Option Topic: Human Physiology Flashcards
Why are hormones released when you are hungry or full
- Stretch receptors in the stomach or intestines
- Adipose tissue in response to fat storage
- Pancreas in response to blood sugar levels
Which hormone grows hunger?
Ghrelin
Which hormone lowers hunger?
Leptin
Exocrine glands
- Secrete substances via a duct onto the epithelial surface. (body, lumen of digestive tract)
- composed of a cluster of secretory cells which form acinus
What are digestive juices controlled by
- Nervous Mechanism
- Hormonal Mechanism
The nervous mechanism in gastric secretion
- The smell of food produces an immediate response
- When food enters the stomach, sensed by stretch receptors
- Signals sent to the brain trigger digestive hormones to sustain gastric stimulation
The Hormonal Mechanism in gastric secretion
- Gastrin is secreted into the bloodstream to stimulate the release of stomach acid
- If Ph is low gastrin secretion is inhibited
- When food passes through the small intestine duodenum releases digestive hormones: Secreyin + CCL stimulate the pancreas and liver to release digestive juice (neutralise stomach acid + bile emulsify fats)
What are the uses of Stomach Acid
- dissolves chemical bonds within food molecules
- pepsin is activated when pepsinogen is in acidic conditions
- Prevents pathogenic infection by killing bacterial
How to protect the organs from stomach acid
- Mucus layer in the stomach
- Pancreas releases bicarbonate ions into the duodenum to neutralize stomach PH
How is low PH environment maintained
Proton pumps secret H+ ions that combine with Cl- ions to form HCL
What is PPL
proton pump inhibitors bind to the proton pump and prevent H+ ion secretion. Helps to raise PH and prevent gastric discomfort
May have more susceptibility to gastric infection
Features of villi
- Microvilli - increase SA
- Rich blood supply - Fast transportation of material
- Singular Layer - Fast diffuson
- Lacteals - Absorbs lipids into the lymphatic system
- Intestinal glands - Release digestive juices
- Membrane protein - Helps transport digested material
How do villi optimize the absorption of digested material
Tight junctions - Impermeable membrane to keep digestive fluid separated from tissue keeping a concentration gradient
Microvilli - Increased SA
Mitochondria - Provide ATP for active transport mechanisms
Pinocytotic Vesicles - non-specific uptake of fluids. Quick way of translocating
Large VS Small intestine
Small absorbs usable food substances and does the final breakdown of food
Large absorbs water and dissolved minerals
what is Roughage
- Provides bulk in the intestine to help material move
- Absorbs water to keep bowel movement
What is Egested
Bile Pigments, Epithelial Cells, Lignin, Cellulose, Bactertia
how does blood flow in the liver?
Receives oxygenated blood through the hepatic artery and nutrient-rich blood from the portal vein
Deoxygenated blood is transported from the liver via the hepatic vein
What does the liver do?
process the nutrients absorbed from the gut
- Storage of key nutrients
- Detoxification of potentially harmful ingested substances
- Produces plasma proteins to maintain sustainable osmotic conditions
- Breakdown of red blood cells and production of bile salts
Hepatic lobules
- surrounded by hepatic artery (oxygen) and portal vein (nutrients)
- Vessels drain into sinusoids which exchange material with hepatocytes
- sinusoids drain into a central vein which feeds deoxygenated blood into the hepatic vein
- Hepatocytes produce bile which is transported into bile ducts
Sinusoids
blood vessel with an increased permeability which allows for larger molecules to leave and enter the bloodstream.
Carbohydrate metabolism
excess glucose is taken and stored as glycogen. And when there is too much glycogen is converted to other substances (fat)
Protein metabolism
amino acids cannot be stored so they are broken down into amine groups which are considered toxic. Therefor liver will remove them nd convert them into something harmless such as urea.
Fat Metabolism
stored by liver and exported to cells.
Low density lipoprotein - Transports cholesterol to cells (raise blood cholesterol levels)
High density lipoprotein - Transport excess cholesterol from cells back to the liver (lowers blood cholesterol levels)
Extra cholesterol is converted into bile salts
Detoxification in Liver
- converted into less harmful chemicals: mediated by cytochrome P450 enzyme group. Produce damage free radicals neutralized by antioxidants
- Converted chemicals attach to other substances. makes less harmful and is water soluble and easily excreted from the body
Plasma protein
the protein present in the blood plasma. Produced through RER and exported into the blood by the Golgi complex
Types of plasma protein
- Albumins - Regulate osmotic pressure
- Globulins - Act as a transport protein
- Fibrinogens - involved in the clotting process
Erythrocyte Recycling
Red blood cells have a short life span. And the liver is responsible for the breakdown and recycling of its components.
What are Kupffer cells
Phagocytes that specialize in the breakdown of red blood cells
- Haemoglobin is broken down into globin and the iron-containing heme group
- Globin digested to produce amino acids
- Heme group are broken down into iron and bile pigment
What happens to the iron in Erythrocyte Recycling
Iron released must be complexed to avid oxidation
- stored by the liver in the protein shell of ferritin
- transported to bone marrow
Endocrine Glands
Release chemicals into blood to help regulate functions. They are specific and slower in response compared to the nervous system.
Steroid Hormones
- Lipophilic and diffuse across membranes of cells freely
- They bind to cytoplasm receptors or nucleus to form active receptor hormone complexes. Wich binds to DNA acting as a transcription factor for gene expression