5.5 Plant & Animal responses Flashcards
What the difference between biotic and abiotic components?
Biotic is a living components whilst abiotic are non living
What are tropisms , name some?
directional growth responses in a plant • Phototropism • Geotropism • Chemotropism • Thigmotropism • Thermotropism • Hydrotropism
What is Phototropism?
Shoots grow towards light to enable photsynthesis
What is Geotropism?
Roots grow towards pull of gravity. Anchors them in soil and helps water uptake
What is Chemotropism?
Pollen tubes growing towards chemicals(in ovaries where fertilisation occurs)
What is Thigmotropism?
growth in response to touch like winding around structures for support
What are the plant relevant Hormones?
- Auxin
- Ethene
- Gibberellin
- Abscisic acid
- Cytokinin’s
What is the role of Auxin?
- directional growth, elongation & inhibition
- inhibits side shoot growth, by causing absicic acid release
- inhibits leaf fall(abcession)
What is the role of Ethene?
• Promotes fruit ripening
What is the role of Gibberellins?
- Promotes Seed Germination
* Stem Growth, elongation of cells at internodes
What is the role of Abscisic acid?
- inhibits lateral bud growth
- causes stomatal closure when low water availability
- Inhibits Seed Germination
What is the role of Cytokinin’s?
- Promotes lateral bud growth
- Delays leaf senescence
- promotes cell division & expansion
What are some other chemical plant responses?
- Bitter-tasting tannins
- Bitter-tasting nitrogen compounds (alkaloids)
- Release cell-signalling pheromones to trigger defensive responses in other organism
How is leaf fall (leaf abscission) in deciduous plants triggeredd?
- As leaf ages auxin levels lower, ethene level increases.
- enzymes weaken leaves by breaking down cell walls
- Leaves break from branch.
How is Germination stimulated?
- Seed absorbs water, activating embryo to secrete gibberellins.
- Gibberellins diffuse to aleurone layer, which produces amylase.
- Amylase hydrolyse starch.
- Hexose sugars act as respiratory substrate to produce energy for growth/ protein synthesis
What are Meristems?
Immature plant cells still capable of dividing
What does ‘Apical’ imply?
at the apex(tip) of roots or shoots
What does ‘lateral’ imply?
from the sides
Explain why shoots show positive Phototropism.
- Auxin produced at shoots Apex, diffuses to shaded side of shoot tip.
- Auxin diffuses down shaded side, it causes active transport of H+ ions into cell wall.
- Ph change makes optimal conditions for expansins (enzymes) make cell more permeable to water
- Cells on shaded side elongate faster
- Shoot bends towards light.
Explain why roots show positive Gravitropism.
- Gravity causes auxins to accumulate on lower side of the root.
- Auxins inhibits elongation of root cells.
- Cells on the upper side of the root continue to grow, so the root tip bends downwards.
How do hormones stimulate stomata to close?
- Abscisic acid binds to complementary receptors on guard cell membrane,
- causing ions leave
- Water potential of guard cell becomes more positive. Water diffuses out
- Guard cells become flaccid so stomata close.
What is Apical dominance?
Phenomenon where during the growth of the shoot, the growth of side shoots does not take place. Maintained by the action of auxin, abscisic acid & cytokinins
Explain the experimental evidence that auxins maintain Apical dominance
Auxin production in apex maintains high levels of abscisic acid. Inhibits growth of side shoots.
When apex is removed:
a) Auxin levels drop, causing abscisic acid levels to drop.
b) Cytokinin’s initially concentrated near auxin reserve in bud diffuse evenly to promote bud growth in other parts of plant (lateral buds)
Explain the experimental evidence that Gibberellins control stem elongation and germination
- Stem elongation: Tall plants have higher gibberellin concentration than dwarf plants.
- Germination: Mutant seeds with non-functional gibberellin gene do not germinate unless gibberellin is applied externally.
- Inhibitors of gibberellin production prevent germination & growth
How are Auxins used commercially?
- rooting powder(dip cutting in auxin before planting for better growth)
- growing seedless fruit
- herbicides(promote shoot growth till plant can no longer support ,buckles then dies
How are Cytokinin’s used commercially?
- delaying leaf senescence(aging), leaves fresher for longer
* promotes shoot growth in tissue cultures
How are Gibberellins used commercially?
- elongation stems , fruits more grwoth space
- Malt production for beer brewing(Barley seeds + Gibberellin = amylase to breakdown starch to maltose
- stimulate growth between nodes of sugar cane(that’s where they store sugar∴ more stored)
How is Ethene used commercially?
• speeds up ripening,
• promotes fruit drop
*Restricting Ethene prevents ripening so fruits can be stored longer
Outline the gross structure of the mammalian nervous system.
CNS(spinal cord & Brain)
OR
Peripheral (Motor & Sensory)
↓
Motor (Autonomic & Somatic)
↓
Autonomic(symp or parasympatheticName the two main divisions of the Nervous system
- Central nervous system (Comprised of brain & spinal cord. Specialised system of nerve cells )
- Peripheral nervous system (all neurons that are not part of the CNS).
Name the two main divisions of the Motor nervous system
- Somatic (under conscious control)
* Autonomic (not under conscious control)
Name the two main divisions of the Autonomic nervous system
Sympathetic: often stimulates effectors (fight-or-flight response), neurotransmitter noradrenaline,
Parasympathetic: often inhibits effectors (rest/digest response), neurotransmitter acetylcholine
*Act antagonistically to eachother
Describe the gross structure of the human brain
2 hemispheres joined by band of nerve fibres (corpus callosum). Divided into lobes
Identify the location and function of the Cerebrum
Uppermost part of the brain which controls (initiates) voluntary functions (thinking)
Identify the location and function of the Cerebellum
Backmost part of the Brain.
Controls execution (not initiation) of movement, balance, coordination, timing etc.
*responsible for ‘Muscle memory’
Identify the function of the Hypothalamus& pituitary
Coordinates homeostatic responses & secretes hormones
Identify the location and function of the Medulla Oblongata
Controls a range of autonomous functions including;
• breathing rate & depth (respiratory centre)
• heart rate (cardiac centre)
What are some effects the Sympathetic system may bring?
fight or flight
- Increase heart rate
- Dilate pupils
- reduce digestive activity
- Noradrenaline neurotransmitter
What are some effects the Parasympathetic system may bring?
Rest & digest
- Decrease heart rate
- Constrict pupils
- Increase digestive activity
- Acetylcholine neurotransmitter
What is a Reflex?
An involuntary response to a stimuli
*can be overridden
Outline what happens in a simple reflex arc
receptor detects stimulus → sensory neuron → relay neuron in CNS coordinates response → motor neuron → response by effector
Why are Reflexes beneficial?
Survival: rapid response to potentially dangerous stimuli since only 3 neurons involved, instinctive.
Describe the Knee jerk reflex
a spinal reflex important for maintaining balance & posture
- Tapping patellar tendon stimulates stretch receptors.
- Impulse travels from sensory→ motor (no interneuron)
- Quadriceps contract.
what triggers the Blinking reflex
- Sudden Movement close to eye
- Foreign object touching eye
- Sudden bright light
- Loud sounds
what is the Corneal reflex Mechanism
stimulus→ sensory neuron→ sensory centre in pons→ Motor centre in pons→ Motor neuron →muscle
*can be overridden by conscious thought( going to cerebral cortex and inhibitory signals)
what is the Optical reflex
if bright light shines in ya eyes the pupils constrict, if little light they dilate to let more light in
What is the ‘Fight or Flight’
If brain perceives threat, it stimulates autonomic stress responses involving adrenaline. Triggers physiological changes to prepare body
What are some ‘Fight or Flight’ response?
- Pupils dilate so ya see more
- glucose levels increase
- heart rate and BP increase so more blood flow and rid of toxins
- Endorphins (natural painkillers)
Use the secondary messenger model to explain how Adrenaline works
- Adrenaline 1st messenger. Hormone-receptor complex forms.
- Conformational change to receptor activates G-protein.
- Activates adenylyl cyclase, which converts ATP to cyclic AMP (cAMP).
- cAMP 2nd messenger. Activates protein kinase A pathway.
- Results in glycogenolysis
Describe the 3 types of muscle tissue
- voluntary skeletal muscle
- involuntary Smoothe muscle
- Cardiac muscle
Describe the gross structure of a muscle
Muscle made of Myocytes(muscle cells/fibres)
Muscle fibres made of fused myofibrils
Myofibril made of many sarcomere subunit
Describe the structure of skeletal muscle
involved in skeletal movement
made of fused Myofibrils, • Multinucleated muscle cells • Sarcoplasm: muscle cell cytoplasm • Sarcolemma: mucle cell membrane • Sarcoplasmic reticulum * striated
Describe the structure of Cardiac muscle
involved in heart beating
• long fibres with cross bridges
• Cross bridging & Branching ensure even spread of electricity
• Intercalated disks fuse cells allowing free diffusion of ions between cells
*striated
Describe the structure of Smooth muscle
involved in constricting blood vessels and tubular structures
- ciruclar layer runs around muscle
* longitudinal layer runs through
The ultrastructure of a Myofibril (1 Sarcomere)?
- I-band: only actin (appears light)
- H-zone: only myosin.
- A-band: overlap of actin & myosin (appears dark)
- Z-line: boundary between sarcomeres.
How is impulse travel across neuromuscular junction
- action potential = voltage-gated Ca2+ channels open.
- Vesicles move towards & fuse with presynaptic membrane.
- Exocytosis of acetylcholine (ACh), which diffuses across synaptic cleft.
- ACh binds to receptors on Na+ channel proteins on skeletal muscle cell membrane.
- Influx of Na+ = depolarisation
Explain the role of Ca2+ ions in Muscle contraction
- Action potential moves through sarcoplasm = Ca2+ channels in sarcoplasmic reticulum open.
- Ca2+ binds to troponin, triggering conformational change and moving tropomyosin.
- Exposes binding sites on actin filaments so cross bridges can form
Outline the ‘sliding filament theory’
during contraction Myosin continually attaches& reattaches to actins further along filament, ‘sliding’ past eachother
How does sliding filament action cause a Myofibril to shorten?
- Myosin heads flex in opposite directions = actin filaments are pulled towards each other.
- Distance between adjacent sarcomere Z lines shortens.
Explain the role of creatine phosphate in muscle contraction
store of extra phosphates for ADP, helps form ATP
State the name and location of the 2 nodes involved in heart contraction
Sinoatrial node (SAN): within the wall of the right atrium. Atrioventricular node (AVN): near lower end of right atrium in the wall that separates the 2 atria
Name the receptors that detect blood Pressure & PH changes
- Baroreceptors (detect changes in blood pressure)
* Chemoreceptors (detect changes in blood pH)
How does the body respond to an increase in blood pressure?
- Baroreceptors send more impulses to cardioinhibitory centre in the medulla oblongata.
- More impulses to SAN down vagus nerve via
parasympathetic nervous system. - slower heart beats
How does the body respond to an increase in CO2 concentration?
- Chemoreceptors detect pH decrease and send more impulses to cardioacceleratory centre of medulla oblongata.
- impulses to SAN via sympathetic nervous system.
- Heart rate increases, so rate of blood flow to lungs increases= rate of gas exchange and ventilation rate increase.
Describe the structure of a neuromuscular junction
Synaptic cleft between a presynaptic motor neuron and a skeletal muscle cell.
How do the 3 muscle types contract
- Cardiac; myogenic, continously uniform
- skeletal; voluntary, quick & strong contractions
- Smooth; involuntary, slowly & regularly
What is role of Atp in contraction
- When myosin bind to actin and moves ADP+Pi released
- New ATP joins Myosin, breaking cross bridge
- New Atp hydrolysed so myosin can swing to new actins
Whats tropomyosins function?
Tropomyosin covers actin binding site
Whats the fucntion of troponin?
troponin bound to actin & tropomysin, with free polypeptide chain,
when calcium binds it causes the troponin to move the tropmyosin, exposing Actin binding site
