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Plant and animal responses Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are features of the sympathetic nervous system?

A

Short pre-ganglionic, long post.
Noradrenaline
Increases heart rate as increases blood flow
Dilates pupils - more light in
Slows digestion - blood to muscles

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2
Q

What are features of the parasympathetic nervous system?

A

Long pre-gangiolic, short post in effector.
Acetylcholine
Decreases heart rate as slower blood flow
Decrease pupil diameter to protect retina
Increases digestion

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3
Q

What is in the CNS?

A

Mostly relay neurones. Brain and spinal cord.
Myelinated neurones make up white brain matter and long distances.

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4
Q

What is in the PNS?

A

Motor and sensory neurones. Lots are myelinated –> nerves.
Divides into motor (AP from CNS to effectors) and sensory (axons of sensory neurones into spinal cord via dorsal root).

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5
Q

What is in the somatic NS?

A

Voluntary with 1 motor neurone into the CNS without a synapse. Mostly myelinated.

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6
Q

What is in the autonomic NS?

A

Involuntary and controls homeostasis. Mostly unmyelinated .

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7
Q

What is the hypothalamus?

A

Control centre monitors blood and maintains homeostasis.

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8
Q

What is the pituitary gland?

A

Regulates many body functions, controlling activity of other glands.
Posterior - neurosecretory cells
Anterior - growth and reproduction

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9
Q

What is the cerebrum?

A

Controls voluntary actions, thought, vision, speech etc.
2 hemispheres.
Outer layer = cerebral cortex (vision) AP connects sensory and motor areas, mediate responses.

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10
Q

What is the cerebellum?

A

Muscle coordination and movement - provides complex signals and connects to motor cortex. Stores info of practiced pathways.

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11
Q

What is the medulla oblongata?

A

Controls involuntary actions - cardiac and smooth muscles. Cardiac, vasomotor and respiratory centres.

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12
Q

Where is the motor area?

A

Near the top of the cerebrum - complexity reflected by size of area for body part.

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13
Q

What is a reflex?

A

Rapid, involuntary responses. Short lives and localised as involve few synapses and bypass brain.

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14
Q

How does the blink reflex work?

A

Sensory neurone in cornea detects stimulus -> relay neurone in pons.
Unmyelinated relay passes AP to motor.
Signal to effectors (cranial muscles) - contract and blink.

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15
Q

Can the blink reflex be overridden?

A

Yes, consciously. Cerebral cortex sends in inhibitory signals to motor centre.

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16
Q

How does the knee jerk reflex work?

A

Stimulates specialised stretch receptors = muscle spindles. Sensory neurone signal to spinal cord to motor neurone.
Signal to quadriceps muscle - contracts and pulls patellar tendon, straightening knee.

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17
Q

What are the features of cardiac muscle?

A

Uninucleated.
Cells form long, branched fibres - even electric stimulation. Heart pumps smoothly.
Intercalated discs for free ion diffusion.
Myogenic - SAN controls contraction without fatigue.

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18
Q

What are the features of involuntary muscle?

A

Contracts slowly and regularly.
Indiv. cells pinched down at both ends. Each contains actin and myosin.
Uninucleated.
Longitudinal circular layers for peristalsis.
Found in walls eg. blood vessels, intestines.

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19
Q

What are the features of voluntary muscles?

A

Cells fused -> long cylindrical cells = muscle fibres, contain many nuclei.
Many mitochondria + specialised ER.
Each fibre has many myofibrils - contraction. Made from actin and myosin.
Contract quickly + powerfully but fatigue fast.

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20
Q

What is a neuromuscular junction?

A

The point at which a motor neurone meets a muscle fibre.
A muscle has many motor units - control force of contraction.
- presynaptic neurone has many mitochondria + vesicles with ACh.

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21
Q

How does a muscle contract?

A
  1. at rest, vesicles present in pre synaptic motor neurone
  2. AP reaches end of axon, VG Ca2+ channels open -> Ca2+ diffuse into neurone
  3. Ca2+ cause synaptic vessels to move + fuse with presynaptic membrane / release ACh into synapse
  4. ACh diffuses across gap + binds with receptors on muscle cell surface membrane - Na+ channels open
  5. Na+ enter muscle fibre -> depolarisation + triggers AP
  6. wave of depolarisation passes along sarcolemma as AP spreads along muscle fibre - wave passes down into transverse tubules = MUSCLE CONTRACTION
22
Q

What is skeletal muscle?

A

Made of bundles of muscle fibres - contain many long, cylindrical structures = myofibrils (made of actin + myosin). For muscle contraction, myofilaments slide over each other - shorten sarcomere length. Sliding filament theory.

23
Q

What are the different parts of a sarcomere (1 repeating unit of myofibril)?

A

I bands formed of thin actin filaments.
A bands - actin + myosin filaments overlap.
Centre of A band = H zone - myosin.
Centre of I band = Z line (end of sarcomere).
M line divides H zone and marks middle of sarcomeres.

24
Q

What is myosin?

A

Bundles make up thick filaments. Consists of long, rod shaped tails + bulbous heads. Heads bind to actin when sites = exposed.

25
Q

What is actin?

A

Makes up thin filaments. 2 strands of actin subunits twisted together.

26
Q

What are tropomyosin and troponin?

A

Attached to tropomyosin = globular molecules of troponin - 3 polypeptides; 1 bound to actin, 1 to tropomyosin, 1 to Ca2+ when available. At rest, block binding sites on thin filament where thick binds during contraction.

27
Q

What is a summary of sliding filament theory?

A

I band becomes narrower, Z lines move closer, H zones become narrower.
Sarcomeres contract due to myosin head movement - interact with actin -> cross bridges.

28
Q

What happens during sliding filament theory?

A
  1. AP arrives at NMJ - travels into muscle fibre via T-tubules, in contact with sarcoplasmic reticulum of fibre
  2. AP reaches SR, triggers SR stores to release Ca2+ into sarcoplasm
  3. Ca2+ binds to troponin associated with actin filaments. Ca2+ binding -> troponin changes shape and pulls away tropomyosin - expose binding site on actin filament
  4. Myosin can attach to actin + form cross bridge. Myosin head attached to ADP + Pi
  5. Myosin heads change angle and pull actin filaments past myosin, shortening sarcomere = power stroke (ADP + Pi released)
  6. New ATP attaches to myosin head, breaking cross bridge. Heads return to OG positions and detach from actin. ATP hydrolyses + ADP+Pi bind.
  7. Myosin heads attach to another binding site further down.
29
Q

How is muscle contraction stopped?

A

After contraction, Ca2+ pumped back into SR so actin filament blocked by tropomyosin - contraction stops.

30
Q

What are sources of ATP for muscle contraction?

A

Myosin head contains ATPase. Energy needed to move myosin heads, reabsorption of Ca2+ by active transport.
- many mitochondria in muscles
- anaerobic respiration occurs in muscle cell sarcoplasm
- creatine phosphate stores phosphate groups + donates to ADP.

31
Q

What is the mechanism of controlling heart rate?

A

In right atrium is the SAN - starts wave of electrical stimulation.
- wave to atrial walls and contract simultaneously. Depolarisation SAN to AVN
- signal to atrial septum - thin collagen layer stops reaching ventricles so to AVN
- AVN signal to ventricles then to bundle of His with slight delay
- bundle of His to Purkinje fibres + branch into each ventricles (contract from base up)

32
Q

What are the 2 nerves in the medulla oblongata?

A

Accelerator nerve - SNS, high frequency of impulses to SAN to increase heart rate
Vagus nerve - PNS, lowers heart rate by low frequency of impulses

33
Q

How can heart rate increase/decrease?

A

Due to internal stimuli - chemoreceptors and baroreceptors.

If high blood pressure, baroreceptors to medulla to parasympathetic neurones. Ach released in cardiac muscle - bind to receptors on SAN.
Noradrenaline and sympathetic neurones if low blood pressure.

Which one is active depends on how many depolarisations these nerves make.

34
Q

What are the similarities and differences between plant and animal hormones?

A

Differences: animal from endocrine, transported in blood, fast acting, act on target cells only. Plant from cells, in phloem/xylem, slow acting, act on most cells.

Similarities: chemical messengers made in cells, can be moved from production site, ST or LT, affect gene expression.

35
Q

What are chemical responses in plants?

A

Tannins - toxic to microorganisms and herbivores. In upper epidermis.
Alkaloids - derived from aa and taste bitter.
Pheromones - affect behaviour/physiology of other organisms.

36
Q

What is tropism and what are the different types?

A

Directional growth response - direction determined by direction of external stimulus.

Phototropism, geotropism, chemotropism, thigmotropism.

37
Q

What is a mastic response?

A

Non directional response to external stimuli.
Eg. Mimosa pudica plant responds to touch and leaves fold up.

38
Q

What are the different types of meristems?

A

Apical - tips of roots and shoots
Lateral bud - forms side shoots
Lateral - widening of roots and shoots
Intercalary - between nodes, shoot getting longer

39
Q

What is the function of auxin?

A

Control plant photo and geotropic responses by regulating cell elongation. Auxin leads to an increase in the plasticity of cell walls, so stretch easier when cell elongates. Moved by diffusion to cell to zone of elongation.

Causes H+ AT into spaces in cell wall, activate proteins = expansins and loosen cellulose, decrease rigidity. Break bonds in cellulose, so walls expand as cell takes in water via osmosis.

40
Q

What is the mechanism of phototropism?

A

Cells in shoot tip produce auxin and transported evenly down shoot. Light causes auxin to move from light to shaded side. Leads to elongation of shoot cells - bends to light.

In roots, has opposite effect - high auxin concentration inhibits cell elongation so faster on light side and bends away

41
Q

What is the mechanism of geotropism?

A

Auxin produces in root tip and evenly distributed. Gravity causes auxin to move from upper to lower side. Auxin inhibits root cell elongation so it bends down to gravity.

42
Q

How do enzymes and auxin work together?

A

Cause redistribution of auxin in response to light. Phototropin 1 and 2.
- activity enhanced by blue light, increasing activity on light side
- gradient leads to auxin redistribution via effects on PIN proteins (found in all sides of plant membranes) - control outflow of auxin from cells
- PIN proteins controlled by PINOID but only works with short bursts of light

43
Q

What did experiments find about auxin?

A

Shoot tip is responsible for phototropic responses - water and solutes need to move backwards form tip for phototropism to occur
When gelatine block placed on shoot tip, positive phototropism seen. But when mica block used, no response. So messenger = diffusable.

When tip placed on agar block and block on top of cut plant, shoot grew as messenger diffused into agar then to plant. Plain agar block showed no growth.

44
Q

What are the main types of plant hormones?

A

Cytokinins - delay leaf senescence + help maintain nutrient supply in leaves. Cell division and expansion increased.
Auxins - promote cell elongation and inhibition of side shoot growth. Inhibit leaf abscission, present in leaves.
Abscisic acid - low water availability - stomata closes and decreases loss via transpiration. Inhibits seed germination and growth.
Gibberellins - promote seed germination and stem growth.
Ethene - fruit ripening.

45
Q

How can apical dominance be observed?

A

If shoot tip removed, side branches start growing. To determine exact effect: ends of shoot cut and auxin layer applied. No lateral bud growth.

Normal auxin levels inhibit growth., low levels promote.

46
Q

How are abscisic acid and cytokinins involved in apical dominance?

A

Abscisic acid - high when high auxin, so growth inhibited. So tip cut, acid decreases so buds can grow.
Cytokinins - apply directly to buds can override apical dominance. High auxin makes shoot tip a cytokinin sink. Auxin gone, cytokinin spreads evenly.

47
Q

What are the functions of gibberellins?

A

Control stem elongation and seed germination. Breaks starch to glucose which plant embryo uses for respiration.
GA levels in tall pea plants and dwarf were compared. Tall plants had higher levels.

Leaf loss in winter - some plants lose leaves. Older leaf, more ethene it makes. So leaf falls. Ethene - layer of cells at leaf base = abscission layer to expand - breaks cell wallls.

Stomatal closure - Abscisic acid binds to guard cells and opens Ca2+ channels. Some enters guard and opens K+ channels. Lots K+ leaves so less negative water potential. Water leaves by osmosis.

48
Q

What are commercial uses of auxin?

A

Prevent leaf and fruit abscission
- treat unpollinated flowers to form seedless fruits
- weedkillers - excessive apical dominance so grows too fast and dies
- root powder - roots grow fast (fast and cheap)

49
Q

What are commercial uses of cytokinins?

A

Prevent yellowing of plant leaves after being picked
- mass production because increases bud and shoot growth
- side branches split and grow separately

50
Q

What are commercial uses of gibberellins?

A

Fruit production - elongates stems so more space to grow bigger. Increases sugar production in sugar canes.

51
Q

What are commercial uses of ethene gas?

A

Controls ripening and rotting.
- increase fruit drop and speed up ripening
- prevent ethene synthesis (low temp stores) with low O2 and high CO2
- increases shelf life

Biology (32 decks)

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