Unit 5 - Plant & Animal Responses Flashcards
Nastic responses
Plant responses in which the direction of the plant response is independent of the stimulus
Herbivory
Consumption of plants
Abiotic
Physical
Tropisms
Directional growth responses in plants
Phototropisms
Influenced by light e.g. plants grow towards light to photosynthesise due to auxin moving unilaterally
Geotropism
Influenced by gravity
Plants recieve unilateral gravitational stimulus (downwards)
Shoots are -vely geotropic and roots are +vely geotropic
Thigmotropism
Influenced by touch
Shoots of climbing plants e.g. ivy winding around other plants or solid structures for support
Chemotropism
Influenced by chemicals
Pollen tubes grow down the style of a plant towards the ovary where fertilisation takes place
Plant hormones
Cytokinins Abscisic acid (ABA) Auxins Giberellins Ethene
Effects of cytokinins
Promote cell divison
Delay leaf senescence - increases shelf life
Overcome apical dominance - lateral growth
Promote cell expansion
ABA
Inhibit seed germination and growth
Stimulate cold protective responses
Cause stomatal closure when the plant is stressed by low water availability
Effect of auxins
Promote cell elongation in roots - low conc
Promote shoot growth/ demote root growth - high conc
Inhibit growth of side shoots
Inhibit leaf abscission
Selective weedkiller
Promote cell division in cambium
Effect of gibberellins
Promote seed germination - break bud dormancy (works against ABA)
Promote growth of stems - elongation of internodes
Develop seedless fruit and fruit setting
Acts synergistically w/ auxin
Effect of ethene
Promote fruit ripening - starch to sugar and breaks down chlorophyll and cell wall
Stimulates cells in abscission zone to expand and breaks cell wall causing leaf to fall off
Opp to auxin
How do plants avoid herbivores
Tannins - phenolic compounds; toxic to herbivores and microorganisms
Alkaloids - make plants taste bitter
Mimosa leaves fold up in response to touch - scares insects
Abscission in deciduous plants
Decreases production of auxin
More sensitive to ethene
Gene expression of enzymes in abcission zone
Cellulase breaks down cell walls in separation layer of abscission zone
Vascular bundles sealed off, fatty materials for neat, waterproof scar
Mechanism of seed germination
Seed absorbs H2O and activates embryo
Begins to produce gibberellins
Gene expression –> produces amylases and proteases to break down starch food stores
Glucose is used as a respiratory substrate and in protein synthesis
Mechanism of stomatal closure
Levels of soil water falls Roots produce ABA Transported and binds to guard cells Increases pH, charged particles move out Increases wp, water moves out Loss of turgor closes stoma
Proof of gibberellins causing seed germination
Mutant varieties that lack gibberellin do not germinate but w/ external gibberellin they do
When gibberellin inhibitors are addeed to normal seeds they dont grow
Apical Dominance Effect
Auxin produced at the apex, inhibits growth of lateral buds
Experimental evidence for apical dominance
Removal of apical buds allows lateral bud to grow
Auxin/synthetic auxin placed on cut tip continues to inhibit the growth of side shoots
Plant 30 plants of same type, age, genotype and weight in same soil
Remove tip of 10 and apply auxin paste
Remove tip of another 10 and add paste w/out auxin
Leave last 10 as control
Sig. increase of no. of side shoots grown in first 10
Recent research on apical dominance
Auxin stimulates production of ABA (inhibits growth)
When apex is removed as is the source of auxin, ABA levels decrease
Most cytokinins go to tip so when tip is removed cytokinins spread evenly around plant promoting growth
Where does growth occur in plants
Apical meristems
Lateral bud meristems
Mechanism of cell elongation by auxin
Tip produces auxins, diffuses down Promotes active transport of H+ into cell walls Lowers pH, optimum pH for expansins Breaks H bonds within cellulose Reduces rigidity and H2O enters
Confirming auxin as the hormone that causes growth
Impregnated agar blocks w/ diff conc. of auxin
Placed them on cut shoot tips
Same effects as in reg. shoots
Curvature is directly proportional to conc of auxin used
Research supporting geotropism in shoots
Plants are grown on a slowly rotating drum (clinostat) so gravitational stimulus is applied evenly
Plants grow straight in both light and dark
Research supporting geotropism in roots
Seeds are placed in petri dishes w/ moist cotton wool that are rotated 90 degrees as seedlings grow
Cover lid w/ oil - ensure no light is coming in
All petri dishes should be in same environment
Geotropic response in the roots can be seen every 2 hours
Investigating role of gibberellin in stem elongation
Plant 40 plants
Water 20 plants normally
Water other 20 w/ diluted solution of gibberellins
Let all 40 grow for 28 days, measuring height every 7
Calculate rate at which plants grew
IAA
Natural form of auxin responsible for +ve phototropism so plant bends towards light to phostosynthesise and grow taller and grows roots to reach water and nutrients
Light stimulus detected by tip of plant
Central nervous system
Brain and spinal cord
Mostly relay neurones in brain
Mostly non-myelinated in brain and myelinated in spinal cord
Role of peripheral nervous system
Ensure rapid comm between the sensory receptors, CNS and effectors
Divisions of PNS
Sensory nerous systems
Motor nervous system
Sensory nervous system
Neurons conduct action potentials from the sensory receptor into the CNS
Divisions of motor nervous system
Autonomic
Somatic
Somatic nervous system
Motor neurones that conduct action potentials to effectors that are under voluntary control e.g. skeletal muscles
Mostly myelinated neurones
One single motor neuone connecting CNS to effector
Autonomic nervous system
Motor neurones that conduct action potentials to effectors that arent under voluntary control e.g. cardiac muscles
Mostly unmyelinated neurones
At least two motor neurones involved - connected at ganglia
Divisions of autonomic nervous system
Sympathetic
Parasympathetic
Ganglia in sympathetic system
Outside CNS, near spinal cord
Ganglia in parasympathetic system
Closer to effector tissue
Neurones in sympathetic system
Short pre-ganglionic neurones
Long post-ganglionic neurones
Neurones in parasympathetic system
Long pre-ganglionic neurones
Short post-ganglionic neurones
Neurotransmitter in sympathetic system
Noradrenaline
Neurotransmitter in parasympathetic system
Acetylcholine
Four sections of the brain
Cerebrum
Cerebellum
Medulla Oblongata
Hypothalamus and pituitary complex
Cerebrum
Largest part of human brain
Two hemispheres connected by corpus callosum
Involved in control of speech and higher thought processes e.g. planning a task
Cerebral cortex
Highly folded
Outer part of cerebrum
Involved in higher thought e.g. overriding reflexes, conscious thought, intelligence and reasoning
What is the cerebral cortex divided into
Sensory areas - recieve impulses from sensory neurones
Motor areas - send impulses out to effectors
Association areas - link info and coordinate approriate respnse
Cerebellum
Controls muscular movement and balance
Connected to cerebrum by pons
Coordination of posture
Medulla oblongata
Controls involuntary processes e.g. heart rate and breathing rate
Has specialised centres that recieve info from internal receptors and adjust breathing and heart rate accordingly
Hypothalamus and pituitary complex
Organises homeostatic responses and controls various physiological processes
Info is recieved from hypothalamus and hormones are released via the pituitary gland (controls endocrine system)
Reflex reactions
Responds to changes in the environment but not involving the brain
Sensory –> relay –> motor
Brain may be informed but doesn’t coordinate
Survival; fast, involuntary and not learned (innate)
Cranial reflex
Nervous pathway passes through the brain
What makes something an reflex arc
Receptor and effector in same place
Blinking reflex
Cranial reflex
Corneal - object toucing eyes
Optical - Light hitting back of eye (retina)
Patnway for corneal blinking reflex
Receptor
Sensory neurone on cornea
Sensory centre on pons
Non-myelinated relay neuron passes action potential to motor neurone
Motor neurone passes out of brain to facial muscles
If the corneal blinking reflex is to be overridden
Sensory neurone on cornea
Myelinated relay neurones inform brain
Allows reflex to be overriden (inhibitory neurone) - faster so reflex can be overriden before it happens
Knee-jerk reflex
Spinal reflex
Unexpected stretching of quadraceps –> detected by muscle spindles –> causes a reflex reaction (no relay neurone) –> quadraceps contract
Spinal reflex
Involves the spinal chord rather than the brain
Muscle spindles
Stretch receptors that detect increase in muscle length
Class of hormones
Steroid - produced in reproductive organs and adrenal cortex
Peptide - insulin, ADH, adrenaline
Hypothalamic - anterior axis
Hypothalamus releases hormones (releasing factors)
Pass down a portal vessel to anterior pituitary gland
Anterior pituitary gland releases tropic hormones e.g. for thyroid and adrenal
Tropic hormones
These stimulate other endocrine glands
Mechanism of steroid hormones
Steroid hormone combines w/ steriod receptor in cytoplasm
Hormone-receptor complex enters nucleus
Complex binds to receptor sites on DNA, activating mRNA transcription
mRNA leaves nucleus
Ribosome translates mRNA into new protein in cytoplasm
Mechanism of peptide hormones
Adrenaline in the blood binds to membrane bound receptor
Stimulates G-protein to activate Adenyl cyclase
Converts ATP to cAMP
cAMP acts as second messenger by moving into the cell cytoplasm and causing an effect
Thyroxin
Increases metabolic rate in most cells
How is thryoxin released
Hypothalamus releases TRH
Travels to anterior pituitary gland and releases TSH
Travels to thyroid through portal vessel and releases thyroxine
TRH
Thyrotropin releasing hormone
TSH
Thyroid stimulating hormone
How are glucocorticoids (cortisol) released
Hypothalamus releases CRH
Travels to anterior pituitary gland and releases ACTH
Travels to adrenal cortex through portal vessel and releases cortisol
Cortisol
Released as a response to chronic stress
Stimlates breakdoen of glycogen
Coordination of flight or fight
Sensory input
Action potential travels to sensory centres (cerebrum)
Signals passed to association areas
If a threat is recognised, cerebrum stimulates hypothalamus
Hypothalamus stimulates symapthetic nervous system and stimulates release of hormones from anterior pituitary gland
How is the fight or flight response formed
Hypothalamus activates sympathetic nervous system
Impulses activate glands and smooth muscle
Activated adrenal medulla
Secretion of adrenaline into the bloodstream
Hypothalamus also secretes releasing factors e.g. CRH and TRH
CRH
Corticotropic releasing hormone
ACTH
Adrenocorticotropic hormone
Physiological changes in fight or flight response
Pupils dilate - more light enters eyes, retina becomes more sensitive
Heart rate and bp increase
Ventilation depth and rate increases
Less digestion
Blood glucose increases
Metabolic rate increase - faster coversion of glucose to ATP
Endorphins released in brain
Erector pili muscles in the skin contract
Why do erector pili muscles stand up in fight or flight response
Hairs/ fur stands up - signs of aggression
Why are endorphins released in the fight or flight response
Wounds inflicted don’t prevent activity
Why must plants be able to respond to their environment
Cope w/ changing conditions
Avoid antibiotic stress
How does auxin cause cell elongation (2 marks)
Loosens rigid cellulose framework
Osmotic uptake of water allows cell elongation
Why do cut plants w/ agar blocks w/ auxin placed on the rhs bend to the lhs
Auxin produced at tip
Diffuses laterally to rhs
Cells on rhs exhibit greater elongation
Bending to the left
How does auxin act as a selective weedkiller
Rapid cell elongation so plant grows too quickly
No extra lignified tissue
Stem collapses or loss of extra water from leaves
What happens when the apex is removed from a plant
Once apex is removed, auxin production stops
Apical dominance is stopped
Lateral growth is not inhibited and lateral buds develop
Types of muscle
Skeletal (voluntary)
Cardiac
Involuntary (smooth)
Voluntary (skeletal muscle)
Striated Multinucleate Regularly arranged —> contraction in one direction Attached to bone by tendon Tubular Nerves from peripheral, somatic (rapid)
Cardiac muscle
Specialised striated (parallel myofibrils)
Branched fibres
Uninucleated
Cross bridges allow simultaneous contraction
Dark bands - intercalated discs
Nerves from autonomic nervous system
Involuntary (smooth muscle)
Non striated
Nerves from autonomic nervous system
No reg. arrangement - diff cells can contract in diff directions
Fibres are spindle shaped and uninucleated
Used in hollow organs (peristalsis)
Sarcolemma
Plasma membrane that encloses bundles of muscle fibre
Why may the sarcolemma fold in
Spread impulse throughout sarcoplasm
Contract at the same time
Sarcoplasm
Shared cytoplasm within muscle fibres
How are muscle fibres formed
Fusion of several embryonic muscle cells - gap between adjacent cells would be a weakness
(That’s why it’s multinucleate)
Sarcoplasmic reticulum
Modified version of ER
Provides strength and stored Ca^2+
Protein filaments
Myosin
Actin
Muscle organisation
Muscle Fascicles Muscle fibres Myofibrils Protein filaments
Connective tissue
Tendons
Light band (I)
Thin actin held together by Z line
Dark band (A)
Both actin and myosin
Entire length of myosin
Myosin held together by M line
M line
Midpoint of myosin
Has no heads
Z line
Found at the centre of each light band
Sarcomere
Functional unit of muscle
From one Z line to another
Sub unit of myofibrils
Why is muscle considered a tissue
Muscle fibre
Blood vessels
Nerves
Connective cells
Characteristics of sliding filament model
Z lines get closer
Sarcomeres shortens
I band narrows
H zone narrows
What does simultaneous contraction of several sarcomeres allow
Myofibrils and then muscle fibres to contract —-> enough to pull a bone
Neuromuscular junction
Action potential arriving at axon of motor neurone opens VG Ca2+ to flood into tip
Vesicles of acetylcholine to move towards membrane & fuse
Acetylcholine diffuses across synapse and binds to receptors on sarcolemma
Na+ channels open and wave of depolarisation passes down transverse tubules
Passes to SR which releases Ca2+ into the sarcoplasm
Cross bridge muscle contraction cycle
Tropomyosin is blocking myosin binding site in actin
Ca2+ binds to troponin causing a conformational change, tropomyosin moves
Myosin heads bind to actin, forming cross bridges between filaments
Myosin heads move, pulling the actin filament. ADP and Pi are released during the power strike
A new ATP molecule attaches to myosin head, breaking cross bridge
ATP hydrolyses and myosin head returns to its orig. position
Where does SR get Ca^2+
Active absorption from sarcoplasm
Supply of ATP for muscular contraction
Aerobic respiration - oxidative phosphorylation
Anaerobic respiration - glycolysis
Glycogen —> glucose
Creatine phosphate can combine w/ ADP to form ATP
Where is creatine phosphate found
Sarcoplasm
Supply of energy of slow twitch muscle
Aerobic respiration
Supply of energy for fast twitch muscle
Anaerobic respiration
Where is the cardiovascular centre
Medulla oblongata - this alters the excitation wave frequency
Frequency of heart excitation
60-80 bpm
What is the heart rate regulated by
SAN
Nerves connect cardiovascular centre to the SAN
Nerves involved in controlling heart rate
Accelerans
Vagus
Accelerans
Causes release of noradrenaline at SAN Increases HR (sympathetic)
Vagus nerves
Causes release of acetylcholine at SAN, reduces HR (parasympathetic)
Sensory inputs that increase HR
Increased muscle movement (muscle stretch receptors)
Decrease in pH (chemoreceptors)
Adrenaline in blood
Sensory inputs that decrease HR
Increase in bp (stretch receptors - carotid sinus)
Decrease in dissolved CO2 (chemoreceptors)
Why do plants kept in the dark grow taller than those in the light
Auxin is more present in the dark
Plant growth substances vs animal hormones
Hormones travel faster in animals
Synthesised in endocrine glands vs cells sites
Slow acting in plants vs fast acting in animals
Why is temp controlled in investigations on effect of plant hormones
So temp does not affect results as temp affects enzyme activity
Why are monkeys used for human research
Closely related
Both primates
Similar physiology
Actions of parasympathetic nervous system
Increases blood flow to digestive system, allows peristalsis Decreases HR Decreases airway diameter Sexual arousal Constricts pupils
Why is glycogen found in striated muscle
Glycogenolysis
Glucose can undergo glycolysis to produce ATP
Energy storage
Uses of mitochondria in muscular contraction
ATP attaches to ATPase on the myosin head
Hydrolysis to release ADP and Pi during power stroke, allows myosin heads pull the actin filaments
Needed for myosin head to detach
Protein synthesis
Ca 2+ pumps in SR
Internal organs affected by SNS/PNS
Heart
Lungs
Liver
Intestines
How is the heart affected in the PNS/SNS
Slow HR vs. fast HR
How are the lungs affected by the PNS/SNS
Shallow breaths vs deep breaths
How is the liver affected by the PNS/SNS
Glucose take up (glycogenesis) vs glucose used up (glycolysis)
How is the stomach affected by the PNS/SNS
More peristalsis vs. less
How does the SNS affect smooth muscle
Alters blood flow to increase bp Vasoconstriction Peristalsis slows down Relaxes in airways (increases diameter) Pupils dilate
How does the SNS affect cardiac muscle
Heart beats faster
Beats w/ more force
How does SNS affect voluntary muscles
Glycogenolysis in muscles for priming
Diaphragm contracting faster
More blood flow to skeletal muscle –> respiration
Long term effects of chronic stress
Cardiovascular problems due to high bp
Suppression of immune system leads to susceptibility to disease
Photoperiodism
Plants’ sensitivity to a lack of light, affects several diff plant responses e.g. flowering
Phytochrome
Light sensitive pigment that affects the sensitivity of plants to light
Exists in two forms, Pt and Pft
How do plants prevent freezing
Cytoplasm and vacuole contain sap that lowers the freezing point
Produce biological molecules (excluding lipids) to prevent cytoplasm freezing or protect cells from damage if they do freeze
Commercial uses of plant hormones
Ethene to control ripeneing Hormone rooting powders and micropropagation Auxin to produce seedless fruit Cytokinins to prevent aging Gibberellins to improve size and shape
Transverse tubules
Extensions into sarcolemma
Factors affecting stomatal closure
Temperature
Water availability
How does increases in temp affect stomata
Release of ABA decreases
Stomata open
Allows plant to cool through water evaporation
How does decrease in water availability affect stomatal
Increased release of ABA
Stomata close
Reduces water loss through transpiration
How do gibberellins cause stem elongation
Promote cell elongation - by loosening cell walls
Promote cell division - producing proteins that control the cell cycle
