5.5 Plant And Animal Responses Flashcards
What is a reflex action?
Response to stimulus that doesn’t involve the brain to coordinate movement, always with a survival value
Explain the blinking reflex - what type of reflex is it? What occurs?
- uses brain but without higher thought processes: CRANIAL
- stimulus, then sensory neurone from cornea carries impulses to sensory centre in pons, which travels through non-myelinated relay neurone to motor centre in pons, and via motor neurone to facial muscles which usually causes both eyes to blink
Describe how the knee jerk reflex works
Coordinated movement and balance
Stimulus - stretching of the quadriceps muscle caused by pressure on the ligament
Receptor - stretch receptors in the quadriceps muscle
Coordinator - the spinal cord
Effector - the quadriceps muscle
Response - contraction of the quadriceps muscle, causing the leg to straighten
Sensory -> motor ( bypasses relay)
What physiological changes occur when adrenaline is released?
- Pupils dilate so more light enters
- Heart rate and blood pressure increases so more oxygen and glucose reaches muscles
- Arterioles to digestive system constricted, to divert blood to muscles
- Blood glucose increases = more energy for muscle contraction
- Erector pills muscles contract = hairs stand up
- Ventilation rate increases to increase gaseous exchange
- Endorphins released = natural painkillers so wounds inflicted do not prevent activity
Describe the pathway of nervous coordination of the fight or flight response
Inputs into cerebrum sensory centres -> signals to association centres -> hypothalamus stimulated -> activates sympathetic nervous system -> activate glands and smooth muscles or activates adrenal medulla to secrete adrenaline into bloodstream. Neuronal activity combines with hormones to constitute fight or flight response.
Describe the pathway of endocrine communication in the fight or flight response
hypothalamus stimulated to secrete hormones into blood which pass down portal vessel to stimulate anterior pituitary gland to release tropic hormones
CRH -> ACTH released from pit -> adrenal cortex secretes corticoids e.g. cortisol to regulate metabolism of carb -> bloodstream
TRH -> TSH released from pit -> thyroid glands secretes thyroxine to increase metabolic rate and make cells more sensitive to adrenaline -> bloodstream
Neuronal activity and hormones combine to carry out response
Describe adrenaline action once it reaches a cell
- Binds to plasma membrane receptor, stimulating G protein to active adenyl cyclase
- Converts ATP to cAMP (second messenger)
- Activates enzyme action
How is heart action modified?
Changing heart rate
Altering force of contractions
Altering stroke volume
What does myogenic mean?
Can initiate its own beat at regular intervals
What do sensory inputs to the cardiovascular centre include?
- Stretch receptors in muscles that detect movement of limbs -> more oxygen needed -> inc heart rate
- Chemoreceptors in carotid arteries, aorta and brain monitor blood pH. If too low, APS sent to centre and inc heart rate
- Baroreceptors in carotid sinus monitor blood pressure. Pressure too high = send APs to centre = dec heart rate
What is the solution if the mechanism controlling the heart fails? E.g. fibrillation occurs
Artificial pacemaker delivered, connected to SAN or to ventricle muscle directly, delivering electrical impulse to heart muscle.
What are some features of smooth muscle?
one nucleus per cell
contracts slowly and regularly
tubular structures : blood vessels, digestive system
circular layer -> segmentation in intestine (spindle shaped)
longitudinal -> wave like contractions (circle cells)
involuntary
What are some features of cardiac muscle?
cells -> long fibres -> branch to form cross bridges between fibres to ensure stimulation spreads evenly
intercalated discs - specialised cell surface membranes fused to produce gap junctions -> allow free ion diffusion
appears striated under microscope
involuntary
What are some features of skeletal muscle?
joints in skeleton
antagonistic pairs
each fibre is multinucleate and surrounded by sarcolemma membrane, and with sarcoplasm and sarcoplasmic reticulum
myofibrils divided into functional subunits called sarcomeres (actin and myosin)
striated appearance
contracts quickly and powerfully
voluntary
Describe the process that occurs at a neuromuscular junction
- APs at end of axon open calcium channels; they enter
- Acetylcholine vesicles move towards membrane and fuse
- Diffuse across gap and bind to receptors
- Sodium channels open and delopolarisation occurs
- Wave of depolarisation passes along sarcolemma and down transverse tubules
What is a motor unit?
muscle fibres contract together (many motor neurones divide and connect to several muscle fibres)
What is the light and dark band?
light: thin filaments, actin
dark: thick filaments, myosin
Describe the structure of actin filaments
two chains of subunits wound around eachother
troponin complexes
tropomyosin wrapped around
Describe the structure of myosin filaments
thick filament, with heads. each molecule has 2 heads
What is the A band, I band and H zone?
A band: between points they overlap
I band: only actin
H zone: only myosin
What happens to sarcomeres during contraction?
- thick and thin filaments slide past one another. H zone gets smaller, Z lines more closer, sarcomere gets shorter. Filaments do NOT change in length. Little/no I band also
How is contraction controlled?
- AP passes along sarcolemma and into muscle fibre
- AP carried to sarcoplasmic reticulum, and causes calcium ion release into sarcoplasm
- Calcium ions bind to troponin, altering shape and pulling it aside (exposes actin binding sites)
- Myosin heads bind to actin = cross bridges form
- Myosin heads move, pulling actin filament past
- Myosin heads detach and can bind again further up
What is the role of ATP in muscle contraction?
- Myosin head attaches to actin
- Power stroke occurs, ADP and Pi are released (part of myosin head acts as ATPase)
- New ATP attaches to myosin head, breaking cross bridge
- Myosin head returns to position as ATP is hydrolysed, releasing energy.
How is ATP supply maintained?
- Aerobic respiration in many mitochondria. But, during intense activity it is less than demand
- Anaerobic respiration but toxic lactic acid is produced
- CREATINE PHOSPHATE: phosphate can be transferred to ADP molecules.
What is the function and structure of the cerebrum?
2 cerebral hemispheres connected via corpus callosum
outermost layer consists of thin nerve cell body layer = cerebral cortex
higher thought processes, emotions, conscious actions, intelligence, decisions, memory
What are the 3 different areas of the cerebral cortex?
sensory areas: receive APs from sensory receptors. The size of regions receiving inputs are related to the sensitivity of area that those inputs are recieved from.
association areas: compare sensory inputs with previous experience and interpret what it means
motor areas: send APs to various effectors. size of regions related to complexity of movements needed in their allocated effectors.
What is the function and structure of the cerebellum?
- balance and fine movements
- connected to cerebrum by pons
- info from sensory receptors
-neurones conduct APs to motor areas
maintaining body position and balance, judging position of objects, tensing muscles, coordination of antagonistic skeletal muscles
- requires learning and complex pathways are strengthened by practice
What is the general function of hypothalamus? Whats special about it?
homeostatic mechanisms
own sensory receptors
What is the general function and structure of the pituitary gland?
posterior: ADH made in the hypothalamus, passes down neurosecretory cells and released there.
anterior: produces its own hormones and released in response to releasing factors
control many processes/homeostatic mechanisms also
What is the general function and structure of the medulla oblongata?What 3 different centres does it have?
- controls non skeletal muscles via APs through autonomic nervous system
- cardiac centre: heart rate
- vasomotor centre: blood pressure
- respiratory centre: breathing rate
How is the CNS divided?
brain: relay neurones (non-myelinated), grey matter
spinal cord: grey and white (myelinated) matter. Protected by vertebral column. Between each vertebrae, peripheral nerves enter and leave to carry APs to and from rest of body.
How is the PNS divided?
sensory and motor system
motor system divided into somatic and autonomic (autonomic has sensory elements too)
Explain in more detail what the peripheral system involves - nerves doing what? What is the difference between motor and sensory?
sensory and motor nerves connecting sensory receptors and effectors to CNS
sensory: conduct APs from sensory receptors into CNS. Cell body in ganglia in DORSAL root leading into spinal cord, and short axon connecting to other neurones in CNS.
motor: conduct APs from CNS to effectors
What is the difference between somatic and autonomic?
SOMATIC: conduct APs under voluntary control e.g. skeletal muscles. myelinated neurones. 1 SINGLE MOTOR NEURONE from CNS to effector
AUTONOMIC: conduct APs not under voluntary control e.g. glands, smooth and cardiac muscle, airways etc. Mostly non-myelinated. At least have TWO MOTOR NEURONES connected at ganglia ( and sensory too).
How can autonomic further be divided?
- sympathetic (prepares body for activity)
- parasympathetic (conserves energy)
these are antagonistic and at rest APs travel at low freq in both.
What are the differences between sympathetic and parasympathetic?
SYM: many nerves each leading to separate effectors
PARA: few nerves divide up and lead to diff effectors
SYM: ganglia outside CNS
PARA: ganglia in effector
SYM: short pre-ganglionic neurones
PARA: long pre-ganglionic neurones
SYM: noradrenaline
PARA: acetylcholine
SYM: increases heart rate, dilates pupils, decreases digestive activity
PARA: decreases heart rate, constricts pupils, increases digestive activity.
what 3 ways do plants use to defend against herbivory?
tannins: toxic to insects and bitter tasting to deter large animals. prevent infiltration by pathogenic microorganisms in roots
alkaloids: bitter nitrogenous compounds, often poisonous
pheromones: chemicals released by an individual which can affect behaviour/ physiology of another
How do plants defend against high temp, low temp, drought and wind?
high: thicker wax layer deposited
low: AFP’s produced to decrease crystal formation
windy: vascular tissue more heavily lignified
drought: close stomata to reduce transpiration and increase abscission
What is tropism vs nastic responses?
tropism = directional growth
nastic = non directional response
positive is towards, negative is away
What are the advantages/ purposes of:
- phototropism
- geotropism
- chemotropism
- thigmotropsim
- thigmonastic
- shoots positively phototropic, so more LDR occurs
- roots positively geotropic -> anchor in soil and increase uptake of mineral ions and water
- on a flower, pollen tubes grow down style towards ovary
- shoots of climbing plants wind around structures for support and greater light access
- mimosa pudica responses to touch with sudden leaf folding
Whats the role of auxins?
cell elongation, inhibit growth of side shoots, inhibit leaf abscission
Whats the role of cytokinins?
cell division, delay leaf senescence, overcome apical dominance, cell expansion
What is the role of abscisic acid?
inhibits seed germination and growth, causes stomatal closure
What is the role of gibberellins?
promote seed germination and stem elongation
What is the role of ethene?
fruit ripening
Leaf drop
How do hormones move in plants?
mass flow in vessels, diffusion or active transport
What is the evidence for seed germination by gibberellins?
- seed absorbs water, embryo releases gibberellin which travels to aleurone layer in endosperm region of seed
- enables amylase production. starch -> glucose used in respiration of embryo
If you break off the shoot tip (——-), the plant starts to grow from ———–
Suggested auxins in ———– —— lateral buds from growing ( tip removed = auxin —— and buds grow)
apical bud
lateral buds
apical bud prevents
decreases
What are the 3 types of meristem?
- apical meristem at tips
- lateral meristems as cylinders around edge of shoots and roots responsible for width
- intercalary meristems between nodes
How would you investigate phototropism and what results would you expect?
- experimental: light on one side
- control: light on all sides
- both shoots and roots marked every 2mm at the start
- moist cotton wool plug used
- would expect shady side of experimental plant to be elongated more and therefore that plant bends towards the light
How would you investigate geotropism and what results would you expect?
- experimental plant: no klinostat -> root bends downwards as upper side elongated more
- control plant: klinostat so gravity applied equally to all sides -> roots and shoots grow horizontally
What is the mechanism of auxins effect in shoots?
SHOOTS:
- produced at apex and travels to cells in zone of elongation = shoot grows
- light shining on one side causes auxins to be transported to shaded side = elongation there.
-extent to which cells elongate is proportional to auxin con
- promotes active transport of H+ by ATPase enzyme on plasma membrane, into cell walls = low pH = expansins work
- these enzymes break bonds within cellulose so walls become less rigid
What do auxins do in roots?
- accumulate on lower side of roots and inhibits cell elongation= bends downwards
What are the commercial uses of auxins?
- promote flowering
- inhibit leaf/fruit drop
- rooting powders
- treating unpollinated flowers can promote seedless fruit growth
- weed killers since they promote root growth too much
What are the commercial uses of cytokinins?
- prevent yellowing of lettuce leaves
- tissue culture to help mass-produce plants
What are the commercial uses of gibberellins?
- delay senescence in citrus fruits
- can make apples and grape stalks elongate
- can speed up amylase production for brewing (turning starch into maltose)
- stimulates internodal growth of sugar cane
- induce seed formation in young trees to speed up breeding
What are the commercial uses of ethene?
- speed up fruit ripening in citrus, apples and tomatoes
- promoting fruit drop in cotton and walnut
- promoting female sex expression in cucumbers reducing chance of self pollination
- promoting lateral growth in some plants
- or can RESTRICT ethene so fruits can be stored for longer
Suggest why a lack of ATP leads to muscle rigidity
- ATP required to break cross bridges
- actin and myosin filaments remain cross linked
- muscle remains contracted
Describe the different sources of ATP that is used in muscle during strenuous exercise
Sources:
- free in sarcoplasm
- creatine phosphate
- runs out in a few seconds/ quickly
Aerobic respiration:
- if oxygen available
- oxidative phosphorylation
- greater yield of ATP
- but O2 doesnt meet demand as it’s limited during strenuous exercise
Anaerobic respiration:
-needed during strenous exercise
- only involves glycolysis
- ATP formed by substrate level phosphorylation
- net yield of 2 ATP
- NAD regenerated so glycolysis can continue
- cannot continue forever due to lactic acid build up
