5.1 - Communication and Homeostasis

What is a response?

A behavioural or physiological change in an organism as a result of a stimulus.

What is a stimulus?

A change in the internal or external environment of an organism.

What is homeostasis?

Responses that maintain a constant internal environment inside an organism.

Name 4 internal conditions that are maintained by an organism's homeostasis.

Body temperature, blood glucose concentration, blood water potential, carbon dioxide concentration

Put the following aspects of a feedback mechanism in order: processor, stimulus, effector, response, receptor

stimulus, receptor, processor, effector, response

What are the 2 communication systems in mammals?

Nervous, hormonal

What is cell signalling?

The release of a chemical from a cell that is complementary to a receptor in a target cell, bringing about a response in the target cell.

What is an effector?

A cell or tissue that bring about a response to a stimulus.

What are the 3 types of effector?

Muscle cell, gland cells, liver cells

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?

-60mV

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 is the highest concentration of Na+ at resting potential?

Outside the cell

Name 3 types of neurone

motor, sensory and relay

Describe the structure and function of a motor neurone?

Their cell body is located in the CNS and they have a long axon carrying the action potential to the effector.

Describe the structure and function of a sensory neurone?

Have a long dendron carrying the action potential from a sensory receptorto the cell body, positioned outside the CNS. They have a short axon carrying the action potential into the CNS.

Describe the structure and function of a relay neurone?

They connect the sensory and motor neurones in the CNS. They have short dendrites and short axon

What is meant by a myelinated neurone?

The neurone is insulaterd by a myelin sheath, which is schwann cells wrapped tightly around the neurone.

Describe any advantages of myelination of neurones?

An action potential can be transmitted much quicker as the signal jumps between the nodes of Ranvier.

Where are non myelinated neurones found?

They are often used to coordinate body functions such as breathing or digestion, carrying action potentials over shorter distances.

What is a sensory receptor?

A cell or tissue that monitors an aspect of an organism's internal or external environment.

What do sensory neurones do?

They convert the energy of a stimulus into electrical energy.

Name 6 examples of sensory receptors.

Thermo, chemo, baro, photo, proprio, osmo

Sensory neurones act as a tranducer. What is a tranducer?

Something that converts one form of energy into another.

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 conective 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 tat 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

Where is the highest concentration of K+ at resting potential?

Inside the cell

Describe how a sodium/potassium pump in the cell menbrane 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?

#ERROR!

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 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 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 type of neurones is the brain mostly composed from?

Relay

What are the 2 divisions of the peripheral nervous system?

Sensory, motor

What are the 2 divisions of the motor 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 are 2 structural features of the somatic nervous system?

Mostly myelinated neurones, single neurone connects CNS to effector

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 are 3 structural features of the autonomic nervous system?

Mostly non-myelinated neurones, at least 2 neurones connects CNS to effector, connections between neurones called ganglia

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 part of the brain connects the 2 cerebral hemispheres?

Corpus callosum

What are the 4 lobes of the cerebrum?

Frontal, parietal, temporal, occipital

What are the 3 areas found in each lobe of the cerebrum?

Sensory, association, motor

What is the function of the cerebellum?

Coordinates balance and fine movement control.

What part of the brain connects the cerebellum to the cerebrum?

Pons

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/spinal/cramial/corneal

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 sympathetic nerve increases heart rate?

Accelerans

What parasympathetic nerve decreases heart rate?

Vagus

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 anf 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 sacromeres as the myosin and actin filaments slide over on another.

Decribe 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 a 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 sacromere 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 tropomysin 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 sacromere?

An action potential from a motor neurone tiggers an influx of Calcium ions.

What is the function of Ca ions in triggereing a muscle contraction?

They bind to troponin, changing it's shape pulling the attached tropomycin 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 sacromere, 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, (thyroid, ovaries, testes)

Name 3 examples of exocrine glands.

Salivary, liver, pancreas, (stomach)

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 (sex hormones)

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, trpsinogen 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 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 affect 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 fedback 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, inslin released to bring down the concentration, low glucose, glycogen 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 responce

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 'flight or fight' 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 respose to a threat?

Increases activity in the sympathetic nervous system and stimulated release of hormones form 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 cortext to release many hormones to deal with a threat.

Adrenocorticotropic hormone (ACTH)

What 2 effects result from the hypothalmus activating the sympathetic nervous system?

Impulses activate gland and smooth muscle and activate adrenal medulla secreteing 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 cardivascular 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 relies 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 an 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 an 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 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 sepctrometry 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 (giberellins 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.

1.) Auxin molecules are produced at the tip and diffuse down the shoot; 2.) Auxin binds to specific receptors on cell surface membranes; 3.) Protons actively pumped into cellulose cell walls; pH falls to about 5 in cell wall providing an optimum pH for expansins; 4.) Expansins break cross links and hydrogen bonds between cellulose molecules; 5.) Lower pressure in cell wall compared to cell means water moves into cell wall and it expands and stretches; 5.) as hormone levels fall further down the shoot, pH rises and expansins denatured; 6.) cellulose cross linking can now occur and cell wall 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)…low auxin levels (if shoot tip removed) --> low abscisic acid levels --> higher cytokinin levels in lateral buds --> lateral bud growth occurs (apical dominance overcome)

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

What effect does stomatal opening have on heat stress on a plant?

It cools the plant/ reduces the temperature. Water leaves the stomata and evaporates, reducing the temperature of the plant.

What effect does ABA have on the stomata?

ABA (from leaf and root cells) causes stomatal closing by activating changes in ionic conc of guard cells, reducing water potential and turgor of cells and closing stomata

State three chemical defences against herbivory (attack by insects).

Tannins, alkaloids, Terpenoids

State three physical defences against herbivory.

thorns, barbs, spikes, spiny leaves, fibrous and inedible tissue, hairy leaves, stings

How do tannins prevent herbivory?

bitter taste to deter animals and toxic to insects (inactivate digestive enzymes in insect saliva)

How do alkaloids prevent herbivory?

bitter tasting and sometimes poisonous

How do tannins prevent herbivory?

toxins to insects and fungi

What is the name for a chemical made by an organism which affects the behaviour of other members of the same species?

Pheromones

Plants do not have pheromones, what do they have instead?

Volatile Organic Chemicals (VOCs). produced by plants, which act between themselves and other organisms

Give an example of a plant that produces a VOC and describe its' action.

Cabbages, under attack from cabbage white butterfly caterpillars, produce VOC's to attract the wasp cotesia glomerata. wasp lays eggs in caterpillars eggs, killing them. The VOC's deter the femal cwb from laying more eggs on the plant. Apple trees, when attacked by spider mites, produce VOC's to attract predators of the mites. Wheat produces VOC's, when attacked by aphids, to deter other aphids

How does the plant, mimosa pudica protect itself against herbivory?

contains alkaloids and stem has sharp prickles, but if leaves are touched, they fold down and collapse. dislodges insects and scares off larger animals. Caused by movement of potassium ions and changes in water potential of the cells.

Describe the functions of positive phototropism and positive geotropism.

Positive phototropism - plant shoots grow towards light which enables them to carry out the light dependent reaction of photosynthesis. Positive geotropism - roots grow downwards into the soil, giving them anchorage and enabling them to obtain water and mineral ions

What will happen if a shoot is grown in light, shining from one side?

It will grow towards the light/ positive phototropism

If a shoot is exposed to light from one side, where will auxin be found within the shoot?

There will be less auxin on the light side and a greater concentration of auxin on the shady side. Auxin migrates laterally away from the light.

What effect does auxin have on the cells in a shoot?

it causes cell elongation and growth on the dark side so the shoot bends away from the shaded side and towards the light

What is etiolation?

When plants are grown in the dark or partial darkness, producing rapid growth upwards. plants are tall, thin and pale.

Which hormones cause longer internodes in plants grown in the dark?

Gibberellins

What slow-rotating piece of equipment can be used to demonstrate geotropism in the lab?

Clinostat

What would you expect to observe if germinating beans are grown on a clinostat over a a few days?

The roots will curl as they try to grown 'downwards'

What would you expect to observe if a potted plant shoot is grown on a clinostat over a a few days?

The shoot will grow horizontally outwards from the pot.

Which plant hormone is involved in fruit ripening?

Ethene

Which plant hormone is involved in encouraging root growth?

Auxins

Which plant hormone(s) is/are involved in delaying senescence?

In leaves - cytokinins; in citrus fruits - gibberellins

Which plant hormone is involved in preventing the ageing of ripened fruit?

Cytokinins

What hormone is used in rooting powder?

Auxin

What are climacteric fruits?

Fruits that continue to ripen after harvesting e.g. bananas, avocados, tomatoes, mangoes

Why are climacteric fruits harvested before they are ripe?

The unripe fruit is hard and much less easily damaged during transport than the ripe fruit.

How are auxins used as weedkillers?

they cause rapid and unsustainable growth in the dicot weeds so they die