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34 Cards in this Set
- Front
- Back
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What is a resting membrane potential?
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Voltage that exists across the plasma membrane during the resting or polarized state of an excitable cell
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What is the voltage number and atomic substances involved in the plasma membrane of the nerve cell
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On the outside is where Na+ is balanced with Chloride; the negative charge inside of -70mV. Positively charged potassium is attracted to the negatively charged proteins.
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What is a voltmeter?
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measures the resting membrane potential @-70mV. The electrode measures inside cell, and another measures outside the cell.
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How is the membrane potential maintained?
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Indirectly by the sodium potassium pump, which transports 3 Na+ out of the cell for every 2 K+ transported back into the cell. This helps the gradient persist in spite of constant potassium passive leakage.
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What are the 2 signals used to produce a change in a resting membrane potential and what 2 terms are normally involved with these signals?
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The 2 signals are: graded potentials and action potentials. The 2 terms associated with them are depolarization and hyperpolarization.
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T/F Restimulation during a refractory period cannot happen if the membrane is in a hyperpolarization state.
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False. it can be restimulated, but only with substantially more frequency of firing impulses to cause a substantial influx of sodium in through the membrane.
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What is conduction velocity?
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How fast the impulse is moving down the axon. Has everything to do with degree of mylenation. Fast conduction happen in fatter type A fibers involving skeletal muscles; Slower conduction happens in internal organs or in unmylenated areas with close proximity-brain.
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How are the 3 types of nerve fibers distinguished or classified in general.
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Degree of mylenation and diameter of axon= speed of conduction
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What is a synapse?
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A functional junction where an action potential is transferred from one neuron (presynaptic) to the next (postsnaptic) or to a muscle by a neurotransmitter.
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What are the names of the 3 types of synapses?
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Axodendritic, Axosomatic, Axoaxonic
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Describe the axodendritic synapse
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Between the axon endings of one neuron and the dendrites of other neurons, primary type, would set off a graded potential.
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Describe the axosomatic synapse
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A synapse between the axon endings and cell bodies of other neurons involving graded potential.
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Describe the axoaxonic synapse
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The axoaxonic synapse happens between axons and is less common. An action potential is involved.
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What are electrical synapses?
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The least common of the two types. Involve gap junctions where ions flow back & forth between cells through the intercellular space. Cells work as one big cell, cells are electrically coupled causing synchronization, found in unmylenated gray matter of the CNS, closely packed nuclei function as unit.
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What are chemical synapses?
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Neurotransmitters convert an electrical impulse coming from a presynaptic neuron into a chemical impulse across a synaptic cleft and then back into an electric impulse in the postsynaptic neuron. Neurotransmitter receptor region is on membrane of dendrites or cell bodies. Synaptic vesicles filled with various molecules are released from and bind with receptor sites on the postsynaptic neuron.
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Describe the process of information transfer across chemical synapses
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1) Ca+ channels open in response to depolarization or AP at the axon terminal. 2) Ca+ release induces synaptic vesicles w/in the terminal boutton to fuse w/ terminal axon membrane releasing neurotrans. molecules (exocytosis) into synaptic cleft. 3) Molecules like (ACh) diffuse across synaptic cleft & bind w/ receptors on the postsynaptic membrane. 4) Receptor undergoes conform. change when neurotrans-mitter binds to it, causes chem-gated channels to open causing Na+ to flood in, starts graded potential. ( *This is when receptors may be inhibited or excited.) 5) Cholinesterase or some enzyme will degrade the neurotrans. inducing membrane to return to original state.
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What is the synaptic cleft?
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The space separating the pre-synaptic neuron and postsynaptic neuron where released chemicals from neurons diffuse and bind with corresponding neurons resulting in neuron communication.
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What is an excitatory synapse or EPSP?
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When neurotransmitter binds and causes depolarization or influx of sodium causing a graded potential proceeding to the axon hillock. These potentials decrease rather quickly, but are usually enough to get an action potential propagated at the axon hillock.
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What is an IPSP or Inhibitory synapse?
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This potential is caused by inhibitory neurotranmitters that cause hyperpolarization (no Na+coming in, but lots K+ going out) which inhibits the postsynaptic neuron from firing, inhibiting an action potential. This is how we anesthetize people, or it can be a protective response with the release of inhibitory neurotransmitters like endorphins.
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What is summation in the postsynaptic neuron and why is it necessary?
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A single EPSP cannot induce an action potential in postSN. but if combined w/many excitatory axon terminals firing the same membrane or if impulses are more rapid on fewer terminals, then reaching threshold depolarization is likely. Nerve impulses won't happen without this summation.
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What is subthreshold?
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No summation because EPSPs don't overlap at the synapse and threshold is not reached-necessary to propagate AP.
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What is Temporal summation?
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Occurs over time (temporal means time) by hitting more than one impulse sequentially in rapid succession=-55 threshold; as each next impulse is added to the residual, initial EPSP and its this summation over time that helps propagate a potential.
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What is spatial (means more than one) summation?
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Occurs when the postsynaptic neuron is stimulated @ the same time by more than one presynaptic neuron. Depending on if it's more than one excitatory which would dramatically enhance postsynaptic depolarization or if by 2 IPSP would dramatically increase hyperpolarization or one of each would cancel each other out.
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What are neurotransmitters and how are they classified?
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The chemical language of the nervous system. Molecules released from axonal terminal bouttons that propagate a nerve impulse to the postsynaptic neuron. More than 50 identified. Some neurons only release 1 neurotransmitter, some release 2+. Classified according to chemical makeup and function. Released at different stimulation frequencies. A neuron that releases more than 1 type of n.t. is diverse, causes epsp or ipsp, and postsynaptic neurons have various receptor sites for different types of neurotransmitters. Complexity of neurons is related to: neurotransmitters-ipsp-epsp-& receptor sites.
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What happens with nicotinic ACh receptors?
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If the chemical nicotinic Ach is released and there is a nicotinic receptor, then the response will be an Epsp, the binding of the nicotine gives a boost like in people who smoke.
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What is a muscarinic Ach receptor?
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One that binds with muscarinic ACh. Can be inhibitory or excitatory in the PNA
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What are the following molecules found in CNS: Acetylcholine, Norepinephrine, Dopamine, and Seratonin known for as far as inhibition or excitement?
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Ach is excitatory, Norepinephrine (amphetimines) is excitatory or inhibitory-feeling good, Dopamine-deficient in parkinsons, blocked by cocaine, excitatory or inhibitory-feeling good, Seratonin allows us to sleep, mainly inhibitory.
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What are the main regions of the brain?
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Cerebral hemispheres-higher level thought, Diencephalon-center & most primitive part, Brain stem:midbrain, pons, medulla oblongata, Cerebellum-posterior region with arbor vitae (cauliflower)
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What is meant by "ontogeny recapitulates phylogeny"?
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As we grow we develop through evolutionary stages that are representative of what our ancestors looked like, (tails, webbed feet/fingers,...)
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What is the general organization of the brain?
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Most inner: central cavity housing spinal fluid, Next layer out: gray unmyelinated matter core; Next layer out: white matter-myelinated fiber tracts; Final layer: (this final layer not found in spinal cord) more gray matter "bark" called the cortex.
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Name the ventricles and their locations in the brain.
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There are 4 ventricles lined with ependymal neuralgia ciliated cells for SF: 2 lateral ventricles:c-shaped horns that are separated by septum pellucidum; 3rd ventricle that is between & below the lateral ventricles located in diencephalon; 4th ventricle is continuous with central canal of spinal cord that is inferior. Note: also interventricular foramen (foramen of monro) a channel allows lateral & third ventricles to communicate. And 3rd ventricle is continuous w/4th ventricle via the cerebral aquaduct that runs through the midbrain. Realize that fluid can exit 4th ventricle by lateral or median apertures and down central canal, basically brain is floating!
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Describe the Cerebral Hemispheres
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Forms superior part of brain; covers the diencephalon & top of brain stem. Entire surface has ridges of elevated tissue called gyri., Sulci-grooves or valleys that separate the gyri, Fissures-deeper grooves separating large regions of the brain; longitudinal (sep. cerebral hemispheres), transverse cerebral (sep. cerebral hem. from cerebrellum); Several sulci: central sulcus (divides frontal & parietal lobe), precentral sulcus (frontal lobe), postcentral sulcus (parietal lobe), lateral sulcus (sep. termporal lobe from frontal & parietal
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What is the cerebral cortex?
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Our conscious mind, enables us to be aware of ourselves, & sensations, communicate, remember, understand, initiate voluntary movements. Is the outermost layer composed of gray matter: neuron cell bodies, denrites, associated with glial cells & blood vessels, but no fiber tracts. Cortex has some unmyelinated axons allowing for continuous conduction, glial cells make up 50% of brain. White matter deep to cortex also houses more gray matter called Basal nuclei.
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Who is Brodman and what is he known for?
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1906 Brodman identified areas of the cortex that corresponded to function-areas were given #s. #8=eye function, #17 location of images we see that are recorded & processed, #4= primary motor control area-where lg. sutures are located when young, #33, 1, 2 =somatic sensation (also where frontal fontanel suture located, prob. for young child) Brodman stimulated monkeys, now we use MRI with radioactive glucose which lights up areas being used at that moment.
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