Topic 6 - Organisms respond to changes in their internal and external environment Flashcards
Kinesis
Kinesis is a non-directional response to a stimulus
The rate of movement of an organism is affected by the intensity of the stimulus
Flatworms called planarians possess a network of neurones and simple eye-like structures that have light-sensitive cells
Planarians display kinesis when removed from their usual dark environment
Planarians are found on the underside of stones, hidden from daylight
When a stone is removed or turned over the planarians begin to move in random directions
Once these random movements eventually bring them back into the darkness they stop moving
This type of responsive behaviour helps them to protect themselves from predators
taxes
Taxis is a directional response to a stimulus
The organism moves directly away from or towards the stimulus
A single-celled organism called Euglena which is commonly found in ponds exhibits taxis
It has chloroplasts for photosynthesis and a flagellum to help it swim
The flagellum has a receptor close to its base that is sensitive to light
Euglena swims directly towards the light, this is known as phototaxis
This behaviour is highly valuable as it brings the organism towards the light where it can photosynthesise
maggot experiment
-The animals need to be observed during the experiment to see if turning frequency or movement rate changes in different environments
If movement is directional then the turning frequency would decrease when the organism detects the stimulus
-The results showed that there was always more maggots in the shaded half of the chamber at the end of the experiment
As the maggots were not observed during the experiment it can not be said whether kinesis or taxis has occurred
However, the results do conclude that maggots have the ability to detect bright light and respond by moving until they reach a more favourable environment
define stimulus
detectable change in the internal or external environment of an organism that leads to a response
stimulus –> receptor –> coordinator –> effector –> response
true or false –. if an organism crosses a sharp dividing line between a favourable and an unfavourable environment, its turning rate increases
true
notes from spec
A stimulus is a change in the internal or external environment. A receptor detects a stimulus. A coordinator formulates a suitable response to a stimulus. An effector produces a response.
Receptors are specific to one type of stimulus.
Nerve cells pass electrical impulses along their length. A nerve impulse is specific to a target cell only because it releases a chemical messenger directly onto it, producing a response that is usually rapid, short-lived and localised.
In contrast, mammalian hormones stimulate their target cells via the blood system. They are specific to the tertiary structure of receptors on their target cells and produce responses that are usually slow, long-lasting and widespread.
Plants control their response using hormone-like growth substances.
survival
-organisms increase their chance of survival by responding to changes in their environment
-in flowering plants specific growth factors move from growing regions to other tissues where they regulate growth in response to directional stimuli
-Taxes and kineses as simple responses that can maintain a mobile organism in a favourable environment.
necessary needs of an organism
-an organism needs oxygen to allow for aerobic respiration in order to release energy (ATP) for processes such as protein synthesis
-Needs water = photolysis of water in LDR for ETC
-Needs CO2
-needs nitrate ions to form nitrate molecules in DNA
-require warmth to ensure optimum temperature for enzyme activity
role of spiracles
Oxygen levels decrease when spiracles are closed as its acting as the final electron acceptor during oxidative phosphorylation
CO2 levels increase when spiracles are closed as it is produced in the link reaction as pyruvate is dexcarboxylated form acetate
taxes vs kinesis
Taxes –> directional response to stimulus (positive –> moves towards)
Kinesis –> non-direction response to stimulus (Slower + relies on chance) (negative -> moves away)
e.g algal cells will move towards light so can photosynthesis. This is an example of positive photo taxes
orthokinesis vs kilokinesis
Orthokinesis = change in rate of movement
Klinokinesis = change in the amount of turning
investigating kinesis
-Kinesis is a non-directional response to stimulus. Slower bc it requires on chance. Small, simple, mobile organisms
-using maggots in our experiment is ethical bc they don’t have a complex nervous system
-null hypothesis = there is not statistically significant difference between the number of times the maggot turned left or right
statistical response
The Chi squared value is less than the critical value. This means that there is a greater than 5% probability that the difference in direction of the turn is due to chance. The difference is not significant.
chi-squared
-If your chi-square calculated value is greater than the chi-square critical value, then you reject your null hypothesis. If your chi-square calculated value is less than the chi-square critical value, then you “fail to reject” your null hypothesis.
-null hypothesis = no significant difference
-alternate hypothesis = there will be a significant difference
-chi squared measures the significance of deviations from expected results. Association between 2 co-variables -> categorical data
types of tropism
-Phototropism –> the growth of plants in response to light
-Geotropism –> the growth of plants in response to gravity
-Chemotropism –> the growth of plants in response to chemicals
-Hydrotropism –> the growth of plants in response to water
plant growth
-IAA is produced in the meristem tissue found in the tips of roots and shoots
-it travels down the coleptile to the “zone of elongation” where it either stimulates or inhibits cell elongation
-IAA is considered a growth factor as opposed to a hormone as it can stimulate or inhibit growth whilst hormones only have one target organ and always result in the same response
tropism
Tropism –> growth of a plant root or shoot in response to a directional stimulus –> allows plant the reach the most favourable conditions e.g roots display negative phototropism and positive geotropism
compare taxes and tropism
-both are a non-directional response to stimulus
-in taxes there is movement of the whole organism whilst in tropism just part of the organism moves
phototropism in flowering plants
-cells in the tip of the shoot produce IAA, which is then transported down the shoot
-the IAA is initially transported evenly throughout all regions as it begins to move down the shoot
-light causes the movement of the IAA from the light side to the shaded side of the root
-a greater concentration of IAA builds up on the shaded side of the root than the light side
-IAA causes elongation so shaded side elongates father than light side causing shoot tip to bend towards the light
gravitropism in flowering plants
-cells in the tip of the root produce IAA, which is then transported along the root
-IAA is intially transported to all sides of the root
-gravity influences movement from upper to lower side
-as IAA inhibits elongation of the root cells
-relative greater elongation on cells of upper side compared to lower side causes root to bend downwards
when describing graphs split into into sections and describe everything despite smaller lines (be descriptive)
can you conclude the woodlice shown turn alteration behaviour when distance between forced and second turn was 10cm
-no
-equal numbers
-random chance
x2 investigations
-due to time not distance
-keep distance the same
-increase time between forced and 2nd turn
using the data in the figure above to explain how behaviour of woodlice results in them moving rapidly out of faviourable conditions
-short distances = more alteration
-prevents going in circles
name the type of behavioural response shown in the investigation
-kinesis
-random non-directional movement
-number of turns depends on strength of stimulus
suggest and explain one advantage of this behaviour
-stays in favourable condition
-remains on host
push vs pull stimulus
push = drives pest away from crop plant
pull = attracts pest
taxes movement
towards the stimulus
describe how the maize plants could be selected at random
-make grid/measure plot of maize plants
-use random number generators to make co-ordinates
why was there bare ground between maize and grass species
-avoid contamination between maize and grass
-reduce movement of pests
explain what the results from group A suggest about the factors controlling the behaviour of winged termites
-gravity (geotaxis) -> 60 degree angle
-eyes covered so cannot see light stimulus
-antannea (B) are involved
increased movement =
increased chance of moving away from unfavourable conditions
explain the growth using knowledge of IAA
-IAA produced at tip
-diffuses to shoot
-more elongation of cells on one side than the other
what conclusions can you make of IAA from the figure
-IAA moves to shaded side
-IAA is produced in the dark
taxis =
increase dispersion
no stats test =
dont know significance
why did the student keep the lid on
to reduce/prevent evaporation
could affect IAA concentration
high IAA
stimulates cell elongation
colorimeter = measure
colour / light etc
phototropism in shoot
-stimulate cell elongation
-IAA formed on darker side of the stem as it doesn’t receive light
-IAA diffuses down shoot tip which stimulates cell elongation towards unilateral light
phototropism in roots
-inhibits cell elongation
-increased conc of IAA on bottom sside of root (darkened)
-diffuses up the root reducing cell elongation
-due to gravity the root grows downwards into the soil to avoid light
IAA = move away from light
replace amount with
volume
nervous system
The nervous system is a complex network of cells, tissues, and organs that is responsible for controlling and coordinating the functions of the body. It collects and processes sensory information from the environment and internal organs, and then sends signals to the muscles and glands to produce a response.
explain the importance of reflex actions
-automatic and unconscious response that prevents tissue harm
-involuntary role in homesostasis (maintaing regulation of internal conditions)
describe the sequence of events which allows information to pass from one neurone to next neuron across cholinergic synapse
-an electrical impulse causes calcium ions to enter the axon
-vesicles move to fuse with the pre-synaptic membrane
-acetylcholine is released an diffuses across the synaptic cleft
-it binds with receptors on the post-synaptic membrane
-sodium ions enter the neuron resulting in the depolarisiation of post-synaptic membrane
-if above the threshold a nerve impulse is produced
give 2 differences between a cholingeric synapse and a neuromuscular junction
1) no summation in neuromuscular junction
2) neuron to neuron in choli but neuron to muscle in junction
dendrites
Dendrites – dendrites are thin extensions of the cell body that carry impulses received from neighbouring neurones to the cell body.
cell body
Cell body – the cell body contains the nucleus, mitochondria, and many ribosomes.
axon
Axon – the axon is a long cytoplasmic extension that carries impulses away from the cell body. It is covered in Schwann cells, that surround and support the neurones.
nodes of ranvier
Nodes of Ranvier – these are gaps in the myelin sheath. They occur between adjacent Schwann cells.
resting potential
Neurones are excitable cells, meaning that they can change their resting potential.
The resting potential is the difference in charge across the neuronal membrane when the neurone is at rest. When neurones are at rest, the outside of the cell is more negative than the inside of the cell – this is caused by differences in ion concentrations and maintained by proteins called ion channels
mainting resting potential
The membrane contains many sodium-potassium pumps. Sodium-potassium pumps use active transport to pump three sodium ions (Naᐩ) out of the neurone, and two potassium ions (Kᐩ) in. The membrane is not permeable to sodium ions, so they cannot diffuse back in, creating a sodium ion electrochemical gradien
Potassium ion channels make the membrane permeable to potassium ions. The channels allow Kᐩ ions to diffuse back out of the neurone, so they move from an area of high concentration (the cytoplasm) to an area of low concentration (extracellular space), increasing the positive charge outside.
Anion concentrations are higher inside the neurone. Anions are large molecules with a negative charge, therefore increasing the electrochemical gradient of the membrane.
changes in membrane permeability
-Changes in membrane permeability lead to depolarisation and the generation of an action potential. The all-or-nothing principle
stimulus to response
Stimulus –> sensory neuron –> intermediate (relay neuron) –> CNS –> intermediate (relay neuron) –> motor neuron –> effector –> response
nervous system
Nervous system is divided into CNS (brain and spinal cord) –> co-ordinate nervous responses and the PNS (all nerves that co-ordinate impulses going towards or away from the CNS)
sensory and motor pathways
-The sensory pathways collects impulses from receptors detecting changes that occur in or around the body
-The motor pathways then coordinate the response to those changes —> somatic nervous system coordinates voluntary responses and the autonomic nervous system coordinates involuntary responses
-sympathetic = fight or flight
-parasympathetic = rest and digest
sympathetic nervous system
-The sympathetic nervous system prepares the body for any possible type of emergency. When the fight or flight response takes over, the SNS is activated. During the activation when the body is under stress, the heart rate and breathing increases in response to a release of adrenaline, as well as changes to the organ’s function. Pre- and post-ganglionic nerves send information between the central nervous system (CNS) and the sympathetic nervous system (SNS).
somatic vs autonomic
The overall function of the somatic nervous system is to:
Relay information from the sensory receptors to the brain
Provide a muscle response through the motor pathways
The autonomic nervous system is in control of automatic involuntary functions, playing an important role in homeostasis. It works to make sure the functions run without an issue and takes control during emergencies. Reflexes such as sneezing and coughing are also carried out by the ANS
simple reflex pathways
-rapid, autonomic and involuntary
-this is important bc it protects against damage to body tissue
-simple reflext actions do not have to be learned and so are coordinated in the spinal cord as opposed to the brain
-important in homoeostatic control, etc
steps of nerve impulse
-nerve impulse travels along sensory neuron to spinal cord
-impulse crosses synapse and to relay neuron (intermediate)
-information is passed along motor neuron
-the information from the motor neuron is then detected by the effector to stimulate a reponse
structure of motor neuron
-wrapped in schwann cells which form a myelin sheath
-myelin is comprised of glycolipids, cholesterol and proteins. It insulates the axon down which electrical impulses are transmitted
-myelin acts an electrical insulator bc It is impermeable to ions like Na+. Action potentials can only occur in the gaps of the myelin.
-glycolipids = covalent bond of a monosaccharide to a glycerol molecule and 2 fatty acids
-increases efficiency along nerve cells + preserves strength of electrical message
where do neurons transmit impulses
Neurones transmit electrical impulses, which travel extremely quickly along the neurone cell surface membrane from one end of the neurone to the other
factors which contribute to establishing membrane potential
The active transport of sodium ions and potassium ions
Differential membrane permeability
difference in membrane potential
The cell-surface membrane of neurones has selective protein channels that allow sodium and potassium ions to move across the membrane by facilitated diffusion
The protein channels are less permeable to sodium ions than potassium ions
This means that potassium ions can diffuse back down their concentration gradient, out of the axon, at a faster rate than sodium ions
active transport
Carrier proteins called sodium-potassium pumps are present in the membranes of neurones
These pumps use ATP to actively transport 3 sodium ions out of the axon for every 2 potassium ions that they actively transport in
This means that there is a larger concentration of positive ions outside the axon than there are inside the axon
The movement of ions via the sodium-potassium pumps establishes an electrochemical gradient
discrete
This makes the action potentials discrete events and means the impulse can only travel in one direction. This is essential for the successful and efficient transmission of nerve impulses along neurones
nerve impulses
When receptors (such as chemoreceptors) are stimulated, they are depolarised
If the stimulus is very weak or below a certain threshold, the receptor cells won’t be sufficiently depolarised and the sensory neurone will not be activated to send impulses
If the stimulus is strong enough to increase the receptor potential above the threshold potential then the receptor will stimulate the sensory neurone to send impulses
This is an example of the all-or-nothing principle
An impulse is only transmitted if the initial stimulus is sufficient to increase the membrane potential above a threshold potential
Rather than staying constant, threshold levels in receptors often increase with continued stimulation, so that a greater stimulus is required before impulses are sent along sensory neurones
phospholipid bilayer
the phospholipid bilayer of axon plasma membrane prevents Na+ and K+ ions diffusing across it so channel proteins /ions channels span the membrane
diffuse vs active transport
action potential = diffusion (passive process)
resting potential = active transport
what part of the nervous system controls voluntary responses
somatic nervous system
sensory neuron
Sensory neuron –> cell body is in the middle, long dendron and short axon
intermediate neuron
Intermediate (relay) neuron –> short axon, short dendrite, found in CNS
motor neuron
Motor neuron –> short dendrite and one long axon (no dendron), cell body at the start not middle, nodes of ranvier, schwaan cells
sensory vs motor
-both sensory and motor neurons are connected by a myelin sheath
-sensory neuron transmits impulses to intermediate neuron
-motor neuron transmits impulses to an effecto
dendron vs axon
Dendron = impulse to cell body
Axon = impulse away from cell body away from cell body
dendrite
Dendrite = transmit impulses from one neuron/receptor to another
nodes of ranvier
Node of ranvier = gaps in the mylein sheath/schwaan cells where there is no insulation
summary establishing resting potential
-ions move through voltage gated channels in neurons plasma membrane (affected by changes in electrical charge)
-charge difference maintained by active transport of Na+-K+ pump of inside and outside cell. 3Na+ pumped out of cell and 2K+ pumped in cell
-external = net positive charge and internal = net negative charge called resting membrane potential
-channels are more permeable to K+ ions
-charge across polarised membrane = -70mv
-nerve impulse = stimulus disturbs plasma membrane on dendrite
action potential
Action potential –> change in electrical potential associated with the passage of an impulse
threshold potential
Threshold potential –> the critical level to which the membrane potential must be depolarized in order to initiate an action potential
repolarisation
Repolarization –> change in membrane potential that returns it to a negative value just after the depolarization phase of an action potential
polarization
Polarization –> the establishment of a negative electrical potential between the inside and outside of the plasma membrane
depolarization
Depolarization –> a loss of the difference in charge between the inside and outside of the plasma membrane
hyperpolarization
Hyperpolarization -> a change in a cell membranes potential that makes it more negative
refractory period
Refractory period –> a period immediately following stimulation during which a nerve or muscle is unresponsive to further stimulation
order of action potential
Polarisation –> depolarisation –> threshold potential –> action potential –> repolarisation –> hyperpolarisation –> refractory period
voltages
Depolarisation occurs at +40mv (voltage gated Na+ channels close)
Threshold potential = -55mv
Polarisation occurs at –70mv
resting neuron
-more positive outside cell than inside
-70mv
-the voltage gated Na+ channels and K+ channels are closed. K+ channels are present which make the membrane more permeable to potassium ions. Some diffuse back out of the cell
-Na+-K+ pump causes 3 Na+ ions to move out of the axon and 2K+ ions into the axon
-this causes the outside of the axon to become more positvely charged than the inside so the resting potential is –70mv in the neuron
generating action potential
-impulse/stimulus is detected by a receptor which causes voltage gated Na+ ion channels to open
-Na+ ions diffuse down electrochemical gradient into the axon. This depolarises the membrane
-if the threshold potential is reached the presence of the sodium ions inside the cell triggers more voltage gated Na+ ion channels to open in an all or nothing response
restoring resting potential
-at 40mv the voltage gated Na+ ion channels closed and the voltage gated K+ ion channel opens. The Na+-K+ pump continues to pump 3Na+ out and 2K+ in and resting potential is reestablished.
Na + and K+ channels
rest = both closed
depolarisation = Na+ open and K+ closed
repolarisation = Na+ closed and K+ opend
describe how the resting potential is established in an axon by the movement of ions across the membrane
active transport of 3Na+ ions out of the axon and 2K+ ions into the axon using a sodium potassium pump
Na+ and K+ are
water soluble
explain why different proteins are required for the diffusion of different ions
different proteins have different teritary structures
true or false - intrinsic/carrier proteins actively transport sodium
true - also called ion channels
cobra poison is similar structure to neurotransmitter
-binds to same receptors as neurotransmitter
-blocks impulse
-no depolarisation
sodium ion channel enables
sodium ions to move down electrochemical gradient
high positive to low positive charge
nm to micrometers
divide by 1000 same for mm3 to cm3
units for gradient
conc / time
conc = gdm-3
time = s-1
add together = gdm-3s-1
percentage change =
(old - new) / old x100
if negative number ignore
number of bacteria grown
bacteria at beginning x 2^number of divisions
negative vs positive correlation
scatter graph only
negative = one thing increases, the other decreases
positive = one thing increases, other increases
statistical tests
chi-squared = difference between observed and expected results
t test = compares the mean of 2 groups
correlation co-efficient = strength of a relationship between 2 variables
calculate standard deviation =
(sum of values - mean)^2 / n -1
n = number of values
square root entire thing
> =
larger than
circumference + area
circumference = 2 x 3.14 x r
area = 3.14 x r^2
rectangular prism volume =
surface area =
1/2 x w x l x h
2 (wl + hl x wh)
sphere
surface area = 4 x pi x r^2
volume = 4/3 pi r^3
refractory period (sodium ion channels are closed)
Very shortly (about 1 ms) after an action potential has been generated in a section of the axon membrane, all the sodium ion voltage-gated channel proteins in this section close.
This stops any further sodium ions from diffusing into the axon
Potassium ion voltage-gated channel proteins in this section of axon membrane open, allowing the diffusion of potassium ions out of the axon, down their concentration gradient
This gradually returns the potential difference to normal (about -70mV) – a process known as repolarisation
Once the resting potential is close to being reestablished, the potassium ion voltage-gated channel proteins close and the sodium ion channel proteins in this section of the membrane become responsive to depolarisation again
Until this occurs, this section of the axon membrane is in a period of recovery and is unresponsive
why is the speed of conduction slow in unmyelinated neurons
This is because depolarisation must occur along the whole membrane of the axon
what happens when threshold potential is reached
all or nothing response
true or false -> there are lots of mitochondria in the pre-synaptic neuron
true = manufacture the neurotransmitters
why is it important so the neurotransmitter is broken down immediately after its carried its job
-neurotransmitter is broken down by acetylcholinesterase
-neurotransmitter needs to be broken down as if it was not, the ligand gated sodium ion channels on the post-synaptic membrane would remain open
-this means that the post-synaptic membrane would remain depolarised so no further action potentials could be generated
explain how a synapse filters out uncessary impulses
-an action potential in the pre-synaptic cell will trigger vesicles of neurotransmitters to be released
-however when only a small number of neurotransmitters are released, fewer ligand gated sodium ion channels on the post synaptic membrane open
-this means that fewer sodium ions diffuse into the post-synaptic membrane so threshold potential is not reached
what are neurons separated by
synaptic cleft
importance of hyperpolarisation
Importance of hyperpolarisation = the period of hyperpolarisation is known as the refractory period. No new action potentials can be transmitted down the axon whilst it is hyperpolarised so impulses are discrete. This means the nervous system is not overloaded and the impulse travels in one direction only.
open and close channels
Voltage gated Na+ channel
Voltage gated K+ channel
Polarisation (A)
Closed
Closed
Depolarisation (B)
open
Closing
Repolarisation (C)
Closed
Open
Hyperpolarisation (D)
open
Open / closing
panician corupscle
-found at the nerve endings where an action potential begins.
-polarised and covered in lamellae
-stretch mediated ion channels
-respond to mechanical stimuli such as pressure
-permeability changes to sodium when they are deformed
1) sensory nerve ending wrapped in many layers to connective tissue
2) Pressure causes deformation of lamellae so stretch mediated sodium ion channels open
3) This means that sodium ions diffuse into the axon which causes the depolarisation of the neuron and creates a generator potential
transmission of nerve impulse
-as sodium ions diffuse into the axon the neuron is depolarised and a current is established
-this triggers the opening of the next voltage gated sodium ion channels to open and the action potential moves along the neuron (wave of depolarisation)
-once the action potential has passed the sodium ion channels closed (repolarisation) and enters a refractory period
-this means that the impulse only travels in one direction
process of saltatory conduction
-the myelin sheath insulates the axon and nodes of ranvier are gaps between schwaan cells that allow Na+ to diffuse down the axon through voltaged gated ion channels
-this generates an action potential which jumps between the nodes of ranvier
-local currents are only established between these nodes of ranvier
how motor neuron disease breaks down the myelin sheath
-breakdown of mylein sheath causes the reduction of saltatory conduction = no action potential
-myelin sheath = less insulating to axon
factors affecting the speed of transmission
-temperature = increase in kinetic energy + increase in enzyme activity
-prescence of mylein sheath = increase in saltatory conduction
-diameter of the axon = greater diameter means lower resistance. Na+ ions are able to diffuse faster and set up currents = increase speed of action potential. An impulse will be conducted at a higher speed along neurones with thicker axons compared to those with thinner axons
cholinergic synapse
1) Action potential arrives at the pre-synaptic neuron
2) This stimulates voltage gated Ca2+ channels to open and Ca2+ ions bind to synaptic vesicles in the pre-synaptic neuron
3) This triggers the vesicles to fuse with receptors on the pre-synaptic membrane
4) Neurotransmitters are released via exocytosis and diffuse onto receptors on the post-synaptic membrane across the synpatic cleft
5) Ligand gated Na+ channels open causing an influx of Na+ ions into the post-synaptic neuron to generate an action potential
6) If threshold potential is not reached neurotransmitters (acetylcholine) are hydrolysed by acetylcholinesterase and are re-uptaked into pre-synaptic vesicles. All or nothing response doesn’t occur
This is an exicatory response (EPSP)
explain how the resting potential of -70mv is maintained in the sensory neuron when no pressure is applied
-membrane is more permable to K+ ions and less to Na+ ions
-3Na+ pumped out by active transport
why was the membrane potential the same whether medium or heavy pressure was applied
-threashold potential reached
-all or nothing response
explan how break down of mylein sheath causes slower response to stimuli
-less insulation of axon = reduced action potential
-more depolarisation of membrane area
explain how lower temperature leads to slower nerve impulse condiction
-slower diffusion of sodium and potassium ions
describe how the change shown in the diagram occurs when an action potential is produced
-current generated causes switch of charges
-voltage gated sodium ion channels open and sodium ion enters axon
how is acetylcholinesterase synthesised
-synthesised in the ribosomes
-translation at ribosomes (describe process)
-describe primary and tertiary structure
-protein is modified and packaged into vesicles by the golgi apparatus
why is an action potential less likely at an inhibitory neuron
-as GABA diffuses out of the pre-synaptic neuron it binds to chloride ion channels on the post-synaptic neuron
-this stimulates Cl- to diffuse in and K+ ions out making the membrane potential hyperpolarised
-this therefore means that more depolarisation/stimulation is required for sodium ion channels to open and reach threshold potential
steps for inhibitory synapses
-GABA is found in vesicles on the pre-synaptic neuron.
-GABA leaves pre-synaptic neuron via exocytosis and diffuses down the synaptic clef to the post-synaptic neuron
-GABA binds to chloride channels on the post-synaptic channel which causes Cl- ions to diffuse in
-This triggers the opening of potassium ion channels, releasing K+ out into the synaptic cleft. This creates an electrochemical gradient.
-this causes the membrane to become hyperpolarised as it is less positive inside (-80mv).
-This means it is less likely for and excitatory post-synaptic potential to be generated as more depolarisation is required for the all or nothing response.
neuromuscular junction
-between a neuron and a muscle (motor neuron)
-motor end plate on muscle = terminal dendrite of axon attaches to this muscle fiber
-always exicatory so muscle can contract
neuromuscular junction vs synapse
Neuromuscular junction
-only excitatory
-only links neuron to muscle
-only motor neurons
-action potential ends here
-acetylcholine binds to receptors on membrane of muscle fiber
Synapse:
-inhibitory or excitatory
-only links neurons or glands
-motor, sensory or intermediate neuron
-new action potential can be generated
-acetylcholine binds to receptors on post-synaptic neuron
how drugs can work on synapses
mimic neurotransmitter, inhibit acetylcholinesterase, stimulate release of neurotramsitter, stop ion channels
agonist
Agonist = have same structure as neurotransmiter so can mimic their action at receptors causing more to be activated
antagonist
Antagonist = completely block receptors = no neurotransmitter binding = no action potential
enzyme inhibitor
Enzyme inhibitor = complimentary to acetylcholinesterase. Prevent the breakdown of neurotransmitter. Leads to continuous action potential
stimulant
Stimulant = stimulate the constant release of neurotransmitter = activate more receptors = increase effect of neurotransmitter
channel blockers
Channel blockers = block Ca2+ ion channels = prevent release of any neurotransmitter, preventing action potentials from occurring further on.
how does diazpam affect the number of action potentials
-diazepam is an agonist to GABA
-this means that it is complimentary to receptors of GABA thus increasing amount of neurotransmitters which diffuse across the synaptic cleft
-this hyperpolarises the post-synaptic neuron as Cl- ions diffuse into the neuron and cause K+ ons to diffuse out.
-this means more stimulation is required to open Na+ channels and depolarise the membrane so less action potentials are generated
spatial summation
-number of different pre-synaptic neurons together release enough neurotransmitter to exceed the threshold value
temporal summation
-single presynpatic neuron releases neurotransmitter many times over a very short period.
summation
-low frequency action potentials often lead to the release of insufficnet concentrations of neurotransmitter to trigger a new action potential
suggest how anesthetic S stops the transmission across the synapse
-anesthetic S binds to receptor on acetylcholine
-forms a complex which prevents the new action potential forming as acetylcholine cannot bind to receptors on post-synaptic neuron
should something be used…..
reference standard deviation
why was each person given the same volume of anesthetic per Kg of body mass
different body mass but requires a comparable effect
explain why they are able to use synaptophysin for this purpose
synaptic vesicles are found in a pre-synaptic neuron
describe how this causes depolarisation of the post-synaptic membrane
-triggers the opening of sodium ion channels
-influx of Na+ ions in the membrane
-threshold potential reached
neurotransmitter not removed =
depolarisation is constant
name one method that the scientists could have used to produce many copies of the mutated gene in the lab
PCR (polymerase chain reaction)
what is a DNA probe
-single stranded DNA
-bases complimentary to DNA
-flourescent marker so can be detected
explain how an increase in blood CO2 levels leads to an increase in heart rate
The high CO2 rate is detected by chemoreceptors in the aorta. The chemoreceptors send impulses to the medulla in the brain. The medulla then sends impulses along sympathetic neurons to the sinoatrial node in the heart. The neurons release noradrenaline which binds to receptors on the sinoatrial node.
Compare the sensitivity and visual acuity of rod and cone cells
Rod cells, specialized for scotopic vision in low-light conditions, are highly sensitive to light but have lower acuity and color discrimination capabilities. In contrast, cone cells, responsible for photopic vision in bright-light conditions, have higher acuity, color vision, and spatial resolution.
lipids + schwaan cells = insulation
charged ions cannot pass without transporter protein
why is the axon membrane more permeable to K+
more K+ channels that are open
bigger stimuli =
increase in the frequency of action potential not the voltage
importance of refractory period/hyperpolarisation
-ensures discrete impulses
-action potential travels in one direction
-limitis overwhelming nervous system through regulating the number of action potentials
wider diameter =
increase in speed of conductance = less leakage of ions = increase in action potential
summation
the rapid build up of neurotransmitters to a synapse to help generate an action potential to ensure a sufficient concentration of neurotransmitter
how do calcium ions enter the presynaptic membrane
via facilitated diffusion
spatial summation
-Spatial summation = multiple nerve impulses converge from multiple neurons
temporal summation
-Temporal summation = multiple nerve impulses from one neuron
both temporal and spatial summation
-excitatory responses (EPSP)
-all or nothing response
-multiple impulses
difference between temporal and spatial summation
-temporal impulses = 1 neuron whilst spatial is multiple neurons
summation + more neurotransmitter
More neurotransmitter = more ligand gated sodium ion channels open = action potential generated
detection of light
-retina = located in the back of the eye
-rod cells = detect low light conditions
-cone cells = detect colour (different photosynthetic pigments)
-optic nerve + fovea = important in light detection
Iris = controls how much light enters pupil = dilate with light and constrict in the dark
skin receptors =
pacinian corpuscle
rod cells
Rod cells = monochromatic vision (black + white) cannot distinguish between different wavelengths of light = high sensitivity to light but low acuity (accuracy)
Rod cells have low visual acuity bc they cannot tell which rod cells is providing the impulse and what part of the retina is hit
cone cells
Cone cells = detect colour = low sensitivity but high acuity
Cone cells often have their own bipolar cell and are connected to a sensory neuron in the optic nerve. Only one stimulation required so respond to high intensity light.
Cone cells contain the pigment iodopsin
generator potential = the eye
Generator potential is created in bipolar cells which rod cells are connected too. In order to create a generator potential the pigment in rod cells rhodopsin must be broken down.
retinal convergence
The most common type of receptor in the retina is rod cells
Retinal convergence = more than one rod cell is connected to one gangian cell
Evidence for spatial summation = multiple impulses from multiple rod cells
increase in stimulus =
depolarisation
antagonistic nervous system
-sympathetic and parasympathetic nervous system = antagonistic
myogenic
Myogenic = contraction originates in the muscle tissue. It doesn’t require nervous stimulation (heart)
-the heart requires the nervous system to increase/decrease rate of heartbeat
control of heart beat order
SAN –> AVN –> bundle of hiss –> purkyne fibres –> contraction from bottom up
describe how a heart beat is initiated and coordinated (5 marks)
-sinoatrial node (pacemaker cells in right atrium) contract and send a wave of depolarisation causing atrial contraction,
-AVN then delays the impulse while blood leaves the atria
-layer of non-conductive tissue prevents the wave of depolarisation from moving to the ventricles
-The atrioventricular node then picks up the wave of depolarisation and transmits it to the bundle of hiss
-the impulse then moves along the purkyne fibers and both ventricles contract at the same time at the apex of the heart (up and out)
-blood leaves the heart via semi-lunar valves
order of ECG
atrial systole –> ventricular systole (peak) –> diastole
which point A or B shows contraction of the ventricle
B
force is greater to pump blood round the whole body
its the second peak coming after atrial systole
explain the effect of acetylcholine on cardiac output
decreases cardiac output because heart rate is lower
cardiac output = stroke vol x heart rate
explain why increased cardiac output is advantageous
increase in volume of blood pumped
more oxygenated blood can reach respiring tissues for aerobic respiration to produce ATP for contraction
hepatic and carotid artery
-hepatic artery = takes blood away from liver
-carotid artery = takes blood to brain
cardiac output and stroke volume
-cardiac output = volume of blood pumped out of the left ventricle every minute
-stroke volume = the volume of blood pumped out of the heart (left ventricle) in each contraction. Affected by genetics, gender, age, exercise.
equation for cardiac output
Cardiac output = stroke volume x heart rate
Units for cardiac output = dm3min-1
chemoreceptors
Chemoreceptors detect changes in pH:
-CO2 increases = increased respiration = decrease in pH (more acidic)
-located in carotid arteries and the aorta
-central chemoreceptors located on surface of the medulla (brain stem)
-sends greater frequency of nerve impulses along sympathetic nervous system to SAN releasing noradrenaline if pH decreases = increase heart rate
-if pH increases nerve impulses are sent along the parasympathetic nervous system to SAN releasing acetylcholine = decrease heart rate
baroreceptors
Baroreceptors detect changes in pressure:
-located in aorta and carotid artery
-detect stretching of blood vessels and act to limit increase in blood pressure
-send nerve impulses to medulla then increased frequency of nerve impulses via the parasympathetic nervous system to SAN, lowering heart rate and releasing acetylcholine
increase in CO2
-decrease in pH levels within the blood
-detected by chemoreceptors in carotid artery and aorta
-impulses sent to the medulla
-increase in frequency of nerve impulse along sympathetic nervous system to SAN
-release noradrenaline to increase heart rate so more CO2 exhaled
decrease in CO2
-increase in pH within blood
-chemoreceptors in aorta and carotid arteries
-nerve impulses travel to medulla and increased frequency along parasympathetic nervous system to SAN
-release of acetylcholine to decrease heart rate
increaseing pressure
-stretching of arteries
-baroreceptors in aorta and carotid arteries
-medulla
-parasympathetic nervous system
-release acetylcholine at SAN
-decrease in heart rate
calculating heart rate =
60 / time it takes for 1 heart beat
structure of the skeletal muscle
-skeletal muscles consist of tightly packed muscle fibres surrounded by connective tissue
-each bundle contains multiple muscle fibres which are formed when individual muscle cells fuse together
-muscle fibres contain myofibrils that run the length of the fibre and are responsible for muscular contraction
-myofibrils are divided into repeating sections called sarcomeres each of which represent a single contractile unit
specialised features for muscle contraction
-multinucleated
-large number of mitochondria (muscle contraction requires ATP hydrolysis)
-specialised endoplasmic reticulum (sarcoplasmic reticulum and stores calcium ions)
-tubular myofibrils made up of thin filament (actin) and thick filament (myosin)
-continious membrane surrounding muscle fibre called sarcolemma and contains T tubles
actin vs myosin
Actin = thinner, two strands twisted round eachother
Myosin = thicker, long rod shaped tails, bulbous heads that project to the side
repeating unit =
sarcomere
z line
-Z-line –> end of each sarcomere, centre of I band
I band
-I band = isotropic (only actin), light in colour, shortens during contraction
A band
-A band = overlapping filaments, anisotropic band, dark in colour, stays same length
M line
-M-line = anchor myosin myofibrils
H zone
-H-zone = isotropic (only myosin), shortens during contraction
contraction vs relaxation
Relaxation = less overlap of sarcomere
Contraction = size of A band is the same but H zone decreases
myoglobin
-myoglobin = stores of oxygen in muscle cells.
short vs long distancr running
-short distance running = more fast twitch muscle fibres (anaerobic)
-long distance running = more slow twitch muscle fibres (aerobic)
fast twitch
-anaerobic respiration
-work over short period of time
-found in biceps
-contract rapidly
-more powerful
-essential for power and intense exercise
-stores of phosphocreatine (weightlifting)
-more numerous myosin filaments
-lighter in colour
-higher conc of glycogen
slow twitch
-contracts slowly
-aerobic respration
-found in calf muscles
-less powerful
-more mitochondria
-rich supply of blood vessels
-large stores of myoglobin
-darker in colour
how muscle fibres differ
-proportion of fast and slow twitch muscle fibers (affected by sex, gender, nourishment etc)
-number of mitochondria within a fiber
-diameter of a fiber
The total number of muscle fibre in skeletal muscle remains constant over time
role of glycogen granules in skeleteal muscle
-store of glucose to be hydrolysed for ATP release
-allows for muscle contraction
suggest how the fall in pH leads to a reduction in the ability of calcium ions to stimulate muscle contraction
-low changes in Ph change shape of calcium ion receptors
-fewer calcium ions to bind to tropomyosin
-fewer actin sites on actin releaved
-fewer cross bridges can form
why was the actual number of slow muscle fibres in the field of view was not the same as the calculated number
variation in the number of capillaries per fibre
explain how an opitcal microscope can be used to view stained muscle tissue
-measure with eyepiece graitucle
-calibrate against something with known size
name the protein present in the filaments labelled W and X
W = myosin
X = actin
why would marathon runners have muscle fibres with the highest mitochondria
-more slow muscle fibres
-slow firbes use aerobic respiration
-good for endurance and long periods of exercise to avoid fatigue
more mitochondria =
increase in diameter
explain how a decrease in Ca2+ ions cause a decrease in the force of muscle contraction
-decrease in calcium ions means less tropomyosin moved from binding site on actin
-fewer actomyosin bridges formed
-less ATP hydrolyase activation
why were the trained mice able to exercise for a longer time perod than control mice
-more aerobic respiration produces mor ATP
-slower anaerobic respiration
-more slow muscle fibres
role of phosphocreatine in providing energy
provides phosphate to make ATP
When looking at sarcomeres under a microscope, what evidence do researchers have that the sliding filament model is correct?
Within a contracted sarcomere, the I-band and H-zone become narrower and the z-lines move closer together.
This is because as the actin filaments slide along the myosin filaments, more of the actin and myosin filaments overlap.
Within a contracted sarcomere, the A-band stays the same which means that the myosin filaments inside the A-band haven’t become shorter.
how many codes for an amino acid =
64
explain how aerobic respiration continues with low glucose levels
-acetyl combines with co-enzyme A and enters the krebs cycle
give the reason why phytokplanton have a value of 0Kjm-2 a year for ingested food
phytoplankton = producers
why would calculating net productivity give a value too high
energy lost i other ways other than respiration such as via excretion
explain why it is important that the isolation medium is cold
reduces enzymes activity = less kinetic energy
enzymes released during blending
chloroplast not damaged
explain how the rate of decolrisation of DCPIP is affected by the prescence of ammonium hydroxide
-rate decreases
-slow transfer of electrons along electron transport chain
DO NOT ABREVIATE IN AN EXAM
especially enzyme substrate complexes or light dependent reaction
why is a logarithmic scale used for IAA concentration
large rage of concentration
Explain how IAA causes the roots and shoots to respond to gravity
-IAA accumlates on lower sides of roots and shoot due to gravity
-higher concentrations stimulate cell elongation on lower side of shoot so grows upwards
-higher concentration inhibits cell elongation on lower side of root so grows downwards
more rainfall=
lower nitrate concentration
draw line using ruler from meniscus to determine concentration
more accurate
geotropism = shoots
-IAA accumlates on the lower side of the shoot due to gravity
-in shoots IAA stimulates cell elongation causing the lower side to lengthen more
-shoot grows upwards
geotropism = roots
-IAA accumlates on lower side of the root due to gravity
-in the roots IAA inhibtirs cell elongation causing lower side to lengthen
-grows downwards
explain how IAA causes cell elongation
-diffusion of H+ ions from cytoplasm to cell wall
-H+ = lower pH = bonds between cellulose microfibrils loosen
-K+ ions diffuse into cell membrane = lowers water potential
-more water absorbed by mitosis = increased pressure = stretching
A band movement
-more overlap between actin and myosin
-A band remains same width during muscle contraction. Its width is determined by the length of myosin filaments
sliding filament theory
1) An action potential arrives at the neuromuscular junction
2) acetylcholine is released, binds to receptors on motor end plate. Ligand gated Na+ ion channels open leading to depolarisation (action potential) int the sarcolemma
3) Action potential travels along T-tubules (wave of depolarisation spread across muscle fibre)
4) Ca2+ ions diffuse from the sarcoplasmic reticulum into the myofibrils. Ca2+ ions released and bind to troponin on tropomyosin causing tropomyosin to change shape. Actin binding sites are exposed so myosin heads can bind.
5) The power stroke
power stroke
-a myosin head with ADP and Pi attached forms a cross bridge with the binding site on actin
-Pi is released causing the myosin head to “nod” causing the length of the sarcomere to decrease
-ADP is then released allowing ATP to bind. This breaks the cross bridge
-ATP is hydrolysed, releasing energy to reset the myosin head to its starting position
-cycle continues as long as Ca2+ ions and ATP are present
-At end Ca2+ ions are actively transported back into the sarcoplasmic reticulum
why muscle fibres have store of phosphocreatine
Why muscle fibres have a store of phosphocreatine
-provides phosphate to make ATP
uses of ATP in muscle contraction
-to actively transport Ca2+ ions back into the sarcoplasmic reticulum
-to break the cross-bridge
-to reset myosin to starting position so power stroke can occur
role of Ca2+ ions and ATP in muscle contraction (5 marks)
-calcium ions diffuse from the sarcoplasmic reticulum into myofibrils
-Ca2+ ions bind to troponin on tropomyosin causing tropomyosin to change shape thus exposing binding sites on actin for myosin heads to bind
-Myosin heads form cross bridge with actin and Pi is released causing to bend (nod) and length of the sarcomere shorterns
-allows sliding of actin and myosin filaments
-ADP is then also released so ATP can bind to the myosin head so cross bridge breaks
-ATP is hydrolysed, releasing energy in order to detach the myosin head from actin filaments to reset back to starting position
lack of oxygen
reduced aerobic respiration –> less ATP production via oxidative phosphorylation –> less breaking of cross bridge –> less contraction
drug blocking acetylcholine
less Na+ ions enters the muscle –> no wave of depolarisation along T-tubules –> less Ca2+ ions released from sarcoplasmic reticulum
low pH within muscle fibres
ATPase denatures = less ATP hydrolysed
muscle relaxation
-active transport of Ca2+ ions back into the sarcoplasmic reticulum using energy from the hydrolysis of ATP
-reabsorption = allows tropomyosin to block actin filaments again
-myosin heads are now unable to bind
notes from spec on homoestasis
-Homeostasis in mammals involves physiological control systems that maintain the internal environment within restricted limits.
The importance of maintaining a stable core temperature and stable blood pH in relation to enzyme activity.
The importance of maintaining a stable blood glucose concentration in terms of availability of respiratory substrate and of the water potential of blood.
Negative feedback restores systems to their original level.
The possession of separate mechanisms involving negative feedback controls departures in different directions from the original state, giving a greater degree of control.
homoestasis
Homeostasis = maintenance of constant internal conditions
regulation by homeostasis
Regulation by homeostasis:
-control temperature
-control blood glucose
-control water levels
-control urea concentration
-control water levels
negative vs positive feedback
Negative feedback = departure/deviation from a norm initiates changes which restore a system to the norm
Positive feedback = departure from the norm initiates the change to further increase
importance of homeostasis
-ensure optiminal water potential
-ensures enzymes are able to work at their optimum to catalyse reactions
-allows survival of an organism in a greater range of external environment
negative feedback
-temperature control (if temp is too high the control centres triggers a mechanism to cool the organism)
-reverses the effect of stimulus detected
-active process
positive feedback
sodium ion channels open whch triggers more sodium ion channels to open
-accelerates the process
-passive process
use your knowledge of colour vision to see how an orange colour is seen at 600nm
-cone cells = detect colour
-each type of photoreceptor has a different pigment
-greater absorption by red sensitive than green sensitive
adrenaline binds to receptors in the plasma membranes of liver cells. Explain how this causes the blood glucose concentration to increase
adenylate cyclase is converted into cAMP as it becomes actvated
enzymes are acivated within the cells so glucogenolysis occurs to convert glycogen into glucose
explain how the binding of insulin leads to an increase in the rate of respiration in cells such as osetoblasts
-more carrier proteins for glucose
-glycolysis can occur
use information from the diagram to explain why this is positive feedback
-osteoclast causes more insulin to be released
-more insulin = more osetoclast activated
why was it important that all of the mice were given the same food each day
- to keep starch intake the same
- to prevent irregulations in blood glucose concentration
inhibtior of amylase = lower blood glucose conc
prevents hydrolysis of starch to maltose to glucose
fewer enzyme substrate complexes form
explain how the presence of abnormal insulin receptors results in a high blood glucose concentration
-insulin is not complementary to abnormal insulin receptors
no carrier proteins for glucose movement
hormones
-long-lasting
-travel through bloodstream
-released from glands
-bind to receptors on target organ
explain importance of maintaing optimum blood glucose concentration
-too low = less glycolysis = less ATP production = less muscle contraction
-too high = decrease in water potentia = water moves out of cells via osmosis and into blood = causes crenation (cells shrivel)
pancreas
Pancreas = point of production for insulin and glucagon
explain how insulin reduces the conc of glucose
insulin is released by beta cells in the islets of Langerhans in pancreas
-insulin attaches to receptor sites on the cell surface membrane of liver/muscle cells
-this causes more glucose carrier proteins so membrane permeability to glucose increases as more carriers are available.
-glucose moves into liver cells via facilitated diffusion
-glycogenesis = glucose is converted into glycogen in cells via condensation reaction
describe the role of glucagon in the control of blood glcuose
-glucagon responds to lower levels of blood sugar
-produced in alpha cells in islets of Langerhans
-glucagon attaches to specific receptor sites on the cell surface membrane of liver cells and triggers enzymes involved in the hydrolysis of glycogen (glycogenolysis)
-this causes the creation of glucose which diffuses out of liver cells causing blood glucose levels to increase.
-an insufficient supply of glycogen causes gluconeogenesis from amino acids and fatty acids
Use evidence from the graph to explain the role of negative feedback in the control of plasma glucose concentration (5 marks)
-negative feedback = increases corrective mechanisms from deviation from the norm
-initial blood glucose concentration decreases = glucagon
-increases = insulin
glycogen
-glycogen = insoluble store of glucose (polysaccharide)
glucose
-glucose = monosaccharide used in respiration (soluble)
insulin
-insulin = hormone that lowers blood glucose levels produced in the pancreas (beta cells in the islet of langerhans
glucagon
-glucagon = hormone that increases blood glucose levels by breaking down glycogen
gluconeogenesis
-gluconeogenesis = creation of new glucose from amino acids and fatty acids
glycogenesis
-glycogenesis = creation of glycogen from glucose via condensation reaction
glyconeolysis
-glycogenolysis = break down of glycogen into glucose
blood glucose is too high
1) pancreas detects high blood sugar and beta cells in islets of langerhans secretes insulin into the bloodstream
2) Insulin attaches to receptor sites on the cell surface membrane of respiring cells e.g muscle and liver cells
3) This causes an increase in the number of glucose carrier proteins within the cell membrane. Increased permeability so more glucose diffuses into muscle/liver cells via facilitated diffusion
4) excess glucose is converted into glycogen via condensation reactions in a process known as glycogenesis. Glycogen is insoluble so does not affect osmotic potential
blood glucose is too low
1) pancreas detects low blood sugar and alpha cells in the islets of langerhan secrete glucagon into the bloodstream
2) glucagon attaches to specific receptor sites on the cell surface membrane of liver/muscle cells and triggers enzymes involved in the hydrolysis of glycogen to glucose (glycogenolysis)
3) glucose diffuses out of liver/muscle cells causing blood glucose level to increase again
4) if there is not enough glycogen available the body starts to generate glucose from amino acids and fatty acids in a process known as gluconeogenesis
role of adrenaline
1) attaches to protein receptors on the cell membrane of target cells
2) activates enzymes that cause the breakdown of glycogen to glucose (glyconeolysis)
second messenger model = adrenaline
Second messenger model
1) Adrenaline (first messenger) is secreted and binds to the receptor on the target liver cell
2) this causes the protein on the membrane to change shape
3) activates adenylate cyclase
4) adenylate cyclase converts ATP to cyclic AMP (cAMP)
5) cAMP acts as a secondary messenger that binds to the protein kinase enzyme
6) protein kinase catalyses the conversion of glycogen to glucose
During release of adrenaline glyconeogenesis is inhibited
diabeties
-diabeties = metabolic disorder = inability to control blood glucose
type I
Type I = insulin dependent = unable to produce insulin. May be the result of an auto-immune response in which the body’s immune system attacks B cells in the islets of langerhan. Also affects glycogen stores resulting in fatigue. Common in childhood
type II
Type II = glycoprotein receptors on body cells being lost or loosing responsiveness to insulin. Risk factors = obesity, poor diet, lack of exercise etc. Age 40+. Could also form due to inadequate supply of insulin from the pancreas
control of type 1
-Type I = injections of insulin (not orally as it is a protein and would be digested). Dose of insulin must be matched to dose of glucose intake. Monitored by biosensors.
control of type II
-Type II = controlled by regulating intake of carbohydrate in the diet and matching this to the amount of exercise taken. Insulin supplements taken if necessary
health advisors vs food manufacturers
Health advisors play a crucial role in educating individuals about healthy lifestyles. = guidance of nutrition etc.
Food industries marketing practices have been linked to increasing the incidence of diabetes. Primary goal is to maximise profits by selling food products.
disruption to insulin function
Insulin function is disrupted = increase in blood glucose = kidneys become unable to filter excess glucose in urine = increased urination = dehydration
diabetes = high blood pressure
Poor controlled diabetes results in high blood pressure as glucose lowers water potential in blood so larger volume of blood within circulatory system.
kidney basics
-renal artery = takes oxygenated blood to the kidney
-adrenal glands = sit above the kidneys
-Role of kidneys = filter waste products from blood
Kidney basics:
-located below the rib cage = cleans the blood by passing fluid and waste products through a biological filter called a nephron.
-nephron = blocks blood cells and important molecules like proteins
-necessary molecules are passed back into the blood + watse exits the body in urine
-Kidneys = prevent waste build up + stabilize electrolyte levels
-patients undergo dialysis when in kidney failure
structure of nepheron
Renal artery –> Afferent arteriole –> Golmerous –> bowmans capsule –> efferent arteriole –> proximal convulted tube –> descending limb (loop of henle) –> ascending limb –> distal convoluted tube + capillaries –> collecting duct –> capillaries
bowmans capsule
Cup like structure called the bowmans capsule that contains a knot of blood vessels called the glomerlus. Glomerlus recieves blood from afferent arteriole. Inner wall of the bowmans capsule is line with specialised cells called podocytes and it extends the proximal convoluted tubule whose walls are lined with microvilli from epithelial cells.
describe how ultrafiltration produces glomerula filtrate
high hydrostatic pressure of blood in the affterent arterile which has a wider diameter than efferent arteriole
-ions/urea/glucose/water move out of pores in endothelium of capillaries and forced through filtration slits due to podoctyes forming the golmerous filtrate
-movement from basement membrane to form filtrate
-proteins and red blood cells remain within capillaries as they are too large molecules
-there is resistance in bowmans capsule due to the movement required for the filtrate in which components like glucose are forced out
explain 2 ways the proximal convulated tubule is specialised for absorption
many microvilli = high surface area for absorption
-folded membrane = increase surface area
-many mitochondria
intersitial fluid + basement membrane
Interstitial fluid = fluid between nephron and surrounding blood capillaries
Basement membrane = comprise of podocytes = movement + cpaillarries = pores for fast diffusion
ultrafiltration in bowmans capsule
-blood enters the glomerulus via the afferent artertiole at high hydrostatic pressure
-red blood cells + proteins remain in the blood since they are too large
-ions/urea/glucose/water form the glomerula filtrate as they are squeezed out of the capillaries and pass through the basement membrane
-high resistance in bowmans capsule
adaptations of bowmans capsule
-high hydrostatic pressure = afferent arteriole = wider diameter
-podocytes have gaps in their branches (filtration slits)
-spaces between endothelium cells of basement membrane allow fluid to pass
-high hydrostaic pressure of blood forces filtrate out
co-transport in proximal convoluted tubule
-active transport of Na+ ions using sodium potassium pump out of PCT wall (intersistial fluid). This creates a conc gradient for the diffusion of Na+ ions and glucose from proximal tubule epithelial cels suing transporter protein. Glucose moves via facilitated diffusion into capillaries. The prescence of glucose lowers water potential in interstital fluid causing water to move via osmosis back into the capillaries.
-85% of reabsorption happens in proximal convoluted tubule
-tubular lumen –> proximal tubule epithelial cells –> interstitial fluid –> capillary
selective reabsorption in loop of henle
-As the filtrate travels down the descending limb, ions diffuse out into intersitial fluid. Water also moves out via osmosis down the water potential gradient. The water and ions are reabsorbed into the blood.
-As the filtrate travels back up the ascending limb ions are actively transported out into the interstial fluid. Water cannot leave because the ascending limb is impermeable to water.
-This means that the filtrate entering the distal convoluted tubule has a higher water potential meaning more can be absorbed from the PCT by osmosis
-those in drier conditions have longer loop of henle
-ascending limb = impermeable to water = high water potential
-urea remains in tubule bc whole loop of henle is impermeable to urea
-water moves down descending limb due to lower w.p at bottom of loop due to urea filtrate
-selective reabsorption = all glucose, some water, some ions
overall kidney structure
-ureter = carries urine from kidneys to bladder
-urethra = releases urine outside the body
-medulla = made of loops of henle
-fibrous capsule = outer membrane that protects the kidney
-cortex = made of bowmans capsule (lighter than medulla)
give on component of blood which is not normally present in the filtrate
proteins
describe another way that the kangeroo rat could obtain water
respiriation = oxidative phosphoryation
where does ultrafiltration occur
glomerulus
ADH =
makes cells more permeable
explain how a lack of insulin affects the reabsorption in the kidneys
-high conc of glucose in blood and filtrate
-reabsorbed via facilitated diffusion using glucose carrier proteins
-all proteins saturated = not all glucose is reabsorbed
explain how the activity of the kidney reults n this clearance value for glucose
-filtration out of blood plasma into renal capsule at high hydrostatic pressure
-ALL glucose reabsorbed in lining of PCT via activity transport
write an essay on negative feedback in living organisms
-osmoregulation
-hameoglobin dissociation curve + cooperative binding
-control of blood glucose
-control of heart rate (chemoreceptors + baroreceptors)
loop of henle =
counter current flow
increase in ions =
lower water potential
diabeties + filtration
ADH inhibited or secreted
Lower water potential = ADH secreted
High water potential = ADH inhibited
low water levels
1) Osmoreceptors in the hypothalamus of the brain detect fall in water potential as osmoreceptors shrink (water leaves cells via osmosis)
2) Change in size of osmoreceptors triggers the hypothalamus to produce a hormone called ADH which is secreted from the posterior pituitary gland
3) ADH passes from the blood to the kidney; it binds to receptors on the cell surface membrane of cells that make up the distal convoluted tubule and collecting duct
4) Binding of ADH leads to the activation of phosphorylase. Causes vesicles containing aquaporins to fuse with the cell surface membrane, increasing the permeability of the membrane to water
5) More water leaves the collecting duct by osmosis down a water potential gradient and re-enters the blood.
6) Osmoreceptors also send nervous impulses to the thirst centre of the brain to encourage the individual to drink more water
high water levels
1) Osmoreceptors in the hypothalamus of the brain detect increase in water potential as osmoreceptors increase in size (more turgid) (water enters cells via osmosis)
2) Change in size of osmoreceptors triggers the hypothalamus to inhibit a hormone called ADH.
3) Less ADH binds to receptors on cell surface of membrane
4) Less activation of phosphorylase = less aquaporins fuse with cell membrane = permeability decreases
5) Less water leaves the collecting duct by osmosis down a water potential gradient and re-enters the blood.
6) Osmoreceptors also send fewer nervous impulses to the thirst centre of the brain
why does ADH only bind to specific receptor sites
-ADH = hormone = protein
-specific tertiary structure = only complementary with receptor sites on collecting duct and distal convoluted tubule
true or false = osmoregulation is a form of negative feedback
true
osmoregulation
Which organelles are present in high quantities within a cell lining the collecting duct:
-rough endoplasmic reticulum
-golgi apparatus = produce aquaporins + store in vesicles
Causes of fall in solute concentration:
-large volumes of water consumed
-salts used in metabolism + excreted
medulla =
location of loop of henle
thicker medulla = longer loop of henle
longer loop of henle = increase in sodium ion concentration
water potential of filrate reduces =
less water reabsorbed by collecting duct through osmosis
descending vs ascending limb
descending = sodium ions enter and water moves out
ascending limb = sodium ions actively transport out but water remains as it is impermeable to water
damage to basement membrane =
alterations in filtrate e.g proteins could now pass into the filtrate
2 factors that could affect the concentration of creatine in the blood
-exercise
-muscle mass
gluconeogenesis + glucagon
-activates enzymes
-amino acids into glucose
after the student stared at the purple square he saw a green afterimage. Suggest why
-red and blue cone cells stimulated, green arent
-red and blue cone cells become exhausted
-afterimage is due to green cone cells working
use the information to explain why the diversity of consumers is greater at site b
-increased variety of food
-more variety of habitats
mark-recapture =
allow time to reintergrate with the rest of the population
