Exam I Flashcards
Name and describe the four different types of glial cells.
S-O-M-A
- Schwann cells: myelination in PNS
- oligodendrocytes: myelination in CNS
- microglia: immune defense
- astrocytes: structural support, maintain chemical balance, vital to blood-brain barrier
What is the importance of astrocytes for blood-brain barrier?
- B-B barrier works as a gatekeeper deciding what gets into brain
- blood vessels are covered with the “feet” of astrocytes, so anything in the blood must go through the protective astrocyte layer in order to reach the neuron
- they are not only gatekeepers but also a mop-up crew and storage unit for leftover substances (ions, neurotransmitters, etc.)
- also help with nutrition
Which glial cells produce myelin?
Schwann cells - PNS
oligodendrocytes - CNS
What constitutes white and gray matter in the brain?
gray matter: cell bodies (middle)
white matter: axons (outer layer)
XDefine what a potential is
How does a neuron fire action potential?
- A neuron begins at rest
- Inputs (changes in voltage) stimulate it
- If large enough stimulus at axon hillock, an action potential is created
- Action potential propagates down axon
- Sends signal to other neurons
How do changes in voltage lead to summation?
can occur through temporal and spatial summation
(temporal: signals arrive at same time, spatial: signals arrive at different dendritic branches and converge in soma)
these small voltage changes are collected in dendrites and travel to soma
Describe the process of summation in regard to excitatory and inhibitory postsynaptic potentials.
normally inside of cell is negative (-65 mV)
depending on ion charge and direction flow, the movement of ions across the membrane can make this potential difference smaller or larger
when positive ions, such as sodium, flow into the cell, the potential difference becomes smaller/less negative (depolarizing cell via EPSP)
when negative ions, such as chloride, flow into cell or positive ions, such as potassium, flow out of cell, the potential difference becomes larger/more negative (hyper polarizing cell via IPSP)
Name and define key cations and anions
Name the key cations and anions that are involved in maintaining resting potential,
firing action potentials and facilitating neuron communication
cations: positive
- potassium (K+)
- sodium (Na+)
- calcium (Ca2+)
anions: negative
- chloride (Cl-)
Describe two forces action on ions.
- Diffusion
- high concentration to low
- K+ wants to go out, Na+ wants to come in - Electrostatic Pressure
- opposite charge
- an ion that is on a side of a membrane where the charge is the same (e.g., positive with positive) will be propelled by a force to the other side, if the membrane is permeable
- K+ is positive, so wants to go into negative cell
- Na+ is positive, so wants to go in
What are the three different types of channels?
L—L—V
- leak channels: ion channels specific for Na+, K+, Cl-, as long as the ion fits it will go through, controlled by mechanical force on cell
- ligand/chemically-gated channels: open in response to a ligand (some chemical signal) binding to them/binding of a ligand/chemical to membrane protein
- voltage-gated channels: open in response to voltage (i.e. when the cell gets depolarized/controlled by membrane potential
Describe the relative concentrations of the key ions inside and outside of the cell and the membrane potential of the inside of the cell at rest.
cell at rest = negative (-65 mV)
lots of Na+ outside and lots of K+ inside
Na Na Na Na Na Na Na Na —————- ———— —————— K K K K K K K K K K K
Describe two forces action on ions.
- Diffusion
- high concentration to low
- K+ wants to go out, Na+ wants to come in - Electrostatic Pressure
- opposite charge
- an ion that is on a side of a membrane where the charge is the same (e.g., positive with positive) will be propelled by a force to the other side, if the membrane is permeable
- K+ is positive, so wants to go into negative cell
- Na+ is positive, so wants to go in
Draw a neuron at rest
Na Na Na Na Na Na Na Na —————- ———— —————— K K K K K K K K K K K
Describe the four factors resting potential relies on
D-E-S-S
Diffusion
Electrostatic forces
Selective permeability
Sodium-potassium pumps
Sodium-potassium pump
3 Na+ out, 2 K+ in
Describe the two kinds of input a neuron can receive.
EPSP and IPSP
normally inside of cell is negative (-65 mV)
depending on ion charge and direction flow, the movement of ions across the membrane can make this potential difference smaller or larger
when positive ions, such as sodium, flow into the cell, the potential difference becomes smaller/less negative (depolarizing cell via EPSP)
when negative ions, such as chloride, flow into cell or positive ions, such as potassium, flow out of cell, the potential difference becomes larger/more negative (hyperpolarizing cell via IPSP)
Describe soma summation.
normally inside of cell is negative (-65 mV)
depending on ion charge and direction flow, the movement of ions across the membrane can make this potential difference smaller or larger
when positive ions, such as sodium, flow into the cell, the potential difference becomes smaller/less negative (depolarizing cell via EPSP)
when negative ions, such as chloride, flow into cell or positive ions, such as potassium, flow out of cell, the potential difference becomes larger/more negative (hyperpolarizing cell via IPSP)
—-
excitatory and inhibitory postsynaptic potentials will add up like a simple math equation
- two EPSPs will sum into a larger voltage change
- an IPSP and an EPSP arriving at the same time will cancel each other out
- the total voltage of the cell is determined by the overall pattern of incoming signals
- if the number of excitatory signals overwhelms the number of inhibitory signals, the voltage will be driven to more positive values, therefore making the cell increasingly depolarized
- if the number of inhibitory signals overwhelmed the number of excitatory signals, the voltage will be driven down, therefore making the cell increasingly hyperpolarized
- if the cell voltage reaches a threshold of (-60 mV), an action potential is generated at the axon hillock
Characteristics of action potential
- all-or-none
- self-perpetuating (once it starts, it keeps going)
- self-limiting (signal doesn’t travel backwards)
Draw an action potential
-drawing-
What is happening during refractory period?
requires a brief refractory period where channels are inactivated (it takes a bit of time to reset the mousetraps)
Action potential proportion down myelinated vs. unmyelinated axon
saltatory vs. continuous conduction
Importance of Nodes of Ranvier
the length of the Nodes of Ranvier is just the right size to allow for the depolarization at one node to be large enough to open the Na+ ion voltage gated channel at the next node
Rate coding
average rate of neural firing over some portion of time
number of action potentials in a window of time
electrical vs. chemical synapse
electrical synapse: “gap junction,” the membranes of two neurons are continuous at tiny spots, making the cells electrically contiguous; allow for even more rapid communication.
chemical synapse: communication via chemical messengers known as neurotransmitters
Describe the neuron doctrine and how it differed from other ideas about what the brain
was actually composed of.
neural doctrine based on Golgi’s stain and Cajal’s histological studies
discovery that neurons were discrete, fundamental units of the nervous system
Golgi’s reticulum theory: single continuous network
nervous system is made up of discrete individual cells
serotonin
neurotransmitter, produced in raphe nuclei of brainstem, mood regulation
dopamine
neurotransmitter, produced in substantia nigra, monoamine, reward system
epinephrine
adrenaline, fight-or-flight
norepinephrine
arousal, alertness
acetylcholine
discovered by Loewi, causes muscle contractions, EPSP in PNS
GABA
IPSP
glutamate
most common EPSP in CNS
synapse with calcium channels
draw
big picture neuron communication
write
two types of receptors
ionotrophic: cause direct flow of ions
metabotrophic: cause cascade of signals
how does neuron communication stop
APs stop firing
Voltage-gated calcium channels close
Calcium concentration inside cell decreases
Vesicles stop fusing with presynaptic membrane
Neurotransmitter no longer released
3 ways leftover neurotransmitters are cleared from synapse
- Diffusion: neurotransmitter can passively diffuse out of synaptic cleft
- Enzymatic degradation/deactivation: enzymes in synapse can break down neurotransmitter
- Active transport: reuptake pumps in synaptic membrane can bring neurotransmitter back into axon terminal and recycle it:
Define an agonist and antagonist
agonist: extend neurotransmitter activity
antagonist: decrease neurotransmitter activity
Describe the four types of channels we’ve discussed
- leak channels: ion channels specific for Na+, K+, Cl-, as long as the ion fits it will go through, controlled by mechanical force on cell
- ligand/chemically-gated channels: open in response to a ligand (some chemical signal) binding to them/binding of a ligand/chemical to membrane protein
- voltage-gated channels: open in response to voltage (i.e. when the cell gets depolarized/controlled by membrane potential
- light channels: optogenetics
Describe how optogenetics works
researches inset a gene found in algae that is light sensitive
using gene therapy, it is implemented into other organisms and the cells then produce that protein on their surface
when the cells are later exposed to light, channels open up and charged particles rush inside, causing electrical signals to be emitted
goal is to find a way to control light activity in some cells but not in others “on and off”
Name and describe the major divisions of the nervous system: CNS, PNS, Autonomic
Nervous System, Somatic Nervous System
CNS (brain and spinal cord)
PNS (sensory and motor communication)
—>autonomic (involuntary, regulates internal organs)
—> sympathetic (fight or flight)
—> parasympathetic (rest and regenerate)
—>somatic (voluntary, hot plate hand withdraw)
ventral
toward the bottom/belly
venter=belly
dorsal
top/back
rostral
front/mouth
rostrum=beak
caudal
back/tail
caudal=tail
anterior
front
posterior
back
superior
top
inferior
bottom
lateral
side
medial
middel
sagittal
sagittal slice - left and right
midsagittal
slice through exact midline left and right of brain
axial
top and bottom
take knife cut top and botton
coronal
front and back
skull
layers of protection for the brain
protects soft tissue from injury
dura mater
layers of protection for the brain
meninges 1 (outer)
arachnoid mater
layers of protection for the brain
meninges 2 (middle)
pia mater
layers of protection for the brain
meninges 3 (inner)
Describe the functions of cerebrospinal fluid in the brain and broadly identify where the ventricular system is in the brain
Explain how cerebrospinal fluid can be used diagnostically to tell us important things
about the health and functioning of the brain
the four ventricles (cavities) in your brain are filled with cerebrospinal fluid
the ventricles constantly produce cerebrospinal fluid which circulates through the ventricles and over the surface of the brain and spinal cord
shock absorber
it protects the brain from injury and helps to maintain stable chemical environment for neurons
Identify on a diagram: cerebrum, cerebellum, brainstem and constituent areas (midbrain, pons, medulla), spinal cord, thalamus, hypothalamus, pituitary gland, frontal
lobe, parietal lobe, temporal lobe, occipital lobe, central sulcus, precentral gyrus (primary motor cortex), postcentral gyrus (primary somatosensory cortex), corpus callosum
diagram
Broadly describe how the primary somatosensory cortex and the primary motor cortex
are organized
there are different regions dedicated to different areas of the body and they’re mapped out in a specific way and larger areas of the brain are devoted to areas where we need more sensitivity or motor control, e.g., hands and fingers, mouth
Describe some functions of the basal ganglia
sceec
simple and complex movements
eye movements
cognition
reward/evaluation
Describe the limbic system, particularly some of its key components, especially the
hippocampus, amygdala (be able to describe some of the functions of both of those
structures)
concerned with instinct and mood, controls basic emotions and drives
hippocampus: memory, navigation, learning
amygdala: attach emotions to places/events
Define and identify gyri and sulci and broadly describe why the brain is folded this way
gyrus: round, raised areas
sulcus: grooves between gyri
allow the brain to fit large sheet of cerebral cortex into small space
which transmitter is the dorsal raphe nuclei is the main source of
serotonin
which transmitter the substantia nigra is the main source o
dopamine
Describe a role of the periaqueductal gray matter
consists of neurons organized into set of columns that are responsible for survival behaviors such as defense, aggression and reproduction
Describe some functions of the cerebellum
smooth, accurate movements
Describe some functions of the hypothalamus
homeostasis
H-C-A-H-S-H
CASHHH
heat dissipation circadian rhythm appetite/thirst heat conservation satiety hormonal regulation
Define homeostasis, endocrine glands, hormones
when the internal environment deviates too far from norm, hypothalamus coordinates compensatory mechanisms
autonomic (constrict blood vessels)
endocrine (hormone to stop kidneys from secreting water)
behavioral (find water)
Identify on a diagram and describe the role of the corpus callosum and what it consists
of
a broad band of nerve fibers joining the two hemispheres of the brain
reason through where the inferior frontal gyrus is
based on the fact that you know what inferior,
frontal, and gyrus all refer to
know
Reason through what happened in that Radiolab episode when the student took a dopamine antagonist to relieve nausea: What did she experience? What do her symptoms tell us about what area was affected and why?
Remember the student interviewing at grad schools who experienced basal-ganglia- related trouble?
She was taking a dopamine antagonist—which blocked dopamine from binding to receptors in the basal ganglia as it normally would
Describe the relationship between the hypothalamus and the pituitary gland
can stimulate pituitary gland for hormone control
Describe what happened with Mary Lou Jepsen after she had to have surgery to remove
a tumor, which left her without a functioning pituitary gland
, she suffered from a pituitary gland tumor and had it removed and thus lost her pituitary gland, requiring a twice-daily regimen of hormone replacement
Describe what happens in sleep paralysis
The pons contains important neuronal pathways between the cerebrum, spinal cord and cerebellum. In locked-in syndrome there is an interruption of all the motor fibers running from grey matter in the brain via the spinal cord to the body’s muscles and also damage to the centers in the brainstem important for facial control and speaking.
pons—>medulla—>muscles
vivid dreams = protective paralysis
Describe in detail what we think of as the first endocrinology experiment: What were
the methods and findings? What is the significance of these findings?
removed tests, replanted them in abdomen
although testes were removed and put in another place, still had effect on development
conclusion: testes release chemical signal (hormone) that has widespread effects
Explain why the thalamus might be thought of as a switchboard operator – but also why
that analogy may undersell its role a little bit
receives information from all the senses and and routes them
Explain what Nancy Kanwisher means when she likens the brain to a Swiss Army knife. What does this describe about the organization of the brain and the relationship
between structure and function
The brain is not a general-purpose processor, but a collection of specialized components,
Describe the case of H.M. and the lesion evidence from his case
medial temporal lobe
EEG
place electrodesinspecific locationsonthe scalp and record electrical activity of large groups of neurons in each region
high temp, low spatial
strengths: high temporal resolution, relatively direct measure of brain activity, relatively noninvasive
weaknesses: low spatial resolution (different sensitivity to different regions, e.g., fairly insensitive to signals in deep brain)
PET
allows imaging of different types of metabolic activity, e.g., blood, glucose, neurotransmitters
somewhat invasive because involves exposure to radioactive material
Inject radioactive tracer into bloodstream (specific to what you’re interested in) —> radiotracer becomes concentrated in tissues of interest —> tracer decays, producing gamma rays, which are detected by machine —> show areas of greateractivity —> often combined with CT or MRI images to produce brain images
strengths: brain function: measures of metabolic processes; can measure multiple neurotransmitters, glucose, etc., depending on the ligand
limitations: cannot show, more rapid changes in brain activity relatively low temporal and spatial resolution
MRI
MRI can tell us about structure (can give high-resolution images of fluid, fat, bone, etc. and can evaluate tissue density, cortical thickness, size differences,
but not brain activity/function, blood flow, or neurotransmitter activity
fMRI
blood flow, indirect
how/why fMRI uses the BOLD signal
uses blood flow as a proxy for neural activity
Blood Oxygen-Level Dependent (BOLD) signal
Describe how direct brain stimulation works and the strengths and limitations of this approach
Direct brain stimulation
Strengths:
-canstimulate different areas and see how it affects behavior
-patientalready havingsurgery can vary strength of stimulation and see effects
Limitations:
-invasive
-limited to studies in humans who require neurosurgical interventions
-stressof being in OR and/or medications might affect behavior
-timeconstraints limit experimental paradigms
retestingusually not possible
Describe how TMS works and the strengths and limitations of this approach
TMS of primary motor cortex
Strengths:
-canstimulate different areas and see how it affects behavior
-cancause inhibitory and excitatoryeffects
-cancreate short-acting lesions and examine within subject-effects
-can be performed in healthy people
-canbe combined with other imaging (e.g. fMRI)
Limitations:
- notat localized as we might like (typically a large area of the brain isstimulated)
- canonly stimulate areas of the brain near the surface of the skull
Transcranial direct current stimulation (tDCS)
passes weak electrical current through the scalp
Describe – very briefly – how tDCS works and why you shouldn’t try doing it at home
TMS can damage hearing, cause scalp discomfort, spasms and headaches. TDCS can cause a slight itching on the skin during stimulation, dizziness and fatigue.
Explain why we’d want to combine behavioral and brain measures in our studies
Combine BEHAVIORAL andBRAINmeasures to understand how the brain relates to/mediates mental processes
Explain the different types of evidence provided by lesion, correlational, and stimulation
studies
lesion
correlational: provide detailed observations of brain activity accompanying behavior
stimulation: provide a causal link between activity and function
Respond to a friend who says that we have a specific neuron in our brains devoted to recognizing our grandmothers, explaining how this idea of a “grandmother cell” – or a Jennifer Aniston neuron – is a bit problematic
neurons in the human brain that represent concepts
We don’t all have Jennifer Aniston neurons, nor is there one neuron whose sole job is to recognize Jennifer Aniston. (Quiroga says there are likely many neurons that fire in response to the actress, and that this neuron likely also responded to other concepts he didn’t test for.) But the discovery of a neuron that is linked to a particular concept is a major milestone in understanding how the mind works.
Explain what converging evidence is and why it’s important
the principle that evidence from independent, unrelated sources can “converge” to strong conclusions
Be able to generally read and understand a graph depicting temporal and spatial resolution, describe what each type of resolution means, and describe how this information might help you choose one method over another
Temporal resolution (TR) refers to the precision of a measurement with respect to time
Spatial: greater number of pixels
Explain what forward inference is, particularly as it pertains to fMRI. Describe how Nancy Kanwisher’s study of the fusiform face area is a good example of forward inference. Describe some of the drawbacks of forward inference.
forward: given a certain physiological state, can we observe brain activity
reverse: can we infer physiological state given brain activity
Explain what reverse inference is, particularly as it pertains to fMRI. Describe where it’s
appropriate to use and where it is less appropriate and why.
forward: given a certain physiological state, can we observe brain activity
reverse: can we infer physiological state given brain activity
4 brain regions
FPTO
frontal - broca (speech), motor cortex, cognitive activity
parietal - somatosensory cortex, orienting oneself
temporal - behavior and memory
occipital - visual cortex
episodic memory vs. implicit memory
episodic = declarative (conscious recall) implicit = procedural (motor, un-recalled)
retrograde vs anterograde amnesia
anterograde = future retrograde = past events
