist attaches to an alternative binding site that facilitates activation 4.) an indirect antagonist is a drug that attaches to an alternative binding site that prevents activation
Describe the transmission of neural information
At chemical synapses, neurotransmitters can influence the resting potential of other neurons. Other than chemical synapses, there are electrical synapses (also known as *gap junctions*). In gap junctions ions flow directly through large channels into adjacent cells, with NO time delay.
How does the site of drug action effect the storage and release of neurotransmitters
Because neurotransmitters are packaged into vesicles for release by transporter molecules, the site of drug action *effects the storage and release of neurotransmitters*. Some drugs can bind to these transporter molecules and inactivate them. Other drugs can deactivate the proteins that allow the docked vesicles to fuse with the synaptic membrane for release. In addition, drugs can also have the opposite effect, which is binding to proteins and triggering the release of neurotransmitter.
What is passive spread vs. propagation
By *passive spread* alone, an electrical current would not reach the axon terminal because the electrical potential can decay. Local currents can *passively spread* directly to neighboring sites on the membrane (i.e. Na+ ions enter and spread to the negatively charged low Na+ concentrated areas) but passive spread alone is ineffective. Instead, the action potential propagates across teh axon. So, once the neighboring site effectively reaches the action potential threshold, the action potential REGENERATES! And because voltage-gated Na+ channels are concentrated along the axon at regular intervals, an action potential is able to be propagated along the axon. In other words, as an action potential moves along the axon, the action potential regenerates at each node! However, because the the opening of channels and flowing of ions takes time, propagation is a slow process. Furthermore, because of the refractory period, signals can NOT propagate back to where they came from. Thus, this is why axons tend to carry information only in ONE direction.
Describe tubules
Different types of *tubules* serve different functions, but in short, tubules are responsible for reinforcing the cell's structure, aiding in cell movement and forming transportation networks to move proteins to desired locations. It is important to note that transport along microtubules in the axon is known as *axoplasmic transport* and there are two types; anterograde and retrograde. *Anterograde* is fast and moves from soma to the terminal buttons while *retrograde* is the opposite. Retrograde is slower and moves from the terminal buttons to the soma.
Describe neuronal migration
During *neuronal migration* cells want to migrate to the surface. In order for the cell to migrate, the leading process of the neuron extends along the glial fiber. After this, the cell soma appears to contract and extend just prior to the release of the adhesion junction, which is underneath the cell soma. This sequence is repeated over and over again, as the neuron progresses along the glial fiber. This process aids in *cortical development* because the radially oriented fibers of the glial cells help guide the migration of newly formed neurons (from the ventricular zone to their final resting place in the cerebral cortex). Also note, as each successive wave of neurons passes the other neurons that migrated earlier, the most recently formed neurons occupy the layers closer to the cortical surface.
How can ions pass inside the membrane if this stable arrangement of the phospholipid bilayer isolates the cytosol (aka intracellular fluid) and extracellular fluid?
Extracellular Fluid and Cytosol (aka intracellular fluid) are separated by a phospholipid bilayer therefore ions pass through membrane with the help of ion channels!
What factors determine how much current will flow
Factors that determine how much current will flow through a channel are electrical potential and the electrical conductance. -*Electrical potential*, which is also called voltage, is the force exerted on a charged particle. The electrical potential reflects the difference in charge between the anode and cathode. For example, the difference in electrical potential between the terminals of a car battery is 12 volts; that is, the electrical potential at one end is 12 volts more positive than at the other. -On the other hand, *electrical conductance* is the relative ability of an electrical charge to migrate from one point to another (and it can depend on the number of charged particles and on the ease with which those particles travel through space). -If the conductance is zero, no current will flow even if the potential difference is very large. -If the potential difference is zero, no current will flow even if the conductance is very large.
Describe Oligodendrocytes and Schwann Cells.
It is important to note that *oligodendrocytes* and *Schwann cells* are both glial cells that have the same function but oligodendrocytes are only in the central nervous system while Schwann cells are only in the peripheral nervous system! Oligodendrocytes and Schwann Cells are known for wrapping axons in myelin. Oligodendrocytes and Schwann cells provide support to axons, and produce the Myelin Sheath. It is important to note that in between myelin sheaths are the *Nodes of Ranvier* which are not insulated with myelin. The myelin sheath is formed when an entire oligodendrocyte or Schwann cell wraps itself around a segment of the axon.
Why is it important to study how the brain develops
It is obviously important to study the brain for many reasons but it is important to note that the neural plate gives rise to all the neurons in the brain. However in order to understand brain development, we must examine how the brain develops. By examining how the brain develops we can understand how the brain is organized and how the different parts fit together. Neurons that grow up together are more similar to each other
Diffusion vs. electrostatic pressure in regards to K+
K+ wants to move from a higher concentration inside the cell (remember that outside of cell is more positive BUT there is a low concentration of K+ outside the cell) to a lower concentration outside the cell and uses the force of diffusion to do so. However, because K+ is positive and attracted to the negatively charged inside of cell, the force of electrostatic pressure moves K+ inside the cell. However, due to equilibrium, the two forces (diffusion and electrostatic pressure) balance and there is no net movement of K+. Thus, for every K+ ion that comes in one goes out
How long does myelination continue?
Myelination continues throughout childhood (to at least age 5). It is important to realize that brain continues to grow post-natal. (also note that the brain continues to develop well into adolescence and that within subjects designs have found that as subjects get older, the amount of grey matter in their brain decreases.)
Describe the shapes of neurons
Neurons are also classified by three general shapes and classification depends on how many axons/dendrites leave the nucleus. -*Multipolar neurons* are most common shape and are composed of one axon and many dendrites -*Bipolar neurons* are composed of one axon and one dendrite branch -*Unipolar neurons* have a single extension that branches in two directions, forming an input zone and an output zone
What type of communication do neurons engage in? (Describe intracellular and intercellular communication)
Neurons are specialized for communication. It is important to note that communication occurs within the neuron, which is known as *intracellular* communication. Communication can also occur between neurons, which is known as *intercellular* communication. Lastly, neuronal communication is BOTH electrical and chemical. -In *intracellular communication*, information flows *within* the neuron via electrical signals however, in *intercellular communication*, information typically flows *between* neurons via chemical signals (or chemical synapses), but it depends on the type of synapse.
Describe the structure of neurons
Neurons have three unique structural elements which are its axon, dendrite and synapse. However, there are many structural components to a neuron. -The *soma* is the cell body containing the nucleus. Also contains protein synthesizing machinery . This is also the area of input where the neuron collects and integrates information from the environment or other neurons. -the *dendrites* are the tree branches off the soma that receive information from the terminal buttons of other neurons - the*terminal buttons* are the buds at the end of the branch of the axon that send information to other neurons. This is an area of output where neuron transfers information to other cells. -the *axon* extends from the cell body and conveys information in the form of electrical potentials from the soma to the terminal buttons.
Describe how neurons actively maintain precise concentrations of several important ions inside and outside the cell
Note that the outside of a cell (the extracellular fluid) is mostly positive while the inside of the cell is mostly negative. K+ is in low concentration outside the cell even thought the outside of the cell is mostly positively charged. This is due to the higher concentration of Na+ and Ca++ outside the cell. On the other hand, similarly to K+'s situation, there is a small concentration of Cl- inside the cell (which is mostly negative) but the inside of the cell maintains its negative charge due to the high concentration of A-.
Describe nonsynaptic chemical communication
Some forms of *nonsynaptic chemical communication* include when neurotransmitters are released by terminal buttons and bind to receptors on cells a short distance away. Also, neuromodulators are chemicals released by neurons that travel farther and are more dispersed. Most neuromodulators are peptides that exert effects by binding to receptors on the surface of target cells.
Where are some of the places that synapses can synapse and if it can effect what is released.
Synapses can *synapse in many places* such as dendrodendritic, axodendritic, axoextracellular, axosomatic, etc. In other words, axons do NOT just terminate at the dendrites! Furthermore, where an axon binds can change the effect it has and can effect the amount of neurotransmitters released
Describe the automatic nervous system
The *automatic nervous system* is composed of the sympathetic and parasympathetic nervous system. Together, the dympathetic and parasympathetic systems maintain the body's homeostasis. *Homeostasis* describes a dynamic process that involves two opposing systems pulling in opposite ways to achieve balance. 1.) The *sympathetic nervous system* is commonly referred to as "fight or flight" because preganglionic neurons synapse on the sympathetic Chain release Acetylcholine and postganglionic neurons innervate smooth muscle, organs, and glands, releasing Norepinephrine on these targets. In other words, it prepares up to fight or run. 2.) the *parasympathetic nervous system* is commonly referred to as "rest and digest" and is the opposite of the sympathetic. This is because parasympathetic ganglia are dispersed and close to the target and ostganglionic neurons release acetylcholine on targets.
What is the basal ganglia
The *basal ganglia* forms from the forebrain and telencephalon and includes the caudate nucleus, the putamen, the globus pallidus, and the subthalamic nucleus which are all important nuclei in regard to motor control.
Describe the cell membrane
The *cell membrane* is essentially a barrier and gatekeeper. The phospholipid bilayer or the cell membrane separates the intracellular fluid from the extracellular fluid. The relative extracellular impermeability of the cell membrane ensures that the concentration of substances inside and outside of the cell are different. It is important to note that the *phospholipid molecule* present in the phospholipid bilayer has a hydrophilic head (meaning it has polar regions) and a hydrophobic tails (which has no polar regions).
How do the cerebellum and pons form?
The *cerebellum* and *pons* form from the meTencephalon which is a subdivision of the HINDBRAIN. These structures are important for balance and movement.
Describe the corpus callosum
The *corpus callosum* joins the left and right hemispheres of the brain. It is important to note that there are bundles of axons in the corpus callosum that serve different regions of the cerebral cortex.
Describe the diencephalon
The *diencephalon* is a subdivision of the forebrain that becomes the hypothalamus and the thalamus. The *thalamus* is a cluster of "relay" nuclei that are known for relaying sensory information and the *hypothalamus* regulates functions that are critical for survival of the self or species. A midsagittal view of the brain will show nuclei of the hypothalamus.
Describe the ER
The *endoplasmic reticulum* is the site of mRNA translation, which is the process that creates proteins. The Endoplasmic Reticulum (ER) is essentially the site of synthesis of proteins in the rough ER (in the ribosomes) or lipids in the smooth ER.
Describe the Intracellular Fluid
The *intracellular fluid* or cytoplasm is the fluid inside the cell which can also be described as the viscous substance in the interior of a cell that contains proteins, and other cellular components
How does the limbic system develop?
The *limbic system* ALSO forms from the forebrain and telencephalon. The limbic system is largely involved with motion and learning.
How has the neocortex expanded throughout the course of evolution?
The *neocortex has expanded* throughout the course of evolution. However, regions that directly receive sensory information or control motor responses have NOT expanded. Instead, it is the "in between" regions of the cortex that have expanded throughout evolution. For example, the *association cortex* is not immediately sensory or motor, but it is related to complex functions such as perception, language, problem-solving, etc.
Describe the nucleus and what is contained in the nucleus (i.e. chromosomes, genes and mRNA)
The *nucleus* is the site of gene TRANSCRIPTION. The nucleus contains all of the instructions for cellular activities (in other words, the nucleus contains the chromosomes). -*Chromosomes* are essentially DNA coiled around proteins, which carry genetic information. -*Genes* are the functional unit of the chromosome. Genes directs the synthesis/creation of proteins (one or more). -*Messenger RNA* (mRNA) leaves the nucleus and delivers the genetic information concerning synthesis of a protein to the ribosome
Describe the peripheral nervous system
The *peripheral nervous system* is composed of the somatic and automatic nervous systems. 1.) The *somatic nervous system* is the part of the PNS that controls the movement of skeletal muscles and transmits somatosensory information to the CNS. Nerves involved in the somatic nervous system include cranial and spinal nerves. 2.) The *automatic nervous system* is the part of the peripheral nervous system that controls the body's "vegetative functions". The automatic nervous system consists of the sympathetic and parasympathetic nervous systems.
Describe the sequence of synaptic transmission (ONLY involving the pre-synapse)
The *sequence of synaptic transmission* begins when the The action potential is propagated into the presynaptic axon terminal. Next, voltage-gated Ca++ channels open. Then the Ca++ causes synaptic vesicles to fuse to the presynaptic membrane, rupture, and release neurotransmitter into the synaptic cleft.
Describe the sequence of synaptic transmission (in the pre-synapse and post-synapse)
The *sequence of synaptic transmission* begins when the The action potential is propagated into the presynaptic axon terminal. Next, voltage-gated Ca++ channels open. Then the Ca++ causes synaptic vesicles to fuse to the presynaptic membrane, rupture, and release neurotransmitter into the synaptic cleft. THEN *some neurotransmitter molecules bind to receptors on the postsynaptic membrane leading *(directly/indirectly)* to the opening of ion channels *(depending on whether is binds to a ionotropic or metabotropic receptor)* AND excitatory or inhibitory post synaptic potentials in the postsynaptic membrane* [Then... The excitatory or inhibitory post synaptic potentials then spread toward the hillock and if the integration of signals results in depolarization to the threshold, the neuron fires an action potential. Then the synaptic neurotransmitter is either degraded or removed from the synapse. Negative feedback can occur via autoreceptors]
Describe the spinal cord
The *spinal cord*'s principal function is to distribute motor fibers to glands and muscles and to collect somatosensory information that will be passed on to the brain. For example, the ventral fibers carry information from the spinal cord to the muscles while dorsal fibers carry information from the body to the spinal cord. Furthermore, there is grey matter that consists mostly of cell bodies and while matter that is arranged in the dorsal and ventral tracts.
describe spinal nerves
The *spinal nerves* begin at the junction of the dorsal and ventral roots of the spinal cord. The efferent nerves leave the spinal cord to innervate muscles. The afferent nerves carry sensory information to the spinal cord. It is important to note that the cell bodies of all the axons that bring information into the brain and spinal cord are outside of the CNS (with the exception of the visual system).
How do the tectum and tegmentum form
The *tectum* and *tegmentum* form from the meSencephalon which is the subdivision of the MIDBRAIN! The tectum and tegmentum are important for diffuse modulatory systems
What is the therapeutic index
The *therapeutic index* equals the Effective Dose50 over the Lethal Dose50. i.e. the therapeutic index=Effective Dose50/Lethal Dose50. This index allows us to major how safe it is to use a drug. A wide therapeutic tends to be safer than a narrow therapeutic index.
Describe the ventricular system and what is does for the brain
The *ventricular system* helps feed and protect the brain. The ventricular system is a series of chambers filled with cerebrospinal fluid. *Cerebrospinal fluid* acts as a shock absorber and provides an exchange medium between blood and brain
What are the most notable features of the CNS and PNS
The CNS is known for containing the brain, spinal cord and retina while the PNS is known for being responsible for the somatic nervous system (voluntary), the automatic nervous system (which is involuntary) and the cranial nerves.
How does an action potential reach the axon terminal?
The action potential reaches the axon terminals because the action potential is regenerated along the length of the axon. When an action potential is triggered, its size remains undiminished as it travels down the axon (remember an action potential is an all or nothing experience). The speed of conduction can be calculated from the delay between the stimulus and the action potential (i.e. the membrane permeability's peak/most positive charge of the voltage). Furthermore, as the action potential moves down the axon, Na+ channels open generating axon potential. The depolarization spreads rapidly like "electricity through a wire". Thus as depolarized Na+ channels open, the action potential is recreated at each node which allows the action potential to reach the axon terminal.
What are the three primary vesicles involved in brain development?
The first step in differentiation of the brain is the development of 3 primary vesicles. The entire brain develops from these 3 vesicles which are known as the forebrain, the midbrain and hindbrain.
Describe the cerebral cortex of the brain
The forebrain consists of the telencephalon which develops into the *cerebral cortex*. When thinking of a cortex, think of the bark on a tree because a *cortex* is the surface area of the brain. It is important to note that the *cerebral cortex* is actually two sheets (one per hemisphere) and it is folded. Note that the folding of the cortex takes up less space, therefore the cortex is able to increase it's surface area by folding. Also note that the surface area of the cerebral cortex varies substantially between species.
What is unique about the axon of a giant squid
The giant squid axon is GIANT and is even visible to the human eye.
Describe motor neurons vs. sensory neurons vs. interneurons
The nervous system controls behavior due to motor neurons, sensory neurons and interneurons. -*Motor neurons* are neurons located inside the central nervous system and control the contraction of muscles or secretion of glands -*Sensory neurons* are neurons that detect changes in the external or internal environment and send information to the central nervous system -*Interneurons* are neurons located inside the central nervous system
Describe the neuron cell body
The neuron cell body is the same as other cells. It contains Cell membrane, Extracellular fluid, Intracellular fluid (cytoplasm), Nucleus, Endoplasmic Reticulum, Ribosomes, Golgi Bodies, microfilaments and microtubules, Mitochondria and Lysosomes. Here is a brief overview of all the functions of the components of the neuron cell body. 1. *Cell membrane* separates the cell from its surroundings and regulates what enters and leaves the cell. The cell membrane is essentially a barrier and gatekeeper. 2. *Extracellular fluid* is the fluid outside of the cell 3. *Intracellular fluid* (or the cytoplasm) is the fluid inside the cell 4. the *Nucleus* contains the genetic blueprint for the cells proteins, stores these blueprints then copies and sends out to the rest of the cell. 5.*Endoplasmic Reticulum* is where the cell's protein products are assembled 6. *Ribosomes* is where the protein is assembled 7. *Golgi Bodies* are where the proteins are wrapped, packaged and shipped. 8. microfilaments and microtubules deliver the protein product to its destination. 9. *Mitochondria* creates the cell's power supply and is also known as the "powerhouse of the cell" 10. *Lysosomes* are vesicles that transport incoming supplies as well as move and store waste.
How does the neurotransmitter affect the neuron on the other side of the synapse?
The neurotransmitter binding site can effect whether the ion channel is opened directly or indirectly (i.e. ionotropic or metabotropic). The type of neurotransmitter released from the presynaptic membrane can lead to an excitatory or an inhibitory post-synaptic potential. This is because at the synapses, neurotransmitters can influence the resting potential of other neurons.
how does the action potential cause the axon terminal to release neurotransmitters into the synapse? (aka describe the PRESYNAPTIC release of a neurotransmitter)
The process begins when an action potential reaches the terminal (of a terminal button) and opens calcium channels. The incoming calcium ions then bind to molecules in the synapse (i.e. the gap between terminal button and dendrites) to form a complex. This complex binds to VESICLES. It then releases some from filaments and induces others to bind to the presynaptic membrane (edge of terminal button), where they will empty their contents. In more detail, an undocked synaptic vesicle will dock to proteins on the presynaptic membrane. When the synaptic vesicle fuses to the presynaptic membrane, the membrane will open allowing for the release of neurotransmitters from the terminal buttons.
What are some routes to administer drugs
The route in which a drug is administered determines the drug's effects (in addition, the route of administration effects how quickly the drug will work as well). Drugs can be administered through ingestion, inhalation, peripheral injection (i.e under skin, into vein) or through a central injection (i.e. into the brain or ventricles).
How does the site of drug action effect receptors (postsynaptic)
The site of drug action *effects receptors (postsynaptic)* because the drug can bind to neuromodulator or neurotransmitter binding sites.
How does the site of drug action effect reuptake or destruction of neurotransmitter
The site of drug action *effects reuptake or destruction of neurotransmitters* because after stimulation of postsynaptic receptors, neurotransmitter molecules are taken back into the cell.
What are the two forces driving membrane potential
The two forces driving membrane potential are *diffusion* and *electrostatic pressure*. An example of diffusion is putting green food coloring in a glass a water- the food coloring will defuse and turn the whole glass of water green. Diffusion is simply the desire of a molecule to move from an area of high concentration to an area of lower concentration. On the other hand, *electrostatic pressure* is the pressure that causes molecules to want to pass though the membrane i.e. positive molecule on outside of cell will want to move to negatively charged inside of cell. Due to unequal distribution of electrical charge carried by ions on the two sides of the membrane, membrane potential (aka a difference in electrical charge) results
Why isn't the cell filled with Na+?
There are *different types of ion channels* and channels are selective for particular ions. Some channels can be gated (which means that they can be opened and closed to control diffusion). Thus the cell isn't filled with Na+ because there are more K+ ion channels than there are Na+ ion channels. During the action potential, voltage-gated Na+ channels open to allow Na+ entry, but these channels quickly inactivate and reset. Thus, the amount of time that Na+ is entering the axon is small. In addition, the *sodium-potassium pump* pushes Na+ ions out and pulls K+ ions in (in fact, for every 3 Na+ ions out, 2 K+ ions come in).
What are the 5 subdivisions of brain development?
There are *five subdivisions* of brain development. The *forebrain* develops into 2 divisions which are the *telencephalon* and the *diencephalon*. The telencephalon will become the two cerebral hemispheres which consist of a cortex in addition to some deeper structures (such as the basal ganglia and the limbic system). On the other hand, the diencephalon or the "between brain" will develop into the thalamus and hypothalamus. The *midbrain* will develop into the tectum and tegmentum. And last the the *hindbrain* will develop into two divisions known as the metencephalon and the myelencephalon. The *metencephalon* will develop into the cerebellum and the pons while the *myelencephalon* will develop into the medulla. It is important to note that some of these structures (i.e. the midbrain, pons and medulla) will refer to the brainstem. In short: -forebrain>telencephalon> cerebral cortex, basal ganglia and limbic system -forebrain> diencephalon> thalamus and hypothalamus -Midbrain> mesencephalon> tectum and tegmentum -Hindbrain> metencephalon> cerebellum and pons -Hindbrain> myelinencephalon> medulla oblongata
What are the stages of neural development?
There are *six stages of neural development* which are neurogenesis, cell migration, differentiation, synaptogenesis, neuronal cell death, synapse rearrangement and lastly, cell death. 1. Neurogenesis is when mitosis produces neurons 2. Cell migration occurs when cells move to establish distinct populations 3. Differentiation is when the cells become distinctive neurons or glial cells 4. Synaptogenesis is the establishment of synaptic connections 5. Neuronal cell death is the selective death of some nerve cells 6. and Lastly, synapse rearrangement is the loss or development of synapses and fine-tuning of synapses
Describe cranial nerves
There are 12 pairs of *cranial nerves*. Most cranial nerves innervate the head and neck, but the Vagus nerve (aka the "wandering nerve") is known for innervating the internal organs of the thoracic and abdominal cavity.
Describe the blood brain barrier
Tight junctions between endothelial cells that form blood vessels in the brain prevent large molecules from passing from the blood into the brain. This is known as the *blood-brain barrier*. The blood brain barrier helps prevent infections and toxins from coming in contact with brain cells. It also prevents many hormones and drugs from accessing neural cells
Describe a gyrus vs. sulcus
When looking at the grooves of the brain, a *gyrus* is the elevation or the bump of the grooves while a *sulcus* is the dip or valleys of those grooves.
How do voltage-gated channels react when the cell is depolarized (i.e. how does an action potential occur).
When the cell is DEPOLARIZED to -40mV (meaning the inside is slightly less negative than normal), voltage-gated Na+ channels open. Remember that a cell is more likely to fire an action potential when it is depolarized! Due to the force of diffusion, Na+ wants to move from an area of higher concentration outside the cell to an area of lower concentration inside the cell. In addition, the force of electrostatic pressure states that because sodium is positive, it wants to move inside the cell because it is attracted to the negative charge inside of the cell. Thus, depolarization to the threshold opens voltage gated Na+ channels, allowing Na+ to enter the inside of the cell. However, now that the inside of the charge is more positive due to the addition of Na+, the positive charge inside the cell pushes K+ out and additional voltage-gated K+ channels open to allow for a greater outflow of K+. Note that Na+ channels become refractory and no more Na+ enters the cell at the membrane potential's peak (reminder that the membrane potential is the electrical voltage across the membrane of a neuron). This process explains an action potential.
Describe channels vs. gates vs. pumps in regards to crossing the cell membrane.
molecules can cross through the cell membrane due to channels, gates and pumps. -With a *channel*, ions can only cross through appropriately shaped channels, -*gates* change shape to open and close -*pumps* change shape to CARRY substances across a cell membrane.
Describe golgi bodies
once proteins are assembled in the ribosomes, they are packaged and sent throughout the cell by the golgi bodies. *Golgi bodies* provide the "packaging rooms" where the proteins are "wrapped" in membrane, addressed and shipped.
Describe peptide neurotransmitters
peptide neurotransmitters are another type of neurotransmitter. *Opioid peptides* mimic opiate drugs such as morphine. In addition, when pituitary hormones such as Oxytocin and Vasopressin are released directly into the brain (not the bloodstream), they are considered peptide neurotransmitters.
How can postsynaptic potentials be terminated by neurotransmitter reuptake
postsynaptic potentials (excitatory or inhibitory) can be terminated by neurotransmitter reuptake meaning that the molecules of a neurotransmitter are returned to the terminal buttons.
Describe the mechanism of action for a metabotropic receptor
the *mechanism of action for a METABOTROPIC receptor* can be described in three steps. First, the neurotransmitter binds to a G-protein coupled receptor. Then, the G-protein is activated inside the cell. The activated G-protein then activates an effector system.
Describe the pituitary gland
the *pituitary gland* controls the hormones released by neurosecretory cells in the hypothalamus. These hormones enter capillaries and are transported to the anterior pituitary gland (note that capillaries surrounds the hypothalamus). The pituitary gland then controls the secretion of hormones. The hormones of the posterior pituitary gland are produced in the hypothalamus and carried there by vesicles by the process of axoplasmic transport (note that axoplasmic transport is the transport along microtubules in the axon).
How does the site of drug action effect the production of neurotransmitters
the site of drug action effects the *production of neurotransmitters* because the drug can block post synaptic receptors. Some drugs can break-down or modify existing neurotransmitters so that the neurotransmitter no longer functions. This often works by modifying the neurotransmitter protein.
Describe neurogenesis in adults and the C14 studies effect
to begin, *neurogenesis* is when new neurons are created. However, it is important to note that adult neurogenesis is difficult to study. While skeptical, most scientists believe that neurogenesis occurs in the hippocampus in humans. One research group attempted to study this by examining the amount of carbon 14 (C14) that was released into the atmosphere by nuclear bombs during periods of nuclear testing. If neurons were all created at birth, you would expect that the neurons of a persons brain would reflect the amount of C14 that was in the atmosphere AT THE TIME of birth. However, this was NOT the case because people born before nuclear testing ALSO had C14 in their hippocampal neurons. Therefore there is proof for neurogenesis.
