5.5 Plant and animal responses Flashcards
1
Q
What are abiotic components?
A
compenents of an ecosystem that are non-living.
2
Q
What are alkaloids?
A
Organic nitrogen-containing bases that have important phyiological effects on animals; includes nicotine, quinine, strychnine and morphine.
3
Q
What are biotic components?
A
Components of an ecosystem that are living.
4
Q
What are pheromones?
A
Any chemical substance released by one living organism, which influences the behaviour or physiology of another living thing.
5
Q
What are tannins?
A
Phenolic compounds, located in cell vacuoles or in the surface wax on plants.
6
Q
What is tropism?
A
A directiona; growth responce in which the direction of the responce is determined by the direction of the external stimulus.
7
Q
How may a plant respond to higher temperatures?
A
They may deposit a thicker layer of wax on their leaves.
8
Q
How may a plant respond to very windy conditions?
A
They may have a more heavily lignified vasular tissue.
9
Q
How may a plant respond to the threat of hervibours? (chemical defences)
A
- Tannins
- Alkaloids
- Pheromones
10
Q
How are tannins a responce to the threat of herbivores to a plant?
A
Tannins are toxic to microoganisms 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 microogranisms.
11
Q
How are Alkaloids a responce to the threat of herbivores to a plant?
A
Alkaloids are derived from amino acids. In plants, scientists think they are a feeding deterrent to animals, tasting bitter. They are located in the growing tips and flowers, and periperal cell layers of stems and roots.
12
Q
How are Pheromones a responce to the threat of herbivores to a plant?
A
Pheromones are chemicals which are released by ome individual and which can affect the behaviour or physiology of another.
13
Q
What sort of response are tropisms?
A
Tropisms are directional responces of plants?
14
Q
Whar are some examples of tropisms?
A
- Phototropism
- Geotropism
- Chemotropism
- Thigmotroptism
15
Q
What is phototropism?
A
Type of tropism where shoots grow towards light, which enable them the photosynthesis. They are positivly phototrophic.
16
Q
What is geotropism?
A
Form of tropism- roots grow towards the pull of gravity. This anchors them in the soil and helps them take up water. There will also be minerals into water, such as nitrates needed for the synthesis of amino acids.
17
Q
What is chotropism?
A
Type of tropism- On a flower, pollen tubes grow down the style, attracted by chemicals, towards the ovary where fertilisation can take place.
18
Q
What is thigmotropism?
A
Shoots of climbing plants, such as ivy, wind around other plants or solid structures to gain support.
19
Q
What is it called when a plant responds towards a stimulus?
A
It’s a positive tropic response.
20
Q
What is it called when a plant respomds away from a stimulus?
A
It’s a negative tropic responce.
21
Q
What are nastic respoces?
A
Non-directional responces to external stimuli.
22
Q
What is an example of nastic responces to a stimulus?
A
Thigmonasty- the nastic response of a plant to touch or vibration. e.g. mimosa plantsresponds to touch by folding it’s leaves
23
Q
What coorfinates plant responces to enviromentak stimuli?
A
Plant hormones
24
Q
Describe plant hormones.
A
Plant hormones are chemical messangers that can be transported awat from the site of manufacture to act in other parts of the plant. They are not produced in endocrine gands, but in a variety of tissues in the plant. When hormones reach their target cells, they bind to receptors on the plama membrane. Specific hormones are specific shapes, which can only bind to specific receptors with complementary shapes on the membranes of particular cells. This specific binding ensures that hormones act on the right cells.
25
What are some effects of plant hormones?
* Amplify each others side effects.
* Cancel out each other side effects.
* Induce cell division, cell enlongation or cell diffrentiation.
26
What are 5 examples of plant hormones?
* Cytokinins
* Abscisic acid
* Auxins
* Gibberellins
* Ethene
27
What do cytokinins do?
* Promote cell divion
* Delay leaf senescence
* Overcome apical dominance
* Promote cell expansion
28
What does abscisic acid do?
* Inhibits seed germination and growth
* Causes stomatal closure when the plant is stressed by low water availability
29
What do Auxins do?
* Promote cell elongation
* Inhibits growth of side shoots
* Inhibits leaf abscission (leaf fall)
30
What do Gibberillins do?
* Promote seed germination and growth of stems
31
What does Ethene do?
Promotes fruit ripening.
32
How do hormones move around a plant?
* Active transport
* Diffusion
* Mass flow in the phleom sap or in xylem vessels.
33
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.
34
What are auxins?
Plamts hormones which are responsible for regulating plant growth.
35
What are gibberellins?
Plant hormones which are responsible for the control of stem elongation and seed germination.
36
What will happen to a plants side shoots, if you break the shoot tip (apex) off a plant?
The plant side shoots start to grow from lateral buds which were previously dormant.
37
Which plant hormone prevents lateral buds growing?
Auxins from the apical bud prevent lateral buds growing.
38
What happens to auxin levels in a plant when a plants shoot tip is removed?
Axins levels drop, causing buds to grow.
39
How did scientists test their hypothesis that lower levels of auxins caused side shoots to grow?
Scientist applied a paste containing auxins to the cut end of the shoots, and the lateral buds did not grow.
40
Why did the scientists testing the effect on auxins have to change their original experiment?
The scientists showed if they put a paste containing auxins on the cut shoot, the buds didnt grow. However, this could have been an unexpected effect upron the exposure to oxygen as the cells could have produced a different hormone.
To overcome this, scientists put a ring of auxin transport inhibitor below the apex of the shoot- the lateral buds grew.
41
Later on, a different scientist suggested 2 hormones are involved in auxin levels and growth inhibition?
* Absisic acid inhibits bud growth. High auxin in the shoot may keep absisic levels high in the bud. When the tip is removed, absisic acid levels drop and the buds start to grow.
* Cytokinins promote bud growth- directly applying cytokinin to buds can override the apical dominance effect. High levels of auxins make the soot apex a sink for cytokinins produced in the roots- most of the cytokinins goes to the shoot apex- when the apex is removed, the cytokinins spread out evenly through the plant.
42
In Japan, a fungus causes a disease whch makes rice grow very tall. What compound must be in the fungus?
The fungal compounds involoved are gibberellins and include gibberellic acid (GA3).
43
What happens to a plant when gibberellic acid is tested on it?
It will grow taller.
44
What is gibberellic acid responsible for?
Stem growth
45
In an experiment investigating the effects of gibberellic acid (GA3), what must happen?
* Must be tested within concentrations of gibberellins normally found in plants.
* Must be tested in parts of the pplant gibberellins normally reach.
46
What hormone promotes seed germination?
Gibberellins
47
How do gibberellins promote seed germination?
When the seed abosrbs water, the **embryo releases gibberellin, which travels to the aleurone layer in the endosperm reigion of the seed. The gibberellin enebles the production of amalase** which can break down strach into glucose. This provides a substate for respiration for the embryo, as it grows. The glusoce is also used in protein sythesis.
48
What is geotropism?
A directional responce to gravity.
49
What is phototropism?
A directional growth responce to light.
50
Where does growth happen in plants?
In places where in the plant there are immature cells that are still capable of dividing, called merristems.
51
Where can meristems be found in plants?
* **Apical meristems** are at the tips of roots or shoots, and are responisble for the roots and shoots getting longer.
* **Lateral bud meristems** are found in the buds. They can give rise to side shoots.
* **Lateral meristems** forming a cyclinder near the outside of the roots and shoots are are responsible for the roots and shoots getting wider.
* In some plants, **intercalary meristems** are located between nodes, where the leaves and buds branch off the stem. Growth between the nodes is responsible for the shoots getting longer.
52
How can you investigate phototropic responces?
Phototropic responces can be investigated using an experimental plant and a control plats (with 10 replicates). The control plant is illuminated from all side, which the experimental plant has illumination just from one side. In each plant, the shoots and roots are marked enery 2mm at the start.
Look at the results after several days. The shoot that has bent towards the light, because the shady side of the shoot has elongated more than the illuminated side. The mean and standard devistion of the lengths between the marks has in creased on the shady side.
53
What experiement confirmed that a chemical messenger from the shoot tip is responsible for the phototropic responses?
Darwin did an experiment with blades of grass changing whats happening to to the tip of the plant and observing the plants responce.
54
What did Boysen-Jenson's work tell us about phototropism? What did he do?
He confirmed that water and/or solutes need to be able to move back anf forwards from the shoot for the tip for phototropism to occur.
When a permeable genaletine block was inserted behind the shoot tip, the shoot still showed positive phototropism but when an impermeable mica block was inserted, there was no phototropic responce.
55
What was done in the classic experiment to confirm the role of the shoot tip in producing a chemical messanger that controls phototropic responces?
With blades of grass, differrent situations are set up:
* Control
* Agar-block containing auxin stimulates growth.
* Offset blocks containing auxin simulated curved growth.
* Blocks containing no auxin have no effect.
56
What results do giving blocks of agar with different concentrations of auxin give to a plant?
Give the same result.
57
Where is auxin when there is light equal on all sides of a plant? What does this cause?
Axin promotes shoot growth evenly- making the shoot grow staight up.
58
Where is auxin when light is on one side of a plant? What does this cause?
Causes auxins to be transported to the shady side, causing the cells to elongate more quickly, making the shoot bend towards the light.
59
What is the extent a plant cell elongates is proportional to?
The concentration of auxins.
60
What is a role of auxin in the cell walls?
Auxin increases the strechiness of the cell wall promoting the active transport of H+ by an ARPase enzyme on the plasma membrane into the cell will. The resulting low pH provides optiumum conditions for wall-loosening enzymes (expansins) to work.
61
How do the enzymes expansisns work?
These enzymes break binds within the cellulose so the walls bbecome less rigid and can expand as the cell takes in water.
62
How does auxin let the cell elongate?
Auxins increases wall stretchyness, promoting the active transport of H+ by ATPase enzymes on the plasma membrane. A low pH is optiumum for expansisn (wall-loosening enzymes) which break down the binds in cellulose. Also, the increased hydrogen ions disrupt hydrogen boonds in the cellulose- soio walls are less rigid- cells can expand when they take in water.
63
How is auxin involoved in the geotropic responces in the roots?
If a root is lying flat, auzin accumulates on the lower side, where it inhibites cell elongation. The upperside continues to groe and the root bends downwards.
64
What does the graph look like showing the efffect of auzin concentration on eleongation of shoots and roots compared to controls?
65
What is the automonic nervous system?
Part of th nervous system responsible for controlling the involuntary motor activities of the body.
66
What is thr central nervous system?
The central part of the nervous system composed of the brain and the spinal cord.
67
What is the peripheral nervous system (PNS)?
The sensory and motor nerves connecting the sensory receptors and effectors to the CNS.
68
What is the somatic nervous system?
The motor neurones uner concious control.
69
What is the role of the nervous system?
To provide responces, such as:
* Coordinating muscle action
* Control of balance and posture
* temperature regulation
* Coordination with the endocrine system
70
What 2 categories is the overall nervous split into?
* Central nervous system
* Peripherial nervous system
71
What is the PNS split into?
* Sensory system
* Motor system
72
What is the motor system split in to in the nervous system?
* Somatic nervous system
* Autonomic nervous system
73
What is the autonomic nervous system split into in the nervous system?
* Sympathic system
* Parasympathetic system
74
What is the organisation of the nervous system?
75
What does the CNS consist of?
The brain and the spinal cord.
76
How many neurones does the brain contain?
86 billion neurones
77
What does a lot of the brain consist of? Decribe these?
Much of the brain is composed of replay neurones, which have **multiple connections** eneabing complex neural pathways. Most of these cells are **non-mylinated** cells and there tissues look grey in colour- it's called **grey matter**.
78
What is similar in what the brain the the spinal cord is made up of?
Both contain non-mylinated neurones making up grey matter.
79
What does the spinal cord contain that thr brain doesn't? What is it's function?
The spinal cord contains large numbers of mylinated neurones making up an outer region of white matter. These mylinated neurones carry action potentials up and down the spinal cord for rapid communication over long distances.
80
What is the spinal cord protected by?
The vertebral column- between each vertebrea, peripheral nerves enter and leave the spinal cord carrying action potentials from the rest of the body.
81
What is the role of the peripheral nervous system?
To ensure rapid communication between the senesory receptors, the CNS and the effectors.
82
What is the PNS composed of?
Composed of sensory and motor neurones. These are usuallly bundled together in a connective tissue sheath of form nerves.
83
Which bit od the sensory neurones enter the CNS?
The sensory fibres entering the CNS are dendrons of the sensory neurones.
84
On a sensory neurone, where is the cell body on the neurone in the nervous system?
These neurones have their cell body in the dorsal root leading into the spinal cord and a short axon connecting to other neurones in the CNS.
85
What does the motor nervous system do?
The motor nervous syetm conducts action potentials from the CNS to the effectors.
86
What are some comnercial uses of auxins?
* Taking cuttings
* Seedless fruit
* Herbicides
87
Why are auxins used to take cuttings comercially?
Dipping the end of a cutting in rooting powder before planting it encourages root growth. Rooting power contains auxins and talcum powder.
88
Why are auxins used to make seedless frits comercially?
Treating unpollinated flowers with auxin can promote growth of seedless fruit (parthenocarpy). Applying auxin promotes ovule growth, which triggers automatic production of auxin in tissues in the developing fruit, helping the complete the develpmental process.
89
Why are auxins used commercially to make herbicides?
Auxins are used as herbicides to kill weeds. Because they are man made, plants find them more difficult to break down, and they can act within the plants for longer. They promote shoot growth so much that the stem cannot support itself, buckles and dies.
90
Commercially what plant hormone is used to stop lettuce leaves going yellow after they have been picked?
Cytokinins bacuse they delay leaf senscence.
91
What are cytokinins used for commercially?
* Used to help mass-produce plants.
* They promotes bud and shoot growth from small pieces of tissue taken from a parent plant- this produces a short shoot with a lot of side branches, which can be split in to lots all small plants to be grown separetly.
92
How are gibberellins used in commercial fruit production?
* Gibberellins **delay leaf senescence in citrus fruit**, extending the time the fruit can be pickeds, and making them available to the shops for longer.
* Gibberellins acting with **cytokinins** can **make apples elongate** to improve their shape.
* Without gibberellins, bunches of grapes are very compact; this restricts the growth of individual grapes. With gibberllins the **stalk enlogates** so the **grapes get bigger**.
93
How are gibberellins used for commercial brewing?
To make beer, you need malt- when barley seeds germinate, the aleurone layer of the seed produced amylase, enzymes break down the stroed starch into maltose. Usually the gebes for amylase production is switched on for naturally occuring gibberellins. **Adding gibberllins speeds up the process**- malt is then produced by grying and grinding up the seeds.
94
How are gibberellins used for comercial plant breeding?
* Gibberellins can spped up artificial selection by inducing seed formation on young trees.
95
How can gibberellin synthesis inhibitors be useful in comercial plant breeding?
Gibberellin synthesis inhibitors can **keeps flowers short and stocky and ensures that the internodes of crop stay short**, helping prevent lodging. (this happens in wet summers- stes bend over because of the weight collected on the ripened seed heads, making crop difficult to harvest.
96
How can ethene be sprayed on a plant?
Ethene is a gas so scientists have developed **2-chloroethylphosphonic acid**, which can be prayed in solution, is easily absorbed, is slowly absorbed, and slowly releases ethene inside the plant.
97
What is ethene used for commercially?
* Speeding up fruit-ripening.
* Promoting fruit drop in cotton and cherry
* Promoting female sex expression in cucumbers, reducing the chance of self fertilisation.
* Promoting lateral growth in some plats, yeilding compact flowering stems.
98
How can restricing ethenes effect be useful?
Storing fruit at a low temperature, with little oxygen and high carbon dioxide levels, means fruits can be stored for longer.
Can also increase self life of cut flowers.
99
What does the motor nervous system do?
Conducts action potentials from the CNS to the effectors.
100
What is the motor nervous system further subdivided into?
* The somatic nervous system
* The autonomic nervous system
101
Whatv is the somatic nervous system?
The somatic nervous system consists of motor neurones that conduct action potentials from the CNS to the effector that are **under volentary control**. These neurones are mostly **mylinated** so reponce is rapid. There is **always one single neurone connecting the CNS to the effector**.
102
What is the autonomic nervous system?
Consists of motor meurnes that conduct action potentials from the CNS to effectors that are **not under volentary control**. Many neurones are **non-mylinated** as responces don't have to be rapid. There are **at least 2 neurones involved in the connection between CNS and the effector**. These neurones are connected at small swellings called **gangia**.
103
What is the connection called between neurones going from the CNS to an effector in the autonomic nervous system?
Ganglia.
104
What are some examples of the autonomic nervous system?
* Glands
* The cardiac muscle
* Smooth muscle in the walls of blood vessles
* The air way
* The wall of the digestive system
105
What is the autonomic nervous system responsible for controlling?
Responsible for controlling the majority of homeostatic mechanisms and so plays a vital role in regulating the internal enviroment of the body.
106
What is the autonomic nervous system further subdivided into?
The autonomic nervous system can be divided up in to the **sympathic system and and parasympathic system**.
107
What doers the sympathic system do?
Prepares the body for action.
108
What does the parasympathic system do?
Conserves energy.
109
Why is the sympathic system and the parasympathic system antagonistic?
The action of one system opposes the other.
110
At rest, what is happening between the sympathetic and parasympathetic systems in the body?
At rest, action potentials pass along the neurones of both systems at a relatively low frequency- this is controlled subconsciously by the brain.
111
What leads to changes in the balence of the sympathetic and parasympathetic systems?
Changes in the intenal condiations, or stress.
112
What are the nerves between the CNS and an effector like in the sympathetic system?
It consists of many nerves leading out of the CNS, each leading to a different effector.
113
What are the nerves between the CNS and an effector like in the parasympathetic system?
It consists of few nerves leading out of the CNS, which divide up and lead to different effectors.
114
Where is the ganglia in the sympathetic system?
Just outside the CNS.
115
Where is the ganglia in the parasympathetic system?
Ganglia is in the effector tissue.
116
What are the pre-ganglionic neurones like in the sympathetic system?
Short pre-ganglionic neurones.
117
What are the pre-ganglionic neurones like in the parasympathetic system?
Long pre-ganglionic neurones. (variable in length dependent upro the position of the effector)
118
What is the neurotransmitter in the sympathic system?
Noradrenaline
119
What is the neurotransmitter in the parasympathic system?
Acetylcholine
120
How does the sympathetic system change the activity in the body?
Increases the activity- prepares the body for activity.
121
How does the parasympathetic system change the activity in the body?
Decreases activity- conserving energy.
122
When is the sympathetic system most active?
In times of stress
123
When is the parasympathetic system most active?
During sleep or relaxation
124
What are the effects of the sympathetic system?
* Increases heart rate
* Dialates pupils
* Increases ventillation rate
* Reduces digestive activity
* Orgasm
125
What are the effects of the parasympathetic system?
* Decreases heart rate
* Constricts pupils
* Reduces ventillation rate
* Increases digestive activity
* Sexual arousal.
126
What is cardiac muscle?
Muscle found in the walls of the heart.
127
What is involentary muscle?
Smooth muscle that contracts without conscious control.
128
What is a neurotransmitter junction?
The structure at which a nerve meets the muscle; its similaar in action to a synapse.
129
What is skeletal muscle?
Also known as **stirated** muscle, it's muscle under volentary control.
130
What are muscles conposed of? What does this acheive?
Muscles are conposed of cells aranged to form fibres. These fibres become shorted, which produces a force.
131
How does contraction occur in a muscle?
Contraction in achieved by interaction between 2 protein filaments (**actin and myosin**) in the muscle cells.
132
What must muscles have to elongate?
Muscle cannot elongate without an antagonist.
133
How are muscle arranged which allows them to elongate?
Muscles are arranged in opposing pairs, so that one contracts as the other elongates. The opposing muscle is the **antogonist.**
In some cases, the antagonist may be elastic reciol or hydroststic pressure in a chamber.
134
What are the 3 different types of muscle?
* Involentary (smooth) muscle
* Cardiac muscle
* Volentary (skeletal/ stirated) muscle
135
Describe the cells involentary (smooth) muscle is made up of?
It 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**.
136
Characteristically, how does involentart (smooth) muscle contact?
It contracts slowly and regularly.
137
Does involentary (smooth) muscle tire quickly?
No
138
What controls the involentary (smooth) muscle?
The autonomic nervous system.
139
Where is involentary muscle found?
Walls of tubular structure: digestive system and blood vessele.
140
How is involentary muscle arranged?
Arranged in longitudinal and circular layers that oppose each other.
141
What is this a diagram of?
Involentary (smooth) muscle.
142
Describe the structure of cardiac muscle?
The individual cells form fibers, which form **cross-bridges** between the fibres. These cross-bridges help to ensure that electrical stimulation spreads evenly over the walls of the chambers. The cells are joined by **intercalated disks**.
143
Why does cardiac muscle have cross-bridges?
So when the muscle contracts, there is a squezzing action rather than a one-dimentional contraction.
144
Muscle cells are joined be intercalated discs, what are these?
These are specialised cell surface membranes fused to **produce a gap junction** that allows the free diffusion on ions between cells, so action protentials pass easily and quickly along cardiac muscle fibe=res.
145
Characteristically, what is the contractions like in cardiac muscle?
It contracts and relaxes continously throughout life. It is **myogenic**- so can initiate its own contaction bu the rate of contraction is controlled by the **SAN**.
146
Does cardiac muscle fatigue easily?
It can contract powerfully and does not fatigue easily.
147
What coordinates the contractions in cardiac muscle?
Muscle fibres (**Purkyne fibres**) are modified to carry electric impulses- they coordinate contraction of the chamber walls.
148
What is this a diagram of?
Cardiac muscle
149
Where acn you find skeletal muscle?
At the joins in the skeleton.
150
What does contraction of the skeletal muscle causes?
Contraction causes movement of the skeleton by bending or straightening the joint.
151
What is it called when muscles are arranged in pairs?
Antagonistic pairs.
152
In an antogonistic muscle pair, what happens to the other muscle when one contracts?
The other muscle will relax.
153
What is the structure of volentary (skeletal) muscle?
The muscle cells form fibres of about **100um** in diameter. Each fiber is **multinucleate** and is surrounded by a membrane called the **sarcolemma.** It has cytoplasm called **sarcoplasm** which contains many **mitochondria** and an extensive **sarcoplasmic rectiilum**.
154
What is the skeletal muscle fibre membrane called?
The sarcolemma.
155
What is the cytoplasm of skeletal muscle called?
The sarcoplasm.
156
What are the spacialised endoplasmic rectilium called my skeletal muscle fibres?
The sarcoplasmic rectilium.
157
What are the contents of volentary muscle fibres arranged into?
They are arranged into **myofibrils,** which are contractile elements. Myofibrils are divided into a chain of subunits called **sarcomeres** which contain actin and myosin.
158
What are sacrcomeres and what do they contain?
They are a chain of subunits in the myofibrils in volentary muscle fibres- they contain the protein filaments actin and myosin.
159
How is actin and myosin arranged in skeletal muscles?
Actin and myosin is arranged in a particular banded pattern, which gives the muscle a striped or stirated appearence.
160
Why do volentary muscles appear to have a striped pattern, what are these called?
Actin and mysin is arranged in a banded parttern, which gives the stiped appearence. The dark bands are called A bands and the lighter bamds are the I bands.
161
Whta is this a diagram of?
Volentary (skeletal) muscle
162
Does volentary muscle fatigue quickly?
Yes
163
Characteristically, how does a volentary muscle contract?
Volentary muscle contracts quickly and powerfully.
164
What are skeletal muscles stimulated by?
They are stimulated by the somatic nervous system.
165
What is the junction and the muscle called?
A neuromuscular junction.
166
What is the process of stimulating a contraction?
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. Vescicles of acetocholine move towards and fuse with the end of the membrane.
3. Acetoylcholine molecules diffuse across the gap and fuse with the receptors in the saecolema.
4. This opens sodium ion channels, which allows sodium ions to enter the muscle fibre, causing depolarisation of the sarcolemma.
5. A wave of depolarisation spreads along the sarcolemma and down a transverse tubules into the muscle fibres.
167
What is happening at this point in a neuromuscluar junction when stimulating a contraction?
Action potentials arriving at the end of the axon open calcium ion channels allowing calcium ions to flood into the axon tip.
168
What is happening at this point in a neuromuscluar junction when stimulating a contraction?
Vesicles of acheltocholine move towards the membrane and fuse.
169
What is happening at this point in a neuromuscluar junction when stimulating a contraction?
Acetocholine molecules diffuse across the gap and bind to receptors.
170
What is happening at this point in a neuromuscluar junction when stimulating a contraction?
Sodium ion channels open and sodium ions enter the muscle fibre causing depolarisation.
171
What is happening at this point in a neuromuscluar junction when stimulating a contraction?
Wave of depolarisation passes along the sarcolemma and down the transverse tubules.
172
What is a motor unit?
Some motor neurones stimulate single muscle fibres. However, many more neurone divide and connect to several muscle fibres. All these **muscle fibres contract togther, providing a stringer contraction**.
173
What equiptment can be used to investigate muscle stimulation?
An elecromygraph (EMG).
174
How is an elecromygraph used to investigate muscle stimulation?
Electrodes applied to the surface of the skin detect the combined effects of these action pontentials. The amplitude of the EMG recording reflects the number and the size of the motor neurine involved in the contrsction.
175
In an EMG, what does a more powerful contraction shown as?
A higher amplitude.
176
What is the recorded trace of an EMG called?
An eletromygram.
177
What is this a picture of?
An electromygram.
178
What are the main 4 parts of the brain?
* The cerebrum
* The cerebellum
* The hypothalamus and pituitary complex
* Medulla oblongata
179
What is the cerebrum?
The largest part of the brain and organises most of our though processes, such as conscious thought and memory.
180
What is the cerebelllum?
Part of the brain that coordinated movement and balence.
181
What is the hypothalamus and the pituitary complex?
Part of the brain which organised homeostatic responces and controls various physiological processes.
182
What is the medulla oblongata?
Part of the brain that coordinates many of the autonomic responces.
183
What does the cerebrum consist of?
It has **2 hemispheres**, which are connected via major tracts of neurones called the **corpus callosum**. The outermost layer of the cerebrum consists of a thin layer of nerve, celll bodies called the **cerebral cortex**.
184
What does the cerebrum control?
It controls the 'hight brain' functions including:
* Conscious thought
* Conscious actions (including the ability to override some reflexes)
* Emotional responces
* Intellegence, reasoning, judgement, decision making
* Factual memory
185
What is the cerebral cortex?
The outermost layer of cerebrum that consists of a thin layer of nerve cell bodies.
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what areas is the cerebral cortex subdivied up into?
* Sensory areas
* Association areas
* Motor areas
187
Describe the sensory areas of the cerebral cortex.
They recieve action potentials indirectly from sensory receptord. The** size of the reigion allocated** to recieve in put from different receptors are **related to the sensitivity of the area the input is from**.
188
Describe the function of the association areas of the cerebral cortex?
These areas c**ompare sensory inputs with previous experience**, interpret what the input means, and **judge an appropiate responce.**
189
Describe the motor areas of the cerebral cortex.
These areas **send action potentials to various effectors**. The **size** of the regions allocated to deal with different effectors are related to the complexitl of the movements needed by the part of the body. **Motor areas on the left side of the brain control the effectors on the right side of the body**.
190
Define cerebellum.
Region of the brain coordinating balence and fine control of movement.
191
Define cerebrum.
Region of the brain dealing with the higher functions such as conscious thought; it is divided into 2 cerebral hemispheres.
192
Define hypothalamus.
The part of the brain that coordinates homeostatic responses.
193
Define medulla oblongata.
Region of the brain that controls physiological processes.
194
Define pituitary galnd.
Endrocrine gland atv the base of the brain, below but attatched to the hypothalamus; the anterior lobe secretes many hormones; the proserior lobe stores and releases hormones made in the hypothalamus.
195
What does the cerebellum contain?
It contains over half of the neurones in the brain.
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What is the cerebellum involved with, why is it so important it has lots of nerves?
It is involved with balence and fine coordination of movement, to do this, it **must reveive information from many senory receptors** and process the information accuratley.
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Where does the sensory receptors that supple the cerebellum come from?
* The retina
* The balence organs in the inner ear
* The spindle fibres in the muscle
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Where is the conscious to contact the volentary muscles initiated?
In the cerebral cortex
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What sort of movements does the cerebral context coordinate?
The cerbral cortext does not provide complex signals requires to coordinate complex movemt.
200
What does the cerebellum coordinate?
Coordinated fine control of musclar movements, such as:
* Maintaining **body position and balence**
Judging the position of objects and limbs
* Tensioning muscles
* Coordinating contraction and relaxtaion of the antagonistic skeletal muscles
201
What does the cerebellum coordinate?
Coordinated fine control of musclar movements, such as:
* Maintaining **body position and balence**
Judging the position of objects and limbs
* **Tensioning** muscles
* **Coordinating** contraction and relaxtaion of the **antagonistic skeletal muscles**
202
What does the coordination from the cerebellum require?
The control often requires learning, but once learned, the activites will become second nature.
This sort of coordination requires complex nervous pathways.
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What happens to the complex nervous pathways in the cerebellum when control is practised?
The nervous pathways are strengthened and the activity become "programmed" into the cerebellum.
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Where does the action potnetials from the cerebellum go?
They travel to the motro area in the cerebrum so that the motor output to the effectors can be finely controlled.
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What is the cerebrum and the cerebellum connected by?
Connected by the pons.
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What does the hypothalamus control?
It controls the homeostatic mechanisms in the body.
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What does the hypothalamus contain too carry out its function?
It contains its own sensory receptors and acts by negative feedback to manitain a constant internal enviroment.
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What does the hypothalamus regulate?
Temperature regulation
Osmoregulation
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How does the hypothalamus regulate body temperature?
The hypothalamus detects changes in the core body temperature. It also receives sensory input from the receptors in the skin. It will initiate responses to temperature change that regulate body temperature in a narrow range. These responses may be mediated by the nervous system or by the hormonal system (pituitary gland).
210
How does the hypothalamus do osmoregulation?
It contains osmoreceptors that monitor the water potential in the blood. When the water potential changes, the osmoregulatory centre initiates responses that bring about a reversal of this change. The responses are mediated by the hormonal system via the pituitary gland.
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What is the structure of the pituitary gland?
It acts in conjunction with the hypothalamus. It consists of 2 lobes: the posterior lobe & anterior lobe.
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Describe the posterior lobe in the pituitary gland.
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 into the blood from the pituitary gland.
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Describe the anterior lobe of the pituitary gland.
It produces its own hormones, which are released into the blood to respond 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 the hormones released by the anterior pituitary gland control?
They control a number of physiological processes in the body, including responses to stress, growth, reproduction and lactation.
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What does the medulla oblongata control?
It controls the non-skeletal muscles (the cardiac and involuntary muscles).
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How does the medulla oblongata control the cardiac and involuntary muscles?
By sending action potentials out through the autonomic nervous system.
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What vital processes does the medulla oblogata control?
The cardiac cycle, regulating heart rate
The Vasomotor centre, regulating circulation and blood pressure
Respiratory centre, controlling rate and depth of breathing
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How do the centres for regulating vital processes in the medulla oblongata work?
The centres receive sensory information and coordinate vital functions by negative feedback.
219
Define the knee jerk reflex?
A reflex action that straighens the leg when the tendon below the knee cap is tapped.
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Define a reflex action.
A responce that does not involve any processing by the brain.
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What does relex actions not involve?
They do not involve any processing from the brain.
The brain may be informed the reflex has happened, but is not involved in coordinating the responce.
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What is the nervous pathway like for a reflex action?
The nervous pathway is as short as possible so that the reflex is rapid.
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What does the reflex pathway consist of?
Sensory neurone-> relay neurone-> motor neurone
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What are reflex actions for?
They aways have a survivle value. A reflex may be to get out of danger, to avoid damage to part of the body, or to maintain damage.
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What are some examples of reflex actions?
* Blinking reflex
* Knee jerk reflex
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What does the blinking reflex cause?
Causes the temporary closure of the eyelids to protect the eyes from damage.
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What sort of reflex is the blinking reflex?
It is a cranial reflex because it. passes through part of the brain.
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How is the blinking relex a relex action eventhough it passes through the brain?
The pathway does not involve any thought processes in the higher parts of the brain.
229
What is a reflex arc?
When the receptor and effector are in the same place.
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Where can a reflec arc be seen?
The blinking reflex.
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What may blinking be stimulated by?
* A forgein object touching the eye.
* Sudden bright light.
* Loud sounds.
* Sudden movements close to the eye.
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What does the corneal reflex consist of?
The reflex is produced by a sensory neurone in from the **cornea**, which enters the **pons**. A synapse connects the sensory, neurone to a relay neurone, which passes to the motor neurone to the **facial muscles**, causing the eyelids to blink.
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What is the corneal reflex pathway like?
It is a very short and direct pathway, so the corneal reflex is very rapid.
234
How can the corneal reflex be overridden?
the sensory neurone passes the action potential to **myelinated neurones in the pons**. These myeilinated neurones carry the action potential to the **sensory region in the cerebral cortex**, to inform the higher centres in the brain a stimulus has occured. This allows the reflex to be **overridden by conscious control** as the higher parts of the brain can send **inhibitory signals to the motor centres** in the pons.
235
Explain how action potentials can be inhibited in the brain.
* **Mylinated neurones** carry the action potential to the sensory reigon in the **cerebral cortex**- informing the brain a stimulus has occured.
* The higher parts of the brain (**cerebral cortex**) can **send inhibitory signals** to the **motor centre in the pons**.
* The mylinated neurones carrying impulses to and from the cerebral cortex transmit action potentials **rapidly** compared to the non-mylinated neurones in the pons- therefore, the **inhibitory actionx potentials can prevent the formation of an action potential in the motor neurone**.
236
What does the optical reflex do?
This protects the light-sensitive cells of the retina from damage.
237
Describe the process of the optical reflex?
The stimulus is **detected by the retina** and the reflex is **mediated by the optical centre in the cerebral cortex**.
238
Compare the corneal reflex and the optical reflex.
The optical reflex is a little slower than the corneal reflex.
239
What sort of reflex is the kee jerk reflex?
A spinal reflex.
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What are the types of reflex actions?
* Cranial reflex
* Spinal reflex
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What is a spinal relfex?
What an action potential passes through the spinal cord rather than the brain.
242
What is the knee jerk reflex involved in?
It is involved in coordinating movement and balence.
243
What muscles are involved in the knee jerk reflex?
The **quadsriceps** contract to straighten the leg- this muscle is attatched to the lower leg via the **patella tendon** that connects the pattella to the lower leg bones at the front of the knee. When the quadraceps are stretched, specialised **strech receptors** called **muscle spindles** detect the increase in length of the muscle. If the stretching is unexpected, a **reflex action causes the contraction of the same muscle.**
244
What do the muscle spindles do in the knee?
They detect the increase in length of the quadreceps.
245
How does the knee jerk reflex contitute to balence?
Contraction of the quads will occur when the body is leaning backwards, causing the body to move back over the legs.
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What is the speed of the knee jerk reflex like?
Only 2 neurones are involved so the responce is very rapid.
247
What neurones does the knee jerk reflex consist of?
Only 2 neurones:
sensory neurone -> motor neurone
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Can the brain inhibit the knee jerk reflex?
The higher brain is informed the reflex is happening, howver because there is **no relay neurone, the reflex cannot be inhibited**.
There is insufficent delay to enable inhibition.
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What does inhibition of reflex actions depend on?
It depends on **rapid myelinated neurones** carrying **inhibitory action potentials to the synapse** before the motor neurone is stimulated.
250
How are inhibitory action potentials sent to the synapse in the reflex acr to prevent contaction of the opposing muscle in the knee?
A **complex pattern of nervous impluses** coming from the cerebellum is able to inhibit the reflex contractions. As action potentials are sent to the hamstring, stimulating it to contract, inhibitory action potentials are sent.
251
What are the importabnt roles of the circulatory system?
* Tranport of oxygen and nutreints
* Removal of waste products
* Transport of urea from the liver to the kiddneys
* Distributed heat around the body or deliver it to the skin ot be radiated away
252
What nutrients is gtransported around the circulatory system?
* Glucose
* Fatty acids
* Amino acids
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what waste products are transported in the circulatory system so that they dont build up?
Carbon dioxide
254
What do the requirements of cells and tissues vary acording to?
Their level of activity.
255
The heart is a very active muscle, what does this mean for its requirements?
The heart muscle will need for oxygen and glucose allowing it to respire more to release energy for conrtaction.
256
What will happen to the amount of waste products produced in a muscle when the level of activity increases?
they will increase
257
Through what ways can the heart action be modified?
* Raising or lowering the heart rate (beats per min)
* Altering the force of the contractions of the ventricular walls
* Altering the stroke volume (vol of blood per beat)
258
The heart beats by itself in regular intervals. What word describes this?
The cardiac muscle is myogenic.
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How does the myogenic rate differ in the atrial muscle and the ventricle muscle?
The atrial muscle has a higher myogenic rate than the ventrical muscle.
260
Why is a coordination mechanism essential in the heart?
The artial muscle has a higher myogenic rate compared to the ventricular muscle but the 2 **chambers must contract in a corrdinated fashion** orr the heart action will be ineffective.
261
What is the hearts pace maker?
The sinostrial node (SAN).
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How does the SAN act as the hearts pacemaker?
The **SAN indicates waves of excitation the usually override the myogenic action of the cardiac muscle.** The wave of excitation travels over the atrial walls, through the AVN and down the purkyne fibres to the walls of the ventricles, causing them to contract.
263
What hormone does the heart muscle directly respond to?
Adrenaline
264
What controls the heart rate at rest?
The SAN.
265
What is the frequency of the wave of excitation in someones heart normally?
60-80 beats per min
266
What is the frequency of the waves of excitation in the heart altered by?
The frequency of these excitation waves is altered by the **cardiovascular centre in the medulla oblongata**.
267
Where do the nerves that supple the SNA come from?
They come from the cardiovascular centre in the medulla oblonaga.
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What part of the nervous system are the nerves travelling from the medulla oblongata to the SAN part of?
The autonomic nervous system.
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What do the nerves travelling from the cardiovasular centre to the SAN control?
They control the **frequency of contractions**. They DO NOT initiate contractions.
270
What nerves and hormones are involved in increasing 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.
271
What nerves and hormones are involved in reducing the heart rate?
Action potentials sent down the **vagus nerve** release the neurotransmitter **acetylocholine**, which reduces the heart rate.
272
How can enviromental factors affect the heart rate?
Input from sensory receptors is fed to the cardiovascular centre in the medulla oblongata.
273
What do the sensory input to the cardiovascular centre inculde?
* Stretch receptors
* Chemoreceptors
* Concentration of carbon dioxide in blood
274
How can stretch receptors in the muscle lead to a change in the heart rate?
Stretch receptors in the **muscles** detect the movement of the limbs. These send impulses to the **cardiovascular centre**, informing it that extra oxygen may soon be needed-increasing the heart rate.
275
How can stretch chemoreceptors lead to a change in the heart rate?
Chemoreceptors **monitor the pH** in the blood. When we exercise, the muscles produce more carbon dioxide- some of this reacts with the water in the blood plasma, producing a weak **carbonic acid**. This will reduce the pH, affecting the transport of oxygen. The change in pH is detected, sending an action potential to the **cardiovascular centre**- increasing the heart rate.
276
Where are chemoreceptors found?
* Carotid artery
* Aorta
* Brain
277
How can the concentration of carbon dioxide in the blood lead to a change in the heart rate?
When we stop exercising, the concentration of carbon dioxide in the blood falls- this reduces the activity of the accelerator pathway- reducing the heart rate.
278
How can stretch receptors in the wall of the carotid sinus lead to a change in the heart rate?
Stretch receptors in the walls of the carotid sinus **monitor blood pressure**. An increase in blood pressure is detected by the stretch receptors. If the pressure **rises too high**, the stretch recptors send an action potential to the cardiovasular centre- **reducing heart rate**.
279
What is the carotid sinus?
Its a small swelling in the carotid artery.
280
What nerve travels from the cardiovascular centre to the SAN to decreases the heart rate?
The Vagus nerve
281
What nerve travels from the cardiovascular centre to the SAN to increase the heart rate?
Accelerans nerve
282
hat happens if the mechanism controlling heart rate fails?
An artificial pacemaker must be fitted.
283
What does a pacemaker do?
It delivers an electrical impulse to the heart muscle.
284
Where would an artifical pacemaker be fit?
It would be implanted under the skin and flat on the chest. It may be connected to tehe SAN or directly connected to the ventricle muscle.
285
What is the carotid artery?
The carotid arteries are a pair of blood vessels located on both sides of your neck that deliver blood to your brain and head.
286
What is a creatine phosphate?
a compound is muscle that acts as **a store of phosphates** and can **supply phosphates** to **make ATP**.
287
What are myofibrils?
They are contractile units of skeletal muscle.
288
What are myofibrils made up of?
They contain 2 types of protein filament:
* **Thin filaments**, which are alignwed to make the **light** band; these are held together by the **Z line**.
* **Thick filaments**, which make up the **dark** band.
289
What is the H zone in the myofibrils?
In the myofibrils, the thin and thick bands overlap, but in the **middle of the dark band there is no overlap, the is the H zone.**
290
What is a Z line?
Light bands in a myofibril are held together by the Z line.
291
What is the distance between 2 Z lines in a myofibril?
The distance is called a **sarcomere**- this is the functional unit of the muscle. At rest, a sarcomere is about 2.5um long.
292
What are the thin and thick filaments surrounded by in the myofibrils?
They are surrounded by **sarcoplasmic rectilium**.
293
What are the thin filaments made up of in myofibrils?
The thin filaments are **actin**. Eacxh filament consists of **2 chains of actin subunits** twitsed around each other.
294
What is the structure of a thin filament in a myofibril?
Each filament is madeup of **2 actin subunits** twisted around eachother. Wound around the actin is a molecule of **tropomyosin** to which are attatched globular molecules of **troponin**.
295
In the thin filaments in myosin, what is the structure of the troponin molecules?
Troponin is a globular molecule- each complex consists of **3 polypeptides**: one binds to actin, One to tropomysoin and the 3rd binds to calcuim when available.
296
What is the function of tropmysin and troponin in a thin filament in a myfibril?
They are part of the mechanism to control muscular contraction.
297
At rest, what do tropomysin and troponin do in a thin filamant in a myofibril?
These molecules cover binding sites to which thick filaments can bind.
298
What does a think filament in a myofibril consist of?
Each thick fibril consists of a** bundle of myosin molecules**. Each myosin molecule has **2 protruding heads**, which stick out at the end of the molecuyle. These heads are **mobile** and can bind to actin when these binding sites are exposed.
299
What lead to the sliding filament hypothesis?
During contraction, the **light band and the H zone get shorter**. therefor, the** Z lines moze closer** together and the sacromere gets shorter. This observation lead to the sliding filament hypothesis.
300
What happens in the sliding filament hypothesis when a muscle contacts?
During contaction, the thick and thin filaments slide over one another.
301
What is the sliding action of the thick and thin filaments caused by during the contraction of a muscle?
Its caused by the myosin heads.
302
Describe the mechanism of contraction of a muscle. (sliding filament theory)
When the muscle is stimulated, the tropomyosin is moved aside, exposing the binding sites on the actin. The myosin heads attach and move, causing the actin to slide past the myosin.
303
Describe 6 steps which outlines the control of a muscle contraction.
1. When the muscle is stimulated, the action potential passes along the **sarcolemma** and down **transverse tubules** into the muscle fibre.
2. The action potential is carried to the **sarcoplasmic recticulum**, 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 **tropomyosin aside**. this exposes the **binding sites on the actin**.
4. **Myosin heads** bind to the actin, forming **cross-bridges** between the filaments.
5. The myosin heads move, pulling the actin filament past the myosin filament.
6. The myosin heads detach from the actin and can bind further up the actin filament.
304
How is energy released to supply energy for a muscle contraction?
Part of the myosin head acts ad **ATPase** can can hydrolyse the ATP to ADP and inorganic phosphate (Pi), releasing energy.
305
Describe the role of ATP in muscle contaction in 4 steps.
1. The myosin head attatches to the actin filament, formining a cross-bridge.
2. The myosin head moves (tilts backwards), causing the thin filament to slide past the myosin filament. This is a **power stroke** and **ADP and Pi are released** from the myosin head.
3. After the powerm stroke, a **new molecule of ATP attatched** to the myosin head, **breaking the cross-bridge**,
4. The myosin head then returns to its original posision as the ATP is hydrolysed, releasing energy for this movement to occur. The myosin head can now make a new cross-bridge further along the actin filament.
306
How does the myosin head move to cause the thin filament to move past the myosin filament?
It tilts backwards.
307
What is formed when the myosin head attatched to the actin filament?
A cross-bridge.
308
What is a power stroke uring a muscle contraction?
The myosin head tilts backwards, causing the thin filament to slide past the myosin filament- during this, **ADP and Pi are released** from the myosin head, **releasing energy.**
309
What happens after a power stroke in a muscle contraction?
A new molecule of ATP attatched to the myosin head, breaking the cross bridge, causing the myosin head to return ti its original position.
310
Why is there millions of myosin heads involved in muscle contraction?
There is a huge requirement for ATP.
311
How much of a contraction is the ATP available in the muscle able to support?
1-2 seconds worth of contraction.
312
Why must ATP must be regenerated very quickly in muscles?
ATP must be maintained as ATP available in tussle tissue is only enough to support 1-2 seconds of contraction.
313
How does aerobic respiration in mitochondria maintaining the supply of ATP in a muscle?
Muscles contain large numbers of mitochondria in which aerobic respiration. The bohr effect helps to release more oxygen from the haemoglobin in the blood. During intense activity, the rate at which ATP can be produced will be limited by the delivery of oxygen to the muscle tissue.
314
What are the 3 mechanisms involved in maintaining th supply of ATP in muscles?
* Aerobic respiration in miochondria.
* Anaerobic respiration in the sarcoplasm.
* Creatine phosphate on the sarcoplasm acting as a reserve store of phosphate groups.
315
How does aerobic respiration in mitochondria maintain the supply of ATP in muscle cells?
The cells contain a large number of mitochondria where aerobic respiration occurs. The **Bohr effect** helps to release **more oxygen** from the haemoglobin from the blood. However, during intense activity, the rate at which ATP can be produced will be **limited by thr oxygen delivery to tissues**.
316
How does Anearobic respiration in the sarcoplasm of the muscle tissue maintain the supply of ATP?
Anaerobic respiration can **release a little more ATP from the respiratory substrates**. However, it leads to the production of **lactic acid**, which is toxic. ANaerobic respiration can last a few seconds before lactic acid build up starts to cause fatigue.
317
Hoe does creatine phosphate in mussle tissues maintaing the supply of ATP?
Creatine phosphate in the sarcoplasm acts as a **reserve store of phosphate groups**. The phosphate can be transferred from the creatine phosphate to **ADP molecules**, creating ATP molecules very radidly. The enzyme **creatine phototransferase** in involved. The supply of creatine phosphate is sufficient to support muscular contraction for a further **2-4 seconds**.
318
What is adenyl cyclase?
An intracellular enzyme, which is activated by certain hormones.
319
What is cyclic AMP (cAMP)?
A secondary messenger releassed inside cells to activiate a responce.
320
What phycological changes would occur in the sympathetic system?
* Pupils dilate
* Heart reate and blood pressure increases
* Arterioles to digrestive system and skin are constricted, whilst those to the muscles and liver are dilated.
* Blood glucose levels increase.
* Erector pili muscles in the skin contract.
* Ventillation rate and detpth increase.
* Endorphins (natural pain killers) are released in the brain.
321
How is the sympathic system coordinated?
1.** Inputs** feed into the sensory centres in the **cerebrum**
2. The cerebrum passes the signsal to the associated centres. If a **threat** is recognised, the cerebrum stimulates the **hypothalamus**.
3. The hypothalamus **increases acitivity** in the sympathetic nervous system and stimulates the release of **hormones from the anterior pituitary gland**.
