MMED physio block Flashcards
DESCRIBE Kidneys
Filter. Reabsorb and Secrete. in the outer renal cortex and the inner renal medulla.
renal pelvis is waste.
DESCRIBE The structure of nephron
The juxtaglomerular apparatus is the intersection between the distal tubule and afferent and efferent arteries.
Renal artery runs with oxygenated blood from the heart. Renal vein runs with deoxygenated blood towards heart.
Nephrons follows the glomerular’ filtrate to bowman’s capsule through proximal tubule down and up loop of henle through distal tubule, out collecting tubule. Blood cells and large plasma proteins are not filtered
DESCRIBE glomerulus structure
Podocytes are cells that form around the outside of glomerulus, form slips, prevent large proteins passing. Inner membrane of glomerulus is the basement membrane which filters.
The filtrate needs to go from the cortex in the bowmans, to the medulla because of the higher osmoregularity.
DESCRIBE Reabsorption from the filtrate through barriers
Substance must pass through 5 barriers:
Luminal cell membrane, cytosol, basolateral membrane, interstitial fluid, peritubular capillary.
DESCRIBE Restriction of glomerular filtration
occurs through vasoconstriction of the afferent arteriole lowering the glomerular capillary and net filtration pressure, lowering GFR. this is caused by increased sympathetic nerve stimulation.
DESCRIBE Renin
enzyme and hormone which forms angiotensin 1 from angiotensinogen, which is converted into angiotensin 2 in the lungs, then stimulates adrenal cortex to produce aldosterone that stimulates kidney to reabsorb Na+ through tubules, as well as Cl-.
angiotensin 2 also stimulates vasoconstriction, increases thirst and stimulates release of vasopressin which increases water reabsorption.
Renin is secreted by kidneys due to reduces NaCl, ECF volume and arterial blood pressure directly into blood.
DESCRIBE Vasopressin
(ADH) controls water output acting in distal tubule and collecting duct causing them to become permeable to water through formation of more aquaporins. Normally is non-permeable to water without vasopressin.
DESCRIBE pupil, iris and conjunctive
Pupil - black centre
Iris - coloured tissue. Acting diaphragm, varying sizes. Has sphincter and radial muscle. Pigmented epithelium
Conjunctive - thin membrane provides blood to sclera and inner surface of eyelid, also protection.
DESCRIBE Sclera, cornea and ciliary body
Sclera - white membrane. Dense in collagen fibers, gives shape.
Cornea - clear section above iris and pupil. Allows light through, epithelium, stroma, endothelium.
Ciliary body - behind iris. extends suspensory ligaments to hold lense in place, produces aqueous humor, has ciliary muscles.
DESCRIBE Lens, fovea and retina
Lense - behind iris and pupil, convex and elastic.
Retina - innermost layer of back eye, has photoreceptors. Made of pigmented epithelium and multilayer neural retina.
Has cones and rods as photoreceptors. Macula in central retinal has mostly cones, peripheral retina have rods.
Fovea - a small pit in macula with only cones for detailed colour vision.
DESCRIBE posterior and anterior chamber of eye
Between cornea and lense is a chamber (posterior and anterior) filled with aqueous humor, which is drained into venous blood via canal of schlemm, Also diffused through viterous humor in posterior.
Provides nourishment in cornea and lens
DESCRIBE Controlling light distance with eye
Distant vision: Min convergence Pupils dilated Ciliary muscles relaxed Suspensory ligaments stretched Lens flattened(narrow) Light focused on retina
Near vision:
Convergence through muscles.
Pupils constricted
Ciliary muscles constricted
Suspensory ligaments relaxes
Lens concaves(bulges) focusing light on retina.
Presbyopia is the hardening of the lense, where it loses its elasticity
Pupillary reflex is mediated by parasympathetic fibers of oculomotor nerve.
DESCRIBE Shape of lense control.
Near accommodation - contraction of ciliary muscles, move ciliary processcesses close to lense that reduce elastic tension in suspensory ligaments and lense capsule result in concave shape.
Far accomodation - relaxation of ciliary muscles result in convex shape
Tensile forces from choroid and sclera contribute to cilary muscles
DESCRIBE Entry of light into eye
Enters into cornea then the lense. Entry through cornea and lense bends light twice, once more leaving lens.
DESCRIBE Movement of eyes:
2 oblique, Superior and inferior muscles
4 rectus muscles, medial, lateral, inferior, superior.
DESCRIBE Cellular organisation of retina: outside to inside:
Pigmented layer, Rod and Cone, horizontal cells, bipolar cells, amacrine cells, ganglion cells.
Axons of ganglion cells form optic nerve, leaving the eyeball at the optic disc, or blind spot.
DESCRIBE photoreception of dark and light
In dark, in membrane disks of photoreceptors. Opsin is bound to 11-cis retinal, inactive, cGMP-gated Na+ channels are open, membrane is hypopolarised (no polar), inhibitory neurotransmitter glutamate is released
In light, in membrane disks of photoreceptors. 11-cis retinal is converted to all-trans retinal and released activating opsin and thus transductin and cGMP hydrolysing enzyme, cGMP Hydrolyses, resulting in closure of Na+ channels. Membrane is hyperpolarised (polar) reducing release of inhibitory neurotransmitter.
DESCRIBE AP travel for optics
Action potentials travel to brain through Lateral Geniculate Nucleus in thalamus via optic nerve, optic tract and optic radiation, there is an LGN on both sides of brain.
DESCRIBE Visual fields
Left visual field, light coming from left, hitting right side of retina, right visual field is opposite. The optic path for each travel to the opposite hemisphere of the brain to its name. Left field travels to right hemisphere LGN, each LGN receives one whole visual field.
Nasal light hits retinal close to nose and Temporal light hits retina close to temple. The axons of ganglion cells from nasal retina decussate whereas axons from temporal region do not decussate.
DESCRIBE where different signals from eyes go to in the Lateral Geniculate Nucleus.
Visual signals from fovea go through parvocellular (small neurons, 4 layers) pathway for colour and detail whereas parafovea and peripheral retina go through magnocellular (large neurons, 2 layers) pathway about form, movement, depth and brightness.
DESCRIBE Functions of the gut:
Motility, propulsion/mixing
Secretion, mucous/acid/enzymes
Blood flow, increases during secretion and absorption
Digestion, secretion and motility work together. (no controlled movement)
Absorption, food getting through body through blood. (little controlled movement)
DESCRIBE The enteric nervous system
all nerve cells within the wall of the gut controlling gut functions. The submucous plexus and myenteric plexus.
DESCRIBE Layer of enterocytes in gut
Microvilli on epithelial cells have pumps. The enterocyte cells are connected through tight junctions, impermeable, and desmosomes and gap junctions, communication.
Epithelial cells are metabolically active, able to flatten and migrate to damaged tissue. Require strong blood supply. Special goblec cells secrete mucous.
Pumps let sodium into cells along with amino acids or glucose, pumps on the other end of the cells allow it to travel through the blood.
DESCRIBE Pancreatic function
Exocrine (digestive) secretions
Lipase -breaks down fat to monoglycerides + fatty acids
– Amylase - breaks down starches to disaccharides
– The pancreatic duct cells also secrete large quantities of HCO3
-
-rich
solution that neutralises gastric acid (stimulated by secretin from the
duodenum)
