Tissues-nerve and muscle Flashcards
Describe a rought anatomy of the 4 parts of the CNS.
1) cerebral hemisphere-or brain-surface of ridges. 4 functional regions-parietal, occipital, temporal and frontal
2) Brainstem-in descending order midbrain, pons and medulla-usually target or source of all cranial nerves. variety of functions
3) Cerebellum-hindbrain attached to brainstem-motor coordination, balance and posture
4) Spinal Cord-extends from medulla-conduit for neural transmission and important for PNS reflexes.
Describe the 4 main morphology of cells of the nervous system
Unipolar-cell body and one only projection coming out
Pseudo-unipolar-single projection that divides in 2 afterwards
Bipolar-two projection from the cell body
Multipolar-numerous projection that split afterwards
Describe neurons- morphology and role
Excitable cells of the CNS-heterogenous morphology
But common features-non dividing, Soma (cell body)-nucleus, machinery, neurofilaments and transport
Axon-Long process connected to soma by axon Hillock-can split into collaterals but only 1. Usually covered in myelin
Dendrites-highly branched cell body-not covered in myelin (recieves signals not send them)
Descibe Astrocytes - morphology and role
Most abundant cells of CNS-and can proliferate => structural cell siting outside, control what goes in and out the blood brain barrier, cell repair, Immune cells (facultative macrophages), Neurotransmitter release and uptake
Describe 2 myelin producing cells
Oligodendrocytes-found in CNS-vary in morphology/Function. But overall numerous projection that encircle cells and produces myelin-one cell can myelinate MANY neirons
Schwann cells-produce myelin for PNS-one cell per axon segment-sits on top
Describe Microglial and ependymal cells
Microglial-macrophages of CNS
Ependymal cells-Epithelial cells of CNS-line fluid filled ventricles=> regulate production and movement of cerebral fluid (CSF)
Describe resting membrane potential. What ions are in and out the cells? In what proportions? Literally what is the RMP?
4 major ions play a role-cell membranes are impermeable to them
High extracellular (vs intra)-Na+ and Cl-
Low extracellular (vs intra)-K+
High conc gradient (more in)-Ca2+
The difference in conc creates a potential -nernst equation–40 to -90mV at resting (negative charges inside rather then out
charges tend to focus around the membrane
Describe the process of action potential. what ions are involved? What changes? why? how? what happens after?
Na+ and K+ are main-normally Voltage gated Na+/K= channels (VGSC and VGKC) are closed
First step is electrical signal transmit through cell-opens up the channels-> influx of Na+ = membrane depolarisation makes cell go from -40 to +90mV.
VGKC also open, leading to efflux of K+-membrane repolarisation to balance-goes back down to -45/50mV
After this-complete balance but has to be reset - Na+/K= ATPase pumps 3Na out for 2K in, using 1 ATP-returns to resting configuration
What is Saltatory conduction? what is it role?
AP spreads along axon-but too slow
Myelin prevents AP from passing-high resistance and low capacitance-but doesnt cover the whole Axon => nodes of Ranvier are small gaps where most VGC are
AP jumps between the nodes and that goes faster
Unable to jump across axon terminal to next neuron
Describe the process of synaptic transmission
When excited, AP propagates along axon until it reaches synapse. There, VGCalciumC at the preterminal open-influx leads to exocytosis of neurotransmitter vesicles-NT released in gap and binds receptors, which create the AP for the next cell
NT finally dissociated from receptor and is either metabolised or recycled
MUSCLE MAN
RANDY SAVAGE
Describe Skeletal muscle function-explain isometric, isotonic. Describe structure as well. What are myofibers and myofibrils.
Describe quickly T-tubules and Sacroplasmic reticulum
Skeletal muscle is attached to the bone at each end and produces movement. Usually a pair of antagonist muscles (flexor and extensor)
Isotonic-muscle change length to keep tension the same (concentric-shorten-, eccentric (lenghtening)
Isometric-tension develops and muscle does NOT change length
Skeletal muscle is a bundle of large cells known as myofibrils-large and cyclindrical multinucleated and packed with myofibrils
Myofibrils-light and dark bands give a striated appearance, composed of sarcomeres (between 2 Z lines)
T-tubules are membrane invaginations at the edge of the fibrils-helps extend contact with ECF
SR-extensive Ca2+ stores surrounding each fibril
Describe excitation contraction coupling
AP potential from origin propagates along membrane and T-tubules. activates surface Dihydropyridine receptros (DHPR)-and this is transmitted to Ryanodine receptor (RyR) on SR which releases Ca2+ ->depolarisation increases intracellular Ca2+
Describe the sarcomere-be able to draw it
Describe the sliding filament theory
List of components-Z lines (lateral boundaries of sarcomeres), Actin (polymeric filaments going from both Z lines to center), Myosin and mysosin heads (sits in center between actin), titin (large spring like filament anchoring myosin to Z line), Nebulin (large filament bound to actin), Tropomysin (elongated prot bound to actin) CapZ and tropomodulin (associated with +Ve and -Ve ends of actin respectively)
For the movement-Ca2+ influx leads to troponin moving from tropomyson-actin and myosin heads can bind actin. Binding and discharge of ADP causes head to pivot-pulls actin/Zline inwards (tension). ATP binding releases head from actin, and hydrolysis pivots the head back to original position
Describe general heart and cardiac muscle background
heart muscle called cardiomysocytes, But other cells are important-pacemaker cells (sinoatrial node (small spontaneous active cells), Atrioventricular node (spindle shaped netword near right atrium)
Conduction fibres-bundle of his (conducting cells ajoining AV nodes and Purkinje fibre
Purkinje fibres- large cells that conduct the impulses
Cardiac muscle-walls of the heart (myocardium)-striated muscle
Cells are not fused like skeletal-intercalate disks join the up the cells with gap junctions to allow potential to spread
Sacromeres-contractile unit-virtually same as skeletal muscle
