What is the order of events that occurs in the body after food is consumed?
What is the role of enzymes in the process of digestion?
The energy input for the reactions to take place is generally in the form of heat. As the internal temperature of our body is constant, enzymes reduce the activation energy (heat) needed for hydrolysis reactions to take place.
What is the alimentary canal?
It is the canal of the digestion system that starts with the mouth and ends with the anus. This canal has to accessory organs (pancreas and liver), which are connected to the canal with ducts.
Explain movement through the digestive system
The alimentary canal is made up of two types of smooth muscles, which are muscles controlled by the autonomous nervous system. These two types are circular and longitudinal muscles, which contract to perform peristalsis, which is the movement of food. The peristalsis performed in the stomach mixes the food with the digestive secretions (churning)
Where are nutrients absorbed?
Either into the bloodstream or into the lympathic system (usually non-polar fatty acids and larger molecular size)
Small intestine from outside to the inside?
- Longitudinal muscle, circular muscle, villi (mucosa), lumen (epithelium)
- Additionally, the same arrangement without the villi would be found in the oesophagus, stomach and large intestine.
What is the role of pancreas?
- Produces insulin and glucagon for the metabolism of glucose
- Produces 3 digestive enzymes which are released into the small intestine through a duct. These enzymes are: lipase, endopeptidase and amylase.
What are the two enzymes that metabolise proteins into polypeptides?
Trypsin (stomach) and endopeptidase. After these two enzymes metabolize long polypeptides into smaller peptides, other enzymes hydrolize these polypeptides into amino acids.
Explain the digestion of starch.
The digestion of starch begins in the mouth, as amylase in saliva metabolizes it into maltose. Due to the highly acidic environment in the stomach, no digestion occurs. As the pH environment of the small intestine is neutral, amylase released from the pancreas begins to be active again when the food reaches the small intestine. The enzyme maltase released from the plasma membrane of epithelial cells on the surface of the lumen digests maltose into two molecules of glucose.
How are nutrients absorbed by the small intestine?
Each villus has microvilli on its epithelial cell surface. Each villus contains a capillary bed for the quick transportation of the absorbed nutrients into the bloodstream. Additionally, there is a lacteal, which is a small vessel of the lymphatic system, that absorbs larger non-polar molecules. Blood from arteriole enters the capillary bed and leaves through the venule with the nutrients absorbed.
What are the transport mechanisms used by epithelial cells to absorb nutrients?
- Simple diffusion: Fatty acids that easily move in the phospholipid bilayer
- Facilitated diffusion (following a concentration gradient but through a protein channel: Glucose and amino acids
- Membrane pumps (against concentration gradient with ATP powered pumps): glucose and amino acids in certain circumstances
- Endocytosis (pinocytosis and phagocytosis): large molecules that have not been fully digested
What are arteries?
Blood vessels that take blood away from the heart that has not yet reached a capillary. An arteriole is the smallest of arteries. After an arteriole, the blood enters a capillary bed.
What is a capillary bed?
It’s a network of capillaries that typically all drain into a single venule (smallest of veins). When blood enters a capillary bed, blood pressure is lost. Most capillaries are single-cell thick for chemical exchanges to occur easily. All exchanges occur in capillaries. No exchanges occur in arteries or veins. Capillaries also have pores to allow for faster diffusion.
What are veins?
Blood vessels that collect the blood from capillaries and return it to the heart.
How do we identify arteries and veins?
- NOT based on whether the blood is oxygenated or deoxygenated.
- Arteries have a relatively thick smooth muscle layer inside the lumen of the blood vessels. In addition, arteries have elastic fibres that help maintain high pressure between pump cycles. Arteries must be able to maintain high pressure, as blood is pumped directly from ventricles to arteries.
- Veins have thin walls and a larger internal diameter. Veins also have internal valves to ensure one-way flow. (Due to low pressure, remember pressure being lost when blood enters capillary beds!)
What are atria? (Left atrium, right atrium)
Collection chambers in the heart for the blood coming from veins. Thin walled, as the blood has low pressure.
What is a ventricle?
Thick walled muscular pump that builds enough pressure to pump the blood out from the heart and around the body.
In what sequence of blood vessels is blood generally used?
Large artery, smaller artery branches, arteriole, capillary bed, venule, larger vein branches, large vein
What are the roles of the right and left sides of the heart?
- The right side sends blood for pulmonary circulation. The left side sends blood for systemic circulation. The left side begins with the aorta, which is the artery that allows for blood to reach the entire body.
- NOTE: Left and right on a diagram are inverted!
What causes heart rate?
The heart is made up of cardiac muscle, which isn’t controlled by the autonomous nervous system. It spontaneously contracts and relaxes through what is called myogenic muscle activity.
How is heart rate controlled generally?
- The right atrium has a mass of specialized tissue that has the properties of both muscle and nervous system cells. This mass is called the SA node. The sinoatrial node sends electrical signals which initiate the contraction of the atria.
- The atrium also has a similar mass of tissue called the AV node, which receives the signal from the SA node, delays it for 0.1 seconds and sends another electrical signal which initiates the contraction of the ventricles.
How is heart rate controlled when heart rate must increase or decrease?
- An area in the brain called the medulla chemically senses the increased amount of carbon dioxide in the bloodstream. The medulla then sends a signal through the cardiac nerve to the SA, which increases the heart rate without changing the mechanism of how the heart rate is generally maintained. When the heart rate must decrease, the signal is sent by the medulla through the vagus nerve to the SA node.
- Additionally, epinephrine (adrenaline), also causes the SA node to fire more frequently than it usually does.
What is a single cardiac cycle?
All events that occur from one SA node signal to the other.
What is the term used for heart that is not contraction?
What is the term used for heart that is contraction?
Describe the changes of pressure in the heart.
- During diastole when both chambers are at rest, the atrial pressure is slightly higher than ventricular pressure, which keeps the atrioventricular valves open. The pressure in the aorta is much higher than the ventricle, which keeps the semilunar valve closed and ensures that no backflow occurs.
- When the atria are at systole and the ventricles are in diastole, the pressure isn’t very high. The atrioventricular valve remains open as all blood fills into the ventricule. The semilunar valve remains closed.
- When the ventricles are at systole and the atria are at diastole, the atrioventricular valve closes as the semilunar valve opens. After the blood is fully pumped, all chambers reach diastole as the cycle repeats itself.
What is atheroclerosis?
The build-up of plaque (cholesterol, lipids, cell depris, calcium) decreases the flexibility of arteries. When a coronary artery (artery that supplies the heart muscles with oxygen rich blood) or one of its main branches becomes blocked, the heart is deprived of its critical oxygen supply. This leads to coronary thrombosis (heart attack)
What is a pathogen?
Any living organism or virus capable of causing a disease.
Explain primary defense
- This is the first source of defence pathogens must face. It’s also the most effective, as it prevents pathogens from entering the body.
- Skin: Is made up of two layers: dermis (alive) and epidermis (dead dermis cells). Most pathogens can only enter alive cells, so the epidermis prevents pathogens.
- Other entry points in the body: These entry points are lined with mucous membrane, which secretes a lining of sticky mucus and captures pathogens. Some mucous membrane tissue have cilia. Examples for mucous membrane tissue are trachea (tube that carries air to and from the lungs), nasal passages, urethra and vagina.
Explain blood clotting
The damaged blood vessel releases chemicals that stimulate platelets (cell fragments produced in bone marrow alongside red blood cells and white blood cells) to adhere to the damaged area. The platelets and the damaged cells release chemicals called clotting factors that turn the plasma protein prothrombin into the enzyme thrombin. Thrombin catalyzes the conversion of soluble plasma protein fibrinogen into insoluble fibrous protein fibrin, which allows for platelets to effectively plug into the damaged area. More and more cell debris is collected in the fibrin mesh.
Explain primary and secondary immune response
Primary response is what occurs when the body encounters the pathogen for the first time. This immune response may last up to a week and symptoms will be experienced. Secondary immune response takes place much quicker and no symptoms are experienced.
Explain non-specific immune response
A type of white blood cell (leukocyte) microphages (which are highly small and can easily move in and out of the bloodstream) solely determine whether the pathogen is ‘self’ or ‘non-self’ and perform phagocytosis if the pathogen is determined to be ‘non-self’. The engulfed organism is then destroyed with the large number of lysosomes present in the macrophage.
What is an antibody?
Specific type of protein produced by the body in response to a pathogen. Each antibody has two attachment sites that attaches to a specific antigen. This marks the pathogen for destruction by other cells. The presence of two attachment sites also helps create clumps of pathogens, making it easier for macrophages to combat.
What are antigens?
Foreign proteins embedded in the cell membranes of pathogens.
What are plasma cells?
Plasma cells are a specific type of leukocyte that produces a specific antibody. As there generally isn’t enough plasma cells present in the body to respond to an infection and produce the necessary amount of antibodies, the body has a specific reaction to primary encounters.
Explain a typical primary immune response (polyclonal response)
- Macrophage engulfs the pathogen.
- The antigen presents the antigen on its cell membrane to be determined by helper T cells.
- T cells activate the antibody producing B lymphocytes in accordance with the antigen is identified. Many different antibodies are produced, thus this is called a polyclonal response.
- This specific type of plasma cell rapidly undergoes mitosis as an army of plasma cells is created.
- This army rapidly produces antibodies which later on circulate in the blood system until they reach the antigen carrying pathogen and eliminate it.
- Some plasma cells (B cells) remain in the blood system and continue to provide protection against the specific pathogen. These long lived cells are called memory cells.
- Memory cells respond quickly if the same antigen is encountered again.
How does AIDS occur?
- The HIV bodies target lymphocytes. The body becomes unable to produce the necessary antibodies. When a person loses their specific immune response capability, they’re said to have AIDS.
- What does the severity of the symptoms experienced in response to an infection depend on?
- The tissue targeted (nervous system vs. mucous membrane tissues)
- How quickly the virus replicates
What determines our blood types?
The different proteins on the plasma membranes of red blood cells. (A, B or Rh). In an emergency situation, blood plasma with no red blood cells may also be used for transfusion.
How do vaccines work?
The pathogen with its symptom causing abilities diminished is injected. Primary immune response takes place and memory cells are created, allowing for rapid immune response should the body encounter the pathogen again. Secondary immune response is capable of producing a significant amount of antibodies much more rapidly than primary immune response, thus little or no symptoms are presented.
What is the difference between passive and active immunity?
- Passive immunity is when an organism gains immunity by using the antibodies produced by another organism.
- Active immunity is when the organism producing the antibodies gains immunity.
What are monoclonal antibodies and how are they produced?
- Usually, the antibodies produced at the primary immune response are polyclonal. Researchers producing pure antibodies containing one type of antibody is called monoclonal antibodies.
- An animal is injected with the antigen corresponding to the target antibody
- The spleen of the animal is harvested after it undergoes primary immune response.
- The leukocytes are removed and are fused together with myeloma cells to create hybridoma cells. This is done to make sure that the B cells remain alive. As myeloma cells are cancer cells, they have a very long life span and are virtually immortal.
- The ELISA test helps determine and identify the cultures secreting the target antibody. These cultures are then isolated.
How do pregnancy tests work?
Hybridoma cells producing specific HCG (hormone only found in the urine of pregnant women) antibodies cause a color change in the enzyme they are bound to after they encounter HCG.
What causes allergies?
- When B cells encounter pollen, dust, nuts etc., they produce IgE antibodies.
- The IgE antibodies bind to mast cells (special type of leukocytes) which produce histamine.
- Histamine is the chemical that leads to the characteristic symptoms of allergies. (such as itchy nose, blotchy skin, sneezing)
What is ventilation?
Filling our lungs with air and then expelling that air is called ventilation.
What are alveoli?
The multitude of spherical air sacs in our lungs.
What are the structures in our lungs?
- Trachea: mucus membrane tissue with cilia that carries air in and out of our longs
- Bronchi and Bronchiole: Structures carrying air to and from the alveoli.
What are the muscles involved in the process of ventilation?
- Diaphragm, muscles of the abdomen, external and internal intercostal muscles (which surround the ribs)
- Internal intercostal muscles are used during expiration.
- External intercostal muscles are used during inspiration.
What happens to the diaphragm during inspiration and expiration?
Diaphragm moves down during inspiration and moves up (relaxes) during expiration.
- The diaphragm contracts (moves down) as external intercostal muscles help raise the rib cage. This increases the volume of the thoracic cavity.
- Due to the increase in volume of the thoracic cavity, the pressure within decreases. This allows for the lungs to expand.
- Due to the expansion in the lungs, there is a decrease in the amount of pressure within. This creates an air vacuum and causes air to fill up inside the lungs and into the alveoli.
- The exact opposite occurs during expiration. During heavy breathing and exercise, the volume of the thoracic cavity increases more.
- Explain the movement of air inside the lungs
- Smaller Bronchi
- Here, the O2 diffuses into the blood that is flowing through the capillary bed surrounding the alveoli. CO2 diffuses into the alveoli and is moved out.
What is the single cell layer that makes alveoli composed of?
- Type 1 Pneumocytes: Very thin, facilitates diffusion. Incapable of mitosis.
- Type 2 Pneumocytes: Produces mucus surfactant which reduces surface tension and prevents alveoli from sticking to each other. Capable of mitosis.
What is emphysema?
Disease characterized by the slow depletion of alveoli. Causes shortness of breath as it reduces the surface area for gas exchange. Leading cause is smoking.
How are alveoli adapted to gas exchange?
- Single layer of cells
- Type 1 is very thin
- Type 2 prevents sticking by producing surfactant
- Surrounded by capillary bed for easier diffusion
- They’re in the shape of bags, which increases the surface area available for gas exchange
What is the central nervous system?
It’s the brain and the spinal cord. These structures receive sensory information, interpret and process that information. If needed they trigger a motor response.
What are neurons?
Neurons are cells that have evolved to transmit electrical impulses. Sensory neurons are cells that carry information to the CNS, and motor neurons carry the information from the CNS to the intended structure. Sensory and motor neurons together form peripheral nerves
What are nerves?
- A group of many individual neurons surrounded by a protective sheath. There are two types of nerves:
- Spinal nerves: Emerge from the spinal cord
- Cranial nerves: Emerge from the brainstem
What are the main parts of a neuron?
Dendrites (receive impulse), cell body and axon (carries impulse). At the end of axon there are terminal buttons that release neurotransmitters that continue the impulse to the next neuron.
What is the myelin sheath?
Protective membranous structure made of multiple layers of Schwann cells that surrounds the axons of neurons belonging to organisms with highly developed nervous systems. The small gaps between the Schwann cells are called Ranvier nodes. This sheath significantly increases the rate at which action potential passes down the axon, as the electrical impulse jumps from one node of Ranvier to the next through Saltatory Conduction. This also reduces the amount of ATP needed, as there is only need for K/Na pumps to operate at nodes of Ranvier rather than the entire axon.
Explain action potential
- Resting Potential: The time period when the neuron is not carrying an impulse, but is ready to do so. The Na/K pumps actively pump Na out and K in (3 Na out for every 2 K in), creating a net negative charge inside the axon membrane along with the permanent negatively charged organic ions inside the axon.
- Depolarization: When a minimum intensity of the stimulus is reached, action potential is created with protein channels open, allowing for Na ions to diffuse in and K ions to diffuse out along the electrochemical gradient. The impulse is then self-propogated along the axon, as each section of the membrane reaches a threshold, causing the next area to begin reaching its threshold. The inside of the membrane becomes positive relative to the outside.
- Repolarization: In order to carry another signal and for Na to diffuse in, the initial potential must be restored. Immediately after action potential, K channels open and allow for K to diffuse out of the membrane. This leaves only Na inside the membrane and K outside. This is the perfect condition for Na/K pumps to begin active transportation, transporting Na out and K inside the axon membrane.
How does communication between two neurons occur?
The communication is chemical and occurs in the space between the two neurons called the synapse. The chemical, aka the neurotransmitter, is released by the synaptic terminal buttons of one neuron and is received by the dendrites of the other.
What are the neurons that receive and transmit signals to each other called?
The one that releases is called a presynaptic neuron and the one that receives it is called a postsynaptic neuron.
What are synaptic terminal buttons?
Small vesicles at the end of the axon carrying neurotransmitters. An example is acetylcholine.
Explain the release of neurotransmitters.
- Action potential arrives to the synaptic terminal button and causes Ca protein channels to open. Ca enters the terminal button.
- This initiates the binding of neurotransmitter vesicles to bind to the plasma membrane and release the neurotransmitter into the synaptic cleft.
- The neurotransmitter binds to a receptor protein on the membrane of the postsynaptic neuron. This initiates the action potential (depolarization) and the opening of Na protein channels for the movement of Na into the axon of the postsynaptic neuron.
- The neurotransmitter is degraded by specific enzymes and released by the receptor protein into the synaptic cleft.
- The leftover components are reassembled at the terminal button of the presynaptic neuron. This is called reuptake.
How to insecticides that block synaptic transmission work?
Neonicotinoid binds to the receptor protein on the postsynaptic neuron that usually binds to acetylcholine. This leads to the paralysis and eventual death of the insect. From an ecological standpoint, this may cause “colony collapse syndrome” in honeybees and is shown to have contributed greatly to the significant depletion of honeybee populations. International efforts are necessary, as insecticides can be carried by air and water.
What is the word that describes the minimum electric potential necessary to propogate an impulse?
- Threshold potential
- An action potential is either propogated or not, there’s no strong or weak impulses.
Which systems maintain homeostasis in our body?
The autonomous nervous system and the endocrine system. The endocrine system consists of numerous glands that produce hormones, which are transported by the bloodstream to specific cell types (target tissues) that are affected by them.
What are the two categories of glands?
- The two categories of glands are
- Exocrine glands: produce saliva and enzymes that are carried to a nearby location via a duct
- Endocrine glands: produce hormones that are carried by the bloodstream to the whole body.
- Hormone produced by the thyroid gland
- There are two types that are transported, namely T3 and T4 (this represents the number of iodine bonded to the amino acid). T4 is transformed into T3, which enters the nucleus.
- Thyroxin increases the amount of mRNA in the nucleus, and thus the rate in which protein is produced. (Thus, the metabolism)
- Regulates the rate of metabolism and BODY TEMPERATURE
- Produced by adipose (fat) tissue
- Target tissue is the hypothalamus of the brain
- Controls appetite (If there is enough fat in the body, more leptin is produced and thus appetite is less) This, however, is quesitonable, as obese people have high amounts of leptin in their bloodstream.
- Produced in the pineal gland in the brain
- Maintains the circadian rhythm
- Very little melatonin is produced during the day, and a maximum amount is reached at 2 am - 4 am
- Depends on exposure to light
Where and how is glucose stored?
Glucose is stored in the form of glycogen in muscles and the liver.
Explain Insulin and Glucagon
- The amount of glucose in the blood would fluctuate significantly in the absence of hormones. Insulin and Glucagon, as negative feedback systems, ensure that the blood glucose level is maintained at a level reasonable close to the body’s set point.
- The hepatic portal vein carries blood with glucose from the villi to the liver. All other blood vessels receive blood after it’s been treated by hepatocytes (cells in the liver). Hepatocytes are controlled by the antagonistic hormones insulin and glucagon.
- Released from the pancreas
- Insulin is produced by beta cells. It causes cells to open their protein channels, allowing for the facilitated diffusion of glucose into the cell. Insulin also initiates the process of the conversion of glucose into glycogen.
- Glucagon is produced by alpha cells. It triggers the hydrolysis of glycogen reserves in the body into glucose.
- Type 1 is caused by insufficient production of insulin as a result of the immune system attacking beta cells. It’s treated by insulin injections.
- Type 2 is caused by the cell receptors not being able to react to the insulin and open protein channels on their membranes. This is treated by changing diet.
- Released by testes
- Ensures the development of male genitalia during embryonic development.
- Ensures sexual development, male characteristics, sex drive and sperm production.
Part of male reproductive system. This is the male gonad. Sperm is produced here in small tubes called seminiferous tubes by Leydig cells.
Part of male reproductive system. This is where sperm mature and learn to swim using their flagella. (Right next to testis)
Explain Vas deferens
Part of male reproductive system. A muscular tube that transfers sperm from the epididymis to the seminal vesicle during ejaculation.
Explain seminal vesicles
Part of male reproductive system. Small glands that produce and add semen to the sperm.
Explain Prostate gland
Part of male reproductive system. Produces much of the seminal fluid, including carbohydrates for the sperm.
Part of the female reproductive system. Oestrogen is produced here. Corpus luteum (producing progesterone) is here. Secondary oocyte is produced and released here.
Explain Oviducts (Fallopian Tubes)
Part of the female reproductive system. Carries the ovum or the early embryo to the uterus.
Part of the female reproductive system. A muscular tissue where the embryo implants and develops.
Part of the female reproductive system. The highly vascular inner lining of the uterus.
Part of the female reproductive system. Allows for sperm to enter and childbirth.
How does a person become male or female during embryonic development?
Depending on the presence of two XX chromosomes or the Y chromosome, high amount of oestrogen + progesterone or testosterone takes place at the 8th week of pregnancy. The male and female reproductive systems have the same origin and are thus homologous.
Explain the Menstruation Cycle
- Hypothalamus releases GnRH which stimulates the pituitary gland to release FSH and LH
- Cause an increase in the amount of oestrogen released by the ovary, which increases the amount of FSH and LH released (positive feedback cycle).
- They also cause the randomly arranged follicles and oocytes to form the Graafian follicle.
- Oestrogen makes the endometrium highly vascular.
- At the maximum amount of LH and FSH released, the oocyte is released from the Graafian follicle. (ovulation).
- The remaining outer ring of the follicles turn into the corpus luteum to fill the “wound” left by ovulation. The corpus luteum releases progesterone.
- Progesterone maintains the highly vascular endometrium. The high amounts of oestrogen and progesterone serve as a negative feedback system for the hypothalamus and prevent more GnRH from releasing.
- If there is no pregnancy, the corpus luteum begins to break down after 10-12 days, resulting in the decrease of the amount of oestrogen and progesterone and menstruation.
- The female takes first takes hormone injections to suspend menstruation.
- Then, she takes hormone injections containing FSH for the production of many graafian follicles.
- The oocytes are then harvested surgically.
- Later on, the sperm and the oocytes are mixed and allowed to fertilize.
- After screening for genetic conditions, the fit zygotes are implanted into the uterus of the female.
Where does spermatogenesis occur? Why?
It occurs in the testes for the optimal temperature to be achieved. It occurs in the Leydig cells located in the seminiferous tubules.
What are the steps of spermatogenesis?
- Spermatogonium cells undergo mitosis to increase the number of spermatogonia cells available.
- When spermatogonium cells undergo meiosis, undifferentiated spermatozoa form.
- The spermatozoa mature and differentiate (flagellum etc.) in the presence of Sertoli cells, which provide them nutrients.
What are the differences between spermatogenesis and oogenesis?
- Polar bodies form as a result of oogenesis and there’s only one ovum. 4 spermatozoa form as a result of spermatogenesis.
- Spermatogenesis begins at puberty and lasts until death, oogenesis occurs once a month during menstruation.
- Ovum is very large, spermatozoa are very small
- Some cell growth occurs before spermatogenesis. A large amount of cell growth occurs before oogenesis.
What are the steps of oogenesis?
- Within the ovaries of the fetus, oogonia cells (2n) undergo mitosis.
- Oogonia mature to become oocytes (2n)
- Follicle cells undergo mitosis.
- Follicle cells surround oocytes to form primary follicle. The primary follicles remain unchanged until puberty is reached.
- After meiosis 1 is completed, the secondary oocyte and 1 polar body forms.
- Polar body degenerates.
- The remaining oocyte, along with follicle cells, forms the Graafian follicle.
- After the ovum is released, meiosis 2 only takes place if the ovum is fertilized.
- Oogonium to primary oocyte to secondary oocyte (Graafian follicle) to ovum
What is an acrosome?
Organelle with many lysosomes at the head of the sperm that helps the sperm enter the ovum.
What are the steps of fertilization?
- Millions of spermatozoa are released into the vagina
- Several of the spermatozoa reach the ovum in the fallopian tube and gain access to the zona pellucida, which they penetrate using the enzymes released by their acrosomes.
- One spermatozoon reaches the plasma membrane first and penetrates the egg using the acrosome.
- Cortical reaction takes place: cortical granules release chemicals that change the zona pellucida and make it impermeable for other spermatozoa.
What occurs after fertilization?
- Rapid mitosis results in the blastocyst.
- Blastocysts implants itself in the highly vascular endometrium.
- The trophoblast cell layer of the blastocyst forms the placenta, which provides the fetus with blood and allows for molecular exchanges to occur between the fetus and the mother.
- Embryo releases the hormone HCG which causes the mother to release high amounts of progesterone and oestrogen, which serve to maintain the highly vascular endometrium and prevent further ovum formation by serving as a negative feedback loop for LH and FSH.
What are the roles of progesterone during pregnancy?
- Maintains highly vascular endometrium by maintaining corpus luteum
- Suppresses contractions of the uterus
What are the roles of oestrogen during pregnancy?
- Encourages muscle growth of the uterus
- Eventually antagonizes progesterone to induce contractions
- Stimulates mammary gland development
- Induces production of oxytocin receptors in uterus
What is the role of oxytocin?
The hypothalamus stimulates the release of oxytocin from the pituitary gland. oxytocin receptors in the uterus will induce contractions. The contractions will signal the hypothalamus to stimulate the pituitary gland. This positive feedback loop is responsible for the steadily increasing contractions during birth.
What is the evolutionary advantage of exoskeletons?
They can maximize efficiency of movements by acting as levers. This gives rise to incredible strength and mobility. (such as grasshoppers or ants)
Why do muscles work in antagonistic pairs?
Each muscle can perform a single movement in a single direction. For mobility and back and forth movement, the muscles must work in pairs.
What are synovial joints?
These are bone to bone joints with synovial fluid in between. These allow limited movement like the opening and closing of a door. An example is the human elbow and the knee.
What are the main parts of a human elbow?
- Radius (top) and Ulna (bottom)
- Humerus (arm bone)
- Triceps (bottom) and Biceps (top)
- Synovial fluid
- Joint capsule
- Cartilage (at the end of bones)
What is the function of cartilage?
It is at the end of bones. It reduces friction and absorbs compression.
What is the function of synovial fluid?
Lubricates the ends of the bones to reduce friction and provides nutrients for cartilage cells.
What is the function of joint capsule?
Joins the two bones (humerus and radius + ulna). Encloses the synovial cavity,
What is the function of tendons?
Connects muscle to bone.
What is the function of ligaments?
Connects bone to bone.
What is the function of the biceps muscle?
Contracts to bring about flexion (bending) of arm.
What is the function of the triceps muscle?
Contracts to cause extension (straightening) of the arm.
What is the function of radius?
Acts as a lever for the biceps muscle.
What is the function of ulna?
Acts as a lever for the triceps muscle.
What are the three types of muscle?
Skeletal muscle, cardiac muscle and smooth muscle.
What is the sarcolemma?
The plasma membrane of muscle cells (fibres) is called sarcolemma. There are many nucleuses ver close to the sarcolemma. The sarcolemma has many tunnel-like extensions that penetrate the inside of the cell. These are called T tubules.
What is sarcoplasm?
This is the cytoplasm of a muscle cell (fibre). The sarcoplasm has a large number of mitochondria and glycogen. Here, there is also a special molecule very close to hemoglobin called myoglobin. Myoglobin stores oxygen and only releases it when hemoglobin is insufficient.
What is myofibril?
Very thin contractile fibrils that run the length of the cell. Each muscle cell has many myofibrils that run parallel and can contract in unison. Myofibrils are made of contractile units called sarcomeres with many mitochondria.
Explain the structure of muscle fibres (cells)
- They are multinucleate (fibres form from the fusion of individual muscle cells and hence have many nuclei)
- They have a large number of mitochondria (muscle contraction requires ATP hydrolysis)
- They have a specialised endoplasmic reticulum (it is called the sarcoplasmic reticulum and stores calcium ions)
- They contain tubular myofibrils made up of two different myofilaments – thin filament (actin) and thick filament (myosin)
- The continuous membrane surrounding the muscle fibre is called the sarcolemma and contains invaginations called T tubules
What are sarcomeres?
A myofibril is composed of many side by side contracting units called sarcomeres. Put very simple, muscle tissue is able to contract because each sacromere gets shorter.
What are sarcomeres composed of?
- Two proteins called actin (thin, is able to move towards the center and shorten the sarcomere) and myosin (thick with heads, doesn’t move)
- Z lines
- The varying thickness of action and myosin gives the sarcomere a striated pattern.
Explain the sliding head theory of muscle contraction
A motor neuron carries an action potential until it reaches the final synapse called the neuromuscular junction.
- The neurotransmitter acetylcholine is released into the synaptic gap between the synaptic terminal buttons the sarcolemma of the muscle fibre
- Acetylcholine binds to receptors on the sarcolemma.
- Sarcolemma Na channels open and Na diffuses into the muscle.
- The resulting action potential causes Ca channels on the sarcoplasmic reticulum to open.
- The released Ca ions flood into the sarcoplasm.
- On actin, the binding sites for myosin heads are covered by blocking complexes called troponin and tropomyosin. Ca ions bind to these complexes and reveal the binding sites.
- Myosin is activated by splitting ATP, which changes the position of myosin heads.
- The myosin heads then form cross bridges with actin and release one inorganic phosphate
- As the cross bridges are formed, the remaining ADP is also released, and the myosin flexes towards the center of the sarcomere due to loss in energy, bringing Z lines closer and shortening the sarcomere.
- Myosin binds to ATP, which leads to the detachment of myosin heads from actin.
- The process continues if ATP is available and Ca levels are high.
Why are troponin and tropomyosin important?
They represent the link between the nervous system and muscle contraction. Without an action potential from the motor neuron, troponin and tropomyosin remain bound to the myosin head binding sites on the actin.
How are nitrogenous waste products formed in the body?
The amine group NH2 is removed from excess amino acids and is used to form ammonia or urea.
What are the different kinds of nitrogenous wastes?
- Ammonia: produced by fish, requires very little energy to produce but is very toxic and requires a large amount of water to remove
- Urea: produced by mammals, requires more energy but is less toxic, still requires some water for removal
- Uric acid: produced by birds and reptiles, requires a lot of energy to produce, but can be removed without water in eggs.
How to insects remove nitrogenous waste products?
A selective reabsorption process occurs in the Malpighian tubules inside the body cavity of the insect. The remnants are removed in the form of feces.
What are the components of a kidney?
- Renal artery: Brings blood into the kidney, blood has more glucose, o2, urea, salt, water
- Renal vein: Takes blood from the kidney, blood has more co2
- Renal Pelvis: urine collects here
- Ureter: takes urine from the renal pelvis to the urinary bladder
- Renal medulla: membrane surrounding renal pelvis, contains nephrons
- Renal cortex: outside of kidney, contains nephrons
What are the structures of a nephron in order?
- Bowman’s capsule / glomerulus: blood is initially filtered to form filtrate, ultrafiltration occurs here
- Proximal convoluted tubule: selective reabsorption occurs
- Loop of henle: selectively permeable loop that descends into the medulla and forms a salt gradient, osmoregulation occurs
- Distal convoluted tubule: selective reabsorption occurs
- Collecting duct: the connection to the renal pelvis
How does blood leave and enter the nephron?
- Enters through afferent arteriole
- Leaves through efferent arteriole
- Occurs in the Bowman’s capsule
- Blood is brought to the glomerulus, a capillary bed with slits that open during high pressure, by the afferent arteriole.
- The afferent arteriole has a larger diameter than the efferent arteriole, which increases pressure inside the glomerulus.
- As pressure increases, blood leaves the glomerulus through the slits and is filtrated through the mesh called basement membrane to go into the proximal convoluted tubule.
- Everything that has not been filtrated (blood cells, proteins) leave the glomerulus through the efferent arteriole.
Explain Selective Reabsorption
- Occurs in the proximal convoluted tubule (majority here because it has microvilli) and the distal convoluted tubule.
- Salt ions and glucose are actively transported into the tubule cells, then they pass the intercellular fluid to reach the peritubular capillary bed. Water is transported alongside mineral ions through osmosis.
- Depending on the amount of water ingested, amount of perspiration and ventilation, different amounts of water enter and leave the body. For the body to maintain homeostasis, osmoregulation takes place the loops of henle.
- The portion of the loop of henle that descends into the medulla has two sides: one that is permeable to water but not to ions, and one that is permeable to salts but not to ions.
- Thus, after it’s descent is over, there is a high amount of ions in the intracellular fluid of the medulla.
- Much of the water remains, however, and the filtrate that reaches the collecting duct is still hypotonic.
- If ADH, produced by the hypothalamus and released by the pituitary gland if osmoregulators are simulated by high blood plasma concentration or low blood pressure, is available, the collecting duct becomes permeable to water and water moves into the medulla to be absorbed by the peritubular capillary bed.
Give an example of adaptation to desert areas.
The longer the loop of henle, the less dilute the urine is, thus conserving high amounts of water. The hormone ADH is also an adaptation to conserve more water.
What are osmoregulators and osmoconformers?
- Osmoregulators have different solute concentration in comparison to their environment. (Fish do active transport through their gills.)
- Osmoconformers have the same solute concentration and water moves in and out freely. (clams)
How do we deal with dysfunctioning kidneys?
- Haemodialysis: Blood is made to run through cellulose based tubing which is only permeable to urea. This must be done every 1-3 days.
- Kidney Transplant: Kidney must match the blood and tissue type and patient must take immuno-suppressors for the rest of their life. (Nothing is ever a perfect match!)
What are signs of kidney dysfunction?
- Presence of glucose indicates dysfunction in the proximal convoluted tubule and distal convoluted tube.
- Presence of blood cells or proteins indicates dysfunction in glomerulus.
What are the signs of dehydration?
- Dry mouth and skin
- Dizziness and headache
What are the signs of overhydration?
- Blurred vision
- Muscle cramps
- Nausea and vomiting