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Bio A2 Level > 15 Control and Coord > Flashcards

15 Control and Coord Flashcards

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1
Q

Describe a hormone (6)

A
  • chem subst produced by endocrine gland + carried by blood
  • alter the activity of 1+ specific target organs
  • long lasting effect
  • slow speed of tranmission
  • widespread
  • made up of secretory cells + gland is a group of cells that produces and releases 1+ subst
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2
Q

what type of mols are these hormones, insulin, glucagon, ADH, adrenaline

A
  • cell-signalling molecules that are released into the blood
  • peptides/small proteins
  • only affect cells w receptors
  • Receptors have to be complementary for there to be an effect
  • water-sol + cannot cross the PLB of CSM
  • hormones bind to receptors on CSM of target cells (cell singalling)
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3
Q

describe features of endocrine glands that help hormones enter blood faster

A
  • good blood supply as when they make hormones they need to get them into the bloodstream ASAP
  • so they can travel around the body to the target organs to bring about a response
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4
Q

describe these hormones Hormones such as testosterone, oestrogen and progesterone

A
  • steroid hormones
  • lipid-soluble + can cross the PLB
  • These hormones bind to receptors in the cytoplasm or nucleus of target cells
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5
Q

Human nervous ss

A

Central nervous system (CNS) – the brain and the spinal cord
Peripheral nervous system (PNS) – all of the nerves in the body

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6
Q

Nerve is same as neurone, true or false?

A

FALSE
A bundle of neurones is known as a nerve

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7
Q

General neurone ss

A
  • long fibre known= axon
  • axon is insulated by meylin sheath sheath , with small uninsulated sections along it = nodes of Ranvier
  • myelin sheath made by Schwann cells
    -electrical impulse does not travel down the whole axon, but jumps from one node to the next via Saltatory conduction
  • cell bodies contain extensions - dendrites
  • so can connect to many other neurones + receive impulses from them, forming a network for easy comms
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8
Q

three main types of neurone: sensory, relay and motor

A
  • Sensory neurones carry impulses from receptors to the CNS (brain or spinal cord)
  • Relay (intermediate) neurones are found within CNS + connect sensory and motor neurones
  • Motor neurones carry impulses from the CNS to effectors (muscles or glands)
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9
Q

Motor neurone ss

A
  • A large cell body at one end, that lies within the spinal cord or brain
  • nucleus,mitochondria/RER/golgi in cell body
  • many highly-branched dendrites extending from cell body= increase SA for the axon terminals of other neurones
  • neurotranmistters in synapatic vesicles + diffuse across synapse
  • long axon
  • schwann cells/nodes of ranvier
  • dendrites attached to cell body
  • dedrites have receptors for neuro
  • CNS to effector
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10
Q

Sensory neurone ss

A
  • cell body that branches off in the middle of the cell -
  • cell body basal root ganglion
  • shorter axon
  • dendrites attached to dendron
  • receptor to CNS
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11
Q

reflex arc pathway (w/o conscious input)

A
  1. innate/involuntary reponse
  2. stimulus
  3. receptor
  4. sensory neurone send electrical impulse to dorsal root in spinal cord
    4. synapses
    - electrical impulse passed onto RN in spinal cord
  5. relay neurone connects to MN and passes on electrical impulse
    6. synapses
  6. motor neurone transmits electrical impulse to effector for corrective action
  7. effector
  8. automatic response
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12
Q

Sensory receptor cells

A
  • cell that responds to stimulus is a receptor cell
  • receptor cells are transducers – they convert energy in one form e.g light/heat/sound into an electrical impulse/energy within SN
  • found in sense organs (eg. light receptor cells are found in the eye)
    e.g light receptors in the eye and chemoreceptors in the taste buds,= specialised cells that detect a specific type of stimulus
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13
Q

what happens when sensory receptor cells are stimulated

A
  • they are depolarised
    If the stimulus is very weak, the cells are not sufficiently depolarised so sensory neurone not activated to send impulses
  • If the stimulus strong enough = the SN is activated + transmits impulses to CNS
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14
Q

chemoreceptors detecting salt

A
  1. surface of the tongue covered in small bumps/ papillae
    - surface of papilla covered w taste buds containing chemoreceptors
    - detect salt/NaCl (chemical stimuli) + respond directly to sodium ions
  • Na+ diffuse into cell through high selective channel proteins in CSM of microvilli
    2) via membrane of microvilli depolarised
    3) increase in positive charge inside the cell is = receptor potential
    3) if receptor potential becomes large enough to stimulate by Na+ THEN causes Ca2+ ion VGC to open
    4) entry of Ca2+ into cytoplasm of chemor cells + stimulates exocytosis of vesicles containing neurotransmitters from basal membrane of chemo recept
    5) if stimulation of action potential in SNis above threshold, the neurotransmitter stimulates an action potential in the sensory neurone —> transmits an impulse to the brain
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15
Q

generator/receptor potential

A
  • weak stimulus =receptor cells not sufficiently depolarised and the SN not activated to send impulses
  • some Na+ channels open
  • some Na+ diffuses in
  • does not reach threshold potential
  • Na+/K+ pump restores resting potential
  • abides by all-or-nothing principle
  • An impulse is only transmitted if the initial stimulus is sufficient to increase the membrane potential above a threshold potential
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16
Q

action potential

A
  • rapid change in PD across memb caused by changes in permeability of CSM to Na+ & K+
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17
Q

how resting potential is maintained

A
  • not transmitting impulses + -70mV
  • by keeping more +ve ions outside the cell than inside = -ve resting potential for neurone

1) done by using a Na+/K+ pump in axon memb; it uses ATP to pump 3Na+ out of axon and 2K+ in

2) membrane also has more protein channels for K+ than Na+, and due to the concentration of K+ being higher inside, it diffuses out of the neurone, making the resting potential even lower

3) many -vely charged molecules are also present inside axon, and the membrane is impermeable to them/neurone is more -ve inside= attracts potassium ions reducing them diffusing out of axon + Na2+ ions cannot diffuse through axon memb when neurone at rest

  • closure of VGC proteins = stops sodium and potassium ions diffusing through axon memb
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18
Q

Events that tranmist nerve impulse/action potential

A
  1. Resting potential
  2. Depolorisation + Action potential
  3. Repolorisation
  4. Hyperpolirastion
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19
Q

speed in mylenited vs unmyleinedt sheath

A

MS= 100ms-1
UMS= 0.5ms-1

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20
Q

Resting potential

A
  • axon is not conducting nerve impulse
  • axon is PLB imperable to Na+ and K+ ions
  • axon contains Na2+ and K+ ion pump for AT, using ATP
  • Na+/K+ pump is globular protein w ATP binding site
  • K+ that are pumped in diffuse back down its conc gradient trhough protein channels then go back down into axon
  • Na+ move in via FD
  • overall excess of +ve ions outside memb compared to inside as more +ve pumped out of axon than in
  • more K+ ion channels open than Na+ ion channels
  • memb more permeable to K+ ions
  • More K+ ions leave than Na+ ions enter
  • K+ ions diffuse out and Na+ ions diffuse in
  • VGC closed
  • -70mV
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21
Q

Why is inside neg comapred to outside

A
  • High conc of positive ions outside axon compared to inside
  • Inside axon there are neg charged orgo mol, proteins and ions
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22
Q

Depolorisation and action potential

A
  • Neurone is stimulated
  • Axon memb has increased permeability to sodium ions
  • specific voltage dependet sodium channels open + allows sodium ions to diffuse rapdily down conc/electrochemical gradient INTO axon
  • a cell becomes +ve on inside compared to outside +40mv = action potential and memb depoloraised
  • long local circuits
  • action potential only at nodes of ranvier
  • saltutatroy conduction
  • 1 way tranmission
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23
Q

Repolorisation

A
  • Sodium ion channels close
  • Permeability of memb to K+ increases as VG K+ channels open
  • K+ diffuses out of axon down conc/electrochem gradient attracted by neg charge on outside of memb
  • K+ and Na2+ which are +ve charged leave cells, making inside of axon more neg compared to outside again
24
Q

Hyperpolorisation

A
  • too much K+ leave neurones
  • VG K+ channels close after delay
  • Charge inside axon becomes more neg that originally was
  • The PD becomes less neg
  • Memb remains permeable to K+ because K+ ion channels are open
  • K+ moves in because of charge diff into the axon, removing +ve charge from outside/inside less neg charge
  • resestablishes resting potential
  • stage of hyperpolorisation where neg is most is refractory period
  • absolute refractory period occurs aft action potential + period where action potential cannot be generated because Na2+ channels closed
  • K+ VGC still open
  • relative refractory period occurs a few miliseconds aft absolute refractory period where axon can be restimulated but will ONLY respond to stronger stimulus than before so threshold raised
25
Q

explain the importance of the refractory period in determining
the frequency of impulses

A
  • ensures action potentials pass along as seperate signals + unidirectional
  • length of refractory period determines max frequency of nerve impulses
  • high frequency of action potentials
26
Q

size of action potential comapred to size of stimulus

A
  • action potential only generated if stimulus reaches threshold leevl
  • below this threshold no action potential can be created
  • the threshold for any nerve fibres is point at which sufficnet Na2+ ion channels open for Na2+ to move into axon FASTER than outflow of K+
  • Size of action potential always same
  • A bigger stimulus INCREASES the FREQUENCY of action potentials NOT STRENGTH e.g more action potentials fired, in a weka stimulus eg punched in stomach, many receptors in skin/baroreceptors detect stimuli and strong stimulu so reaches threshold potentia;, more action potentials generated
27
Q

explain using an example how sensory receptors in mammals convert energy into action potentials

A
  • baroreceptor in skin detect stimulus e.g pressure
  • stimulus causes sodium ion channels to open
  • potassium ion channels open
  • potassium ions leave axon cell
  • depolorisation
  • generator potential
  • if greater than threshold leads to action potential
  • less than threshold only localised epolorisation
  • increased stimulus leads to increased frequency of action potentials
28
Q

chemoreceptors detecting sweet

A

1) cell sensitive to sweet have protein receptors that stimulate a G-protein
2) G-protein activates an enzyme that produces cyclic AMP
3) cyclic AMP acts as a 2nd messenger, activating a cascade to amplify the signal that leads to K+ channels closing
4) this depolarises the membrane

29
Q

why do we need mitochondria in synaptic knob

A
  • produces ATP
  • ACh production
  • Vesicle fromation
  • Excoytosis
  • Functioining of ion pumps
30
Q

role of synapses

A

1) one-way transmission beacuse receptors are only present on 1 side of synapse so impulses are unidrectional
2) interconnection of nerve pathways= 1 neuorne may have syanpses w/ many other nuerones
3) Summation: where 3 neurones tgt release small amounts of neurotranmsitter (not enough for Action potential to occur) at the sae synapse, but tgt neuroT releases WILL reach threshold level for action potential to occur

31
Q

Describe ultrass of striated muscle

A
  • fibres are multinucleate ;
  • CSM is sarcolemma ;
  • sarcoplasm has many mitochondria ;
  • 4 sarcoplasmic reticulum membranes have protein pumps ;
  • 5 transverse system tubules / T-system ;
  • 6 ref. to myofibrils ;
  • 7 thick filament / myosin, attached to M line ;
  • 8 thin filament / actin, attached to Z line ;
  • 9 interdigitation of filaments causes striated appearance ; -, A / H / I, bands ;
  • 11 sarcomere is the distance between M lines ;
  • 12 myosin is a fibrous protein with globular protein head
  • 13 actin is a chain of globular protein molecules ;
  • 14 tropomyosin / troponin, attached to actin ;
32
Q

describe the roles of neuromuscular junctions, the T-tubule system

A

Sarcolemma/CSM infolds = network of memb running through –> Trasverse tubular endoplasmic reticulum/T tubules which help to spread impulses through the sarcoplasm near sarcoplasmic reticulum
- muscles cells have myoglobin = so have higher affinity to O2 than Hb, accepting O2 from blood and stores O2 in muscles
- muscles attathed to skeleton
- small amounts of ATP in muscle fibres

33
Q

SS of cardiac muscle

A
  • striations at regular intervals
  • uninucleate cells joined by intercalated discs
  • cells shorter w branches connecting to adjacent cells
  • organised into parallel bundles of myofribrils
  • heart
  • myogenic
34
Q

SS of smooth muscle

A
  • no striations
  • uninucleate cells
  • long, unbranched cells that taper at eitheir end
  • contractile proteins not organised into myofribils
  • tubular ss e.g blood vessels, arterioles, oviducts
  • neurogenic
35
Q

How do muscle contract

A

A band= actin + myosin
I band= only actin filaments
H zone= only myosin filaments
Z line= one sarcomere

When a muscle contracts, actin filaments slide over mysoin filaments:
- I band shorter
- Z lines closer tgt + sarcommere shortens
- H zone narrower
- A lines stay same length
- so everything shorter EXCEPT A bands

36
Q

transverse system tubules (T-tubules)

A
  • infolding/invagination of sarcolemma
  • formed from the inward extension of sarcolemma
  • allows impulses from sarcolemma to pass to the SR
  • maintains Ca2+ store in SR
37
Q

structure of thick filaments (myosin)

A
  • made of myosin (a fibrous protein with a globular head)
  • fibrous protein anchors molecule to thick filament
  • globular heads point away from M-line
38
Q

structure of thin filaments (actin)

A
  • made of actin (a globular protein)
  • many actin molecules link to form a chain
  • 2 chains twist to form an active filament

tropomyosin (fibrous): twisted around 2 chains/filament
troponin: attached to actin chain at regular intervals, Ca2+ binding site**

39
Q

sliding filament model of muscle contraction

A
  • Nerve impulse reaches NMJ
  • Ca2+ channel gates open so Ca2+ ions enter synaptic bulb, vesicles w neurotransmitter fuse w presynaptic memb + releasing neuroT into synaptic cleft and binds to receptor on Post SM/sarcolemma so Na2+ ion channels open = depolorize memb of muscle fibres –> action potentail generated
  • depolorisation of sarcolemma spreads down t tubule

3) 1) Ca2+ is released from stores in SR and binds to troponin, changing it’s shape

2) troponin and tropomyosin move to different positions on thin filament, exposing myosin binding sites on the actin chain/filament

3) myosin head attactched to actin filament usuing ATP = binds to exposed binding sites, forming cross-bridges between thick and thin filaments/actomysoin cross brdidge

4) myosin changes shape + heads tilt, pulling/sliding actin filaments past myosin filaments usuing ATP, towards centre of sarcomere/shortens = power stroke

5) Free ATP binds to head so shape of myosin head change, binding of head to actin filament broken
6) ATPASE in mysoin head breaks ATP into Pi and ADP = recovery stroke
7) W continued stimulation calcium ions remain in sarcoplasm and cycle repeated IF NOT = calcium ions actively pumped into SR + T tubules
8) Troponin + Tropomyosin return to OG positions and contraction complete = MF relaxed

40
Q

describe role of ATP in muscle contraction

A
  • ATP hydrolysed. causing mysoin head to change shape + ATP binding frees mysoin from cross bridge
  • ATP used in AT of calcium ions back into SR
41
Q

Suggest how a tumour on the optic nerve could prevent the transmission of nerve impulses to the brain. [3]

A

1) compresses nerve
2) damages myelin sheaths / Schwann cells
3) prevents the setting up of local circuits / saltatory conduction
4) stops Na+ / K+ pumps from working
5) blocks blood supply
6) oxygen supply / glucose supply / ATP production is reduced

42
Q

Explain why the aleurone layers of barley seeds need to produce amylase during germination. [3]

A

1) amylase enters endosperm
2) hydrolyses starch to maltose
3) glucose needed by embryo for
4) for ATP production
5) for growth of embryo

43
Q

Describe the effects on the cell wall of many hydrogen ions moving into the cell wall. [3]

A

1) cell wall pH decreases/becomes more acidic

2) expansins are activated by decrease in pH

3) they loosen non-covalent bonds / cross-links

4) between cellulose and hemicellulose OR between cellulose microfibrils

5) cell wall expands

6) due to turgor pressure on wall

44
Q

describe part played by auxins in apical dominance in plant shoot

A
  • IAA (Auxin) /plant growth regulator
  • synthesized in meristems/apical buds
  • diffuses down stem
  • moves by diffusion/AT from cell to cell
  • through plasmodesmata + phloem
  • Mass flow in phloem
  • stimulats cell elongation
  • inhibits side growth/laterbal buds
  • plants grow upward/taller + stem elongates
  • auxin concetrated in lateral buds
  • ROLE OF ABA
45
Q

Describe the role of giberllins in stem elongation

A
  • giberellin is a plant growth regulator
  • controlled by Le/le gene
  • dominant allele Le gives functional enzyme/active giberellin
  • without GA - TF/PIF attatched to DELLA
  • GA binds to receptor causes DELLA protein breakdown
  • TF/PIF/RNA poly binds to DNA
  • growth genes expressed/transcribed
  • stimulates cell division + cell elongation
    -increased internode growth
  • plant grows tall
    -loosens cell wall so celols expand when water enters
46
Q

describe role of giberellin in germination of barely/wheat seeds

A
  • barely seed is dormant
  • water enters seed by osmosis
  • embryo produces/releases gibrellin
  • gibberellin stimulates aleurone layer to produce amylase
  • switches on/activates trancription enzyme genes/transcription of mRNA = amylase
  • amylase hydrolyses starch in endosperm to maltose/glucose
  • embryo uses sugars for resp
  • energy used for growth of embryo plant
47
Q

describe response of venus fly trap to touch

A
  • mechanical energy converted to electrical energy
  • sensory hair cell is receptor and detects touch
  • cell membrane depolarises if at least 2 hairs touched within 35s
  • action potential occurs/depolorisattion + spreads over lobes
  • hinge/midrib cells
  • H+ pumped out of cells into cell walls
  • cell wall loosens/cross links broken
  • calcium pectate dissolves in middle lamella
  • calcium ions enter cells
  • water enters cells via osmosis
  • cells expand/become turgid
  • change from convex to concave
  • trap shuts quickly
48
Q

why reducing temp reduces contraction efficeny in muscles

A
  • less ATP produced ;
    -reduces movement of, Ca2+ / Na+ / ACh / neurotransmitter ;
  • no, Ach broken down
  • acetylcholine remains attached to receptors
  • acetylcholinesterase, less active /
    fewer / no, Ca2+ bind to troponin
    fewer / no, cross bridges formed
    fewer / no, power stokes ;
    -/ no, detachment of myosin heads (from actin)
  • no, cross bridges broken
  • reduced blood flow to muscle / energy diverted for thermoregulation (
49
Q

explain how a cholinergeic synapse fucntions

A
  • impulse/ action potential/ depolarisation, reaches, synaptic knob ;
  • Ca2+ ion VGC channels open (in pre-synaptic membrane) ;
  • Ca2+ enters (synaptic knob/ pre-synaptic neurone) ;
  • vesicles with acetylcholine, move towards /fuse with, pre-synaptic membrane;
    -(ACh) released I secreted I exocytosis ;
  • ACh diffuses across synaptic cleft ;
  • binds to receptors on post-synaptic membrane ;
  • (ligand-gated) Na+ channels open and Na+ enters post-synaptic neurone ;
  • depolarisation I action potential I EPSP ;
  • acetylcholinesterase, breaks down ACh / recycles Ach ;
50
Q

saltatory conduction

A
  • action potential jumps from node to node
  • local circuits set up between nodes/longer
  • fast/increases speed of tranmisson
  • 100ms-1 vs 0.5ms-1
51
Q

explain how auxin causes plant to elongate

A

acid-growth (hypothesis) ;
auxin stimulates proton pumps ;
3 (in) cell surface membrane ;
4 protons / H+, pumped into cell wall ;
5 using energy / by active transport
; 6 pH of cell wall decreases / cell wall becomes (more) acidic ;
7 pH-dependent enzymes activated ;
8 ref. to expansins ;
9 bonds between cellulose microfibrils broken ;
10 idea that cell wall, ‘loosens’ / becomes more elastic / able to stretch ;
11 (more) water enters cell / turgor pressure increases ;
12 (so) cell (wall) expands

52
Q

role of acetylcholinestrase

A
  • breaks down ach to acetate and choline
  • so ach leaves binding site
  • depolraistion on post synaptic memb stops
  • stops continous action potentials
  • ach can be recyled
53
Q

explain what happens during A- depolorisation, B repolorisation and C hyperpolorisation

A

A
1 Na+ / sodium, channels already open OR
Na+ has already entered neurone OR
no more Na+ channels to open OR
less Na+ outside to diffuse in OR
less steep Na+ concentration gradient ;

B – any one reason from:
2 sodium channels are, inactive / unresponsive OR
potassium channels are open OR
membrane is, impermeable / less permeable, to Na+ OR
membrane is more permeable to K+ ;

C – any one reason from:
3 harder to reach threshold OR
potassium channels are (still) open OR
sodium-potassium pumps need to restore the resting potential ;
4 hyperpolarisation at

54
Q

explain how transmission of actio potential occurs in mylentied neurone

A
  • sodium channels open
  • sodium enters axon
  • causes depolarisation
  • sodium ion channels close
  • potassium, ion channels open
  • membrane, more permeable, potassium, ions
  • potassium moves out of axon, inside becomes negative
  • causes repolarisation
  • local circuits
  • solitary, conduction/action potential jumps from node to node
  • mylene sheath, insulates axon
  • action, potential notes of Ranveer
  • one way you need directional transmission
  • hyperpolarisation to maintain resting potential by sodium potassium pump
55
Q

I’m scared

A

Bio A2 Level (8 decks)

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