Final neurobiology Flashcards
lays down myelin around some axons
oligodendrocytes
Specialized macrocyte cells in the brain that remove myelin and cellular debris
microglial cells
maintain an appropriate chemical environment
astrocytes
nerve cell bodies that reside in the PNS
ganglia
bundles of peripheral axons
nerves
local accumulations of neurons that have roughly similar connections and functions
nuclei
sheet like arrays of nerve cells
cortex
gathering of CNS axons
tracts
tracts that cross the midline of the brain
commissures
what his the resting (membrane) potential and what is the ionic basis underlying it
The resting membrane potential is largely determined by the K+ selective permeability and K+ concentration gradient
Below is the Nernst equation for the electrochemical equilibrium of a permeant ion. Eion is the equilibrium potential (measured in units of mV) generated by the permeant ion across the membrane at electrochemical equilibrium; [ion]out and [ion ]in are permeant ion’s concentration outside and inside the cell. z is the electrical charge of the permeant ion (2 for Ca2+). Log10 = 1, Log100 = 2, Log1000 = 3, Log1/10 = -1, Log1/100 = -2, and Log1/1000 = -3. If a neuron has 10 mM Ca2+ inside the cell and 10000 mM Ca2+ outside the cell, the equilibrium potential of Ca2+ for this neuron would be? Eion = 58/Z log ion out/ion in
+87 mV
A neuron’s resting potential is -65 mV and the threshold potential is -40 mV. The equilibrium potential for Na+ (ENa) of this neuron is +70 mV. You use a voltage clamp method to inject positive currents into a neuron at the resting potential to depolarize the membrane potential by 40 mV. The membrane potential for the neuron is now clamped at?
specific value -65 mV + 40 mV = -25 mV.
- A transient increase in Na+ conductance causes Na+ to enter the neuron and quickly depolarizes the membrane potential (PNa+↑).
- Depolarization slowly activates the voltage‐dependent K+ conductance, causing K+ to leave the cell and repolarizing the membrane potential (PNa+↓ & PK+↑↑).
- Undershoot: the K+ conductance becomes temporarily higher than it is resting, (hyperpolarization, PK+↑↑). Hyperpolarization causes the voltage‐dependent K+ conductance to turn off, and the membrane potential returns to the resting potential (PK+↑).
- Refractory period: following an action potential, the axon becomes refractory to further excitation for a brief period.
reconstruction of action potential
Which protein molecule generates sodium and potassium ion concentration gradients across neuronal membranes?
Sodium-Potassium ATPase Pump
- An action potential depolarizes the presynaptic axonal terminal.
- Depolarization leads to the opening of voltage‐gated calcium channels.
- The influx of Ca2+ allows synaptic vesicles to fuse with the presynaptic membrane.
- Neurotransmitter is released into the synaptic cleft via exocytosis.
- The neurotransmitters bind to receptors in the postsynaptic membrane, causing channels to open or close.
- Neurotransmitter‐induced postsynaptic current increases or decreases the probability that the postsynaptic cells will fire an action potential (the excitability).
sequence of events involved in chemical synaptic transmission
If the reversal potential is more ______ than the threshold potential then it is excitation
positive
if reversal is more negative than threshold potential then it is _____
inhibitory
-45 mV – (-65 mV) = 20 mV
EPSPs + IPSPs need to be greater or equal to 20 mV. 10mV – 4mV – 3mV + 15 mV = 18 mV
18 mV < 20 mV, so the neuron would not fire an action potential
Enzymatic degradation (3)
Acetylcholine, Substance P, and Opioid Peptides
Uptake through transporters (4)
Glutamate, GABA, Dopamine, and Serotonin
ionotropic NT
Nicotinic acetylcholine receptor
AMPA
NMDA
P2X receptors
Metabotropic NT
-Muscarinic acetylcholine receptor
-dopamine receptor
-α-adrenergic receptors
-β-adrenergic receptors
ii. Peptide transmitters are made as propeptide precursors and packed in large dense-core vesicles
iii. Propeptides can give rise to more than one species of active neuropeptides.
iv. Peptide transmitters typically elicit complex postsynaptic responses
Understand synthesis and processing of peptide transmitters and they are packed in which types of vesicles?
The mechanism for short-term synaptic depression
Depletion of the presynaptic vesicle
what is the common btw LTP and LTP
both remove or internalize AMPARs from the surface
Differences between LTD:
Cerebellar:
1. uses kinases
2. coincidence detector: activation of mGluR + VCa2+ synapses
Hippocampal:
1. uses phosphates
2. coincidence detector: NMDAR
How do receptor potentials encode the intensity of stimuli?
Receptor potential is grade so their amplitude will be correlated with their intensity (increase in amplitude with increasing intensity of the stimulus)
Senses mediated by dorsal root ganglion neurons
Touch, proprioception, nociception, and thermoception (heat or cold)
sense points
Merkel cells
sense skin motion
messiner corpuscles
sense vibration
pacinian corpuscles
cutaneous stretching
Ruffini corpuscles
the primary somatosensory cortex has _____ _____ that does not reflect
disproportional somatotopy
The neurons in the Primary SSC will cluster together to form _____ _____ _____
functional distinct columns
lesions to which area will cause the most severe deficit in primary somatic sensory cortex
3B
C fibers convey what type of pain, 1st or second
second
injury to one side then the patient will lose tactile sensation and proprioception on that same side but will lose nociception on the opposite side of the injury.
Dissociated Sensory loss
convey a sharp pain first
A epsilon
-mediates tactile sensation and proprioception
-is the axon bundle of the dorsal root ganglia neuron running in the spinal cord
dorsal column
-mediates nociception - pain
-axon bundle of dorsal horn neurons in the spinal cord
anterolateral column
1) Photoreceptors absorb a photon of light and change 11-cis retinal to all-trans isomer.
2) Conformational change of rhodopsin leads to activation of transducin (Gt)
3) Transducin activates a phosphodiesterase that hydrolyzes cGMP
4) Lowering of cGMP concentration in the outer segment
5) cGMP-gated channel closure and hyperpolarization of the cell
The sequence of events of phototransduction
low acuity + scoptic vision
rod
-specialized for acuity
-phototopic vision
cone
The spatial arrangement of different sounds and different frequencies are processed in different regions of the auditory system
tonotopy
what is the mechanoelectrical transduction: the process by which hair cells convert mechanical energy from sound waves to electrical signals
what its the sequence for mechanical transduction
- displace of the hair
- opening (MET) channel
- K+ influx generates a graded receptor potentiation to depolarize the hair cell (HAIR CELLS DO NOT FIRE ACTION POTENTIALS)
- depolarizing + opening of VGIC Ca2+ and transmitters release
liner acceleration
otolith
rotational acceleration
semicircular canal
The olfactory system does require a thalamic relay from the receptor neurons to the pyriform cortex True or false
False it does NOT require thalamic relay
i. Odorant receptor proteins are encoded by the odorant receptor gene family
ii. Each of the olfactory receptor neurons expresses only one of the two copies of the odorant receptor genes
iii. Most mammalian olfactory receptor neurons express only one odorant receptor gene) **
iv. Odorant receptor proteins are G‐protein‐coupled receptors
v. Odorant receptor proteins are found at the highest concentration in the olfactory cilia of the olfactory receptor neurons
odorant receptor proteins
1) Alpha subunit of Golf dissociates upon odorant binding to receptors
2) Activation of adenyl cyclase III (ACIII)
3) An increase in cAMP opens cAMP‐gated channels that permit entry of Na+ and Ca2+
4) Depolarization is further amplified by Calcium‐activated Cl‐ channels
5) Action potential are generated via voltage‐gated sodium channels
The Sequence of events of odor transduction
TRPM5 channel is involved in sensory transductions for
sweet, bitter, and umami tastes
Sensory Epithelia for Visual
retina
Sensory Epithelia for Auditory
Organ of Corti
Sensory Epithelia for Otolith organs (Utricle and Saccule)
Macula
Sensory Epithelia for semicircular canals
crista
Reflex movement is the movement that does or doesn’t involve Cortical upper motor neurons.
DOESNT
Cell types involved in reflex movements
Cells involved in reflex movements are sensory neurons, lower motor neurons, interneurons, brainstem upper motor neurons
-gradual increases in muscle tension (or force) results from the progressive recruitment of motor units in a fixed order (S → FR → FF), according to their size.
–Low threshold S motor units are recruited first, then FR motor units, and finally, at the highest levels of activity, the FF motor units
Size principle
maintain muscle length at a desired level
muscle stretch reflex
maintain muscle tension (force) at a desired level
Autogenic Inhibition Reflex
without sensory feedback or descending UMN inputs
Central Pattern Generator
generates a feedback response to stabilize posture after existing unanticipated postural instability
Vestibulo-Spinal Reflex
generates a feedforward response to stabilize posture to anticipated postural instability.
Reticular Formation
control the orientating head and eye movement
Superior Colliculus
encode intentions for movements in central personal space
UMNs Primary Motor Cortex
encode intentions for movements that are oriented toward extra personal space (beyond arm’s length)
UMNs Premotor Cortex
initiate feedforward voluntary adjustments that stabilize posture to anticipated postural instability
UMNs Reticular Formation
The corticospinal tract is the axons of the UMNs in the motor cortex, which descend through the ____ white matter and terminate in _______ spinal cord
lateral; contralateral
A subset of UMNs in the premotor cortex fire when an animal observes and performs a particular movement
What are mirror motor neurons
What are the four major parts of the basal ganglia
i. The corpus striatum
ii. The globus pallidus
iii. The substantia nigra
iv. The subthalamic nucleus
HYPOKINETIC (difficulty in expression of movement) movement disorder CAUSED by the loss of the dopaminergic neurons in substantia nigra pars compacta
parkinson’s disease
Loss of _____ input → increased indirect pathway and diminished direct pathway → more tonic inhibition of thalamus → decreased excitation of motor cortex UMNs → reduced voluntary movement.
dopaminergic
Medium spiny neurons that project to the external globus pallidus degenerate
Huntington’s disease
Cortical inhibitory loop is formed by _____ _____ cells that provide the only output from the cerebellar cortex
GABAergic Purkinje
formed by deep cerebellar nuclei neurons
Deep excitatory loop
Parallel fiber pathway conveys the main inputs and functions to _____ ____
correct motor errors for ongoing movements
Climbing fiber pathway convey the modulatory input and functions to encode
motor learning and memory
the folding process of ectoderm to develop the neural tube
Neurulation
the single‐layered blastula is reorganized into a multilayered structure known as the gastrula
Gastrulation
Prosencephalon
cerebral cortex, hippocampus, basal ganglia, thalamus and hypothalamus
midbrain tegmentum, superior colliculi
Mesencephalon
cerebellum, pons, and medulla
Rhombencephalon
dorsalizing signals to regulate specification of the neural tube and differentiation of dorsal part
BMP
secreted from notochord to block BMP signaling for neural induction
Noggin and Chordin
ventralizing
Sonic Hedgehog
neuronal differentiation during neurogenesis by regulating neural stem cell decisions to generate either additional stem cells or postmitotic neurons
Delta/Notch
What are the two major functions of radial glial cells in the developing CNS?
- Acting as migratory guides
- They are neuronal progenitor (stem) cells in the developing cortex
regulate neuronal polarization
Par
axon guidance chemoattractant
Netrin
non-diffusible axon guidance molecules and constitutes cell-cell recognition codes
Eph/ephrin
- Neurite outgrowth or retraction
- Synapse stabilization or elimination for activity‐dependent plasticity
- Cell survival or death
Neurotrophins
Neurotrophins receptors
- Tyrosine kinase (Trk) receptors
- P75 receptor
- Explain the cellular basis of the experience-dependent modification of neural circuits
- Suggests that synaptic contacts between co-activated pre- and postsynaptic neurons will be strengthened and strengthening of synaptic connections
- Strengthening of synaptic connections can be reflected in sprouting of new branches
- Uncorrelated activities between pre- and postsynaptic neurons result in loss of synaptic connections
Hebb’s postulate
The temporal window when experience and the resulting neural activity have a maximal effect on the circuit connectivity and the acquisition or skilled execution of a particular behavior
critical period
key players of activity-dependent plasticity during the critical period?
Neurotransmitter receptor (NMDA receptor), CREB transcription factor, kinase, intracellular Ca2+, and neurotrophins
distinct anatomical and functional arrangement of neurons within the primary visual cortex of the brain.
Ocular dominance column
the column for the deprived eye becomes narrower, while the column for the intact eye becomes wider
monocular deprivation
early deficiencies of sensory experience (4)
ADHD, Autism, Amblyopia, and Schizophrenia
What is the underlying reason for improved functional recovery after mammalian CNS damage
Reorganization of intact undamaged circuits rather than the regrowth or replacement of damaged neurons
Describe the sequence of events during peripheral nerve regeneration
- The distal portion of the injured axon degenerates.
- Macrophage phagocytoses myelin and axonal debris.
- Schwann cells proliferate and secrete molecules to guide and stimulate regeneration.
- Injured neurons transform the proximal segment of the injured axon into a growth cone, express growth-related genes, and increase protein trafficking.
- Axon regrows to the target.
the process that all three types of glial cells (astrocytes, oligodendroglia, and microglia) are activated by proliferation and hypertrophy in response to the CNS injury
Reactive Gliosis
formed by astrocytes prevents axon growth + physical barrier that inhibits axon growth
glial scar
What are the factors that inhibit the regrowth of CNS axons after injury
a) glial scar
b) Chemorepellents
c) Extracellular matrix components
d) Myelin‐associated inhibitors
What are the two neurogenic areas in the adult mammalian brain?
Subventricular Zone (SVZ) and Subgranular Zone (SGZ)
