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Biology - Module 5 > 5.1.5 - Plant and Animal Responses > Flashcards

5.1.5 - Plant and Animal Responses Flashcards

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1
Q

What is the mammalian nervous system made up of?

A
  • Peripheral nervous system
  • Central nervous system
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2
Q

What is the peripheral nervous system made up of?

A
  • Receptors
  • Sensory neurones
  • Motor neurones
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3
Q

What is the central nervous system made up of?

A
  • Brain
  • Spinal cord
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4
Q

What can the peripheral nervous system be split into?

A
  • Autonomic nervous system
  • Somatic nervous system
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5
Q

What does the autonomic nervous system do?

A

It works constantly subconsciously. This includes activities such as digestion and heart rate which we have no conscious control over.

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6
Q

What does the somatic nervous system do?

A

It is consciously controlled and includes voluntary activities such as muscle movement.

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7
Q

What are the differences in function between the sympathetic and parasympathetic nervous system?

A
  • S uses noradrenaline but P uses acetylcholine
  • S increases breathing rate but P reduces this
  • S increases blood flow to skeletal muscle but P increases blood flow to the gut
  • S prepares body for the ‘fight or flight’ response but P rests
  • S increases heart rate but P reduces it
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8
Q

What is the function of the cerebrum?

A
  • Receives sensory information, interprets it and sends out motor impulses to bring about a voluntary response
  • Site of learning, reasoning, intelligence, personality, memory and conscious thought
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9
Q

What is the function of the cerebellum?

A

Coordinates muscles movement such as balance and fine movement

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10
Q

What is the function of the medulla oblongata?

A
  • Controls non-skeletal muscle
  • Control centre for the autonomic nervous system
  • Contains regulatory centres - cardiac and respiratory centres
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11
Q

What is the function of the hypothalamus?

A
  • Controls most of the body’s homeostatic mechanisms such as temperature and water balance
  • Links the nervous and endocrine systems
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12
Q

What is the function of the pituitary gland?

A
  • Regulated by the hypothalamus
  • Stores hormones such as ADH
  • Secretes hormones to coordinate responses such as osmoregulation
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13
Q

What are reflex actions?

A

Rapid automatic responses to protect from danger

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14
Q

Why are reflex actions rapid?

A

They are made up of 3 neurones so there are only 2 synapses which speeds up the transmission. The brain is not involved as there is no conscious decision needed which also makes the response rapid.

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15
Q

How do reflex arcs generate a response?

A
  • Once the stimulus is detected by a receptor an impulse is passed along the sensory neurone to a relay neurone
  • The relay neurone passes the impulse onto a motor neurone which is connected to an effector
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16
Q

What are two examples of reflex actions?

A
  • Knee jerk reflex
  • Blinking
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17
Q

How does the knee jerk reflex happen?

A
  • When the leg is tapped just below the kneecap it stretches the patellar tendon and acts as a stimulus
  • This stimulus initiates a reflex arc that causes the extensor muscle on top of the thigh to contract
  • At the same time a relay neurone inhibits the motor neurone of the flexor muscle causing it to relax
  • This contraction coordinated with the relaxation of the antagonistic flexor hamstring muscle causes the leg to kick
  • After the tap the leg is normally extended once and comes to rest
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18
Q

How does the blinking reflex happen?

A
  • When the cornea of the eye is irritated by a foreign body the stimulus triggers an impulse along a sensory neurone
  • The impulse then passes through a relay neurone in the lower brain stem
  • Impulses are then sent along branches of the motor neurone to initiate a motor response to close the eyelids
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19
Q

What is the fight or flight response?

A

When mammals are exposed to a potential threat to their survival a series of automatic responses are triggered to prepare the organism to either fight to survive or to run away from danger.

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20
Q

How does the fight or flight response work?

A
  • The autonomic nervous system detects the potential threat sending an impulse to the hypothalamus
  • This results in more impulses being transmitted along the sympathetic nervous system and the adrenal cortical system
  • The effectors are the adrenal glands which will release more adrenaline and noradrenaline
  • These hormones trigger the hypothalamus to stimulate the release of adrenocorticotropic (ACTH) from the pituitary gland
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21
Q

How does adrenaline work as a first messenger?

A
  • Adrenaline binds to receptors with a complementary shape on the surfaces of target cells which causes a G protein to be activated
  • This in turn activates adenylyl cyclase which converts ATP to cyclic AMP (cAMP)
  • cAMP acts as a second messenger by activating enzymes by altering their 3D structure that can hydrolyse glycogen into glucose
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22
Q

How is the heart rate controlled?

A

The sinoatrial node in the wall of the right atrium of the heart is connected to the cardiovascular centre in the medulla oblongata in the brain by the autonomic nervous system. The autonomic nervous system influences the heart rate to slow down via the parasympathetic nervous system or to increase it via the sympathetic nervous system.

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23
Q

How are changes in pH/carbon dioxide levels detected?

A

By chemoreceptors in the aorta, carotid artery and medulla oblongata

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24
Q

How does the heart rate change in response to pH?

A
  • The pH of the blood will decrease during times of high respiratory rate due to the production of carbon dioxide or lactic acid
  • Excess acid must be removed from the blood rapidly to prevent enzymes denaturing
  • This is achieved by increasing the heart rate (more impulses via sympathetic nervous system to SAN) so carbon dioxide diffuses out into the alveoli more rapidly
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25
Q

How are changes in blood pressure detected?

A

By baroreceptors in the aorta, vena cava and carotid arteries

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26
Q

How does the heart rate change in response to pressure?

A
  • If the blood pressure is too high this can cause damage to the walls of the arteries so the blood pressure is reduced by sending more impulses via the parasympathetic nervous system to decrease the heart rate
  • If the blood pressure is too low there may be insufficient supply of oxygenated blood to respiring cells and removal of waste so more impulses are sent via the sympathetic nervous system to increase the heart rate
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27
Q

What are the three types of muscle fibres?

A
  • Cardiac
  • Skeletal
  • Involuntary
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28
Q

What is the function of cardiac muscle?

A

To pump blood

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29
Q

What is the structure of cardiac muscle?

A
  • Striated appearance
  • Cells are divided by intercalating discs
  • Fibres are made of many cells in rows
  • Branched cells
  • Uninucleate
30
Q

What is the function of skeletal muscle?

A

To move bones

31
Q

What is the structure of skeletal muscle?

A
  • Multinucleate
  • Striated bands of actin and myosin
  • Cylindrical cells
32
Q

What is the function of involuntary muscle?

A

For unconscious actions such as uterine contraction and controlling pupil size

33
Q

What is the structure of involuntary muscle?

A
  • Unstriated
  • Spindle shaped cells
  • Uninucleate
  • Found in antagonistic pairs
34
Q

What are myofibrils made up of?

A

Fused cells that share nuclei and cytoplasm known as sarcoplasm and there are high numbers of mitochondria

35
Q

What is a neuromuscular junction?

A

The place where a motor neurone meets a muscle fibre

36
Q

What is the action of neuromuscular junctions?

A
  • When a nerve impulse arrives at the junction acetylcholine (ACh) is released into the synaptic cleft
  • ACh binds to its receptor on the postsynaptic membrane (sarcolemma) which allows sodium ions to rapidly enter the muscle fibre causing depolarisation of the membrane and muscle contraction
37
Q

What are the two protein filaments involved in muscle contraction?

A
  • Actin - two thin strands which are twisted together
  • Myosin - thick filaments with heads at each end arranged in bundles
38
Q

What is the A band in a sarcomere?

A

Length of the myosin including the overlapping actin

39
Q

What happens to the length of the A band when the muscles contract?

A

It stays constant

40
Q

What is the H zone in a sarcomere?

A

Just myosin with no actin overlapping

41
Q

What happens to the length of the H zone when the muscles contract?

A

It shortens

42
Q

What is the I band in a sarcomere?

A

Just actin with no myosin overlapping

43
Q

What happens to the length of the I band when the muscles contract?

A

It shortens

44
Q

What is the Z band in a sarcomere?

A

The end of one sarcomere

45
Q

What happens to the Z bands when the muscles contract?

A

They get closer together

46
Q

What is the sliding filament model?

A
  • When an action potential reaches a muscle it stimulates a response
  • Calcium ions bind to troponin causing it to change shape and causing the protein tropomyosin to move aside and expose the binding sites on actin
  • Whilst ADP is attached to the myosin head it binds to the actin to form a cross bridge
  • The angle created in this cross bridge creates tension and as a result the actin filament is pulled and slides along the myosin which releases the ADP molecules
  • An ATP molecule then binds to the myosin head and causes it to change shape slightly so it detaches from the actin
  • Within the sarcoplasm there is the enzyme ATPase which is activated by the calcium ions to hydrolyse the ATP on the myosin head into ADP and releases enough energy for the myosin head to return to its original position
  • This entire process repeats continually whilst the calcium ions remain high and therefore whilst the muscle remains stimulated by the nervous system
47
Q

How is the supply of ATP maintained?

A

The chemical phosphocreatine which is stored in muscles assists this by providing phosphate to regenerate ATP from ADP

48
Q

What are the 2 types of plant responses?

A
  • Abiotic stress which is caused by abiotic factors such as temperature, light or water
  • Herbivory through physical defences (thorns or spikes), chemical defences or touch response
49
Q

What is an example of a response to abiotic stress?

A

In an environment where less water is available a plant risks losing even more water through transpiration so to reduce the rate of transpiration the plant shuts its stomata

50
Q

What are the 3 chemicals plants can use as chemical defences?

A
  • Alkaloids
  • Pheromones
  • Tannins
51
Q

How do alkaloids work?

A

Tobacco plants produce an alkaloid called nicotine and to most herbivores alkaloids are toxic causing the leaf eating herbivores to die which enables the plant to survive and reproduce

52
Q

How do pheromones work?

A

Some plants release pheromones which trigger nearby plant leaves to produce more callose which causes the leaves to become harder for herbivores to eat enabling the plant to survive and reproduce

53
Q

How do tannins work?

A

Most tannins are toxic to herbivores causing them to die which enables the plant to survive and reproduce

54
Q

What is an example of the touch response?

A

The plant mimosa pudica folds its leaves when touched

55
Q

What is tropism?

A

When part of a plant has a directional growth response to a stimulus

56
Q

What is phototropism?

A

When light causes tropism

57
Q

What happens during phototropism in shoot tips?

A
  • Auxin concentrates in cells that are not facing the light
  • This is because a higher auxin concentration stimulates cell elongation in shoot tips
  • This causes the shoot tip to bend towards the light
58
Q

What is geotropism?

A

When gravity causes tropism

59
Q

What happens during geotropism in root tips?

A
  • Auxin concentrates in cells that are facing gravity
  • This is because a higher auxin concentration inhibits cell elongation in root tips
  • This causes the root tip to bend towards gravity
60
Q

What are plant hormones?

A

Signalling molecules that enable plants to respond to changes in the environment

61
Q

What do plant hormones enable plants to do?

A
  • Avoid abiotic stress such as cold or heat
  • Avoid predators
  • Access resources such as light, minerals and water
62
Q

What are the 3 roles of auxin?

A
  • Stimulates cell elongation in shoot tips
  • Inhibits leaf loss in deciduous plants during spring and summer which ensures plants are able to photosynthesise and build up a glucose storage for autumn and winter
  • Maintains apical dominance meaning the tip of the plant’s stem is dominant over its lateral branches
63
Q

What is the evidence for the role of auxins in the control of apical dominance?

A
  • In conifers auxin concentrates at the stems tip which stimulates those cells to grow longer causing the stem to grow upwards
  • At the same time high auxin concentration in the tip inhibits the growth of lateral branches
  • If we remove the stem’s tip these lateral branches start to grow
64
Q

What are the 3 roles of gibberellin?

A
  • Stimulates seed germination which is when a seed is developing into a plant
  • Stimulates stem elongation by stimulating cell elongation and cell division in the stem of the plant
  • Stimulates stomatal closure which ensures plants don’t lose even more water through transpiration
65
Q

How does gibberellin control seed germination?

A
  • When a seed absorbs water the embryo inside the seed produces gibberellins
  • These gibberellins activate genes that code for amylases and proteases
  • These enzymes break down the food stores inside the seed into glucose
  • Glucose is transported back to the embryo providing energy for its growth
66
Q

What are the 2 roles of ethene?

A
  • Stimulates leaf loss in deciduous plants during autumn
  • Stimulates fruit ripening in the summer
67
Q

What are the 4 key differences between plant hormones and animal hormones?

A
  • Plant hormones can be produced in many plant tissues while animal hormones are only produced in endocrine glands
  • Plant hormones are transported from cell to cell while animal hormones are only transported inside the bloodstream
  • Plant hormones act on most cells while animal hormones only act on specific cells
  • The response triggered by plant hormones is slower than the response triggered by animal hormones
68
Q

What are the 3 commercial uses of plant hormones?

A
  • Use ethene to control fruit ripening
  • Use auxin to grow cuttings
  • Use auxin as a weedkiller
69
Q

How is ethene used to control fruit ripening?

A
  • Ethene stimulates fruit ripening
  • Commercial farmers harvest fruits before they are ripe because they are easier to transport than soft ripe fruits meaning they won’t get damaged when they are shipped
  • Once they’ve arrived at their destination and are ready to be sold the unripe fruits are exposed to ethene gas which turns them into soft ripe fruits ready to be eaten
70
Q

How is auxin used to grow cuttings?

A
  • Auxin stimulates root growth
  • Cut a small piece from a plant stem called a cutting
  • Dip it into rooting powder that contains auxin
  • Plant the cutting into the soil allowing the new plant to form
71
Q

How is auxin used as weedkiller?

A
  • Auxin stimulates shoot growth
  • When applied at high concentrations auxin causes uncontrolled shoot growth which means the plant dies
  • Apply a high concentration of auxin to a weed plant as a result the weed plant grows too fast and dies

Biology - Module 5 (7 decks)

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