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146 Cards in this Set
- Front
- Back
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What class of active transport protein is the sodium-potassium pump?
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It is a P class ATPase (ATP driven) pump that pumps a # of Na+ out for two K+ pumped in
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Why is the sodium-potassium pump called a P class pump?
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Because the transport protein itself is phosphorylated
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What are P segments?
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Loops in a transmembrane domain of an ion channel that project into the pore and determine the charge and size of the opening
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What has to happen to an ion before passing through an ion channel?
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It has to lose its hydration shell and have those bonds replaced by carbonyl oxygen molecules that are part of the pore protein
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Under resting conditions, which side of the membrane is negative and what is the electrical potential?
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The internal side of the membrane is more negative and the potential is ~ -90mV
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What gives the inside of the cell its negative charge?
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Proteins and phosphates fixed inside the cell give the anionic charge
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At rest the membrane is permeable to K+ but not Na+. Why doesn't all the K+ flow out of the cell?
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As K+ flows out, the non-diffusable anions build up at the inner membrane surface and a potential is created. This charge difference opposes further diffusion of K+ out of the cell.
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What happens to ion concentrations during an action potential?
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The cell becomes permeable to Na+ and becomes depolarized to ~ 60mV. This is quickly reversed and ion conc. is restored by pumps
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Why do pacemaker cells of the heart have a less negative resting potential?
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Under normal circumstances they have a higher permeability to Na+ so the potential is less
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How does a membrane become HYPERpolarized?
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It is usually due to an increase in Cl- ions inside the cell or a decrease of K+ inside the cell
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How are mechanosensitive channels in snesory neurons activated?
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They are activated by stretching or deforming the membrane. This is a graded response (more stretch=greater activation)
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What is a receptor potential?
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When an ion channel is opened and Na+ permeability increases. If the depolarization is sufficient, an action potential is generated.
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As more and more stimulus is applied to sensory receptor, how does the nerve respond?
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The frequency of action potentials increase (not the magnitude). Frequency conveys intensity
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What is a tonic receptor?
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It adapts slowly to a stimulus and conveys information about the duration of a stimulus (ex. merckels and ruffini corpuscles)
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What is a phasic receptor?
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It adapts rapidly to a stimulus and conveys information about rapid changes in intensity and rate (ex. meissners and pacinian corpuscle)
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What type of mechanoreceptors are commonly found in the PDL to help assess bite intensity?
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Ruffini corpuscles
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How is high-background K+ permeability maintained in the cell?
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By housekeeping K+ channels that are open most of the time
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What is the structure of a voltage-gated K+ channel?
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It is a tetramer, each monomer consisting of 6 transmembrane alpha-helixes
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What is the structure of a voltage-gated Na+ channel?
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It is a gigantic monomer of 4 alpha-helix groups all connnected
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What is a voltage-sensing helix?
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It is the fourth helix in each group of Na+ or K+ channels that contains a charged amino acid. It causes the pore to open when the membrane becomes depolarized.
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How does Lidocaine work?
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It blocks the voltage gated Na+ channels from the cytosolic side (drug must permeate the membrane)
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What is a channel-inactivating segment?
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It is a cytosolic voltage-sensing region of the channel that gets pulled up into the vestibule and closes the channel following membrane depolarization.
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How is positive charge displaced during an action potential in a myelinated nueron?
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By electrotonic displacement to the node of Ranvier
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What prevents backward propagation of an action potential?
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The channels have a short refractory period while membrane potential is restored
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How does myelination effect propagation of action potentials?
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It increases membrane resistance, length constant, and axonal conduction velocity
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Which cells myelinate axons in CNS and PNS?
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In CNS it is oligodendrocytes and in the PNS it is Schwann cells
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What is the effect of pH on Lidocaine function?
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The drug must enter the cell in a neutral form. In acidic medium it becomes positively-charged and can't get into the cell. Once inside cell it becomes positively charged and can't get out
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What are Nissel bodies?
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They are collections of rough ER that can be seen in the cell body of neurons
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Characteristics of neuron soma
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Abundant rough ER, less smooth ER, large Golgi complex, and mitochondria with lamellar cristae. Also has lipofucsin and lipid droplets
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What is the function of dendritic spines?
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This is where the synapses form. They tend to diminish with age, inadequate nutrition, neuronal diseases, and Down syndrome.
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What is transported in anterograde axonal transport?
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Cell maintanance proteins and neurosecretory products. Can be as rapid as 400mm/day
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What is transported in retrograde axonal transport?
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Proteins for building neurofilaments and microtubules, and enzymes and endocytosed material. Some viruses also do this. Can be quite slow, about 0.2mm/day
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What is glial fibrillary acidic protein (GFAP)?
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Astrocytes use it to make intermediate filament bundles to help support the connections they make with surrounding structures.
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Functions of astrocytes
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Mediate metabolic exchange of waste and nutrients between neurons and blood, form blood brain barrier, and help remove deleterious substances from the extra cellular fluid
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What is astrogliosis (gliosis)?
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Damage to the CNS of some type that illicits an overactive repair response from astrocytes. They form abundant scar tissue (called astrocytic mat) that axons can't get through
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What is the function of oligodendrocytes?
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They are the myelin producing cells of the CNS. One of these can cover many different axons.
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What is the function of microglial cells?
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They are the macrophages of the CNS, cleaning up and protect against pathogens. They are preferentially attacked by HIV
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What are ependymal cells?
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They are low columnar or cuboidal epithelia that line the ventricles. They are ciliated and help move the CSF
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What are the common causes/diseases of demyelination?
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Radiation, chemotherapy, MS, Guillan-Barre, and Lou Gherigs disease.
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How do excitatory and inhibitory synapses differ morphologically?
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Excitatory have thick post-synaptic density and wide synaptic cleft. Inhibitory have thin post-synaptic density and a narrow cleft
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What are common diseases associated with loss of neurotransmitters?
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Huntington's chorea (GABA) and Parkinson's disease (dopamine)
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What are the three coverings of a peripheral nerve?
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In order of largest to smallest fibers: epineurium, perineurium, and endoneurium
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What are Auerbach's and Meissner's plexi?
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Groups of ganglion cells in the gut. Without these the gut can't properly constrict (Crohn's disease)
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What are the five layers of the epidermis?
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From superficial to deep: Stratum corneum, lucidum, granulosum,spinosum and basale
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In what part of the body would you find stratum lucidum layer?
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Its only seen in very thick layers of skin, like the pads of the feet
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What gives the stratum spinosum its spiny appearance?
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The desmosomes that attach the cells to one another. This layer helps makes the skin impermeable
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What cells would you find in the stratum basale?
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Melanocytes, Merkel cells, and actively replicating cells. Skin is regenerated from this bottom layer
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How do skin cells become keratinized?
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Substances from keratohyaline granules combine with tonofibrils converting them to keratin
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What gives the skin its waterproofing?
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Keratinocytes produce membrane coating granules called lamellar bodies that contain glycophospholipid. This produces a hydrophobic layer that keeps water in
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What are the characteristics of white muscle fibers?
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Poor vascular supply, large nerve fibers, faster stronger contractions but easily fatigued. Poor in myoglobin
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What are the characteristics of white muscle fibers?
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Rich vascular supply, smaller nerve fibers, slower contractions and not easily fatigued. Rich in myoglobin
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Skeletal muscle
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Multiple peripherally located nuclei, long and cylindrical striated cells, contract voluntarily
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What are the surrounding layers of muscle fibers?
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Epimysium surrounds entire muscle, perimysium surrounds bundles of fibers, and endomysium surrounds each cell.
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Derivation of skeletal muscle cells
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Derived from myoblasts. Form myotubes and then start to form myofilaments and myofibrils
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What are contractile elements of muscle?
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Myofibrils (bundles full of myofilaments containing actin and myosin)
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What is a sarcomere?
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A section of a muscle fiber from Z disk to Z disk. Includes an H band and an A band. It is the basic unit of contraction
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What is troponin?
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3 subunit protein that is bound to actin helix. TnT binds to tropomysin, TnC binds to calcium, and TnI binds to actin and inhibits actin and myosin interaction
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What is tropomyosin?
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It runs in the groove of the helix and binds to troponin and actin to regulate actin-myosin interaction
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Myosin myofilament (thick filament)
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200-300 myosin molecules arranged in 2 antiparallel identical heavy chains and 2 pairs of light chains. The head region binds ATP
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Actin thin filaments
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G actin polymerized to form F actin. 2 chains arranged in alpha helix
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What does titin protein do
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Holds thick myosin filaments to the Z disk
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What are T-tubules?
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Transverse tubules, invaginations of the sarcolemma among the myofibrils that facilitate the conduction of depolarization
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What happens to the bands during muscle contraction?
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The I-band narrows, the H-band disappears, the Z-lines get closer, and the A-band remains unchanged
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Structure of cardiac muscle
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Striated involuntary muscle. These are long, branching, anastomosing fibers with a central oval nucleus. They are connected by cell junctions that form intercalated disks
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Main energy source of cardiac muscle
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60% of energy used is derived from triglycerides
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What is the function of atrial natiuretic peptide (ANP)?
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It is contained in secretory granules in cardiac muscle. It lowers blood pressure by decreasing the ability of renal tubes to resorb water
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What is a terminal cisternate?
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Enlarged portions of the SER that approximate the T-tubules. They have an abundance of Ca and can readily release it during action potential
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What is a triad/dyad and where do you find them?
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Made up of terminal cisternae and T-tubule. In cardiac muscle it is one of each, in skeletal there are 2 terminal cisternae (triad)
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What are the two types of cell junctions in cardiac muscle?
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Transverse (desmosomes) and lateral (gap junctions). These are in the intercalated discs.
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explain calcium triggered calcium release
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Depolarization of the membrane causes membrane calcium channels to open and allow Ca inside. This binds to calcium releasing channel on SR and more calcium is released
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Characteristics of smooth muscle
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No striations, tapered cells with single centrally-located nucleus. No T-tubules, contracts involuntarily.
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What are the two types of smooth muscle cells and how do they differ?
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Multiunit contract independently, they have their own nerve supply. Unitary don't, they have gap junctions between adjacent cells and share a nerve supply.
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What other important function does smooth muscle do aside from contraction?
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Lots of protein secretion: collagen, elastin, GAGs, proteoglycans, and growth factors
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What are unique about the myofilaments of smooth muscle?
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No troponin, caldesmon blocks the active site of F-actin. Also, myosin S1 heads project from thick filaments throughout the entire length and allow contractoins of long duration
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What are intermediate filaments?
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Vimentin and desmin (unitary smooth muscle) and desmin alone (multiunit). They connect the thin filaments with other cell components and create dense bodies where they connect
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How is control of smooth muscle contraction different than others?
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The myosin is in a conformation such that its actin-binding site is masked by light meromyosin portion. It has to be phosphorylated by myosin light chain kinase to unfold the chain so actin can bind
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What stimulates the release of neurotransmitters in the nerve terminal?
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Activation of voltage gated Ca channels. Elevated Ca in the cell stimulates release of neurotransmitters
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How do synaptic vessicles acquire neurotransmitters?
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They have specific membrane pumps that require a proton gradient to function. They transport the neurotransmitters into the vessicles.
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What does ionotropic mean?
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It is a term to describe a neurotransmitter. It means it directly binds to and avtivates a ligand-gated channel (Na for Ach and Cl for GABA)
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What is the significance of temporal and spatial summation?
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It refers to the additive effect of excitatory or inhibitory impulses on a neuron either at the same time (temporal) or over the surface of a cell (spatial). This is necessary to generate an action potential
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What is the fate of neurotransmitters after release from pre-synaptic neuron?
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They bind and quickly dissociate and are broken down by enzymes and taken back into pre-synaptic neuron
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What does metabotropic mean?
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Refers to a type of neurotransmitter that binds to a G-protein linked receptor which act on ion channels. The effects are slower but longer lasting
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What determines the effect of a particular neurotransmitter in a given tissue?
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The type of receptor it is binding to. Ach for example can bind to nicotinic or muscarinic (G-protein) receptors
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What is the amino acid precursor of the biogenic amine neurotransmitters dopamine, epi, and norepi?
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Tyrosine--> L-dopa--> dopamine--> norepinephrine--> epinephrine (this is the pathway)
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How does L-dopa work to treat symptoms of Parkinson's disease?
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It crosses the blood brain barrier and is converted to dopamine by neurons that have aromatic amino acid decarboxylas (AAAD)
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What is the amino acid precursor of the biogenic amine neurotransmitter serotonin?
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tryptophan--> 5-hydroxytryptophan--> serotonin
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What enzyme is responsible for degredation of serotonin, dopamine, etc?
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Monoamine oxidase. Inhibitos of this enzyme are common anti-depression drugs. Also those that prevent reuptake by the presynaptic neuron (SSRI's)
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What is end plate potential?
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The depolarizing of the muscle fiber membrane due to neurotransmitter release from presynaptic neuron
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What effect does ATP binding have on the myosin head?
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It causes the myosin head to release from the actin chain
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What effect does cleavage of ATP have on the myosin head?
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It changes the conformation and basically "cocks the spring" to prepare it for the power stroke.
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What is troponins effect on tropomyosin?
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When Ca binds to it, it causes a positional shift deeper into the helix groove unmasking the myosin binding site on actin chain
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How does the body increase the force of muscle contraction?
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By progressively recruiting more and more motor units. There is not graded contraction in individual fibers though, its all or none
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muscle spindle function
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they provide feedback about the changes in muscle length as well as the rate of alteration in muscle length
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Golgi tendon organs
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they monitor the tension as well as the rate at which the tension is being produced during movement
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Intrafusal fibers
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specialized muscle spindle fibers that are connected to stretch receptors that can detect muscle length.
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extrafusal fibers
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These are the fibers that make up the motor units that contract and develop tension
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What is a gamma fiber?
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Small motor fibers that activate contractile elements at the ends of intrafusal fibers. This places tension on the stretch receptor and increases their sensitivity
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Why is gamma fiber stimulation important in muscle contraction?
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It gives muscle the ability to respond to the load placed on it and continue to recruit motor units
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What function do Golgi tendon organs serve?
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Collection of stretch activated receptors that stimulate inhibitory interneurons and reduce muscle tension while stimulating the opposing muscles.
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Large motor units
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Large, fast conducting, glycolytic type II. Recruited only in forceful contractions
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Small motor units
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Small, slow conducting, oxidative type I. Recruited first, frequently activated during fine motor movement.
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Function of corticospinal fibers
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They generally innervate appendicular muscles, not axial/postural. They can innervate alpha motor neurons directly or interneurons or pattern generating circuits.
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What is hyperopia and how do you correct it?
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Farsightedness due to lense of the eye being too flat. Correct with a convex lense
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What is myopia and how do you correct it?
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Nearsightedness due to lense of the eye being too round. Correct with concave lense
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What is the typical lifespan of an olfactory receptor cell and how are they replaced?
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30-60 day life span. They are replaced by basal cells
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roll of odorant binding proteins
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they carry inhaled odorant molecules through the mucus layer to the receptors on the cilia of the receptor cells
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Odorant receptors
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G-protein linked receptors, activation opens ion channels. There are 500-1000 different receptors and only 12 odor qualities.
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what are olfactory glomeruli?
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This is the point in the olfactory bulb where axons from similar odorant receptors all meet and connect to mitral and tufted cells (2nd order afferents)
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Function of periglomerular and granular cells?
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They are fibers from the olfactory cortex that inhibit sensory input and allow the brain to detect changes in odor (essentially resets the receptor)
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Taste buds
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A cluster of 50-150 chemoreceptor cells embedded in the lingual epithelium and connected with primary afferent nerve fibers
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Fungiform papillae
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2-4 taste buds per papillae. These are found on the top anterior 2/3 of the tongue
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Foliate papillae
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2-9 taste buds per papillae. These are found on the lateral borders of the tongue
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circumvalate papillae
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many taste buds in each one, they are located behind the gustatory V
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Von Ebner's glands
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secrete a purely serous saliva into the trough of the circumvalate papillae to help with dissolve tastants
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Mechanism of sour and salty taste
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Tastant molecule has direct ection on the ion channel in the apical membrane of taste cells. This is mostly fungiform
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Mechanism of sweet and bitter taste
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Signal is transduced via G-protein linked receptors (gustducin and transducin). This is mostly in folate and circumvalate
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What class of receptors are nociceptors?
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They are chemoreceptors, like taste and olfactory cells. They are activated by molecules that are a result of tissue damage
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2 main types of pain fibers
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Type A-delta are the most common and are small and myelinated (fast pain fibers).
Type C are unmyelinated and are slow pain fibers. |
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Gate-control theory of pain
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inhibitory interneurons between nociceptive fibers and 2nd order fibers. Pain signals inhibit the inhibiting interneuron and allow signal to pass to brain
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Neurotransmitter released by nociceptor nerve terminal
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Substance P stimulates 2nd order neurons to transmit pain signal
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Neurotransmitter released by pain inhibiting interneurons (endogenous analgesia)
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Opiod peptide called enkephalin. Might block the nociceptor or the 2nd order neuron, don't know for sure which
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What are the sites of opiod action?
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Dorsal horn synapse, rostroventral medial medulla (RVM) and periaqueductal grey (PAG)
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Where are the greatest amount of nociceptive fibers in the tooth?
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In the crown
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What causes depolarization of nociceptors?
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Damaged cells release proteolytic enzymes, K+, H+ (called inflammatory soup) that depolarize nociceptors.
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What is bradykinin?
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The proteolytic enzymes released by damaged cells cleave a short peptide from a circulating blood protein. This sensitizes free nerve endings
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Local tissue effects of substance-P
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Causes local inflammation and increase in permeability of capillaries
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primary hyperalgesia
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When an area becomes sensitized by injury so nociceptors fire easier and more frequently in response to the same stimulus.
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secondary hyperalgesia
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Skin surrounding area of injury becomes more sensitive to pain stimulus
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Allodynia
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When a normally innocuous stimulus evokes pain
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Role of prostaglandin-E2 in pain
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it is a product of cell damage and can activate mast cells. Contributes to secondary hyperalgesia
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What is a TRP channel?
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Ion channels found on polymodal neurons that respond to temp and chemical stimuli
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Vanilloid (TRPV) channel
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Respond to heat and also capsaicins. This is why peppers feel hot
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Menthol (TRPM) channels
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Stimulated by cold and also by menthol. This is why menthol feels cold
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What neurotransmitter do sympathetic postganglionic cells secrete?
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Norepinephrine, except in the adrenal medulla where they secrete epinephrine
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Common term for epi and norepi receptors
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adrenergic receptors
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function of alpha-2 adrenergic receptors
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noriepi binds to these receptors in the presynaptic cell and inhibits synthesis and release (feedback)
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function of alpha-1 adrenergic receptors
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found on vascular smooth muscle, functions to increase blood pressure by contracting vessels. Gq protein (IP3)
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function of beta-1 receptors
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Stimulation of heart rate and force via Gs protein (cAMP)
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function of beta-2 receptors
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causes smooth muslce in bronchi and uterus to relax, blood pressure to drop. Less bronchial constriction
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What is the major difference between artery and vein structure?
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Veins have bundles of longitudinally arranged smooth muscle in the adventitia...arteries only have CT. Arteries have much thicker muscular tunica media
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Epithelial reticular cells types 1-3
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they contain granules with thymic hormones for T cell maturation. They also encapsulate and seal off the cortex from the medulla
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Tingible body macrophages
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they are thymic macrophages that phagocytize the T cells that apoptose in the cortex
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Epithelial reticular cells types 4-6
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associated with the medulla, type 6 forms Hassal's corpuscles
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spleen red pulp function
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encompasses most of the splenic tissue. It is involved in degredation of senescent RBC's
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Spleen white pulp
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Scattered throughout the red pulp. Organized into T call and B cell rich regions. This is where antigen presentation takes place and B cell activation
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differences between MALT and other secondary lymphoid tissue
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MALT isnt encapsulated like the spleen or lymph nodes and IgA is the primary antibody
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