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87 Cards in this Set

  • Front
  • Back

Define stimulus

Any change in environment that causes a response

Define response

A change in behaviour or physiology as a result of a change in environment

What are the features of a good communication system?

-Whole body is included

-Specific response

-Rapid response

-Short term and long term responses

What are the features of the hormonal communication system?


-Travels in blood

-Chemical message

-Longer lasting response

What are the features of the nervous communication system?


-Travels in nerves and neurones

-Electrical message

-Shorter response

Define negative feedback

The reversal of a change in the internal environment, to return to a steady state

Define positive feedback

The process that increases any change detected by the receptors- tending to be harmful

Define homeostasis

The maintenance of the internal environment in a constant state despite external changes

Give an example of where and how negative feedback is used

Body temperature- shivering when temp. is too low to increase temp., sweating when temp. is to high to reduce temp.

Give an example of where and how positive feedback is used

Body temperature- enzymes stop working at low temperatures, so less energy is released by their action, which decreases the temperature even further, causing hypothermia

What body conditions are controlled by homeostasis?

-Blood temperature

-Blood glucose concentration

-Blood salt concentration

-Water potential of the blood

-Blood pressure

-Carbon dioxide concentration

Describe the negative feedback loop

Optimum conditions> Change from optimum conditions> Receptor detects the change> Communication system informs effector> Effector reacts to reverse the change> Return to optimum conditions

Describe the positive feedback loop

Optimum conditions> Change from optimum conditions> Receptor detects the change> Communication system informs effector> Effector reacts to increase the change> Receptor detects the change...

What is the function of a motor neurone?

Carry the action potential from the CNS to an effector

What is the function of a sensory neurone?

Carry the action potential from a sensory receptor to the CNS

what is the difference between motor and sensory neurones ?

motor neorones

- cell body found in the CNS

-Long axon, no dendron but there are dendrites on cell body

sensory neourones

- cell body just outside the CNS

-Short axon, long dendron

What causes the cell membrane to be polarised at resting potential?

-Sodium/potassium pump actively pumps 3 NA+ for every 2 K+ in

Anions in cytoplasm

Some K+ channels are open so K+ diffuse out

What causes the initial depolarisation of the membrane in the propagation of an action potential?

A stimulus causes an energy change which causes the sodium ion channels to open, so sodium ions diffuse into the cell

What is an initial depolarisation of the membrane in the propogation of an action potential called?

Generator potential

Describe what happens at threshold potential in the generation of a nerve impulse

When -50mv is reached, voltage gated Na+ channels open, and Na+ ions diffuse in rapidly down a concentration gradient

Describe how local currents are set up and how an action potential is passed along a neurone

1. Na+ channels open and Na+ ions diffuse in down concentration gradient

2. Na+ concentration increases at site of channel

3. Na+ diffuses sideways along axon due to concentration gradient

4. Creates a local current

5. Voltage gated ion channels further along the axon open

6. Na+ ions enter neurone down a concentration gradient

7. New action potential is achieved further down the axon

What is a local current?

Movement of charged ions

What happens at repolarisation step in the generation of a nerve impulse?

Na+ channels close and K+ channels open, K+ diffuses out down concentration gradient

The potential difference inside the neurone is returned to negative

What happens at the hyperpolarisation step in the generation of a nerve impulse?

Potential difference overshoots slightly making inside more negative than before- this ensures no action potential is possible so it only moves forwards. Called the refractory period.

Potential difference is then restored by the Na+/K+ pump

What is saltatory conduction?

The way in which an action potential appears to jump from node to node because they can only be generated at the nodes of ranvier

What are olfactory cells?

Cells that detect chemicals, found in the nasal cavity

What are proprioceptors?

Muscle spindles which give you an awareness of your body and give you a sense of which muscles are contracting at any time

What's the difference between myelinated and non-myelinated neurones?

Myelinated neurones have Schwann cells wrapped around the neurone, which insulate it and increase the speed of conduction.

outline the roles of synapse

>ensures movement of , impulse / action potential , in one direction (only)

>integration or one neurone can transmit impulses to many neurones


> filters out , ‘background’ / low level , stimuli

> acclimatisation

>prevents continuous stimulation of neurones > permits , memory / learning and conscious thought

Describe what happens in a presynaptic neurone to cause acetylcholine to be released

-Action potential arrives at the neurone

-Voltage gated calcium (Ca+) ion channels open

-Ca+ diffuses into presynaptic neurone

-Ca+ ions cause synaptic vesicles of acetylcholine to fuse with with presynaptic membrane

-Acetylcholine is released by exocytosis

Describe how acetylcholine causes an action potential to be produced in a postsynaptic neurone

-Acetylcholine binds to receptors on postsynaptic membrane which are situated on sodium ion channels

-Causes sodium channels to open

-Triggers depolarisation

-An action potential is created

What happens to the acetylcholine that isn't taken up by the postsynaptic neurone?

It is broken down into ethanoic acid and choline by an enzyme called acetylcholinesterase. The ethanoic acid and choline are taken up by the presynaptic membrane and converted back into acetylcholine using energy from many mitochondria

What is the difference between temporal and spatial summation?

Temporal is the summation of many smaller action potentials in one neurone to produce one large action potential in the postsynaptic neurone

Spatial is the summation of many smaller action potentials in many neurones to produce one large action potential in the postsynaptic neurone

What are the differences between the nervous and endocrine systems?

Nervous- uses neurones and synapses

Endocrine- uses blood

Nervous- specific pathway for specific response

Endocrine- general pathway for specific response

Nervous- electrical and chemical signal

Endocrine- chemical signal

Nervous- quicker and short duration

Endocrine- slower and long duration

What are endocrine glands?

Give some examples

Ductless glands that consist of a group of cells that secrete a hormone straight into the blood

e.g. pituitary gland, ovaries, testes, adrenal gland

What are exocrine glands?

Give some examples

Ducts which release larger molecules such as enymes or sweat, not directly into the blood

e.g. salivary glands, sweat glands

What are the two types of hormones and some information about each type?

Protein and peptide homones- insoluble, so have to bind to a receptor and have a secondary messenger inside the cell. e.g. insulin, glucagon, adrenaline

Steroid hormones- soluble, so can enter the cell and have a direct effect on the DNA in the nucleus e.g. oestrogen, testosterone

How does adrenaline cause its effects on cells?

It is unable to enter the target cells so it binds to a complementary receptor on the cell surface membrane. This receptor is associated with the enzyme adenyl cyclase which is inside the cell, and is activated when adrenaline binds. Adenyl cyclase converts ATP to cAMP, which causes enzymes in the cell to become activated.

Where is adrenaline manufactured?

The adrenal medulla

What are the effects of adrenaline?

Relaxes smooth muscle in bronchioles

Increases stroke volume and heart rate


Stimulates conversion of glycogen to glucose

Dilates pupils

Improves mental awareness

How does relaxing smooth muscle in the bronchioles prepare you for activity?

Widens airways which allows more airflow and increases O2 intake and CO2 expulsion

What is manufactured in the adrenal cortex?

Steroid hormones such as mineralocorticoids (ion monitoring) and glucocorticoids (control metabolism of carbs and proteins)

Describe the exocrine functions of the pancreas

Secretes enzymes; cells arranged around tiny tubules manufacture and secrete the enzymes into the tubules when stimulated by a hormone or a nerve impulse. The tiny tubules join together to form the pancreatic duct, which carries to (digestive) fluid to the duodenum

What is contained in the digestive fluid from the pancreatic duct?

Enzymes: amylase, trypsinogen, lipase

Sodium hydrogencarbonate to neutralise stomach acid

Describe the endocrine functions of the pancreas

Islets of Langerhans have alpha and beta cells which respectively manufacture and secrete glucagon and insulin directly into the blood

How are alpha and beta cells in the Islets of Langerhans specialised?

-Lots of ribosomes and RER for protein synthesis

-Lots of golgi apparatus for protein processing and packaging

-Lots of secretory vesicles to transport the hormone

-Many mitochondria to supply ATP for exocytosis

How is the concentration of blood glucose regulated ? mark scheme answer

beta cells / alpha cells / receptors , detect , change / increased / decreased ,in blood glucose (concentration)

;2 ) if high(er) glucose (concentration) , beta , cells (in pancreas) release insulin

3) (increased) uptake of glucose by ,liver / muscle / effector , cells ;

4) enters through glucose transport proteins (in cell surface membrane) ;

5) glucose converted to glycogen / (glycogenesis );

6) increased (use of glucose in) , respiration / ATP production ;

7) if low(er) glucose (concentration) , alpha /  , (in pancreas) cells release glucagon ;

8 (increased) conversion of glycogen to glucose / glycogenolysis ;

9 (increased) conversion of other compounds(amino acids / lipids) to glucose / gluconeogenesis ;

10 glucose leaves cells , by facilitated diffusion / through glucose channels ;

What is the sequence of events if blood glucose concentration is too high?

Beta cells detect the change and secrete insulin directly into the blood

Target cells on the liver (hepatocytes) and some other body cells have complementary receptors which the insulin molecule binds to

Activates adenyl cyclase inside the cells which causes the conversion of ATP to cAMP, which activates a series of enzyme controlled reactions inside the cell

How does insulin reduce blood glucose concentration?

Causes more glucose channels in the cell surface membrane to open

More glucose diffuses into the cells down a concentration gradient

Glucoes is converted into glycogen- glycogenesis

More glucose is converted into fats

More glucose is used in respiration

What is the sequence of events if blood glucose concentration is too low?

Alpha cells detect low blood glucose concentration and secrete glucagon

Target cells on the liver (hepatocytes) have a receptor which is complementary to glucagon, allows it to bind

Causes adenyl cyclase to be activated inside the cells, which leads to the conversion of ATP to cAMP and a series of enzyme controlled reactions inside the cell

How does glucagon increase blood glucose concentration?

Stored glycogen is broken down by hydrolysis to glucose (glycogenolysis)

Causes more fatty acids to be used in respiration

Causes the conversion of amino acids and fats into glucose (gluconeogenesis)

Glucose leaves cells by facilitated diffusion through glucose channels into the blood

Describe how insulin is released from a beta cell

High blood glucose concentration causes glucose to diffuse into the cell

Glucose is metabolised to produce ATP

The ATP causes potassium ion channels in the beta cell's cell surface membrane to close

Causes a buildup of potassium ions which makes the cell less negative inside

Change in p.d. causes calcium ion channels to open

Calcium ions which enter the cell cause the vesicles of insulin to fuse with the cell membrane, releasing insulin by exocytosis.

What are the names of the two nerves that can alter heart rate?

Vagus nerve can slow down the heart rate

Accelerator nerve can increase heart rate

How is high blood pressure detected?

Carotid sinus in the carotid artery has stretch receptors which detect the stretching of the arteries to accommodate a high blood pressure

How is a high blood CO2 concentration detected?

Chemoreceptors in arteries can detect the lowered pH from increased CO2

What is the stroke volume?

The volume of blood pumped per beat

What is the medulla oblongata?

A region at the base of the brain which coordinates the unconcious functions of the body e.g. breathing rate and heart rate

Why is ATP made in respiration?

It releases more energy when it is broken down than it requires to be made
Describe the steps involved in the ATP cycle

ATP is hydrolysed to ADP and Pi. This releases energy which becomes available to cells.

Energy from respiration is used to remake ATP in a condensation reaction, aided by the enzyme ATP synthase. To do this, ADP is phosphorylated which transfers energy to the ATP molecule.

ATP is hydrolysed......

What is an anabolic reaction?

A metabolic reaction that builds large molecules

What is a catabolic reaction?

A metabolic reaction that breaks large molecules into smaller ones

How is energy used in the activation of chemicals?

Energy is required for phosphorylation at the beginning of respiration so that it is more unstable and can be broken down to release energy
What are photoautotrophs?

Organisms that use light energy in photosynthesis to make large, organic molecules that contain chemical potential energy

How much energy is released when ATP is hydrolysed to ADP and Pi?

30.6 KJ per mol

How much energy is released when ADP is hydrolysed to AMP and Pi?

30.6 KJ per mol

How much energy is released when AMP is hydrolysed to Adenosine and Pi?

14.2KJ per mol
What is a co-enzyme?

An organic non-protein molecule that helps an enzyme to catalyse a reaction

Why are coenzymes needed in respiration?

Enzymes are not good at catalysing oxidation or reduction reactions so coenzymes are needed to carry out the oxidation reactions in respiration. The coenzymes can transport hydrogen atoms for use in reduction.
What is the structure of NAD?

2 linked nucleotides. The nucleotide contains the nitrogenous base adenine, and the other contains a nicotinamide ring. The two nucelotides are joined by the 2 phosphate groups.

Why is NAD often called a nucleic acid derivative?

It contains phosphoryl groups, adenine and ribose sugar which are all found in RNA.

What is CoA made out of?

amino acid- cysteine

patothenic acid- a B group vitamin

3 phosphoryl groups

adenosine- nitrogenous base adenine with a ribose sugar

Why is there not much NAD or CoA in cells?

They are recycled and can be regenerated

Who might become deficient in NAD? Why?

People who drink lots of alcohol

Alcohol is metabolised in the liver where it is oxidised to ethanol (by dehydrogenation)

It is then oxidised again from ethanol to ethanoate (acetate)

When these substances are reduced, the hydrogen atoms are combined with NAD, which means there is less NAD available for respiration purposes.

Which stages of respiration occur in the mitochondria?

Link reaction

Krebs cycle

Oxidative phosphorylation

How might some humans' mitochondrias be different from cell to cell?

Trained athletes may have larger mitochondria in their muscle cells

Metabolically active cells (e.g. hepatocytes) may have many more mitochondria, which may be larger and have more densely packed cristae (larger surface area for electron transport change and ATP synthase enzymes)

Why has it been suggested that mitochondria are derived from prokaryotes?

-Similar in length

-Both have 70s ribosomes (smaller)

-Both have similar style of DNA

Why does glycolysis support the theory of evolution?

It is found and remains in all cell types of all species.

Describe the phosphorylation stage of glycolysis

In glyclosis , which is the first stage, an ATP molecule is hydrolysed to ADP and Pi. The Pi is released and attaches to a glucose molecule at carbon 6. This changes the glucose to glucose 6 phosphate. This isomerises to fructose 6 phosphate. Another ATP molecule is hydrolysed, and this Pi is released and attaches to fructose 6 phosphate. This changes the sugar to fructose 1,6,bisphosohate. This sugar is too large to leave the cell. so broken down into 2 Triose phosphate then into 2 pyruvate.

How many ATP are used and made in glycolysis?

4 ATP molecules made

2reduced NAD molecules made

net increase of 2 ATP

Name 4 photosynthetic pigments
-chlorophyll a or b


- xanthophyl

Explain why plants with several photosynthetic pigments can make more starch than plants with just one photosynthetic pigments
Explain why plants with several photosynthetic pigments can make more starch than plants with just one photosynthetic pigments
Wat is limiting factor ?
Is the factor that is the least favourable , which limits the rate of photosynthesis . If that factor is increased then the rate of photosynthesis increases
Explain fully how each of the following factors can limit the rate of photosynthesis ? 1)Low temp
Low temperature-reduced kinetic enery of enzymes and substrates involved in LIS

- fewer successful collisions between enzymes and substrates-rubisco, RuBP and C02

-less starch made

Explain fully how each of the following factors can limit the rate of photosynthesis ? b) low intensity
Fewer photon absorbed by photosynthetic pigmentsFewer excited electronsLess ATP and NADPH producedLess conversation of GP to TPLess starch
Suggest why on a hot day the rate of photosynthesis may be less at noon
-Increased temp

-Increase rate of transpiration

-Reduced water availability

-Stomata close so less uptake of C02

Or-Increase temp

-at higher temp ,enzyme become denatured

-Enzyme needed in light independent stage (rubisco)

-Rate of photosynthesis decreases

function of adrenal glands
The Adrenal Glands are located above the kidneys.

There are 2 regions within the glands.

Medulla region - Adrenaline is synthesised from amino acids and is secreted by the medulla, in response to danger, excitement or stress. This is also part of the fight/flight response.

Cortex region - Produces cholesterol to produce steroid hormones such as mineralocorticoids (e.g. aldosterone) which help control the concentration of sodium and potassium ions in the blood. The glucocorticoids control synthesis of glycogen, carbohydrates and proteins in the live.

Outline the hormonal and nervous mechanism involved in control of the heart
> adrenaline increases heart rate

>cardiovascular center in medula oblangata

>parasympathetic decreases heart rate

>sympathetic increases heart rate

>high blood pressure detected by stretch receptor

>low ph caused by increase co2 detected by chemoreceptor

>nervous system connected to SAN

>receptor in aorta/carotid