Exam I Flashcards
Neuroanatomical Division:
Saggital
Neuroanatomical Division:
Horizontal
Neuroanatomical Division:
Coronal
Neuroanatomical Division:
Anterior/Rostral
The frontal section of the brain closest to the face, nose, and mouth.
Neuroanatomical Division:
Posterior/Caudal
The rear section of the brain closest to the back of the head.
Neuroanatomical Division:
Superior/Dorsal
The upper section of the brain closest to the top of the head.
Neuroanatomical Division:
Inferior/Ventral
The lower section of the brain closest to the neck.
Types of Neurons: Monopolar
a neuron from which only a single process leaves the cell body; this single process then divides close to the cell body into a trunk to supply the branching dendrites for incoming signals and an axon for outgoing signals
Types of Neurons: Bipolar
a neuron from which two processes leave the cell body; in this neuron, the dendritic tree emerges from one end of the cell body, while the axon emerges from the opposite end; the dendritic branching of bipolar neurons is typically limited, and the axons of such neurons are usually short in length
Types of Neurons: Multipolar
a neuron from which multiple branches leave the cell body; the many dendrites of the multipolar neuron allow for extensive integration of information coming from many other neurons; the axons of such neurons are usually long, allowing this integrated information to affect distant regions of the nervous system
True or False:
Neurons make up the majority of the cells in the brain
False. Glia make up most of the cells in the brain.
True or False:
Microglia have similarities to macrophages
True. Microglia can phagocytose pathogens.
Why are bullet wounds to the brainstem so often fatel, whereas bullet wounds to the frontal lobe of the cerebral cortex can often be survivable?
- Brainstem controls respiration
- Frontal lobe controls motor planning and complex behavior.
Which kind of glial cell is involved in potassium uptake around neuronal axons
Astrocyte.
What is the function of oligodendrocytes?
Myelin formation in the central nervous system.
Cajal stated the “Principle of Dynamic Polarization.” What did this principle assert?
This asserted that information flows from dendrites to nerve terminal via the axon.
What method or technique would you use for measuring the individual responses of 50 neurons simultaneously?
Multi-electrode Method or Dye Method
What method or technique would you use for showing that the cerebral cortex has layers where neuronal cell bodies are in high density
Nissel Stain
What method or technique would you use for demonstrating that the protein actin is localized at the tip of a growing axon?
GFP tag or antibody labeling.
What method or technique would you use for measuring the membrane potential of a living cell?
Intracellular electrode, Voltage-Sensitive Dye
Why does fMRI take much longer than magnetoencephalography (MEG) to localize neuronal activity to a particular region of the brain?
Because it detects blood flow charges, not electrical activity directly.
In the knee-jerk response reflex, the flexor muscle reflex, how many neurons are involved in the pathway that mediates this relaxation and what are they called?
- Sensory Neuron
- Interneuron
- Motor Neuron
Fill in the blanks:
A voltage clamp is a circuit that measures ____________ while keeping the _______________________ at a fixed value that the experimenter determines.
A voltage clamp is a circuit that measures CURRENT while keeping the MEMBRANE POTENTIAL at a fixed value that the experimenter determines.
The sodium ion concentration outside a squid giant axon is 435 mM whereas the sodium ion concentration outside a mammalian axon is 100 mM. Despite this difference, the maximum peak amplitude of action potentials in both axons is the same, about +50 mV. Explain why the greater external sodium concentration outside a squid axon does not lead to a greater peak amplitude of the squid axon’s action potential. In your explanation you must refer to specific equation(s) that describe the relationship between ion concentrations and the forces that move ions across a membrane.
- [Na+]I is also greater inside a squid axon than inside a mammalian axon.
- Keeping in mind the Nernst Equation (ENa = RT/F ln(Co/Ci), the ratio is the same for the squid and the mammal.
- If ENa is the same, than the peak of the action potential will also be the same.
A neuronal membrane contains only voltage-gated calcium channels and leakage chloride channels. Draw the LABELED circuit model for the membrane. You must show which side of the battery is positive.
There needs to be:
- Cm to show the capacitor of the membrane
- ECl with the negative side on the opposite side of the resistor for chloride
- ECa with the positive site on the opposite side of the resistor for calcium
- GCl next to the positive terminal for ECl
- GCa next to the negative terminal for ECa
You are investigating a neuron that has a resting potential of around -80 mV, rather more negative than usual. You suspect that the neuron’s leakage ion channels (which determine its resting potential) are much more permeable to potassium ions than to chloride ions. Briefly describe an experiment (method, results, conclusion – with labeled graphs if you want) that would allow you to verify this suspicion. You can isolate the neuron and alter the composition of the saline solution surrounding it and you can impale it with a single micropipette and measure Vm
- Impale neuron with the micropipette and measure Vm
- Increase [K+]o to various levels to measure the Vm at each level of [K+]o
- Plot Vm vs log[K+]o
- If slope approaches 58 mV/10 x [K+]o, then Vm follows Ek and cell is mostly permeable to K+
- Repeat with [Cl-]o—Vm should not change much with [Cl-]o and should not follow ECl
Explain in terms of the forces that move ions why the action potential never exceeds +60 mV?
+60 mV is ENa and at ENa, the positive Vm repels any more net Na+ influx and so Na+ influx slows down and stops and so Vm reaches ENa but does not depolarize further and equilibrium is reached.
Principal of Dynamic Polarization
- Information flows in a consistent way in each neuron
- From dendrites to nerve terminals via axons
Principal of Connectional Specificity
- NO cytoplasmic connection between neurons
- Nerve cells do NOT form random networks
- Each cell makes precise connections with neurons via synapses
Glial Cell Functions
- Regulate environment around nerve cell
- Take up NTs released from nerve terminals
- Defend the brain and/or spinal cord from injury or infection
- Can direct neuronal growth
- Glial Stem cells can proliferate and differentiate into new glial cells, or sometimes into new neurons
- 10 to 50 times more glia than neurons in BRAIN
Microglial Cells
- Found in CSF and CNS
- Small, motile phagocytic cells (like macrophages)
- Can engulf particles following injury
- Can secret signaling molecules that modulate inflammatory response (cytokines)
- Mobilized after damage (# microglia increase at injury site)
Astrocytes
- Macroglial cells
- Starbursts
- NOT motile
- Take up potassium around active neurons
- NT removal around active synapses
- “Glial scaffold” to guide axons to target cells in development
- Part of blood, brain barrier
Oligodendrocytes
Responsible for myelination in the CNS
Schwann Cells
Responsible for myelination in the PNS
Glial Stem Cells
- Undifferentiated glial stem cells in the brain and elsewhere can proliferate and differentiate into new glial cells and in very few places, new neurons
- Subclass: oligodendrocyte precursor cells, which differentiate into new oligodendrocytes
Nissel Stain
- Labels ER in neuronal cell bodies
- Shows division of parts of CNS into layers due to differing cell densities
- Good for distinguishing tissues and layers within NS
- Does NOT distinguish individual neuronal types well
- Does NOT stain axon and dendrite patterns
Golgi Stain
- Randomly stains few whole individual cells in a tissue entirely
- Shows axon and dendritic branching
Knee-jerk Response
- Hammer tap stretches tendon, which stretches sensory receptors in leg extensor muscle
- Sensory neuron synapses with and excites motor neuron in spinal cord
- Sensory neuron also excited interneuron
- Interneuron synapse inhibits motor neuron to flexor muscles
- Motor neuron conducts AP to synapses on extensor muscle fibers, causing contraction
- Flexor muscle relaxes because the activity of its motor neurons has been inhibited and leg extends
Graded Potentials
- Changes in potential that precede APs and which are NOT all-or-nothing
- Amplitude of graded potential increases with increasing stimulation
- Graded potentials modulate the rate of APs in the neurons where they occur (can TRIGGER APs)
Computerized Tomography (CT)
- 3D xray image produced using an xray camera and source that rotates arounf the aptient’s head
- Computer reconstructs 3D image from scans
- Anatomical, NOT functionals
Magnetic Resonance Imaging (MRI)
- Detects energy emitted by spinning hydrogen nuclei in water molecules, lined up in a strong magnetic field, that are irradiated by a brief radiofrequency pulse
- Image is based on distribution of water in different tissues and the characteristics of the energy emitted by hydrogen nuclei in different tissues
- High resolution
- Anatomical, NOT functional
Functional MRI (fMRI)
- Hemoglobin slightly distorts the MRI resonance properties of nearby hydrogen nuclei (depends on if Hb is loaded with O2)
- Enables detection of active areas of the brain: areas locally supplied with increased blood flow containing oxygen-rich Hb
- Takes seconds for blood supply through microvasculature to increase in response to activity
- Spatially accurate
- Slow
Positron-emitting Tomography (PET scans)
- Incorporate positron emitting atoms into molecules such as glucose or oxygen (15 O or 11 C)
- Inject labeled oxygen or glucose into the bloodstream and they will enter brain
- Detect emitted positrons with scanning detectors
- Reconstruct location and density of labeled oxygen or glucose
- Active areas of the brain will show increased oxygen or glucose levels
- Slow, poor resolution and need on-site cyclotron
Electro-encephalography (EEG)
- Arrays of electrodes placed on patient’s scalp
- Detect minute electrical potential waves flowing between points on scalp (due to currents flowing through active brain tissues beneath)
- Can be used to characterize gross functional state of brain (sleep/ awake)
- Can detect “Activity” in gross areas of cortex
SQUID-MEG
Superconducting Quantum Interference Device Magneto-encephalography
- As neurons generate electrical impulses, they generate magnetic fields
- Intensity and shape of fields varies with electrical activity within an area of brain
- Magnetic fields can be detected with SQUID and a 3D image formed
- Very rapid, poor localization
Peripheral Nervous System
- Sensory neurons, sensory axons, motor neuron axons
- Divided into autonomic and somatic divisions
- Includes cranial and spinal nerves (nerve = sensory and motor neuron axons)
Brainstem
- Respiratory centers, control of movement
- Pons, medulla, midbrain
Cerebellum
- Control of fine movement
Diencephalon
- Contains thalamus and hypothalamus
- Thalamus: Sensory information processing
- Hypothalamus: Hormonal control
Corpus Callosum
- Tracts of white matter linking the cerebral hemispheres
Occipital Lobe
- Located at back near brainstem
- Vision
Parietal Lobe
- Located in middle
- Somatosensation (heat, cold, light)
Frontal Lobe
- Located at front
- Motor planning
Temporal Lobe
- Located “underneath”
- Hearing
Basal Ganglia
- Motor planning
- Includes
- Caudate
- Putamen
- Globus pallidus
Cerebral Cortex
- Outer layer of brain
- Grey matter
Hippocampus
- Memory
Amygdala
- Emotional balance
Ventricles
Spaces containing cushioning CSF
Principle of Electroneutrality
- Positive and negative particles or ions in a substance are evenly distributed so that the overall charge at any one point is zero
- Ex. In NaCl, # Na = # Cl
Kirchoff’s First Law
Two points in a circuit that are connected together without resistance are always at the same voltage
Kirchoff’s Second Law
The sum of all voltage drops across a series of resistances in a circuit loop is equal to the sum of all battery voltages in that loop
Neuron as Circuit
Ion channels = resistors coupled in series to batteries
- Resistors rep pores through which ions flow
- Batteries rep the driving force forcing ions through pores
Lipid bilayer = capacitor
- Lipid head groups act as two conducting sheets of material separated by a thin layer of insulating material (hydrophobic core of membrane)
- Able to store separated charge on membrane surface
Permeability and Action Potentials
- At rest, membrane is mostly permeable to K+ ion making resting potential near the potassium equilibrium potential (-60 to -70 mV)
- During AP, large increase in Na permeability overwhelms the resting K permeability and membrane becomes mostly permeable to Na. Membrane potential driven toward Na equilibrium potential (+58 mV)
- Subsequent decline in Na permeability and increase in K permeability restores resting membrane potential
Voltage Clamp
- Device that allows you to clamp the membrane potential at a desired value and measure the summed ionic current across the membrane
- Allows calculation of conductances
i = g (Vm - E)
- Measure i by isolating with TEA/TTX
- Measure Vm with voltage clamp
- Estimate E with ion concentrations
Our visual system can recognize a scene faster than a small computer equipped with a digital camera because………
Thousands of neurons process information about each part of the image simultaneously
In the stretch reflex, the sensory signal is transmitted from the skin to the spinal cord by a graded potential change in the axon of the sensory neuron. True or False?
False. The signal is transmitted by an action potential change in the axon of the sensory neuron.
Why is the use of calcium-sensitive fluorescent proteins to monitor brain activity an invasive technique - one that often requires surgery on the animal from which the activity is recorded?
Because you have to measure the protein’s fluorescence
Which of the the following has the best time resolution for recording neuronal activity in areas of the brain
- fMRI
- PET
- MEG
- multi-electrode recording
(4) Multi-Electrode Recording
The basal ganglia are rostral to the cerebellum. True or False?
True.
Electrical current moves through solutions very quickly because the ions that carry it move close to the speed of light. True or False?
False.
Which of the following is the most conclusive and totally definitive way to show that the early voltage-gated inward current is carried by sodium ions?
- Voltage clamp the axon, add TTX and show that the current is abolished
- Voltage clamp the axon, remove extracellular sodium and show that the current reverses
- Remove extracellullar sodium and show that the action potential is abolished
- Voltage clamp the currents and show that the early current is inward
(2) Voltage clamp the axon, remove extracellular sodium and show that the current reverses.
Labeling and staining neurons and glia to show their structure and to distinguish different types (4)
- Antibody labeling of proteins expressed only by that type of neuron
- In-situ hybridization to mRNA’s expressed only by that type
- The “tagging” of proteins expressed only by a specific neuronal type with a fluorescent protein label (GFP) in genetically engineered organisms
- The application of enzyme substrates that produce colored products in type of neurons that express that enzyme
Locate:
- Precentral Gyrus
- Brainstem
- Cerebellum
- Spinal Cord
Locate:
- Corpus Callosum
- Diencephalon
Locate:
- Frontal Lobe
- Occipital Lobe
- Parietal Lobe
- Temporal Lobe
Locate:
- Basal Ganglia
- Thalamus
- Hippocampus
- Fornix
