Exam 1 Flashcards
basic features of Galen’s model
- the brain is the seat of sensations from the 5 external senses, the site of all mental or psychic functions, and source of voluntary movement
- Sensory function is supported by psychic pneuma flowing from sensory organs to lateral ventricles
- The three psychological functions of the rational soul (imagination, thought, and memory), are accomplished by psychic pneuma refined in the brain ventricles
- Voluntary movement effected by psychic pneuma flowing from fourth ventricle through motor nerves to the muscles
- Regarded the brain as a sort of pump
- Pneumatic-ventricular model was the first system of nervous system functional localization
3 cell theory as described by Nemesius
- The first cell (the right and left lateral ventricles together) subserve association of the 5 basic external cells along with the imagination
- The second cell (our third ventricle) subserves thinking or cognition
- The third cell (our fourth ventricle) subserves memory
- The three basic internal senses - memory, cogitation and imagination - were divided into at least 7 different faculties and then further refined in over 70 different ways
Vesalius’ contribution to neuroanatomy
- Systematically described the body through dissection, to correct previous errors, and to illustrate the body with best artistic methods
- Paid attention to the brain structure and the ventricular system but was careful not to speculate too much
- Distinguished between outer grey matter and inner white matter when drawing the cerebrum and cerebellum and illustrated the entire nervous system
Willis extended the view of the nervous system
- Psychic pneuma is generated in the grey matter of the cerebral and cerebellar cortices and circulates through the white matter of the brainstem and spinal cord from the sensory to the motor nerves
- Topographic separation of functionally distinct fiber types within white matter and its continuation in the nerves
- The cerebral grey matter controls voluntary behavior whereas the cerebellar cortex controls involuntary movements
- Certain white matter tracts known from that time interconnect the cerebral and cerebellar cortices
neuron doctrine (Cajal)
nerve cells interact by way of contact rather than continuity (axons and dendrites generally do not anastomose)
functional polarity law (Cajal)
in the context of normal neural circuits, impulses are generally transmitted from dendrites and soma to axon, and then from the axon to its terminals on other neurons or effector cells
four broad eras in the nervous system evolution (Cajal)
- First era - irritability - characterizes certain cells in plant and animals without a nervous system
- Second era - sensory and motor nerve cells derived from the outer covering of the first animals with a nervous system - coelenterates
- Third era - characterized by worms, where neurons between motor and sensory (interneurons) assume equally important role
- Fourth era - characterized by dominant role for second broad class of association neuron - a psychomotor or second order neuron
principles of nervous system evolution (Cajal)
- As evolution proceeds, products of earlier eras are preserved and integrated in more advanced forms
- Hierarchy of conditions required for psychological experiences is linked to the nature of differentiated sensory outputs
- The proliferation of neurons and their process increases the complexity of relationships that can be maintained between various organs and tissues
- Adaptive differentiation of neuronal morphology and fine structure increases their capacity for impulse conduction
- Progressive concentration of neural elements into gray matter masses results in shortening of many processes and consequently an increase in the rate of impulse conduction
- By forcing nervous system differentiation, there is refinement/enhancement of reflex activity which protects life of both individual and species
flatmap
2D schematic drawing to show general spatial relationships within the brain. A good way for showing the general organization, especially for neural circuitry and pathways
connection matrix
connection tables with “from” on one axis and “to” on the other, such as looking at gray matter regions
Swanson’s ideas of an ideal model of the nervous system, including his minimum requirements to move forward
•Ideal model would be systematic, complete, and internally consistent, and needs to have microscopic, macroscopic, mathematical and schematic descriptions
•Seven requirements:
1) hierarchically organized account of all nervous system parts
2) mathematically defined 3D computer graphics models of nervous system need to be developed and made available online
3) computer graphics atlases based on representative series of histological sections
4) nervous system flatmaps
5) schematic diagrams of neural circuitry
6) connection matrices
7) basic plan of nervous system circuitry must be described and analyzed in mathematical terms
optogenetics
- Optogenetics use brief pulses of light that enables the control of electrical potentials of neurons - either activated or silenced
- Takes a light-sensitive protein from algae - this protein is an ion channel that opens in response to blue light. Take the gene for this protein and insert DNA into certain neurons in the brain. Can flash blue light to make neurons fire (firing is an electrical signal created by opening and closing ion channels). With right combo of neurons, you can activate an entire brain circuit or region to control behavior such as movement.
Three classes of opsins used for optogentics
channelrhodopsins, halorhodopsins, and light-driven outward proton pump (eg. archaerhodopsins)
channelrhodopsin
light driven inward cation channels from green algae. They localize to the cell membrane when expressed in neurons, and when illuminated they open up a channel that lets in a positive charge which then depolarizes the cell
halorhodopsin
light-driven inward chlorine pumps. When expressed in neurons and illuminated, they pump chlorine ions into the cells which hyperpolarizes them
light-driven outward proton pump
archaerhodopsins - positively charged protons flow out of the cell, hyperpolarizing them
how are genes typically delivered?
Viral delivery. Once the neurons are infected, the neuron will express the opsin protein. By inserting a promotor (another piece of DNA) in front of the opsin gene, only a specific subset of neurons will have the correct machinery to express the algal protein in the cell membrane.
blindsight
- Cortical regions involved in conscious perception of visual stimuli are damaged but other visual pathways are intact
- Use subconscious vision to see, showing that perceptions don’t need to enter consciousness to affect our behavior
types of cerebral cortex and where they’re typically found
- Isocortex aka neocortex - 6 layers, 90% of cerebral hemisphere (sensory, motor and association areas)
- Mesocortex - 3-6 layers, transition area consisting of paralimbic areas, majority of the limbic lobe
- Allocortex - 3 layers, hippocampal formation (archicortex), primary olfactory areas (paleocortex)
- Corticoid areas - no layers but cortex-like appearance
criteria used to define Brodmann’s areas
Thickness of cortex, number and thickness of cortical layers, arrangement of cells, presence of specific cell types
What is the difference between primary, secondary, and association cortex in terms of the types of information they process?
- Primary cortex - first cortical input of sensory stimuli or last cortical input of movement commands
- Secondary cortex - 2nd cortical input or next-to-last cortical output (more abstract processing)
- Association cortex - processing of more than one sense and/or areas not strictly sensory or motor - multimodal areas, more complex functions
layers of cortex
I - molecular layer, contains very few neurons, and only fibers of cells from other layers rather than cell bodies
II - external granular layer, pyramidal cells, granule/stellate cells
III - external pyramidal layer, pyramidal cells, projection neurons
I-III: supragranular layers, primary origin and termination of the intracortical connections
IV - involved in specific sensations. Internal granular layer, receives thalamocortical connections, stellate or granule cells, interneuons
V - pyramidal cells, internal pyramidal layer, projects to basal ganglia, brain stem and spinal cord, has projection neurons
VI - multiform (fusiform) layer, these cells connect to thalamus, and also receive connections from thalamus, many types of cells
V-VI: infragranular layers, primarily connect cerebral cortex with subcortical regions
gene therapy using adenovirus vector
vector binds to cell membrane, vector is packaged inside the vesicle, vesicle breaks down releasing the vector, vesicle injects new gene into nucleus, cell makes protein using new gene
different portion of layers of cortex
primary motor cortex - majority of layers V and VI, very small IV
association cortex - slightly less V and VI, larger IV
primary sensory cortex - IV is more proportional to combination of V and VI
ways to classify cells in nervous system
- could classify as neurons or glial cells
- Shape, size function, location, number of connections, kinds of synapses, kinds of neurotransmitters
- Structure - multipolar, bipolar, monopolar
- Function - sensory, motor, interneurons
different structures of neuron
multipolar - have many dendrites and one axon, this is the typical neuron
bipolar - have one dendrite and one axon (receiving end of visual, vestibular and auditory systems)
monopolar/pseudo-unipolar have single branch that extends in two directions, often found in dorsal root ganglia
different functions of neuron
- sensory - receive environmental input because their dendrites are “specialized” for detecting physical stimuli. Carry signals from periphery to CNS
- motor - can make muscles contract or gland change, carry signals from CNS to outer parts of body
- interneurons - neurons that lie entirely within the CNS, receive input from and send output to other in brain and spinal cord
glia
surround neurons and hold them in place, control supply of nutrients, insulate neurons from one another
types of glia
1) microglia - respond to injury, act as phagocytes and engulf/breakdown dead and dying neurons, primary immune defense of CNS
2) macroglia
- astrocytes
- oligodendrocytes
- NG2 cells
- Schwann cells
functions of astrocytes
- Provide physical support to neurons
- Clean up debris in the brain
- Help control chemical composition of fluid surrounding neurons
- Involved in providing nourishment to neurons
- Help control extracellular K+ concentration
- Help control BBB along with capillaries
How neurons differ from other cells in body
Have distinctive structural components that serve purpose of:
•Signaling - both with other neurons and with outside world
•Integration of signals from other neurons
Parts of a typical neuron
- Dendrites - receive signal (input)
- Cell body - contains nucleus
- Axon hillock - combines/transforms input
- Axon - conducts signal, carries action potential
- Axon terminals - transmit signal to other cells (output), when AP reaches them they secrete neurotransmitter, form synapses with other neurons
interneuron
- Receive input from and send output to other neurons
- Enable communication between sensory or motor neurons and the CNS
- Local interneurons form circuits with nearby neurons and analyze small pieces of info
- Relay interneurons connect circuits of local interneurons in one region of the brain with those in other regions
Division of Nervous System
•Central NS - brain, spinal cord
•Peripheral NS - consists of nerves and most of sensory organs
-Somatic NS: taking in sensory info, interact with environment
-Autonomic NS: normal, underlying functions, regulation of internal environment of body, carries signals between CNS and sensory organs
>Sympathetic Nervous System
>Parasympathetic Nervous System
>Enteric Nervous System
Autonomic Nervous System
- Sympathetic NS: prepares body for fight or flight, functions to coordinate expenditure of energy especially in response to stressors
- Parasympathetic NS: increases metabolic and other resources during rest and digest, increases supply of stored energy and returns body to resting state
- Enteric NS: control function of gastrointestinal tract, pancreas and gallbladder
types of info carried by cranial nerves
- 12 nerves that serve sensory and motor functions in the head, neck, and thoracic and abdominal cavities
- Smell, vision, eye movement, touch, pain, chewing, facial expression, hearing, functions of viscera (digestion, heart rate, glands)
dorsal versus ventral root
- Small bundles of fibers emerge from each side of the spinal cord in two straight lines along its dorsolateral and ventrolateral surfaces. Groups of these fibers fuse together and become thirty-one paired sets of dorsal and ventral roots
- Dorsal root is sensory, ventral root is motor
information carried through sensory from dorsal and ventral horns
- Motor neurons in ventral horn project their axons into periphery to innervate skeletal and smooth muscles that mediate voluntary and involuntary movements
- Dorsal horns deal with sensory perception and receive info from the periphery into the dorsal root
patch-clamp experiment in whole-cell mode
- Allows measurement of ion flow through ion channels (current) or changes in membrane potential (voltage) in a patch of membrane
- A glass pipette uses a small amount of suction to make tight contact with a patch of neuronal membrane. In whole-cell mode, the membrane patch is disrupted and interior of pipette becomes continuous with the cytoplasm which allows for measurements of electrical potentials and currents from entire cell using an ultrasensitve electronic amplifier connected to the pipette
- Record of the current reveals whether channel is open or closed
capacitance
- storing charges by separating them, membrane is holding positive and negative charges in place
- If you open pore in membrane, all negative charge won’t leave at once because the membrane has capacitance so it’s being held in place. The voltage across the membrane is resisting change so it’s taking more time to discharge the membrane and for negative charges to essentially leave the cell.
what happens when increase or decrease capacitance
Myelin on the axon would decrease ability to store charges across the membrane because increasing space between opposite charges. This lowers capacitance charges can essentially ignore pull of charges across the membrane. Myelination can cause faster spread of passive currents
voltage
separation of unlike charge (+ vs. -) in space, the difference in electrical “potential” between 2 points
current
flow of electrical charges (I)
resistance
opposition to flow of electrical charges, difficult with which current flows in a circuit
Ohm’s Law
I=V/R
Current is directly proportional to voltage, and inversely proportional to resistance
equilibrium potential
voltage reached by making the membrane permeable to a single ion
ways ion channel can be gated
•Non-gated “leak” channels : always open, many are K+ channels
•Gated channels open in response to a particular event
- Voltage-gated: open in response to change in membrane voltage
- Ligand-gated: open in response to binding of a chemical messenger like a neurotransmitter from another neuron
equilibrium potentials for potassium, chloride, sodium
Potassium: around -85mV
Sodium: around +55mV
Chloride: around -66mV
Nernst Equation
E= RT/zF…
taking into account concentration of ion both inside and outside cell
ion concentrations
- potassium and charged proteins more concentrated on inside of plasma membrane
- sodium, chloride, calcium more concentrated on outside
Goldman equation
- looking at whole cell and considering all species of ions
- Vm= [(RT)/F]ln(permeability)
TTX and TEA and their effects on action potentials
- TTX - voltage gated sodium channel blocker, blocks action potentials from occurring because an action potential in an axon can’t be initiated without voltage-dependent Na+ channels
- TEA - voltage gated potassium channel blocker, action potential would be longer and wouldn’t have an overshoot because blocking ability to restore membrane to resting potential
action potential
brief electrical impulse that provides basis for conduction of information along the axon
refractory period and different types
- Refractory period - period of time when channels become blocked and another action potential cannot be generated
- prevent AP from turning around and limit how often patch of membrane can generate AP
* Absolute refractory period - voltage-gated Na+ channels are inactive immediately after closing
* Relative refractory period - patch of membrane still fairly unresponsive because it needs to because it tends to become slightly hyperpolarized briefly after AP
gates of voltage-gated Na+ channels
- activation gates open rapidly
* inactivation gates close slowly
role of sodium potassium pump
- continuously pushing Na+ out of cell
- driven by energy provided by molecules of ATP produced by mitochondria
- push three sodium ions out for every two potassium ions they push in
single-unit recording versus field potential recording
- single-unit recording: recording of action potentials of one or more units (neurons) near the electrode tip
- field potential recording: recording summed electrical current flowing from nearby neurons
how does fMRI measure brain activity?
- Measures brain activity indirectly by measuring changes in blood oxygenation levels to sensory stimuli or during motor responses
- Provides excellent spatial resolution of regional activity in the brain
- Increased activity of a brain region stimulates blood flow to that region which increase the local blood oxygen level
anterograde and retrograde labeling
- Anterograde labeling methods employ chemicals that are taken up by dendrites or cell bodies and are transported through the axons toward terminal methods and traces the pathways of the efferent axons
- Retrograde labeling methods used chemicals which are taken up by terminal buttons and transferred back up through axon to cell body
- Retrograde and anterograde help discover circuits of interconnected neurons
MRI
creates image of tissue based on temporary disruption of a spatially varying magnetic field. Hits protons with radio frequency energy and protons absorb energy and will flip orientation and eventually emit some radio frequency back
DTI
images of white matter tracts based on diffusion of water molecules. Measures movement of particles that generate signal and location of fiber bundles to determine which brain structures are connected to each other and how strong their connection is
nissl stains
stains the cell body, in particular the endoplasmic reticulum and highlights important structural features of neurons
golgi stains
stains nerve tissue using silver staining technique
EEG
- EEG measures net voltage in a region of cortex and field potentials
- Signal generated by summation of synchronous activity of thousand of neurons
- Typically described in terms of frequency of rhythmic activity
states of EEG and rhythms
Delta - 1-4 Hz, infants and stages 3-4 of sleep
Theta - 4-8 Hz, regular children up to 13, and in sleep
Alpha - 8-13 Hz, major rhythm in normal relaxed adults with eyes closed
Beta - 13-30 Hz, occur when alert or attentive or in REM sleep
Gamma - 30-100 Hz, cognitive functions?
In what general ways do techniques for discerning structure-function relationships in the brain differ
Differ by their temporal resolution (fractions of a ms to a year), spatial resolution (from synapse to brain) and their relative non-invasiveness
In order for someone to claim they’re consciously aware of a stimulus, a stimulus must:
register in the brain’s language centers
Which describes permeability of a neuronal membrane at rest?
The membrane is more permeable to K+ than Na+
At resting membrane potential of -70mV, what ion is being driven into the cell by both electrochemical force and force of diffusion?
Sodium (Na+) and Calcium (Ca2+)
Which equation describes the voltage at which a given ion ceases to flow across a porous membrane?
Nernst equation
Which equation takes permeability of multiple ions into account to compute the voltage across membrane?
Goldman equation
What determines whether a given segment of a neuronal membrane is able to conduct an action potential?
The density of voltage-gates SODIUM channels
increases of intracellular concentrations are necessary and sufficient for neurotransmitter release from the axon terminal?
Calcium (Ca2+)
In order for postsynaptic neurons to respond to a neurotransmitter, that neurotransmitter much bind to ion channels
False - there are metabotropic receptors too
A synapse closer to axon hillock…
True
Which of following regions of cortex contains less than 6 layers but more than 3?
Cingulate Gyrus
What are 2 most common neurotransmitters in the CNS?
GABA and Glutamate
GABA typically inhibitory, glutamate excitatory
Acetylcholine broken down in synaptic space
True
What are criteria for labeling chemical as neurotransmitter?
1) synthesized in presynaptic neuron
2) stored in presynaptic terminal
3) released from presynaptic terminal in sufficient amounts to produce postsynaptic effect
4) receptors on the postsynaptic terminal
5) removal from the synaptic cleft terminates action
How is action of acetylcholine terminated?
enzymatic degradation and diffusion
What is myasthenia gravis? How is it treated?
individuals develop antibodies against cholinergic receptors on muscle which leads to severe weakness and fatigue.
•Can be treated by neostigmine and pyridostigmine
ionotropic receptor
ion channel opens when a molecule of neurotransmitter attaches to the binding site
direct method of how neuroT open ion channel
these receptors are sensitive to acetylcholine
metabotropic receptors
ligand binding to these receptors start chain of chemical events
when neuroT binds, receptor activates G protein and simulates second messenger
