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Neurology Block I
| Question | Answer |
|---|---|
| What part of the brain is responsible for declarative memory? | Medial temporal lobe (diencephalon) |
| What part of the brain is responsible for the skills and habits section of nondeclarative memory? | striatum |
| What part of the brain is responsible for emotional responses in simple classical conditioning? | amygdala |
| what part of the brain is responsible for skeletal musculature simple classical conditioning (nondeclarative memory)? | cerebellum |
| How do neurons change after training? | Have greater number of branches, greater number of synaptic varicosities |
| Path that granule cells take as they migrate | along radial glial cells from external granule cell layer --> cerebellar molecular layer --> purkinje cell layer --> granule cell layer |
| what composes lamellipodia and filipodia? | actin filaments |
| What is fasciculation? | bundling together of axons into tracts. Acts as guidance cue |
| What is the chemoaffinity hypothesis? | Positional information is encoded in the form of gradients of signaling molecules at the target. Complementary gradients of receptors on axons |
| How does Netrin 1 relate to the ventral midline? | It's a chemoattractant. After crossing the midline, axons that used to be responsive to it aren't anymore |
| what do Slit proteins do? | May function as positive regulators of axon collateral formation during the establishment or remodeling of neural circuits |
| what is the receptor for the slit protein? | It's on growth cones and is called Roundabout/Robo |
| How does Robo relate to the ventral midline? | Robo is downregulated on axons as they cross the midline, and then upregulated again, ensuring that is doesn't cross again. |
| are netrins diffusible or cell-associated? | both |
| What axonal receptors do netrins bind? | DCC/UNC-40 and UNC-5. Determines whether netrins are attractive or repulsive. |
| what do netrins do? | outgrowth and guidance of spinal cord axons |
| What do semaphorins do? | mediate growth cone collapse, axonal steering, axonal branching, axon terminal arborization. Repulsive factors for axonal guidance |
| What are receptors for secreted semaphorins? | neuropilins. Plexins can also associate w/ neuropilins, so plexins can help. |
| what are receptors for cell-associated semaphorins? | plexins |
| What does agrin do? | Found in motor neuron basal laminae.Encourages AChR clustering (organizes postsynaptic differentiation) |
| What is responsible for changes in ACh receptor density at the synapse? | 1) AChR inducing activity (ARIA) promotes increase in total AChR 2) Agrin induces clustering 3) Calcitonin gene related peptide (CGRP) --> inc. cAMP in muscle -->receptor synthesis |
| Does ACh release from nerve terminals cause increase in ACh receptors? | NO |
| How does NGF control cell survival? | competition for NGF occurs when multiple axons innervate single target. Innervating axons take it up via NGF receptors --> retrogradely transport --> no cell death |
| what is the NGF receptor? | tyrosine kinase (trkA) |
| What happens if axons of postsynaptic neurons are cut? | Presynaptic neurons withdraw their axon terminals |
| If you add NGF when a peripheral nerve is cut, what happens? | regeneration and reinnervation |
| Why are CNS neurons generally not regenerable? | In the adult brain, ECM molecules like laminin and fibronectin are no longer expressed. Also, oligodendroglia express growth inhibitory molecules |
| Do Schwann cells secrete NGF? | yes |
| Are MAPs in dendrites or axons of higher molecular weight? | dendrites |
| Are RER and ribosomes in all dendrites? | No, only in large dendrites |
| what is the predominant MAP in axons? | tau |
| Does axon have RER and ribosomes? | not past the initial segment |
| does axon hillock have organelles? | no |
| are there mitochondria in the nerve terminal? | yes, lots |
| what type of neuron is most common? | multipolar |
| Golgi Type I vs Golgi Type II neurons | Golgi Type I cells are small and usually interneurons. Type II are larger. |
| Which is more abundant in dendrites, neurofilaments or microtubules? In axons? | Neurofilaments more abundant in axons, microtubules more common in dendrites |
| What do the macroglia originate from and what types are there? | Arise from ectoderm. Consist of astrocytes, oligodendrocytes, and ependymal cells |
| What do microglia originate from? | mesoderm |
| where are protoplasmic astrocytes generally found? | gray matter |
| where are fibrous astrocytes generally found? | white matter |
| what forms glia limitans? | fibrous astrocytes |
| do protoplasmic astrocytes form sheets? fibrous? | protoplasmic do, fibrous don't |
| do fibrous astrocytes tend to conform around axons? | no |
| what is the predominant cell type in white matter? | oligodendroglia |
| where can oligodendroglia be found in gray matter? | near neurons, therefore known as perineuronal satellite cells |
| do oligodendroglia have definite perivascular feet? | no |
| where are oligodendroglia located in white matter? | as rows of cells between groups of neuronal processes |
| Do oligodendroglia have glial fibrils | no |
| role of oligodendroglia | formation and maintenance of myelin |
| what do schwann cells do? | responsible for myelination in PNS |
| what are ependyma derived from? | ectoderm |
| where do you find ependymal cells? | line ventricles of brain and central canal of spinal cord as simple columnar epithelium |
| do ependymal cells rest on basal lamina? | no, except at choroid plexus |
| where do you find microglia? | throughout CNS but normally inconspicuous. More abundant in gray matter |
| what are microglial nuclei like? | elongated and triangular, deeply stained |
| What are the two components of the prosencephalon? | Forebrain. Telencephalon (forebrain) and diencephalon |
| 2 components of the brain stem | mesencephalon (midbrain) and rhombencephalon (hindbrain) |
| components of telencephalon | cerebral lobes, basal ganglia |
| components of diencephalon | epithalamus, thalamus, hypothalamus, subthalamus |
| what does the precentral gyrus do? | controls somatomotor on contralateral side of brain |
| three components of inferior frontal gyrus | opercular part, triangular part, orbital part |
| Broca's area | Pars opercularis + pars triangularis, on dominant side of brain (L side in R handed individuals). Productive speech |
| what does the postcentral gyrus do? | somatosensory |
| where are the supramarginal and angular gyri? | in the inferior parietal lobule |
| What does the supramarginal gyrus form a cap over? | lateral fissure |
| what does the angular gyrus form a cap over? | superior parietal sulcus |
| what are the uncus and the anterior part of the parahippocampal gyrus part of? | primary olfactory cortex |
| what does the inferior parietal sulcus separate? | the inferior temporal lobe from the occipitotemporal sulcus |
| where is Wernicke's area? | posterior part of the superior temporal gyrus. important for comprehension of language |
| what is the superior bank of the superior temporal gyrus also known as? where is it located? what does it do? | AKA transverse temporal gyri of Heschl. In dorsal surface of temporal cortex. Primary auditory receiving area. |
| what part of the brain is the limbic lobe in? | telencephalon |
| what part of the rhombencephalon does the cerebellum belong to? | metencephalon |
| what part of the rhombencephalon does the medulla belong to? | myelencephalon |
| what is the internal capsule? | all of the fibers going to and coming from the cerebral cortex which form a fan-shaped mass of fibers called the corona radiata. Fibers of the corona radiata converge towards the diencephalon forming a prominent, compact bundle of axons: internal capsule |
| what types of fibers are in the internal capsule? | Thalamocortical and corticothalamic fibers. Also corticofugal fibers: include the corticoreticular, corticopontine, corticobulbar and corticospinal tracts. Smaller projections also exist to the basal ganglia, other areas of the diencephalon & midbrain |
| components of the basal ganglia | Caudate, Putamen, Globus Pallidus, Subthalamic Nucleus and Substantia Nigra |
| components of the lentiform nucleus | Putamen, Globus Pallidus |
| components of corpus striatum | The lentiform nucleus and the caudate |
| what do the basal ganglia do? | major subunit of the motor control system that works with the cerebral cortex and other brainstem structures to program movements. |
| what kind of fibers are within the internal capsule? | projection fibers |
| what kind of fibers are in the external and extreme capsules ? | association fibers |
| what is the fornix? | The Fornix is a C-shaped structure that is a major input and output pathway of the hippocampus. It begins caudal to the hippocampus and arches superiorly close to the midline under the corpus callosum, then turns inferiorly and posteriorly toward hypotha |
| what does the anterior commissure link | interconnecting the middle and inferior temporal gyri |
| four parts of the diencephalon | Epithalamus, Hypothalamus, Thalamus and Subthalamus. |
| what is the thalamus? | collection of nuclei that have sensory, motor or association function. All sensory information traveling to the cerebral cortex (except for the olfactory pathway) reaches it by way of a thalamic nucleus with sensory function. |
| what does the hypothalamus do? | exerts important controls over visceral and endocrine activities. The hypothalamus is the major subcortical center for the regulation of both sympathetic and parasympathetic autonomic activities |
| rostral border of hypothalamus? | Lamina Terminalis and anterior commissure |
| caudal border of hypothalamus? | Mammillary Bodies |
| superior border of hypothalamus | Hypothalamic Sulcus |
| medial border of the hypothalamus | third ventricle |
| what is the cerebral peduncle? | Aka crus cerebri. made up of corticofugal fiber systems in the midbrain |
| what makes up the pyramids? | corticofugal fiber systems in the brain stem |
| nuclei of which cranial nerves are in brainstem? | CN III-CN XII |
| Cranial nerves with nuclei in the pons | trigeminal, the abducens, the facial, and the vestibulocochlear nerves. These nuclei are located within the pontine tegmentum along with the reticular formation, longitudinal fiber bundles and other important cell groups. |
| components of metencephalon | pons and cerebellum form the metencephalon |
| what fibers constitute most of the base of the pons? | pontocerebellar fibers), which are located in the interior of the pons, terminate within the cerebellum and are involved in the interaction of the cerebral cortex and cerebellum in regulating motor function |
| what fibers constitute pyramidal tract? | corticospinal fibers |
| what is the reticular formation of the pons? | receives the terminals of corticoreticular fibers (a sub-population of the corticofugal fibers). Some of these reticular formation neurons, in turn, send their axons to cranial nerve nuclei and are part of a system exerting cortical influences on these nu |
| what marks the inferior boundary between pons and medulla? | stria medullaris |
| what forms the anterior surface of the pons? | fibers of the middle cerebellar peduncles |
| what forms the walls of the fourth ventricle? | superior cerebellar peduncles |
| where is the tegmental portion of the pons? | extends from the base up to the floor of the fourth ventricle. |
| what's in the tegmentum? | cranial nerve nuclei, longitudinal fiber systems in continuity with those in the midbrain and medulla, as well as the reticular formation and other cell groups |
| what forms the facial colliculus? | abducens (VI) nucleus and the facial nerve root |
| what's on either side of the sulcus limitans in the pons? | facial colliculus and the more lateral sensory vestibular region |
| In a spinal cord reflex, what neurotransmitter is used by the sensory neuron? | Glutamate |
| Amplitude of synaptic potential in CNS vs neuromuscular junction | Neuromuscular junction: 50 mV. Spinal motor neuron: 1 mV |
| IPSP | depolarizing the interneuron --> transient hyperpolarization of motor neuron to be inhibited |
| Ionic mechanisms for IPSPs | selective increase in chloride permeability |
| neurotransmitter for spinal inhibitory neuron | glycine sometimes, but most often GABA |
| what does curare do? | competitive inhibitor of Ach receptors |
| Intrinsic (homosynaptic) vs extrinsic (heterosynaptic) pathway | Intrinsic: changes to synapse brought about by itself. extrinsic: brought about by different pathway |
| 2 types of homosynaptic plasticity | synaptic depression and facilitation |
| Synaptic depression | Action potential in sensory neuron --> EPSP in motor neuron. 2nd action potential in sensory neuron 200 mmsec later is smaller --> synaptic depression |
| synaptic facilitation | 2 action potentials in presynaptic cell produce 2 EPSPs in postsynaptic cell. 1st is 1 mV, but 2nd is much larger. --> larger net EPSP due to temporal summation (residual calcium) |
| 2 types of heterosynaptic plasticity | Presynaptic inhibition and presynaptic facilitation (both mediated by axoaxonic synapses) |
| Presynaptic inhibition | Action potential in presynaptic cell --> EPSP in postsynaptic cell. M1 (modulatory cell) makes axoaxonic synapse w/ presynaptic cell. After M1 fires, postsynaptic EPSP is smaller. M1 regulated ability of presynaptic cell to release neurotransmitter |
| Presynaptic inhibition and calcium | Modulatory transmitter engages metabotropic receptors --> 2nd messenger system --> phosphorylates Ca2+ channels --> open less readily --> less Ca2+ influx --> smaller EPSP |
| Presynaptic inhibition vs facilitation | Presynaptic inhibition directly modulated Ca2+ channel; facilitation affects Ca2+ channel via modulation of K+ channel |
| How does presynaptic facilitation work? | M2 activated 2nd messenger cascade --> fewer K+ channels available to be opened in presynaptic terminal --> broader action potential, more time for Ca2+ influx --> more neurotransmitter released |
| what is Long Term Potentiation (LTP) important for? | storing memory |
| what is the NMDA-type receptor critical for? | some forms of LTP (long term potentiation), particularly at the CA3-CA1 synapse in the hippocampus |
| what kind of glutamate receptors do the postsynaptic spines of CA1 neurons in the hippocampus have> | NMDA-type glutamate receptors and non-NMDA type glutamate receptors. Both are permeable to Na+ and K+ |
| How is the NMDA-type glutamate receptor different from the non-NMDA type glutamate receptor? | 1) Significant permeability to Ca2+ 2) normally blocked by Mg2+ |
| what do the vinca alkaloid drugs (colchicine and vinblastine) do? | disrupt microtubules and prevent axonal transport |
| How does Ca++ influx cause translocation to the active zone? | Increasing Ca++-dependent phosphorylation of synapsin, which frees vesicles from binding to actin |
| what do clostridia toxins do? | target proteins in vesicle membrane to block synaptic transmission |
| what vesicle protein is affected by botulinum toxins A and E, and where is it? | SNAP-25 on synaptic plasma membrane |
| What does Botulinum toxin C1 affect and where is it? | Syntaxins, on synaptic plasma membrane |
| What do Botulinum toxin B,D,F,G and tetanus toxin affect and where is it? | VAMP (Synaptobrevin), on synaptic vesicle |
| What is n-sec1? | a synaptic plasma membrane protein.loose association w/ plasma membrane proteins prevents binding of neurotransmitter vesicle proteins until it's displaced and a trimeric complex forms. |
| what is synaptotagmin? | a protein which may act as Ca++ sensor (has 2 binding sites for Ca) for fission of plasma membrane to synaptic vesicle |
| What neurotransmitter usually mediates excitatory transmission (Type I)? | Glutamate |
| what neurotransmitters mediate inhibitory transmission (Type II)? | Glycine in spinal cord, GABA in brain |
| where are excitatory synaptic connections often found? | on spines of dendrites |
| where are inhibitory synapses generally located? | near neuronal soma |
| What do you need more of to cause an action potential, axodendritic excitatory synapses or axosomatic dendritic synapses? | Axodendritic excitatory synapses (b/c further from axon) |
| How are excitatory amino acid neurotransmitters charged? Inhibitory ones? | Excitatory 2 negative charges on 2 carboxylate groups. Inhibitory: 1 neg charge |
| What is N-methyl-D-Aspartate? | Synthetic compound. AGONIST that mimics action of glutamate on certain glutamate receptors |
| where does GABA come from? | Unlike all other amino acid neurotransmitters, GABA is not a product of intermediary metabolism. Is produced by an enzyme located in neurons. |
| how do glial cells recycle excess glutamate? | Glutamine synthase: glutamate --> glutamine, which can cross plasma membrane |
| what does strychnine do? | Blocks glycine binding to receptor on postsynaptic neurons. Because glycine is inhibitory, this leads to hyperexcitation --> asphyxiation due to hypertense diaphragm |
| How is GABA made? | made from glutamate by glutamic acid decarboxylase (GAD). Antibodies to GAD identifies GABA neurons |
| What is the GABA shunt? | For GABA reuptake. GABA is first converted back to glutamate by GABA transaminase in mitochondria using COOH from a-ketoglutarate. Then glutamate --> glutamine, which diffuses back to neuron --> back into glutamate |
| what is purinergic transmission? | ATP in vesicles --> degrades to adenosine, which is itself a neurotransmitter. This can also modify the pre or postsynaptic cell response if there are appropriate receptors; for example, adenosiine inhibits neurotransmitter release |
| Is there a known metabotropic receptor for glycine? | NO, ionotropic only (mediated through ion channel permeable to Cl-) |
| 3 types of glutamate receptors | 1) NMDA (ionotropic) 2) non-NMDA (aka kainate/AMPA receptors) (ionotropic) 3) metabotropic glutamate receptor |
| what receptors are responsible for most ESPSs? | non-NMDA receptors (mainly permeable to Na+ and K+) |
| How are glutamate receptors different from nicotinic ACh receptors? | Glutamate receptors have 5 subunits with 3 membrane spanning segments each (four for ACh receptor) |
| 2 important characteristics of NMDA receptors | 1) High permeability of Ca++ (also permeable to Na and K) and 2) require both ligand binding and membrane depolarization to open |
| What is associativity (re: the NMDA receptor?) | senses both presynaptic activity and postsynaptic activity --> learning |
| Are GABA-A receptors postsynaptic or presynaptic? GABA-B receptors? | GABA-A: postsynaptic. GABA-B: presynaptic |
| How do GABA-A receptors act? GABA-B? | GABA-A: ionotropic, opens Cl- channel. GABA-B: alters second messengers |
| Is GABA-A a fast or slow response receptor? Is GABA-B? | GABA-A: rapid response. GABA-B: slow response |
| How many subunits in GABA-A? GABA-B? | GABA-A: multisubunit, can bind modulators. GABA-B: single subunit |
| Structure of GABA-A receptor | 5 subunits with 4 membrane spanning domains each. Highly related to nicotinic ACh receptor. Cl- channel b/c of + charged aa's |
| what subunit of the GABA-A receptor does GABA bind? | alpha receptor |
| What subunit of the GABA-A receptor do Benzodiazepenes (Valium, Lithium) bind? | gamma subunit |
| what subunits of the GABA-A receptor do barbiturates bind | both alpha and beta subunits |
| Where does picrotoxin bind the GABA-A receptor? | blocks ion flow through receptor |
| What effect do benzodiapemines have? | Enhance GABA binding to receptor, enhancing GABA's ability to hyperpolarize the neuron by opening the Cl- channel |
| What do barbiturates do? | enhance GABA binding to receptor |
| what does strychnine do? | blocks glycine receptor |
| structure of glycine receptor | at least 2 subunits w/ 4 membrane spanning regions each |
| How does the metabotropic glutamate receptor act? | Activates phospholipase C --> IP3 and DAG from PIP3. IP3 --> Ca release. Ca + DAG -->activate protein kinase C |
| what happens if glutamate is not removed from the synapse? | Uncontrolled opening of receptors --> large influx of Na+ --> swelling. Large Ca influx --> hyperactivation of Ca-dependent enzymes |
| what is tissue plasminogen activator (tPA)? | clot breaking agents used to treat strokes |
| Are glutamate receptors involved in Alzheimer's and Huntington's chorea? | yes |
| what happens in focal epilepsy? | decreased local GABA-mediated inhibition --> cells fire synchronously --> massive local excitation. Treat by hyperpolarizing w/ barbiturates |
| what is the neurotransmitter in the preganglionic sympathetic and preganglionic parasympathetic neurons? | ACh |
| what is the neurotransmitter at the adrenal medulla? | ACh |
| What is the neurotransmitter of all parasympathetic-innervated organs? | ACh |
| What's the neurotransmitter at the NMJ in the PNS? | ACh |
| Where in the CNS is ACh found? | Primarily in interneurons although a few long-axon cholinergic pathways have also been found (eg, cholinergic projection from the nucleus basalis of Meynert in the basal forebrain to the forebrain neocortex and associated limbic structures). |
| What synthesizes ACh and from what? | Single step reaction via Choline Acetyltransferase (CAT) made in cell body and moved down to axon terminals. Acetyl CoA + Choline --> ACh |
| Rate-limiting steps of ACh synthesis | Availability of choline and Acetyl CoA. Increased neuronal activity increases acetyl CoA availability from mitos, increases choline uptake into nerve ending from synaptic cleft. Ca involved in regulating these mechanisms. |
| Inactivation of ACh -->? | choline and acetic acid |
| 2 sources of choline for ACh synthesis | ACh breakdown in synaptic cleft and breakdown of phosphatidylcholine |
| How is ACh stored in the vesicle? | Energy-dependent pump acidifies vesicle. Then uses vesicular ACh transporter (VAChT) to exchange protons for ACh |
| 2 broad classes of ACh receptors | Nicotinic and muscarinic |
| Where are nicotinic receptors found? | NMJ, autonomic ganglia, sparsely in the CNS |
| Structure of NMJ nicotonic ACh receptor | 5 subunits (4 types): two alpha, 1 each beta, delta, and gamma. Funnel-shaped Na channel between. Each subunit has N extracellular, C intracellular. Each subunit spans membrane 5 times. |
| where on the nicotinic ACh receptor are the primary binding sites? | alpha subunits |
| How many subunits does the neuronal nicotinic receptor have | 5 subunits, 2 types (2 alpha, 3 beta) |
| Where are muscarinic receptors found? | parasympathetic visceral organs, and both pre- and post-synaptically in the CNS |
| Structure of muscarinic receptor | Single polypeptide w/ 7 regions made up of 20-25 aa's arranged in an alpha helix. 3rd internal loop + C terminal = site of interaction w/ G proteins |
| 3 responses mediated by muscarinic receptors through G proteins | 1) Inhibition of adenylate cyclase 2)Stimulating phospholipase C 3) Activating K+ channels |
| What happens when adenylate cyclase is inhibited due to activity of muscarinic receptors? | Decreased cAMP -->reduced activation of cAMP-dependent protein kinase --> reduced heart rate and contraction strength. |
| What variety of acetylcholinesterase (AChE) is found at the NMJ? | Heteromeric, composed of 4 subunits coupled to collagen tail anchoring enzyme in matrix. In contrast, other isoforms are homomeric and soluble in presynaptic cell cytoplasm. |
| Is AChE found in non-cholinergic neurons? ChAT? | AChE is, but not ChAT |
| what are pseudocholinesterases? | cholinesterases found throughout body that can metabolize ACh |
| what do isopropylfluoroesters do? | Irreversibly inhibit AChE, so ACh stays in synaptic cleft and accumulates, keeps receptors occupied, thereby paralyzing muscles of respiration --> death |
| What is the mechanism for insecticides and war gases? | Irreversibly inhibit AChE by carbamylating it, inactivating both acetyl binding domain and choline binding domain |
| What does eserine (physostigmine) do? | Reversibly inhibits AChE. Therapeutic. |
| Is the action of ACh on nicotinic receptors always excitatory? | yes |
| Can muscarinic receptors be either excitatory or inhibitory? | yes |
| 2 examples of how muscarinic receptors mediate behavior in the CNS | 1) Have role in modulating motor control circuits in basal ganglia 2) participate in learning and memory (which we know b/c their antagonic are amnesic, and deterioration of cholinergic innervation in the neocortex is associated w/ Alzheimer's) |
| How do atropine and other anticholinergics work? | Block muscarinic receptors |
| Clinical uses of atropine | Relaxes eye muscles --> pupil dilation. Also slows gut activity and acid secretion |
| How does scopolamine act? | blocks CNS muscarinic receptors |
| Clinical use of scopolamine | Used topically to treat motion sickness |
| How does amantadine (Symmetrel) act? | blocks muscarinic receptors |
| Clinical use of amantadine (Symmetrel) | Antidyskinetic used to treat Parkinson's disease and dyskinesia associated w/ antipsychotics |
| How does bethanechol act? | Mimics ACh |
| Clinical uses of bethanechol | Treat urinary retention, stimulate intestinal tract movement |
| How does Tacrine (Cognex) act? | blocks ACh breakdown |
| Clinical use of Tacrine (Cognex) | treat Alzheimer's |
| How does eserine (physostigmine) act? | blocks ACh breakdown |
| Clinical use of eserine (physostigmine) | reduces pressure in eye --> treat glaucoma. Also used to diagnose and treat myasthenia gravis |
| where do the anterior choroidal arteries arise from and what do they supply? | arising from the internal carotid lateral to the origin of the posterior communicating arteries. Besides supplying the choroid plexus of the lateral ventricles, also provide branches to the core of the parahippocampal gyrus and posterior internal capsule |
| what does the anterior cerbral artery arise from and what does it supply? | Arises from internal carotid bodies. Major branches supply the medial surface of the frontal and parietal cortex and much of the corpus callosum. Small branches enter anterior perforated substance to supply portions of the hypothalamus. |
| what are leptomeningeal anastomoses? | between the anterior cerebral and middle cerebral arteries. They permit blood flow from cortical branches of one cortical arterial territory to the other. |
| What's the medial striate artery ((Recurrent Artery of Heubner) ? | Arises from anterior cerebral artery before it passes through longitudinal fissure. Medial striate artery passes laterally and enters the brain to supply medial areas of the corpus striatum of the basal ganglia and anterior internal capsule. |
| What branches does the middle cerebral artery give off and where do they go? | lateral striate arteries (lenticulostriate arteries). supply most of the lateral areas of the corpus striatum of the basal ganglia and the internal capsule. |
| What happens if the lateral striate arteries get occluded? | Basal ganglia starve --> motor deficits |
| what do branches from the posterior communicating arteries supply? What does the posterior communicating artery arise from? | Arises from internal carotid artery. Branches supply rostral and medial regions of the diencephalon |
| where do the posterior cerebral arteries arise from? | Usually basilar but sometimes internal carotid |
| What do the cortical branches of the middle cerebral artery supply? | most of the lateral aspect and some of the inferior aspect of the cerebrum. |
| what do the cortical branches of the posterior cerebral artery supply? | Inferior part of temporal lobe, entire occipital lobe. |
| what's the posterior choroidal artery derived from and what does it supply? | Derived from posterior cerebral artery, supplies choroid plexus of the lateral and third ventricles and the superior aspect of the thalamus and the midbrain tectum. |
| what parts of the brain will be affected by internal carotid thrombi? | forebrain |
| course of the vertebral arteries | pass over the anterior surface of the medulla and give rise to posterior spinal arteries, anterior spinal arteries and posterior inferior cerebellar arteries. vertebral arteries pass rostrally and unite near pontomedullary junction to form basilar artery. |
| course of posterior spinal artery | arise from the vertebral arteries and descend along the posterolateral aspect of the medulla and spinal cord |
| what do anterior spinal arteries do? | supply the anterior and midline regions of the medulla. These arteries merge to form a single artery which descends in the anterior median fissure of the spinal cord. |
| what does the posterior inferior cerebellar artery usually arise from and where does it go/supplies what? | Usually from vertebral a. Goes along lateral and posterior medulla. Supplies that part of medulla, inferior cerebellum, choroid plexus of 4th ventricle |
| where does basilar artery branch to form posterior cerebral arteries? | caudal to mammillary bodies |
| where do the anterior inferior cerebellar arteries arise? | From basal artery near pontomedullary junction. It is the most caudal large artery originating directly from the basilar artery. |
| what does the anterior inferior cerebellar artery supply? | inferior parts of the cerebellum lateral to that supplied by the posterior inferior cerebellar artery. It also provides branches to the caudal pontine tegmentum and to the choroid plexus of the fourth ventricle. |
| what do the paramedian branches of the basilar artery supply? | provide blood to structures in the basal and medial tegmental regions of the brain stem |
| where do the superior cerebellar arteries arise from the basilar artery? | near the pons-midbrain junction. |
| course of superior cerebellar artery | travels along the lateral surface of the pons and subdivides to provide branches to the superior surface of the cerebellum & to deep cerebellar nuclei and white matter. Small branches also provide blood to rostral part of posterior pontine tegmentum |
| Posterior cerebral artery | Arises from bifurcation of basilar artery. Cortical branches supply cuneus and lingual gyri of occipital lobe, inferior part of temporal lobe, lateral occipital gyri |
| what artery provides blood supply to visual cortex. What happens if one of these arteries is occluded? | Posterior cerebral artery. Occlusion leads to blindness on contralateral side. |
| where does the lateral olfactory stria terminate? | in uncus and structures forming limbic system |
| where does the optic tract terminate? | thalamus of the diencephalon |
| which cranial nerves originate or end in the brainstem? | III --> XII |
| primary function of superior colliculus | S is for SIGHT |
| primary function of inferior colliculus | auditory |
| which cranial nerves are associated w/ the midbrain? | oculomotor (cranial nerve III) and the trochlear (cranial nerve IV). |
| where does CN III emerge? | in midbrain medial to crus cerebri in interpendicular fossa |
| where does CN IV emerge? | in posterior midbrain just caudal to the inferior colliculus |
| what forms the caudal border of the pons? | stria medullaris |
| what cranial nerve is associated with the pons proper? | CN V |
| what nerves are located at pontomedullary junction? | abducens nerve (cranial nerve VI), the facial nerve (cranial nerve VII), and the vestibulocochlear nerve (cranial nerve VIII). |
| what does portio major of CN V do? | sensory to the face |
| what does portio minor of CN V do? | muscles of mastication |
| where does CN V leave the pons? | anterolateral aspect of the pons about halfway between its rostral and caudal borders |
| Where does CN VI leave the pontomedullary junction? | in the pontomedullary sulcus a little lateral to the pyramid. |
| what does the nervus intermedius of the facial nerve do? | taste of anterior 2/3 of tongue |
| where is the primary auditory receiving area in the cerebral cortex? | superior bank of the superior temporal gyrus. |
| what is the cerebellopontine/cerebellomedullary angle? | area where CNVII, VIII and IX are found. Can have tumors that affect all of these at once. |
| what's in the preolivary sulcus? | rootlets of CN XII |
| what's in the postolivary sulcus? | rootlets of the glossopharyngeal nerve (cranial nerve IX), the vagus nerve (cranial nerve X), and the spinal accessory nerve (cranial nerve XI). |
| what are catecholamines? | dopamine (DA), norepinephrine (NE), epinephrine (E). Named b/c of hydroxylated phenol ring known as catechol nucleus |
| principle member of indolamine family of neurotransmitters | serotonin (5-hydroxytryptamine, 5-HT) (there's also melatonin) |
| what is the neurotransmitter in postganglionic sympathetic neurons? | norepinephrine |
| Where does DA (dopamine) work as a neurotransmitter? What does it do? | Modulates cholinergic transmission in autonomic ganglia, and stimulates renal vasodilation and inhibits Na and H20 reabsorption in the kidney |
| what's the epinephrine: norepinephrine ratio released from adrenal medulla? | 4E:1NE |
| where is serotonin found peripherally? | In GI tract and in platelets |
| Which monoamines are neurotransmitters in the CNS? | All of them (catecholamines, indolamines, histamines) |
| where are the cell bodies of monoamine neurons generally found? Where do the axons extend to? | Cell bodies found in clusters in midbrain or brainstem, project to other brain or spinal cord regions |
| Which has a more extensive projection, NE or DA? | NE |
| where is the major site of DA cell bodies? | midbrain |
| Four DA systems in midbrain | 1) Large mesostriatal system 2) Mesolimbocortical system 3)Periventricular system 4)Tuberohypophyseal system |
| where's the major site of NE cell bodies? | medulla and pons |
| 3 groups of NE cells? | 1)Locus coerulus cell group 2)Lateral tegmental cell group 3)Dorsal medullary cell group |
| What is volume transmission and where is it found? | Found in NE cells. NE, once released, diffuses widely to influence any number of cells |
| 2 clusters of serotonin cells | One in brain stem, other in caudal midbrain. Both project widely through the CNS |
| Where are histamine cells located in the CNS? | Exclusively in basal posterior hypothalamus |
| what does histamine probably do, neurologically? | behavioral and physiological functions |
| First step in synthesis of DA, NE, and E | Hydroxylation of tyrosine to form L DOPA via tyrosine hydroxylase (TH) |
| First step in 5HT synthesis | hydroxylation of tryptophan via tryptophan hydroxylase (TryH) |
| Second step in monoamine synthesis | Products of hydroxylation step by Aromatic Amino Acid Decarboxylase (AADC) to form the monoamine |
| what's the final step of NE synthesis and where does it occur? | NE is formed from dopamine via hydroxylation of the 2nd carbon of the side chain. Occurs within monamine storage vesicle |
| What do tyrosine and tryptophan hydroxylases need to function? | Molecular oxygen, iron, BH4 |
| what vitamins are required for synthesis of monoamines? | Vitamin B6 necessary for decarboxylation, Vitamin C required for conversion of DA to NE in storage vesicle |
| How is epinephrine synthesized? | Made in adrenal medulla and CNS by methylation of NE on N-terminus, catalyzed by Phenyl Ethanolamine N methyl transferase (PNMT), which uses SAM. |
| Where is PNMT located and what does this mean? | Found outside storage vesicle, so NE has to be shuttled out of the vesicle and then back in for storage and release as E |
| How is histamine synthesis different from catecholamines and 5HT? | Does not require hydroxylation |
| How is histamine made? | Single step decarboxylation of histidine analogous to decarboxylation of L DOPA and 5HTP |
| What vitamin does histidine carboxylase need to make histamine? | Vitamin B6 |
| How is catecholamine biosynthesis regulated? | Concentration kept stable through short-term phosphorylation of regulating enzyme TH, and long-term regulation of gene transcription of TH mRNA and TH mRNA stability |
| how is serotonin biosynthesis regulated? | Amt of tryptophan available. Since people don't make tryptophan, this depends on diet. Because trp is transported across blood-brain barrier, a high protein diet can lower CNS 5HT levels by competition |
| what are "dense core vesicles"? | monoamine vesicles |
| what are monoamines complexed with in storage? | Complexed w/ ATP and chromagranins (including D-beta-H, the enzyme that converts DA to NE) |
| How do monoamines get into vesicles? | exchange of H+ for MA |
| what does reserpine do? | inhibits uptake of monoamines into storage vesicles |
| How do monoamines feed back onto presynaptic cell? | Presynaptic receptors are stimulated --> MA synthesis stimulated, MA release inhibited |
| Structure of pre- and post-synaptic MA receptors | G-protein linked w/ 7 membrane domain structure similar to muscarinic receptors |
| Mechanisms of monoamine receptor activity | 1)stimulate or inhibit adenylate cyclase 2) stimulate PCB-beta 3)direct influence of G protein on ion channel conductance |
| what do alpha catecholamine receptors in the iris do? | cause pupil dilation |
| what do alpha catecholamine receptors in the spleen do? | contraction, via linkage to IP3 production |
| what do alpha catecholamine receptors in the bladder do? | contraction via linkage to IP3 production |
| what catecholamine receptors are in the heart? | Beta-1 |
| What catecholamine receptors in fat cells? | Beta-3 receptors, induce lipolysis |
| What are B catecholamine receptors linked to? | cAMP production |
| what are alpha catecholamine receptors linked to? | IP3 production |
| what synaptic action do alpha catecholamine receptors cause? | contraction (and pupil dilation) |
| synaptic action for most beta catecholamine receptors cause? | relaxation |
| What does the D1 dopamine receptor family do? | decreased excitability due to cAMP production |
| Where is the D1 family of dopamine receptors located? | In caudate - putamen, nucleus accumbens, olfactory tubercles, hippocampus, hypothalamus |
| What does the D2 family of dopamine receptors do? | increase excitability due to decreased cAMP production |
| Where are D2 family dopamine receptors located? | Caudate-putamen, nucleus accumbens, olfactory tubercles, frontal cortex, diencephalon,brain stem |
| What 5HT receptor is NOT part of the G protein coupled receptor superfamily? | 5HT-3 receptor (ligand-gated ion channel) |
| What characterizes all histamine receptors? | All are G protein linkes, all present in CNS as well as periphery |
| What receptors do antihistamines block? | H1 receptors |
| What responses are H2 receptors for? | Histamine stimulation of gastric acid secretion |
| What do Tagamet and Zantac target? | They block H2 receptors, thereby inhibiting histamine stimulation of gastric acid secretion. Don't cross blood-brain barrier, so no CNS effects. |
| What do H3 histamine receptors do? | Found on histamine nerve terminals, regulate release of histamine and possibly other neurotransmitters |
| What does monoamine reuptake need? | Na and ATP |
| what effect does amphetamine have on histamine reuptake? | reverses transport direction, causing increased MA in the extracellular space |
| What effect does cocaine have on histamine reuptake? | Blocks reuptake of MA into the terminal, resulting in elevated MA in extracellular space |
| when does uptake of histamines into glial cells kick in? | Only at very high MA concentrations |
| When do released catecholamines diffuse into extracellular space and get catabolized by MAO or COMT? | following extremely high catecholaminergic neurons |
| What does monoamine oxidase (MAO) do? | On outer membrane of mitochondria. Metabolizes DA, NE, and 5HT by oxidative deamination |
| what does MAO metabolize DA to? | DHPA (aldehyde intermediate which has to be further metabolized by aldehyde reductase to make alcohol) |
| What does MAO metabolize NE to? | DHPGA (aldehyde intermediate which has to be further metabolized by aldehyde dehydrogenase |
| What does MAO metabolize 5HT to? | 5HIAA |
| What does COMT do? | It's an extraneuronal enzyme that inactivates catecholamines by methylating hydroxyls on the catechol ring. Methylates either MAO-processed catecholamines and non-processed ones |
| How is histamine metabolized? | HA is taken up into cells and methylated by histamine methyltransferase (HMT) to form telemethylhistamine. MAO then oxidizes that to TMI |
| Metabolites of dopamine | DOPAC if just processed by MAO; HVA if processed by COMT and MAO |
| What are the metabolites of norepinephrine? | VMA and MHPG if processed by both MAO and COMT. Normetanephrine (trace) if only proceessed by COMT |
| Where is VMA found? | PNS sympathetic neurons |
| Where is MHPG found? | Brain mostly, less in PNS |
| What is the metabolite of epinephrine? | Metanephrine (mainly) when processed by COMT |
| What is the metabolite of serotonin? | 5-HIAA when processed by MAO |
| where is 5-HIAA found? | Brain and PNS |
| What is the metabolite of histamine? Where is it found? | TMI. Found peripherally. |
| what happens when have low NE? high NE? | Low --> dpression. High --> mania |
| what is serotonin important for? | appetite regulation (pathway monitors carbohydrate and acts as negative regulator mediated by 5HT in hypothalamu s) |
| What neurotransmitter is important in aggressive behavior? How? | 5HT (serotonin). Low 5HT --> increased aggression and decreased dominance |
| What happens if have low levels of 5HT? | Increased aggression, decreased dominance, depression, suicide (especially early in life) |
| What happens if have too much DA? | Schizophrenia, movement disorders |
| What happens if have decreased DA levels in substantia nigra and striata? | Critical lesion in Parkinson's disease (degeneration of DA neurons) |
| Why is L-DOPA used to treat Parkinson's? | b/c can be converted to DA by AADC in cells |
| what problems are associated w/ NE? | unipolar and bipolar disorders |
| What are SSRIs and how do they work for what? | Selective serotonin reuptake inhibitors, used to treat depression |
| What's used to treat obsessive-compulsive disorders? | 5-HT reuptake blockers |
| what is fenfluramine? | controversial 5HT reuptake blocker sometimes used to treat eating disorders. Similar to amphetamine |
| What is carbidopa? | Converted to DA in CNS only, used to treat Parkinson's |
| What does Isoproterenol (Isuprel) and what does it do? | Stimulates B receptors to dilate arteries and bronchii. |
| What does atenolol do? | Blocks B receptors to treat hypertension, coronary artery disease,angina, arrhythmia, migraine,hyperthyroidism |
| How does Sumatriptan (Imitrex) work? | Stimulates 5HT1 receptors to treat hypertension or migraine |
| How are neuropeptides and NO different from classical neurotransmitters? | Ignore directionality of information flow, just spray over large volume of area from point of release |
| are neuropeptides producers of fast or slow responses? | slow |
| are neuropeptide receptors ionotropic or metabotropic? | always metabotropic |
| Do neuropeptides always produce an obvious electrophysiological change in the postsynaptic neuron? | no |
| 5 neuropeptide families | Tachykinins, insulins, somatostatins, gastrins, opioids |
| Biosynthesis of neuropeptides | Made from larger precursors via proteolytic processing --> go froom Golgi to nerve ending via fast axonal transport. Cleavage happens during its travel |
| 3 types of proteolytic processing which occur in neuropeptide synthesis | 1) endopeptidase 2)carboxypeptidase cleaves basic residues from C terminus of new peptide 3) Conversion of COO on Gly at C terminus to NH2 group |
| are vesicles releasing neuropeptides larger or smaller than those for other neurotransmitters? | larger |
| do neuropeptide vesicles require presynaptic specialization for release? | no |
| What do spinal motor neurons often co-release? | ACh and calcitonin gene-related polypeptide (CGRP). CGRP --> activate adenylate cyclase --> up cAMP --> potentiates force of contraction produced by ACh activation of nicotinic ACh receptor |
| Are neuropeptides terminated via reuptake? | no |
| Do neuropeptides have higher or lower affinities for their receptors than normal neurotransmitters? | higher (slow dissociation) |
| How does nitric oxide synthetase (NOS) make NO? | Uses arginine as substrate, produces NO and citrulline. In response to elevated Ca levels |
| where is NOS found? | In most endothelial cells and 1-2% of cortical neurons |
| What cofactors does NOS use? | NADPH, FAD, FMN |
| How does NO influence guanylyl cyclase? | Activates it by binding to iron in the heme associated w/ guanylyl cyclase --> increase cGMP levels --> activates cGMP-dependent protein kinase --> decreased Ca levels in smooth muscle --> relaxation |
Created by:
saral