10478568
Description
Flashcards by Brianne Schmiegelow, updated more than 1 year ago
|
Created by Brianne Schmiegelow
about 7 years ago
|
|
| Question | Answer |
| What is Nissl substance? | Rough endoplasmic reticulum in somas of neurons |
| What pigments are found in neuron cell bodies? | Melanin and lipofuscin |
| Fast vs. slow axonal transport | Both movement of products down axon Slow: carries cytoskeletal elements Fast: carries membrane-bound organelles |
| Anterograde vs Retrograde axonal transport | Anterograde: from cell body down axon; uses KINESIN Retrograde: from axon to cell body; uses DYNEIN; less common! |
| Types of neurons | Multi-polar: most common; several dendrites; e.g. motor neurons and interneurons Bipolar: single dendrite opposite axon; e.g. receptor neurons of retina Unipolar: no dendrites on soma, axon only; e.g. sensory neurons Pseudounipolar: single dendrite and axon fuse with soma off to one side; e.g. dorsal root ganglia |
| Process of nervous conduction | 1. Na+ and Cl- higher OUTSIDE cell and K+ higher INSIDE cell due to Na-K pump and K channels in membrane (-80 mV resting potential) 2. Afferent stimulus causes region of plasma membrane in cell body to depolarize 3. V-gated Na channels open and Na rushes into the cell 4. V-gated K channels open and K leaks out of cell to cause reversal of resting potential (zero or slightly +) 5. Na channels close and are stuck there to cause refractory period (absolute at first, then relative) 6. K channels close and membrane repolarizes 7. Wave of depolarization travels down axon to synapse where neurotransmitter released |
| Which neurotransmitters are used in the PNS? | acetylcholine: parasympathetic norepinephrine (adrenaline): sympathetic |
| What prevents continuous stimulation of nerve receptors? | Vesicles on post-synaptic membrane contain hydrolytic and oxidative enzymes (e.g. acetylcholinesterase, MAO) which inactivate the neurotransmitters |
| What are Schwann cells and peripheral nerves derived from? | Neural crest |
| What do blood vessels in neurons tend to follow? | Epineurium and perineurium |
| What nerves are enveloped in Schwann cells? | ALL nerves in the PNS Non-myelinated: several in channels within Schwann cell surrounded by single layer of neurilemma Myelinated: nerve insulated by many layers of neurilemma to form myelin sheath from Schwann cell |
| What are nodes of Ranvier? | Gaps in myelin sheath between adjacent Schwann cells Responsible for rapid saltatory conduction Only place depolarization occurs in myelinated PNS nerves! |
| What are oligodendrocytes? | Type of neuroglial cell Cells in the CNS that myelinate nerves to increase conduction rate (although this also depends on diameter of the axon) |
| What are satellite cells? | Cells derived from neural crest that provide structural and metabolic support |
| Meninges | Composed of specialized epithelial cells (meningothelial cells) Supported by connective tissue Have protective function Confined to outer layer of the brain and cord in CNS |
| What are the layers of meninges? | Dura mater: outermost thick layer of dense CT internally lined by mesothelium; in cranium, fuses with periosteum of skull; in spinal cord, surrounded by epidural space Subdural space: separates dura from arachnoid mater Arachnoid mater: Subarachnoid space: separates arachnoid from pia mater; lined by flattened mesothelial cells; contains CSF and is continuous with ventricles of the brain Pia mater: adherent to surface of brain and cord; highly vascular |
| What is CSF? | Cerebrospinal fluid Secreted by cuboidal/columnar epithelium in choroid plexus (vascular structure arising from walls of ventricle in brain) Acts as shock absorber in CNS |
| What are the leptomeninges? | Pia mater and arachnoid mater |
| What are denticulate ligaments? | Ligaments that support the spinal cord Extend from the pia and anchor the cord to the arachnoid, dura, and periosteum |
| What are CNS neurons derived from? | Neuroectodermal cells of neural tube |
| What does gray matter contain? | Neuron cell bodies, dendrites, and axons |
| What does white matter contain? | Mostly myelinated axons |
| Neuroglial cells | Support cells in CNS Highly-branched and provide structural and metabolic support for neurons Includes oligodendrocytes, astrocytes, microglia, ependymal cells |
| What are astrocytes? | Type of neuroglial cell Most highly branches and largest of neuroglial cells Provide structural and metabolic support; aid in tissue repair following injury |
| What are microglia? | Type of neuroglial cell Phagocytic, fixed-tissue macrophage Smallest neuroglial cells; originally mesodermal, have immune function |
| What are ependymal cells? | Type of neuroglial cell Cuboidal epithelium lining ventricles and central canal of spinal cord Frequently ciliated |
| What is the cerebrum? | AKA cortex 90% is neocortex (includes sensory, motor, and association areas) Organized into folds called gyri |
| What are nuclei in the brain? | Clusters of neuron cell bodies formed in small islands of gray matter in the cerebrum and cerebellum |
| What are tracts? | Grouped bundles of axons leading in and out of gray matter in the cerebrum |
| What are pyramidal cells? | Pyramid-shaped neurons with long, slender axons found in cortex Includes Betz cells (upper motor neurons in motor cortex |
| What are stellate (granule) cells? | Small star-shaped neurons in cortex with short axons and dendrites |
| What are Cells of Martinotti? | Small neurons in cortex with long, horizontal axons |
| What are fusiform cells? | Vertically-oriented, spindle-shaped neurons in cortex with vertical axons |
| What are horizontal cells of Cajal? | Horizontally-oriented, spindle-shaped cortical neurons with horizontal axons Least common type of neuron, found only in the superficial layer |
| Layers of neocortex | I (plexiform layer): most superficial layer; contains mostly dendrites and axons of cortical neurons II (outer granular layer): contains large numbers of small pyramidal and stellate cells III (pyramidal cell layer): larger cells located deeper in layer; Martinotti cells also present IV (inner granular layer): densely packed stellate cells V (ganglionic layer): contains large pyramidal cells, stellate cells, and cells of Martinotti VI (multiform cell layer): contains small pyramidal cells, cells of Martinotti, stellate cells, and fusiform cells |
| What is the cerebellum? | Part of the brain that coordinates muscular activity, posture, and equilibrium Organized into folds called folia Central medulla of white matter contains mostly oligodendrocytes and myelinated axons |
| Two layers of outer cerebellar cortex | Outer molecular layer: contains few neurons and lots of unmyelinated axons Inner granular layer: very basophilic; contains lots of neuroglial cells and small neurons (granule cells) Separated by single layer of Purkinje cells which are specialized neurons which function in coordination and equilibrium |
| What is found in the central canal of the spinal cord? | Lined by ependymal cells and full of CSF Continuous with ventricles of brain |
| What is found in dorsal and ventral horns of the spinal cord? | Dorsal: afferent (sensory) nerve tracts Ventral: efferent (motor) nerve cell bodies |
| What is found in the white matter of the spinal cord? | Ascending and descending fiber tracts (columns) Mostly myelinated axons carrying sensory and motor data |
| Regeneration of an axon | 1. IF gap is not too big, Schwann cells multiply to physically bridge gap 2. Nerve axon sprouts neurites from proximal stump 3. Neurites grow into distal stump and contact reestablishes function May take weeks to months! |
| What is anterograde (Wallerian) degeneration? | If the portion of an axon distal to a point of injury degenerates due to the interruption of axonal transport ONLY in PNS Cell body also swells, becomes brightly eosinophilic, and loses Nissl substance (chromatolysis) if severe, results in retrograde degeneration and death of cell body |
| What happens in CNS injury? | Neuroglial cells multiply and the scar tissue proliferation prevents regeneration (physically blocks contact b/w cell body and axon) Neurons terminally differentiated (Go) and are unable to be replaced |
| What is meningitis? | Inflammation of the meninges May be bacterial or viral Viral generally causes transient lymphocytic infiltrate Bacterial generally causes neutrophilic infiltrate and may be life-threatening |
| What is encephalitis? | Inflammation of the brain |
| What is myelitis? | Inflammation of the spinal cord |
| What is poliomyelitis? | Disease caused by poliovirus that affects alpha-motor neurons of the ventral horn of spinal cord Causes lower motor neuron paralysis and subsequent muscle atrophy Eradicated by Salk vaccine |
| What is Parkinson's disease? | Neurodegenerative disease characterized by muscular tremor due to death of neurons in substantia nigra Decreases production of dopamine in the brain Treatment with L-dopa (dopamine precursor) |
| What is Alzheimer's disease? | Form of dementia characterized by neural plaques and fibrillary tangles within the cortex |
| What is multiple sclerosis? | Autoimmune, inflammatory, demyelinating disease of CNS Antibodies destroy myelin sheaths around the axons forming plaques Usually affects women between ages of 20-40 yrs old Symptoms vary with location of affected neurons and degree of demyelination Often multiple episodes with partial resolution in between |
| What is Guillain-Barre syndrome? | immune-mediated demyelination in the PNS often initiated by infection and leads to progressive weakness in peripheral muscles |
| How much of body mass is composed of skeletal muscle? | ~40% |
| How are muscles derived? | Mesodermally |
| How big are individual skeletal muscle fibers? | 80-100 micron diameter and up to 35 cm (1 ft) long |
| Skeletal muscle cell characteristics | Multinucleate Form syncytia due to fusion of myoblasts into myotube during development Myotubes synthesize contractile proteins which assemble into sarcomeres Nuclei are on periphery of cell and cannot proliferate |
| What do blood vessels and nerves in skeletal muscle follow? | Perimysium and epimesium |
| Fast twitch vs. slow twitch skeletal muscle | Slow-twitch: have "slow myosin; small fibers with lots of myoglobin; use aerobic respiration; LOTS of mitochondria; resistant to fatigue but only moderate tension; common in peripheral limbs Fast-twitch: have "fast" myosin; large fibers with less myoglobin and fewer mitochondria; use anaerobic glycolysis; have abundant glycogen and extensive SR for rapid Ca release; fatigue rapidly but high tension |
| What is rhabdomyolysis? | Condition caused by extreme exertion due to the breakdown of Type I muscle fibers and release of myoglobin |
| How is glycogen metabolized during peak periods of exertion? | In both Type I and Type II skeletal muscle fibers, via anaerobic glycolysis Produce ATP with lactic acid precipitating as crystals in muscle |
| Why do skeletal muscle cells increase in size with exercise? | Due to splitting/branching of individual muscle fibers, increase in mitochondria, and increase in volume of contractile proteins Production of new fibers is RARE |
| How do skeletal muscles regenerate after injury? | Primarily due to satellite cells (small myogenic cells adjacent to sarcolemma) Proliferate following injury and differentiate into myoblasts |
| What are mechanoreceptors? | Modified skeletal muscle fibers (intrafusal fibers) associated with modified nerve endings Two types Neuromuscular spindles: within belly of muscle; sensitive to changes in LENGTH Neurotendinous spindles (Golgi tendon organs): located within tendon; sensitive to changes in TENSION Both prevent overstretching and tearing of muscle; used in postural reflexes and coordination |
| Two types of myofilaments | Actin: "thin filament"; 6-8 nm diameter Myosin: "thick filament"; 15 nm diameter |
| Organization of muscle fibers | Myofilaments (contractile proteins) --> myofibrils --> individual muscle fibers |
| What causes striated appearance in skeletal muscle? | Parallel arrangement of contractile proteins Actin and myosin present in 2:1 ratio Overlap in A band but NOT in I band => striations |
| What are Z-discs? | Areas of sarcomere that act as anchoring points for actin myofilaments |
| What is the difference between a motor end plate and a terminal bouton? | Motor end plate is the same except it is MYELINATED |
| What is a T-tubule? | Extensive network of tubules continuous with sarcolemma in skeletal muscle Indirectly links the ECS with the ER and intracellular environment Ends are bounded by enlarged terminal cisternae of the ER on either side to form a triad |
| Sliding filament mechanism | 1. Influx of Na+ into cytoplasm (from stimuli) from t-tubules triggers depolarization of sarcolemma 2. Ca2+ is released from SR and terminal cisternae reservoirs into cytoplasm 3. Ca causes conformational change in troponin which interacts with tropomyosin molecules, exposing myosin-binding site on actin filament 4. Binding causes conformational change in myosin head and sliding of myosin past actin 5. Myosin heads repeat this in presence of Ca and Pi, causing contraction |
| What is a motor unit? | Group of muscle fibers supplied by a single motor neuron |
| What is recruitment? | Increase in number of motor units firing within a skeletal muscle |
| What is myasthenia gravis? | Autoimmune disease caused by production of antibodies to acetylcholine receptors Causes muscle weakness Treated with acetylcholinesterase inhibitors |
| What is muscular dystrophy? | Degenerative wasting disease that causes muscle weakness Due to genetic defect in muscle protein (i.e. dystrophin) that leads to cell death |
| What is inherent contractility? | Characteristic of smooth muscle Rhythmic, wave-like contractions independent of neurological stimulation |
| How many nuclei do smooth muscle cells have? | ONE |
| What is the ratio of actin and myosin filaments in smooth muscle? | 15:1 ratio Randomly arranged! |
| What are dense bodies? | Intracytoplasmic structures in smooth muscle that provide attachment sites for actin Functionally equiv. to Z-discs |
| What is calmodulin? | In smooth muscle, binds Ca and activates myosin cross-binding Used instead of troponin complex in skeletal |
| What are caveolae? | Buddings of membrane in smooth muscle that takes place of t-tubule system and terminal cisternae in skeletal Relies on diffusion of extracellular Ca for contraction |
| Types of smooth muscle | Single unit (tonic): fibers contract as a unit; most common; e.g. visceral SM of the gut Multi unit (phasic): individual fibers contract independently; e.g. erector pili and ciliary body of iris |
| Where do smooth muscle cells develop from? | Endothelial cells, pericytes of blood vessels, and fibroblasts Retain ability to divide and repair themselves |
| What kind of cells make up the pericardium? | Mesothelial cells |
| Epicardium | Outermost layer of heart Simple squamous mesothelium on external surface of the heart Supported by underlying fibroblastic CT and adipose tissue Blood vessels and neurons located within subepicardial layer |
| Myocardium | Cardiac muscle itself; thicker in ventricles than atria Thick, collagenous, CT skeleton composed of fibroblasts and collagen Cardiac muscle intermediate between skeletal and smooth muscle both structurally and functionally |
| Endocardium | Layer of heart that lines atria and ventricles as well as covers heart valves Simple squamous endothelium Supported by subendothelial fibroblastic CT interspersed with reticular fibers and smooth muscle Thicker in atria than ventricles Purkinje fibers located within subepi and endocardial layers |
| Structure of cardiac muscle | Cardiac myocytes contain intracellular diad composed of one T-tubule and one cisterna of ER located at Z-disc |
| Cardiac valves | Valves that contain a layer of fibrous CT (lamina fibrosa) covered by endothelium Surrounded by tough, fibrous rings at base of aorta and pulmonary arteries, AV valves Occasionally ossify to form bony rings at base of AV valves (os cordis) |
| What are intercalated discs? | Places where cardiac fibers end Enhance spread of contractile stimulus between cells and allow synchronous contractions Also provide increased surface area for attachment of myofibrils between adjacent cells Made up of cell junctions -Desmosomes: bind individual myocytes together laterally and on ends -Fascia adherens: join ends of fibers -Gap junctions: located laterally and provide ionic comm between cells, synchronize contractions, and allow syncitium behavior |
| What makes up the conduction system of the heart? | SA node, AV node, Bundle of His, and Purkinje fibers All consist of highly modified myocytes that are joined by extensive gap junctions and coordinate conduction Cells are larger and conduct impulses 4x faster |
| Why are conduction system cells paler-staining than the surrounding muscle? | High glycogen content |
| What is the process of cardiac conduction? | 1. SA node: "Pacemaker" located at junction of superior vena cava and right atrium generates impulses that induce contraction of atria 2. As impulses spread, stimulates AV node located between right atrium and right ventricle 3. AV node delays impulse and gives atria time to contract 4. Impulse travels down IVS via bundle of His and branches into left and right AV bundles to initiate ventricular contraction 5. Fibers further subdivide in ventricular myocardium into Purkinje fibers within subendocardium and subepicardium of ventricular wall then gradually merge with myocardium |
| What modulates the inherent rhythm of the SA node? | Autonomic nervous system Sympathetic stimulation from sympathetic ganglia increases HR Parasympathetic stimulation from vagus nerve decreases HR |
Want to create your own Flashcards for free with GoConqr? Learn more.