5.5 Flashcards
What are tannins
phenolic compounds, located in cell vacuoles or in surface wax on plants - toxic to microorganisms and larger herbivores
what are alkaloids
organic nitrogen-containing bases that have important physiological effect on animals
what are pheromones
any chemical released by 1 living thing which influences the behaviour or physiology of another living thing
what is geotropism
a directional growth response, made by plants, to gravity
what is chemotropism
a directional growth response, in plants, to chemicals
what is phototropism
a directional growth response, made by plants, to light
what is thigmotropism
a directional growth response, in plants, to the stimulation of touch
role of cytokinins
- promote cell division
- delay leaf senescence (go yellow/brown)
- overcome apical dominance
- promote cell expansion
role of abscisic acid
- inhibits seed growth+germination
- causes stomatal closure when plant is stresses by low water availability
role of auxins
- promote cell elongation
- inhibit growth of side-shoots
- inhibit leaf abscission (leaf falls)
role of gibberellins
-promote seed germination +growth of stems
role of ethene
promotes fruit ripening
experimental evidence for role of gibberellins
- found by comparing GA₁ concentration in tall+short pea plants
- tall plants higher concentration
- tall genotypes (Le Le) can process GA₁ from GA₂₀ so plants grow taller
- dwarf genotype (le le) do not produce enzyme that creates GA₁ (gibberellins) from GA₂₀ so are short as do not produce gibberellins
commercial uses of auxins
- rooting powder
- seedless fruit
- herbicides (weed killers)
commercial uses of cytokinins
- prevents yellowing of lettuce
- helps mass-produce plants
commercial uses of gibberellins
- fruit production (delays senescence)
- brewing (speeds things up)
- sugar production (makes more sugar (stem elongates))
- plant breeding (induces seed formation on young conifer trees)
commercial uses of ethene
- speeds up fruit ripening
- promotes fruit drop
- storing fruit at low temps stops ethene synthesis (fruits stored for longer)
- silver salts also inhibit ethene synthesis
- promotes lateral growth (compact flowering stems)
- promotes female sex expression in cucumbers 🥒 (ensures they aren’t bitter + increases yield)
what is the peripheral nervous system (PNS)
the sensory and motor nerves connecting the sensory receptors and effectors to the CNS
-divided into sensory system and motor system
what is the central nervous system (CNS)
the central part of the nervous system composed of the brain and spinal cord
-divided into brain and spinal cord
what is the motor system
the motor system conducts action potentials from the CNS to the effectors.
-divided into somatic nervous system and autonomic nervous system
what is the somatic nervous system
the motor neurones under conscious control, such as the skeletal muscles
-conduct action potentials from the CNS to the effectors that are under voluntary (conscious) control, neurones are mostly myelinated so that responses can be rapid
what is the autonomic nervous system
consists of motor neurones that conduct action potentials from the CNS to effectors that are not under voluntary control e.g. cardiac muscle
-neurones mostly non myelinated as responses do not need to be rapid
what is the sympathetic system + effects include
part of autonomic nervous system that prepares the body for activity
- increases HR
- dilates pupils
- increased ventilation rate
- reduced digestive activity
- orgasm
what is the parasympathetic system + effects include
part of the autonomic system that regulated physiological functions when the body is at rest
- decreases HR
- constricts pupils
- reduces ventilation rate
- increases digestive activity
- sexual arousal
what are the different parts of the human brain
cerebrum cerebellum hypothalamus and pituitary complex medulla oblongata skull corpus callosum pons spinal cord
what does the cerebrum do
- largest part and organises most of our higher thought processes, such as conscious thought and memory
- divided into 2 central hemispheres
what does the cerebellum do
coordinates movement and balance
-receives info from many sensory receptors + processes the info accurately
what does the hypothalamus do
coordinates homeostatic responses
what does the medulla oblongata do
coordinates many of the autonomic response
e.g.
-cardiac centre
-vasomotor centre
-respiratory centre
these centres receive sensory info and coordinate vital functions by negative feedback
what does the pituitary gland do
endocrine gland at the base of the brain, below but attached to the hypothalamus; the anterior lobe secretes many hormones; the posterior lobe stores and releases hormones made in the hypothalamus
what ‘higher brain’ functions does the cerebrum control
- conscious thought
- conscious actions (including the ability to override some reflexes)
- emotional responses
- intelligence, reasoning, judgement, decision making
- factual memory
structure of the cerebrum
-2 central hemispheres, connected via major tracts of
neurones called the corpus callosum.
-the outermost layer of the cerebrum consists of a thin layer of nerves cell bodies called the cerebral cortex
subdivision of the cerebrum
- sensory areas receive action potentials indirectly from the sensory receptors
- association areas compare sensory inputs with previous experience, interpret what the input means and judge and appropriate response
- motor areas send action potentials to various effectors
how are the cerebrum and cerebellum connected
by the pons
examples of homeostatic mechanisms that the hypothalamus controls
- temp regulation, detects change in the core temp, also receives sensory input from temp receptors in the skin
- osmoregulation, contains osmoreceptors that monitor the water potential in the blood, responses are mediated by the hormonal system via the pituitary gland
what is the knee jerk reflex
a reflex action that straightens the leg when the tendon below the knee cap is tapped
-spinal reflex, nervous pathway passes through the spinal cord rather than through the brain
what is the blinking reflex
-reflex is a cranial reflex as the nervous pathway passes through part of the brain
-reflex arc
can be stimulated by:
a foreign object touching the eye
loud sounds
sudden bright light
sudden movements close to the eye
survival value of reflexes
- used to get out of danger
- avoid damage to part of the body
- maintain balance
fight or flight response
- pupils dilate (more light)
- HR + BP increase (more O2 & glucose to muscles)
- blood glucose levels + metabolic rate increase (more energy)
- endorphins (natural painkillers) released in brain
- ventilation rate+depth increase
- erector pili muscles in skin contract makes hairs stand on end
- blood is diverted from skin&gut to heart, lungs + skeletal muscles as certain arterioles constrict whilst other dilate
coordination of the fight or flight response
- inputs feed into the sensory centres in the cerebrum
- the cerebrum passes signals to the association centres
- if a threat is recognised, the cerebrum stimulates the hypothalamus
- the hypothalamus increases activity in the sympathetic nervous system and stimulates the release of hormones from the anterior pituitary gland
mechanism of adrenaline action
- adrenaline binds to adrenaline receptor on plasma membrane. receptor is associated with a G protein which is stimulated to activate the enzyme adenyl cyclase
- adenyl cyclase converts ATP to cyclic AMP (cAMP) ➡️ second messenger inside the cell
- cAMP causes an effect inside the cell activating enzyme action
the release of hormones from the anterior pituitary
hypothalamus secretes releasing hormones into the blood. these pass down a portal vessel to the pituitary gland and stimulate the release of tropic hormones from the anterior part of the pituitary gland. these stimulate activity in a variety of endocrine glands
control of heart rate by the cardiovascular centre
- action potentials sent don a sympathetic nerve (the accelerant nerve) cause the release of the neurotransmitter noradrenaline at the SAN. this increases the HR
- action potential sent down the vagus nerve release the neurotransmitter acetylcholine, which reduces to HR
- (sensory input) stretch receptors in the muscles detect movement of the limbs, these send impulses to the cardiovascular centre, informing it that extra O2 may soon be needed ➡️ leads to an increased HR
how does a low blood pH affect the heart rate
- exercise produces more CO2, some reacts with water in blood plasma to produce carbonic acid, lowering pH of blood
- change detected by chemoreceptors which send action potentials to the cardiovascular centre, which tends to increase the HR
how does conc of CO2 affect HR
- when we stop exercising. the conc of CO2 in blood falls
- reduces the activity of the accelerator pathway, therefore the HR declines
how does blood pressure affect HR
- an increase in bp is detected by stretch receptors in the walls of the carotid sinus
- if bp is too high, the stretch receptors send action potentials to the cardiovascular centre, leading a reduction in HR
cardiac muscle
muscle found in the heart walls
- myogenic
- made of muscle fibres connected by intercalated discs which have low electrical resistance so nerve impulses pass easily between cells
- muscle fibres are branched to allow nerve impulses to spread quickly throughout the whole muscle
- each muscle fibre has 1 nucleus, shaped like cylinders
- contract rhythmically and don’t fatigue
involuntary muscle
smooth muscle that contracts without conscious control
- found in walls of hollow internal organs eg. gut, blood vessels
- each muscle fibre has 1 nucleus + bundles of actin & myosin
- muscle fibres are spindle shaped with pointed ends and
- contract slowly and don’t fatigue
skeletal (striated) muscle
muscle under voluntary control
- made of many muscle fibres that have many nuclei
- some contract quickly, used for speed & strength but fatigue quickly
- some contract slowly and fatigue slowly, used for endurance & posture
- contractions stimulated by the somatic nervous system
neuromuscular junction
the auction between the nervous system and the muscle is called this. it has many similarities to a synapse
stimulation of contraction
- action potentials arriving at the end of the axon open Ca2+ channels in the membrane. Ca2+ floods into the end of the axon
- vesicles of acetylcholine move towards + fuse with the end membrane
- acetylcholine molecules diffuse across the gap and fuse with receptors in the sarcolemma
- this opens Na- channels which allow Na- to enter the muscle fibre causing depolarisation of the sarcolemma
- a wave of depolarisation spreads along the sarcolemma and down transverse tubules into the muscle fibres
structure of skeletal muscle
muscle ➡️ bundle ➡️ fibres (mutinuclei) ➡️ myofibril ➡️ sarcomere ➡️ protein filaments
sliding filament theory
- myosin & actin filaments slide over one another to make the sarcomeres contract
- sarcomeres return to their original lengths as the muscle relaxes
- myosin filaments have globular heads and binding sites
- binding sites in resting muscles are blocked by tropomyosin
ATP in muscle contraction
- action potentials trigger and influx of calcium ions
- Ca2+ binds to troponin
- myosin head binds to the exposed site
- actin-myosin cross-bridge formed - ATP provides the energy needed to move the myosin head and bread the cross bridge, ADP and Pᵢ released, myosin head reattaches to the next binding site
what happens when the muscles stop being stimulated
calcium iOnS leave their binding sites on the troponin molecules, actin filaments slide back, tropomyosin blocks the binding sites again
how is ATP regenerated ?
by aerobic respiration
-only works when theres O2 so good for long periods of low intensity exercise
how is ATP regenerated by anaerobic respiration
-ATP made rapidly, however it produces lactic acid which causes fatigue
how is ATP regenerated by ATP-Creatine Phosphate (CP) System
ADP + CP ➡️ ATP + C(creatine)
- cp is stored inside cells but runs out quickly
- anaerobic + doesn’t form lactic acid
how is ATP regenerated by ATP-Creatine Phosphate (CP) System
ADP + CP ➡️ ATP + C(creatine)
how do neuromuscular junctions work
- they use the neurotransmitter acetylcholine (ACh) which binds to receptors (called nicotinic cholinergic receptors)
- causes depolarisation of the muscle cell causing it to contract (if the threshold level is reached)
- acetylcholinesterase (AChE) stored in post synaptic membrane release to break down acetylcholine after use
