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biology paper 2 > 15 nervous coordination > Flashcards

15 nervous coordination Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what are the two main forms of coordination in animals?

A

the nervous system

the hormonal system

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2
Q

what is the nervous system?

A

uses nerve cells to pass electrical impulses along their length, rapid but responses are short lived and restricted to a localised region of the body

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3
Q

what is the hormonal system?

A

produces chemicals that are transported in the blood plasma to their target cells, slower less specific form of communication but results are long lasting and widespread

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4
Q

what are neurones?

A

specialised cells adapted to rapidly carrying nerve impulses

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5
Q

what are the structural components of a neurone?

A

cell body - contains nucleus and other organelles
axon - carries impulses away from cell body
dendrites/dendrons - carry impulses towards cell body
myelin sheath - made of Schwann cells, protects and insulates
nodes of ranvier - constrictions between Schwann cells where no myelin sheath

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6
Q

what is the resting potential in humans?

A

-65mV

inside membrane negative outside positive

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7
Q

what is resting potential?

A

electrochemical gradient between the inside and the outside of the axon, sodium ions outside, potassium ions inside

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8
Q

what maintains resting potential?

A

active transport - sodium potassium pump, for each ATP molecule 3 Na+ pumped out and 2Na+ pump in
unequal facilitated diffusion - more leaky potassium channels than sodium channels so potassium diffuses out faster than sodium diffuses in

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9
Q

what is an action potential?

A

the nerve impulse, a rapid reversal of the resting potential

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10
Q

what are the main stages of an action potential?

A

depolarisation
repolerisation
hyperpolarisation
return to resting potential

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11
Q

what occurs during depolarisation?

A

some voltage gated sodium channels open causing more to open allowing sodium ions to diffuse in
positively charged so trigger a reversal in the potential difference

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12
Q

what occurs during repolarisation?

A

once an action potential of +40mV is reached sodium channels close and potassium channels open
positively charged potassium ions diffuse out

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13
Q

what occurs during hyper polarisation?

A

diffusion of potassium ions causes a temporary overshoot

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14
Q

are resting and action potentials active or passive processes?

A

resting potential - active

action potential - passive

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15
Q

why is an action potential self-propagating?

A

the depolarisation of one region of an axon will immediately cause the depolarisation of the next region

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16
Q

what is the role of the myelin sheath?

A

electrical insulation
physically protect
speed up transmission of nerve impulse

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17
Q

what is saltatory conduction?

A

when nerve impulse jumps from one node to the next

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18
Q

what factors affect the speed of conductance of a nerve impulse?

A

saltatory conduction along myelinated neurones
wider axon diameter, less leakage of ions
temperature, high increases enzyme activity, too high denatures them

19
Q

what is the all or nothing principle?

A

if the potential generated reaches the threshold value an action potential is generated
if the generator potential is not large enough there is no action potential
all action potentials are the same size

19
Q

what is the refractory period?

A

after an action potential is created there is a period when sodium voltage gated channels are closed making it impossible to create an action potential

20
Q

what are the purposes of the refractory period?

A

ensures that action potentials are propagated in one direction only
produces discrete impulses, separates action potentials from each other
limits the number of action potentials

21
Q

what is a synapse?

A

the point where one neurone communicates with another or with an effector

22
Q

what are the structural components of a synapse?

A 
presynaptic membrane
postsynaptic membrane
synaptic knob
synaptic cleft
vesicles
22
Q

what are key features of synapses?

A

unidirectional - impulse can only pass one way
inhibitory - some synapses make it less likely a new action potential will be created
summation - combine to generate an impulse

23
Q

what is spatial summation?

A

many different neurones collectively trigger a new action potential by combining the neurotransmitter the release to exceed threshold

24
Q

what is temporal summation?

A

a single neurone releases neurotransmitter many times over a short period which add up to enough to exceed threshold

25
Q

how to inhibitory synapses function?

A

presynaptic neurone releases a neurotransmitter that binds to chloride ion protein channels on postsynaptic membrane
causes chloride channels to open
chloride ions move into postsynaptic neurone
binding of neurotransmitter causes opening of potassium channels
potassium ions move out of neurone
negatively charged chloride ions moving in and positively charged potassium ions moving out makes it more negative so its harder to reach threshold

26
Q

what is a cholinergic synapse?

A

neurotransmitter is acetylcholine

27
Q

what are the three types of muscle in the body?

A

cardiac muscle: in the heart
smooth muscle: walls of blood vessels and gut
skeletal muscle: attached to bone and acts under voluntary control

28
Q

general structure of skeletal muscle

A

made up of many myofibrils which are collectively very powerful
separate cells fused together into muscle fibres, they share nuclei and cytoplasm, calles sarcoplasm, large conc of mitochondria and ER

29
Q

what are the main types of protein that make up myofibrils?

A

actin: thinner and consists of two strands twisted around one another
myosin: thicker and consists of long rod-shaped tails with bulbous heads

30
Q

microscopic structure of myofibril

A

I bands: lighter because filaments don’t overlap, only actin
A bands: darker because actin and myosin overlap
H-zone: only myosin, but no heads
Z line: end of each sarcomere

31
Q

how do skeletal muscles occur?

A

antagonistic pairs which pull in opposite directions, when one is contracted the other is relaxed

32
Q

why do muscle occur in antagonistic pairs?

A

muscles can only pull, can only move in one direction

33
Q

evidence for the sliding filament mechanism

A

when a muscle contracts:
I-band becomes narrower
Z-lines move closer together (sarcomere shortens)
H-zone becomes narrower

33
Q

evidence for the sliding filament mechanism

A

when a muscle contracts:
I-band becomes narrower
Z-lines move closer together (sarcomere shortens)
H-zone becomes narrower

34
Q

what is tropomyosin?

A

long thin threads that are wound around actin filaments

35
Q

the sliding filament mechanism

A

1) tropomyosin prevents myosin head from attaching to binding site on actin
2) calcium ions released from ER cause tropomyosin to change shape, uncovering binding sites
3) myosin head forms cross bridges with actin
4) head pulls actin over myosin, ‘power stroke’, ADP molecule released
5) new ATP attaches to myosin head, causing it to detach
6) hydrolysis of ATP to ADP provides energy for head to ‘re-cock’
7) myosin head reattaches to binding site further along actin

36
Q

what happens during muscle relaxation?

A

calcium ions are actively transported back into endoplasmic reticulum using energy from hydrolysis of ATP
reabsorption of calcium ions allows tropomyosin to block actin filament again
myosin heads unable to bind to actin so can’t contract

37
Q

what are the two types of skeletal muscle?

A

slow-twitch fibres

fast-twitch fibres

38
Q

what is myoglobin?

A

respiratory protein found in slow-twitch fibres that has a high affinity for oxygen (stores oxygen)

39
Q

comparison of slow-twitch and fast-twitch fibres

A

slow-twitch darker colour, high conc of myoglobin, fast-twitch lighter colour, low conc of myoglobin

slow-twitch used for endurance activity, contracts slowly and fatigues slowly, fast-twitch used for rapid bursts of activity, contracts quickly and fatigues quickly

slow-twitch uses aerobic respiration, high density of mitochondria, fast-twitch uses anaerobic respiration, low density of mitochondria

40
Q

comparison of cholinergic synapse and neuromuscular junction

A

both unidirectional

neuromuscular only excitatory, cholinergic excitatory or inhibitory

neuromuscular connects motor neurone to muscles, cholinergic connects two neurones

neuromuscular is end point for action potential, cholinergic new action potential generated in next neurone

biology paper 2 (13 decks)

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