human physiology

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miranda leung

Cards (43)

The mechanisms by which the products of digestion are absorbed include:
Diffusion
Facilitated diffusion
Active transport
Exocytosis
Peristalsis ensures one way movement of food through the alimentary canal in the following way:
A series of muscle contractions creates a wavelike movement through the alimentary canal
Circular muscles contract behind the food substance to prevent the food moving backwards
Longitudinal muscles contract / reduce in length to force food forwards (through the alimentary canal)
Compare and contrast endopeptidases and exopeptidases:
Similarities:
Both are produced by the pancreas/ found in pancreatic juice
Both hydrolyse peptide bonds
Both act in the small intestine
Both produce dipeptides (which can then be broken down further by dipeptidases)
Differences:
Endopeptidases hydrolyse peptide bonds in the middle of the polypeptide; exopeptidases hydrolyse peptide bonds at the end of the polypeptide
The small intestines are adapted to maximise absorption in the following ways:
(Epithelium is highly folded and has microvilli gives) a large surface area (for absorption)
There is a good blood supply and many lacteals - maintain a concentration gradient by removing nutrients as they are absorbed
The epithelium of the small intestine is only one cell thick - minimises the diffusion distance
Many enzymes are present in the small intestine to break down larger molecules into small molecules that can be absorbed
Peristalsis ensures food is mixed up with enzymes
Similarities of the process of peristalsis in the oesophagus and small intestine:
Both involve the action of longitudinal AND circular muscle
In both cases, the muscle contraction is controlled by the enteric/autonomic nervous system / is outside conscious control
In both cases the muscle contraction forces the contents of the alimentary canal to move forward / in one direction only
The food is lubricated by / moves smoothly because of mucus in both locations
Differences of the process of peristalsis in the oesophagus and small intestine:
Peristalsis in the oesophagus will move the food/bolus quickly (towards the stomach); in the small intestine the movement of food/chyme is slow
The food bolus in the oesophagus is more solid / less liquid than the food/chyme in the small intestine
Peristalsis in the small intestine will churn food and mix it with digestive enzymes to increase the rate of / aid digestion; in the oesophagus peristalsis is not involved with digestion
Lipid absorption:
Monoglycerides can enter epithelial cells by simple diffusion AS they are non-polar
Fatty acids can move by facilitated diffusion through fatty acid transport proteins
Inside the epithelial cells, fatty acids recombine with monoglycerides/glycerol AND form triglycerides
Triglycerides are unable to diffuse back into the lumen of the small intestine
Triglycerides are packaged with cholesterol
Encased/coated in / surrounded by phospholipids AND proteins making lipoproteins
(Lipoproteins) leave the epithelial cells by exocytosis and enter the lacteals
The roles of pancreatic juice include...
Amylase that (partially) digests starch into maltose
Lipase that breaks down triglycerides into fatty acids and glycerol/monoglycerides
Phospholipase that breaks down phospholipids into fatty acids, glycerol, and phosphate
Protease that (partially) digests proteins/polypeptides into shorter (poly)peptides
The structure of capillaries enable them to function efficiently as exchange surfaces because:
Permeable wall / gaps between the cells making up the capillary wall SO allowing exchange of materials / named material
Thin walls / walls one cell thick SO short diffusion pathway/distance
Narrow/small diameter SO can pass right next to cells in the tissues (reducing diffusion distance)
Narrow/small lumen which reduces blood flow rate which allows more time for diffusion
Heart rate increases during exercise because:
The rate of respiration increases in muscle cells (during exercise)
The carbon dioxide concentration in the blood increases
Changes in the blood are detected by (chemo)receptors (in blood vessel walls)
Impulses are sent to the medulla/acceleratory centre/cardiovascular centre
Acceleratory centre sends impulses to the sinoatrial node/SA node via a nerve (causing the heart rate to increase)
Controlled by the autonomic nervous system
SAN is also stimulated by adrenaline/epinephrine
Blood returns to the heart from the legs by:
Skeletal muscle contraction (e.g. in the legs) helps blood flow / pushes blood through the veins
Veins have valves that prevent backflow of blood OR valves in veins ensure blood flows in one direction
Blood that does flow backwards gets caught in the valves/valve flaps
Blood caught in the valves/valve flaps is pushed forward again by the next muscular contraction
Wide lumen (in the veins) results in little resistance / low friction
William Harvey's theory on circulation:
Blood is pumped to the brain and body by the heart OR the heart acts as a pump to circulate blood around the entire body
The circulatory system is a double system OR blood moves through a (separate) pulmonary/lung and systemic/body circuit
Capillaries link arteries to veins
Blood returns to the heart and recirculates OR blood is not used up by the tissues
Blood flow is unidirectional
Valves in veins prevent backflow of blood
The SA node can be considered the pacemaker of the heart because....
The cardiac cycle / heart beat is controlled by electrical signals initiated by the SA node
The cells of SA node depolarise which triggers a wave of depolarisation that spreads across the rest of the heart
The SA node also controls the speed at which the heart beats / heart rate
The pressure changes during cardiac cycle:
Diastole (relaxing), blood flows into the atria from the veins; increases atrial pressure
AV valves open
Pressure in the pulmonary artery and aorta > ventricles; closes the semilunar valves
Systole (contracting), it increases the pressure due to reduced volume
AV valves open
Pressure in the ventricles < pulmonary artery and aorta; semilunar valves are closed
In ventricular systole, the pressure in the ventricles > atria closing the AV valves
Pressure in the ventricles > pulmonary artery and aorta; semilunar valves are open
Blood clotting:
Platelets release clotting factors
Clotting factors stimulate the release the enzyme thrombin
Thrombin catalyses the conversion of fibrinogen to fibrin
Fibrin forms a mesh that traps platelets and blood cells preventing entry of bacteria /microorganisms through the wound
The mesh hardens when in contact with the air OR the blood clot hardens to form a scab
Mucous membranes form a primary defence against pathogens in the following ways:
(Mucous membranes) produce mucus OR secrete glycoproteins (as a physical barrier)
Mucus traps pathogens and harmful particles
Mucus has antiseptic properties because of the presence of the anti-bacterial enzyme lysozyme OR enzymes/lysozymes present in mucus can break down/digest bacteria
Cilia (present in some mucous membranes) remove/sweep away the mucus so it can be swallowed or expelled
Antibodies are a protein produced by lymphocytes in response to an antigen
Antigens are proteins (and chemicals) produced by/on the surface of a pathogen OR any protein/chemical/substance that stimulates/triggers an immune response
The effect of HIV on the immune system:
Loss of the capacity to produce antibodies
(Because) HIV causes a reduction in the number of active lymphocytes (which produce antibodies) OR HIV attacks/destroys helper T-cells (which produce antibodies)
Phagocytosis:
A phagocyte is attracted by a substance/chemical/antigen OR a phagocyte recognises (foreign) antigen
The virus is engulfed by endocytosis
(The vacuole/vesicle/phagosome) fuses/joins with lysosome
Lysosomes (within the phagocyte/cytoplasm) contain enzymes
The virus is digested OR molecules hydrolysed by the enzymes
A retrovirus is:
(A virus) that contains genes made of RNA instead of DNA
(A virus that) makes a DNA copy of the viral RNA
(Uses) reverse transcriptase
HIV is a retrovirus. This means it carries RNA as its genetic material. Retroviruses also contain the enzyme reverse transcriptase, which allows it to copy RNA into DNA and use that DNA ‘copy’ to infect human (host) cells. When HIV infects a cell, it first attaches to and fuses with the host cell. The viral RNA is then converted into DNA during a process known as reverse transcription. HIV then uses the host cell’s ‘machinery’ to replicate itself. The new copies of HIV then leave the host cell and move on to infect other cells.
Florey and Chain’s experimental method:
Grew fungus Penicillium in liquid culture conditions
Penicillium/fungus stimulated to secrete penicillin
Method developed to purify and concentrate penicillin from the cultures
Tested the effectiveness of the penicillin on bacteria on agar plates
Infected (eight) mice with with (pathogenic) Streptococcus bacteria
Gave half the mice (four of the eight mice) penicillin, (remaining mice untreated)
Mice treated with penicillin survived/untreated mice died
Risks involved in Florey and Chain’s experiments included:
Only eight mice used in the sample OR very small sample size used during animal testing
Human trials began with limited quantities of penicillin/antibiotic OR supplies were insufficient so some patients could not complete a full course of penicillin OR some patients relapsed as penicillin ran out during treatment
Antibiotic/penicillin released after experiments on sample size of only five humans OR very small sample size used during human testing
Whole study lasted only months
Similarities of the role of phagocytes and lymphocytes in the immune system:
Both are types of white blood cells (produced in bone marrow)
They provide the next line of defence against pathogens that crossed the physical barriers of the body OR they are both involved with fighting against pathogens that entered the skin/mucous membranes
Differences of the role of phagocytes and lymphocytes in the immune system:
Phagocytes are responsible for a non-specific immune response; lymphocytes are involved with a specific immune response (in response to a specific antigen)
Phagocytes engulf pathogens via endocytosis; lymphocytes produce antibodies to fight pathogens
Once engulfed by phagocytes, pathogens are digested by enzymes in lysosomes; antibodies will fight pathogens in a variety of ways e.g. labelling them for phagocytes , preventing viruses from binding to host receptors etc.
The development of antibiotic resistance in bacteria can:
Random mutations may result in bacteria that are resistant to an antibiotic and survives
There is less competition present for resources since the non-resistant bacteria were killed by the antibiotic
They reproduce and pass the allele for resistance on to next generation (increase frequency); same generation via conjugation
Antibiotic resistance will increase the survival chances of bacteria that possess the allele
Entire bacterial population will be resistant to the antibiotic (natural selection)
Explain how the fluid secreted by epithelial cells of the alveolus helps to reduce surface tension and prevent adhesion of the alveolar surface.
(Fluid) contains pulmonary surfactant
(Fluid) has molecules of hydrophobic tails and hydrophilic heads (accept labeled diagram)
Monolayer formed on the surface of the alveoli
Hydrophobic tails (of the monolayer) face the alveolar air space
Hydrophilic heads (of the monolayer) face the water
Monolayer prevents water from adhering the alveolar sides together (during exhalation)
The volume of the thorax increases during inspiration as…
The diaphragm contracts and flattens
External intercostal muscles contract to move the rib cage upwards and outwards
Adaptations of the alveoli:
alveolar epithelium is one cell thick - reduces diffusion distance
large number of alveoli - increases surface area
extensive network of capillaries - short diffusion pathway to help maintain concentration gradient
pulmonary surfactant - reduces surface tension/prevents alveoli walls collapsing/evaporation of carbon dioxide
Antagonistic muscle action during ventilation…
(During inspiration) diaphragm contracts whereas the abdomen muscles relax
(During expiration) diaphragm relaxes whereas the abdomen muscles contract
(During inspiration) external intercostal muscles contract whereas the internal intercostal muscles relax
(During expiration) external intercostal muscles relax whereas the internal intercostal muscles contract
Smoking can increase symptoms of emphysema because:
(In smokers) goblet cells (in the alveoli epithelium) secrete more mucus
Mucus destroys the cilia cells lining the trachea
(Therefore) cilia cells cannot trap bacteria and other pathogens
(Leads to) increase of phagocytes that release elastase enzyme
Elastase breaks down proteins in alveolar cells
(This causes) alveolar walls break down decreasing the surface area to volume ratio
(This causes) emphysema where oxygen is not efficiently diffused into the blood
Factors affecting risk of lung cancer:
second hand smoking
air pollution
radon gas
asbestos/silica
genetics/hereditary factors
A ventilation system is needed in mammals because...
Ventilation/breathing maintains oxygen/carbon dioxide concentration gradient between the alveoli and the blood / keeps the concentration of oxygen in the alveoli higher than in the blood / keeps the concentration of carbon dioxide in the alveoli lower than in the blood
A large surface area is needed for gas exchange / the surface area of the skin is not large enough to supply the oxygen requirements/needs (of mammals)
Aerobic respiration needs oxygen AND produces carbon dioxide (which needs to be removed from the body)
The lungs are adapted for gas exchange as follows...
The trachea/bronchi contain rings of cartilage to prevent them from collapsing / keep the airways open
The airways are lined with smooth muscle to regulate airflow into the lungs
The alveoli provide a large surface area to increase the rate of diffusion
Ventilation/capillary network supply maintains concentration gradient
Type I pneumocytes so the diffusion distance is short; Type II secrete a surfactant that prevents alveoli from collapsing/sticking together/reduces surface tension
Oxygen dissolves in the fluid lining the alveoli
Myelin can speed up a nerve impulse because…
(In myelinated nerve fibres) Schwann cells deposit a phospholipid bilayer/myelin
Nodes of Ranvier exist between the Schwann cells/myelin
(In myelinated nerve fibres) the nerve impulse can jump from one node of Ranvier to the next
Called saltatory conduction
At a synapse information can pass across because…
An impulse arrives (at the end of the presynaptic neurone) which causes Ca2+ to enter the axon
Vesicles move to/fuse with the presynaptic membrane
(As a result) acetylcholine is released, diffuses across the synaptic cleft/synapse
And binds with the receptors on the postsynaptic neurone
Depolarisation of the postsynaptic membrane occurs
If the impulse reaches above the threshold an action potential will be produced
Local currents are generated by…
Diffusion of sodium ions into the axon (through sodium channels)
(Leads to) depolarisation of that part of the axon
(There is now a) lower concentration of sodium ions outside the axon AND greater concentration of sodium ions inside the axon
Inside the axon sodium ions diffuse to the neighbouring polarised region
Outside the axon sodium ions diffuse back towards the depolarised region
(This is a) local current causes regions/wave of depolarisation and repolarisation (which propagates the nerve impulse
Active immunity involves the production of antibodies by the body itself and the subsequent development of memory cells.
Passive immunity results from the acquisition of antibodies from another source and hence memory cells are not developed
Active immunity will result in long-term immunity but passive immunity will not (due to the absence of memory cells).
When the body is challenged by a foreign pathogen it will respond with both a non-specific and a specific immune reaction
Non-specific immune cells called macrophages will engulf pathogens non-selectively and break them down internally
A proportion of macrophages (dendritic cells) will present the antigenic fragments of the pathogen to specific lymphocytes
The body contains millions of different T lymphocytes and B lymphocytes that each recognise a single, specific antigen
Antigenic fragments are presented to specific helper T lymphocytes (TH cells) that, when activated, releases cytokines
The cytokines stimulate a specific B cell that produces antibodies to the antigen to divide and form clones (clonal selection)
Most of the clones will develop into short-lived plasma cells that produce large quantities of specific antibody
A small proportion of clones will differentiate into long-lived memory cells that function to provide long-term immunity