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Biology is for cool people > 15. nervous coordination and muscles > Flashcards

15. nervous coordination and muscles Flashcards

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1
Q

What are the three types of muscle?

A
  • smooth
  • cardiac
  • skeletal
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2
Q

What is meant by sarcoplasm

A

myofibrils share nuclei and cytoplasm

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3
Q

Describe the structure of actin

A
  • thin, globular protein
  • long chains in a helical shape
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4
Q

Describe the structure of myosin

A

‘Thick filament’ made up of two proteins;
- tail, long fibrous protein
- head, globular protein, two bulbous at the end

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5
Q

Describe the structure and function of tropomyosin.

A
  • long, thin wound around actin filaments
  • covers actin binding site, calcium ions expose binding sites, allowing myosin heads to bind
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6
Q

Draw and label that a sarcomere

A

go online for images :)

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7
Q

What is meant by ‘slow twitch fibres’

A
  • slow, less powerful contractions
  • contract for long periods
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8
Q

How are slow twitch fibres adapted for their function?

A

Adapted for aerobic respiration;
- large supply of myoglobin (store of oxygen)
- large supply of blood vessels (glucose + oxygen)
- many mitochondria (ATP)

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9
Q

How are fast twitch fibres adapted for their function?

A

Adapted for anaerobic respirations
- more myosin fibres
- high concentration of glycogen
- enzymes involved in anaerobic respiration
- phosphocreatine, replenishes ATP from anaerobic respiration.

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10
Q

What is meant by ‘fast twitch fibres’

A

rapid, powerful contractions for a short period, adapted for anaerobic respiration

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11
Q

Give four similarities between neurotransmitter and cholinergic junctions.

A
  • neurotransmitters move by diffusion
  • neurotransmitters binding to receptors causes influx of sodium ions
  • Na/K pump repolorise
  • use of enzymes to hydrolyse neurotransmitters
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12
Q

Give four differences between neurotransmitter and cholinergic junctions.

A

neuromuscular junctions;
- only excitatory
- involves motor neurons only
- action potential ends here
- acetylcholine binds to muscle, not another neuron

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13
Q

Give four pieces of evidence for the sliding filament theory.

A
  • increased overlap of filament when contracted, appears darker.
  • I-band is narrower when contracted
  • z-lines are closer together, sarcomere is smaller
  • H-zone is shorter
  • A-band remains the same when contracted, shows that filaments are not shortening
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14
Q

Describe the seven steps of the sliding filament theory.

A

1) action potential reaches muscle

2) calcium ions enter sarcoplasmic reticulum and cause movement of tropomyosin to expose actin binding sites

3) myosin head forms ‘cross-bridge’ by binding to actin binding site. With ADP + pi

4)ADP detaches, bend created by rotation of myosin head (req ATP) , pulling actin filament,

5) attachment of new ATP molecule causes myosin heads to detach

6) hydrolysis energises myosin and causes it to move back to normal position.

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15
Q

Describe what happens when muscle is relaxed.

A
  • calcium ions actively transported into ER
  • tropomyosin covers up actin binding site
  • can be stretched by antagonist (to a pont)
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16
Q

What neurotransmitter is found at neuromuscular junctions?

A

Acetylcholine

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17
Q

What enzyme hydrolyses Acetylcholine?
Why does this occur?

A
  • acetylcholinerase
  • to prevent muscle from being overwhelmed by sodium ions
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18
Q

Summarize what happens at neuromuscular junctions.

A
  • impulse reaches junction
  • synaptic vesicles (containing acetylcholine)
    fuse to presynaptic membrane
  • acetylcholine diffuses to post-synaptic membrane
  • acetylcholine causes a change in shape of sodium ion channels, increasing their permeability to sodium
  • sodium ions enter postsynaptic membrane (muscle), depolarisation.
  • acetylcholine is hydrolysed by acetylcholinesterase
  • products diffuse back into presynaptic membrane.
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19
Q

What is meant by ‘motor unit’?

A

Fibres that share a motor neuron, allows for more units stimulated if more force is required.

20
Q

How are rapid muscle contractions allowed?

A

Many neuromuscular junctions, action potential reaches across muscle

21
Q

Explain the stages of action potential

A

DEPOLARIZATION
- stimuli opens some Na+ channels (fac diff), reversal of electrochemical gradient
- more Na+ channels open

REPOLARIZATION
- +40mV = voltage-gated sodium channels close, potassium channels open, K+ out of axon (fac diff).
- more channels open

HYPERPOLARIZATION
- temporary overshoot of electrical gradient (too negative) k+ channels close, resting is established by Na/K pump

22
Q

Explain what is meant by saltatory conduction.

A

depolarization can only take place at nodes of ranvier.
insulation from myelinated sheaf, depolarization cannot take place here

faster action pot. at myelinated axons

23
Q

Describe the structure and function of sensory neurons

A
  • impulse from receptor to intermediate neuron
  • one (long) dendron
  • one axon
24
Q

Describe the structure and function of Motor neurons.

A
  • intermediate to receptor
  • One long axon
  • many dendrite
25
Q

Describe the structure and function of Intermediate neurons

A
  • impulse between different types of neurons (eg. sensory to motor)
  • many short axon/dendrites
26
Q

What direction do dendrites/ dendrons carry impulse?

A

towards cell body

27
Q

What direction do axons carry impulse?

A

away from cell body

28
Q

Explain how resting potential is maintained at the axon.

A

More positive outside neuron membrane, maintained by sodium-potassium pump
- 3Na+ out, 2K+ in
- electrochemical gradient
- K+ diffuse out (more permeable)
- SOME Na+ diffuse in (less permeable)

29
Q

Contrast the permeability of axon membrane to Na+ and K+ at resting potential

A
  • more permeable to K+, more channels, some always open
30
Q

What is the voltage of resting potential?

A

-50, -90mV
-65mV in humans

31
Q

Ignoring saltatory conduction, what are the functions of schwann cells?

A
  • electrical insulation
  • phagocytosis
  • regeneration
32
Q

What is the voltage at action potential (at the most depolarized)

A

+40mV

33
Q

Describe what happens at cholinergic synapses. (6)

A
  • arrival of action potential at presynaptic neuron causes calcium channels to open (enter fac diff)
  • influx of calcium ion causes synaptic vesicles to fuse with membrane (acetylcholine into synaptic cleft)
  • acetylcholine diffuses across cleft, binds to receptor on sodium channels on membrane of post-synaptic channel opens, Na+ in rapidly (fac diff)
  • influx of Na+ generates new action potential
  • acetylcholinesterase hydrolyses acetylcholine into acetyl and choline, diffuse back into presynaptic neuron
  • ATP from mitochondria, is used to create acetylcholine, stored in synaptic vesicle
34
Q

Why is acetylcholine hydrolysed after being released into synaptic cleft?

A
  • recycle products at SER
  • prevents too much stimulus, Na+ channels close
35
Q

Factors affecting the speed of action potential

A
  • mylenatic sheaf, saltatory conduction
  • diameter of axon, larger = less leakage of ions, faster
  • temperature, rate of diffusion, enzymes involved in respiration (sodium-potassium pump)
36
Q

Describe and explain the importance of the refractory period.

A

Sodium channels remain closed after action potential.
- ensures action potential travels in one direction, prevent from going backwoods
- separates impulses
- limits no. of impulses and therefore strength of impulses

37
Q

Draw and label the structure of a synapse.

A

including structures;
- mitochondria
- SER
- calcium channels
- vesicles
- presynaptic membrane
- synaptic cleft
- sodium ion channels
- postsynaptic membrane

38
Q

Explain the ‘all or nothing’ principle

A

Stimulus must exceed threshold value to create action potential.

39
Q

How is the size of stimulus detected?

A
  • no. of impulses in a given time
  • some neurons have different threshold value, detected by brain
40
Q

Describe spacial summation

A
  • multiple presynaptic neurons produce enough neurotransmitters for action potential
  • multiple action pot. into one action pot.
41
Q

Temporal Summation

A

neurotransmitter released multiple times in short period to exceed threshold.

42
Q

Inhibitory synapses

A
  • releases neurotransmitter that bind to chloride channels on postsynaptic membrane
  • chloride channels open, in by fac diff
  • also causes potassium to open, K+ out of postsynaptic
  • post synaptic membrane is more negative (hyperpolarization)
  • resting = -80mv
  • more Na+ needed to establish action pot.
43
Q

What are the functions of synapses

A
  • action pot. from one neuron to multiple = simultaneous response
  • multiple impulses combined at one synapse, single response from many stimuli
44
Q

define summation

A

rapid build up of neurotransmitters in the synapse to help generate action potential

45
Q

To enter the bowman’s capsule, molecules have to small enough to fit through…

A

gaps in epithelial lining of capillaries and gaps between podocytes

46
Q
A
47
Q

how do synapse ensure unidirectional flow of depolarisation

A

sodium channels only on post synaptic membrane

neurotransmitter released at the pre synaptic membrane only

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