15) Control & Co-ordination Flashcards
1
Q
list 5 key ideas about hormones
A
- proteins or steroids
- released by endocrine glands
- directly into the blood
- act as messengers
- affect target organs/ cells
2
Q
what are 3 peptide hormones
A
- ADH
- insulin
- glucagon
(cell signalling molecules)
3
Q
how do peptide hormones pass through the membrane?
A
- cannot pass through directly
- since they are hydrophilic
- so they bind to receptors in the plasma membrane of a target cell
4
Q
5 differences between the endocrine system and the nervous system
A
Endocrine system
- communication = HORMONE
- nature of communication= chemical
- mode of transmission = blood
- response destination = target organs/cells
- transmission & response speed = slower
- effects = widespread
- duration = longlasting/permanent
Nervous system
- communication = action potential/impulse
- nature of communication= electrical (& chemical)
- mode of transmission = neurone
- response destination = muscle/gland
- transmission & response speed = faster
- effects = specific
- duration = short lived/temporary
5
Q
describe the structure of a motor neurone
A
- cell body at end of neurone
- cell body in CNS
- long axon
- dendrites attached to cell body
6
Q
describe the structure of a sensory neurone
A
- cell body in middle of neurone
- nucleus in cell body
- short axon
- dendrites attached to dendron
- long dendron
- many mitochondria in cell body
- many RER/ribosomes in cell body
- synaptic knobs
- myelin sheath/ schwann cells
- nodes of Ranvier
7
Q
how does the myelin sheath increase the speed of conduction of nerve impulses
A
- it insulates axon
- action potential only at nodes of Ranvier
- local circuits set up between nodes
- action potential jumps from node to node
- saltatory conduction
8
Q
what is a transducer
A
convert energy in one form (light/heat) into electrical energy within a sensory neurone
9
Q
role of chomoreceptor cell in detecting stimuli and stimulating action potential
A
- chemicals act as a stimulus
- specificity of chomoreceptors
- Na+ diffuse into cell via microvilli
- membrane depolarised
- receptor potential
- stimulates opening of Ca+ channels
- Ca+ enter the cell
- vesicles with neurotransmitter move/fuse
- neurotransmitter released by exocytosis
- neurotransmitter stimulates action potential
10
Q
How is a resting potential set up and maintained in a myelinated neurone [9]
A
- Na+ moves out of the cell and K+ moves into the cell. by active transport.
- 3 Na+ for every 2 K+.
- sodium potassium pump.
- against concentration gradient
- K+ diffuses out of cell & Na+ diffuses into.
- by facilitated diffusion.
- membrane more permeable to K+ so more K+ goes out than Na+ in.
- inside of the cell is more negative than the outside
- membrane polarised
- resting potential = -70mV
11
Q
describe the transmission of an action potential in a myelinated neurone [9]
A
- stimulus occurs
- Na+ channels open
- Na+ enters the cell
- causes depolarisation as inside of the cell becomes less negative
- Na+ channels close
- K+ channels open
- K+ moves out of the cell
- repolarisation = inside becomes negative
- local circuits
- myelin sheath insulate axon
- action potential ONLY at nodes of Ranvier
- saltatory conduction (action potential jumps from node to node)
- hyperpolarisation
- back to resting potential
12
Q
what is the importance of the refractory period
A
- ensures action potentials are discrete events, stopping them from merging into one another
- ensures the charge of the membrane potential is generated ahead rather than behind the original action depolarisation
- so impulse can only travel in one direction
13
Q
what is a synapse
A
where two neurones meet but do not actually touch - a tiny gap
14
Q
synaptic transmission
A
- Ca2+ channels open
- Ca2+ enters presynaptic knob
-vesicles contain neurotransmitter ACh - vesicles fuse with presynaptic membrane
- ACh released by exocytosis
- ACh diffuses across the cleft
- binds to receptors on post-synaptic membrane
- Na+ channels open
- Na+ enters post-synaptic neurone
15
Q
what is the role of acetylcholinesterase [2]
A
- breaks down neurotransmitter ACh
- recycles ACh
16
Q
why are there tight junctions between chemoreceptor cells
A
so theres no movement of substances between the chemoreceptor cells
17
Q
breakdown the structure of a muscle
A
- muscle
- muscle fibres
- myofibrils
- myofilaments
18
Q
2 types of myofilaments
A
actin - thin
myosin - thick
19
Q
what are myofilaments
A
repeating contracting units in a sarcomere
20
Q
when the muscle contracts, what happens
A
I band = shorter
A band = same
21
Q
when the muscle is relaxed what happens
A
- sarcomere is longer
- H band longer/wider
- light area on each side of Z line longer
22
Q
one sarcomere = between 2 Z lines
A
one sarcomere = between 2 Z lines
23
Q
neuromuscular junction
A
24
Q
what is the importance of the Schwann cell in transmission of nerve impulses
A
- myelin sheath
- insulates axon
- increases speed of impulse
- saltatory conduction
25
why is mitochondria needed in neuromuscular junction?
- produces ATP
- for recycling ACh
- for movement of vesicles (in presynaptic knob)
- for contraction of sarcomeres
- for sodium potassium pumps/ active transport
- active transport of Ca2+ into sarcoplasmic reticulum
- detachment of myosin heads/cross bridges (sarcolemma)
26
events occuring during muscle contraction
- sarcolemma depolarised
- transverse tubules depolarised
- Ca2+ ions diffuse out of sarcoplasmic reticulum
- Ca2+ ions bind to troponin
- troponin changes shape
- tropomyosin moves
- binding sites on actin exposed
- myosin heads bind to actin
- myosin heads tilt & pull actin so sarcomere shortens
- myosin head binds to ATP to allow detachment
27
why do venus flytraps trap flies
- not enough nitrate in soil
- poor mineral content of soil
- so flies provide minerals for GROWTH
28
response of venus flytraps to touch
- mechanical energy converted to electrical
- sensory haircells is receptor
- cell membrane depolarises
- if atleast 2 hairs touched within 35 secs, action potential occurs
- action potential spreads over leaf
- H+ pumped out of the cell into cell walls
- cell wall loosens & cross-links broken
- calcium pectate dissolves
- Ca2+ enter cells
- water enters by osmosis
- cells become turgid
- change from convex to concave
- trap shuts quickly in <1secs
- acid growth hypothesis
29
role of Auxin in cell elongation
-auxin binds to receptor in cell surface membrane
- auxin increases proton pump activity
- more protons (H+) enter cell wall
- cell wall becomes acidic/less pH
- expansins activated
- expansins break bonds between cellulose microfibrils
- K+ enters cell
- w.p of cell decreases
- water enters by osmosis
- turgor pressure so walls stretch
- acid growth hypothesis
30
why do aleurone layers of barley seeds need to produce amylase during germination
- amylase enters endosperm
- amylase hydrolyses starch to form maltose
- maltose converted to glucose
- glucose transported to embryo = providing energy for growth/ATP production
31
explain how endorphins may act to reduce pain
- endorphins bind to (endorphin) receptors
- stop calcium ions / Ca2+, entering presynaptic knob
- no / fewer vesicles fuse with, (presynaptic) membrane
- no / less ACh, released
- no / less, binding of ACh to postsynaptic receptors
- no / less, depolarisation of postsynaptic, neurone / membrane
- no / fewer, action potentials / impulses, to, pain centre / brain
32
When a mammal dies, aerobic respiration stops. The striated muscles contract and remain
contracted for a few hours after death. Why?
- no ATP produced
- so no breaking of cross bridges / myosin head not released
33
location of gibberellin synthesis in a barley seed during germination
embryo
34
why does germination increase as water potential increases
- low / negative, water potential decreases water uptake in seed
- water needed to activate embryo / produce gibberellin
- water needed for hydrolysis (reactions)
- starch to maltose / maltose to glucose
- water needed as a medium for reactions
35
what enzyme does gibberellin stimulate and where
- amylase / maltase/ protease
- aleurone layer
36
sequence of events that lead to poduction amylase during germination
- embryo absorbs water
- (stimulates) embryo to produce gibberellin
- gibberellin moves to aleurone layer
- gene coding for amylase, expressed
- translation of mRNA (to produce amylase)
37
where are starch reserves in a barley seed
endosperm
38
diff in function between motor and sensory neurones
- motor neurones - transmits impulses from CNS to effector
- sensory neurones - transmits impulses from receptors to CNS
39
what is the function of microvilli in chemoreceptors
- increase surface area
- for more Na+ channels/ more Na+ can enter
40
why is the speed of transmission faster in a myelinated neurone
- Na+ channels ONLY at nodes of Ranvier (in non-myelinated its all along the neurone)
- depolarisation ONLY occurs at nodes
- long local circuits
- saltatory conduction
41
explain what is happening in the striated muscle fibre during
the latent phase.
- transverse / T- , tubules depolarised
- Ca2+ diffuse out of sarcoplasmic reticulum
- Ca2+ bind to troponin
- tropomyosin moves from binding sites
- for myosin on actin
- cross-bridges form / myosin (head) binds to actin
42
why preventing the free movement of mitochondria within the cytoplasm of the axon affects the transmission of action potentials along the axon
membrane
- no ATP for sodium potassium pump/active transport of Na+ and K+
- reduces/prevents resting potential
- reduces transmission of action potential
43
Explain how the speed of transmission of nerve impulses in people with GAN can affect
walking
- takes longer for impulses to reach impulses
-fewer/slower muscle contractions
- slower reflexes
- walks slower/trips
44
Suggest reasons why a reduction in temperature can decrease the efficiency of contraction of striated muscle cells.
- respiration rate/ATP decreases
- reduces activity of enzymes
- reduces movement of Ca2+/ACH/Na+
- no acetylcholine broken down
- acetylcholinesterase inactive
- no Ca2+ bind to troponin
- no cross bridges formed
- no detachment of myosin heads
- no cross bridges broken
45
similarities in structure between a neuromuscular junction and a cholinergic
synapse
- acetylcholine from vesicles
- many mitochondria
- have presynaptic and postsynaptic membranes
- (synaptic) cleft / gap
- have receptor(s) (for ACh / neurotransmitter) ;
- presynaptic Ca2+ channels
46
Suggest why calcium phosphate formation in the sarcoplasmic reticulum may result in
fewer power strokes occurring in sarcomeres
- few(er) Ca2+ ions, leave sarcoplasmic reticulum / enter sarcoplasm
- few(er) Ca2+ ions bind to troponin
- few(er) troponin molecules change shape
- few(er) tropomyosin molecules move
- few(er) myosin-binding sites, uncovered / exposed
- few(er), actin-myosin cross bridges form / myosin (heads) bind to actin
47
Suggest how developing muscle cells that express stress genes will differ in structure from
normal muscle cells
- less actin
- less myosin
- less troponin
- less tropomyosin
- fewer / smaller sarcomeres / myofibrils
48
what does acetylcholinesterase do
- binds to ACh receptors
- so that Na+ channels open
- Na+ enters
- sarcolemma depolarised
49
role of synapses
- one way transmission of impulses
- communication between many neurones
50
similarities between the endocrine & nervous system
- both involve cell signalling
- both involve chemicals
51
what is a voltage gated channel
- ion transport
- opens/closes when voltage (charge) changes
