5.5 Flashcards
(253 cards)
1
Q
What does biotic mean
A
Living
2
Q
What does abiotic mean
A
Non livint
3
Q
What does plants responding to stimulus help them to do
A
Survive long enough to reproduce
4
Q
What is an example of plants responding to external stimuli
A
In high temps plants deposit thick layers of wax on leaves and in windy conditions more lignified vascular tissue
5
Q
What are 3 chemicals plants have to deter herbivores
A
Tannins, alkaloids, pheromones
6
Q
What are tannins
A
Toxic to microorganisms and larger herbivores, in leaves in upper epidermis and makes leaves taste bad, in roots they prevent infiltration by pathogenic microorganisms
7
Q
What are alkaloids
A
Derived from amino acids, in plants, feeding deterant to animals by tasting butter and found in growing tips and flowers and peripheral cell layers of stems and roots
8
Q
What are pheromones
A
Chemicals released by individual and can effect behaviour/physiology of another
9
Q
What is tropism
A
Directional growth responses of plant
10
Q
What is phototropism
A
Shoots grow towards light (positively phototropic) enables them to photosynthesis and stay turgid
11
Q
What is geotropism
A
Roots grow to pull of gravity, anchors them in soil to take up water to support plant as raw materials for photosynthesis and to cool plant, also nitrate in water for synthesis of amino acids
12
Q
What is chemotropism
A
On flower, pollen tubes grow does style, attracted by chemicals to ovary where fertilisation occurs
13
Q
What is thigmotropism
A
Shoots of climbing plants like ivy wind round other plants or solid structures for support
14
Q
What is a positive tropic response
A
Plant responds towards stimulus
15
Q
What is a negative tropic response
A
Plant responds away from stimulus
16
Q
What is a nastic response
A
Non-directional response to external stimuli
17
Q
WhT are plant hormones
A
Chemical messengers that can be transported away from site of manufacture to act in other parts (cells or tissue) of plant
18
Q
What produces plant hormones
A
cells in a variety of tissues
19
Q
What do plant hormones do when they reach target cells
A
Bind to receptors on plasma membrane, only bind with complementary receptors on certain cells, specific binding ensures hormones act on correct tissue, some hormones have different effects on different tissues, some amplify effects others cancel effects
20
Q
What do hormones influence
A
Cell division, cell elongation, cell differentiation
21
Q
What is the effect of plant hormone cytokinins
A
Promote cell division, delay leaf senescence, overcome apical dominance, promote cell expansion
22
Q
What is the effect of plant hormone abscisic acid
A
Inhibits seed germination, causes stomatal closure when plant stressed by low water availability
23
Q
What is the effect of plant hormone auxins
A
Promotes cell elongation, inhibits side shoot growth, inhibits leaf abscission (leaf fall)
24
Q
What is the effect of plant hormone gibberellins
A
Promotes seed germination and growth of stems
25
What is the effect of plant hormone ethene
Promotes fruit ripening
26
What 3 ways to hormones travel round plant
Active transport, diffusion, mass flow in phloem sap/xylem vessel
27
WhT are auxins
Plant hormones for regulating plant growth
28
What happens if you break shoot tip (apex) of plant
Plant starts to grow side branches from lateral buds that before we’re dormant, auxin from apical bud prevents lateral buds from growing when removed auxin level in shoot drops and buds grow
29
How did scientists test their hypothesis about auxin and regulating growth
Applied auxin paste to cut end of shoots and lateral buds didn’t grow
30
What is a limitation of scientists test about auxin and regulating growth
Their manipulation of plant could have unexpected effect, on exposure to oxygen, cells on cut end could have produced hormone that promoted lateral bud growth, so scientists applied ring of auxin transport inhibitor below apex of shoot and lateral buds grew
31
What did scientists conclude from their experiment with auxin and growth of lateral buds
Scientists said normal auxin levels in lateral buds inhibit growth but low levels of auxin promotes growth
32
What are the 2 variables in auxin and growth regulation
Auxin levels and growth inhibition may have no effect on each other but effect a 3rd variable, different scientists said auxin levels in lateral buds of beans increased when shoot cut off
33
What 2 other hormones do scientists now thing aid auxin in growth regulation
Abscisic acid and cytokinins
34
What is abscisic acid role in growth regulation
Inhibits bud growth, high auxin in shoot keeps abscisic acid levels high in bud when tip removed, abscisic acid levels drop and bud grows
35
What is cytokinins role in growth regulation
Promotes bud growth, directly applying cytokinins to bud can override apical dominance effect, high levels of auxin make shoot apex a sink of cytokinins produced in roots, when apex removed cytokinins spread evenly around plant
36
What is a example of giberillins in stem elongation and germination
Disease causes rice to grow very tall, component involved in giberellins and giberellic acid
37
How did scientists check giberellins effect on plants
When applied to dwarf plants giberellic acid made them grow taller suggests it is responsible for plant stem growth
38
What is limitation of experiment with giberellins
Needs to work with concentration of giberellins naturally found in plants and in parts of plant that they reach, to do this they compared giberellin in tall pea plants vs dwarf pea plants which otherwise are genetically identical, found plants with more giberellins were talker
39
How can you show giberellins directly effect stem elongation
Researchers must know how giberellins are formed, they worked out the Le gene responsible for converting giberellic acid to GA, researchers then chose pea plant with mutation what blocks giberellin production, these were only 1cm tall, when researchers grafted homozygous plant (can’t convert giberellic acid to GA1) and it grew taller
40
What do shoots with no giberellic acid have instead
Enzyme to convert giberellic acid to GA and can use unused giberellic acid from normal plants, as shoot grew tall it confirmed giberellins cause stem elongation by loosening cell wall and cell division by stimulating production of proteins that control cell cycle
41
How do giberellins promote seed germination
When seed absorbs water, embryo releases giberellins which travels to aleurone layer in endosperm region of seed
42
What does giberellin enable production of
Amalyse which breaks down starch to glucose, providing substrate for respiration for embryo so it grows, glucose also used for protein synthesis
43
What does plant cell wall limit
Cells ability to divide and expand
44
Where does growth occur in plants
Only in places with immature cells that can still divide (meristems)
45
What are the 3 meristems in plants and 4th found in some plants
Apical meristems, lateral bud meristems, lateral meristems and 4th intercalary meristems
46
What is apical meristem
At tips of roots and shoots and responsible for roots and shoots getting longer
47
What is lateral bud meristems
Found in buds and give rise to size shoots
48
AhT is lateral meristems
Form cylinder near outside of roots and shoots and responsible for widening roots and shoots
49
What is intercalary meristems
Located between nodes when leaves and buds branch off stem, growth between nodes responsible for shoots getting longer
50
When investigating phototropic responses what is the difference between control plant and experimental plant
Control plant illuminated from all side, experimental plant only illuminated from one side
51
What are the results of phototropic response experiment
After several days shoot bends to light as shady side has elongated more than illuminated side
52
When investigating geotropic responses what is control and what is experimental plant
Control plant spun very slowly by machine so gravity effect applied evenly to all sides, experimental plant plant isn’t spun so gravity only applied to one side
53
What we’re results from geotropic response experiment
Experimental plant, root bends down as upper side of root has elongated more than lower side, control, roots and shoots grow horizontally
54
What has series of experiments shown is responsible for phototropic responses
Chemical messenger
55
What did Darwin work confirm in phototropic responses
Shoot tip responsible for phototropic responses
56
What did Boysen-Jensens work confirm
Water and/or solutes need to move backwards from shoot tip for phototropism to occur
57
How did Boysen-Jensons experiments show water/solutes need to move back from shoot tip for phototropism to occur
When permeable gelatine block inserted behind shoot tip, shoot still showed positive phototropism, when impermeable mica block inserted, no phototropic response
58
How did Darwin experiments show phototropism
Control bend to light, if tip removed it stayed straight, stayed straight if tip had opaque cap, bend to light of tip had transparent cap, bend to light of base had opaque shield
59
How was phototropic effect artificially stimulated to show chemical messenger existed
Shoot tip placed on agar block, chemical later identified as auxin, diffuses from shoot tip to agar
60
What was done to confirm role of auxin as chemical messenger
Agar blocks impregnated with different concentrations of auxin and gives same results, using series of blocks with different auxin concentrations created by cereal dilution gives shoot curvature in proportion to amount of auxin
61
Where is auxin produced and where does it travel to
Produced at apex of shoot and travels to cell in zone of elongation making shoot grow
62
What happens to shoot with auxin when light even on all sides vs when light shines on one side
Auxin promotes even shoot growth but when light on one side it causes auxin to be transported to shaded side causing cells to elongated quicker so shoot bends to light
63
What is the extent to which a cell elongated proportional to
Concentration of auxin
64
What does auxin do
Increase stretchiness of cell wall by promoting active transport of hydrogen ions by ATPase on plasma membrane into cell wall, resulting low pH gives optimum conditions for wall loosening enzyme expansins to work
65
How do expansins work and increased hydrogen ions
Break bonds in cellulose and increased hydrogen ions disrupt hydrogen bonds so wall less rigid so can expand as cell takes in water
66
What 2 enzymes have been identified in redistribution of auxin due to light
Phototropin 1 and 2, their activity promoted by blue light
67
How does phototropin cause redistribution of auxin due to activity being promoted by blue light
Blue light main component of white light that causes phototropic response, so lots of phototropin 1 on light side but less on shaded side, gradient causes redistribution of auxin through their effect on PIN proteins
68
What are PIN proteins and where are they found
Transmembrane proteins found dorsally, ventrally or laterally on plasma membrane of cells and control efflux of auxin from each cell sending auxin in different directions in shoot depending on location on plasma membrane
69
What is activity of PIN proteins controlled by
Pinoids
70
What does one theory say about phototropins and pinoids
Phototropins affect pinoid activity which effects pin activity
71
What does recent evidence suggest about phototropins and pinoids
Phototropins may only effect pinoid activity and pin activity in pulse induced phototropism (short bursts of light) with another independent mechanism able to operate on continuous light
72
How is auxin involved in geotropic responses and how was it discovered
Auxin accumulates on lower side of roots lying flat where it inhibits cell elongation, upper side continues to grow and roots bend downwards, auxin promotes cell elongation on lower side making root lying flat bend upwards
73
Why does auxin cause different geotropic responses root and shoot
Root and shoot cells in elongation zone exhibit different responses to same concentration of auxin
74
What does the concentration of auxin that stimulates shoot growth so to root growth
Inhibits it
75
What are artificial auxins used for
To stop leave and fruit drop and promote flowering in commercial flower production, but high concentration of auxin can promote fruit drop
76
When is it useful for auxin to promote fruit drop
If too many small fruit that are be difficult to sell, auxin causes plant to grow fewer larger fruits
77
What is a commercial use for auxin in taking cuttings
Dipping end of cuttings in rooting powder before planting encourages root growth , rooting powder has auxin and so does talcum powder
78
What is a commercial use for auxin in seedless fruit
Treating unpollinated flower with auxin can promote seedless fruit growth, applying auxin promotes ovule growth causing production of auxins by tissues in developing fruit helping to complete development
79
What is a commercial use for auxin in herbicides
Auxins used as herbicides to kill weeds as they’re man made, plants find them more difficult to breakdown and can act within plant for longer promoting shoot growth so stem can’t support itself, buckles and dies
80
What do cytokinins do in commercial uses
Delay leaf senescence and used to stop yellowing of lettuce leaves after picking, used in tissue culture to mass produce plants
81
How is cytokinins used in mass production of plants
They promote bud and shoot growth form small pieces of tissue from parent plant, producing short shoot with many side branches that can be split to lots of small plants each grown separately
82
How are gibberellins used in artificial fruit production
Delay senescence in citrus fruits extending time fruit can be left unpicked and last shipping, if acting with cytokinins they can elongate apples to improve their shape, grape stalks elongate so less compact and grapes grow bigger
83
How are gibberellins used in brewing
When barley seed germinates aleurone layer of seed produces amylase that breaks starch to maltose and adding gibberellins speeds up process and then malt can be produced by drying and grinding seeds
84
How are gibberellins used in sugar production
Spraying sugar cane with gibberellins stimulates growth between nodes so stem elongates which is useful as cane sugar stores sugar in cells of internodes making more sugar available from each plant
85
How are gibberellins used in plant breeding
Nbl
86
What is the aim of plant breeding
To produce plant with desired characteristics by breeding plants over many generations
87
How are gibberellins used in plant breeding (increase production)
Speed up process by enduring seed formation in young trees
88
What are commercial uses for stopping gibberellins
Keeps flowers short and stocky and ensures internodes of crop plants stay short preventing lodging (occurs when wet stems bend over as weight of water collects on ripening seed head making crop hard to harvest
89
What is ethene and what does it mean if it’s commercial use
It’s a gas so can’t be directly sprayed but scientists developed a form of it which can be sprayed, is easily absorbed and slowly releases ethene inside plant
90
What are commercial uses of ethene
Speeding up Fruit ripening, promote fruit drop in cotton, cherry and walnut, promote female sex expressions in cucumbers, reducing self pollination and increasing yield, promotes lateral growth in some plants, yielding compact flowering stems
91
What is restricting ethene effect useful for
Storing fruit at low temp with little oxygen and high CO2 stops ethene synthesis and fruit ripening so fruit stored for longer (banana shipped from Caribbean) and also it can increase shelf life of cut flowers
92
Why do organisms require communication system
To response to external and internal environment to survive and need communication system to respond
93
What do all communication systems need to enable
Detection of change in environment, cell signalling between body parts, coordination of range of effectors to carry out responses to sensory input, enable suitable response
94
What may a rapid and well coordinated response involve
Coordinated muscle action, control of balance and posture, temp regulation and coordination with endocrine system (role of nervous system)
95
What are the 2 main categories the nervous system is divided into
Peripheral nervous system and central nervous system
96
What is the peripheral nervous system divided into
Sensory system and motor system
97
What is central nervous system divided into
Brain and spinal cord
98
What is the motor system subdivided into
Somatic nervous system and autonomic nervous system
99
What do most of the brains pathways rely on
Neurones which have multiple connections enabling complex neural pathways
100
What are most cells in the central nervous system (brain) and what are they called
Non-myelinated cells and tissue looks grey in colour (grey matter)
101
What is grey matter part of in spinal cord
Non-myelinated relay neurones
102
As well as grey matter what does spinal cord also contain large amount of
Myelinated neurones making outer region of white matter
103
What is myelinated neurones role in spinal cord
Carry action potentials up and down spinal cord for rapid communication of longer distances
104
What protects spinal cord and what is between each section of it
Protected by vertebral column, between each vertebrae peripheral nerves enter and leave spinal cord carrying action potentials to and from rest of the body
105
What is the role of peripheral nervous system
Ensures rapid communication between sensory receptors, CNS and effectors
106
What is peripheral nervous system composed of
Sensory and motor neurones that are usually bundled together in a connective tissue sheath to form nerves
107
What are sensory fibres that enter CNS
Dendrons of sensory neurones
108
What do dendrons of sensory neurones conduct
Action potentials from sensory receptors into CNS
109
What is sensory neurone structure
Neurones have cell body in dorsal root leaving to spinal cord and short axon connecting to other neurones in CNS
110
What does the motor nervous system do
Conducts action potentials from CNS to effectors and subdivided according to function of motor nerve
111
What does somatic nervous system consist of
Motor neurones that conduct action potentials from CNS to effectors, that are under voluntary control like skeletal muscles, these are mostly myelinated so rapid response and always single motor neurone connecting CNS to effector
112
What does the autonomic nervous system consist of
Motor neurones that conduct action potentials from CNS to effectors that aren’t under voluntary control, including glands, cardiac muscle and smooth muscle in blood vessel walls, airways and digestive system walls, control of many of these effectors don’t require rapid response and most non-myelinated neurones, atleast 2 neurones involved in connection between CNS and effectors, these neurones connect at small swellings called ganglia
113
How does autonomic nervous system mostly operate
Independently of conscious control
114
What is autonomic nervous system responsible for
Controlling majority of homeostatic mechanisms and so plays vital role in regulating internal environment of body
115
What is autonomic nervous system subdivided into and what is each of its roles
Sympathetic nervous system (prepares body for activity), parasympathetic nervous system (conserves energy)
116
What are parasympathetic and sympathetic nervous systems to each other
Antagonistic systems as action of 1 system opposes action of another
117
At rest how to para and sympathetic nervous systems work
Action potentials travel along neurone at low frequency and controlled by subconscious of brain
118
What is structure of sympathetic NS
Has many nerves leading out of CNS, each leading to different effector
119
What is structure of parasympathetic NS
Has few nerves leading out of CNS which divide up and lead to different effectors
120
What are other structural feature of sympathetic NS
Ganglia just outside CNS, short pre-ganglionic neurones, noradrenaline neurotransmitter, increase activity, most active in stress
121
Other structural features of parasympathetic NS
Ganglia in effector tissue, long pre-ganglionic neurones, acetylcholine neurotransmitter, decreases activity, most active in sleep or relaxation
122
What are effects of sympathetic NS
Increase HR and ventilation rate, dilates pupils, reduces digestive activity, orgasm
123
Effects of parasympathetic NS
decrease HR and ventilation rate, constructs pupils, increase digestive activity, sexual arousal
124
What are 4 main parts of brain
Cerebrum, cerebellum, hypothalamus/pituitary complex, medulla oblongata
125
What is cerebrum
Largest part of brain and organises most of higher thought processes like unconscious thought and memory
126
What is cerebellum
Coordinates movement and balance
127
What is hypothalamus/pituitary complex
Organises homeostatic response and controls various psychological processes
128
What is medulla oblongata
Coordinates many autonomic responses
129
How is the cerebrum divided
Has 2 hemispheres connected via major tracts of neurones called corpus callosum
130
What is the outermost layer of cerebrum
Consists of thin layer of nerve cell bodies called cerebral cortex
131
How high brain functions does cerebrum control
Conscious thought, conscious actions, emotional responses, intelligence, reasoning, judgement, decision making, factual memory
132
How is cerebral cortex subdivided
Subdivided into areas responsible for specific activity or body region: sensory area, association area, motor area
133
What is sensory area in cerebral cortex
Receive action potentials indirectly from sensory receptors, size of region allocated to receive input from different receptors age related to sensitivity of areas that input received form
134
What are association area in cerebral cortex
Compare sensory inputs with previous experience, interpret what input means and judge appropriate response
135
What are motor areas in cerebral cortex
Send action potentials to effectors (muscles and glands), sizes of regions allocated to deal with different effectors related to complexity of movements needed in body, motor areas on left side of brain control effectors on right side of body and vice versa
136
What does cerebellum contain and involved in
Contains over half of all neurones in brain, involved with balance and fine coordination of movement, for this must receive info from many sensory receptors and process info accurately
137
What are examples of sensory receptors that supply cerebellum info
Retina, balance organs in inner ear, spindle fibres in muscles which give info about muscle length and joints
138
Where is conscious decision to contract voluntary muscles initiated
Cerebral cortex but cerebral cortex doesn’t provide complex signals required to coordinate complex movements
139
What does cerebellum coordinate and give examples
Fine control of muscular movements like maintaining body position and balance, like cycling (judging positive of objects which moving body) and coordinating contraction and relaxation of antagonistic skeletal muscles when walking
140
What does fine control by cerebellum often require first
Learning and once learnt becomes second nature and involved in unconscious control to coordinate needs of complex nervous pathways which are strengthened by practice
141
What becomes programmed into cerebellum
Complexity of activity and neurones from cerebellum conduct action potentials to motor areas, so motor output to effectors can be finely controlled
142
How are cerebrum and cerebellum connected
By pons
143
What does hypothalamus control
Homeostatic mechanisms in body, it contains own sensory receptors and acts by negative feedback to maintain constant internal environment
144
How does temp regulation work in hypothalamus
Hypothalamus detects change in body temp and receives sensory input from temp receptors in skin which will imitate responses to temp change that regulate body temp in narrow range, these responses may be mediated by nervous system or hormonal system via pituitary gland
145
How is osmoregulation controlled by hypothalamus
Hypothalamus contains osmoreceptors that monitor water potential in blood, when water potential changes osmoregulatory centre initiates response to reverse change, response mediated by hormonal system via pituitary gland
146
What does the pituitary gland and in conjunction with and what are its 2 lobes
Conjunction with hypothalamus and posterior lobe and anterior lobe
147
What is posterior lobe of pituitary gland
Linked to hypothalamus by specialised neurosecretory cells, hormones like ADH manufactured in hypothalamus pass down neurosecretory cells and released into blood from pituitary gland
148
What is anterior lobe of pituitary gland
Produces own hormones released into blood in response to releasing factors produced by hypothalamus to pituitary, hormones from anterior pituitary control many physiological processes in body like response to stress, growth, reproduction and lactation
149
What does medulla oblongata control
Non-skeletal muscles by sending action potentials out through autonomic nervous system
150
What does medulla oblongata contain
Centres for regulating several vital processes like cardiac centre regulates HR, vasomotor centre regulates circulation and BP, respiratory centre controls rate and depth of breathing
151
How do the centres in medulla oblongata work
They receive sensory info and coordinate vital functions by negative feedback
152
What are reflex actions
Responses to changes in environment that don’t involve any processing in brain to coordinate movement
153
Why is nervous pathway short as possible
So reflex is rapid
154
What 3 neurones do reflex pathways have
Sensory, relay, motor,
155
What is the brains involvement in reflex action
Aware it’s happening but not involved in coordination
156
What is the purpose of reflex actions
Survival value, reflex used to get out of danger, stop damage to body and used to maintain balance
157
What do reflex actions include
Blinking reflex and knee jerk reflex
158
What is the blinking reflex
Causes temporary closure of eyelids to protect eye from damage
159
How does blinking reflex work
Passes through part of the brain, reflex is a cranial reflex but doesn’t involve thought and since receptors and effectors in same place it’s a reflex arc
160
What sudden environment changes stimulate blinking reflex
Foreign object touching eye (corneal reflex), bright light (optical reflex), loud noise, sudden movement close to eye
161
What is corneal reflex mediated by
Sensory neurone in cornea, when it enters pons, synapse connects sensory neurone to relay neurone which passes action potential to motor neurone, motor neurone passes back out of brain to facial muscles causing eyelid to blink
162
Why is the corneal reflex quick and what does it cause
It is short, and usually causes both eyelids to close
163
In corneal reflex where does sensory neurone pass action potential to
Myelinated neurones in pons which carry action potential to sensory region in cerebral cortex to inform higher centres of brain that stimulus occurred (reflex can be overridden by conscious control)
164
What do high parts of the brain do in corneal reflex if it want reflex inhibited
Send inhibitory signals in motor centre in pons, myelinated neurones carrying signals to/from cerebral cortex transmit action potentials more rapidly than non-myelinated relay neurones in pons, so, inhibitory action potentials can stop formation of action potential in motor neurone
165
What is purpose of optical reflex
Protects light sensitive cells from retina damage
166
How does optical reflex work
Stimulus detected by retina and reflex mediated by optical centre in cerebral cortex
167
Is optical or corneal reflex faster
Corneal is faster
168
What is knee jerk reflex
Spinal reflex, nervous pathway passes spinal cord not brain
169
What is knee jerk involved in
Reflex involved in coordination movement and balance
170
How does knee jerk reflex work
Quadriceps contract to straighten leg and this muscle attaches to lower leg by patella tendon that connects patella to lower leg bones at front of knee, when muscle at front of knee stretch specialised stretch receptors detect increase in muscle length, and if stretch unexpected reflex action causes contraction of muscle
171
What happens when we stand still in knee jerk reflex
Muscle in front of thigh will stretch if knee bends or body leans back, contraction of muscle straightens knee or brings body back upright, response must be rapid so body stays balanced
172
How many neurones does knee jerk pathway have and what are they
Sensory neurone and motor neurone (2)
173
How are high parts of brain involved in knee jerk action
It’s informed of reflex but as no relay neurone the reflex can’t be inhibited
174
What does inhibition of knee jerk reflex need
Rapid myelinated neurones passing inhibitory action potentials to synapse before motor neurone stimulated, in absence of relay neurone, motor neurone stimulated directly by sensory neurone and insufficient delay to enable inhibition
175
How does knee jerk reflex work when walking and running
Knee must bend and will stimulate muscle spindles but complex patterns of nervous impulses coming from cerebellum can inhibit reflex contractions, as action potentials sent to hamstring stimulating it to contract, inhibitory action potentials sent to synapse in reflex arc to prevent reflex contractions of opposing muscles
176
What do mammals complex sensory mechanisms do
Monitor changes in internal and external environment which provide input to brain which assimilates inputs and coordinates response for survival
177
What may input include info about to the brain
Blood glucose from islets of langerhans, info from stretch receptors in stomach or pain receptors in joints and skin
178
Are response to internal/external environment short or long term
Both, short like homeostatic mechanisms or long like reproduction behaviour
179
How many the brain coordinate responses through output to effectors
Action potentials in somatic NS, action potentials in para/sympathetic parts of autonomic NS, causing release of hormones via hypothalamus and pituitary gland
180
What is fight or flight response
Detecting threat to survival stimulated this response and leads to physiological changes so mammal prepares for activity
181
What are physiological changes with fight or flight
Pupils dilate, HR/BP rises, vasoconstriction, blood glucose increases, metabolic rate increase, erect pili muscle in skin contact, ventilation rate increases, endorphins released in brain
182
What is purpose of dilated pupils in fight or flight
More light enters eye making retina more sensitive
183
What is purpose of increased HR/BP in fight or flight
Increased blood flow to deliver more oxygen and glucose and remove CO2 and toxins
184
What is purpose of increased HR and BP in fight or flight
More blood flow to deliver oxygen and glucose and removal of CO2 and toxins
185
What is purpose of vasoconstriction in fight or flight
Diverts blood flow from skin and digestive system to muscles
186
What is purpose of increased blood glucose in fight or flight
Supplies energy for muscular contractions
187
What is purpose of increased metabolic rate in fight or flight
Converts glucose to ATP
188
What is purpose of erect pili muscles on skin contract in fight or flight
Makes hair stand up
189
What is purpose of increased ventilation rate in fight or flight
Increases gaseous exchange so more oxygen in blood for aerobic respiration
190
What is purpose of endorphins released in brain in fight or flight
Wound inflicted on mammal don’t prevent activity
191
How is fight or flight coordinated
Receptors that detect external threat (eyes, ears, nose), internal receptors may also detect threat (pain or sudden increase/decrease in blood pressure) and cerebrum uses this to coordinate response
192
What is the 4 steps to coordination of fight or flight
1.input feeds into sensory centres in cerebrum 2.cerebrum passes signal to associated centres 3.if threat recognised cerebrum stimulates hypothalamus 4.hypothalamus increases activity in sympathetic NS and stimulates release of hormones from anterior pituitary gland
193
What does autonomic nervous system control
Physiological mechanisms
194
What does increasing stimulation of sympathetic nervous system increase
Effector activity but nervous communication used for rapid responses not prolonged response
195
If fight or flight from danger needs a prolong response how does it work
Endocrine system, sympathetic nervous system stimulates adrenal medulla so adrenaline released and has wide range of effects on cells
196
What is adrenaline
A first messenger, it’s an amino acid derivative so can’t enter target cells and must cause effect inside cell without entering it
197
What is the 3 steps of adrenaline mechanism of action
1.adrenaline binds to adrenaline receptors on plasma membrane, receptor associated with G protein on inner surface of plasma membrane which is stimulated to activate enzyme adenyl cyclase 2.adenyl cyclase converts ATP to cyclic AMP which is 2nd messenger inside cell 3.cAMP causes effect inside cell by activating enzyme action precise effect depends on cell adrenaline bound to
198
What does the hypothalamus secrete into blood and what happens next
Secretes releasing factors which pass down portal vessel to pituitary gland and stimulate release of tropic hormones from anterior pituitary gland (stimulates activity in many endocrine glands)
199
What is corticoteopin
Releasing hormone from hypothalamus which causes release of adrenocorticotropic hormone (ACTH) which passes around blood system and stimulates adrenal cortex to release hormones like cortisol causing more glucose to be released from glycogen stores or fat and protein stires
200
What does thyrotropin releasing hormone cause
Causes release of thyroid stimulating hormone which stimulates thyroid gland to release more thyroid hormone (thyroxin) which acts on almost all body cells, increasing metabolic rate and making cells more sensitive to adrenaline
201
What important roles does the heart pumping blood round circulatory system have
Transport of oxygen and glucose, fatty acids and amino acids to tissue, removal of waste like CO2 to prevent toxic accumulation, transport of urea from liver to kidneys, distribute heat round body or to skin to be radiated away
202
What do requirements of cell and tissue vary on
Levels of activity, when physically active muscles need more oxygen and glucose to respire more releasing energy for contraction
203
How does the circulatory system control heart activity
Raising/lowering heart rate, altering force of contractions, altering stroke volume (volume of blood pumped per beat)
204
How is the heart muscle myogenic
Can initiate it’s own contractions
205
WhT has high myogenic rate, atrial or ventricular muscle
Atrial muscle
206
How does heart coordinate contractions
Hearts pacemaker (SAN) initiates wave of excitation that overrides myogenic action of cardiac muscle, SAN initiates action potential which travels over atrial walls through AVN and down purkyne fibres to ventricle walls causing contraction
207
What in blood causes heart rate to increase
Adrenaline
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At rest what controls heart rate
SAN, but frequency of excitation waves are altered by output from cardiovascular centre in medulla oblongata
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What do nerves from cardiovascular centre in medulla oblongata supply
SAN, these nerves are part of autonomic NS, nerves don’t initiate contraction but affect contraction frequency
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How do nerves in cardiovascular centre in medulla oblongata control frequency of contractions
Action potentials sent down sympathetic nerve cause release of noradrenaline at SAN, increasing HR, action potentials sent down vagus nerve release acetylcholine, reducing HR
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How do environmental factors impact HR
Input from sensory receptors fed to cardiovascular centre in medulla oblongata, interaction of inputs coordinated by cardiovascular centre to ensure output to SAN appropriate
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What do sensory input to cardiovascular centre include
Stretch receptors in muscles, chemoreceptors in carotid arteries, concentration of CO2 in blood, stretch receptors in walls of carotid sinus monitor BP
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How is stretch receptors in muscle input to cardiovascular centre
Detect limb movement, send impulses to cardiovascular centre informing it extra oxygen may be needed causing increased heart rate
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How is chemoreceptors in carotid arteries input to cardiovascular centre
Aorta and brain monitor blood pH, when we exercise muscles produce more CO2, some reacts with water in blood plasma producing carbonic acid reducing blood pH affecting oxygen transport, change detected by chemoreceptors which send action potentials to cardiovascular centre increasing HR
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How is concentration of CO2 in blood input to cardiovascular centre
When stop exercising CO2 concentration in blood drops reducing activity of accelerator pathway so HR falls
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How is stretch receptors in walls of carotid sinus input to cardiovascular centre
They monitor BP, carotid sinus is small swelling in carotid artery increasing BP, in exercise if pressure to high change detected and stretch receptors send action potentials to cardiovascular centre reducing HR
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What happens when mechanism for controlling heart rate fails
Artificial pacemaker must be fitted, pacemaker delivers electrical impulses to heart muscle and placed under skin and fat on chest, it’s either connected to SAN or directly to ventricular wall
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How are muscles composed
Cells arranged to form fibres which can contract become shorter producing a force
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How are muscle contractions achieved
By interactions between protein filaments actin and myosin in muscle cells
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How do muscles elongate
With antagonistic pair, so muscles usually arranged in opposite pairs, 1 contracts as other elongates (antagonist may be elastic recoil or hydrostatic pressure in a chamber)
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What are 3 types of muscle
Involuntary smooth muscle and cardiac muscle and voluntary skeletal muscle
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What is involuntary smooth muscle structure
Individual cells tapered at both ends (spindle shape), each cell has nucleus and bundles of actin and myosin,
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WhT are 2 layers of smooth muscle
Circular layer runs round intestines and contraction causes segmentation, longitudinal layer runs along intestines causing wave like contractions
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What is muscle contraction of smooth muscle like and where is it found
Slow and regular, doesn’t tire quickly and controlled by autonomic NS, found in walls of tubular structures and longitudinal and circular layers oppose each other
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What is structure of cardiac muscle
Individual cells form long fibres which branch forming cross bridges between fibres to help ensure electrical stimulation spreads evenly over walls of chambers
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How does cardiac muscle structure help contractions
Structure means contraction is squeezing action, cells joined by intercalated discs (specialised cell surface membranes fused to produce gap junctions allowing free diffusion of ions between cells, action potentials pass easily and quickly along and between cardiac muscle fibres
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How does cardiac muscle contact
Contracts and relaxes continuously through life and doesn’t fatigue easily and contracts powerfully
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How are purkyne fibres modified for cardiac muscle contractions
Carry electrical impulses to coordinate contraction of chamber walls, heart muscle is myogenic but contraction rate controlled by SAN
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How does cardiac muscle look under microscope
Striated
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What is voluntary skeletal muscle
Found at joints and contraction causes movement of skeleton by bending and straightening joint
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Structure of skeletal muscle
Arranged in antagonistic pairs, each fibre is multinucleate and surrounded by membrane called sarcolemma, muscle cell cytoplasm called sarcoplasm and cells have many mitochondria and extensive sarcoplasmic reticulum
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How are skeletal muscle fibres arranged
Into many myofibrils which are contractile elements, myofibrils divided into subunits called sarcomeres which have protein filaments myosin and actin arranged into patterns giving striated appearance
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How does skeletal muscle contact
Powerfully and quickly but fatigues easily
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What are skeletal muscle contractions stimulated by
Somatic nervous system, junctions between nervous system and muscle called neuromuscular junction (similar to synapse)
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What are the 5 steps to stimulation of contraction of voluntary skeletal muscle
1.action potential arriving at axon terminal opens calcium ion channels in membrane and calcium ions flood into axon end 2.vesicles of acetylcholine move to and fuse with end of membrane 3.acetylcholine diffuse across gap and fuse with receptors in sarcolemma 4.opens sodium ion channel allowing sodium ions to enter muscle fibre, causing depolarisation of sarcolemma 5.wave of depolarisation spreads along sarcolemma and down transverse tubules into muscle fibre
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What do motor neurones do in stimulating muscle contraction
Some stimulate single muscle fibres but many motor neurones divide and connected to several muscle fibres, all these muscle fibres contract together providing stronger contraction called motor unit
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What are myofibrils
Contractile units of skeletal muscle
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What are 2 types of protein filaments and myofibrils
Thin filaments lined up to make up light band held together by Z line, thick filament which make dark band, thick and thin filaments overlap but in middle of dark band no overlap (H zone), distance between 2 Z lines called sarcomere (functional unit of muscle), thick and thin filament surrounded by sarcoplasmic reticulum
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What are thin filaments myofibrils
Composed of actin, each filament has 2 chains of actin subunits twisted round each other, wound around a molecule of tropomyosin to which globular molecules of troponin attached
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How many polypeptides does each troponin complex have
3 polypeptides, 1 binds to actin, 1 to tropomyosin and 3rd binds to calcium when it’s available
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What are tropomyosin and troponin in thin filaments part of
Mechanism to control muscular contractions, at rest these molecules cover binding sites to which thick filaments can bind
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What is thick filament structure
Each thick filament has Bundle of myosin molecules, each myosin has 2 protruding heads which stick out at each end of molecule, these heads are mobile and can bind to actin when binding sites exposed
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What is sliding filament hypothesis
During contraction light band and H zone get shorter so Z lines move closer together and sarcomeres get shorter, during contraction thick and thin filaments side past one and other
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What is sliding action of thin and thick filaments caused by
Movement of myosin heads, when muscle stimulated tropomyosin moved aside, exposing binding sites on actin, myosin heads attach to actin and move causing actin to slide past myosin
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What are the 6 steps to controlling muscle contraction
1.when muscle stimulated action potential passes along sarcolemma and down transverse tubules into muscle fibre 2.action potential carried to sarcoplasmic reticulum which stores calcium ions and causes release of calcium ions to sarcoplasm 3.calcium ions bind to troponin altering shape pulling tropomyosin aside exposing actin binding sites 4. Myosin heads bind to actin forming cross bridges between filaments 5. Myosin heads move pulling actin filament past myosin filament 6.myosin dead’s detach from actin and can bind again further up actin filament
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What do cross bridges form between
Actin and myosin filaments, and once contraction occurred, calcium ions rapidly pumped back into sarcoplasmic reticulum allowing muscle to relax
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How does ATP supply energy for contractions
Part of myosin head acts as ATPase and hydrolyses ATP to ADP and Pi releasing energy
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4 steps to Myosin head hydrolysing ATP to ADP and Pi
1.myosin head attaches to actin filament forming cross bridge 2.myosin head moves causing thin filament to slide past myosin filament (power stroke) during which ADP and Pi released from myosin head 3.after power stroke new ATP molecule attaches to myosin head breaking cross bridge 4.myosin head then returns to original position as ATP hydrolysed releasing energy to make this movement occur, myosin head can now make new cross bridge further along actin filament
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Why must ATP be constantly regenerated in skeletal muscles
Many myosin heads involved in contractions so huge need for ATP and ATP available in muscle tissue only enough to support 1sec of contraction
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What are 3 mechanisms involved in maintaining ATP supply
Aerobic respiration in mitochondria, anaerobic respiration in sarcoplasm of muscle tissue, creatine phosphate in sarcoplasm
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How does aerobic respiration in mitochondria regenerate ATP In skeletal muscles
Muscle tissue has lots of mitochondria for aerobic respiration, Bohr effect helps release more oxygen from haemoglobin into blood but in intense activity rate of ATP production limited by delivery of oxygen to muscle tissue
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How does anaerobic respiration in sarcoplasm of muscle tissue regenerate ATP In skeletal muscles
It releases a little more ATP from respiratory substrates but leads to production of lactate which is toxic, only lasts few seconds before lactic acid builds up and causes fatigue
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How does creatine phosphate in sarcoplasm regenerate ATP In skeletal muscles
It acts as reserve store for phosphate groups, phosphate can be transferred from creatine phosphate to ADP molecules creating ATP molecules rapidly, enzyme creatine phosphatransferase involved, supply of creatine phosphate supports muscle contraction by further 2-4secs
