Digestion of large food molecules
Food = starch, protein, lipids.
These molecules are very large.
They need to be digested before being absorbed.
Absorption of food molecules requires them to pass into a cell lining the gut. To do so molecules must be small and soluble.
Large molecules like polysaccharides, proteins and lipids need to be broken down into their building blocks before absorption.
Large molecules are not useful. Plants may contain a lot of starch which is good for releasing energy, but only after it has been digested down to glucose.
ie. Steak contains proteins but not the exact same ones we need. If we break the protein into amino acids, we can use them as monomers or "building blocks" to produce exactly the right protein.
Function of the digestive system
Stomach: - temoporarily stores food, chemically digest proteins, kill pathogens
The stomach recieves food from the mouth via the esophagus. Food is stored in the stomach for a while because digestion in the small intestine can take place. It is moved along by waves of muscle contractions of the inestinal wall called peristalsis. Pepsin (enzyme) chemically digests proteins and breaks them down into shorter polypeptides. pH of stomach is very low, to protect from disease and kill pathogens.
Small intestine: - digestion, absorption of products of digestion
Enzymes are secreted into the small intestine from 2 sources - wall, and exocrine part of pancreas. They are responsible largely for digestion. Bile is also secreted here. (not an enzyme). It breaks drops of fat into smaller drops (emuslification) so that the enzyme (pancreatic lipase) has more surface area to work on. The SI is super long, ( 6 metres) has folds on inner surface, villi, and microvilli = all increase surface area.
Large intestine: - absorption of liqures and minerals
During digestion, lots of fluid is added to the "food" as it moves through the alimentary canal. Glucose is actively absorbed in the SI and minerals are actively absorbed in the LI and water follows by osmosis.
Control of heartbeat
The heartbeat is controled with myogenic muscle contraction, involving the pacemaker, nerves, the medulla of the brain and epinephrine (adrenline)
Contraction of cardiac muscles - myogenic (originate from heart muscle) They happen because of nerve impulses from (inside heart, specifically, right atrium) the Sino-Atrial Node (SA Node) also known as the cardiac pacemaker. (can install artifical pacemaker)
The SA node is made from specialised muscle cells - releases impulse at regular intervals which spread across walls of atria causing simult. contractions. SA node doesn't spread to ventricles except region of the Atrio-Ventricular Node)
The AV node is connected to the "bundle of His" which branches out into the Purkinje tissue. From the AV node, impulse travels through BofH down to apex of heart and spreads up PT. Causes ventricular contractions to push blood up into arteries.
Heart is largely autonomous, brain and hormones CAN influence it. Impuse from lower part of brain (medulla) decrease cardiac frequency. Impulses from brain via sympathetic nerves can INCREASE cardiac frequency.
Adreneline (horomone) from adrenal glands near kidneys can influence cardiac frequency
Structure and function of arteries, capillaries an
Arteries - transport blood very fast away from heart (oxygenated apart from pulmonary artery)
thick muscular walls and layer of collagan for support - resists expansion due to high pressure of blood. The muscle layer contracts on pulse of blood maintaining pressure all the way to tissues.
Veins - transport blood at moderate speed towards heart( except hepatic portal vein) (de-oxygenated except pulmonary vein)
quite thin walls and valves (to prevent blood from flowing back.
Carry blood under low pressure so the lumen is wide to reduce the resistance to blood flow.
Capillaries - numerous blood vessels in tissue. Thin walls (single layer of endophilium) to allow easy exchange of material eg. respiratory gases. Move blood at low speed, and moderate pressure.
Antibiotics and viruses
Antibiotics - ie. aminoglycosides block protein synthesis in bacteria but no in eukaryotic cells.
Bacteria and animal cells synthesise in a similar manner but different proteins are involved. Useful antibiotics use these differences to bind to or inhibit the function of the bacterial proteins. They prevent new proteins and new bacterial cells without damaging the patient.
Most bacteria have a cell wall. Antibiotics may disrupt this cell wall which will interfere with the life cycle of the bacteria. Eukaryotic animal cells do not have cell walls so are not affected by the antibiotic. Viruses also do not have a cell wall.
Viruses invade a cell and get this host cell to produce protein and DNA that the virus needs. The virus uses the host's processes - so antibiotics can't hurt them
If they did antibiotics would also disrupt the process of protein synthesis in the host (a serious problem)
Role of skin
Best way to prevent disease is to prevent pathogens from entering the body.
When skin is unbroken, it is almost impossible for any micro-organism to penetrate the skin.
Weak points are those where we do not have skin. However these areas have their own barriers. Mucus is often used - it traps micro-organisms and prevents further entry.
Lungs are protected by mucus and cilia which transport the mucus to the throat.
The stomach is very acidic.
Glands above the eyes produce tears that contain lysozymes ( enzyme) which destroy bacterial cell walls
The vagina produces mucus and has an acidic environment.
Role of phagocytic leucocytes
Despite measures of skin and mucus to keep pathogens out of the body, many get in.
This is called infection - successful invasion of the body by pathogens, but does not always lead to disease.
Leucocytes (white blood cells) are the body's defense against pathogens after they have entered. They can be found in the blood but also in tissues e.g lungs.
Several different kinds of leucocytes exist - some are phagocytic ie they eat any cell not recognised as their own. (phagocytosis)
They determine foreign bodies by a code on the outside of the cell surface membrane.
There are many different kinds of antibodies - they are produced by different kinds of lymphocytes.
Each different lymphocyte can recognize a particular kind of antigen and produce antibodies that work against this antigen.
1. Antigen enters organism
2. Lymphocyte produces right kind of antibody that will recognize antigen.
3. This lymphocyte will divide many times forming a clone.
4.. This clone is a group of lymphocytes all producing the same antibody.
5. They produce alot of this antibody
6. Antibody will attach itself to antigen that has entered the organism and make it harmless.
HIV and the immune system
The Human Immunodeficiency Virus (HIV) is a virus that infects the cells of the immune system.
It reduces the number of lymphocytes that are actively involved in the production of antibodies.
As a result the infected person makes a much lower number of antibodies and is therefore much more likely to develop disease.
These diseases are called opportunistic diseases and they are the major cause of death of people who have been infected with HIV and developed AIDS.
Mechanism of ventilation
The mechanism of ventilation of the lungs occurs in terms of volume pressure changes, caused by the internal and external intercostal muscles, the diaphragm and the abdominal muscles.
Inspiration - the daiphragm contracts and flattens downwards.
- The external intercostal muscles contract, pulling the ribs up and out. This increases the volume of the thorax and the lung and alveoli volume. Decreases the pressure of the air in the alveoli, meaning air flows in to equalise pressure
Expiration - diaphragm relaxes and curves upwards
- external intercostal muscles relax, allowing the ribs to fall. This decreases the volume of the thorax and lung and alveoli volume. Increases pressure of air in the alveoli so air flows out to equalise the pressure
- abdominal muscles contract, pushing the diaphragm upwards
- the intercostal muscles contract, pulling the ribs downward - this gives larger/faster expiration used in exercise
Role of hormones in the menstrual cycle
There are 4 hormones involves in control of the monthly cycle.
Follicle Stimulating Hormone and Luteinizing Hormone are produced by the anterior lobe of the pituitary gland in the brain. Estrogen and Progesterone are produced in the ovaries.
1. FSH is released from pituitary gland - about the size of a pea and deep within brain.
2. It stimulates the ripening of the follicle.
3. Growing follicle releases estrogen.
4. Estrogen increases the thickness of the endometrium and inhibits FSH + stimulates LH.
5. LH stimulates ovulation and the formation of the corpus luteum.
6. Corpus luteum produces progesterone which keeps endometrium intact + inhibits both FSH and LH.
7. Fertlisation doesn't occur, corpus luteum degenerates and FSH is produced again.
Process of in vitro fertlization (IVF)
IVF is when the egg and sperm cells meet outside the female's body.
IVF is used on women who have blocked fallopian tubes, or cannot sustain pregnancy.
Egg cells of woman who wants to be pregnant can be used, or donor egg cells.
1. Woman who is generating egg cells is treated with hormones so more than one follicle will ripen.
2. Needle is placed in follicle and egg cell is removed. repeated until all egg cells are taken
3. Egg cells are mixed with sperm cells, if quality is poor it is injected.
4. The fertilized egg cells are cultivated and are either placed inside uterus or frozen.
5. Number placed depends on policies of country or opinion of doctor.
6. If all embryos are implanted successfully, can lead to multiple pregnancy that may result in premature delivery and a reduced change of survival for the babies.
Ethics of IVF
- the creation of life in a laboratory
- freezing embryos and keeping them in case they are needed
- discarding surplos embroys or using them for stem cell research
- possiblity of creating embryos for research
- possiblity of selecting embryos
- potential possibility of modifying embryos
- birth mother may not be genetic mother
- elderly women can have babies