4. Nervous System Flashcards
Know structure of neuron
Dendrites (receive incoming signals from cells), soma (contains nucleus, ER and ribosomes), axon hillock (integrates incoming signals), axon, axon terminal, myelin sheath (help inc speed of conduction), nodes of Ranvier (critical for rapid conduction), synapse, neurotransmitters, target cell
What do myelin sheaths do? What produces them?
Insulate axon to maintain and speed up signal travel, prevent dissipation of signal, they contribute to saltatory conduction; oligodendrocytes in CNS and Schwann cells in PNS
What are glial cells/neuroglia? Examples? What type of tissue are they made of?
Structural support for neurons. astrocytes vs ependymal cells vs microglia vs oligodendrocytes and Schwann cells. Unmyelinated neural tissue
Examples of afferent and efferent neurons? What are interneurons?
Sensory neurons (bring info to dorsal side of spinal cord => dorsal root ganglia); motor neurons (bring info to ventral side of spinal cord) Most numerous, found between other neurons, reflexive behavior, kinda like a brain substitute
Nerves vs tracts
Group of neurons carrying sensory, motor, and/or mixed info; together they make up ganglia in PNS vs group of axons carrying only 1 kind of info; together they make up nuclei in CNS
Explain the types of glial cells: astrocytes vs ependymal cells vs microglia vs oligodendrocytes and Schwann cells
nourish neurons and form blood-brain barrier to allow small nonpolar hydrophobic molec into into nervous tissue from bloodstream vs produce CSF as brain’s shock absorber vs phagocytes in CNS vs producers of myelin sheaths in CNS and PNS respectively
Depolarization vs hyperpolarization
Raising membrane potential (less difference in charge) –> closer to action potential; caused by excitatory signals vs lowering membrane potential (more difference in charge) –> farther away from action potential; caused by inhibitory signals
Temporal summation vs spatial summation
Multiple signals integrated in short period of time vs additive effects based on number and location of signals
Why doesn’t membrane potential keep increasing when sodium channels open? Why does it decay?
It doesn’t always increase b/c when neurotransmitter leaves sodium channel receptor, the channel closes. It decays b/c sodium ions will diffuse along conc gradient
What are the most common excitatory signals and most common inhibitory signals?
Incoming Na and Ca via electrostatic forces –> depolarization; incoming Cl and outgoing K via diffusion –> hyperpolarization
What’s the threshold value for action potential? What’s the resting membrane potential value?
-50 mV; -70 mV
What is saltatory conduction?
When action potential hops from node to node of Ranvier (myelin = good insulator –> prevent dissipation of electrical signals)
Are leaked channels gated? Are receptors of dendrites gated?
No, leaked channels are open all the time. Dendrites have ligand gated ion channels
What type of gated channel is along axon?
Voltage gated ion channels
What is the refractory period? What are the two types of refractory period?
The slow return to resting potential. Absolute - when no amount of excitatory input can trigger another action potential; relative - when greater than nml amount of excitatory input can trigger another action potential
Presynaptic neuron vs postsynaptic neuron vs effector
neuron before synaptic cleft vs neuron after synaptic cleft vs cell, gland or muscle after synaptic cleft
What are neurotransmitters? Where are they stored? From where are they transmitted?
Molecules that carry info from neuron to neuron. Stored in synaptic vesicles. Neurotransmitters like serotonin and dopamine = transmitted from axons to synaptic cleft; NO and cannabinoid neurotransmitters = transmitted from dendrites to synaptic cleft => retrograde neutrotransmission
What are 3 types of neurotransmitters?
Amino acids, peptides, monoamines
Examples of amino acid neurotransmitters? Which are excitatory and inhibitory?
glutamate (excit), GABA more in brain and glycine more in spinal cord (inhib). Glycine inc Cl influx into neuron
Examples of peptide neurotransmitters? How are they produced?
Endorphin, opioids. Their precursors & enzymes = axonally transported in vesicles
Examples of monoamine neurotransmitters?
Serotonin and histamine; dopamine and nor/epinephrine (catecholamines)
Explain how neurotransmitters are released
Action potential reaches axon terminal —> voltage gated Ca channels allow stored Ca to flow from axon terminal into presynaptic membrane —> proteins fuse vesicles into presynaptic membrane –> neurotransmitters diffuse from vesicles into respective neurotransmitter receptors of postsynaptic membrane
What are the 3 ways neurotransmitters are removed?
Diffusion away from synaptic cleft like NO; enzymes break em down like AchE; re-uptake carriers like dopamine, norepinephrine, and astrocyte endfeet
White matter vs grey matter. Is the brain made out of these?
Portion made of myelinated axons vs unmyelinated somas AND DENDRITES. Brain = made up of both white and grey matter
All or none property
Doesn’t matter how far you’re above a threshold; if you’re above it, it’ll activate an action potential. So theoretically, there is no “maximum action potential”
Do action potentials decay over long distance?
Nope. Even if the axon is a meter long
Equil potential of potassium
Lots of K inside cell —> K wants to move outside of cell. Leaked K channels slowly allow K to leave cell until some K wants to move back into cell cuz cell becomes more neg when K leaves in the first place. Eventually, amount of K in and out of cell stays at equil —> -90 mV (it’s neg bc K was leaving cell)
Equil potential of sodium
Lots of Na outside cell —> Na wants to move inside of cell. Leaked Na channels slowly allow Na to move into cell due to electrochemical gradient until it reaches equil —> 35 mV (it’s pos bc Na was moving into cell)
Impulse propagation. Know how distance and cross sectional area of axon affects speed of action potential
When action potential travels along the axon. like fluid dynamics!: longer axon –> more resistance –> slower conduction, bigger cross sectional area –> less resistance –> faster conduction
Na/K pump
When Na/K ATPase uses ATP to restore resting potential by kicking out 3 Na out of cell and putting 2 K into cell
Vertebral column and 4 regions of spinal cord
Protects spinal cord, transmits nerves at space between adjacent vertebrae; cervical, thoracic, lumbar and sacral
Preganglionic neuron and postganglionic neuron
2 neurons working in series transmitting messages from spinal cord in autonomic nervous system
Monosynaptic vs polysynaptic reflex arc
Single synapse b/w sensory neuron and motor neuron like knee jerk reflex vs at least one interneuron b/w sensory neuron and motor neuron like stepping on a nail and maintaining balance
Acetylcholine
A neurotransmitter active in both sympathetic and parasympathetic nervous system. Preganglionic neuron releases Ach in both systems; postganglionic neuron releases norepinephrine in sympathetic and more Ach in parasympathetic. Generally considered as excitatory signal since it’s linked to attn and arousal in CNS. Produced by choline acetyltransferase
Know divisions of CNS and PNS
CNS: brain and spinal cord
PNS: somatic and autonomic nervous system, auto breaks into para/sympathetic systems and enteric, soma and auto contain sensory and motor neurons; soma motor neurons for skeletal, auto motor neurons for smooth muscle and gland secretion; soma sensory neurons for somatosensation and reflexive arcs, auto sensory neurons for receiving info from viscera and sending it to CNS
Vagus nerve is impt for which nervous system? Relaxing bronchi occurs in what nervous system?
Parasympathetic nervous system; it slows down HR
Relaxed bronchi in sympathetic nervous system
Chemical synapses vs electrical synapses
Unidirectional vs bidirectional, less regulated —> faster and more uniform signal transmission
