5.5 plant and animal responses Flashcards
define tropic
directional response
Define nastic
Non directional response
Why do plants respond to stimuilus
predation
growth
increase photosynthesis
What are three chemical defenses
tannins
alkaloids
pheromones
Describe tannins
toxic to microorganisms and larger herbivores and make the leaf taste bad
Describe alkaloids
feeding deterrent as they taste bitter
Describe pheromones
chemicals which released by one individual can affect the behaviour or physiology of another
What are the different types of tropic response
Phototropism
geotropism
chemotropism
thigmotropism
Define phototropism
Shoots grow towards light enabling them to photosynthesise
Define geotropism
Roots grow towards pull of gravity anchoring them in soil and helps them take up water
Define chemotropism
On a flower pollen tubes grow down the style attracted by chemicals in the ovary where fertilisation takes place
Define thigmotropism
Shoots of climbing plants such as ivy wind around other plants or solid structures to gain support
Give an example of a nastic response
thigmonastic - response to touch
why are plant hormones called hormones if they dont come from a gland
The are chemical messengers specific to a tissue and receptor and initiate a response
What is the action of cytokinins
promote cell division and expansion
delay leaf senescence
overcome apical dominance
What is the action of abscisic acid
inhibit seed germination and growth
cause stomatal closure when water availability is low
What is the action of auxins IAA
Promote cell elongation
inhibit growth of lateral shoots
inhibit leaf fall
What is the action of gibberellins
promote seed germination and growth of stems
Give the action of ethene
Promote fruit ripening
How do hormones move around the plant
active transport
diffusion
mass flow in sap or xylem vessels
Define apical dominance
inhibition of lateral buds further down the shoot by chemicals produced by the apical bud at the tip of a plant shoot
Describe the investigation into apical dominance
Auxin was applied to a cut shoot and lateral buds did not grow then auxin transport inhibitor was applied below the apex and lateral buds grew
The conclusion was that low levels of auxin promotes growth of lateral buds
What other chemicals are involved in apical dominance
Abscisic acid inhibits bud growth and high auxin levels keep abscisic acid levels high
Cytokinins promote bud growth and candirectly overcome apical dominance - when the apex is removed cytokinins spread around more evenly in the plant rather than all being in the tip
What is the relationship between gibberellins and pea plants
Higher levels of GA1 in tall pea plant were homozygous dominant for the Le allele whereas the short plants where homozygous recessive
The Le gene was found to produce the enzyme which converted GA20 to GA1
What is the action of gibberellins in seed germination
When the seed absorbs water the embryo releases gibberellin which stimulates the production of amylase which breaks down starch into glucose for respiration
What did Darwins experiments confirm
The shoot tip was responsible for phototropic responses
What experiments did darwin do
Cut tip
cover tip with opaque and transparent caps
cover base of shoot
What did Boyson-Jensen confirm
That water and solutes need to be present to move auxin from the shoot tip for phototropism to happen
What experiments did boyson - jensen do
Slice the tip of plant shoot and place agar block - lent to light
slice the tip of plant shoot and place mica - grew straight
what is the effect of auxin in shoot growth
inhibits root growth
what are some commercial uses of auxins
used to prevent leaf and fruit drop and promote flowering
producing seedless fruit
used as herbicides by promoting shoot growth and causing the plant to buckle
What are some commercial uses of cytokinins
they delay leaf senescence and used to prevent yellowing of lettuce leaves
used in tissue culture to help mass produce plants by promoting shoot and bud growth from small pieces of tissue taken from the parent plant
What are the commercial uses of gibberellins
fruit production
brewing
sugar production
plant breeding
How are gibberellins used in fruit production?
they can delay senescence in citrus
they can act with cytokinins and improve apple shape
can make grape stalks elongate making grapes less compact and bigger
How are gibberellins used in brewing
adding gibberellin can speed up the process of when barley seed produce amylase enzymes from the aleurone layer so more maltose is produced
malt is needed to make beer
How are gibberellins used in sugar production?
spraying sugar canes with gibberellins stimulates growth between the nodes which is useful as sugar can stores sugar in the cells of the internodes making more sugar available from each plant
How are gibberellins used in pant breeding
gibberellins can speed up the process of conifer trees becoming reproductively active by inducing seed formation on young trees
spraying with gibberellin synthesis inhibitors can make flowers short and stocky such as poinsiettas
What are some commercial uses of ethene
speeding up fruit ripening in apples tomatoes and citrus fruit
promoting fruit drop in cherries
make cucumbers not bitter by reducing chance of self pollination
promoting lateral growth in some plants
define the autonomic nervous system
part of the nervous system responsible for controlling the involuntary motor activities of the body
Define the central nervous system
the central part of the nervous system composed of the brain and spinal cord
Define the peripheral nervous system
the sensory and motor nerves connecting the sensory receptors and effectors to the CNS
Define the somatic nervous system
the motor neurones under conscious control
What are the somatic and autonomic nervous systems part of
They branch from the peripheral nervous system into the motor system and then the autonomic and somatic nervous systems
What can the autonomic nervous system be further split into
sympathetic and parasympathetic
efine sympathetic
fight or flight and prepares the body for activity
Define parasympathetic
rest and digest - conserves energy
how does the sympathetic and parasympathetic systems differ in terms of ganglia
s - ganglia just outside CNS
p - Ganglia in the effector tissue
how does the sympathetic and parasympathetic systems differ in terms of pre and post ganglionic neurones
s - short pre-ganglionic neurones and long post-ganglionic neurones
p - long pre-ganglionic neurones and short post-ganglionic neurones
how does the sympathetic and parasympathetic systems differ in terms of neurotransmitters
s - noradrenaline
p - acetylcholine
What are the 4 main parts of the human brain
cerebrum - higher thought process - memory
cerebellum - movement and balance
hypothalamus and pituitary - organises homeostatic response
medulla oblongata - coordinates autonomic responses
describe the structure of the cerebrum
has two cerebral hemispheres connected via a major tract of neurones called the corpus callosum and the outermosst layer consists of a thin layer of nerve cell bodies called the cerebral cortex
what are the functions of the cerebrum
conscious thought
conscious actions
emotional responses
intelligence, judgement and reasoning
what three areas is the cerebral cortex subdivided into
sensory areas
association areas
motor areas
what is the sensory area in the cerebral cortex responsible for
receiving action potentials indirectly from sensory receptors and the size of the regions are related to the sensitivity of the area
what is the association area in the cerebral cortex responsible for
compare sensory inputs with previous experience and judge an appropriate response
what is the motor area in the cerebral cortex responsible for
send action potentials to various effectors and the sizes of the regions are related to the complexity of the movements needed
What is the function of the cerebellum
involved with balance and the co-ordination of movement and fine control of muscular movement
e.g. tensing correct muscles when playing a musical instrument
Where is the conscious decision to contract muscles initiated
cerebral cortex
How are the cerebrum and the cerebellum connected
by the pons
what is the action of the hypothalamus and pituitary complex
controlling homeostatic mechanisms in the body
how does the hypothalamus control homeostatic mechanisms in the body
it contains its own sensory receptors and acts by negative feedback to maintain a constant internal environment
Give some examples of how the hypothalamus controls homeostatic mechanisms
temperature regulation - the hypothalamus detects changes in core body temperature and receives sensory input from temperature receptors in the skin and will initiate responses
osmoregulation - osmoreceptors in hypothalamus monitor water potential of blood and osmoregulatory centre initiates the response
how are the hypothalamus responses mediated
via the pituitary gland
How does the pituitary gland act
In conjunction with the hypothalamus
What are the two lobes of the pituitary gland
posterior lobe
anterior lobe
Describe the function of the posterior lobe in the pituitary gland
linked to the hypothalamus by neurosecretory cells
hormones manufactured in hypothalamus such as ADH pass down neurosecretory cells and are released into the blood via the pituitary gland
describe the function of the anterior lobe in the pituitary gland
produces its own hormones which are released into the blood in response to releasing factors (type of hormone) produced by the hypothalamus
what do the hormones from the anterior lobe control
a number of physiological processes including response to stress, growth, reproduction and lactation
What are the actions of the medulla oblongata
controls non skeletal muscle - cardiac and involuntary smooth muscle - by sending action potentials through the autonomic nervous system
What centres does the medulla oblongata contain
cardiac
vasomotor
respiratory
What is the cardiac centre in the medulla oblongata responsible for
regulating heart rate
What is the vasomotor center in the medulla oblongata responsible for
regulating circulation and blood pressure
What is the respiratory centre in the medulla oblongata responsible for
controlling rate and depth of breathing
How do the centers in the medulla oblongata coordinate vital functions
they receive sensory information and coordinate vital functions by negative feedback
What is a reflex action
responses to changes in the environment that do not involve any processing in the brain to coordinate the movement
what is the blinking reflex
causes temporary closure of the eyelids to protect them from damage
What type of reflex is the blinking reflex
cranial as it passes through part of the brain
Why may blinking be stimulated
foreign object
sudden bright light
loud sounds
Describe the corneal reflex
this reflex is mediated by a sensory neurone from the cornea which enters the pons then relay neurone and an action potential passes down the motor neurone causing the eye to blink
What type of reflex is a corneal reflex
cranial reflex
How can the corneal reflex be inhibited
e.g. contact lenses wearers can prevent the reflex and not blink
the myelinated neurones carry inhibitory action potentials faster than the non-myelinated neurone can carry an action potential so the inhibitory action potentials can prevent the formation of an action potential in the motor neurone
describe optical reflexes
protects the light sensitive cells of the retina from damage
Describe the knee jerk reflex
unexpected stretching of muscle spindles causes a contraction of the quadriceps to straighten the leg
what kind of reflex is the knee jerk
spinal reflex
What is different about the neuronal pathways of a knee jerk reflex
no relay neurone
Why can the knee jerk reflex not be overridden
lack of relay neurone means the action potential cannot be inhibited as it relies on myelinated neurones carrying inhibitory action potentials to the synapse before the motor neurone is stimulated there is insufficient delay to enable inhibition
Why do we have reflexes
they have survival value
How does the brain coordinate responses to the effector
action potentials in the somatic nervous system
action potentials in sympathetic and parasympathetic parts of the autonomic nervous system
release of hormones via hypothalamus and pituitary gland
What are some physiological changes caused by adrenaline
pupils dilate
heart rate and blood pressure increase
blood glucose levels rise
ventilation rate and depth increase
metabolic rate increases
How does the cerebrum use sensory input to coordinate a response
inputs feed into the sensory are in cerebrum
cerebrum passes signals to association centres
if a threat is recognised the cerebrum stimulates the hypothalamus
hypothalamus increases activity in sympathetic nervous system and stimulates release of hormones from anterior pituitary gland
Describe the role of the sympathetic nervous system in the fight or flight response
hypothalamus activates sympathetic nervous system and this either activates the adrenal medulla causing a secretion of adrenaline into the bloodstream or impulses activate glands and smooth muscles
this combines with neural activity to constitute a fight or flight response
Describe the action of the anterior pituitary gland in the fight or flight response (CRH)
The hypothalamus secretes releasing hormones to stimulate the pituitary gland
corticotropin-releasing hormone (CRH) from the hypothalamus causes the release of adrenocorticotropic hormone (ACTH) which passes around the blood stream and stimulates adrenal cortex to release a number of corticosteroid hormones e.g. cortisol which metabolises carbohydrates
Describe the action of the anterior pituitary gland in the fight or flight response (TRH)
Thyrotropin-releasing hormones (TRH) causes the release of thyroid stimulating hormone (TSH) which stimulates the thyroid gland to release more thyroxine which increases metabolic rate and makes cells more sensitive to adrenaline
What are the three types of muscle
involuntary - smooth
involuntary - cardiac
voluntary - skeletal
what kind of pairs are muscles arranged in
antagonistic pairs - one contracts the other relaxes
where is smooth muscle found
found in the walls of tubular structures such as blood vessels and the bronchioles
describe smooth muscle
consists of individual cells tapered at both ends
each cell contains a nucleus and bundles of actin and myosin
What is smooth muscle contraction controlled by
the autonomic nervous system
describe cardiac muscles
long fibres which branch to form cross bridges and the cells are joined by intercalated disks
What is the purpose of intercalated discs
specialised cell surface membranes fused to produce gap junctions that allow free diffusion of ions between cells
Describe how the structure of the cardiac muscles aids the heart
the cross bridges help to ensure that electrical stimulation spreads evenly over the walls of the chambers it also ensures that the contraction is a squeezing actionrather than one dimensional
How are some muscles in the heart fibres adapted
purkyne tissue are modified to carry electrical impulses
heart muscle is myogenic and can initiate its own contractions
Where can skeletal muscle be found
joints in the skeleton
intercostal muscles
Describe skeletal muscles
it is made up of a large bundle of long cells called muscle fibres and each fibre is multi nucleate and is surrounded by a membrane called the sarcolemma
the cell cytoplasm is known as the sarcoplasm and is specialised to contain many mitochondria and an extensive sarcoplasmic reticulum
Describe the arrangement of muscle fibres in skeletal muscle
They arranged into a number of myofibrils which are contractile elements
they are then divided into sarcomeres which contain protein filaments called actin and myosin
describe how the sarcolemma is specialised
folds inwards across the muscle fibres and stick into the sarcoplasm called T tubules and they help to spread electrical impulses throughout the sarcoplasm so they reach all parts of the muscle fibre
what is the function of sarcoplasmic reticulum
stores and releases calcium ions that are needed for muscle contraction
Describe the stimulation of contraction
action potentials arriving at the end of the axon cause calcium ion channels to open and calcium ions flood in causing vesicles of acetyl choline to fuse with the plasma membrane and diffuse across the gap and fuse with receptors in the sarcolemma
this opens sodium ion channels causing sodium ions to enter the muscle fibre causing a depolarisation and a wave of depolarisation spreads along the sarcolemma and down transverse tubules into the muscle fibre
How do you investigate muscle stimulation
an electromyograph (EMG) electrodes detect action potentials in the motor neurone
What is creatine phosphate
a compound in muscle that acts as a store of phosphates and can supply phosphates to make ATP rapidly
describe the structure of myofibril
contain bundles of thick and thin myofilaments
thin filaments (I band) which are aligned to make up the light band these are held together by the Z line (light band)
thick filaments make up the dark band (A band)
thick and thin filaments overlap but where there is no overlap is called the H zone
Sarcomere - distance between two Z lines
thick and thin filaments are surrounded by sarcoplasmic reticulum
What is the distance between 2 Z lines called
sarcomere
What is the H zone comprised of
mostly myosin as this is where no overlap occurs
Describe the thin filaments in myofibrils
they are actin and consists of 2 chains of actin subunits twisted around each other
wound around the actin is a molecule of tropomyosin which are globular molecules of troponin
Each troponin complex consists of three polypeptides one binds to actin one to tropomyosin and the third to calcium when its available
Actin filaments have binding sites for myosin heads called actin-myosin binding sites
describe thick filaments
consists of a bundle of myosin molecules and each molecule has two protruding heads at the end of each molecules
these heads are mobile and bind to the actin when the binding sites are exposed
Each myosin head has a binding site for actin and ATP
What lead to the sliding filament hypothesis
during contraction the light band and H zone get shorter therefore the Z lines move l=closer together so the thick and thin filaments slide past each other leading to this theory
What is the action of troponin and tropomyosin
These proteins help myofilaments move past each other
How can the thick and thin filaments bind
Actin filaments have binding sites for myosin heads called actin-myosin binding sites
Each myosin head has a binding site for actin and ATP
What is the mechanism of muscle contraction
the sliding action is caused by movement of myosin heads, when the muscle is stimulated the tropomyosin is moved aside exposing the binding sites on the actin, the myosin heads attach to the actin and move causing the actin to slide past the myosin
Describe the control of contraction
the received action potential is carried to the sarcoplasmic reticulum which stores calcium ions and causes the release of calcium ions into the sarcoplasm
the calcium ions bind to the troponin which alters the shape pulling the tropomyosin aside exposing the binding site on the actin
myosin heads bind to the actin forming cross bridges between filaments
the myosin heads move pulling the actin filament past the myosin filament
The myosin heads detach from the actin and can bind again further up the filament
What happens once contraction occurs
the calcium ions are rapidly pumped back into the sarcoplasmic reticulum allowing the muscles to relax
What is the role of ATP in muscle contraction
it supplies energy for contraction, part of the myosin head acts as ATPase and can hydrolyse ATP releasing energy
Describe the role of ATP in muscle contraction
the myosin head attaches to the actin filament forming a cross bridge
the myosin head tilts backwards causing the thin filament to slide past the myosin filament this is the power stroke and during the power stroke ADP and Pi are released from the myosin head
After the power stroke a new ATP molecule attaches to the myosin head breaking the cross bridge
The myosin head then returns to its original position and the atp is hydrolysed releasing the energy required to make this reaction occur and the myosin head can now make a new cross-bridge further along the actin filament
How is the supply of ATP maintained
Aerobic respiration
anaerobic respiration
creatine phosphate
What enzyme is involved when using creatine
creatine phosphotransferase
How much longer does creatine phosphate prolong a contraction
ATP available in muscle tissue is only enough to support 1-2 seconds worth of contraction and the supply of creatine phosphate is sufficient enough to prolong it for a further 2-4 seconds
Why is the circulation caused by the heart pumping important
transport of oxygen and nutrients
removal of waste products
transport of urea from liver to kidneys
distribute heat around the body
why does the requirement of cells and tissues vary
varies according to level of activity
how can heart action be modified
raising or lowering the heart rate
altering the force of contractions of the ventricular walls
altering stroke volume (volume of blood pumped by minute)
describe the difference between atrial and ventricular muscle
the atrial muscle has a higher myogenic rate than ventricular muscle
Why is a coordination mechanism in the heart essential
the two chambers must contract in a coordinated fashion or the action of the heart will be ineffective
What is called the hearts pacemaker
SAN sinoatrial node
describe the action of the SAN
it initiates a wave of excitation that usually overrides the myogenic action of the cardiac muscle
the SAN is a region of tissue that can initiate an action potential which travels as a wave of excitation over the atrial walls through the AVN and down purkyne fibres to the walls of the ventricles to contract
what hormone does the heart respond to and why
adrenaline which increases heart rate
How is the heart controlled at rest
by the SAN which has a set frequency varying from person to person typically 60-80 per minute
what can the frequency of excitation waves in the heart be altered by
by the output from the cardiovascular centre in the medulla oblongata
How is the frequency of the excitation waves altered
nerves from the cardiovascular centre in the medulla oblongata of the brain supply the SAN and affect the frequency of contractions
nerves are controlled by autonomic nervous system
what part of the nervous system are the nerves which alter frequency of excitation in the heart from
autonomic
how does the action of the accelerans and vagus nerve differ
accelerans causes the heaert rate to increase whereas action potentials travelling down the vagus nerve reduce heart rate
Describe what occurs when action potentials are sent down the accelerans nerve
Action potentials sent down the sympathetic accelerans nerve cause the release of the neurotransmitter noradrenaline at the SAN which increases heart rate
Describe what occurs when action potentials are carried down the vagus nerve
they release the neurotransmitter acetylcholine which reduces heart rate
what environmental factors can affect heart rate
inputs from the sensory receptors
How do environmental factors affect heart rate
the interactions of inputs is coordinated by the cardiovascular centre to ensure that the output to the SAN is appropriate to the overall conditions
give some examples of sensory inputs to the cardiovascular centre
stretch receptors in muscles
chemoreceptors in the carotid arteries, aorta and brain
stretch receptors in the walls of the carotid sinus
Describe how stretch receptors in the muscle are able to effect heart rate
they detect movement of the limbs sending impulses to the cardiovascular centre informing it that extra oxygen may soon be needed leading to an increase in heart rate
Describe how chemoreceptors in the carotid arteries have an effect on heart rate
the chemoreceptors in the carotid arteries, aorta and brain monitor the pH of the blood when excess CO2 reacts with water in blood plasma it produces a weak carbonic acid reducing the pH of the blood affecting the transportation of oxygen
the change in pH is detected by the chemoreceptors which send action potentials to the cardiovascular centre this will tend to increase the heart rate
Describe what may occur if CO2 concentration in the blood falls
reduces the activity of the accelerator pathway therefore the heart rate declines
Describe how stretch receptors in the carotid sinus affect heart rate
it a small swelling in the carotid artery which monitors blood pressure
If pressure rises too high the stretch receptors send action potentials to the cardiovascular centre leading to a reduction in the heart rate
what must happen if the controlling mechanism of the heart rate fails
an artificial pacemaker must be fitted which delivers an electrical impulses to the heart muscle
an artificial pacemaker may be connected to the SAN directly or directly to the ventricle muscle
Give an example of positive feedback caused by increasing heart rate
increasing heart rate may produce more carbon dioxide in the heart muscle which leads to a decrease in pH which will be detected by the chemoreceptors and tend to increase heart rate
Describe how sensory input is used to prevent the heart rate rising too high during intense exercise
stretch receptors in the carotid sinus will detect an increase in blood pressure and if the pressure rises too high it will send action potentials to the cardiovascular centre in the medulla oblongata leading to a reduction in heart rate
.How does auxin stretch cells
promoting active transport of H+ by an ATPase on the plasma membrane into the cell wall, the resulting low pH provides optimum conditions for wall loosening enzymes called expansins to work, these enzymes breaks bonds within the cellulose so the walls become less rigid and can expand as the cell takes in water
the H+ also interrupts the hydrogen bonds
how are plant hormones involved in the leaf loss of deciduous plants
auxins inhibit leaf loss and are produced in young leaves not older ones
ethene stimulates leaf loss and is produced in ageing leaves and abscission layer develops at the bottom of the leaf stalk separating the leaf from the rest of the plant
how are hormones involved in stomatal closure
abscisic acid binds to receptors on guard cell membranes causing calcium ions to enter through the now open channels to the cytosol
the increased concentration of calcium ions in the cytosol causes other ion channels to open and ions such as potassium leave the guard cell raising its water potential. Water then leaves the guard cell making it falcid and the stomata close
