F214

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.

Movements of ions along a neurone. Flow of ions caused by increase in concentration at one point, which causes diffusion where the ions diffuse away from the region of higher concentration.

Local Currents

Myelin Sheath

Insulating layer of fatty materials made from Schwann cells. Gaps between called nodes of Ranvier, these cause the local currents to elongate so Na+ diffuse from one to the next. This means the action potential appears to jump from one node to another. Saltatory conduction.Advantages of this are that action potentials can only occur at nodes or Ranvier speeding up transmission of action potential.

Nerve Junctions

Synaptic 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

Acetylcholinesterase

Enzyme found in synaptic cleft. It hydrolyses acetylcholine to ethanoic acid and choline. This stops transmissions so action potentials aren’t continued.

Endocrine System

Endocrine Gland- secretes hormones directly into the blood, has no ducts.Exocrine Gland- secretes molecules into a duct that carries molecules 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 the pancreas 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

Excretion

Excretion- The removal of metabolic waste from the body.Carbonic Acid Dissociation:H₂0₃ → H⁺ + HCO ₃⁻Deamination:Amino Acid + Oxygen → Keto Acid + AmmoniaFormation Of Urea:2NH₃ + CO₂ → CO(NH ₂) ₂ + H₂O

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 Cells

Are specialised macrophages, they move in sinusoids and breakdown/recycle. Bilirubin is a breakdown of the RBC and is excreted as part of bile. Bilirubin causes the brown pigment in faeces.

Ornithine Cycle

Ammonia+ Carbon Dioxide → Urea +Water

Detoxification

Detoxyfication of Alcohol

Ethanol→Ethanal → Ethanoic Acid →Acetyl CoA (Goes To Respiration)

2H removed from Ethanal & Ethanoic Acid by NADNAD + 2H → Reduced NAD

The Kidney

Kidney Fluid Composition

PCT- fluid altered by reabsorption of all sugars, salts and some water. 85% of fluid reabsorbed here.D LoH- Ѱ decreased by addition of salts & removal of waterA LoH- Ѱ increased as salts removed by active transportCD- Ѱ decreased by removal of water, ensures urine has low Ѱ . Meaning urine has higher conc. of solutes than in blood and tissue fluid.

UltrafiltrationBlood flows into glomerulus form afferent arteriole.This is wider the efferent arteriole. This difference ensures pressure is higher in glomerulus than the Bowman’s capsule, pushing fluid from the blood into Bowman’s capsule. Basement membrane stops bloods cells and proteins passing through. Podocytes allow fluid to travel between them into Bowman’s capsule.

Filtered Out of BloodWaterAmino AcidsGlucoseUreaInorganic Ions (salts)

Selective Reabsorption

Structure/Anatomy

Cell surface membrane highly folder Greater SACo-transporter proteins – facilitated diffusionHas mitochondria- ATP for active transportMembrane of cell by blood supply has Na-K pumps that pump Na out of cell and K in.

Selective Reabsorption

Sodium ions actively transported out of cell into tissue fluid via sodium/potassium pumps.Glucose or amino acids enter cells with Na+ by facilitated diffusion involving co-transporter proteins.Glucose and amino acids diffuse into blood capillary.Low water potential in cells due to reabsorption of salts/glucose means water enters cells and then blood by osmosis.

Water Reabsorption

D 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 capillaries

Urine 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 neurosecretory cells. These release ADH, which is in the hypothalamus which flows down the axon to the posterior pituitary gland and stays until needed.When Neurosecretory cells are stimulated it goes into blood capillaries around 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

Dialysis

Dialysis- use of a partially permeable membrane to filter blood. Dialysis fluid matches blood composition. Heamodialysis- blood taken from vein cleaned, herapin added to reduce clotting, and bubbles removed.

Pregnancy Testing

Hormone hCG released when pregnant. Pregnancy tests have monoclonal antibodies which is specific and will only bind to hCG. hCG binds and moves until it stiks to immobolised antibodies. As a result antibodies have blue bead and form a blue line. One blue line is a control. The second line confirms pregnancy.