Human Cell Biology and Physiology

1. Human Cell Biology and Physiology Timothy Billington PhD

2. HIDDEN IN A CLOUDLESS SKY

3. 6TH FORMATIVE • The liver regulates general metabolism and controls the composition of………………….? • Name two types of biochemical substances that a hepatocyte can store • What two functions are known for Kuppfer cells? • Parietal cells in the stomach produce hydrochloric acid. What functions does this acid perform? • Which structures line the internal surface of the small intestine? • Where in the body is the beginning of the digestion of carbohydrates? • Which two enzymes can produce monosaccharides from longer saccharides? • Meat in the diet provides protein. Which enzymatic processes produce amino acids? • Name the vessel that brings blood to the liver directly from the capillaries in the digestive system. • Blood that leaves the liver is taken by the……………vein to the ………cava.

4. Write out the general scheme for the synthesis of proteins. • Which type of nucleic acid is derived from the coding strand of DNA? • How many different types of amino acids are available for protein synthesis? • How many different t-RNA species are there? • In which long molecule do you find codons? • Anti-codons are associated with…………………… acids. • Two distinct structural characteristics distinguish RNA from DNA. Which are they? • Draw two different amino acids structures employing R1 and R2 side chains. • Show how these two can combine to form a dipeptide.

5. Indicate the type of bond which results and justify why we call this a dehydration reaction. • A hypothetical strand of DNA has the sequence: ATAAGCGCGTACCGA. Derive the RNA sequence. • UAU UCG CGC AUG GCU • Based on your derived sequence, list the anti-codon triplets which are complementary. • AUA AGC GCG UAC CGA • On which structure does protein synthesis take place?

6. WEEK 9 BEGINS HERE THE URINARY SYSTEM ( RENAL PHYSIOLOGY )

7. Urinary system removes most wastes generated by our physiological processes Functional organisation of the kidney How the kidneys remove metabolic waste products from the blood plasma How is urine produced Regulatory mechanisms controlling production & concentration of urine Transport of urine to the urinary bladder and release into the environment

8. Functional structures in the RENAL SYSTEM from Dorsal Aorta to Vena Cava Renal Artery Left Kidney Right Kidney Left Renal Vein Ureter Ureter Urinary Bladder Musclecontrollingexit to urethra Urethra Kidneys are at the level of your elbows

9. WHAT DOES the URINARY SYSTEM DO? Excretion:removes organic waste products from body fluids (plasma) Elimination: discharge of wastes into the environment Homeostatic regulation: of volume and solute concentration of blood plasma Question: What is a SOLUTE?

10. EXCRETION: is performed by the KIDNEYS Produce URINE Fluid containing water, ions and small soluble compounds Urine leaving the Kidneys flows down the 2 Ureters and then enters the Urinary bladder for temporary storage = Muscular sac

11. ELIMINATION: carried out by the BLADDER and the URETHRA process = MICTURITION or URINATION Micturition is the muscular expulsion of urine from the bladder into the urethra and thence to the outside of the body. MIC – TURE- ISHUN

12. Apart from waste removal, the urinary system has at least 5 other important functions: Regulates blood volume and blood pressure Regulates plasma concentrations of Na+, K+, Cl - , and Ca++ Assists in stabilizing blood p H Conserves valuable nutrients Assists the liver in detoxifying any poisons in plasma

13. Blood volume and Blood pressure: Kidneys control the amount of water lost in urine regulate blood volume Kidneys produce Renin, a hormone which controls blood pressure Concentration of ions in plasma: Kidneys control the amounts of ions lost in urine Stabilizing blood p H: Kidneys control the numbers of Hydrogen ions (H+) and Bicarbonate ions (HCO3-) lost in urine

14. Conservation of valuable nutrients: Kidneys prevent their loss in urine Assisting the liver in detoxification: Kidneys detoxify poisons and, in starvation, remove amino groups from amino acids so that they can be re-used in other metabolic processes

15. WHAT’S IN A KIDNEY? Kidneys are highly vascular structures containing Nephrons Nephrons are the functional units of kidneys and are responsible for filtration of blood plasma, re-absorption and secretion NEF-RONZ Question:What does ‘vascular’ mean

16. KIDNEY STRUCTURE CORTEX RENAL ARTERY MEDULLA RENAL VEIN RENAL PELVIS URETER

17. WHAT is the STRUCTURE & FUNCTION of a NEPHRON? BOWMAN’S CAPSULE FILTRATE CONTAINS Water, salts incl. NaCl Bicarb ions (HCO3-) Hydrogen ions (H+) Urea Glucose Amino acids Some drugs To RENAL PELVIS LOOP OF HENLE

18. BOWMAN’S CAPSULE DIRTY CLEANED GLOMERULUS

19. BLOOD SUPPLY in RELATION to LOOP of HENLE To RENAL PELVIS

20. There are about 1.3 million Nephrons per kidney Blood flow through kidneys: 1200 ml per minute is filtered at the Glomerulus Each glomerulus is composed of a network of about 50 intertwining capillaries The process of filtration takes place within Bowman’s Capsule. Blood pressure forces water and dissolved solutes out of the capillary blood and they are collected in the Bowman’s Capsule, as Filtrate. Filtrate now travels along the tubular part of the Nephron, and in doing so, it gradually changes in composition.

21. Filtrate travels from Bowman’s Capsule to Proximal tubule then to the Loop of Henle then to the Distal tubule then to the Collecting duct then to the Renal pelvis And lastly enters the Ureter Bladder Urethra Outside

22. WHAT is HAPPENING to the FILTRATE on its JOURNEY THROUGH the NEPHRON ? Cells in the walls of the Proximal Tubule actively remove ions and organic nutrients absorb water continuously from the filtrate ( only 30 % of the volume remains) Cells in the walls of the descending Loop of Henle actively remove more water, leaving a small volume of concentrated fluid in the Loop

23. WHAT is HAPPENING to the FILTRATE on its JOURNEY THROUGH the NEPHRON ? Cells in the walls of the ascending Loop of Henle are IMPERMEABLE to water activelytransport Na+ and Cl- out of the fluid remaining in the filtrate Cells in the walls of the Distal Tubule andCollecting Duct make final adjustments to the concentration of the fluid by controlling permeability to water and by reabsorption and secretion of ions

24. VASA RECTA = the blood vessels which surround the Loop of Henle They absorb the solutes & water which have been re-absorbed by the Loop and by the Collecting Ducts By transporting the solutes & water into the blood stream, the Vasa Recta vessels maintain a concentration gradient across the Renal Medulla The concentration gradient encourages the osmotic flow of water OUT of the tubular fluid, which makes the fluid more concentrated

25. Once the fluid reaches the Renal Pelvis, there is no further adjustment The concentrated fluid is now URINE, and it enters the Ureters Peristaltic contractions of the Ureters force URINE into the Bladder Micturition Reflex This reflex co-ordinates the act of Urination As the bladder fills with urine, Stretch Receptors on cells in the bladder wall are stimulated Receptors send action potentials via the spine, to the brain You become aware of the need to empty the bladder ( > 200 mL) Brain then sends message to relax the muscle at the exit to the bladder Urination

26. NEW TOPIC: 4 MECHANISMS of INTERCELLULAR COMMUNICATION

27. 1. DIRECT:Using transmission thru Gap Junctions. Chemical modulators: ions and small molecules Distribution of effects: limited to adjacent cells

28. 2. PARACRINE: Through extracellular fluid A cell produces a chemical factor to induce changes in nearby cells. The factor might be a protein or a small peptide Nearby cells must have appropriate receptors Distribution of effects: limited to a very local area

29. 3. ENDOCRINE: Through the bloodstream Chemical mediators: Hormones Distribution of Effects: Target cells are primarily in distant tissues and organs, and must have appropriate receptors

30. 4. SYNAPTIC: Across synaptic clefts Chemical mediators: neurotransmitters Distribution of Effects: limited to a very specific area Must have appropriate receptors on the post-synaptic cell membrane

31. HORMONES 1. Produced by cells in glands 2. How do they work? 3 ways A.stimulate synthesis of an enzyme or a structural protein not already present in the cytoplasm, by activating appropriate genes in the cell nucleus B.increase or decrease rate of synthesis of a particular enzyme or other protein by changing the rate of transcription or translation C.turn an existing enzyme or membrane protein channel “on” or “off”, by changing its shape or structure

32. WHAT TYPES OF HORMONES ? Derivatives of amino acids example: thyroid hormones Peptides example: insulin Derivatives of lipids example: steroid hormones

33. HORMONE ACTION A peptide hormone (= First messenger) that binds to its specific receptor on the cell membrane cannot directly affect the activities inside the cell. To overcome this, the activation of a molecule already in the cytoplasm is required. This is called a Second messenger c-AMP

34. INSULIN - PARTICULAR EXAMPLE of a PEPTIDE HORMONE Produced by cells in the Pancreas Important in treatment of Type 1 Diabetes Binds to its Specific Receptor on the cell membrane Receptor sends a chemical signal to the cytoplasm which causes a protein molecule, called GLUT 4, to be translocated to the cell membrane. GLUT 4 then acts as a channel to admit glucose molecules into the cell. Glucose cannot simply diffuse into the cell. Insulin is always required. INSULIN GLUT4 Glucose molecules Receptor Vesicle, containing GLUT4