part 2 Flashcards
What is a processor?
A tissue or organ that coordinates the input from sensory receptors and communicates the output response to the relevant effector.
What is a Pacinian corpuscle?
A pressure sensor that detects changes in pressure or vibration in the skin.
Describe the structure of a Pacinian corpuscle?
The corpuscle is oval shaped with a series of rings of concentric connective tissue, wrapped around the end of a nerve cell.
How does a Pacinian corpuscle detect pressure changes?
The corpuscle is sensitive to changes in pressure that deform the rings of connective tissue. Therefore no response when the pressure is constant.
How are cell membrane proteins involved in neural communication?
Some proteins are channels allowing the movement of ions across the membranes by facilitated diffusion, while others are transport proteins that actively move ions across the membrane requiring energy in form of ATP.
What happens if a stimulus is too weak?
The generator potential will not reach the threshold level and so there is no action potential.
What is meant by the potential difference across a membrane?
The difference in potential between inside and outside the cell.
What is meant if a membrane is polarised?
The inside of the cell has a more negative potential than outside.
What is the resting potential value of a resting neurone?
-70mV
What 3 things maintain the resting potential of a resting neurone?
Presence of large organic anions inside the cell, 3 Na+ out, 2 K+ in by Na+/K+ pump, membrane is more permeable to K+.
Where has the highest concentration of Na+ at resting potential?
Outside the neurone.
Where is the highest concentration of K+ at resting potential?
Inside the cell.
Describe how a sodium/potassium pump in the cell membrane functions?
3 Sodium ions are actively pumped out of the cell, with 2 potassium ions going into the cell.
What is meant if a membrane depolarises?
The inside of the cell has a less negative potential than outside.
What causes a membrane to depolarise?
Some Na+ channels open, allowing Na+ to diffuse down its concentration gradient.
What happens in the neurone membrane if threshold potential is reached?
Voltage-gated Na+ channels open for bigger influx of Na+.
What is the action potential value of a stimulated neurone?
+40mV
What happens in the neurone membrane at +40mV?
Voltage-gated Na+ channels close, voltage-gated K+ channels open.
What is repolarisation?
Return of membrane potential difference to more negative inside the cell than outside.
What causes repolarisation?
Diffusion of K+ out of the cell down their concentration gradient.
What is hyperpolarisation?
Overshoot of membrane potential difference so that inside is more negative than outside than at resting potential.
What happens to the voltage-gated K+ channels in the neurone membrane at -70mV?
Voltage-gated K+ channels close.
What causes hyperpolarisation?
Voltage-gated K+ channels only close at -70mV so K+ continues to diffuse out of the cell.
What is the refractory period?
A short period of time after an action potential when it is impossible to stimulate the membrane into another action potential.
What are the 2 purposes of the refractory period?
To restore the resting potential Na+/K+ concentrations on either side of the membrane, ensure action potentials only transmit in one direction.
What is a local current in a neurone?
Diffusion of Na+ from point of entry to area of low concentration adjacent to the next region of membrane.
What is an electrochemical gradient?
A concentration gradient of ions.
What is saltatory conduction in a neurone?
Elongated local currents in myelinated neurones so that action potentials only occur at nodes of Ranvier.
How does changing the intensity of the stimulus affect the action potential?
Makes them more frequent.
What is a synapse?
A junction between 2 or more neurones.
What is a synaptic cleft?
A small gap between 2 neurones.
What is a neurotransmitter?
A chemical released from the pre-synaptic neurone that causes a new action potential in the post-synaptic neurone.
What are 4 examples of neurotransmitters?
Acetylcholine, adrenaline, dopamine, GABA.
Name one example of an excitatory neurotransmitter.
Acetylcholine.
Name one example of an inhibitory neurotransmitter.
GABA.
What is the difference between excitatory and inhibitory neurotransmitters?
Excitatory: causes depolarisation of postsynaptic neurone, causes action potential to be triggered; Inhibitory: causes hyperpolarisation of postsynaptic neurone, prevents action potential to be triggered.
What is a cholinergic synapse?
A synapse that uses acetylcholine as a neurotransmitter.
What are the 4 specialisations of the pre-synaptic bulb?
Many mitochondria, complex SER, many vesicles containing neurotransmitter, voltage-gated Ca2+ channels.
What is the specialisation of the post-synaptic membrane?
Neurotransmitter-gated Na+ channels.
What is acetylcholinesterase?
Enzyme that hydrolyses acetylcholine into acetic acid and choline.
What is the ‘all or nothing’ principle?
Each action potential is the same size and intensity.
What is an excitatory post-synaptic potential (EPSP)?
A small depolarisation in the post-synaptic neurone caused by a small number of neurotransmitter molecules being released from the pre-synaptic neurone.
What is summation?
The reaching of threshold potential in the post-synaptic neurone due to the combination of several EPSPs.
What is temporal summation?
The reaching of threshold potential in the post-synaptic neurone due to the combination of several EPSPs consecutively from the same pre-synaptic neurone.
What is spatial summation?
The reaching of threshold potential in the post-synaptic neurone due to the combination of several EPSPs from the several different pre-synaptic neurones.
What is an inhibitory post-synaptic potential (IPSP)?
A small hyperpolarisation in the post-synaptic neurone caused by a small number of neurotransmitter molecules being released from the pre-synaptic neurone.
What are the 2 structural divisions of the nervous system?
Central, peripheral.
What are the 2 organs of the central nervous system?
Brain, spinal cord.
What organ connects the central and peripheral nervous systems?
Spinal cord.
What are the 2 functional divisions of the nervous system?
Somatic, autonomic.
What is the function of the somatic nervous system?
Conduct action potentials to effectors that are under voluntary / conscious control.
What effectors are controlled by the somatic nervous system?
Skeletal muscles.
What is the function of the autonomic nervous system?
Conduct action potentials to effectors that are not under voluntary / conscious control.
What 3 effectors are controlled by the autonomic nervous system?
Smooth muscle, glands, cardiac muscle.
What are the 2 divisions of the autonomic nervous system?
Sympathetic, parasympathetic.
What is the function of the sympathetic nervous system?
Prepare the body for activity.
What is the function of the parasympathetic nervous system?
Conserve energy.
What are 3 effects of the sympathetic nervous system being more active than the parasympathetic nervous system?
Increased heart rate, increased ventilation rate, decreased digestion.
What are 3 effects of the parasympathetic nervous system being more active than the sympathetic nervous system?
Decreased heart rate, decreased ventilation rate, increased digestion.
What are 3 structural features of the sympathetic nervous system?
Ganglia close to CNS, 1:1 nerve:effector ratio, acetylcholine as neurotransmitter.
What are 3 structural features of the parasympathetic nervous system?
Ganglia close to effector, 1:many nerve:effector ratio, noradrenaline as neurotransmitter.
What are 4 main regions of the brain?
Cerebrum, cerebellum, hypothalamus / pituitary complex, medulla oblongata.
What is the function of the cerebrum?
Coordinates higher functions such as conscious thought & actions, emotions, speech and memory.
What is the function of the cerebellum?
Coordinates balance and fine movement control.
What is the function of the hypothalamus / pituitary complex?
Coordinates homeostatic mechanisms such as thermoregulation and osmoregulation.
What is the function of the medulla oblongata?
Coordinates physiological processes such as heart rate, blood pressure and ventilation rate.
What is a reflex action?
A response that requires no processing from the brain.
What are 2 examples of a reflex action?
Blinking, knee jerk.
What is a cranial reflex?
A reflex action with a nervous pathway through the brain.
What is a spinal reflex?
A reflex action with a nervous pathway through the spinal cord.
What does a corneal reflex do?
A reflex action with a nervous pathway through the brain, causing the eyelid to blink.
What part of the medulla oblongata controls heart rate?
Cardiovascular centre.
What are 2 stimuli that would lead to an increase in heart rate?
Muscle stretch, low blood pH.
What is a stimulus that would lead to a decrease in heart rate?
High blood pressure.
What are the 3 types of muscle?
Skeletal, smooth, cardiac.
What are 3 features used to identify smooth muscle?
Small, discrete cells, non-striated, longitudinal / circular layers.
What are 3 features used to identify cardiac muscle?
Long, branched fibres, striated, intercalated discs.
What is an intercalated disc?
Specialised cell surface membrane that allow action potentials to be easily conducted.
What are 3 features used to identify skeletal muscle?
Long, unbranched fibres, striated, multinucleate.
What is a sarcolemma?
Cell surface membrane of a muscle fibre.
What is a sarcoplasm?
Cytoplasm of a muscle fibre.
What is a sarcoplasmic reticulum?
Endoplasmic reticulum of a muscle fibre.
What is a myofibril?
The contractile units of skeletal muscle, containing two proteins; light and dark bands held together on the Z line.
What is the sarcomere?
The distance between the two Z lines, where the filaments are held together.
What happens when the muscle contracts?
Contraction of sarcomeres as the myosin and actin filaments slide over one another.
Describe the structure of the myosin filaments?
They have globular heads and are hinged so they can move back and forth, with a binding site for actin and a binding site for ATP.
Describe the structure of an actin filament?
They have binding sites for myosin heads, called actin-myosin binding sites.
Describe the sliding filament hypothesis of muscle contraction?
During contraction of the muscle the light band and H zone gets shorter so the Z lines move closer together and the sarcomere gets shorter.
What causes a muscle contraction?
The myosin heads attach to the actin and move causing the actin filament to slide past the myosin filament.
What does tropomyosin do in a resting muscle?
It blocks the actin-myosin binding site, so the myosin heads cannot bind to the actin for muscle contraction.
What triggers a muscle contraction in the sarcomere?
An action potential from a motor neurone triggers an influx of Calcium ions.
What is the function of Ca2+ ions in triggering a muscle contraction?
They bind to troponin, changing its shape pulling the attached tropomyosin out of the actin-myosin binding site.
How is an actin-myosin cross bridge formed?
It is formed when a myosin head binds to an actin filament.
How is ATP released to provide the energy for a muscle contraction?
Calcium ions activate the enzyme ATPase.
When ATP is hydrolysed in the sarcomere, what does it trigger?
Provides energy for the myosin head to return to its original position.
What is the endocrine system?
A communication system using hormones as signalling molecules.
What are the 2 types of hormone?
Steroid, non-steroid.
Name 3 examples of non-steroid hormones.
Adrenaline, insulin, glucagon.
Name 2 examples of steroid hormones.
Oestrogen, testosterone.
What are the 2 types of gland?
Endocrine, exocrine.
Where does an endocrine gland secrete into?
Blood.
Where does an exocrine gland secrete into?
Through ducts into organs or surface of body.
Name 3 examples of endocrine glands.
Pituitary, adrenal, pancreas.
Name 3 examples of exocrine glands.
Salivary, liver, pancreas.
What is a target cell of a hormone?
A cell in which the hormone causes an effect.
What do target cells of non-steroid hormones have?
Complementary receptors on their cell surface membrane.
What is a first messenger?
A non-steroid hormone.
What is a second messenger?
A signalling molecule that stimulates a change in a cell.
Name an example of a second messenger.
cAMP.
What are the 2 main regions of the adrenal gland?
Adrenal cortex, adrenal medulla.
What hormone is secreted from the adrenal medulla?
Adrenaline / noradrenaline.
What type of hormone is adrenaline?
Non-steroid.
Name 3 target cells of adrenaline.
Smooth muscle, cardiac muscle, hepatocyte.
Name 7 effects of adrenaline on the body.
Increased tidal volume, increased stroke volume, increased heart rate, vasoconstriction, pupil dilation, piloerection, inhibition of digestion.
What is the function of noradrenaline?
Works with adrenaline to respond to stress.
What type of hormones are secreted from the adrenal cortex?
Glucocorticoids, mineralocorticoids, androgens.
What is the function of mineralocorticoids?
Regulate the concentration of sodium and potassium ions in the blood (affecting blood pressure).
Name an example of a mineralocorticoid.
Aldosterone.
What is the function of glucocorticoids?
Regulate the metabolism of carbohydrates, lipids and proteins in the liver / regulate immune response and suppress inflammatory reactions.
Name an example of a glucocorticoid.
Cortisol / corticosterone.
What is the function of the androgens?
Regulate the production of gametes and development of secondary sexual characteristics.
Name 2 examples of androgens.
Oestrogen, testosterone.
What are the exocrine glands found in the pancreas?
Acini.
What is secreted by acini?
Digestive enzyme precursors.
What enzymes are found in the pancreatic duct?
Pancreatic amylase, trypsinogen and lipase.
What are the endocrine glands found in the pancreas?
Islets of Langerhans.
What 2 cells make up the islets of Langerhans?
Alpha, beta.
What hormone is secreted by the alpha cells of the islets of Langerhans?
Glucagon.
What hormone is secreted by the beta cells of the islets of Langerhans?
Insulin.
What range of blood glucose concentration is considered normal?
4-6 mmol dm-3 OR 90mg 100cm-3.
What are the endocrine glands found in the pancreas?
Islets of Langerhans
What 2 cells make up the islets of Langerhans?
Alpha, beta
What hormone is secreted by the alpha cells of the islets of Langerhans?
Glucagon
What hormone is secreted by the beta cells of the islets of Langerhans?
Insulin
What range of blood glucose concentration is considered normal?
4-6 mmol dm-3 OR 90mg 100cm-3
What hormone is secreted if blood glucose concentration is above normal?
Insulin
What hormone is secreted if blood glucose concentration is below normal?
Glucagon
What is the effect of insulin on blood glucose concentration?
Decrease
What is the effect of glucagon on blood glucose concentration?
Increase
What are the 2 target cells of insulin?
Hepatocytes, muscle cells
What 4 effects does insulin have on its target cells?
Glucose transporter proteins added to cell surface membrane, glycogenesis, glucose converted to lipids / proteins, increased rate of cellular respiration
How does insulin cause an effect on target cells?
Insulin binds to the glycoprotein receptor, which causes a conformational change in the glucose transport protein channels (part of a complex with the receptor); 2. Activates enzymes to convert glucose to glycogen and fat
What is glycogenesis?
Condensation of glucose molecules to form glycogen.
What is the target cell for glucagon?
Hepatocytes
What is the second messenger for glucagon?
cAMP
What 3 effects does glucagon have on its target cells?
Glycogenolysis, increased rate of fatty acid respiration, gluconeogenesis
What is glycogenolysis?
Hydrolysis of glycogen to produce glucose.
What is gluconeogenesis?
Conversion of amino acids and lipids into glucose.
What is meant by describing insulin and glucagon as antagonistic hormones?
They have opposite effects on blood glucose concentration.
How is negative feedback involved in the control of blood glucose levels in the blood?
The hormones are antagonistic, having the opposite effects on the blood glucose concentration. High glucose, insulin released to bring down the concentration, low glucose, glucagon release to increase concentration.
At normal blood glucose levels, how do beta cells stop releasing insulin?
Potassium channels of beta cells are open and K+ cells constantly diffuse out of cell to maintain a -70mV across the cell membrane.
How do beta cells detect a change in glucose level to release insulin?
At high BGL, glucose enters beta cells by glucose transporters, which is metabolised to make ATP –> ATP binds to potassium channels and closes them, stopping the diffusion of K+ ions out of cells, causing the membrane potential difference to drop to -30mV (depolarisation) –> voltage-gated calcium ion channels open, Ca2+ influx causes secretory vesicles to release insulin by exocytosis.
What two protein channels are involved in the release of insulin from beta cells?
ATP-sensitive potassium channels + voltage-gated calcium channels
What condition is caused by a long period below the normal blood glucose concentration?
Hypoglycaemia
What are the symptoms of mild hypoglycaemia?
Tiredness, irritability
What are the symptoms of extreme hypoglycaemia?
Seizures, unconsciousness, due to impairment of the brain activity
What condition is caused by a long period above the normal blood glucose concentration?
Hyperglycaemia
What is the symptom of hyperglycaemia?
Organ damage
Above what blood glucose concentration is considered a diagnosis for diabetes mellitus?
7 mmol dm-3
What is the cause of type 1 diabetes?
An autoimmune disease where the immune system destroys the beta cells of the pancreas.
What is the cause of type 2 diabetes?
Receptors on the surface of insulin target cells become less responsive to insulin.
What are the 5 risk factors of early onset of type 2 diabetes?
Obesity, lack of regular exercise, diet high in sugar, Asian / Afro-Caribbean origin, family history
What are the 5 possible treatments for type 1 diabetes?
Insulin injections, insulin pump, islet cell transplantation, pancreas transplant, stem cells
What is the main treatment for type 2 diabetes?
Regulate carbohydrate intake, increase exercise levels, take drugs that stimulate insulin production/slow down rate of glucose absorption
How is the insulin used to treat diabetes produced?
Escherichia coli bacteria that have undergone genetic modification.
What are the advantages of using insulin from genetically modified bacteria?
An exact copy of human insulin so more effective, less chance of developing tolerance, less chance of rejection due to immune response, lower risk of infection, easier to manufacture to demand and less moral objection to production in bacteria to animals
What is the ‘fight or flight’ response?
Detecting a threat to survival leading to physiological changes to prepare for a response
What is the survival value of pupils dilating?
Allows more light to enter the eyes making the retina more sensitive.
What is the survival value of increasing the blood glucose levels?
Energy supplied for muscular contraction
What is the survival value of increasing ventilation rate and depth?
Increases gaseous exchange so that oxygen enters the blood to supply aerobic respiration
What is the survival value to the heart rate and blood pressure increasing?
Increases the rate of blood flow to deliver more oxygen and glucose to the muscles and to remove carbon dioxide and other toxins
Where is the ‘fight or flight’ response coordinated?
Cerebrum
How is the ‘fight or flight’ response coordinated?
Receptor input to the sensory centres in the cerebrum, passing signals to associated centres and to the hypothalamus if a threat is detected.
What is the role of the hypothalamus in response to a threat?
Increases activity in the sympathetic nervous system and stimulated release of hormones from anterior pituitary gland
Name the hormone released by the hypothalamus to cause the release of ACTH in the pituitary gland.
Corticotropin-releasing hormone (CRH)
Name the hormone released by the pituitary gland to activate the adrenal cortex to release many hormones to deal with a threat.
Adrenocorticotropic hormone (ACTH)
What 2 effects result from the hypothalamus activating the sympathetic nervous system?
Impulses activate gland and smooth muscle and activate adrenal medulla secreting adrenaline
What happens next once adrenaline binds to the receptor on the cell surface?
Activates adenylyl cyclase to convert ATP to cAMP
What effects are caused on the cell by having more cAMP?
cAMP activates protein kinases to phosphorylate and activate other enzymes to bring about different effects (eg. convert glycogen into glucose)
What is the role of cAMP in the action of adrenaline on a cell?
Second messenger
What part of the medulla oblongata controls heart rate?
Cardiovascular centre
What sympathetic nerve increases heart rate?
Accelerator nerve
What parasympathetic nerve decreases heart rate?
Vagus nerve
Name the two types of receptors that detect stimuli to affect heart rate.
Baroreceptors (blood pressure) + chemoreceptor (chemical in blood)
What are 2 stimuli that would lead to an increase in heart rate?
Muscle stretch, low blood pH, low blood pressure
What is a stimulus that would lead to a decrease in heart rate?
High blood pressure
What neurotransmitter is released at the SAN to increase the heart rate?
Adrenaline / Noradrenaline
What neurotransmitter is released at the SAN to reduce the heart rate?
Acetylcholine
What effect could sensory input to the cardiovascular centre from stretch receptors in muscles?
Extra oxygen may be needed for movement increasing the heart rate
What do chemoreceptors in the carotid arteries and aorta do?
Monitor the pH of the blood
What is negative feedback?
A response that is opposite to the stimulus, returning conditions back to the optimum.
What is positive feedback?
A response that increases the stimulus, taking conditions further away from the optimum.
What is the difference between endotherms and ectotherms?
- Endotherms generate own heat by metabolic reactions
- Ectotherms rely on environment to control body temp
What is an ectotherm?
An organism that is unable to control its body temperature and is reliant on external sources of heat.
What is an endotherm?
An organism that controls its body temperature in a narrow range using physiological or behavioural adaptations.
What is an exergonic chemical reaction?
A chemical reaction that releases thermal energy.
Name 5 physiological responses in an endotherm to an increase in body temperature.
Sweating, pilorelaxation, vasodilation, reduced liver metabolism, panting
Name 4 physiological responses in an endotherm to a decrease in body temperature.
Piloerection, vasoconstriction, increased liver metabolism, shivering
What is vasodilation?
Relaxation of smooth muscle to widen arterioles and allow blood flow close to the skin’s surface.
What is vasoconstriction?
Contraction of smooth muscle to narrow arterioles and restrict blood flow close to the skin’s surface.
What is pilorelaxation?
Relaxation of the skin’s hair erector muscles so hair lies flat.
What is piloerection?
Contraction of the skin’s hair erector muscles so hair stands erect.
Name 4 behavioural responses in endotherms and ectotherms to an increase in body temperature.
Seek shade, reduce surface area, inactivity, wet skin
Name 4 behavioural responses in endotherms and ectotherms to a decrease in body temperature.
Seek sunlight, increase surface area, activity, keep dry
What are 3 advantages of being ectothermic that are disadvantages of being endothermic?
Ectotherms can: use less energy from food for respiration, use more energy from food for growth, survive long periods without food
What are 3 advantages of being endothermic that are disadvantages of being ectothermic?
Endotherms can: remain active in low temperatures, inhabit colder parts of the planet, maintain a constant internal temperature
What is excretion?
The removal of metabolic waste from the body.
Name 3 excretory products.
Carbon dioxide, urea, bile pigments
What are the 4 main excretory organs?
Lungs, liver, kidneys, skin
What is the effect on the blood of an increase in carbon dioxide concentration?
Decrease in pH.
What is the response to an increase in carbon dioxide concentration in the blood?
Increase in breathing rate.
What is the name for the basic functional unit of the liver?
Lobules
What is another name for liver cells?
Hepatocytes
What are the 4 vessels associated with the liver?
Hepatic vein, hepatic portal vein, hepatic artery, bile duct
Which liver vessel(s) is intra-lobular?
Hepatic vein
Which liver vessel(s) is inter-lobular?
Hepatic portal vein, hepatic artery, bile duct
What are the chambers in the lobules through which blood from the hepatic portal vein and hepatic artery pass?
Sinusoids
What are the chambers in the lobules through which bile is transported to the bile duct?
Canaliculi
What are the resident macrophages called in the liver?
Kupffer cells
What is the function of a Kupffer cell?
Break down and recycle old red blood cells.
Name three key functions of the liver.
- carbohydrate metabolism
- deamination of excess amino acids
- detoxification
What is deamination?
Removal of the amine group from an amino acid.
What is transamination?
Conversion of one amino acid into another
Why is transamination important?
To make essential amino acids that are not normally in our diet
What is the amine group converted into after deamination?
Ammonia (then urea)
Ammonia is converted to urea by ………………………
Ornithine cycle
What is the word equation for the ornithine cycle?
Ammonia + carbon dioxide → urea + water
Name two enzymes found in hepatocytes that are involved in detoxification.
Catalase; Alcohol dehydrogenase
Name the two products of the breakdown of hydrogen peroxide.
Oxygen and water
How is the liver involved in regulating blood glucose level?
Interacts with insulin and glucagon to convert between glucose and glycogen
Where is bile stored?
Gall bladder
What is the function of bile?
Emulsification - increases surface area for more lipase to work on –> speeds up lipid digestion
What are the two key functions of the kidneys?
Ultrafiltration + selective reabsorption
What structures of the kidneys are involved in ultrafiltration?
Glomerulus + Bowman’s capsule
What is the importance of selective reabsorption?
Get the useful substances back into the body
What are the 3 vessels associated with the kidney?
Renal artery, renal vein, ureter
What are the 3 regions of the kidney (from outside to inside)?
Cortex, medulla, pelvis
What are the kidney tubules called?
Nephrons
What are the 5 components of the nephron?
Bowman’s capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, collecting duct
What is the name for the knot of capillaries surrounded by the Bowman’s capsule?
Glomerulus
What arteriole enters the glomerulus?
Afferent
What arteriole exits the glomerulus?
Efferent
What is the difference in the structure of the afferent and efferent arterioles?
Afferent has a wider lumen / Efferent has a narrower lumen.
What is ultrafiltration?
The pushing of fluid out of the glomerulus into the Bowman’s capsule.
What are the 3 layers through which ultrafiltration occurs?
Endothelium of capillary, basement membrane, podocytes (epithelium of Bowman’s capsule)
What 5 substances are able to pass from the glomerulus into the Bowman’s capsule?
Water, amino acids, glucose, urea, mineral ions
What 2 substances are unable to pass from the glomerulus into the Bowman’s capsule?
Red / white blood cells, plasma proteins
Where does selective reabsorption mainly take place in the nephron?
Proximal convoluted tubule
What 4 substances are reabsorbed in the proximal convoluted tubule?
Glucose, amino acids, mineral ions, water, vitamins, hormones
What are the 5 specialisations of the PCT epithelial cells?
Microvilli on surface in contact with lumen, lumen membrane has many cotransporter proteins, highly folded membrane on surface in contact with capillaries, capillary-facing membrane has many Na+/K+ pumps, many mitochondria
What cotransport occurs in the PCT?
Glucose and Na+ from the lumen into the epithelial cells.
What are the 2 sections of the loop of Henle called?
Descending limb, ascending limb
What substance(s) enter the descending limb of the loop of Henle?
Mineral ions (Na+ and Cl-)
What substance(s) leave the descending limb of the loop of Henle?
Water
What substance(s) enter the ascending limb of the loop of Henle?
None
What substance(s) leave the ascending limb of the loop of Henle?
Mineral ions (Na+ and Cl-)
What happens to the water potential of the urine as it passes through the descending limb of the loop of Henle?
Decreases / becomes more negative
What happens to the water potential of the urine as it passes through the ascending limb of the loop of Henle?
Increases / becomes less negative
What happens to the water potential of the tissue fluid of the medulla towards the bottom of the loop of Henle?
Decreases / becomes more negative
What is the hairpin countercurrent multiplier effect in the loop of Henle?
The transfer of mineral ions from the ascending to descending limb creating a water potential gradient between urine and tissue fluid.
What is the hairpin countercurrent multiplier effect in the loop of Henle?
The transfer of mineral ions from the ascending to descending limb creating a water potential gradient between urine and tissue fluid at all points along the loop of Henle.
What is the importance of energy in the loop of Henle?
To do active transport to reabsorb Na+ and Cl- in the ascending limb
What occurs in the distal convoluted tubule?
Active transport of minerals out of the nephron to further increase the water potential.
What happens in the collecting duct?
Reabsorption of water, affected by ADH concentration
How does the body lose water?
Urine, sweat, exhaled air, faeces
What is osmoregulation?
Control of the blood water potential.
What is ADH?
Anti-diuretic hormone
What are the target cells of ADH?
Collecting duct epithelial cells
What is the effect of ADH on its target cells?
A cascade of enzyme-controlled reactions resulting in vesicles containing aquaporins fusing with the cell surface membrane.
What is an aquaporin?
Water permeable channel
Where are aquaporins found in cells lining the collecting duct that have not been affected by ADH?
In the membrane of vesicles.
Where are aquaporins found in cells lining the collecting duct that have been affected by ADH?
In the cell surface membrane.
What receptors detect changes in the water potential of the blood?
Osmoreceptors
Where are osmoreceptors found?
Hypothalamus
Where is ADH produced?
Hypothalamus
Where is ADH released?
Posterior pituitary gland
If water needs to be conserved, __________ ADH is secreted, __________ water is reabsorbed and __________ urine is produced.
More, more, less
If water does not need to be conserved, __________ ADH is secreted, __________ water is reabsorbed and __________ urine is produced.
Less, less, more
If a urine sample contains glucose, what may be a possible diagnosis about the patient?
High blood pressure / kidney failure (problem with selective reabsorption) / Diabetes
What is the glomerular filtration rate (GFR)?
A measure of the volume of fluid passing into the nephrons every minute.
What are the units used to measure GFR?
cm3 min-1
What is considered the normal range for GFR?
90-120 cm3 min-1
Below what GFR value is an indication of kidney disease?
60 cm3 min-1
What are 5 substances that can be detected in the urine?
Glucose, alcohol, recreational drugs, hCG, anabolic steroids
What hormone is detected using a pregnancy-testing kit?
Human chorionic gonadotrophin (hCG)
What are monoclonal antibodies?
Antibodies produced by clones of a single plasma cell, usually specific to a single epitope of an antigen.
What is the purpose of the control zone on a pregnancy-testing kit?
To determine if the kit is working.
What do monoclonal antibodies do in pregnancy testing?
Binds specifically to hCG and to the immobilised antibodies in the test window
Why should the pregnancy test be done early in the morning?
Highest concentration - as more water has been reabsorbed overnight, the urine should have the highest concentration of hCG in the morning
What methods are used to test for the presence of anabolic steroids in urine?
Mass spectrometry and gas chromatography
What is gas chromatography?
A separation technique used to determine the compounds in a liquid mixture based on their volatility.
Why is it necessary to do another test after immunoassay when testing for illegal drugs in urine?
To confirm the presence of the drug
What are the 2 most common treatments for kidney failure?
Renal dialysis, kidney transplant
What is renal dialysis?
Treatment used to artificially regulate the concentrations of solutes in the blood.
What are the 2 types of renal dialysis?
Haemodialysis, peritoneal dialysis
What is the membrane used in haemodialysis?
Artificial dialysis membrane
What is the membrane used in peritoneal dialysis?
Abdominal (peritoneal) membrane
How does the membrane used in haemodialysis determine what substances leave or stay in the blood?
The size of the gaps within the membrane
Which process in the kidneys does haemodialysis replace?
Ultrafiltration
How should the dialysis fluid be designed? What sort of chemicals and concentrations should be in it?
Should imitate concentrations of solutes in healthy blood/plasma
Why is it bad for the dialysis fluid to be pure water?
Lose useful substances due to steep concentration gradient (eg. glucose, vitamins, hormones)
What are the 4 main advantages of having a kidney transplant instead of renal dialysis?
Freedom from ongoing treatment, feeling physically fitter, better quality of life, improve self image
What are the 4 main disadvantages of having a kidney transplant instead of renal dialysis?
Regular doses of immunosuppressants, requires major surgery, possible rejection, side effects of immunosuppressants
State the difference between a tropic and a nastic response.
Tropic - directional; nastic - non-directional
Suggest why plant growth regulators are called hormones despite not being produced in endocrine glands.
Because, like animal hormones, they are chemical messengers that can be transported away from their site of manufacture to act on other parts of the plant. They also act on specific receptors
Explain why only certain tissues in a plant respond to a particular plant hormone.
Only the target tissues will have the necessary complementary-shaped receptors on their cell surface membranes to which the particular hormone molecule can bind.
State three functions of auxins.
Promotes cell elongation, prevents leaf fall (abscission), maintains apical dominance, inhibits ethene release
State three functions of cytokinins.
Promote cell division, delay leaf senescence, overcome apical dominance
State two functions of gibberellins.
Promote stem elongation, promote seed germination
State two functions of ethene.
Causes fruit ripening, promotes leaf abscission
State two functions of abscisic acid.
Inhibits seed germination (maintains dormancy), stimulate stomatal closure in times of water stress, stimulate production of antifreeze molecules in cold weather
Describe the synergistic action of auxin and gibberellin.
Auxin and gibberellin work together to promote stem elongation (gibberellins have a greater effect on this)
Describe the antagonistic action of auxin and ethene.
Auxin inhibits leaf abscission, ethene promotes leaf abscission
Describe the antagonistic action of gibberellin and abscisic acid.
Gibberellins promote seed germination, ABA inhibits seed germination
Describe the antagonistic action of auxin and cytokinin.
Auxin maintains apical dominance, cytokinin overcomes apical dominance
Describe how gibberellins stimulate seed germination.
Seed absorbs water activating gibberellin production; enzymes like amylase and protease produced to break down food stores; these food stores are respired to produce ATP for growth of a root and shoot
State a specific example of an auxin.
IAA
Describe how auxins promote cell elongation.
Auxins binds to cell surface receptors, causing influx of protons into cellulose cell wall. Drop in pH provides optimum pH for expansins to break crosslinks and H bonds between cellulose molecules, leading to lower pressure in CW. Water then moves into it to expand and stretch it. As auxins diffuse further down shoot, pH rises, denatures expansins, allowing crosslinks to reform. CW becomes rigid.
Describe the contributions of auxins, cytokinins and abscisic acid to apical dominance.
High auxin levels -> high abscisic acid levels -> low cytokinins in lateral buds -> lateral bud growth inhibited (apical dominance maintained) ORA
Explain how roots behave in response to particular levels of auxin.
Low auxin concentrations promote root growth; high concentrations of auxin inhibit root growth
Where does IAA accumulate when a plant is exposed to unilateral light?
The shaded side
What causes leaf loss in deciduous plants?
when the amount of glucose needed by the plant for respiration to maintain the leaves is less than the amount of glucose produced by photosynthesis
What is the term given to a plants’ sensitivity to a lack of light?
photoperiodism
What are the light-sensitive pigments that enables photoperiodism to happen?
phytochromes
What is the abscission?
Leaf fall
Describe the process of abscission.
Falling light levels result in falling conc. of auxin. Leaves respond by producing ethene. Ethene stimulates production of enzymes that digest and weaken cells at the base of the leaf stalk. vascular bundles are sealed off and a layer of fat is deposited. Cells in separation zone swell by retaining water. This strains weakened separation zone. Wind and low temps also help to separate leaf from plant.
How do plants avoid freezing?
solutes in cytoplasm reduce the freezing point. Some produce sugars, polysaccharides, amino acids and proteins to act as antifreeze
Why do plants need to prevent their cells from freezing?
their cell membranes would be ruptured and they would die.
What are the 2 main abiotic stresses that plants must adapt to?
Heat and water availability
