Plant and Animal responses Flashcards
(128 cards)
1
Q
CHEMICAL DEFENCES: Tannins
A
-phenolic compounds located in cell vacuoles or in surface wax of plants
-toxic to microorganisms and larger herbivores
-in upper epidermis of leaves and make leaf taste bad
-in roots they prevent infiltration by pathogenic microorganisms
2
Q
CHEMICAL DEFENCES: alkaloids
A
-organic nitrogen containing bases that have important physiological effects on animals
-include nicotine, quinine, strychnine and morphine
-derived from amino acids
-feeding deterrents to animals as taste bitter
-located in growing tips and flowers
-in peripheral cell layers of stems and roots
3
Q
CHEMICAL DEFENCES: pheromones
A
-any chemical substance released by one living thing which affects the behaviour or physiology of another living thing
4
Q
Define tropism
A
directional growth response to in which direction of response is determined by direction of external stimulus
5
Q
TYPES RESPONSE: phototropism
A
-shoots grow toward light which enable them to photosynthesise
6
Q
TYPES RESPONSE: geotropism
A
-roots grow towards pull of gravity
-this anchors them in soil and helps them to take up water which is needed for support (keeps cells turgid) as raw material for photosynthesis and helps cool plant
-also be minerals such as nitrates in water, needed for synthesis of amino acids
7
Q
TYPES RESPONSE: chemotropism
A
-on a flower, pollen tubes grow down style attracted by chemicals, towards ovary where fertilisation can take place
8
Q
TYPES RESPONSE: thigmotropism
A
-shoots of climbing plants such as ivy wind around other plans or solid structures to gain support
9
Q
Positive v negative response
A
-if plant responds towards stimulus it is positive tropic response
-if plant responds away from stimulus it is still a tropic response but negative
10
Q
Nastic responses
A
-non directional response to external stimuli
-e.g. sensitive plant, Mimosa pudica responds to touch with sudden folding of leaves
11
Q
What are plant hormones
A
-they coordinate plant response to environmental stimuli
-they are chemical messengers that can be transported away from their site of manufacture to act in other parts of plant
-they are not produced by endocrine glands but by cells in a variety of tissues in the plant
12
Q
Mechanism of plant hormones
A
-when hormones reach target cells, bind to receptors on plasma membrane
-specific hormones have specific shapes which can only bind to specific receptors with complementary shapes on membranes of particular cells
-this specific binding ensures hormones only act upon correct tissues
-some hormones can amplify each others effects and some even cancel each other out
-hormones can influence cell division, elongation or differentiation
13
Q
HORMONES: cytokinins
A
-promote cell division
-delay leaf senescence
-overcome apical dominance
-promote cell expansion
14
Q
HORMONES: abscisic acid
A
-inhibits seed germination and growth
-causes stomatal closure when plant stressed by low water availability
15
Q
HORMONES: auxins
A
-promote cell elongation
-inhibit growth of side shoots
-inhibit leaf abscission (leaf fall)
16
Q
HORMONES: gibberellins
A
-promote seed germination
-promote growth of stems
17
Q
HORMONES: ethene
A
-promote fruit ripening
18
Q
How do hormones move around plant
A
-either by active transport, diffusion or mass flow in phloem sap or xylem vessels
19
Q
Define apical dominance
A
-inhibition of lateral buds further down shoot by chemicals produced by apical bud at tip of plant shoot
20
Q
Describe role of auxins and how they were tested
A
-plant hormones responsible for regulating plant growth
-if you break tip off plant, plant starts to grow side branches from lateral buds that were previously dormant
-auxin levels drop when tip removed and buds grow
-to test this, scientists applied paste containing auxins to cut end of shoot and lateral buds did not grow
-however, when they applied a ring of auxin transport inhibitor below apex of shoot, lateral buds grew
-suggests that normal auxin level in lateral buds inhibits growth, whereas low auxin levels promote growth
-the two variables - auxin levels and growth inhibition - may have no effect on each other both could be affected by third variable
21
Q
Describe abscisic acid
A
-inhibits bud growth
-high auxin shoot may keep abscisic acid levels high in bud
-when tip removed, source of auxin, abscisic acid levels drop and bud starts to grow
22
Q
Describe cytokinins
A
-promote bud growth
-directly applying cytokinins to buds can override apical dominance effect
-high levels of auxin make apex a sink for cytokinins produced in root - most cytokinins goes to shoot apex
-when apex removed, cytokinins spread evenly around plant
23
Q
Describe how gibberellins cause stem elongation
A
-cause growth in internodes by stimulating cell elongation (by loosening cell walls) and cell division (by stimulating production of protein that controls cell cycle)
24
Q
Describe how gibberellins control seed germination
A
-when seeds absorbs water, embryo releases gibberellins which travel to aluerone layer in endosperm region of speed
-gibberellin enables production of amylase which can break down starch into glucose
-this provides substrate for respiration for embryo and so it grows
-glucose also used for protein synthesis
25
Where does plant growth occur
-plant cells can only divide and expand in groups of immature cells that are still capable of dividing
(meristems)
-apical meristems - at tips or apices of roots and shoots; responsible for roots and shoots getting longer
-lateral bud meristems - found in buds; give rise to side shoots
-lateral meristems - forming cylinder near outside of roots and shoots and are responsible for roots and shoots getting wider
-intercalary meristems - located between nodes where leaves and buds branch off stem. Growth between nodes responsible for some shoots getting longer
26
How can we investigate phototropic responses
-using experimental plant and control plant with 10 replicates
-control plant is illuminated from all sides, while experimental has illumination from just one side
-in each plant, shoots and roots are marked every 2mm at start
-after several days look at results
-shoot has bent toward light because shady side of shoot has elongated more than illuminated side
-mean and standard deviation of lengths between marks has increased on shady side
27
How can we investigate geotropic responses
-a control plant constantly spun (very slowly) by machine called klinostat to ensure effect of gravity applied equally to all sides
-for experimental plant klinostat is not switche don so gravity only applied to on side
-in experimental plant, root bends downwards because upper side of root elongated more than lower side
-shoot bends upwards because lower side of shoot elongated more than upper side
-in control, both root and shoot grow horizontally
28
How are the effect of plant hormones on phototropism investigated
-Darwin's experiments confirmed that shoot tip was responsible for phototropic responses
-Boysen-Jensen work confirmed water and/or solutes need to be able to move backwards from shoot tip for phototropism to work
-when permeable gelatine block inserted behind shoot tip, shoot still showed positive phototropism
-when impermeable mica block inserted, no phototropic response
29
How was the role of auxin as the chemical messenger confirmed
-using a series of different concentrations of auxins (e.g. IAA) created by serial dilution gives shoot curvature in proportion to amount of auxin
-auxins are produced at apex of shoot
-auxin travels to cells in zone of elongation, causing them to elongate and make shoot grow
-when light equal on all sides, auxin simply promotes shoot growth evenly
-light shining on one side of shoot appears to cause auxins to move to shaded side causing cells there to elongate more quickly, and shoot bends toward light
-extent to which cells elongated is proportional to concentration of auxins
30
Describe the mechanism of auxins
-auxin increases stretchiness of cell wall by promoting active transport of H+ by ATPase enzyme on plasma membrane, into cell wall
-the resulting low pH provides optimum conditions for wall loosening enzymes (expansins) to work
-these enzymes break bonds within cellulose (at same time, increased hydrogen ions disrupt hydrogen bonds within cellulose) so walls become less rigid and can expand as cell takes in water
31
Explain the research on how light causes the redistribution of auxins
-two enzymes identified - phototropin 1 and phototropin 2 - whose activity is promoted by blue light
-blue light is main component of white light that causes the phototropic response
-hence, lots of phototropin 1 activity on light side but progressively less toward dark
-this gradient thought to cause redistribution of auxins through their effect on PIN proteins
these transmembrane proteins can be found dorsally, ventrally or laterally on plasma membrane of cells and they control efflux of auxin from each cell, essentially sending auxin in different directions in shoot, depending on their location
32
How is activity of PIN proteins controlled
-controlled by PINOID molecule
-one theory suggests that phototropins affect activity of PINOID which then affects PIN activity
-however evidence from ARABIDOPSIS suggests this may only work for pulse induced phototropism (short bursts of light) with another independent mechanism able to operate in continuous light
33
Explain the effect of auxin in geotropic responses of roots
-in a root lying flat, Went discovered that auxin accumulates on lower side where is inhibits cell elongation
-the upper side continues to grow and root bends downwards
-this effect of auxin in roots is in contrast to that in the shoot where auxin promotes cell elongation on lower side, making shoot lying flat bend upwards
-this happens because root and shoot cells in elongation zone exhibit different responses to same concentration of auxin
-concentrations that stimulate growth in shoot=inhibit root growth
34
COMMERCIAL USES: auxins
-can be used to prevent leaf and fruit drop and to promote flowering for commercial flower production
-useful if there are too many small fruit that will be difficult to sell - fruit produces fewer, larger fruit
- cuttings - dipping end of cutting in rooting powder (containing auxins) before planting it encourages root growth
-seedless fruit - treating unpollinated flowers with auxin can promote growth of seedless fruit. Applying auxin promotes ovule growth which triggers automatic production of auxin by tissues in developing fruit, helping to complete developmental process
-herbicides - used as herbicides, man made auxins hard to break down and can act within plant for longer. Promote shoot growth too much that stem cannot support itself, buckles and dies
35
COMMERCIAL USES: cytokinins
-because cytokinins can delay leaf senescence they are sometimes used to prevent yellowing of lettuce leaves after been picked
-used in tissue culture to help mass produce plants
-promote bud and shoot growth from small pieces of tissue taken from plant parent - produces short shoot with lot of side branches which can be split into lots of small pieces
-each of these then grown separately
36
COMMERCIAL USES: gibberellins; fruit production
-gibberellins delay senescence in citrus fruit, extending time fruit can be left unpicked and making them available for longer in the shops
-gibberellins acting with cytokinins can make apples elongated to improve their shape
-without gibberellins bunches of grapes are very compact which restricts growth of individual grapes
-with gibberellins grape stalk elongates, less compacted and grape gets bigger
37
COMMERCIAL USES: gibberellins; brewing
-to make beer you need malt which is usually produced in malthouse at brewery
-when barley seeds germinate, the aluerone layer of seed produces amylase enzymes that break down stored starch into maltose
-usually genes for amylase production are switched on by naturally occurring gibberellins
-adding gibberellins can speed up process
-malt produced by drying and grinding seeds
38
COMMERCIAL USES: gibberellins; sugar production
-spraying sugar cane with gibberellins stimulates growth between nodes, making stems elongate
-useful as sugar cane stores sugar in cells of internodes, making more sugar available from each plant
39
COMMERCIAL USES: gibberellins; plant breeding
-plant breeders job to produce plants with desired characteristics by breeding together other plants usually over many generations
-however in conifer plants this can take particularly long time because conifers spend long as juveniles before becoming reproductively active
-gibberellins can speed up process by inducing seed formation on young trees
-seed companies that want to harvest seeds from biennial plants can add gibberellins to induce seed production
-stopping plants making gibberellins also useful
-spraying with gibberellin synthesis inhibitors can keep flowering short and stocky - desirable in poinsettias
-also ensures internodes of crop plant stay short, helping prevent lodging
-lodging occurs in wet summers - stem bend over because of weight of water collected on ripened seed heads making crop difficult to harvest
40
How is ethene applied
-ethene is a gas so cannot be sprayed directly, scientists developed 2-chlorethylphosophonic acid which can be sprayed in solution, so is easily absorbed and slowly releases ethene inside plant
41
COMMERCIAL USES: ethene
-speed up fruit ripening in apples, tomatoes, citrus fruit
-promoting fruit drop in cotton, cherry, walnut
-promoting female sex expression in cucumbers, reducing chance of self pollination (bitter taste) and increase yield
-promoting lateral growth in some plants, yielding compact flowering stems
42
Why is restricting ethene effects useful
-storing fruit at low temperature with little oxygen and high carbon dioxide levels prevents ethene synthesis and thus prevents fruit ripening
-means fruits can be stored for longer - essential when shipping unripe bananas from caribbean
-other inhibitors of ethene synthesis such as silver salts, can increase shelf life of cut flowers
43
Summarise the role of the nervous system
-successful organism must be able to respond to changes in the environment
-these changes could be in internal or external environment
-communication system must enable: cell signalling between all part of body, coordination of range of effectors to carry out responses to sensory input, suitable responses, detection of changes in environment
-many environmental changes require rapid and well coordinated responses to ensure survival
-this may involve wide array of responses such as coordinated muscle action, control of balance, temperature regulation etc
44
Describe the divisions of the nervous system
-most obvious division of nervous system is into central nervous system and peripheral nervous system
-the PNS further divided into sensory system and motor system
-motor system divided into somatic nervous system and autonomic nervous system
-these divisions help us describe nervous actions and to understand coordination processes
-CNS - brain and spinal cord
-PNS- sensory nervous system and motor system
-MOTOR SYSTEM - somatic nervous system and autonomic nervous system
45
Describe the brain of the CNS
-human brain contains about 86 billion neurones
-much of brain is composed of relay neurones which have multiple connections enabling complex neural pathways
-most of these cells are non myelinated cells and tissue looks grey in colour - known as grey matter
46
Describe the spinal cord of the CNS
-also has many non myelinated relay neurones making up central grey matter
-however spinal cord also contains large numbers of myelinated neurones making up an outer region of white matter
-these myelinated neurones carry action potentials up and down the spinal cord for rapid communication over longer distances
-spinal cord is protected by vertebral column
-between each of these vertebrae, peripheral nerves enter and leave spinal cord carrying action potentials to and from rest of body
47
Describe the peripheral nervous system
-role of the peripheral nervous system is to ensure rapid communication between the sensory receptors, CNS and effectors
-the PNS is composed of sensory and motor neurones
-these usually bundled together in connective tissue sheath to form
48
Describe the sensory nervous system
-sensory fibres entering CNS are dendrons of sensory neurones
-these neurones conduct action potentials from the sensory receptors into CNS
-these neurones have their cell body in dorsal root leading into spinal cord and short axon connecting to other neurones in CNS
49
What is the motor nervous system
-conducts action potentials from the CNS to effectors
-further subdivided according to functions of motor neurones
50
Describe the somatic nervous system
-consists of motor neurones that conduct action potentials from CNS to the effectors that are under voluntarily (conscious) control, such as skeletal muscles
-these neurones are mostly myelinated so that responses can be rapid
-there is always one single motor neurone connecting CNS to effector
51
Describe the autonomic nervous system
-consists of motor neurones that conduct action potentials from CNS to effectors that are not under voluntary control
-this includes the glands, the cardiac muscles and smooth muscle in the walls of the blood vessels, the airways and wall of digestive system
-control of many of these effectors does not require rapid responses and the neurones are mostly non myelinated
-there are at least 2 neurones involved into connection between CNS and effector
-these neurones are connected at small swellings called ganglia
52
Define autonomic
-means self governing and autonomic nervous system operates to a large extent independently of conscious control
-it is responsible for controlling majority of homeostatic mechanisms and so plays vital role in regulating internal environment of body
53
How is the autonomic nervous system further divided
-sympathetic system - prepares body for activity
-parasympathetic system - conserves energy
-differ both in structure and action
-they are antagonistic systems as action of one system opposes action of the other
-in general, at rest, action potentials pass along the neurones of both systems at relatively low frequency
-controlled by subconscious parts of brain
-changes to internal conditions or stress lead to changes in the balance of stimulation between two systems leading to an appropriate response
54
Compare the sympathetic and parasympathetic system
SYMPATHETIC
-consists of many nerves leading out of CNS each leading to separate effector
-ganglia just outside CNS
-short pre ganglionic neurones
-long post ganglionic neurones (variable in length, dependent upon position of effector)
-uses noradrenaline as neurotransmitter
-increases activity - prepares body for activity
-most active at times of stress
-effects include: increase heart rate, dilate pupils, increase ventilation rate, reduce digestive activity, orgasm
PARASYMPATHETIC
-consists of few nerves leading out of CNS, which divide up and lead to different effectors
-ganglia in effector tissue
-long pre ganglionic neurones (variable in length, dependent upon position of effector)
-short post ganglionic neurones
-uses acetylcholine as neurotransmitter
-decreases activity- conserves energy
-most active during sleep or relaxation
-effects include: decreases heart rate, constricts pupils, reduces ventilation rate, increase digestive activity, sexual arousal
55
Describe the 4 main structures of the brain
-cerebrum - largest part of the brain and organises most of our higher thought processes such as conscious thought and memory
-cerebellum - coordinates movement and balance
-hypothalamus and pituitary complex - organises homeostatic responses and controls various physiological processes
-medulla oblongata - coordinates many of autonomic responses
56
Structure of cerebrum
-has two cerebral hemispheres which are coordinated via major traits of neurones called corpus callosum
-outermost layer of cerebrum consists of thin layer of nerve cell bodies called cerebral cortex
57
What does cerebrum control
-'higher brain functions'
-conscious thought
-conscious actions (including ability to override some reflexes)
-emotional responses
-intelligence, reasoning, judgement and decision making
-factual memory
58
How is the cerebral cortex subdivided
-sensory areas receive action potentials indirectly from sensory receptors. Sites of regions allocated to receive input from different receptors are related to sensitivity of area that inputs are received from
-association areas compare sensory inputs with previous experience, interpret what the input means and judge appropriate response
-motor areas send action potential to various effectors (muscle and gland). The size of the regions allocated to deal with different effectors are related to complexity of movements needed in parts of body. Motor areas on left side of brain control effectors on right side of body and vice versa
59
Describe the cerebellum
-cerebellum contains over half of all neurones in brain
-it is involved with balance and fine coordination of movement
-to do this it must receive information from many sensory receptors and process information accurately
-the sensory receptors that supply information to cerebellum include retina, balance organs in inner ear and spindle fibres in muscle, give information about muscle length and joints
-the conscious decision to contract voluntary muscles is initiated in cerebral cortex
-however cerebral cortex does not provide complex signals required to coordinate complex movements
60
What does cerebellum control
-maintaining body position and balance, such as riding bike
-judging position of objects and limbs while moving or playing sport
-tensioning muscles in order to use tools and play musical instruments effectively
-coordinating contraction and relaxation of antagonistic skeletal muscles when walking and running
61
How does coordination occur
-control of requires learning
-once learnt, such activities become second nature and involve much unconscious control
-this sort of coordination requires complex nervous pathway
-the nervous pathways are strengthened by practise
-the complex activity becomes programmed into cerebellum and neurones from cerebellum conducts action potential to motor areas so motor output too the effectors can be finely controlled
62
How are cerebrum and cerebellum connected
by pons
63
Describe the hypothalamus role and how pituitary interlinked
-hypothalamus controls homeostatic mechanism in body
-it contains its own sensory receptors and acts by negative feedback to maintain constant internal environment
-temperature regulation - hypothalamus detects changes in core body temperature. However also receives sensory input from temperature receptors in skin. It will initiate responses to temperature change that regulate body temperature within narrow range. These responses may be mediated by nervous system or by hormonal system (via pituitary gland)
-osmoregulation - hypothalamus contains osmoreceptors that monitor water potential in blood. When water potential changes, osmoregulatory centre initiates responses that bring about reversal of this change. Responses are mediated by hormonal via pituitary gland
64
Describe the lobes of the pituitary gland
-pituitary gland acts in conjuction with hypothalamus
-pituitary glands consists of two lobes
-posterior lobe - linked to hypothalamus by specialised neurosecretory cells. Hormones such as ADH which are manufactured in hypothalamus, pass down neurosecretory cells and are released into blood from pituitary gland
-anterior lobe produces its own hormones, which are released into blood in response to releasing factors produced by hypothalamus. These releasing factors are hormones needed to be transported only short distance to pituitary. Hormones from anterior pituitary control a number of physiological processes in body including response to stress, growth, reproduction and lactation
65
What is a reflex action
-responses to changes in the environment that do not involve any processing in the brain to coordinate the movement
-nervous pathway is as short as possible so reflex is rapid
-most reflex pathway = sensory neurone - relay neurone - motor neurone
-brain may be informed that reflex has happened but is not involved in coordinating response
-reflex actions always have survival value - may be used to get out of danger, avoid damage or maintain balance
66
Describe the blinking reflex
-causes temporary closure of eyelids to protect eyes from damage
-the nervous pathway for the blinking reflex passes through part of the brain - cranial reflex
-however, it is a direct pathway that doesn't involve any thought processes in higher parts of brain
-receptor and effector are in same place - reflex arc
67
What stimulates blinking reflex
-sudden change in environment
-foreign object touching eye (corneal reflex)
-sudden bright light (optical reflex)
-loud sounds
-sudden movements close to eye
68
What is the corneal reflex
-reflex mediated by sensory neurone from cornea which enters pons
-a synapse connects sensory neurone to relay neurone which passes the action potential to motor neurone
-motor neurone passes back out brain to facial muscles causing eyelid to blink
-very short and direct pathway so corneal reflex is very rapid - takes about 0.1secs
-causes both eyes to blink, even if only 1 cornea affected
-sensory neurone involved in corneal reflex also passes action potential to myelinated neurones in pons
-these carry action potential to sensory region in cerebral cortex to inform higher parts of brain stimulus has occurred
-this allows reflex to be overriden by conscious control
69
How to inhibitory signals work
-cerebral cortex can send inhibitory signals to motor centre in pons
-myelinated neurones carrying impulses to and from cerebral cortex transmit action potentials much more rapidly than non myelinated relay neurone in pons
-therefore inhibitory actions potentials can prevent information of action potential in motor neurone
70
Describe optical reflex
-protects light sensitive cells of retina from damage
-the stimulus detected by retina and reflex mediated by optical centre in cerebral cortez
-this optical reflex is little slower than corneal reflex
71
What is knee jerk reflex
-a spinal reflex - nervous pathway passes through spinal cord rather than through brain
-involved in coordinating movement and balance
-quadricep muscle contracts to straighten leg
-this muscle attached to lower leg via patella tendon and connects patella to lower leg bones at front of knee
-when muscles at front of thigh stretched, specialised stretch receptors called muscle spindles detect increase in length of muscle
-if this stretching unexpected, reflex action causes contraction of same muscle
72
How do we balance
-in situation when standing still, muscle at front of thigh will stretch if knee bending or body starting to lean backwards
-contraction of muscles straightens the knee or brings body back above legs
-such response must be very rapid, so that body can be balanced
73
Pathway of knee jerk reflex
-sensory neurone - motor neurone
-one less synapse involved so response is quicker
74
Why can inhibition not occur in knee jerk reflex
-higher parts of brain informed that reflex occurring
-however because no relay neurone, brain cannot inhibit reflex
-inhibition relies on rapid myelinated neurones carrying inhibitory action potentials to synapses before motor neurone stimulated
-in absence of relay neurone, motor neurone stimulated directly by sensory neurone and insufficient delay to enable inhibition
-this is why doctors detect reflexes by tapping tendon below knee cap - cause immediate response that cannot be inhibited
75
How are reflex contractions inhibited
-when walking or running, knee must be bent and will stimulate muscle spindles
-however, complex pattern of nervous impulses coming from cerebellum able to inhibit reflex contractions
-action potentials sent to hamstring muscles stimulating it to contract, whilst inhibitory action potentials sent to synapse in reflex arc to prevent reflex contraction of opposing muscle
76
Why do we have complex sensory mechanisms
-to monitor changes in both internal and external environment
-these provide input to brain which must assimilate the inputs and coordinate a response which ensures survival
-even relatively simple task such as standing requires input from range of receptors including eyes, balance organs and muscle stretch receptors
77
Hoe do more complex activities differ from normal
-receive input from wider range of receptors
-input may include information about blood glucose levels, information from stretch receptors or pain receptors in skin and joints
78
Long v short term response
-typically short term responses are homeostatic mechanisms such as temperature control
-long term responses include behaviours associated with reproduction
79
What kinds of output are there
-the brain coordinates response through output to effectors
-action potentials in somatic nervous system
-action potentials in sympathetic and parasympathetic parts of autonomic nervous system
-release of hormones via hypothalamus and pituitary gland
80
What is the fight or flight response
-detecting threat to survival stimulates the fight or flight response
-in mammals this leads to range of physiological changes that prepare animal for activity
-that activity may be running away or may be direct challenge to perceived threat
81
List some physiological responses and their survival value
-pupils dilate= allow more light in eyes, make retina more sensitive
-heart rate and blood pressure increase= increase rate of blood flow to deliver more oxygen and glucose to muscles and remove more carbons dioxide/other toxins
-arterioles to digestive system and skin constrict whilst those to muscles and liver dilate= divert blood away from skins and towards muscles
-blood glucose levels increase= supplies energy for muscular contractions
-metabolic rate increase=convert glucose to useable forms of energy e.g. ATP
-ventilation rate and depth increase= increase gas exchange so more oxygen enter blood and supplies aerobic respiration
-endorphins released= wounds inflicted do not prevent activity
82
How is fight or flight coordinated
-receptors that can detect an external threat includes eyes, ears and nose
-internal receptors may detect a threat such as pain or sudden increase or decrease in blood pressure
-cerebrum uses such sensory input to coordinate suitable response
1) input feeds into sensory centres in cerebrum
2) cerebrum passes signals to association centres
3) if threat recognised, cerebrum stimulates the hypothalamus
4) hypothalamus increases activity in sympathetic nervous system and stimulates release of hormones from anterior pituitary gland
83
What is the role of the sympathetic nervous system
-autonomic nervous system controls many physiological mechanisms
-increasing stimulating of sympathetic nervous system will increase activity of effectors
-however nervous communication is used for rapid response rather than prolonged response
-a flight or flight from danger may need a prolonged response - this is achieved by endocrine system
-the sympathetic nervous system stimulates the adrenal medulla
-adrenaline released from adrenal medulla has wide range of effects on cells
84
Describe the mechanism of adrenaline action
-adrenaline is a first messenger
-it is an amino acid derivative and therefore unable to enter target cell; it must cause effect inside cell, without entering cell itself
1) adrenaline binds to adrenaline receptor on plasma membrane. This receptor is associated with G protein on inner surface of plasma membrane, which is stimulated to activate enzyme adenyl cyclase
2) adenyl cyclase activates ATP to cyclic AMP cAMP which is a second messenger inside cell
3) cAMP causes an effect inside cell by activating enzyme action. Precise effect depends upon cell that adrenaline has bound to
85
Describe the release of hormones from anterior pituitary
-hypothalamus secretes releasing hormones, known as releasing factors, into blood
-these pass down portal vessel to pituitary gland and stimulate release of tropic hormones from anterior part of pituitary gland
-these stimulate activity in variety of endocrine glands
86
Effect of corticotropin-releasing hormone (CRH)
-CRH from hypothalamus causes release of adrenocorticotropic hormone (ACTH)
ACTH passes around blood system and stimulates glucocorticoids such as cortisol which regulate metabolism of carbohydrates
-as result, more glucose released from glycogen stores
-new glucose may also be produced from fat and protein stores
87
Effect of thyrotropin-releasing hormone (TRH)
-TRH causes release of thyroid stimulating hormone (TSH) which stimulates thyroid gland to release more thyroid hormone (thyroxine)
-thyroxine acts on nearly every cell of body, increasing metabolic rate and making cells more sensitive to adrenaline
88
What is the role of the circulatory system
-transport of oxygen and nutrients, such as glucose, fatty acids and amino acids to tissues
-removal of waste products such as carbon dioxide from tissues to prevent accumulation that may become toxic
-transport urea from liver to kidneys
-distribute heat around body or deliver it to skin to be radiated away
89
Effect of activity on heart
-requirement of cells and tissues vary according to their level of activity
-when you're physically active your muscle cells need more oxygen and glucose so that they can respire more, releasing energy for contraction
-your heart muscle cells also need more oxygen and fatty acids
-all muscles will also need to remove more carbon dioxide and heat
90
How can the circulatory system adapt
-raising or lowering heart rate- number of beats per minute
-altering force of contractions of ventricular walls
-altering stroke volume (volume blood pumper per beat)
91
Describe the myogenic muscle of heart
-cardiac muscle in heart is myogenic
-this means it can initiate its own beat at regular intervals
-however, atrial muscle has a higher myogenic rate than the ventricular muscle
-two pairs of chambers must contract in a coordinated fashion or heart action will be ineffective
-therefore coordination mechanism essential
92
How is heart rate coordinated
-heart contains its own pacemaker - sinoatrial node SAN
-SAN initiates waves of excitation that usually override myogenic action of cardiac muscle
-SAN is a region of tissue that can initiate an action potential, which travels as wave of excitation over atrial walls, through AVN (atria-ventricular node) and down Purkyne fibres to walls of ventricles, causing them to contract
-heart also responds directly to adrenaline - increases heart rate
93
How is heart rate controlled by cardiovascular centre
-at rest, heart rate is controlled by SAN
-this has set frequency varying from person to person at which initiates wave of excitation
-frequency of excitation is typically 60-80 per minute
-however, frequency of these excitation waves is altered by output from cardiovascular centre in medulla oblongata
-nerves from cardiovascular centre in medulla oblongata of brain, supply SAN
-these nerves part of autonomic nervous system
-these nerves do not initiate contraction but can affect frequency of contractions
94
How is frequency of contractions affected
-action potentials sent down sympathetic nerve (the accelerans nerve) causes release of neurotransmitter noradrenaline at SAN. This increases heart rate
-action potentials sent down vagus nerve release the neurotransmitter acetylcholine which reduces heart rate
95
How do environmental factors affect heart rate
-input from sensory receptors fed to cardiovascular centre in medulla oblongata
-some inputs increase heart rate, others decrease it
-the interaction of these inputs is coordinated by cardiovascular centre to ensure the output to SAN is appropriate to overall conditions
96
SENSORY INPUT: stretch receptors
-stretch receptors in muscles detect movement in limbs
-these send impulses to cardiovascular centre, informing it that extra oxygen may soon be needed
-this leads to an increase in heart rate
97
SENSORY INPUT: chemoreceptors
-chemoreceptors in carotid arteries, aorta and brain monitor pH of blood
-when we exercise, muscles produce more carbon dioxide
-some of this reacts with water in blood plasma to produce weak acid (carbonic acid)
-this reduces pH of blood, which will affect transport of oxygen
-the change in pH is detected by chemoreceptors which will send action potentials to cardiovascular centre
-this will tend to increase heart rate
98
SENSORY INPUT: concentration of CO2
-when we stop exercising, concentration of carbon dioxide in blood falls
-this reduces activity of accelerator pathway
-therefore heart rate declines
99
SENSORY INPUT: stretch receptors in carotid sinus
-the stretch receptors in carotid sinus monitor blood pressure
-carotid sinus is small swelling in carotid artery
-an increase in blood pressure, perhaps during vigorous exercise, is detected by these stretch receptors
-if pressure rises too high, stretch receptors send action potentials to cardiovascular centre, leading to reduction in heart rate
100
How is heart rate artificially controlled
-if mechanism controlling heart rate fails, artificial pacemaker must be fitted
-a pacemaker delivers electrical impulse to heart muscle
-pacemaker is implanted under skin and fat on chest (or sometimes within chest cavity itself)
-an artificial pacemaker may be connected to SAN or directly to ventricle muscle
101
Compare the somatic and autonomic nervous system
SOMATIC
-under conscious control
-all sensory neurones
-motor neurones to skeletal muscle
-sensory receptors-CNS via dorsal root ganglion
-one motor neurone pathway
AUTONOMIC
-under involuntary control
-no sensory neurones
-motor neurones to smooth, cardiac muscle and glands
- 2 motor neurones in pathway
102
Compare sympathetic and parasympathetic nervous system
SYMPATHETIC
-increase heart rate
-times of stress - fight or flight
-short pre-ganglionic neurone
-long/variable post ganglionic neurone
-autonomic ganglion just outside CNS
-neurotransmitter =noradrenaline
PARASYMPAHETIC
-decrease heart rate
-rest and digest
-long pre-ganglionic neurone
-short post ganglionic neurone
-autonomic neurone within effector tissue
-uses vagus and pelvic nerve
-neurotransmitter=acetylcholine
103
Describe the structure of muscles
-muscles are composed of cells arranged to form fibres
-these fibres can contract to become shorter, producing force
-contraction is achieved by interaction between two protein filaments (actin and myosin) in muscle cells
-muscle cannot elongate without antagonist
-therefore, muscles usually arranged in opposing pairs so that one contracts as other elongates
-in some cases, antagonist may be elastic recoil or hydrostatic pressure in chamber
104
Describe involuntary (smooth) muscle
-consists of individual cells, tapered at both ends (spindle shaped)
-at rest, each cell about 500um long and 5um wide
-each cells contains nucleus and bindles of actin and myosin
-this type muscle contracts slowly and regularly
-does not tire quickly
-controlled by autonomic nervous system
-found in walls of tubular structures such as digestive system and blood vessels
-muscle arranged in longitudinal and circular layers that oppose each other
105
Describe structure of cardiac muscle
-cardiac muscle forms muscular part of heart
-individual cells form long fibres, which branch to form cross-bridges between fibres
-cross-bridges help ensure that electrical stimulation spreads evenly over walls of chambers
-when muscle contracts, arrangement also ensures that contraction is squeezing action rather than one dimensional
-cardiac muscle appears striated (striped) under microscope
106
How are cardiac muscle cells joined
-cells joined by intercalated discs
-these are specialised cell surface membranes fused to produce gap junctions that allow free diffusion of ions between cells
-action potentials pass easily and quickly along and between cardiac muscle fibres
107
Describe the contraction of cardiac muscle
-cardiac muscle contracts and relaxes continuously throughout life
-can contract powerfully and does not fatigue easily
-some muscle fibres in heart (Purkyne fibres) are modified to carry electrical impulses
-these coordinate the contraction of chamber walls
-heart muscle is myogenic - can initiate own contraction
-however, rate of contraction normally controlled by SAN
108
Describe contraction of voluntary muscle
-skeletal muscle occurs at joints in skeleton
-contraction causes movement of skeleton by bending or straightening joints
-the muscles are arranged in pairs called antagonistic pairs
-when one contracts, other elongates
-contracts quickly and powerfully and fatigues quickly
109
Describe the structure of voluntary muscle
-muscle cells form fibres of about 100um diameter
-each fibre is multinucleate (many nuclei) and surrounded by membrane called sacrolemma
-muscle cell cytoplasm known as sarcoplasm and specialised to contain many mitochondria and extensive sarcoplasmic reticulum (specialised endoplasmic reticulum)
-contents of fibres arranged into number of myofibrils which are contractile elements
-myofibrils divided into chain of subunits called sacromeres
-sacromeres contain protein filaments actin and myosin
110
Describe the appearance of voluntary muscle under microscope
-actin and myosin arranged in particular banded pattern which gives muscle a striped appearance
-dark bands known as A bands and lighter bands are I bands
111
What is the neuromuscular junction
-skeletal muscle under voluntary control
-its contractions are stimulated by somatic nervous system
-junction between nervous system and muscle called the neuromuscular junction - many similarities to synapse
112
List the stimulation of contraction
1) action potentials arriving at end of axon open calcium ion channels in membrane. Calcium ions flood into end of axon
2) vesicles of acetylcholine move towards and fuse with end of membrane
3) acetylcholine molecules diffuse across gap and fuse with receptors in sarcolemma
4) this opens sodium ion channels which allow sodium ions to enter muscle fibre causing depolarisation of sarcolemma
5) wave of depolarisation spreads along sarcolemma and down transverse tubules into muscle fibre
113
Describe the motor unit
-some motor neurones stimulate single muscle fibres
-however, many motor neurones divide and connect to several muscle fibres
-all these muscle fibres contract together, providing stronger contraction
-this called motor unit
114
Describe the structure of myofibrils
-myofibrils are the contractile units of skeletal muscle and contain two types of protein filaments
-thin filaments which aligned to make up light band, held together by Z line
-thick filaments which make up dark band
-the thick and thin filaments overlap but in middle of dark band there is no overlap - called H zone
-distance between two Z lines called sacromere
-this is function unit of muscle
-at rest, sacromere about 2.5um long
-thick and thin filaments surrounded by sarcoplasmic reticulum
115
Structure of thin filaments
-thin filaments are actin
-each filaments consists of two chains of actin subunits twisted around each other
-wound around actin is a molecule of tropomyosin to which are attached globular molecules of troponin
-each troponin complex consists of three polypeptides; one binds to actin, one to tropomyosin and third binds to calcium when available
-tropomyosin and troponin are part of mechanism to control muscular contraction
-at rest these molecules cover binding sites to which thick filaments can bind
116
Structure of thick filaments
-each thick filament consists of bundle of myosin molecules
-each myosin molecule has two protuding head, which stick out at each end of molecule
-these heads are mobile and can bind to actin when binding sites exposed
117
Describe sliding filament hypothesis
-during contraction the light band and H zone gets shorter
-therefore, the Z lines move closer together and sacromere gets shorter
-this observation led to sliding filament hypothesis
-during contraction thick and thin filaments slide past one another
118
Describe the mechanism of contraction
-sliding action is caused by movement of myosin heads
-when muscle stimulated, the tropomyosin is moved aside, exposing binding sites on actin
-the myosin heads attach to actin and move, causing actin to slide past myosin
119
Describe the control of contraction
1) when muscle stimulated the action potential passes along the sarcolemma and down transverse tubules (t-tubules) into muscle fibre
2)action potential is carried to sarcoplasmic reticulum, which stores calcium ions, and causes release of calcium ions into the sarcoplasm
3) calcium ions bind to troponin which alters the shape pulling the tropomyosin aside. This exposes binding site on actin
4) myosin heads bind to actin, forming cross-bridges between filaments
5) myosin heads move, pulling the actin filament past myosin filament
6) myosin heads detach from actin and can bind again further up actin filament
-millions of cross bridges can be formed between actin and myosin filaments
-once contraction has occurred, the calcium ions are rapidly pumped back into sarcoplasmic reticulum, allowing muscle to relax
120
Role of ATP
-ATP supplies energy for contraction
-part of myosin head acts as ATPase and can hydrolyse ATP to ADP and inorganic phosphate (Pi) releasing energy
121
Mechanism of releasing energy
1) myosin head attaches to actin filament, forming a cross bridge
2) myosin head moves (tilts backwards) causing thin filaments to slide past myosin filament. This is the power stroke. During the power stroke, ADP and Pi are released from myosin head
3) after power stroke, new ATP molecules attaches to myosin head, breaking cross bridge
4) myosin head then returns to its original positions (swings forward again) as ATP hydrolysed, releasing the energy to make this movement occur. The myosin head can now make a new cross bridge further along the actin filament
122
Why must ATP supply be maintained
-as there are millions of myosin heads involved in muscle contraction, there is huge requirement for ATP
-the ATP available in muscle tissue is only enough to support at most 1-2 seconds worth contraction
-ATP must be regenerated very quickly in order to allow continued contraction
123
How is ATP supply maintained : AEROBIC RESPIRATION
-aerobic respiration in mitochondria. Muscle tissue contains a large number of mitochondria in which aerobic respiration can occur. The Bohr effect helps release more oxygen from haemoglobin in blood. However, during intense activity, rate at which ATP can be produced will be limited by delivery of oxygen to muscle tissue
124
How is ATP supply maintained: ANAEROBIC RESPIRATION
-anaerobic respiration in sarcoplasm of muscle tissue. Anaerobic respiration can release a little more ATP from respiratory substrates. However, it leads to production of lactate (lactic acid) which is toxic. Anaerobic respiration can only last a few seconds before lactic-acid build up starts to cause fatigue
125
How is ATP supply maintained : CREATINE PHOSPHATE
-creatine phosphate in sarcoplasm acts a reverse store of phosphate groups. Phosphate can be transferred from the creatine phosphate to ADP molecules, creating ATP molecules very rapidly. The enzyme creatine phosphotransferase is sufficient to support muscular contraction for a further 2-4 seconds
126
Give an involvement of the endocrine system within the fight or flight response
-adrenaline is released
-blood glucose levels rise
-endorphins are released
127
RP: effects of IAA (auxins) on shoot growth
-take 15 wheat seedlings, measure them and cut final 2mm from tip
-take further 5 seedlings and measure them but do not remove tip
-treat 5 seedlings with lanolin to cover end tip (A)
-treat 5 seedlings with lanolin infused with IAA (B)
-leave 5 seedlings untreated (C)
-return seedlings to beaker with roots surrounded by wet cotton wool
-after 3 days measure all them again
-seedlings in group A and C will not have grown
-group B with intact seedlings and IAA will have grown
128
RP: investigating muscle stimulation
-electrical activity of muscles can be investigated using an electromyograph (EMG)
-when muscle is stimulated the motor neurone creates action potentials in muscle fibres
-electrodes applied to surface of skin detect combined effects of these action potentials
-simple contraction of muscle seen as series of disorganised peaks on trace
-amplitude of EMG recording reflects number and size of motor units involved in contraction so more powerful contraction =higher amplitude
-recorded trace called electromyogram
