5.1.5 Plant and animal responses Flashcards
CNS made up of and role
central nervous system = brain + spinal cord
coordinating response
brain mostly made out of
non-myelinated relay neurones (grey matter)
spinal cord mostly made out of
myelinated (white) and non-myelinated (grey) relay neurones
PNS made out of and role
sensory and motor neurones
connects receptors to CNS and to effector to bring about response
sensory nervous system structure
connects receptor to CNS
sensory neurones enter spinal cord at dorsal root (where cell body is also)
short axon connects to relay neurones in CNS
motor neurones structure and role
connects CNS and effectors
split into autonomic and somatic nervous systems
somatic nervous system features and role
motor neurones under voluntary control
e.g. controlling skeletal muscles
mostly myelinated neurones (fast)
single motor neurones connect CNS and effectors
autonomic nervous system features and role
motor neurones under involuntary control
mostly non-myelinated neurones (slower)
at least 2 neurones between CNS and effector
examples of actions controlled by autonomic nervous system
controlling glands cardiac muscle smooth muscles in gut eyes blood vessels airways
ganglia obvious features
swelling
sympathetic vs parasympathetic nervous systems in general
sympathetic more active in times of stress whereas parasympathetic in times of rest
how autonomic nervous system is split
sympathetic and parasympathetic
antagonistic to each other
balance depending on internal conditions and stress to bring about appropriate response
sympathetic nervous system features
short preganglionic neurone ganglia near CNS many nerves leave CNS noradrenaline is neurotransmitter active in fight/flight or stress
parasympathetic nervous system features
long preganglionic neurone ganglia near organs few nerves leave CNS then split up to go to effectors acetylcholine is neurotransmitter active in calm
human brain 4 main parts
cerebrum
cerebellum
hypothalamus + pituitary complex
medulla oblongata
cerebrum function
organises most higher thought process e.g.
conscious thought/actions
memory
emotions
intelligence, reasoning, judgement, decision making
cerebellum function
coordinates balance and fine movement e.g. tensioning muscles for playing music, judging positioning of objects while moving
complex nervous pathways become stronger with practice (becomes “second nature”)
hypothalamus structure and role
organises homeostatic responses and control physiological processes
e.g. temperature regulation and osmoregulation
contains own receptors, osmoreceptors, thermoreceptors
regulates feeding and sleeping patterns
medulla oblongata function
coordinates many autonomic responses controls cardiac muscles and smooth muscles by sending action potentials through autonomic nervous system regulates many vital processes e.g. cardiac centre (regulates heart rate) vasomotor centre (regulates circulation + blood pressure) respiratory centre (controls rate + depth of breathing) centres receive sensory information and coordinate vital functions through negative feedback
cerebrum structure
2 cerebral hemispheres connected via major tracts of neurones called corpus callosum
outermost layer consists of thin layer of nerve cell bodies called cerebral cortex
cerebral cortex structure
sensory areas
association areas
motor areas
how cerebrum and cerebellum connected
the pons
pituitary gland structure and role
posterior lobe linked to hypothalamus by specialised neurosecretory glands
secretes hormones (produced in hypothalamus) into blood
anterior lobe produces own hormones (for physiological processes e.g. stress), released in response to releasing factors produced by hypothalamus
sensory area function
receive action potentials from sensory receptors, size related to sensitivity of area to inputs received
association area function
compares and interprets sensory inputs with previous experiences to judge appropriate response
motor area function
send action potentials to effectors, size related to complexity of movements needed in parts of body, left side of brain controls effectors on right side and vice versa
knee jerk reflex definition
reflex action that straightens leg when tendon below kneecap is tapped
reflex action definition
response that doesn’t involve any processing by the brain
why reflex occur
need to be quick for survival
e.g. get out of danger, prevent damage, maintain balance
nervous pathway of reflex actions
sensory neurone -> relay neurone -> motor neurone
cranial reflex definition
reflex where nervous pathway passes through part of the brain but doesn’t involve any thought processes
reflex arc definition
receptor and effector are in the same place
blinking stimulus examples
foreign object touching eye (corneal reflex)
sudden bright light (optical reflex)
loud sounds
sudden movements close to eye
optical reflex
protects light-sensitive cells of retina from damage
stimulus detected by retina
reflex mediated by optical centre in cerebral cortex
slower than corneal reflex
corneal reflex
mediated by sensory neurone from cornea, entering pons
synapse connects sensory to relay neurone, carrying action potential to motor neurone
motor neurone passes back out of brain to facial muscles, causing eyelids to blink
short and direct pathway so very rapid
why corneal reflex can be overridden
sensory neurone involved in corneal reflex also passes action potentials to myelinated neurones in pons
these neurones carry a.p. to sensory area in cerebral cortex
informs higher centres of brain that stimulus has occurred
allows reflex to be overriden by conscious control
myelinated neurones carry a.p. faster than non-myelinated neurones
how knee jerk reflex works
muscle at bottom of thigh contracts to straighten leg
muscle spindle (specialised stretch receptors) detect increase in length of muscle
if unexpected, reflex causes contraction of same muscle to remain balanced
why knee jerk reflex is strange
nervous pathway only involves 2 neurones
sensory neurone -> motor neurone
much quicker as 1 less synapse
spinal reflex definition
nervous pathway passes through spinal cord rather than through brain
why brain cannot inhibit knee jerk reflex
no relay neurone to carry a.p. to brain
sensory neurone stimulates motor neurone directly
insufficient delay to enable inhibition by brain sending inhibitory action potentials to synapse before motor neurone is stimulated
fight or flight response physiological changes
+heart rate and blood pressure (increased blood flow, more O2 and glucose to respiring cells for more respiration)
+breathing rate and depth (faster rate of gas exchange = more O2 in blood = more respiration)
arterioles to skin+digestive system vasoconstrict (less blood to skin and DS, not needed in response)
arterioles to muscles vasodilate (more blood for more respiration, needed in response)
pupils dilate (more light into retina to see better)
+glycogenolysis (more glucose released into blood from liver, more respiration)
+metabolic rate
erector muscles in skin contract (make hairs stand up to look bigger, potentially more intimidating, prevent conflict)
role of brain in fight or flight response
receptor sense threatening stimulus
a.p. sent to sensory centres in cerebrum
then association centres to coordinate response
cerebrum stimulated hypothalamus in response to threat
hypothalamus stimulates sympathetic nervous system + anterior pituitary gland
role of sympathetic nervous system in fight or flight response
increases activity of effectors via nervous impulses (more rapid response)
stimulates adrenal medulla to release adrenaline (which brings about responses in effectors) for longer response
action of adrenaline
adrenaline acts as first messenger (travels through blood to target cells)
binds to receptors on cell surface membrane of target cells
binding causes a G-protein on membrane to activate adenyl cyclase (enzyme)
this converts ATP into cAMP (cyclic AMP)
brings about effect in cell
role of anterior pituitary gland in hypothalamic-pituitary-adrenal cortical axis
hypothalamus secretes corticotropin-releasing hormone (CRH)
causes release of adrenocorticotropic hormone (ACTH) into blood
stimulates adrenal cortex to release corticosteroids e.g. cortisol
role of anterior pituitary gland in hypothalamic-pituitary-thyroid axis
thyrotropin‐releasing hormone (TRH) causes the release of thyroid‐ stimulating hormone (TSH) into blood stimulates the thyroid gland to release more thyroxine
role of anterior pituitary gland in hypothalamic-pituitary axis in general
hypothalamus secretes releasing hormones into blood to pituitary gland
stimulates release of tropic hormones
cortisol effect
increases metabolism of carbohydrates -> glucose
increases blood glucose levels
increases blood pressure and suppresses immune system
thyroxine effect
increases metabolic rate
makes cells more sensitive to adrenaline
how heart rate is controlled
cardiovascular centre in medulla oblongata sends nervous impulses to SAN via autonomic nervous system to alter the frequency of waves of excitation (changes heart rate)
how SAN alters heart rate
heart beat always same length of time
heart rate increased by higher frequency and larger stroke volume
how heart rate increased during exercise method
produce more CO2
more carbonic acid formed when reacting with water
more H+ which reduces pH
lower pH detected by chemoreceptors in carotid arteries, aorta and brain
increased action potential frequency in sensory neurone to medulla oblongata
cardiovascular centre sends nervous impulse to SAN via sympathetic nervous system
noradrenaline released at SAN
causes heart rate to increase
other ways heart rate is increased examples
hormones from adrenal medulla bind to adrenoreceptors on cardiac muscle
stretch receptors detect movement in muscles, sends impulses to cardiovascular centre
heart rate increases
why heart rate is increased
faster exchange of oxygen and glucose
faster removal of CO2 and other waste
decreasing heart rate when stopping exercise method
conc. of CO2 decreases (pH rises)
higher pH detected by chemoreceptors in carotid arteries, aorta and brain
decreased ap. frequency in sensory neurone to medulla oblongata
cardiovascular centre sends fewer nervous impulses to SAN via parasympathetic nerve
heart rate decreases
decreasing heart rate when increase in blood pressure method
monitored by baroreceptors in carotid sinus
if b.p. too high, sensory nerve carries signal to medulla oblongata
cardiovascular centre sends nervous impulses to SAN via vagus nerve (parasympathetic)
acetylcholine (neurotransmitter) released at SAN
cause heart rate to decrease
blood pressure to decrease
muscle cell grouping
group together to form fibres which contract and relax
groups arranged in antagonistic pairs (one contracts as one elongates)
skeletal muscle function and location
attached to bones
contract to move bones
cardiac muscle location and function
found in heart
contract to make the heart beat to pump blood
smooth (involuntary) muscle location and function
walls of bronchi/bronchioles, blood vessels and organs (e.g. small intestine, stomach)
control diameters of arteries/arterioles, bronchi/bronchioles
peristalsis (and passing of other substances)
cardiac muscle structure
cells branch to ensure electrical stimulation spreads evenly over the walls so contraction is 3D
cells joined by intercalated discs to ensure synchronised contraction
muscles striated in appearance
do not easily fatigue
smooth muscle structure
controlled by autonomic NS
contract slowly
non-striated
longitudinal cells arranged in circular shapes around lumen
skeletal muscle structure
controlled by somatic NS
striated, cylindrical shaped cells
muscle cells join up to make long muscle fibres that share sarcoplasm (cytoplasm, contains lots of mitochondria) and sarcolemma (membrane)
between myofibrils are mitochondria, sarcoplasmic reticulum (Ca^2+ store), glycogen granules
short striated section of myofibrils called sarcomeres made out of actin+myosin filaments
structure of sarcomeres
thin filaments of light bands (I bands) of striations
thin + thick filaments overlapping make up dark bands (A bands)
area in the middle of dark band that has no over lap (H zone) with dark M line in midle
sliding filament hypothesis and contracted sarcomere under electron micrograph
shorter I band, shorter H band, Z discs get closer together, sarcomere shorter
A band remains the same
stimulation of contraction method
a.p. arriving at end of axon open calcium ion channels
allows Ca^2+ ions to flow into axon tip
vesicles of acetylcholine move towards and fuses with the cell surface membrane
acetylcholine diffuses across gap and bind to receptors on muscle fibre
sodium ion channels open and Na^+ ions enter muscle fibre, causes depolarisation
wave of depolarisation creates a.p. that passes along sarcolemma and down transverse tubules
a.p. reaches sarcoplasmic reticulum, causing it to release Ca^2+ ions
causes muscle contraction
thickness of filaments
myosin = thick filaments actin = thin filaments
thin filament structure
consists of 2 actin subunits and tropomyosin molecules twisted around each other attached to troponin
anchored to Z-disks
troponin structure
globular made up of 3 polypeptides 1 binds to actin 1 to tropomyosin 1 to calcium ions when they are available
thick filament structure
bundle of myosin molecules
each have 2 protruding heads at each end of molecule
heads are mobile and bind to actin when binding sites are exposed
anchored to M-line
muscle contraction model answer
action potential passes along sarcolemma and down transverse tubules into muscle fibre
action potential carried to sarcoplasmic reticulum, released calcium ions into sarcoplasm
calcium ions bind to troponin
causes troponin to change shape, pulls tropomyosin aside and exposes binding sites to actin
myosin heads bind to actin to form actin-myosin cross-bridges when ATP is present
causes myosin head to move and actin filament to slide past the stationary myosin filament (power stroke)
ADP and Pi released from myosin during power stroke
ATP attaches to myosin head and causes it to detach from actin
ATP hydrolysed by ATPase on myosin head into ADP and Pi, provides energy to return myosin head to original position
myosin can reattach further up actin and repeat
when stimulus stops, calcium ions actively transported back into sarcoplasmic reticulum
calcium concentration falls until troponin and tropomyosin move back to cover binding sites
role of ATP during contraction
supplies energy for contraction
during power stroke, ADP and Pi released from myosin head
new ATP molecule attached to myosin head, breaks cross-bridge
ATP is hydrolysed, releasing energy for myosin head to return to original position and repeat contraction mechanism further along actin filament
maintaining supply of ATP
ATP available in muscle tissue needs to be regenerated very quickly to allow continued contraction via:
aerobic respiration in mitochondria (limited by delivery of oxygen to muscle tissue during intense activity)
anaerobic respiration in sarcoplasm (releases smaller amounts of ATP, leads to production and build up of lactic acid, toxic and causes fatigue)
creatine phosphate in sarcoplasm (reverse store of phosphate groups that can bind to ADP to form ATP rapidly, enzyme required, enough to support muscular contraction for 2-4 more seconds)
enzyme required for creatine phosphate
creatine phosphotransferase
why plant need to respond to their environment
avoid abiotic stress
maximise photosynthesis (obtain more sunlight/water)
germinate in suitable conditions
respond to and protect against predation or invasion by pathogens
what plants respond to in environment
abiotic stress
tropisms
avoid herbivory/grazing
how plants respond to abiotic stresses (environmental)
higher temperatures = more waxy layer
very windy = more lignification of xylem vessels
drought = root growth slows, stomata close (abscisic acid)
how plants respond to tropisms
geotropism/gravitropism (roots grow towards soil to obtain more minerals and water)
hydrotropism (roots grow towards water to absorb more water required for photosynthesis)
phototropism (shoots grow towards sunlight to maximise sunlight absorbed for photosynthesis)
thigmotropism (grow up and around structures for support + anchor and obtain reactants for photosynthesis)
chemotropism (pollen grows towards ovule)
how plants respond to herbivory/grazing
thigmonasty (e.g. folding in response to touch in Mimosa pudica) chemical defences (tannins, alkaloids, pheromones)
tannins
makes plant taste bad
defends roots against pathogen
alkaloids
make tips of roots and shoots and flowers taste bitter
pheromones in plants
can be produced when one leaf is eaten
communicates with other leaves to produce chemical defences
cytokinins effect
promote cell division
delay leaf senescence
overcome apical dominance
promote cell expansion
abscisic acid effects
inhibits seed germination and growth
causes stomata closure when plant is stressed by low water availability
inhibit lateral bud growth (promote apical dominance)
auxins effects
e.g. IAA (indole-3-acetic acid)
promote cell elongation
promotes apical dominance (keeps abscisic acid levels high)
inhibit leaf abscission (leaf fall) by reducing ethene production
gibberellins effects
promote seed germination and growth of stems
ethene effects
promotes fruit ripening and leaf abscission
nastic movement
plant movement that occurs in response to environmental stimuli but the direction of response is not dependent on direction of stimulus
leaf abscission definition
leaf fall
leaf senescence definition
ageing of leaves
chlorophyll degrades, causes leaves to change to autumnal colour
apical dominance definition
inhibits lateral buds growing further down the shoot
causes shoots and buds to grow upwards
plant hormone action
made in many plant tissues
act on wide variety of target tissues
move in xylem vessels or phloem tissue by mass flow up and down plant
then diffuse or active transport from cell to cell
binds to complementary-shaped receptors on plasma membrane
binding causes series of enzyme-controlled reactions (sometimes causing genes to be switched on/off) that brings about response
differences between plant and mammalian hormone action
made in endocrine glands vs made in many tissues
move in blood vs move in xylem/phloem, from cell to cell
act on few/specific target tissues vs add on most tissues, act in cells where produced
act more rapidly vs acts more slowly
similarities in plant and mammalian hormone action
binds to complementary-shaped receptor
causes cascade of events / enzyme reactions
may involve switching on/off of genes
only present in small quantities to cause effect
may have effect on more than one location/tissue
may involve interaction with more than one hormone
auxin experiment method
take 15 seedlings, cut off tip and measure them
to 5 seedlings, cover end of tip with lanolin (wax) (A)
to another 5, cover end with lanolin infused with IAA
leave final 5 untreated (C)
after 3 days measure them
both A and C needed as lanolin alone is not causing effect and only IAA causes effect
height doesnt matter by measuring % change in height
how to prove phototropism of plants method
collect 20 seedlings
mark stems every 2mm
plant 10 in one pot and 10 in another
set up lamps so one pot (A) gets light from all direction and the other (B) only gets light from one side
leave to grow for 4 days
measure distances between each mark and calculate mean distances for A and B for both shady and light sides
tropism definition
plants responding to stimuli via growth
response is directional
elongation method
auxins produced at apex of shoot
diffuse down shoot to zone of elongation
binds to receptors on cell surface membrane of cells
causes H+ ions to be actively transported into cell wall
low pH causes wall-loosening enzymes to catalyse breaking of bonds in cellulose
walls become more flexible
water enters cell, flexible wall allows cell to elongate
phototropism method
auxins produced at apex of shoot
more phototropin enzymes activated on side with more light shining on it
phototropin enzymes cause PIN proteins to transport more auxins to shaded side
cells on shaded side of shoot elongate more quickly
shoot bends towards light
mica vs gelatin
mica is impermeable (doesn’t allow diffusion)
gelatin is permeable (allows diffusion)
what Darwin’s work showed about phototropism
tip was responsible for phototropism
what Boysen-Jensen’s work showed about phototropism
substance responsible for phototropism
auxins must pass from the tip down to cause response
what Went’s work showed about phototropism
showed chemical (auxin) from tip causes response effect can be caused artificially if chemical was allowed to diffuse into agar block
geotropism of plants
plant shoots show negative geotropism (up and against from gravity)
plant roots show positive geotropism (down and with gravity)
showing geotropism experiment
collect 10 seeds
embed 5 in one Petra dish of moist cotton wool
other 5 in another
place one group (A) in the klinostat, allow to turn very slowly for 4 days
place B into klinostat, without turning
observe results
auxin mechanism for geotropism
auxins produced at apex (tip) of shoot
if roots lying flat, auxin collects on lower side
auxin inhibits cell elongation in roots
upper side cells elongate, so root bends downwards
where acetylcholine receptors are found
postsynaptic membrane in neuromuscular junction
auxins commercial uses
weedkiller (promotes rapid shoot growth, plant can’t support itself, falls and does)
cuttings of plants dipped in rooting powder (promotes root growth)
micropropagation
make seedless fruits
