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
Peptide Hormones
- Hydrophilic and lipophobic so they cannot move freely across the membrane
- bind to receptors on the surface of the cell and activates a series of intracellular molecules called second messengers causing cell activity (signal transduction)
What is the use of the second messenger in Peptide hormones
Enables the amplification of the initial signals since more molecules are activated
Hypothalamus
Part of the brain that links to nervous and endocrine to maintain homeostasis
- Initiate endocrine
- Secrete releasing factors which target the anterior lobe of the pituitary gland
- secretes hormones directly into the blood into the posterior pituitary lobe
Pituitary Gland
Direct contact with the blood portal system
endocrine - no duct
Anterior Lobe
releasing factors cause the release of specific hormones into the bloodstream. These relate to glands
Posterior Lobe
releases hormones produced by the hypothalamus itself. Relates to nerves
What does the Pituitary gland control
Metabolism
Adult Development
Reproduction
Growth
Homeostasis
What do growth hormones do
Reduce the formation of adipose cells acting indirectly with insulin growth factors. (Increase muscle mass and bone size)
What is lactation regulated by
oxytocin and prolactin
Prolactin in Lactation
production of milk
- Secreted by the anterior pituitary as a response to the release of PRH (prolactin-releasing hormone)
- Inhibited by progesterone (prevent milk during birth)
Oxytocin in Lactation
release of milk
- produced in the hypothalamus
- triggered by sensory receptors in the breast by the suckling infant
- continuous oxytocin secretion until the infant stops feeding
Specialised cardiac muscle cells
- Contract without stimulation
- Branched faster signalling
- Not fused they are connected by gap junction at intercalated discs important as it allows for independent contraction
- lots of mitochondria for aerobic respiration
sinoatrial node
A cluster of cells in the right atrium acts as a primary pacemaker which controls the rate of heartbeat. Electrical signals sent out and stimulate contraction on atrial walls simultaneously
Connective tissue between atria and ventricles
helps to anchor valves and cant conduct electrical signals so second node must be used
atrioventricular node
second node that separates atrial and ventricular contractions. Helps with electrical signals however slower than sinoatrial
Why is the delay in contractions between the atrioventricular and sinoatrial nodes important
Allows blood to fill up ventricles before the valves close
Ventricular Contraction
sends signals down the septum by a specialised bundle of cardiomyocytes (bundle of his). Causing it to contact and ensuring contraction begins in the bottom forcing blood up
Diastole
A period of Heart relaxing after contraction to fill with blood. Stops muscle from becoming fatigued
Atrioventricular valves
(tricuspid and bicuspid)
Stops it flow back into atria
Semilunar valves
(pulmonary and aortic)
Stops flow back into ventricles
What is the first heart sound caused by
closure of the atrioventricular valves
What is the second heart sound caused by
closure of the semilunar valves
What is a p Wave
depolarisation of the atria
what is a QRS complex
depolarisation of the ventricles
what is a T wave
repolarisation of the ventricles
Cardiac output equation
Heart Rate x Stroke Volume
How is heart rate increased
sympathetic nervous system
How is heart rate decreased
parasympathetic stimulation
Systolic blood pressure
Higher shows pressure following contraction of the heart
Diastolic blood pressure
Lower shows pressure of the heart when it relaxes between beats
Type 1 Pneumocyte
mediate gas exchange with the bloodstream therefor is thin
Type 2 Pneumocyte
secretes pulmonary surfactant to reduce surface tension
alveolar air space
a dense network of capillaries that transport respiratory gases in the lungs
cooperative binding
makes o2 binding to haemoglobin easier as every time o2 binds it alters it slightly. Higher affinity for o2 in oxygen-rich areas (oxygen loading) vs low affinity in oxygen-poor (oxygen unloading)
why is the saturation of haemoglobin not linear?
Because binding potential changes with each additional O2 molecule
Adult Haemoglobin dissociation curve
Sigmoidal (s-curve)
- Low saturation of haemoglobin when o2 levels low and vise-versa
Fetal Haemoglobin dissociation curve
Has a higher affinity for oxygen so the dissociation curve shits to left
- Therefore it will load o2 when an adult is unloading
Myoglobin
an oxygen-binding molecule that is found in skeletal muscle tissue and is not capable of cooperative binding. The curve is logarithmic.
- Saturated at low oxygen levels as it has a high affinity
- hold onto its o2 supply until levels in the muscles are very low
How is co2 transported
- Bound to haemoglobin
- dissolved into water (very little)
- converted into carbonic acid (most)
Transport as Carbonic Acid
- co2 combines with h2o to form carbonic acid
- dissociated from h+ and bicarbonate
- bicarbonate pumped out cl- comes in
- bicarbonate with sodium in blood plasma form sodium bicarbonate which travels to the lungs
- H+ makes less alkali which means haemoglobin releases o2 and absorbs H+ to maintain PH
- Blood reaches the lungs bicarbonate is pumped back and the process reversed
Chemoreceptors
detect PH change
How do lungs regulate blood PH
Regulate amount of Co2 In the blood stream by changing ventilation
How do kidneys regulate blood PH
Control reabsorption of bicarbonate ions
Bohr Shift
the bohr effect is when there is a decrease in PH and its shifts the oxygen dissociation to the right as haemoglobin releases oxygen.
How does metabolism affect the release of oxygen
Increased metabolism will result in a greater release of co2 as haemoglobin is promoted to release its o2 at its greatest needs
Central chemoreceptors
control respiration by detecting changes in co2
Peripheral chemoreceptors
detect CO2 levels, as well as O2 levels and blood pH
miotic index
pmat/pmat+Interphase
