Cellular Physiology

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  • Created by: Splodge97
  • Created on: 16-05-17 14:21
What is the composition of the reference man?
60% H2O (2/3 ICF, 1/3 ECF (25% plasma, 75% interstitial fluid)), 17% protein, 15% lipid, 5% minerals, 2% nucleic acid and 1% carbs
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What is the benefit of a molal solution?
1 L of water added to a mole (not made up to 1L) so can better resist temp change
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What is Fick's law?
Diffusion rate = conc grad x SA x permeability/membrane thickness
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What is the Gibbs Donnan effect?
Example when negative proteins in cells attract cations from the interstitial fluid and repel anions - as such ionic concentrations either side of membrane not equimolar
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What is hydrostatic pressure (generally)?
Pressure any fluid exerts in a confined space
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Why does hydrostatic pressure lessen?
As force exerted by heart reduces (so oncotic overtakes, causing net movement into capillaries (driving movement of venous plasma))
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Where do the lymphatics return excess fluid to the venous system?
Subclavian vein via thoracic duct
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What is osmolarity?
Conc. of osmotically active praticles (which diffuse across the membrane) per L of solution. Calculated by molarity x number osmotically active particles per molecule after dissociation.
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What is tonicity?
Comparative term to describe how a solution would affect cell volume (hypotonic causes lysis, hypertonic crenation)
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What are ineffective osmoles?
Particles which are permeable to the membrane, so become isosmotic across it after a time (as they are taken into account by osmolarity, eventually making it 0 for that particle. Not accounted for by tonicity (so doesn't always equate to osmolarity).
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What is bulk flow?
Fluid movement from a higher to a lower pressure
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Why is transport by channels faster than by carriers?
As carriers require ATP to bind to allow conformational shape change in active transport (channels allow facilitated diffusion, or dont require a shape change)
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Why does SDGT (SGLT-1) operate by secondary active transport?
Moves glucose/galactose into cell using gradient for Na+, but gradient for Na+ actively established by Na+/K+/ATPase
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What is membrane poteontial?
Potential inside a cell membrane relative to the fluid just outside it
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What limits the outward movement of K+ and the inward movement of Na+ at resting potential?
K+ outflow limited by negative intracellular proteins, Na+ influx limited by high intracellular cation concentration. At the point they stop movement they have reached their dynamic equilibrium.
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What are the E values (from Nernst equation) for Na+ and K+?
K+ = -97mV, Na+ = +61mV
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What is threshold potential? What does it cause?
-55mV, causes Na+ VGC's to open at their activation (m) gate
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Why is the refractory period greater in cardiac muscle?
Prevent palpitations, allows atria and ventricles to fully empty
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What is the transmission velocity in un-myelinated axons vs myelinated axons?
0.5m/s in un-myelinated, 70m/s in myelinated
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What is a receptor potential?
The graded potential caused by Na+ as a result of the stimulus; integrated in the axon hillock to see if AP generated (depolarisation sufficient). Has no minimum stimulus, as amplitude in proportion to it.
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Describe the actomyosin arrangement in smooth muscle
Long thin actin filaments in a matrix overlaid with short myosin filaments (dense bodies); works to contract whole cell at once
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What causes the power stroke?
Loss of Pi from myosin heads
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What is excitation contraction coupling?
Conversion of an electrical stimulus to a mechanical response (responsible for contraction delay, occurs after synaptic delay - diffusion across cleft - so represents time between transmission down t-tubules and start of sliding filament theory).
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What are the different types of tetanus (when AP's across muscles at their maximum)?
Unfused (allows individual contractions to be seen as muscle doesn't fully relax) and fused (one long maximal contraction so the twich is smaller than the tetanus but of longer duration)
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What is epithelium?
Cell type covering external surfaces and hollow lumens (except blood vessels/lymphatics lined with endothelium), derived from endoderm layer
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What are the different types os epithelia?
Simple (arranged in a single layer), stratified (arranged in multiple layers) or pseudostratified (layers which interlink), columnar (rectangular shaped), cuboidal (square shaped), squamous (long and flat)
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Give example of the different types of epithelia
Simple squamous in alveoli, keratinised squamous stratified on the skin, tongue, gingiva and palate (un-keratinised on oral mucosa), pseudostratified in trachea, simple columnar in the intestine, stratified cuboidal in sweat glands.
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How do tight junctions act to tightly adhere cells?
Claudin and occludin proteins ensure only small gaps exist between adjacent cell membranes
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Describe the appearance of gap junctions
Heterodimers (of connexin or innexin to form connexon/innexon channels) or pannexon channels (formed from 6 pannexin) interlink the cytoplasm of adjacent cells
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How are anchoring junctions held?
Desmosomes present between cells, contain linking cadherins proteins; allow slight movemnt, select substances can pass through
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What is the basal lamina?
Matrix upon which the base epithelial cells sit; comprised of type IV collagens, proteoglycans (attract H2O) and glycoproteins (lamin and enactin). Acts as molecular filter, supports/regenerates cells, may retain stem cells (later differentiate).
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What are exchange epithelia?
In lungs and CVS, rapid transport enabled by leaky junctions
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What are transporting epithelia?
Tight juctions allow selective transport of ions and nutrients (in kidney and intestines)
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What are exocrine tissues (a type of secretory epithelia)?
Occur in goblet cells of mucous glands, excrete directly to external environment via a duct; when signalled to become glandular tissue, cells divide down into underlying connective tissue to form a lumen.
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What are endocrine tissues (a type of secretory epithelia)?
Secrete proteins/hormoes directly into ECF/blood; when signalled to become glandular tissue cells divide down into conective tissue but then hollow structure formed detaches from the surface epithelial layer.
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What causes psoriasis (flaky skin)?
Overproduction of epithelial cells
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What is the fuction of the epidermis?
Formed by keratinocytes, not vascularised, nouished by the dermis - has barrier function, protects from abrasion.
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What is the stratum basale?
Bottom layer of epidermis - contains basal keratinocytes (regenerate epidermis and basal lamina), merkel cells and melanocytes
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What is the striatum spinosum?
Layer of epidermis above stratum basale, contains suprabasal keratinocytes (start to differentiate to keratin, appear spinous due to desmosomes between them) plus langerhans cells.
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What is the stratum granulosum?
Layer of epidermis above stratum spinosum - keratinocytes lose their nuclei and cytoplasm appears granular, releases lipids (especially is stratum lipidum to be formed)
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What is the stratum lipidum?
Layer of epidermis which may form above stratum granulosum in the palms and soles - it is translucent
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What is the stratum corneum?
Top layer of epidermis where keratinocytes have no nucleus/organelles and are surrounded by keratin, lipids and cross-linked proteins (form protective cornified envelope).
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What does the dermis contain?
Fibroblasts, collagen, elastic fibres, hair follicles, sweat glands, serbaceous glands, nerves and blood vessels
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What is the papillary dermis?
Upper layer of the dermis, entwines with epidermis via papillae. Contains loose collagen fibres, messiners corpuscles and langerhan's cells.
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What are langerhans cells?
Dendritic cells found in the striatum spinosum and papillary dermis - process microbial antigens and present to the immune system
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What is the reticular dermis?
Thick cell layer below the papillary dermis, contains dense network of collagen and elastic fibres to provide tensile strength. Also contains small blood vessels, serbacous glands (holocrine), sweat glands (merocrine) and pacinian corpuscles.
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What is the basal membrane?
Formed from the basal lamina and the reticular layer (produced by fibroblasts of the dermis)
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What does the hypodermis contain?
Adipose tissue (energy store/protective), large blood vessels, a few collagen fibres; insulates body heat
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What is the lamina propira?
Layer of conective tissue which replaces the dermis in oral mucosa - forms shorter and broader papillae to increase SA for nutrient exchange and restance to pressure
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How are layers of the oral mucosa different to in skin epithelia?
Stratum intermedium replaces stratum granulosum as cells don't lose nuclei), stratum intermedium replaces stratum corneum (as cells not keratinised - are alive and require nutrients). Para-keratinisation may occur with persistant biting.
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What is the benefit of a molal solution?

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1 L of water added to a mole (not made up to 1L) so can better resist temp change

Card 3

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What is Fick's law?

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Card 4

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What is the Gibbs Donnan effect?

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Card 5

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What is hydrostatic pressure (generally)?

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