Midterm #1 Flashcards
What is Consciousness
State or quality of awareness – awareness of our thoughts, perceptions, memories, and feelings
What is a Frontal Lobotomy
Outdated surgical approach for treating seizure disorder (epilepsy) that involves cutting the corpus callosum: the bundle of nerve fibers that connect the left and right sides of the cerebral cortex.
Generally effective, but it has unacceptable side effects.
Why can’t we do frontal lobotomy anymore?
Our cerebral hemispheres are critical for our ability to consciously process sensory information (sights, sounds, touch, etc).
What is the left brain responsible for?
The left brain is largely responsible for the right side of the body.
Left brain processes right side of the eyes
Consciousness must be located in the left part of the brain
Language is on the left side as well
What is the Right Brain responsible for?
The right brain is largely responsible for the left side of the body.
Right brain processes left side of the eyes
What is the corpus callosum?
Enables the two hemispheres to share information so that each side knows what the other side is perceiving and doing.
What happens if we cut the corpus callosum?
If it is cut – the hemispheres can’t talk to each other but can talk to the spine
Left hand sometimes seemed to have a mind of its own
What happens if a Slpit brain patient has his eyes closed and touches an object with his LEFT HAND
Cannot identify the object out loud - left hand = right brain
Left brain is responsible for language
What did the sperry lab prove?
When the command ‘laugh’ was directed to the right hemisphere of one patient, he laughed. When asked why he was laughing, he said “you guys come up and test me every month – what a way to make a living!
what is the interpreter theory
Behavior is fully controlled by unconscious processes, and that the function of our left-brain consciousness is create narratives in an attempt to make sense of the world.
What is mind-body dualism
If our intuitions and perceptions are misleading, if the earth is actually spinning and hurtling through space, what can we trust? After doubting everything, even existence itself, Descartes eventually drew a line in the sand and famously stated, “I think, therefore I am.”
What is an ion
If a molecule or single atom has an electric charge, it is called an ion.
Ions form ionic (electric) bonds with each other.
What happens if ionic bonds go in water
Ionic bonds typically break apart (dissolve) in
what is a salt
Molecules held together by ionic bonds
what represents the six most important chemical elements whose covalent combinations make up most biological molecules on Earth.
CHNOPS
carbon, hydrogen, nitrogen, oxygen, phosphorus, sulfur,
what is a ribosome
RIBOSOME – When RNA can catalyze a reaction
Consists of strands of RNA and strands of amino acid (i.e. proteins)
what is an enzyme
When a protein can catalyze a chemical reaction
what is a phospholipid bilayer and what does it do?
Phospholipid are a long strand of fat (lipids) with a phosphate cap
Lipids prefer the company of other lipids – phosphate caps prefer to interact with water
Phospholipids often form bilayer sheets if left undisturbed
When shaken, phospholipids form micelles (soap bubbles)
If your hands are greasy water just bounces off – when you wash your hands…
Prokaryotic cell
Cell membrane filled with cytoplasm
Very long, loose strands of DNA (strings of nucleic acids) and shorter loose strands of RNA
Ribosomes (which are made of strands of RNA and strands of amino acids)
The function of ribosomes is string together the amino acids held by tRNA in the order dictated by the genetic code. Thus, ribosomes make proteins.
Eukaryotic cell (that prokaryotic does not have)
The mitochondria – digest sugar and can grow into ATP molecule
Extract energy from nutrients
Create ATP molecules by digesting sugar molecules
Nucleus
Safely imprisons the cell’s long strands of DNA.
Compacted strands of DNA within a nucleus (Chromosomes)
What is a genome
Provides information necessary to synthesize all cell’s proteins
Sections of the genome that gets transcribed into RNA and translated into proteins
what is a gene
Section of DNA that codes for a specific protein
When a gene is read, that segment of DNA is transcribed into RNA.
After RNA leaves the nucleus; ribosomes translate RNA to create proteins.
What is the basic structure of a neuron
soma/cell body
dendrites
axon
axon terminal
synapse
What is the resting membrane of a neuron
-40mV to -90mV
What are ions and what are they called when they are negative or positive?
charged atom or molecule
Cations are positively charged
Anions are negatively charged
What is electrostatic pressure
Attractive force between molecules that are oppositely charged
OR repulsive force between molecules that are similar charged
what are ion channels vs leak channels
Ion channels
Specialized protein molecules that sit in the cell membrane.
Pore (hole) in them through which specific ions can enter or leave cells
Leak channel
An ion channel protein that is in the membrane and has a pore that is always open (e.g., potassium leak channel – only potassium is comfortable using this).
Monovalent cations and divalent cations
Monovalent cations: sodium (Na+) (more in extracellular space), potassium (K+) (more in intracellular space)
Divalent cations : calcium (Ca2+)(more in extracellular space), magnesium (Mg2+)(more in intracellular space)
What are the two proteins are responsible for setting up and maintaining the resting membrane potential of neurons
Sodium-Potassium transporter
Leak-Potassium Channel
What is Sodium-Potassium Transporter
Requires ATP, concentrates sodium and potassium outside and inside the cell, respectively
Pump Na+ atoms out of the cell and K+ atoms in.
Concentration gradients
K+ ions to be 30x more concentrated inside the cell than out
Na+ ions to be 15x more concentrated outside the cell than in.
These concentration gradients never change, ever, unless the cell dies
Membrane potential = 0 (no electrical charge difference)
What is a Leak-Potassium Channel?
Always open, the number of these channels largely determines the resting membrane potential
The cell membrane of neurons contains K+ leak channels, which are selectively permeable to K+.
If K+ was the only ion that could cross the membrane, the electrical potential of the membrane would settle at -90 mV, because this is when the force of diffusion encouraging K+ to leave is equal and opposite to the electrostatic pressure driving K+ in.
The resting membrane potential of most neurons is less negative than -90 mV because other ions can move across the membrane through other types of leak channels.
The more K+ leak channels a neuron has, the more permeable it will be to K+ relative to other ions and the closer its membrane potential will be to -90 mV.
Potassium leak channels are always open. Potassium can always flow through them (in either direction).
What are the three Proteins (Voltage-gated ion channels) that the action potential involves?
Voltage-gated sodium channel
Voltage-gated potassium channel
Voltage-gated calcium channel
What is the Voltage-gated sodium channel?
To initiate and propagate the action potential
These ion channels are found all over the axon, along its entire length.
Open – The gate opens whenever the membrane potential becomes less negative than -40 mV. The initial cause of this depolarized state is usually the activation of receptor protein ion channels that let in sodium
Have electrical charges on their doors, such that they open or close when the charge difference across the membrane is greater or smaller than some number
What is the Voltage-Gated potassium channel?
To restore the resting membrane potential
Ending the Action Potential
Voltage-gate K+ channels open when the membrane potential is more positive than 0 (no difference in charge between inside and outside of the cell).
The opening of the voltage-gated K+ channels helps bring the membrane potential back down to -70 mV
Voltage-gated potassium channels open in the middle of an action potential, when the membrane potential is around 0 mV.
What is the Voltage-gated calcium channel?
Located in the axon terminal, triggers the release of neurotransmitters
Synaptic transmission
Voltage-gated calcium channels open when the axon terminal becomes depolarized (i.e., in response to an action potential).
Calcium is 1000x more concentrated outside the cell than in.
The calcium that enters through these channels activates vesicle release machinery
When an action potential reaches the end of an axon (the axon terminal), it causes voltage-gated calcium channels to open. The influx of calcium into the axon terminal triggers the release of signaling molecules (neurotransmitters) into the synapse.
What is diffusion?
If there is a concentration gradient and no forces or barriers to prevent free movement of molecules, then molecules will move, on average, from regions of high concentration to regions of low concentration
Balancing Diffusion and Electrostatic energy
Neuronal membranes are filled with K+ leak channels. Given the ability to travel freely, K+ ions leave the cell on account of the force of diffusion
What are receptors?
All cell membranes are full of proteins that act as sensors (receptors). These proteins are sensitive to specific features of the extracellular environment.
For example, cells use proteins to detect and pull in nutrients from the extracellular space. (Nutrients include proteins, fats, sugars, vitamins and minerals.)
Neurons put receptor proteins on their dendrites to sense the external world.
What are sensors for detecting?
The presence of certain molecules (e.g., neurotransmitters)
Physical pressure (movement, touch)
Electrical pressure (voltage)
Temperature
pH (acidity, basicity)
Electromagnetic radiation (light)
What is depolarization?
Membrane potential of a cell becomes less negative than it normally is at rest
When positive sodium ions enter a cell through a receptor protein ion channel, they might depolarize a neuron from -70 to -60 mV
If this happens – they immediately close back up
Potassium leak channels are always open - potassium can flow in either direction through them
Action Potential
The opening of one Na+ channel allows Na+ ions to rush in, propelled by both diffusion and electrostatic forces.
This influx of Na+ depolarizes the membrane further, which in turn causes additional voltage-gated Na+ channels to open.
Soon there is an avalanche effect as all voltage-gated Na+ channels open causing the membrane potential to shoot up to +40mV
At the peak of the action potential, the membrane potential is +40 mV. All voltage-gated Na+ channels are now inactivated.
When voltage-gated potassium ion channels open, the outflow of K+ ions driven now by diffusion and electrostatic forces restore the resting membrane potential in about a millisecond.
What is the threshold for excitation?
The value of the membrane potential that must be reached to produce an action potential
What is synaptic transmission?
transmission of messages from one neuron to another via the release of signaling molecules (neurotransmitters) into the synapse. These signaling molecules activate receptor proteins on downstream neurons
What is a promoter
Region of DNA that initiates transcription of a particular gene
They indicate what kind of cells should read the gene and when
Typically located just before the gene
What are Neuroglia – or Glial Cells
Found al around neurons and physically encapsulate some parts of them
They help traffic nutrients and maintain molecular (ionic) stability in extracellular space
Support any functions of the Nervous system
Glial : Neuron = between 2:1 and 5:1
What is the glial cell astrocyte?
Glial cell providing physical support and cleans up debris in the brain through phagocytosis
Control chemical composition of surrounding environment and help nourish neurons
What is the glial cell microglia?
Smallest of glial cells
Provide immune system for the brain
Protect the brain from invading microorganisms
What is the glial cell oligodentrocyte?
Produce the myelin sheath that encapsulate axons
Sheath is a series of segments – not continuous
Exposed axon – Node de Ranvier
During the development of the CNS, oligodendrocytes form processes shaped something like canoe paddles
Each of the paddle-shaped processes then wraps itself many times around a segment of an axon and, while doing so, produces layers of myelin that make up part of the axon’s myelin sheath.
what is Saltatory conduction
The conduction of action potentials by myelinated axons
Action potential appears to jump from one Node of Ranvier to next – at each one the strength of the signal is regenerated with additional voltage-gated Na+ channels
Slow processing of pain and temperature
What is the impact of myelination
The only place where a myelinated axon comes into contact with extracellular fluid is at nod of Ranvier, where the axon is naked
In myelinated areas there are almost no ion channels and those that are there are of no consequences because there is no extracellular fluid outside the membrane
What are synapses/
Junction between axon terminal of the sending neuron and the cell membrane of the receiving neuron
Communication across the synapse is achieved by the release of a molecule from an axon terminal
What are neurotransmitters?
A molecule that can have a simple excitatory or inhibitory effect or a complex modulatory effect on the receiving neuron.
Synaptic vesicle
Contain molecules of neurotransmitter. They attach to the presynaptic membrane and release neurotransmitter into the synaptic cleft
synaptic cleft
The space between the pre- and postsynaptic membranes. It is filled with an extracellular fluid.
pre-synaptic membrane
The membrane of the terminal button (the sending cell). This is where neurotransmitter is released from.
post-synaptic membrane
The membrane of the receiving cell that is opposite the axon terminal.
What is electron microscopy
Allows us to see small anatomical structures (e.g. synaptic vesicles and details of cell organelles) using a special electron microscope.
What are ligands
Signaling molecules that bind to protein receptors
Most cell signaling and cell communication occurs through ligand-receptor interactions.
What are ionotropic receptors? (Neurotransmitter receptors)
ion channels
What are metabotropic receptors? (Neurotransmitter receptors)
G protein coupled receptors that can open ion channels through an intracellular signaling cascade.
Receptors can be found on the cell membrane (surface receptors) or inside the cell (intracellular receptors).
where are post-synaptic receptors located
on postsynaptic membrane
where are pre-synaptic receptors located
on presynaptic membrane.
where are extrasynaptic receptors located
near to but outside the synapse
Comunication between neurons
ligands
binding sites
post-synaptic receptor
ligand-gated ion channel/ionotropic receptor
what is a ligand
General term for a signaling molecule (chemical) that binds to the binding site of a receptor. Neurotransmitters are ligands
what is a binding site
Location on a receptor protein to which a ligand binds
what is a post-synaptic receptor
Receptor protein in postsynaptic membrane of a synapse that contains a binding site for a neurotransmitter
what is a Ligand-gated ion channel/Ionotropic receptor
A receptor that is an ion channel. The ion channel opens when the ligand (e.g., the neurotransmitter) binds to it
what is Enzymatic deactivation
Destruction of a neurotransmitter by enzyme after its release (example: destruction of acetylcholine by acetylcholinesterase
what is reuptake
Reentry of a neurotransmitter just liberated by a terminal button back through its membrane, thus terminating postsynaptic potential
what is a postsynaptic potential (Excitatory vs. Inhibitory)
Alterations in the membrane potential of a postsynaptic neuron, produced by neurotransmitter release into the synapse and receptor activation.
Excitatory – influx of positive sodium ions depolarize the cell
Inhibitory – influx of negative chloride ions hyperpolarize the cell
what is depolarization
Less negative than normal
Excitatory
When the membrane potential of a cell becomes less negative than it normally is at rest
influx of positive ions (Na+) can depolarize a neuron from -60 to -50 mV
what is hyperpolarization
Less positive than normal
Inhibitory
When the membrane potential of a cell becomes more negative than it normally is at rest
influx of negative ions such as Cl- can hyperpolarize a neuron from -60 to -70 mV
what is EPSP
Excitatory postsynaptic potential (EPSP)
Excitatory depolarization of postsynaptic membrane caused by neurotransmitter binding to a postsynaptic receptor protein.
Mediated by receptor proteins that open ion channels permeable to sodium. (Making the membrane more permeable to sodium will depolarize the cell.)
Brief depolarization of the membrane potential, typically caused by neurotransmitter activation of ionotropic receptors that let in positively charged sodium ions.
What is IPSP
Inhibitory postsynaptic potential (IPSP)
Inhibitory hyperpolarization of postsynaptic membrane caused by neurotransmitter binding to a postsynaptic receptor protein.
They are mediated by receptor proteins that open ion channels permeable to chloride (Making the membrane more permeable to chloride will hyperpolarize the cell.)
Brief hyperpolarization of the membrane potential, typically caused by neurotransmitter activation of ionotropic receptors that let in negatively charged chloride ions
What is neural integration
The interaction of the excitatory and inhibitory synapses on a particular neuron
When EPSPs and IPSPs occur at the same time, the influx of negatively charged chloride ions diminish the impact of the positively charged sodium ions. IPSPs decrease the likelihood that the cell will fire.
What is a postsynaptic potential
Can be depolarizing or hyperpolarization
Receptor – determines the direction of the postsynaptic potential
Ex. Some serotonin receptors sauce exhibitory and others cause inhibitory potentials
what is an ionotropic receptor
A neurotransmitter receptor that is an ion channel.
The properties of the pore of the ion channel (the hole) will determine if it causes EPSPs or IPSPs (i.e., if it lets in sodium or chloride ions)
what is a receptor protein
Protein that is sensitive to and capable of communicating some signal.
what is an ionotropic receptor protein
Neurotransmitter binds and can change shapes to accept/bind
Turn towards IONS to mediate their effect
A receptor protein that is an ion channel.
The properties of the pore of the ion channel (the hole) determine if it will produce EPSPs or IPSPs (i.e., if it lets in sodium or chloride ions).
The direct effect of ionotropic receptor activation is always an immediate change in the permeability of the membrane to specific ions (i.e., whatever ions pass through the receptor).
what is an metabotropic receptor protein
Proteins but not ion channels – they also change shapes but they don’t have automatic reaction like the ionotropic receptors
Turn towards METABOLISM to mediate their effect
A receptor protein that is not an ion channel. These receptors typically trigger an intracellular signaling cascade that involves g proteins, which can produce a variety of cellular effects such as a change in gene expression or the opening/closing of g protein-gated ion channels. The effects of metabotropic receptor signaling can be quite large, but they are often delayed (because they rely on signaling cascades and diffusion).
Metabotropic receptor activation can cause the opening of many ion channel
what is a g protein
G proteins are a family of intracellular proteins that are involved in intracellular signaling cascades.
All G protein coupled receptors are METABOTROPIC
“G proteins” are proteins that use GTP molecules instead of ATP molecules for their energy to perform chemical reactions
what happens when a g protein binds to GTP
it turns it “ON” and can trigger chemical reactions
A g protein turns GTP into GDP. This process turns the protein “OFF”
G proteins have a hard time letting go of GDP
how do they do it?
They do so by finding an activated metabotropic receptor and use the intracellular side of an activated metabotropic receptor to pry off their GDP molecule.
After prying off the GDP molecule, they bind to another GTP molecule and the process starts over again
What is a g protein-gated ion channel and how does it work
Some ion channels are gated by g proteins. They all use the GTP molecule for energy.
Generalized illustration of a metabotropic GPCR receptor causing ion channel opening
Neurotransmitter binds to a metabotropic receptor.
Activated g proteins transmit the message intracellularly.
Some ion channels are gated (directly or indirectly) by activated g proteins.
G protein signaling cascades can affect multiple downstream processes including
opening g protein gated ion channels
changes in gene transcription
secretion of substances from the cell
really anything the cell wants.
Where do synapses form
Between axon terminals
Dendrites (dendritic shafts) - cause action potential
Dendritic spines – cause action potential
The soma (cell body) - cause action potential
Other axon terminals (axoaxonic synapses)
What are axoaxonis synapses
Regulate amount of neurotransmitter that the second neuron will release when it has an action potential
what is presynaptic inhibition
Axoaxonic synapse can HYPERPOLARIZE the axon terminal of the downstream neuron, so that its voltage-gated calcium channels WILL NOT OPEN at all or for very long when an action potential arrives.
The net effect is to REDUCE neurotransmitter release from the red cell when it has an action potential.
what is presynaptic facilitation
Axoaxonic synapse can DEPOLARIZE the axon terminal of the downstream neuron, so that its voltage-gated calcium channels are MORE LIKELY TO OPEN when an action potential arrives.
The net effect is to INCREASE neurotransmitter release from the red cell when it has an action potential.
what are autoreceptors
A receptor located on presynaptic membrane that gets activated when the cell releases its own neurotransmitter.
They are gated by the neurotransmitter that the cell releases.
They are generally metabotropic and inhibitory.
Main source of presynaptic inhibition.
what is a post-synaptic receptor
A receptor located on the receiving neuron (the one that is not releasing the neurotransmitter).
Anatomical directions
neuraxis
anterior
posterior
superior
inferior
rostral
caudal
dorsal
ventral
lateral
medial
transverse plane
sagittal plane
horizontal plane
Neuraxis – imaginary line that runs along the length of the CNS
Animals and Human head
Anterior – in front
Posterior – behind
Superior – above
Inferior – below
Rostral – towards the beak
Caudal – towards the tail
Dorsal – towards the back
Ventral – towards the belly
Human spinal cord
Lateral – away from the midline
Medial – towards the midline
“Geography” of the brain
Transverse plane (frontal section, cross section, coronal section)
Sagittal plane – A mid-sagittal cut means the exact middle (between the eyes)
Horizontal plane – looking down at horizontally cut brain
Contralateral
Ipsilateral
Superfacial
Deep
Proximal
Distal
Brain Nuclei
Contralateral – structures on the opposite side of the body
e.g., the motor cortex controls movements of the contralateral hand.
Ipsilateral – structures on the same side of body
e.g., taste information is processed ipsilaterally, which means that taste receptors on the left side of your tongue are processed by your left cerebral hemisphere. Taste and smell are the only sensory systems that do not have contralateral organization.
Superficial – located close to the surface, close to the exterior of the animal
Deep – located far away from the surface, deep in the interior of the animal
Proximal – nearby
Distal – far away
Brain nuclei – in the brain, the word nuclei means a collection of neurons that are clustered together that all work together to serve some function.
E.g., there are many different brain nuclei in the hindbrain. One controls breathing, another controls vomiting, etc.
Central Nervous Systen
CNS
Everything in the brain AND spinal cord
Myelin created by oligodendrocytes
A neuron located in the CNS is considered an interneuron
Interneuron is only used for CNS neurons whose axon STAYS LOCAL (it only makes synapses on nearby neurons).
The term projection neuron to used when the axon of a cell goes outside the area where its soma is located
Peripheral Nervous system
PNS
Any part of the nervous system outside the brain and the spinal cord
Myelin created by Schwann Cells
PNS communicates with the rest of the body with NERVES (cranial and spinal nerves)
Axons of motor neurons:Efferent or Afferent? (What does that mean)
EFFERENT fibers – fibers that bring information AWAY from (the CNS), the OUTPUTS
Motor neurons control muscle contraction and gland secretion. The soma of motor neurons is located within the spinal cord (the CNS).
Axons of sensory neurons: Efferent or Afferent? (What does that mean)
AFFERENT fibers – fibers that bring information TOWARDS… (the CNS), the INPUTS.
Sensory neurons detect changes in the external and internal environment. They send this information to the CNS.
These nerves are part of PNS, which sends sensory information to the CNS and effector information away from the CNS (targeting muscles and glands throughout the body). How many are there
31 pairs of spinal nerves attach to the spinal cord (like 1 pair per vertebrae)
12 pairs of cranial nerves attach to the ventral surface of brain
What is the job of cranial nerves
All the cranial nerves (except the 10th) serve sensory and motor functions of head and neck region
