Action Potential1. Resting state- Polarised -60mV > outside2. Sodium ion channels open & Na+ diffuse in3. Membrane depolarises and becomes -50mV > outside4. Voltage gated Na+ channels open, more ions enter, cell becomes positively charged5. P.D reaches +40mV6. Sodium channels close & potassium channels open7. Potassium ions diffuse out, P.D become –ve and cell repolarises8. P.D overshoots become hyperpolarised9. Original P.D restored so cell returns to resting state.
Local CurrentsMovements of ions along a neurone. Flow ofions caused by increase in concentration at onepoint, which causes diffusion where the ionsdiffuse away from the region of higherconcentration.
Myelin SheathInsulating layer of fatty materials made fromSchwann cells. Gaps between called nodes ofRanvier, these cause the local currents toelongate so Na+ diffuse from one to the next.This means the action potential appears to jumpfrom one node to another. Saltatory conduction.Advantages of this are that action potentials canonly occur at nodes or Ranvier speeding uptransmission of action potential.
Nerve JunctionsSynaptic Knob has:• Many mitochondria indicating processing needing ATP occurs• Large amoung of smooth ER• Vesicles of acetylcholine• Voltage-gated calcium ion channels
Transmission across synapse• Action potential arrives at knob.• Voltage gated Ca+ channels open and Ca+ diffuses in• Ca+ causes synaptic vesicles to move and fuse with presynaptic membrane• Acetylcholine is released by exocytosis & diffuse across cleft• Acetylcholine bind to receptor sites on Na+ channels in postsynaptic membrane & Na+ channels open• Na+ diffuse across postS membrane into the postS neurone• Generator potential is created if this combined reaches sufficient levels then threshold potential is achieved• A new action potential is been created in the PostS neurone
AcetylcholinesteraseEnzyme found in synaptic cleft. It hydrolysesacetylcholine to ethanoic acid and choline. Thisstops transmissions so action potentials aren’tcontinued.
Endocrine SystemEndocrine Gland- secretes hormones directly into the blood, hasno ducts.Exocrine Gland- secretes molecules into a duct that carriesmolecules to where they’re needed.Adrenaline• Can’t enter cell therfore it binds to the first complementary receptor site.• Adrenaline activates the enzyme Adenyl Cyclase• Adenyl Cyclase converts ATP to cAMP which then activates enzymes within the cell.
Regulation of Blood GlucosePancreatic Duct- tube that collects all secretions from the exocrine cells in thepancreas and carries the fluid to the small intestine.Alpha Cells- Secrete hormone GlucagonBeta Cells- Secrete hormone InsulinGlycogen > Glucose (Glycogenolysis)Glucose > GlycogenType 1 Diabetes- insulin dependent, starts in childhood usuallyType 2 Diabetes- Non-insulin dependent
The LiverBlood from Aorta → Hepatic Artery → LiverDe-ox Blood from Hepatic Portal Vein → LiverBlood leaves via Hepatic VeinBile Duct secretes bile from Liver → Gall Bladder
Kupffer CellsAre specialised macrophages, they move insinusoids and breakdown/recycle. Bilirubin is abreakdown of the RBC and is excreted as part ofbile. Bilirubin causes the brown pigment infaeces.
Kidney Fluid CompositionPCT- fluid altered by reabsorption of all sugars, saltsand some water. 85% of fluid reabsorbed here.D LoH- Ѱ decreased by addition of salts & removal ofwaterA LoH- Ѱ increased as salts removed by active transportCD- Ѱ decreased by removal of water, ensures urine haslow Ѱ . Meaning urine has higher conc. of solutes thanin blood and tissue fluid.
UltrafiltrationBlood flows into glomerulus form afferent arteriole.This is wider the efferent arteriole. This difference ensures pressure is higherin glomerulus than the Bowman’s capsule, pushing fluid from the blood intoBowman’s capsule. Basement membrane stops bloods cells and proteinspassing through. Podocytes allow fluid to travel between them into Bowman’scapsule.Filtered Out of BloodWaterAmino AcidsGlucoseUreaInorganic Ions (salts)
Selective ReabsorptionStructure/AnatomyCell surface membrane highly folder Greater SACo-transporter proteins – facilitated diffusionHas mitochondria- ATP for active transportMembrane of cell by blood supply has Na-Kpumps that pump Na out of cell and K in.
Selective ReabsorptionSodium ions actively transported out of cell into tissuefluid via sodium/potassium pumps.Glucose or amino acids enter cells with Na+ byfacilitated diffusion involving co-transporter proteins.Glucose and amino acids diffuse into blood capillary.Low water potential in cells due to reabsorption ofsalts/glucose means water enters cells and then bloodby osmosis.
Water ReabsorptionD LoH- H₂O out Na+ & Cl- inA LoH- Na+ & Cl- out lower part Active removal of ion out higher partC D- H₂O out by osmosis & enters capillariesUrine passes down collective duct to pelvis.
OsmoregulationCollecting duct walls respond to ADH, increasing/ decreasing permeability.Vesicles with aquaporins embed in membrane to change permeability.Water potential of blood monitored by osmoreceptors in the hypothalamus.When water potential in blood is low, cells shrink, stimulating neurosecretorycells. These release ADH, which is in the hypothalamus which flows down theaxon to the posterior pituitary gland and stays until needed.When Neurosecretory cells are stimulated it goes into blood capillariesaround the PPG and Is transported to the collecting duct.Once potential of blood rises less ADH is released.More ADH= More permeabilityLess ADH= Less permeability
DialysisDialysis- use of a partially permeable membrane tofilter blood.Dialysis fluid matches blood composition.Heamodialysis- blood taken from vein cleaned, herapinadded to reduce clotting, and bubbles removed.
Pregnancy TestingHormone hCG released when pregnant.Pregnancy tests have monoclonal antibodieswhich is specific and will only bind to hCG. hCGbinds and moves until it stiks to immobolisedantibodies. As a result antibodies have bluebead and form a blue line. One blue line is acontrol. The second line confirms pregnancy.