Topic 6 - Internal and External Changes Flashcards
define a stimulus
a change in an organisms internal or external envrionment
why is it important that organisms can respond to stimuli
organisms increase their chance of survival by responoding to stimuli
what is IAA’s effect on shoot tissue
it stimulates cell division and elongation
what tropisms does IAA cause in shoot tissue
a positive phototropic response (phototropism) and negative gravitropic response (geotropism)
what tropisms does IAA cause in root tissue
it causes a positive gravitropic response and a negative phototropic response
what is IAA’s effect on root tissue
it inhibits cell devision and elongation
define a hormone
a chemical messener produced by a gland that travels in the bloodstream which affects a target organ
why is auxin a plant growth factor
- it is produced by a collection of undifferentiated cells called a meristem (not a gland)
- it diffuses through plant tissue (not transported in the blood)
- it affects many cells/tissues including the cells that produces it
what is auxin
a group of plant growth factors
what auxin do we need to know about
IAA
what is a tropisim
growth of a plant in response to directional stimulus
what does positive tropism mean
growth of a plant towards a stimulus
what does negative tropism mean
growth of a plant away from stimulus
what does a clinostat enable
for there to be an equal gravitational force on plants when growing
state 3 things that have an impact on growth response
- growth factor
- concentration of the growth factor
- tissue responding to the growth factor
what type of concentration of IAA do weed killers have
very strong
explain gravitropism in flowering plants
- cells in trip of shoot/root produce IAA
- IAA diffuses down shoot/root intially evenly
- IAA moves to lower side of shoot/root so concentration increase
- cell elongation in shoots is stimulated whereas in roots it inhibits cell elongation
- shoots bend away from gravity whereas roots bend towards gravity
explain phototropism in flowering plants
- cells in tip of shoot/root produce IAA
- IAA diffuses down shoot/root evenly initially
- IAA moves to shaded side of shoot/root so concentration increases
- in shoots, this stimulates cell elongation whereas in roots, this inhibits cell elongation
- shoots bend towards light whereas roots bend away from light
how can organisms increase their chance of survivial
they can respond to changes in their environment
what is the sympathetic nervous system responsible for
it is responsible for the fight or flight response
what is the parasympathetic nervous system response
the rest and relax actions - e.g. digestion
what is the autonomic nervous system responsible for
for involutary actions e.g. heart beat, pupil dilation
what is the somatic nervous system responsible for
responsible for voluntary movements e.g. muscle movements
what does the central nervous system control
the brain and spinal cord
what does the peripheral nervous system control
the cranial and spinal nerves
what is the central nervous system responsible for
sensory activities, storing memories and emotions
what does the peripheral nervous system do
it brings messages to and from the CNS to the rest of the body
describe the structure of a motor neurone
should have mentioned:
- nucleus
- cytoplasm (in cell body)
- dendron branched into dendrites
- axon (also cytoplasm)
- myelin sheath
- schwann cell (make up the myelin sheath)
- node of ranvier (gap btwn the schwann cells)
describe the structure of a sensory neurone
- axon
- dendrites
- dendron
- cell body (partway along the axon, adjacent)
describe the structure of an intermediate/relay neurone
- axon
- dendrites
- dendron
- cell body is part of the axon and not parallel to it
define nerve impulse
a self propagating wave of electrical disturbance that travels along the surface of the axon membrane
describe resting potential
the axon cytoplasm is less positively charged compared to the surrounding tissue fluid
explain how a resting potential is established across the axon membrane in a neurone
- Na\k pump actively transports (using ATP) Na out of the axon and K into the axon
- this causes an electrochemical gradient = higher K conc inside and higher Na conc outside
- differential membrane permeability = more permeable to K - move by FD. less permeable to Na
what does self propagating mean
the previous section causes the next section to become depolarised
what does electrical disturbance mean
unequal distribution of positive ions NaK
what does surface of an axon mean
only impacts the surface of the phospholipid bilayer = diameter of the neurone can affect the speed of an action potential
describe action potential
when the axon cytoplasm becomes more positively charged than the surrounding tissue fluid
how many sodium and potassium ions are pumped out each time
3 sodium out for 2 potassium in
Na-OUT and K-in
how is the unequal distribution of Na and K in the cytoplasm and tissue fluid maintained (how is a resting potential maintained)
- the phospholipid bilayer of the axon is impermeable to Na and K
- intrinsic proteins are found in the phospholipid bilayer: Na voltage gated channels are closed. K voltage gated channels are some are alwaysopen and some are closed when it is resting potential
- a sodium otassium pump actively transports Na and K across the axon membrane: 3 Na out, 2 K in
what is the approx value of the resting potential
-65 mV (milli volts)
what is the peak value of the action potential
+40 mV
can you draw/label a graph showing action potential
labelled:
- voltage gated Na channels open
- Na channels open
- hyperpolarisation
- resting potential
- stimulus
- depolarisation
- repolarisation
- voltage gated Kchannel open,Na channel closed
- voltage gated K+ channel close
define action potential
when a stimulus detected by a receptor and the energy causes a temporary reversal of the charges on the axon membrane
what is the membrane like during action potential
depolarised
why does depolarisation occur
due to the voltage gated channels
what is the difference between resting and action potential
resting - more +ve outside
action - move +ve inside
describe action potential
at resting potential:
- some K+ gated channels are open
- all Na+ gated channels are closed
the energy of the stimulus causes some of the Na+ gated channels to open
- Na+ diffuses into the axon along the electrochemical gradient
- this causes a reversal in potential difference across the membrane
Na+ diffuses into the axon
- axon cytoplasm becomes more positive = more Na+ gated channels open
- amplifies the influx of Na+
when the action potential reaches +40mV the Na+ gated channels close
- additonal K+ gated channels open
K+ gated channels are open = electrochemical gradient is reversed
- K+ diffuses out of the axonn = repolarisation of the axon
hyperpolarisation (axon cytoplasm is more negative than usual)
- K+ gated channels close
- NaK pump resores to 65 mV
- axon is replenished
describe the all or nothing principle
- for an action potential to be produced, depolarisation must exceed the threshold potential
- action potentials produced are always the same magnitude/size at the same potential
what is the effect of bigger stimuli on the action potentials
they increase the frequency of action potentials
What happens according to the all or nothing principle when depolarisation is below the threshold
NOTHING
no action potential which means that there is no impulse generated
any stimulus whatever the strength below the threshold value will fail to generate an action potential
what happens according to the all or nothing action potential when depolarisation is above the threshold level
ALL
action potential generated so the nerve impulse will travel
the action potential are the same size at the same potential and always peak at the same maximum voltage
the strength of a stimulus does not affect the size of action potential
how can an organism perceive the size of a stimulus if all action potentials are the same size
number of impulses passing in given time (frequency) - larger stimulus = more impulses generated in a given time
different neurons with different threshold values - brain interprets number/types off neurons that pass impulses as a result of a given stimulus = determines the size
why is the all or nothing principle important
ensure animals only respond to large enough stimuli rather than responding to every slight change in the environment which would overwhelm them
describe the nature of the refractory period
the time taken to restore the acon to resting potential when no further action potential can be generated as the Na+ channels are closed and will not open
explain the importance of the refractory period
ensure discrete impulses are produced - action potentials don’t overlap
limits the frequency of impulse transmission at a certain intensity - prevents over reaction to stimulus
- higher intensity stimulus cuases a higher frequency of action potentials only up to a certain intensity
ensures action potentials travel in one direction
define nerve impulse
the transmission of an action potential along an axon
describe the speed an action potential moves
0.5 m/s - 120 m/s
suggest how damage to the myelin sheath can lead to slow responses and/or jerky movements
less saltatory conduction = depolarisation occurs along the whole length of the axon, so nerve impulses take longer to reach neuromascular junction/delay in muscle contraction
ions/depolarisation may pass/leak to other neurones = wrong muscle fibres contract
describe how the passage of an action potential along non-myelinated axons result in nerve impulse
action potential passes as a wave of depolarisation
influx of Na+ in one region increases permeability of adjoining region to Na+ by causing voltage-gated Na+ channels to open so adjoining region depolarises
describe how the passage of an action potential and myelinated axons results in nerve impulses
myelination provides electrical insulation
depolarisation of axon at nodes of Ranvier only
results in saltatory conduction [local currents circuits]
so there is no need for depolarisation along the whole length of axon
describe the function of the myelin sheath and how it affects the speed of an action potential
- insulates the axon preventing an action potential from forming in parts of the axon covered in schwann cells
- results in saltatory conduction where the action potential jumps from one node of ranvier to the next
what is the affect of saltatory conduction in myelinated vs non myelinated neurones
triples the speed in myelinated neurones
state 3 factors that affect the speed of an action potential
myelin sheath
diameter of the axon
temperature
describe how the diameter of the axon affectts the speed of an action potential
greater the diameter of an axon, the faster the speed of conductance due to:
- greater diamater = smaller SA:V = smaller leakage and membrane potential is easier to maintina
- greater diameter = large SA = larger area for attachment of voltage-gated channels = faster diffusion = faster switch in potentiall difference
describe how temperature affects the speed of an action potential
causes an increased rate of diffusion therefore action potentials generated more rapidly
active transport of ions by NaK pump requires ATP from respiration which requires enzymes that is affected by temperature
gated channels and NaK pump will denature = control of ion distribution is lost and impulses cannot be conducted
state 5 ways the synapse’s structure has adapted to its function
- bulbous knob giving a large surface area: for attachment of transport proteins to allow rapid facilitated diffusion + active transport
- small diffusion distance: decreases time taken for an action potential to be created in the post-synaptic neurone
- mitochondria: ATP to provide energy for synthesis of neurotransmitter/vesicles/proteins
- RER: synthesis of transport proteins
- SER: synthesis of neurotransmitter and vesicles
explain how acetylcholine contributes to a synapse being unidirectional
- acetylcholine is released from the presynaptic side
- receptors in postsynaptic side
why are synapses important
- a single impulse can be transmitted to multiple neurones = single impulse can create multiple responses
- multiple impulses from multiple receptors can be passed to a single neurone = single response from multiple different stimuli
describe the transmission across a cholinergic synapse in the presynaptic neurone
- depolarisation of pre-synaptic membrane causes the opening of volted-gated Ca2+ channels, diffuse into pre-synaptic knob
- causes vesicles containing acetylcholine to move and fuse with the pre-synaptic membrane, releasing ACh into the synaptic cleft by exocytosis
describe transmission across a cholinergetic synapse in the postsynaptic neurone
- ACh diffuses across the synaptic cleft to bind to specific receptors on post-synaptic membrane causing Na+ channels to open
- Na+ diffuse into post-synaptic knob causing depolarisation, if the threshold is met, action potential is initiated
describe what happens to acetylcholine after synaptic transmission
- hydrolysed by acetylcholinesterase
- products are reabsorbed by presynaptic neurone
this is to stop overstimulation, if not removed it would keep binding to receptors causing depolarisation
describe temporal summation
- one pre-synaptic neurone releases neurotransmitter many times over a short period of time
- sufficient NT to reach threshold to trigger an action potential
describe spatial summation
- many pre-synaptic neurones share one post synaptic neurone
- collectively release sufficient neurotransmitters to reach threshold to trigger an action potential
describe inhibition by inhibitory synapses
inhibitory neurotransmitters hyperpolarise postsynaptic membrane:
Cl- channels open (diffuse in) + K+ channels open (diffuse out)
more Na+ required for depolarisation
reduces likelihood of threshold being met and action potential formation at post-synaptic membranes
describe how muscles work
they work in antagonistic pairs = pull in opposite directions
- one muscle contracts, pulling on the bone
- one relaxes
what is the advantage of muscles working in antagonistic pairs
the second muscle is required to reverse the movement caused by the first and it helps to maintain posture
describe the gross structure of skeletal muscle
made up of many bundles of muscle fibres packaged together, they are attached to bones by tendons
what do muscle fibres contain
muscle fibres are made up of long cylindrical cells containing many nuclei and myofibrils
- sarcolemma (cell membrane)
- sarcoplasm (cytoplasm)
- sarcoplasmic reticulum (endoplasmic reticulum)
- multiple nuclei
- many myofibrils
- many mitochondria
- T (transverse) tubles from sarcolemma folding inward
describe the ultrastructure of a myofibril
made of two types of long protein filaments arranged in parallel = myosin (thick) and actin (thin)
arranged in functional repeating units called sarcomeres = Z line, M line, H zone
what causes the characteristic banding pattern of myofibrils
characteristic banding pattern due to the arrangement of myofilaments
what is cross-striations
when muscle cells are composed of alternating light and dark bands
explain the banding pattern in I bands
light band containing only thin actin filaments
explain the banding pattern in A bands
dark bands containing thick myosin and some actin filaments
explain the banding pattern in the H zone
it contains only myosin
what does A in A band stand for
anisotropic
what does I in I band stand for
isotropic
why is summation by synapses important
low frequency of action potentials release insufficient neurotransmitter to exceed the threshold
define excitatory synapse
a synapse that increases the likelihood of an action potential in the post-synaptic membrane
explain the effect of drugs on a synapse
- stimulate the nervous system leading to more action potentials = similar shape to NT, stimulates the release of more NT, inhibits the enzyme that breaks down the NT = Na+ continues to enter
- inhibit the nervous system leading to less action potentials = inhibits the release of NT and blocks the receptors mimicking the shape of NT
name the gap between the pre-synaptic membrane and post-synaptic membrane
synaptic cleft
how does myosin and actin interact
the myosin head attaches to actin and bends
suggest why ATP is needed in the presynaptic membrane
active transport of ions, movement of vesicles
describe the roles of calcium ions in the contraction of a myofibril
- calcium ions diffuse into myofibrils from sarcoplasmic reticulum
- calcium ions bind to and cause movement of tropomyosin on the actin, changing the 3D tertiary structure
- exposure of the binding sites on the actin
- myosin heads attach to binding sites on actin
describe the role of ATP in the contraction of myofibril
- hydrolysis of ATP causes myosin heads to bend
- pulling the actin molecules
- attachment of new ATP molecule to each myosin head causes myosin heads to detach from actin sites
state how ATP is used in muscle tissue
- “resetting” of the myosin head back to it’s original position, ready for the next power stroke
- active transport of Ca2+ back into the sarcoplasmic reticulum for tropomyosin to move
- the active transport of Na+ out of the sarcoplasm in order to restore the normal potential difference of the muscle cell (‘resting potential’)
state the similarities between neuromuscular junctions and a cholinergic synapse
- release neurotransmitters that move by diffusion
- binding of receptors cause an influx of ions into the cell
- enzymes break down the neurotransmitter
state the differences between neuromuscular junctions and a cholinergic synpase
- synapse has sensory, intermediate and motor neurones involved, the junction only invovles motor neurons
- synapse
- ACh binds to receptors on sarcolemma not the post-synaptic membrane
- neuromuscular is excitatory but synapse is excitatory or inhibitory
- the action potential ends in the NJ but may be produed in the post-synaptic neuron in the cholinergic
- synpase links neurons to other neurons whereas NJ links neurons to muscle cells
what is a motor unit
each section of muscle that is depolarised by a motor end plat
how are muscle contractions synchronised and pwoerful
the motor neuron’s axon will divide into many dendrons and then into many motor end plates to form many neuromuscular junctions
what is a sarcomere
the unit of measurement for muscle tissue [distance btwn z lines]
describe what happens in neuromuscular junctions
- arrival of action potential at the motor end plate causes release of ACh into the neuromuscular junction
- Ach binds to the sarcolemma, causing muscle fibre to become depolarised
- depolarisation is propagated into muscle fibre t-tubles
- depolarisation of t-tubles causes Ca2+ gated channels to open into sarcoplasmic reticulum, releasing Ca2+ into the sarcoplasm
state the 3 ways of generating ATP
- aerobic respiration: large amounts of ATP but takes time
- anaerobic respiration: generates ATP during intense periods
- phosphocreatine: instanteneous generation of ATP during first few seconds of muscle contraction + only provides a few seconds worth of ATP but allows us to avoid a potentially life-threatening encounter
describe the role of phosphocreatine in muscle contraction
- source of inorganic phosphate to rapidly phosphorylate ADP to regerate ATP
ADP + phosphocreatine -> ATP + creatine
- runs out after a few seconds, used in short bursts of vigrous exercise
- anaerobic and alactic
what are slow twitch muscle fibres suited for
endurance activity e.g. running a marathon
what are fast twitch muscle fibres suited for
intense activity e.g. weight lifting
describe the features of slow twich muscle fibres
- adapted for aerobic respiration
- a rich blood supply to deliver oxygen and glucose
- contracts slowly over long periods of time
- possess a large store of myoglobin (bright red molecule that stores oxygen)
- common in leg muscles (calves) to maintain body in upright position
- numerous mitochondria
- less powerful contractions
describe the features of fast twitch muscle fibres
- adapted for anaerobic respiration
- high concentration of enzymes involved in anaerobic respiration
- common in arm muscle to do short bursts of exercise
- more powerful contractions
- thicker and more numerous myosin filmanets
- higher conc. of glycogen as delivery of glucose by the bloodstream is not fast enough
- store of phosphocreatine in order to repidly regenerate ATP from ADP
- contract rapidly over short periods of time
what are receptors also called
transducers (convert one form of energy into another form of energy)
describe the basic structure of a pacinian corpuscle
- lamellae
- sensory neurone ending
- sensory neurone axon
- myelin sheath
- gel
- stretch mediated sodium ion channel
what does the receptor convert the energy provided by the stimulus into
an action potential
state the 4 types of receptors
- mechanoreceptors
- photoreceptors
- baroreceptors
- chemoreceptors
explain the protective effect of a simple reflex
- rapid as only 3 neurones and a few synapses
- autonomic = doesn’t have to be learnt
- protects from harmful stimuli e.g. escapes predators
where is the pacinian corpuscle found
fingers feet and external genitalia
what type of receptor is a pacinian corpuscle
mechanoreceptor
how is an generator potential generated in a pacinian corpuscle
- mechanical stimulus e.g. force or pressure, deforms the lamellae and the stretch-mediated Na+ channels deform and allow the diffusion of Na+ into the sensory neuron
- greater pressure causes more Na+ channels to open and more Na+ to enter = depolarisation = generator potential
- when the generator potential reaches the threshold, it triggers an action potential
what does a pacinian copuscle illustrate
- receptor respond only to specific stimuli: pacinian corpuscle only responds to mechanical pressure
- stimulation of a receptor leads to the establishment of a generator potential = action potential sent when threshold is reached
what are the 4 features of a reflex reaction which means they confer a survival advantage
- innate: have them from birth
- involuntary
- fast
- protect us from harm
how are images focused
the cornea and lens refract light onto the retina
explain the differences in sensitivity to light for rods and cones in the retina
rods are more sensitive to light than cones
- several rods are connected to a single neurone vs each cone is connected to a single neurone
- spatial summation to reach a threshold to generate an action potential vs cones have no spatial summation
what is the fovea
where the majority of light is focused
what do rods allow us to do
to see in the dark
how do rods allow us to see in the dark
- rrhodopsin is broken down very easily by light = generator potentials can be produced in very low light conditions
- many rod cells are connected to a single sensory neurone vis single bipolar cell = retinal convergence
- rods can work together to produce enough neurotransmitters in v low light conditions to exceed threshold value for generator potential aka summation
why are cones needed
thay allow us to see in colour and higher detail
how do cones allow us to see in high detail and colour
- 3 cone cells: red green blue = trichromatic colour theory
- iodopsin is only broken down by high light intensities
- each cone cell is connected to its own bipolar cells + sensory neurone = high visual acuity
what does retinal convergence lead to and why
low visual acuity
- multoiple rods connected to single senroy neurone via single bipolar cell = brains cannot interpret exactly where light is coming from
describe the distribution of rods and cones
- 20:1 rods to cones in retina
- most cones found in fovea as this is where majority of light is focused = high visual acuity
– only rods are found at peripheries of retina = low light intensity
what is the difference in visual acuity for rods and cones in the retina
rods have lower visual acuity, cones have higher visual acuity
explain the differences in visual acuity for rods and cones in the retina
- several rods connected to a single neurone vs each cone connected to a single one
- several rods send a single set of impulses to brain (can’t distinguish btwn diff sources of light) vs cones send separate impulses to brain (can distinguish btwn diff sources of light)
what is the difference between in sensitiviy to colour for rods and cones and why
rods allow for monochromatic vision (1 type of rod + pigment)
cones allow for colour vision (3 types of cones rgb sensitive w diff optical pigments = absorb diff wavelengths = different combinations of cones = range of colour perception
what does it mean is the cardiac muscle is myogenic
contract and relax without receiving electrical impulses from the nerves
describe where you can find the Sinoatrial node (SAN)
wall of right atrium
describe where you can find the atrioventricular node (AVN)
border of right and left vventricle within the atria still
what is the Sinoatrial node known as
the pacemaker
where can you find the bundle of His
it runs through the septum (bit that separates left and right side of heart)
where can you find the purkyne fibres
in the wall of the ventricles
describe myogenic stimulation of heart and transmission of a subsequent wave of electrical activity
- SAN sends regular waves of electrical activity across the atria = atria contract stimultaneously
- non-conducting tissue btwn atria/ventricles prevents impulse passing directly to ventricles = prevents immediate contraction of ventricles
- waves of electrical activity reach AVN = delays impulse = atria fully contracts b4 ventricles contract
- AVN sends wave of electrical activity down bundle of His = conduct wave btwn ventricles to apex where it branches into purkyn tissue = ventricules contract stimultaneously from base up
where can you find chemoreceptors and pressure receptors
aorta and carotid arteries
where is the cardiac control found in the brain
medulla
what does the sympathetic nerve do
increases heart rate and force of contraction
what does vagus/parasympathetic nerve do
decreases heart rate
where does the parasympathetic and sympathetic nerve lead to
SAN
describe the roll of chemoreceptors + pressure receptors + autonomic nervous system + effectors in increasing heart rate (if you have low blood pressure)
- baroreceptors detect fall in blood pressure/chemoreceptors detect blood rise in blood CO2 conc or fall in blood pH
- send impulses to medulla/cardiac control centre
- sends more frequent impulses to SAN along sympathetic neurones
- more frequent impulses sent from SAN to AVN
- cardiac muscle contracts more frequently
- heart rate increases
describe the roll of chemoreceptors + pressure receptors + autonomic nervous system + effectors in decreasing heart rate (if you have high blood pressure)
- baroreceptors detect rise in blood pressure/chemoreceptors detect blood fall in blood CO2 conc or rise in blood pH
- send impulses to medulla oblongata/cardiac control centre
- sends more frequent impulses to SAN along parasympathetic neurones
- less frequent impulses sent from SAN to AVN
- cardiac muscle contracts less frequently
- heart rate decreases
what is the autonomic nervous system invovled in
involves the involuntary control of internal muscles and glands
what are the functions of the sympathetic nevour system
- stimulates effectors so speeds up any activity
- helps to deal with stressful situations
- heightens our awareness and allows more powerful musle contractions
what are the functions parasympathetic nervous system
- inhibits effectors so slows down activity
- controls activity in restful situations
- concerend with conserving energy, replenishing body reserves
how to calculate cardiac output
stroke volume x heart rate
how to calculate pulmonary ventilation
tidal volume x breathing rate
what is the typical heart rate of humans
~70bpm
what are the efffects of the sympathetic nervous sytem
- pupils dilate
- cardiac output increases
- bronchioles dilate
- pulmonary ventilation rate increases
- secretion of adrenaline + sweat
- blood diverted away from digestive system, towards skeletal muscle
what are chemoreceptors sensitive to
changes in pH which arise from amount of CO2 dissolved in the blood plasma
what are the effects of the parasympathetic nervous system
- pupils constrict
- cardiac output decreases
- bronchioles constrict
- pulmonary ventilation rate returns to resting rate
- blood diverted to digestive system
- sweat secretion inhibited
what forms when CO2 dissolves in the blood plasma
carbonic acid = lowers pH
what is homeostasis
the maintenance of a constant optimal internal environment through negative feedback mechanisms
the maintenance of a stable internal environment within restricted limits by physiological control systems, normally invovle negative feedback
what is negative feedback
a stimulus produces a response that acts to limit the effect of that stimulus
what is positive feedback
a reponse to a stimulus that acts to increrase the stimulus
why is it importance to maintain a stable core temperature if the temperature if too high
- H bonds in 3* of enzymes break
- enzymes denature = active sites change shape and substrates can’t bind = e/s complexes cannot form
why is it important to maintain stable core temperature if temperature is too low
- not enough kinetic energy so fewer e/s complexes form
why is it important to maintain stable blood pH
- above/below optimal pH = ionic and H bonds in 3* break
- enzymes denature = active sites change shape and substrates can’t bind = fewer substrate complexes
why is it important to maintain stable blood glucose concentration if it is too low
- not enough glucose for respiration
- less ATP produced
- active transport can’t happen
why is it important to maintain stable blood glucose concentration if it is too high
- water potential of blood decreases
- water lost from tissue to blood via osmosis
- kidneys can’t absorb all glucose = more water lost in urine = dehydration
describe the role of negative feedback in homeostasis
- receptors detect change from optimum
- effects respond to counteract change
- resuming levels to optimum/normal
describe vasoconstriction
- muscle in the arterioles near the surface of the skin contract and make the lumen smaller
- restricts blood flow to skin surface = limits amount of heat lost
describe vasodilation
- muscle in the arterioles relax making the lumen larger
- more blood flows to surface of capillaries + extremities increase heat loss
state the physiological responses of thermoregulation
- vasodilation & vasoconstriction
- sweating
- piloerection
- shivering
describe piloerection
contraction of hair erector muscles which raises the body’s hairs = thicker layer of insulating air/water to be trapped against the skin = improves insulation
what is the role of the pancreas in blood glucose regulation
has islets of langerhans which secretes either insulin [beta] or glycogen [alpha]
define glycogen
a carbohydrate storage molecule found in animal livers and muscle tissue
define glucagon
a hormone that stimulates the conversion of glycogen to glucose via the second messegener model
define adrenaline
a hormone that stimulates the conversino of glycogen to glucose via the second messenger model
define insulin
a hormone that stimulates the conversion of glucose into glycogen via the second messenger model
define glycogenolysis
the conversion of glycogen to glucose when blood levels are lower than normal
define glycogenesis
the conversion of excess glucose to glycogen when blood levels are higher than normal
define glyconeogenesis
the conversion of a non-carbohydrate molecule to glucose this occurs if all glycogen has been converted to glucose and your body still requires more glucose
define glycolysis
the splitting of glucose into two 3 carbon molecules releasing atp
what is hypoglycaemia
when the blood glucose concentration is too low
what is hyperglycaemia
when the blood glucose concentration is too high
why is it important to maintain a stable blood glucose concentration when its too low
not enough glucose for respiration = less ATP produced = AT can’t happen = cell death
why is it important to maintain a stable blood glucose concentration when it is too high
water potential of bblood decreases = water lost from tissue to blood via osmosis = kidneys can’t absorb all glucose = more water lost in urine causing dehydration
describe the role of neggative feedback in homeostasis
- receptors detect change from optimum
- effectors respond to counteract change
- returns lelvels to optimum/normal
describe positive feedback
receptors detect change from normal, effectors respond to amplify change = produce greater deviation from normal
explain the importance of conditions being controlled by separate mechanisms involving negative feedback
departure in different directions from the original state can all be controlled = greater degree of control
define hormone
a chemical messenger secreted by glands that travels through the bloodstream and bind to target cells
describe the second messenger model
- adrenaline/glucagon binds to a transmembrane protein receptor within the cell-surface membrane of a liver cell
- the binding of the hormone causes the protein to chnge shape on the inside of the mmebrane
- this changes the protein shape = activation of a membrane-bound enzyme adenyl cyclase
- adenyl cyclase converts atp into cyclic AMP [cAMP]
- the active protein kinease catalyses the hydrolysis of glycosidic bonds in a glycogen molecule
- glucose released from the hydrolysis reaction leaves the liver cell and enters the blood via FD and carrier protein
what does the second messenger model do
increase permeability of liver cells
suggest an advantage of the second messenger model
amplifies signal from hormone, each hormone will stimulate production of many molecules of second messenger [cAMP] which can activate many enzymes for rapid increase in glucose
what are the signs and symptoms of diabetes
- high blood glucose conc
- presence of glucose in urine
- urinate excessively
- weight loss
- blurred vision
- tiredness
- increased thirst and hunger
- genital itching or regular thrush episodes
what causes diabetes type 1
the body is unable to produce insuline due to an autoimmune response - attacks b cells of islets of langerhans
what causes diabetes type 2
glycoprotein receptors on body cells are losing/have lost their responsiveness to insulin, or an inadquete supply of insulin from the pancreas
how is diabetes type 1 treated
injections of insulin 2/4 times a day. insulin dose must match the glucose intake. this is moniitored using biosensors
how is diabetes type 2 treated
drugs to stimulate insulin production/slow down rate of absorption of glucose
state 3 factors
core temperature, blood pH, blood glucose concentration
what is diabetes
a metabolic disorder caused by an inability to control blood glucose concentration due to a lack of the hormone insulin/repsonse to insulin
state how insulin reduces blood glucose concentration
- causing more glucose channels to be inserted into the cell membrane = increase uptake of glucose by muscle cells
- increases rate of respiration = more glucose is used
- activates enzymes involved in the conversion of glucose to glycogen [glycogenesis]
- causes excess glucose to be concerted to fat
where is insulin secreted
beta cells in the islets of langerhans
where is glucagon secreted
alpha cells in the islets of langerhans
state how glucagon increases blood glucose concentration
- attaches to receptors on surface of target cells e.g. liver and muscle
- activating enzymes involved in the conversion of glycoen to glucose [glycogenolysis]
- activating enzymes invovled in the conversion of glycerol and amino acids into glucose [ gluconeogenesis]
0 causes body to use more fatty acids in respiration
define diabetes mellitus
medical condition where a person is unabl to control their blood glucose concentration
