5.5 Flashcards
1
Q
what do plants respond to
A
biotic and abiotic factors and external stimuli
2
Q
give examples of stimuli to plants
A
-temperature (e.g in a high temperature they will deposit a thick layer of wax on their leaves)
-wind (in very windy conditions they may have vascular tissue which is more heavily lignified)
3
Q
describe tannins
A
(chemical defence) toxic to microorganisms and larger herbivores. In leaves, they are found in the upper epidermis, and make the leaf taste bad. In the roots they prevent infiltration by pathogenic microorganisms
4
Q
describe alkaloids
A
(chemical defence) they are derived from amino acids. In plants, scientists think they are a feeding deterrent to animals, tasting bitter. They are located in growing tips and flowers, and peripheral cell layers of stems and roots (N containing)
5
Q
describe pheromones
A
(chemical defence) chemicals which are released by one individual which can affect the behaviour or physiology of another
6
Q
what are the types of response in plants ( name the tropisms which are directional growth responses of plants)
A
-phototropism
-geotropism
-chemotropism
-thigmotropism
7
Q
what are tropisms
A
tropisms are directional growth responses of plants. The direction of the response is stimulated by the direction of the external stimulus.
8
Q
what is geotropism
A
roots rowing towards the pull of gravity. This anchors them in soil and helps them to take up water, which is needed for support (to keep cells turgid), as a raw material for photosynthesis and to help cool the plant. There will also be minerals such as nitrate in the water needed for synthesis of amino acids
9
Q
what is chemotropism
A
on a flower, pollen tubes grow down the style, attracted by chemicals, towards the ovary where fertilisation can take place
10
Q
what is thigmotropism
A
shoots of climbing plants such as ivy, wind around other plants or solid structures to gain support
11
Q
what is phototropism
A
shoots grow towards light ( they are positively phototropic ) which enables them to photosynthesise
12
Q
whats a positive tropic response and whats a negative trophic response?
A
positive tropic response- a plant responding towards a stimulus
negative trophic response- a plant responding away from a stimulus
13
Q
what are nastic responses
A
non- directional responses to external stimuli are nastic responses
14
Q
talk about the sensitive plant Mimosa pudica and its response to touch
A
it responds to touch with a sudden folding of the leaves, this response is thigmonasty
15
Q
what is thigmonasty
A
a non-direct(ional) response, in plants , to the stimulation of contact
16
Q
what coordinates plant responses and what produces them
A
hormones (chemical messengers to act on target cells) coordinate responses, they are produced by cells in a variety of tissues in the plant.
17
Q
state what happens after plant hormones reach their target cells and their effect and their influence
A
after they reach their target cells, they bind to receptors on the plasma membrane , specific hormones have specific shapes which can only bind to specific receptors with complimentary shapes on the membrane of particular cells, this specific binding ensures hormones only act upon the correct tissues. Some hormones can have different effects on different tissues; some can amplify each others effects. Hormones can influence cell division, cell elongation or cell differentiation
18
Q
name the 5 plant hormones
A
-cytokinins
-abscisic acid
-auxins e.g. IAA (indole-3-acetic acid)
-gibberellins
-ethene
19
Q
plants- what is the effect of the hormone:
cytokinins
A
-promote cell division
-delay leaf senescence
-overcome apical dominance
-promote cell expansion
20
Q
plants- what is the effect of the hormone:
abscisic acid
A
-inhibit seed germination and growth
-causes stomatal closure when the plant is stressed by low water availability
21
Q
plants- what is the effect of the hormone:
auxins e.g. IAA (indole-3-acetic acid)
A
-promotes cell elongation
-inhibits the growth of side-shoots
-inhibits leaf abscission (leaf fall)
22
Q
plants- what is the effect of the hormone:
gibberellins
A
-promote seed germination and growth of stems
23
Q
plants- what is the effect of the hormone:
ethene
A
-promotes fruit ripening
24
Q
how do hormones move around the plant (3 ways)
A
-active transport
-diffusion
-mass flow in the phloem sap or in xylem vessels
25
what are auxins responsible for
regulating plant growth
26
what did scientists discover abt auxins when testing plants dk
-firstly scientists stated that if you break the shoot tip (apex of a plant), the plant starts to grow side branches from the lateral buds.
-scientists suggested that auxins from the apical bud prevent lateral buds from growing. when the tip is removed, auxin levels in the shoot drops and the buds grow. they applied an auxin paste to the cut end of the shoot and lateral buds didnt grow. However due to the manipulation, buds may ahve grown due to expose to oxygen/another hormone. auxin transport inhibitor was placed below the apex of the shoot and lateral buds grew. due to this scientists suggested that normal auxin levels in lateral buds inhibit growth , whereas low auxin levels promote growth however auxin levels and growth inhibition may have no effect on each other, but could both be affected by a third variable . later a scientists remarked that auxin levels actually increased when a shoot tip was cut off, scientists now think 2 hormones are involved.
27
what other 2 hormones are important in regulating plant growth and what do they do apart from auxins
-abscisic acid inhibits bud growth
-cytokinins promote bud growth
28
what is apical dominance
inhibition of lateral buds further down the shoot by chemicals produced by the apical bud at the tip of the plant shoot
29
what happens when u apply cytokinins directly to buds
it can override the apical dominance effect
30
what is the relationship between cytokinins and auxins
And what happens when the apex is removed
High Auxin = Cytokinins accumulate in shoot apex.
Low Auxin = Cytokinins spread around plant and so allow side shoot growth..
-when the apex is removed, cytokinin spreads evenly around the plant.
31
what are gibberellins
plant hormones which are responsible for the control of stem elongation and seed germination
32
in japan, there is a fungus that causes a disease which makes rice grow very tall, what are the fungal compounds involved
gibberellins and gibberellic acid
33
what is gibberellic acid responsible for
plant stem growth ( they applied this to dwarf varieties of pants and they grew taller).
34
what do gibberellins cause growth in and how
in the internodes by stimulating cell elongation (by loosening cell walls) and cell division (by stimulating production of a protein that controls the cell cycle)
35
in terms of growth, what does the plant cell wall limit
it limits the cells ability to divide and expand.
36
where does growth happen in plants
at the meristems
37
talk abt apical meristems
- are at the tips or apices (singular: apex) of roots and shoots, and are responsible for the roots and shoots getting longer
38
talk abt where lateral bud meristems are found and what they can give rise to
found in the buds
give rise to side shoots
39
talk abt what lateral meristems form and what they are responsible for
form a cylinder near the outside of roots and shoots
responsible for roots and shoots getting wider
40
intercalary meristems are found in some plants, where are they located and what are they responsible for
located between nodes, where the leaves and buds branch off the stems.
growth between the nodes is responsible for the shoot getting longer
41
whats a klinostat
a machine that causes something to spin very slowly so that the effect of gravity is applied equally to all sides of the plant.
42
whats a klinostat and what can it investigate?
a machine that causes something to spin very slowly so that the effect of gravity is applied equally to all sides of the plant.
-this can investigate geotropic responses
43
what would you expect to see when one plant has been in a kilostat and one plant hasn't
plant with kilostat: both root and shoot grow horizontally
plant without kilostat: (gravity is only applied to one side) the root bends downwards because the upper side of the root has elongated more than the lower side. The shoot bends upwards, because the lower side of the soot has elongated more than the upper side
44
in terms of growth, what happens to a plant where its given light but only from one side
the shoot has bent towards the light as the shady side of the shoot has elongated more than the illuminated side,
45
what did Darwins experiments confirm that the shoot tip was responsible for
confirmed the shoot tip was responsible for phototrophic responses by causing cell elongation on the shaded side of the shoot which makes the shoot bend towards the light
46
for phototropism to occur, what did Boysen-Jensen remark
he confirmed that water and/or solutes need to be able to move backwards from the shoot tip for phototropism to happen- he showed that the signal was a mobile chemical as when a permeable block (e.g, gelatin) was inserted, the shoot tip still showed positive phototropism, whereas with an impermeable block (e.g. mica), no phototropism occured
47
when a permeable gelatine block was inserted behind a shoot tip, what did it show
still showed positive phototropism
48
in terms of phototropic response, was there one when an impermeable mica block was inserted on a shoot tip
no phototropic response
49
what is the role of auxins
auxins:
-promote cell elongation
-regulate plant growth
-inhibit growth of side shoots
-inhibit leaf abscission (leaf fall)
50
what is senescence
the gradual decline of all organ systems leading inevitably to death
51
how did scientists experiment on auxins
-applied auxin paste to a cut shoot, this prevented side shoot growth (contributes to apical dominance)
-applied auxin paste and a ring of auxin transport inhibitor to a cut shoot. This allowed lateral growth
52
what did scientist conclude on auxins
-normal auxin levels inhibit lateral bud growth, but low levels promote growth
-however scientists now think 2 other hormones are involved
53
what is the role of abscisic acid
-inhibits bud growth and seed germination
-causes stomatal closure when the plant is stressed by low water availability
54
what is the relationship between auxins and abscisic acid
high auxin= high abscisic acid= low lateral bud growth
-when the apical bud is removed, (removing auxins) the level of abscisic acid also drops.
55
what is the role of cytokinins
-promote cell division
-overcome apical dominance
-delay leaf senescence
-promote cell expansion
56
what is the relationship between auxins and cytokinins
high auxin= cytokinins accumulate in shoot apex
low auxin= cytokinins spread around plant and so allow side shoot growth
57
what is the role of gibberellins
-promote seed germination
-promote growth of stems
58
How did scientists experiment on Gibberellins
found GA1 existed at higher levels in taller pea plants (Le) than shorter pea plants (le)
59
How did scientists conclude on Gibberellins
they worked out the Le gene was responsible for producing the enzyme that converted GA20 to GA1
60
what happens when grafting an Le plant with no GA20 onto an le plant
the Le plant uses the spare GA20 from the normal plant, and contains the enzyme to convert GA20 to GA1, and therefore grew tall
61
how do gibberellins stimulate seed germination
when the seed absorbs water, the gibberellins enable the production of amylase, which can break down starch into glucose
this provides substrate for respiration and protein synthesis
62
whats the role of ethene
promotes fruit ripening
63
auxin is produced in the tip, what happens when the tip is cut
when the tip is cut, auxin levels drop and the bud grows
64
what happened when auxin paste was applied to the cut shoot
the lateral buds didn't grow ( this is cus the conc is too HIGH)
65
what role does the secondary hormone of abscisic acid play a part of
- high abscisic acid= lateral bud growth inhibition
-it is thought that high auxin levels encourage high abscisic acid levels thus when tip is cut, abscisic acid levels drop and growth is uninhibited
66
what role does the secondary hormone of cytokinins play a part of
cytokinin= bud growth promotion
-produced in the roots, cytokinins travel to where auxin is most concentrated. when the apical tip is cut, cytokinins are spread more evenly and promote growth
67
talk abt auxin to abscisic acid to cytokinins and what that leads to when plant tip is intact
high auxin levels
\/
high abscisic acid levels
\/
low cytokinins in lateral bud
\/
inhibit lateral bud growth
68
talk abt auxin to abscisic acid to cytokinins and what that leads to when plant tip is removed
low auxin levels (more normal levels)
\/
low abscisic acid levels
\/
higher cytokinin levels in lateral buds
\/
lateral buds grow
69
what are gibberellins responsible for
stem elongation (by loosening cell walls) and seed germination (cell division by stimulating production of a protein that controls the cell cycle)- this happens in internodes
70
what are the 4 steps of seed germination
1. the seeds absorb water
2. the embryo releases gibberellin (GA) which travels to the aleurone layer in the endosperm of the seed.
3. gibberelin aids the production of amylase that breaks down starch into glucose
4. glucose is used for respiration
71
how did scientists test for GA1 levels
they found that plants with higher GA1 levels were taller- they found that the La gene was responsible for producing an enzyme converting GA20 to GA1
71
what happened when gibberellic acid was added to dwarf plants
they grew taller
72
what caused lengthening? GA1 or GA20
GA1
73
where does growth in length occur
apical meristems
74
where does growth in side shoots occur
lateral bud meristems
75
auxin is produced at the apex of the shoot, auxin travels to the cells in a zone of elongation, what doe this lead to
when moving to the zone of elongation this causes them to elongate and making the shoot grow
76
what does auxin do when light is equal on all sides
auxin promotes shoot growth evenly
77
when light is shone from one direction onto a plant, there is a light side and a shaded side, where do auxins move o and what does this cause
they move to the shaded side, this causes the cells there to elongate more quickly, this makes the shoot bend towards the light (the extent at which the cells elongate is dependent on the conc of auxins)
78
talk abt the mecanism of auxin
Auxin increases the stretchiness of the cell wall by promoting the active transport of H+ by an ATPase enzyme on the plasma membrane, into the cell wall. The resulting low pH provides optimum conditions for wall- loosening enzymes (expansins) to work. these enzymes break bonds within the cellulose ( at the same time, the increased hydrogen ions also disrupt hydrogen bonds within cellulose), so the walls become less rigid and can expand as the cell takes in water.
79
what is the main component of white light that causes phototrophic responses
blue light
80
what two enzymes are promoted by blue light
phototropin 1 and photropin 2
81
where is there lost of phototropin activity and what redistribution cause
lots on the light side but not a lot on the dark side, this gradient causes the redistribution of auxins through their effect on PIN proteins
82
where can PIN proteins be found and what can they do
these transmembrane proteins are found dorsally, ventrally or laterally on the plasma membrane of cells and they control the efflux of auxin from each cell, essentially sending auxin in different directions in the shoot, depending on their location on the plasma membrane
83
describe how is auxin involved in geotropic responses of roots
when a root is lying flat, auxin accumulates on the lower side, where it inhibits cell elongation . The upper side continues to grow and the root bends downwards
84
talk abt how the effects on auxin in roots and shoots contrast each other
they are the direct opposite as root and shoot cells in the elongation zone exhibit different responses to the same conc. of auxin (look at graph)
85
what can artificial auxins do
can be used to prevent leaf and fruit drop (this can occur in high conc. of auxin) and to promote flowering for commercial flower production.
86
why are artificial auxins useful in terms of fruit growth
they can be used to produce fewer but larger fruit instead of many small fruit
87
what are the three commercial uses of auxins
1. Auxin and cuttings
-dipping the end of a cutting in rooting powder encourages root growth
2. Auxin and seedless fruit
-treating unpollinated flowers with auxin can promote the growth of seedless fruit (parthenocarpy). Applying auxin promotes ovule growth, which triggers automatic production of auxin by tissues in the developing fruit, helping it complete the developmental process.
3. Auxin and herbicides
- auxins are used as herbicides to kill weeds. Because they are an made, plants find them more difficult to break down, and they can act within a plant for longer. They promote stem growth so that the stem cant support itself, buckles and dies
88
what are the commercial uses of cytokinin's
- cytokinin's can delay leaf senescence thus they are used to prevent the yellowing of lettuce leaves after they have been picked.
-cytokinin's are used in tissue culture to help mass produce plants.
-cytokins promote bud and shoot growth from small pieces of tissue taken from a patient plant. This produces a short shoot with a lot of side branches, which can be split into lots of small plants. each of these is then grown separately.
89
what 4 things are gibberellins used in (commercial)
- fruit production
-brewing
-sugar production
-plant breeding
90
how are gibberellins used in fruit production
- they delay senescence in citrus fruit, extending the time fruits can be left unpicked, and making them available for longer in the shops
-gibberellins acting with cytokinin's can make apples elongate to improve their shape.
-without gibberellins, bunches of grapes are very compact: this restricts the growth of individual grapes. with gibberellins, the grape stalk elongate, they are less compacted, and the grapes get bigger
91
how are gibberellins used in brewing
during germination, the seed produces amylase that breaks down starch to maltose, usually due to gibberellin. By adding gibberellin, the process is sped up, malt is then produced by drying and grinding the seeds ( germinated cereal grains)
92
how are gibberellins used in sugar production (SPRAYING)
spraying sugar cane with gibberellins stimulates growth between the nodes, making the stems elongate. this is useful as sugar cane stores sugar in the cells of the internodes ( subsections of the stems), making more sugar available from each plant.
93
how are gibberellins used in plant breeding
sometimes breeding can take a long time (esp in conifer plants). gibberellins ca speed up the process by inducing seed formation on young trees.
stopping plants making gibberellins is also useful, spraying plants with gibberellin synthesis inhibitors can keep flowers short and stocky and ensures that internodes of crop plants stays short, helping to prevent lodging
94
whats lodging
it occurs in wet summers where stems bend over because of the weight of water collected on the ripened seed heads, making the crop difficult to harvest
95
ethene
ethene
96
what are the 4 commercial uses of ethene
-speeding up fruit ripening in apples
-promoting fruit drop in cotton, cherry and walnut
-promoting female sex expression in cucumbers, reducing the chance of self-pollination (pollination makes cucumbers taste bitter) and increasing yield
97
why can restricting ethenes effects be useful
storing a fruit at a low temperature , with little oxygen and high carbon dioxide levels prevents ethene synthesis and thus prevents fruit ripening, this means fruits can be stored for longer and is essential for shipping. Other inhibitors such as silver salts can increase shelf life of cut flowers
98
what 4 things must a communication system enable
- detection of changes in environment
-cell signaling to occur between all parts of the body
-coordination of a range of effectors to carry out responses to the sensory input
-suitable responses
99
to ensure survival when there is a change in environment, what should responses be
rapid and well coordinated
100
what are some examples of the role of the nervous system
-coordinated muscle action
-control of balance and posture
-temperature regulation
-coordination with the endocrine system
101
what is the most obvious division of the nervous system
the central nervous system (CNS) and the peripheral nervous system (PNS)
102
what is the PNS further divided into
the sensory system and the motor system
103
what is the motor system divided into
into the somatic nervous system and the autonomic nervous system
104
what is the CNS divided into
the brain and the spinal cord
105
much of the brain is composed of which types of neurons
-relay neurons which have multiple connections enabling complex neural pathways
106
are relay neurons myelinated or non- myelinated and what does this mean it looks like
mostly non-myelinated cells and the tissue looks grey in colour, this is known as grey matter.
107
what's the autonomic nervous system
part of the nervous system responsible for controlling the involuntary motor activities of the body.
108
what's the central nervous system
the central part of the nervous system composed of the brain and spinal cord
109
whats the peripheral nervous system
the sensory and motor nerves connecting the sensory receptors and effectors to the CNS. The sensory and motor neurons are usually bundled together in a connective tissue sheath to form nerves
110
what's the somatic nervous system
the motor neurones under conscious control.
111
what in the spinal cord makes up the central grey matter
the spinal cord has many non-myelinated relay neurons which make up central grey matter
112
what makes up a region of white matter in the spinal cord
there is a large number of myelinated neurons making up an outer region of white matter
113
what allows for rapid communication over long distances in the spinal cord
myelinated neurons carrying action potentials up and down the spinal cord
114
what is the spinal cord protected by
the vertebral column
115
what is between each vertebrae in the spinal cord
between each vertebrae in the spinal cord, peripheral nerves enter and leave the spinal cord carrying action potentials to and from the rest of the body
116
what is the role of the PNS
is to ensure rapid communication between the sensory receptors, the CNS and the effectors
117
what are the sensory fibers of entering the CNS referred to and what do they do/what do they conduct
sensory fibers entering the CNS are dendrons of the sensory neurons. these neurons conduct action potentials from the sensory receptors into the CNS. These neurons have their cell body in the dorsal root leading into the spinal cord and a short axon connecting to other neurons in the CNS.
118
Simply, what does the motor nervous system do?
The motor nervous system conducts action potentials from the CNS to the effectors.
119
what are the two further subdivisions of the motor nervous system (the two functions of the motor nerves)
-the somatic nervous system
-the autonomic nervous system
120
one subdivision of the motor nervous system is the somatic nervous system , describe this system
- consists of motor neurons that conduct action potentials from the CNS to the effectors that are under voluntary (conscious) control, such as the skeletal muscles. these neurons are mostly myelinated, so that responses can be rapid. There is always one single motor neuron connecting the CNS to effector
121
difefernce between nerrve and nurone
wdwsd
122
one subdivision of the motor nervous system is the autonomic nervous system , describe this system
consist of motor neurons that conduct action potentials from the CNS to effectors that are not under voluntary control. The control of many of these effectors does not require rapid responses, and the neurons are mostly non-myelinated. There are at least two neurons involved in the connection between the CNS and the effector. These neurons are connected at small swellings called ganglia.
123
which effectors are involved in the autonomic nervous system that are not under voluntary control
this includes glands, the cardiac muscle and smooth muscle in the walls of blood vessels, the airway and the wall of the digestive system. (bronchi)
124
define autonomic
'self-governing'
125
what is the autonomic nervous system responsible for ( roles it plays in the body )
for controlling the majority of homeostatic mechanisms and so plays a vital role in regulating the internal environment of the body. ( it acts independently of conscious control)
126
what is the autonomic nervous system further divided into
the sympathetic system (prepares body for activity)
the parasympathetic system. (conserves energy)
127
in general in both the sympathetic system and the parasympathetic system, how would u describe the action potentials at rest and what are they controlled by
at rest, action potential are passed along both neurons at low frequencies- this is controleld by the brain
128
how is the the sympathetic system and the parasympathetic system related to each other
they are antagonistic (the action of one system opposes the other).
129
what alters the balance of stimulation for the sympathetic system and the parasympathetic system
information from external or internal receptors or stress
130
compare the nerves in the sympathetic system and the parasympathetic system
sympathetic system:
- consist of many nerves leading out of the CNS, each leading to a separate effector.
parasympathetic system:
-consists of a few nerves leading out of the CNS, which divide up and lead to different effectors
131
compare where the ganglia is in the sympathetic system and the parasympathetic system
sympathetic system:
- ganglia just outside the CNS
parasympathetic system:
-Ganglia in the effector tissue
132
what is the ganglia
ddss
133
compare the length of the post-ganglionic neurons in the sympathetic system and the parasympathetic system
sympathetic system:
-long post-ganglionic neurons (variable in length, dependent upon the position of the effector)
parasympathetic system
-short post-ganglionic neurons
134
compare what neurotransmitter is used in the sympathetic system and the parasympathetic system
sympathetic system:
-uses noradrenaline as the neurotransmitter
parasympathetic system:
-uses acetylcholine as the neurotransmitter
135
what does kind of activity does the sympathetic system promote compared to the parasympathetic system
sympathetic system:
-increases activity- prepares the body for activity
parasympathetic system:
-decreases activity- conserves energy
136
compare when the sympathetic system and the parasympathetic system is most active
sympathetic system:
-most active at times of stress
parasympathetic system:
-most active during sleep or relaxation
137
what are the effects of the sympathetic system
sympathetic system effects:
-increases heart rate
-dilates pupils
-increases ventilation rate
-reduces digestive activity
-orgasm
138
what are the effects of the parasympathetic system
parasympathetic system effects:
-decreases heart rate
-constricts pupils
-reduces ventilation rate
-increases digestive activity
-sexual arousal
139
what are the 4 main parts of the brain
-the cerebrum
-the cerebellum
-the hypothalamus and pituitary complex
-the medulla oblongata
140
whats the cerebrum, what does it do
the cerebrum is the largest part of the brain and organizes most of our higher thought processes, such as conscious thought and memory.
141
what does the cerebellum do
the cerebellum coordinates movement and balance
142
what does the hypothalamus and pituitary complex organize
it organizes homeostatic responses and controls various physiological processes.
143
what does the medulla oblongata do
coordinates many autonomic responses. it controls physiological processes. It consists of 3 centres
144
label the brain
the brain
145
describe the structure of the cerebrum
- has two cerebral hemispheres, which are connected via major tracts of neurons called the corpus callosum. The outermost layer of the cerebrum consists of a thin layer of nerve cell bodies called the cerebral cortex.
146
the cerebrum controls 'higher brain' functions, what does this include
-conscious thought
-conscious actions ( including the ability to override some reflexes)
-emotional responses
-intelligence, reasoning, judgement and decision making
-factual memory
147
what are the 3 subdivisions of the cerebral cortex (these are responsible for specific activities and body regions)
-sensory areas
-association areas
-motor areas
148
what's the function of the sensory areas of the cerebral cortex
receive action potentials indirectly from sensory receptors. The sizes of the regions allocated to receive input from different receptors are related to the sensitivity of the area that inputs are received from.
149
what's the function of the association areas of the cerebral cortex
compare sensory inputs with previous experience, interpret what the input means and judge an appropriate response
150
what's the function of the motor areas of the cerebral cortex
send action potentials to various effectors ( muscles and glands). the sizes of the regions allocated to deal with different effectors are related to the complexity of the movements needed in parts of the body.
151
what do motor areas on the left side of the brain control
controls the effectors on the right side of the body
152
whats the pituitary gland?
What does the anterior and posterior lobe do?
an endocrine gland at the base of the brain, below but attached to the hypothalamus; the anterior lobe secretes many hormones; the posterior lobe stores and releases hormones made in the hypothalamus.
153
what is the cerebellums' function, give examples of sensory receptors supply the info to the cerebellum
it must receive information from many sensory receptors and process info accurately. the sensory receptors that supply info cerebellum include the retina, balance organs in the inner ear, and spindle fibers in the muscles, which give information about muscle length and the joints
154
the conscious decision to contract voluntary muscles is initiated in the _______
cerebral cortex
155
the conscious decision to contract voluntary muscles is initiated in the cerebral cortex, but what does the cerebral cortex not provide
doesn't provide the complex signals required to coordinate complex movements.
156
the cerebellum coordinates the fine control of movements such as:
-maintaining body position and balance
-judging the position of objects and limbs while moving about
-tensioning muscles in order to use tools and play musical instruments effectively
-coordinating contraction and relaxation of antagonistic skeletal muscles when running or walking.
157
fine control of muscular movements require _________ but once taught they become ___________
1. learning
2. second nature
158
the fine control of muscular movements requires what type of nervous pathways
requires nervous complex pathways ( these are strengthened by practice)
159
how can effectors be finely controlled when the cerebellum finely controls muscular movements
the complex activity becomes programmed into the cerebellum, and neurones from the cerebellum conduct action potentials to the motor areas, so that motor output to the effectors can finely be controlled.
160
what are the cerebrum and cerebellum connected by
connected by the pons
161
what does the hypothalamus control
controls homeostatic mechanisms in the body and contains its own sensory receptors
-it controls temp regulation and osmoregulation
162
how does the hypothalamus maintain a constant internal environment (simple)
via negative feedback
163
how does the hypothalamus regulate temperature
the hypothalamus detects changes in the core body temperature. However, it also receives sensory input from temp receptors in the skin. It will initiate responses to temp change that regulate body temp within a narrow range. These responses may be mediated by the nervous system or by the hormonal system (vis the pituitary gland)
164
how does osmoregulation occur by the hypothalamus
the hypothalamus contains osmoreceptors that monitor the water potential in the blood.. When the water potential changes, the osmoregulatory center initiates response that reverses the change. The responses are mediated by the hormonal system via the pituitary gland
165
the pituitary gland acts within conjunction of the hypothalamus, how many lobes does the pituitary gland consist of?
-consists of 2 lobes
166
what are the two lobes that the pituitary gland is made up of
-the posterior lobe
-the anterior lobe
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describe the posterior lobe and its function
its linked to the hypothalamus by specialised neurosecretory cells. Hormones such as ADH, which are manufactured in the hypothalamus, pass down the neurosecretory cells and are released from the pituitary gland into the blood
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describe what the anterior lobe produces and its function
produces its own hormones, which are released into the blood in response to releasing factors produced by the hypothalamus. These releasing factors are hormones that need to be transported only a short distance from the hypothalamus to the pituitary.
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what do hormones from the anterior pituitary control
they control a large number of physiological processes in the body, including the response to stress, growth, reproduction and lactation
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what muscles does the medulla oblongata control
controls the non-skeletal muscles ( the cardiac muscles and involuntary muscles)
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how does the medulla oblongata control the non-skeletal muscles
by sending action potentials out through the autonomic nervous system
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the medulla oblongata contains centres for regulating several vital processes, including:
-the cardiac centre, which regulates heart rate
-the vasomotor centre, which regulates circulation and blood pressure
-the respiratory centre, which controls the rate and depth of breathing
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when the centres of the medulla oblongata receive sensory information, what do they do
they coordinate vital functions by neg feedback**
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what are reflex actions
reflex actions are responses to changes in environment that do not involve any processing in the brain to coordinate the movement.
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for reflex actions why is the nervous pathway as short as possible
so that reflex is rapid
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what three neurons do reflex pathways consist of
sensory neuron-> relay neuron-> motor neuron
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during a reflex action, does the brain play a role
no but the brain may be informed that the reflex has happened but its not involved in coordinating the response
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what role do reflex actions have
a survival role e.g to get u out of danger
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what are 2 examples of reflex actions
-blinking reflex
-knee jerk reflex
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what does the blinking reflex do
causes temporary closure of the eyelids to protect the eyes from damage
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what does the nervous pathway for the blinking reflex pass through
passes through part of the brain, its the cranial reflex
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what is a cranial reflex
a reflex mediated by neurons that pass into the brain
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what is the direct pathway of the blinking reflex- what doesn't it involve and whats it called
its a cranial reflex as it passes through part of the brain it doesn't pass through higher parts of the brain), since the receptor and effector are in the same place, this is called a reflex arc
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blinking may be stimulated by sudden changes in the environment such as
- a foreign object touching the eye (the corneal reflex)
-sudden bright light (the optical reflex)
-loud sounds
-sudden movements close to the eye
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state how the corneal reflex occurs
The reflex is mediated by sensory neurons from the cornea, which enters the Pons. A synapse connects the sensory neuron to a relay neuron, which passes the action potential to the motor neuron. the motor neuron passes back out the brain to the facial muscles causing the eyelid to blink
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what is the pons
a part of the brain stem that connects the cerebellum and cerebrum
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describe features of the corneal reflex pathway and what this means
a very short and direct pathway, so the corneal reflex is very rapid
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the corneal reflex causes both eyes to blink even if...
one cornea is affected
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during the corneal reflex, what are sensory neurons also involved in apart from mediating a reflex
also pass the action potential to myelinated neurons in the pons
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what is the function of the myelinated neurons during the corneal reflex
carry the action potential to the sensory region in the cerebral cortex, to inform higher centers of the brain that the stimulus has occurred
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during the corneal reflex, what can causes reflexes to be overridden
concious control
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during the corneal reflex, what can higher parts of the brain (cerebral cortex) do?
can send inhibitory signals to the motor center in the pons. The myelinated neurons carrying impulses to and from the cerebral cortex transmit action potentials much more rapidly than the non-myelinated relay neuron in the pons. thus the inhibitory action potential can prevent the formation of an action potential in the motor neuron.
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what is the optical reflex, what's its function
protects light sensitive cells of the retina from damage. The stimulus is detected by the retina and the reflex is mediated by the optical center in the cerebral cortex.
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compare the speed of the optical reflex and the corneal reflex
the corneal reflex is a little faster
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what is the knee jerk reflex
a reflex action that straightens the leg when the tendon below the knee cap is tapped
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what type of reflex is the knee jerk reflex
its a spinal reflex
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what is the spinal reflex
where the nervous pathway passes through the spinal cord instead of the brain
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what is the knee jerk reflex involved in coordinating
involved in coordinating movement and balance
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describe the action in the leg of the knee jerk reflex
the muscle at the front of the thigh ( quadriceps) contracts to straighten the leg. this muscle is attached to the lower leg via the patella tendon that connects the patella to the lower leg bones at the front of the knee.
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what happens when muscles at the front of the thigh are stretched
when muscles at the front of the thigh are streched, specialized stretch receptors called muscle spindles detect the increase in length of the muscle. if this streching is unexpected, the reflex action causes contraction of the same muscle
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what mechanism allows us to balance on two legs
the knee jerk reflex, this is rapid fro balance
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what neurones are presnet for the knee jerk reflex
sensory neuron -> motor neuron
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why is the knee jerk reflex quicker than other reflexes
there is one less synapse involved
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why can the brain not inhibit the knee jerk reflex
because there is no relay neurone
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why can the brain not inhibit the knee jerk reflex
because there is no relay neuron
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what is the inhibition of the knee jerk reflex reliant on
inhibition relies on rapid myelinated neurons carrying the inhibitory action potentials to the synapse before the motor neuron is stimulated (pre-emptively)
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what happens in the absence of a relay neuron in the knee jerk reflex (once the reflex begins, it cant be inhibited)
the motor neuron is stimulated directly by the sensory neuron and there is insuffienct delay to enable inhibition.
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what is able to inhibit reflex contractions, describe (knee jerk)
the complex pattern of nervous impulses coming from the cerebellum. As action potentials are sent to the muscles behind the thigh (hamstring), stimulating it to contract, inhibitor action potentials are sent to the synapse in the reflex arc to prevent the reflex contraction of opposing muscle. (occurs pre-emptively)
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what will stimulate the msucle fibres (knee jerk)
the knee bending wile walking or running.
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when tapping knee cap, can the response be inhibited? ( knee jerk)
no
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the brain coordinates responses through output to the effectors. This output may include:
-action potentials in the somatic nervous system
- action potentials in the sympathetic and parasympathetic parts of the autonomic nervous system
-release of hormones via the hypothalamus and pituitary gland
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what type of change does fight or flight lead to
a physiological change
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what are the 8 physiological changes associated with the fight or flight response
-pupils dilate
-heart rate and blood pressure increases
-arterioles to the digestive system and skin are constricted, whilst those to the muscles and liver are dilated
-blood glucose levels increase
-metabolic rate increases
-erector pili muscles in the skin contract
-ventilation rate and depth increase
-endorphins (natural painkillers) are released in the brain
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how does the physiological change of pupils dilating associated with fight or flight give survival value
allows more light to enter eyes making the retina more sensitive
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how does the physiological change of increasing heart rate and blood pressure associated with fight or flight give survival value
increases rate of blood flow to deliver more oxygen and glucose to the muscles to remove co2 and other toxins
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how does the physiological change of arterioles to the digestive system and skin being constricted whilst those to the muscles and liver dilated associated with fight or flight give survival value
diverts blood flow away from the skin and digestive system towards the muscles
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how does the physiological change metabolic rate increasing associated with fight or flight give survival value
converts glucose to usable forms of energy such as ATP
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how does the physiological change of increasing blood glucose levels associated with fight or flight give survival value
Supplies energy for muscular contraction
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how does the physiological change of erector pili muscles contracting associated with fight or flight give survival value
makes hairs stand up- which is a sign of aggression
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how does the physiological change of ventilation rate and depth increase associated with fight or flight give survival value
increases gaseous exchange so that more oxygen enters the blood and supplies aerobic respiration
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how does the physiological change of release of endorphins (natural painkillers) via the brain associated with fight or flight give survival value
wounds inflicted on the mammal do not prevent activity
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how does the cerebrum use sensory input to coordinate a fight or flight response (there are 4 steps)
1. inputs feed into the sensory centers in the cerebrum
2. the cerebrum passes signals to association centers
3. if a threat is recognized, the cerebrum stimulates the hypothalamus
4. the hypothalamus increases activity in the sympathetic nervous system and simulates the release of hormones from the anterior pituitary gland
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what does increasing stimulation of the sympathetic nervous system increase activity of?
it will increase the activity to the nervous receptors
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what speed of a response is the nervous system used for
rapid response rather than a prolonged response
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sometimes fight or flight may need a prolonged response, how is this achieved?
via the endocrine system
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state the mechanism of adrenaline action
1. adrenaline binds to the adrenaline receptor on the plasma membrane. This receptor is associated with a G protein on the inner surface of the plasma membrane , which is simulated to activate the enzyme adenyl cyclase
2.adenyl** cyclase converts ATP to cyclic AMP (cAMP) which is the second messenger inside the cell
3. cAMP causes an effect inside the cell by activating enzyme action. The precise effect depends upon the cell that adrenaline has bound to.
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why is adrenaline unable to eneter the target cell
its an amino acid derivative. Must cause an effect inside the cell, without entering the cell itself.
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how are trophic hormones released from the anterior pituitary
the hypothalamus secretes releasing hormones (also known as releasing factors) into the blood. These pass down the portal vessel to the pituitary gland which stimulates the release of trophic responses.
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what do trophic hormones stimulate activity in
in endocrine organs
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what are two trophic hormones
Cortiotropin-releasing hormone( CRH)
-Thyrotropin-releasing hormone (TRH)
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what is the effect of Cortiotropin-releasing hormone (CRH)
- causes the release of adrenocorticotrophic hormone (ACTH)
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what is the effect of adrenocorticotrophic hormone (ACTH)
passes around the blood system and stimulates the adrenal cortex to release a number of different hormones
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what is the effect of cortisol (a Glucocorticoid)
regulates the metabolism of carbohydrates, more glucose is released from glycogen stores
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what is the effect of TRH
causes the release of TSH
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what is the effect of TSH
stimulates the thyroid gland to release more thyroid hormone
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what is the effect of thyroxine (a thyroid hormone)
acts on nearly every cell of the body, increasing the metabolic rate and making the cells more sensitive to adrenaline
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what are the 4 important roles of the heart pumping blood around the body
- transport of o2 and nutrients (glucose, fatty acids and amino acids) to the tissue
-removal of waster products such as co2 to prevent accumulation that may become toxic
-transport urea from liver to kidney
-distribute heat around body or deliver it to the skin to be radiated away
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what can heart action be modified by (3)
-raising or lowering of the heart rate. This is the number of beats per min
-altering the force of contractions of the ventricular walls
-altering the stroke volume (volume of blood pumped per beat)
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what has a higher myogenic rate, the atrial muscle or the ventricular muscle?
the atrial muscle
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what can the wave of excitation in the SAN overide
the myogenic action of the cardiac muscle
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what can the SAN initiate
an action potential
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what hormone does the heart muscle directly respond to
the hormone adrenaline which increases heart rate
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at rest the heart rate is controlled by the ...
SAN
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what can the frequency of the waves of excitation be altered by
by the output from the cardiovascular center in the medulla oblongata
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what supplies the SAN and what do they do
nerves from the cardiovascular center in the medulla oblongata supply the SAN, these nerves are part of the autonomic nervous system. The nerves do not initiate contraction but can affect the frequency of contractions.
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how do nerves increase the heart rate
action potentials sent down a sympathetic nerve (the accelerans nerve) cause the release of the neurotransmitter noradrenaline at the SAN. this increases heart rate
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how do nerves decrease heart rate
action potentials sent down the vagus nerve release the neurotransmitter acetylcholine, which reduces the heart rate.
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what detects environmental factors that causes a change in heart rate, what happens once the change in environment is detected
sensory receptors, input is then sent to the cardiovascular center (in the medulla oblongata). the cardiovascular center coordinates the output to the SAN
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heart: sensory input to the cardiovascular center:
what happens when stretch receptors in the muscles detect movement of the limbs
steretch repectors send impulses to the cardiovascular centre, informing it that extra oxygen may soon be needed. This leads to an increse in heart rate
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3heart: sensory input to the cardiovascular center includes chemoreceptors ; what do they do and where are they located.
they are in the carotid arteries, the aorta and the brain. Thye monitor the pH of blood. The change in pH is detected by the chemoreceptors, which will send action potentials to the cardiovascular center. this will tend to increase the heart rate.
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how does the conc of CO2 act as sensory input (what happens when conc of CO2 decreases)
when we stop exercising, the conc. of co2 in the blood falls, this reduces the activity of the accelerator pathway. thus, heart rate declines
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how does stretch receptors acts as a sensory input
stretch receptors are in the walls of the carotid sinus (a small swelling in the carotid artery), they monitor blood pressure. when there is an increase in blood pressure e.g., by exercise, it will be detected by these stretch receptors. if the pressure rises too high, the stretch receptors will send action potentials to the cardiovascular center, leading to a reduction in heart rate.
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what must be fitted if the mechanism controlling the heart rate fails
an artificial pacemaker
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where is the artificial pacemaker implanted and what does it do
implanted under the skin and fat on the chest ( or sometimes within the chest cavity itself), it may be connected to the SAN or directly to the ventricle muscle.
-it delivers an electrical impulse to heart muscle
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whats cardiac muscle
muscle found in the heart walls
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whats involuntary muscle
smooth muscle that contracts without conscious control
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whats a neuromuscular junction
the structure at which the nerve meets the muscle, its similar in action to a synapse.
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whast skeletal (striated) muscle
muscle under voluntary control
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what are muscles composed of
composed of cells arranged to form fibers
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what can muscle fibers generally do
can contract to become shorter which produces a force
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how is contraction of muscle achieved
achieved by the interaction between two protein filaments (actin and myosin) in the muscle cells.
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what can muscle not operate without
can't operate without an antagonist (works against each other in opposite pairs)
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how are muscles usually arranged
usually arranged in opposing pairs, so that one contracts as the other elongates.
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what may the antagonist be for muscles
elastic recoil or hydrostatic pressure in the chamber
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what are the 3 types of muscle
- involuntary (smooth) muscle
- cardiac muscle
- voluntary (skeletal or striated) muscle
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describe involuntary (smooth) muscle
-consists of individual cells tapered at both ends (spindle shaped)
-at rest each cell is about 500um long and 5um wide
-each cell contains a nucleus and bundles of actin and myosin
-non striated
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what two layers does smooth muscle contain
- a circular layer of smooth muscle
-a longitudinal layer of smooth muscle
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describe the circular layer of smooth muscle in smooth muscle in the gut wall
it runs around the intestine and its contraction causes segmentation
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describe the longitudinal layer of smooth muscle in smooth muscle in the gut wall
it runs along the intestine and causes wave like contractions
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talk abt the actions of the smooth muscle in the gut and what its controlled by
it contracts slowly and regularly, it does not tire quickly.
its controlled by the autonomic (self governing )nervous system
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where is involuntary smooth muscle found
found in the walls of tubular structures such as the digestive system and blood vessels
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how is involuntary smooth muscle arranged
usually arranged in longitudinal and circular layers
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what does cardiac muscle form
forms the muscular part of the heart
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describe the structure of cardiac muscle and what this allows for
individual cells form long fibres. These cross bridges help to ensure that electrical stimulation spreads evenly over the walls of the chambers. when muscle contracts, this arrangement also ensures that the contraction is a squeezing action rather than one dimensional.
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what are the cells in cardiac muscle joined by
joined by intercalated discs
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what are intercalated discs in cardiac muscle*
specialised cell surface membranes fused to produce gap junctions that allow free diffusion of ions between the cells
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what can pass easily and quickly along cardiac muscle fibres
action potentials
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talk abt the actions of the cardiac muscle
cardiac muscle contracts and relaxed continuously throughout the day. It can contract powerfully and does not fatigue easily.
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can purkinje fibres carry electrical impuses
yes, if muscle fibres are modified
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what is the rate of contraction controlled by in the heart
the SAN
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how does cardiac muscle appear when viewed under a microscope
appears striated (striped)
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where is skeletal muscle located
at the joints in the skeleton
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how does contraction cause movement of the skeleton
by bending or straightening the joint
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muscles are arranged in pairs, what are these pairs called?
antagonistic pairs, when one contracts, the other elongates
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what is the diameter of the fibres that muscle cells form
100 um
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skeletal muscle: muscle cells form fibers, describe these fibers:
each fiber is multinucleate (contains many nuclei) and surrounded by a membrane called the sarcolemma.
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what is the muscle cell cytoplasm called
sarcoplasm
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how is the sarcoplasm specialized
its specialized to contain many mitochondria and an extensive sarcoplasmic reticulum (specialized endoplasmic reticulum)
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muscle cells form fibers, what are these fibers arranged into
arranged into a number of myofibrils, which are contractile elements.
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what are myofibrils divided into
divided into a chain of subunits called sarcomeres
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what 2 protein filaments do sarcomeres contain
-actin
-myosin
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actin and myosin are arranged in a particular banded pattern, how does this affect how the muscle looks
gives the muscle a striped or stirated apperance
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what are dark bands of the muscle called
A bands
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what are lighter bands of the muscle called
I bands
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label the skeletal muscle
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voluntary muscle contracts quickly and powerfully, what does it also mean due to this
that it also fatigues quickly
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what type of control is skeletal muscle under
voluntary control
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state the six steps for stimulation of contraction at the neuromuscular junction
1- Action potentials arriving at the end of the axon open calcium ion channels in the membrane. Calcium ions flood into the end of the axon.
2- vesicles of acetylcholine move towards and fuse with the end membrane
3- acetylcholine molecules diffuse across the gap and fuse with the receptors in the sarcolemma
4- This opens sodium ion channels, which allow sodium ion channels to enter the muscle fibre, causing depolarisation of the sarcolemma
5- a wave of depolarisation spreads along the sarcolemma and down the transverse tubules into the muscle fibre.
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what do SOME motor neurones stimulate while what do MANY motor neurones divide and connect to
-some motor neurones stimulate single muscle fibres
-however many motor neurones divide and connect to several muscle fibres.
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whats a motor unit
when many muscle fibres contract together, providing a stronger contraction
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what are myofibrils and what do they contain
-myofibrils are contractile units of skeletal muscle and contain two types of protein filament.
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myofibrils contain two types of protein filament, state these
-contains thin filaments (actin), which are aligned to make up the light band; these are held together by the Z line.
-thick filaments (myosin), which make up the dark bands.
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do thick and thin filaments overlap ( in myofibrils)
yes however in the middle of the dark band (thick filaments) there is no overlap
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what is the H zone
where no thick and thin filaments overlap ( this is in the middle of the dark band)
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what is the sarcomere
the distance between two Z lines, its the functional unit of the muscle
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at rest, how long is the sarcomere
2.5um long
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what surrounds thick and thin filaments
surrounded by sarcoplasmic reticulum
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*what are the thin filaments made of
actin
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what does each thin filament consist of
consists of two chains of actin subunits twisted around each other
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thin filaments: what is wound around each actin
wound around each actin is a molecule of tropomyosin to which are attached globular molecules of troponin.
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thin filaments: what does each troponin complex consist of
each troponin complex consists of three polypeptides: one binds to actin , one to tropomyosin and the third binds to calcium when its available
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what mechanism is tropomyosin and troponin part of
are part of the mechanism to control muscular contraction.
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*at rest, what do the molecules of tropomyosin and troponin do
they cover binding sites to which thick filaments can bind
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what does each thick filament consist of
consists of a bundle of myosin molecules
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thick filaments: what does each myosin molecule have
-each myosin molecule has 2 protruding heads
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thick filaments: describe the heads of the myosin molecule and what they can do
these heads are mobile and can bind to actin when binding sites are exposed when tropomyosin has been moved.
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what happens to the light band and the H zone during contraction
they both get shorter during contraction
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sliding filament hypothesis: during contraction, the light band and the H zone gets shorter, what does then happens to the Z lines and the sarcomere
the Z lines move closer together and the sarcomere gets shorter
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the mechanism of contraction: what is the sliding action caused by
the sliding action is caused by the movement of myosin heads
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from the stimulation in muscle for the mechanism of contraction, describe the sequence of events leading to actin sliding past myosin
When the muscle is stimulated, the tropomyosin is moved aside, exposing the binding sites on the actin. The myosin heads attach to the actin and move causing the actin to slide past the myosin
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lable the filaments sliding past one another during contraction
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what are the 6 steps in control of contraction
1. When the muscle is stimulated, the action potential passes along the sarcolemma and down the transverse tubules (t-tubules) into the muscle fibre
2. The action potential is carried to the sarcoplasmic reticulum, which stores calcium ions, and causes the release of calcium ions into the sarcoplasm.
3. The calcium ions bind to the troponin, which alters the shape pulling the troponin, which alters the shape pulling the tropomyosin aside
4. Myosin heads bind to the actin, forming cross-bridges between the filaments.
5. they myosin heads move, pulling the actin filaments past the myosin filament.
6. The myosin heads detach from actin and can bind again further up the actin filament
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control of contraction: what can be formed between actin and myosin filaments
millions of cross bridges are formed between the actin and myosin filaments
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control of contraction: what allows the muscle to relax
once contraction has occurred, the calcium ions are rapidly pumped back into the sarcoplasmic reticulum, allowing the muscle to relax
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what is the role of ATP in muscle contraction
ATP supplies the energy for contraction
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part of the myosin head can act as ATPase***, what does this mean it can do
part of the myosin head can act as ATPase, it cn hydrolyse ATP to ADP and inorganic phosphate (Pi) releasing energy
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describe the role of ATP in muscle contraction
1. The myosin head attaches to the actin filament, forming a cross bridge
2. The myosin head moves (tilts backwards), causing the thin filament to slide past the myosin filament This is the power stroke. During the power stroke, ADP and Pi are released from the myosin head.
3. After the power stroke, a new ATP molecule attaches to the myosin head, breaking the cross bridge.
4. The myosin head then returns to its original position (swings forwards again) as the ATP is hydrolysed, releasing the energy to make this movement occur. The myosin head can now make a new cross bridge further along the actin filament.
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why must ATP be regenerated very quickly in muscles
because the ATP available in muscles is only enough to support 1-2 seconds worth of contraction.
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what are the 3 mechanisms involved in maintaining the supply of ATP
-aerobic respiration in mitochondria
-anaerobic respiration in the sarcoplasm of the muscle tissue
-creatine phosphate
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How does Aerobic respiration in mitochondria produce ATP?
-muscle tissue contains a large number of mitochondria in which aerobic respiration can occur
-the bhor effect helps release more oxygen from haemoglobin in the blood
-however, during intense activity, the rate at which ATP can be produced will be limited by the delivery of oxygen to the muscle tissue
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How does anaerobic respiration in the sarcoplasm of the muscle tissue produce ATP?
-Anaerobic respiration can release a little more ATP from the respiratory substrates. However it leads to the 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
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How does Creatine Phosphate produce ATP?
creatine phosphate in the sarcoplasm acts as a reverse store of phosphate groups. The phosphate can be transferred from creatine phosphate to ADP molecules, creating ATP molecules very rapidly. the enzyme creatinine phosphotransferase is involved. The supply of creatine phosphate is sufficient to support muscular contraction for a further 2-4 seconds.
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Describe the role of ATP during muscle contraction?
ATP joins the myosin head as it detaches from the actin.
The ATP is hydrolysed to ADP and Pi releasing energy, which causes the myosin head to swing back to its starting position.
When the myosin binding site is exposed the myosin can bind to the actin and move causing the actin filament to slide.
As the filament slides the ADP and Pi are released.
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How is ATP used while the muscle is at rest?
ATP is hydrolysed to release energy for active transport - this transports calcium ions into the sarcoplasmic reticulum by pumping them back into the sarcoplasmic reticulum, allowing the muscle to relax.
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A few hours after death, the muscles contract in rigor mortis (stiffening of muscles). Suggest why this happens?
When the ATP runs out the calcium ions start to leak out of the sarcoplasmic reticulum. The calcium binds to the troponin and exposes the myosin binding sites on the actin. The myosin binds and causes the filaments to slide - contraction of the muscle. However, there is no ATP left to release the myosin from the actin so the muscle remains contracted.
