Option: Human Phys Flashcards
Define Hormone
Is a chemical messenger that is transported indiscriminately via the bloodstream to act on a distant target cells.
Define Steroid Hormones
Are lipophilic hormones that are able to freely diffuse across the plasma membrane of cells.
How do steroid hormones work?
They bind to receptors in either the cytoplasm or nucleus of the target cell, for an active receptor-hormone complex.
This activated complex moves into the nucleus and binds directly to DNA, acting as a transcription factor for gene expression.
Define Peptide Hormones
They are hormones that are hydrophilic and lipophobic, thus cannot freely cross the plasma membrane.
How do Peptide Hormones work?
They bind to receptors on the surface of the cell, which are typically coupled to internally anchored proteins.
The receptors complex activates a series of intercellular molecules called second messengers, which initiates cell activity. This process is called signal transduction.
The use of second messengers enables the amplification of the initial signals as more molecules are activated.
Define Hypothalamus
A section of the brain that links the nervous and endocrine systems in order to maintain homeostasis.
Define Growth Hormones
Is an anabolic peptide hormone that stimulates growth.
Define Lactation
The production and secretion of milk by maternal mammary glands following birth.
Define Autocrine
Occurs when chemicals released by a cell stimulate the cell itself (self-signalling).
Define Paracrine
Occurs when chemicals released stimulate a neighbouring cell.
Define Endocrine
Occurs when chemicals released travel in the bloodstream to activate distant cells.
Define constitutive secretion
Hormones are released as they are produced [vesicles fuse directly with cell membrane].
Define regulated secretion
Hormones are stored in vesicles and only released following an external signal.
Define Negative Feedback
Involves a response that is the reverse of the change detected.
Define Positive Feedback
Involves a response that reinforces the change detected.
Nutrients
A chemical substance found in foods that is used in the human body.
Define Essential Nutrients
Nutrients that cannot be synthesised by the body and must be ingested as part of the diet.
Vitamins
Organic molecules with complex structures that are diverse and clasifed into groups.
Types of malnutrition
Stunting
Wasting
Obesity
How are fats and cholesterol transported?
Both do not dissolve in the bloodstream and hence are carried by lipoproteins
LDL
Low density lipoproteins
saturated trans fats
From liver to rest of the body
HDL
High density lipoproteins
cis polyunsaturated fats
From body to liver
Phenylketonuria
Genetic condition (autosomal) that results in impaired metabolism of phenylalanine.
Caused due to mutation in gene encoding for enzyme (phenylalanine hydroxylase) that breaks excess phenylalanine into tyrosine.
Normal:
excess phenylalanine –> Tyrosine
With PKU:
Excess phenylalanine –> phenylpyruvate or phenylketone
How are release of hormones for hunger triggered?
- Stretch receptors in the stomach and intestine become activated when ingested food distends these organs
- Adipose tissue releases hormones in response to fat storage
- The pancreas will release hormones in response to changes in blood sugar concentrations
Which hormone triggers hunger response?
Stomach: ghrelin
Pancreas: glucagon
Which hormone triggers satiety response?
Adipose tissue: leptin
Intestine: CCK
Hypertension
Abnormally high blood pressure
Type II diabetes
Occurs when fat, liver and muscle cells become unresponsive to insulin (insulin insensitivity). Results from a diet rich in sugars causing the progressive overstimulation of these cells by insulin
Starvation
Describes the severe restriction of daily energy intake, leading to a significant weight loss.
Anorexia nervosa
An eating disorder in which individuals severely limit the amount of food they intake
Tight junction
Occluding associations between the plasma membrane of two adjacent cells, creating an impermeable barrier
Pinocytosis
is the non-specific uptake of fluids and dissolved solutes (a quick way to translocate in bulk)
Fibres
Indigestible portion of food
Stomatch ulcers
inflamed and damaged areas in the stomach wall, typically caused by exposure to gastric acids.
Vibrio cholerae
A bacterial pathogen that infects the intestines and causes acute diarrhoea and dehydration
Bacteria that causes stomach ulcers
Helicobacter pylori
Bacteria that causes dehydration and diarrhoea
Vibrio cholerae
Function of the liver
- Process nutrients absorbed by gut, hence regulates the body’s metabolic processes.
- Responsible for the storage and controlled release of key nutrients (e.g. glycogen, cholesterol, triglycerides)
- Detoxification of potentially harmful ingested substances (e.g. amino acids, medications, alcohol).
- It produces plasma proteins that function to maintain sustainable osmotic conditions within the bloodstream,
- Responsible for the breakdown of red blood cells and the production of bile salt.
Sinusoids
A type of small blood vessel found in the liver that are needed for material exchange. They have increased permeability, allowing larger molecules (e.g. plasma proteins) to enter and leave the bloodstream.
How are sinusoids different from capillaries?
- They have an incomplete basement layer
- Their endothelial layer contains large intercellular gaps and less tight junctions allowing larger molecules to pass.
How are drugs broken down in the liver?
Toxins are fat soluble but not water soluble hence they are difficult to excrete.
1. Toxins are converted into less harmful chemicals via oxidation, reduction and hydrolysis reactions using cytochrome P450 enzymes.
- This conversion produces damaging free radicals which are neutralised by antioxidants within the liver.
- Next conjugation reaction takes place, where the converted chemicals are attached to another substance to make it less harmful and water soluble in order to be carried out of the body via urine.
What are the nutrients stored in the liver
glycogen
iron
vitamin a
vitamin d
Protein metabolism
amino acids cannot be stored in the body this need to be broken down. They release an amine group which is toxic and the liver is responsible for the removal of this (deamination). The amine is converted to urea and excerpted out.
Fat metabolism
Liver converts excess carbohydrates and proteins into fatty acids and triglycerides.
It is responsible for the synthesis of large quantities of phospholipid and cholesterol.
