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CCEA A2 Biology Unit 1 > U1T3 - Keywords (2) > Flashcards

U1T3 - Keywords (2) Flashcards

Animals

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1
Q

Nervous System

A

Consists of CNS + many peripheral nerves.

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2
Q

CNS

A

Brain + spinal cord. Integrates incoming info from peripheral nerves + coordinates effective response.

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3
Q

Centrons

A

Contains nucleus, mitochondria + other organelles + Nissi’s granules.

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4
Q

Dendrons

A

Fine threads of cytoplasmic threads which deliver impulses towards cell body in neurone.

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5
Q

Axons

A

Fine cytoplasmic threads which carry impulses away from cell body in neurone. Terminate in synaptic bulbs.

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6
Q

Sensory neurones

A

Have dendrons + axons with similar long length so cell body quite central. Carry impulses from receptors to CNS.

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7
Q

Motor neurones

A

Long axons with dendrites. Carry impulses from CNS to effectors.

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8
Q

Dendrites

A

Short dendrons

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9
Q

Relay neurones

A

Shorter overall, shorter dendrons + axons. Connect neurones within CNS.

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10
Q

Myelinated Neurone

A

Neurone wrapped in Schwann cells, created electrically insulating myelin sheath rich in lipid myelin. Between each SC, nodes of Ranvier exposed. Speed of impulse transmission greatly increased as local current only exists as nodes of Ranvier.

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11
Q

Nodes of Ranvier

A

Small patch of neurone membrane exposed in myelinated neurone.

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12
Q

Potential Difference

A

Difference in charge between 2 regions (e.g. inside + outside cell).

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13
Q

Polarised Cells

A

Cells with potential difference across membrane.

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14
Q

Neurones

A

Have excess of positively charged ions surrounding them, resulting in potential diff of -70mV. More + charged cells outside cell + cell contains many proteins which are - charged. Have cell body + extended nerve fibre.

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15
Q

Resting Potential

A

PD across CSM. (Neurones polarsed as electrochemical gradient across CSM) When neruones have excess of + charged ions around them, resulting in pot diff of -70mV. More + charged cells outside cell + cell contains many proteins which are - charged. Maintained as CSM mostly impermeable to flow of sodium ions when not conducting impulse.

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16
Q

Threshold Potential

A

-55mV in mammals. Is met when enough transmembrane proteins + positively charged ions open.

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17
Q

Action Potential

A

When PD across membrane reaches peak of around +40mV after stimulus applied and threshold potential reached and neurone becomes depolarised.

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18
Q

Sub Threshold Stimulus

A

A stimulus which doesn’t cause threshold potential to be reached and action potential isn’t fired. Display all or nothing principle in this case.

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19
Q

All or Nothing Principle

A

Action potential always peaks at same value regardless of stimulus intensity. More intense stimuli result in more frequency firing of action potentials.

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20
Q

Repolarisation

A

After depolarisation, neurone actively re-establishes it’s resting potential using this. Positively charged ions both diffuse and are actively pumped out of neurone into surrounding fluid.

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21
Q

Refractory Period

A

Period of time taken for repolarisation. Neurone can’t be stimulated during this time. Limits speed at which action potential fires + so allows coordinator (CNS) to detect each action potential as discrete event. Also ensures impulses travel in 1 direction.

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22
Q

Impulse

A

Propogation of action potentials along axon by flow of current in a series of localised currents.

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23
Q

Voltage Gated Ion Channels.

A

Transmembrane proteins. Able to sense localised changes in charge + respond by changing shape so positively charged ions flow into cell, resulting in depolarisation, making action potential more likely.

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24
Q

Saltatory Conduction

A

Due to fast transmission speed of myelinated neurone, localised currents jump from one node to the next, myelin sheath prevents depolarisation in myelinated zones, hence why it must jump to nodes of Ranvier so fast.

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25
Q

Synapse

A

Junction between axon of 1 neurone + dendrite of adjacent as they aren’t in physical contact. Electrical signals can jump across this gap. Includes synaptic bulb, synaptic cleft + post-synaptic neurone. Filter out low level background stimuli to prevent overload + overstimulation.

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26
Q

Tropism

A

Growth response

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27
Q

Acetylcholine

A

Primary neurotransmitter in CNS. Acts to make depolarisation more likely, found in excitatory synapses as its actions results in EPSP. Broken down into choline + ethanoic acid by ecetylcholinesterase.

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28
Q

EPSPs

A

Excitatory Post Synaptic Potential.

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29
Q

GABA

A

Neurotransmitter. Associated with IPSPs. Released at inhibitory synapses. Hyperpolarises neurone membrane resulting in lower PD across membrane which reduces likelihood of action potential so more + ions must move in to reach threshold potential. Reduces anxiety.

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30
Q

IPSPs

A

Inhibitory Post Synaptic Potentials. Central in reducing anxiety through reducing num of impulses which reach brain + reducing possibility of reflex actions being prevented.

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31
Q

Ciliary Muscles

A

Ring of muscle surrounding lens. Contains muscular ring of ciliary muscle around eye. Suspensory ligaments extend from ciliary body + hold lens in place. Adjusts lens shape to focus light rays.

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32
Q

Lens

A

Flexible fluid filled sac. Transparent biconcave structure with refractive properties which refracts light + focuses light rays on retina.

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33
Q

Refracted

A

Bent.

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34
Q

Retina

A

Inner layer of eyeball containing light sensitive receptor cells (rods + cones), bipolar cells + ganglion cells.

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35
Q

Visual Transduction

A

The process of converting light energy into an energy potential occurring.

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36
Q

Bleaching

A

When light strikes rhodopsin, causing it to break down into retinal + opsin.

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37
Q

Retinal Convergence

A

Many rods can synapse onto 1 bipolar sense resulting in high rod sensitivity so summation can occur.

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38
Q

Summation

A

Small amount of neurotransmitter released from few rod cells can be added together to open enough ion channels in bipolar cell to form action potential. Explains why rods provide decreased visual acuity as image formed is due to patch of cells being stimulated rather than single cell. Provides complexity + flexibility of synapses.

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39
Q

Light Adapted Eye

A

When rhodopsin almost entirely broken down as cones used for vision in bright light.

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40
Q

Dark Adapted Eye

A

After 30 mins in dark room so rhodopsin has reformed to allow rods to be sensitive.

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41
Q

Binocular Vision

A

Use of 2 eyes to form image, allows better distance perception + stereoscopic vision so brain can form 3D image. Distance between eyes + placement of head on animal determine visual field. Prey animals have eyes on side of head to have wide vision for predators.

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42
Q

Sarcolemma

A

Outer membrane of muscle fibre. Here, synapses of motor neurones make contact in motor end plates. Also forms T-tubules.

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43
Q

T-tubules

A

Deep infoldings at intervals along length of muscle fibre by sarcolemma.

44
Q

Sarcoplasmic Reticulum

A

Network of membranes within muscle fibre which act as storage site for calcium ions.

45
Q

Sarcoplasm

A

Cytoplasm of muscle fibre.

46
Q

Myofibrils

A

Functional units of muscle. Contraction occurs by shorting these. Made of sarcomeres in repeating pattern along length of myofibril.

47
Q

Myosin

A

Thicker fibrous protein with protruding heads at intervals along length. Forms denser striations.

48
Q

Actin

A

Finer fibrous protein with binding sites for myosin heads along length. Form lighter regions between them.

49
Q

Sarcomere

A

Unit of repeating pattern of actin, myosin + structures they attach to.

50
Q

Nerves

A

Bundles of neurones grouped together, protected within outer protective layer. Can contain sensory neurones only, motor neurones only or mix of both.

51
Q

Nervous Control

A

Involves receptors + effectors with interlinking coordinator.

52
Q

Receptors

A

Found in eyes + ears etc. Each sensitive to particular stimulus.

53
Q

Stimulus

A

Something we hear, see or smell.

54
Q

Effectors

A

Parts of body which produce response (muscles)

55
Q

Nissi’s Granules

A

Large groups of ribosomes.

56
Q

Threshold Stimulus

A

Level of stimulus necessary before action potential produced.

57
Q

Zone of Depolarisation

A

Part of neurone where polarity reversed.

58
Q

Pre-synaptic neurone

A

Neurone which releases transmitter. Specialised. End thickened into synaptic bulb + synpatic vesicles.

59
Q

Post-synaptic neurone

A

Neurone which receives diffusing neurotransmitter. Specialised. Membrane contains receptors complementary to type of neurotransmitter involved in the synapse.

60
Q

Synaptic Bulb

A

Contain large numbers of mitochondria necessary to create neurotransmitter.

61
Q

Synaptic Vesicles

A

Where neurotransmitter stored.

62
Q

Synapse Fatigue

A

When too many impulses pass along same neurone in short period of time, exhausting neurotransmitter supply more quickly than can be built up.

63
Q

Integration

A

Coordination of processes. Aided by summation.

64
Q

Excitatry Synapses

A

When neurotransmitter chemicals released with function of causing EPSP + subsequent action potential/

65
Q

Inhibitory Synapses

A

Make more difficult for synaptic transmission to occur using preventative neurotransmitter which lead to influx of - ions in PoS membrane so inside of membrane more negative, creating IPSP. This hyperpolarisation makes difficult to create EPSP.

66
Q

Noradrenaline

A

Results in EPSPs. Typically used in involuntary nervous control.

67
Q

Nicotine

A

Stimulates release of acetylcholine + other neurotransmitters making action potentials more likely. Allows Na ions to flood cell.

68
Q

Curare

A

Blocks receptors at neuromuscular junctions preventing synaptic transmission causing loss of muscle function.

69
Q

Opiods

A

Blocks CA channels in pre synaptic neurone so less transmitter substance released + action potentials less likely. Can provide pain relief by reducing impulses from pain receptors.

70
Q

Conjunctiva

A

Thin transparent membrane covering cornea which protects it from damage.

71
Q

Sclera

A

Tough opaque connective tissue covering eye, replaced by transparent cornea at front. Protects against damage + site of attachment of eye muscles.

72
Q

Cornea

A

Front transparent part of sclera where most refraction of light occurs.

73
Q

Aqueous Humour

A

Transparent watery fluid between cornea + lens which maintains shape of front part of eye.

74
Q

Iris

A

Muscular layer with circular + radial muscles, contains light absorbing pigment. Adjusts pupil size to control amount of light entering eye.

75
Q

Pupil

A

Gap within iris where light reaches lens + enters centre of eye.

76
Q

Suspensory Ligaments

A

Ligaments that connect ciliary body to lens. Transfer tension in eyeball wall to make lens thinner, important for distance vision. Tough + flexible but don’t stretch, allowing the lens to thin when they’re pulled.

77
Q

Vitreous Humour

A

Transparent, jelly like material between lens + back of eye which maintains shape of rear part of eye + supports lens.

78
Q

Fovea

A

Region in centre of retina which is rich in cones + doesn’t contain rods. Gives clearest daylight colour vision in eye.

79
Q

Choroid

A

Layer of pigmented cells between retina + sclera which contain blood vessels supplying retina + prevent reflection of light back through eye.

80
Q

Optic Nerve

A

Bundle of sensory nerve fibres that leave retina + transmit impulses from retina to brain.

81
Q

Blind Spot

A

Part of retina where sensory neurones that unite to form optic nerve leaving eye. Contain no light sensitive cells so not sensitive to light.

82
Q

Accommodation

A

Adjustment of lens thickness to ensure light rays are focused on retina, irrespective of angle of light rays reaching eye. Example of reflex action.

83
Q

Photoreceptors

A

Photosensitive cells. Light energy brings about change in level of polarisation of membranes. e.g. Rods + cones which as act as transducers converting light stimulus to nerve impulse in associated neurones.

84
Q

Rhodopsin

A

Light sensitive pigment which is packed into array of membranes in outer part of rod cell. Formed from protein opsin, combined with light absorbing compound retinal from vitamin A. When stimulated by light, breaks into components, changing membrane potential of cell + creating generator potential. . If threshold potential reached, becomes depolarised + action potential created.

85
Q

Trichromatic theory of colour vision

A

Blue, green + red.

86
Q

Generator Potential

A

Degree of depolarisation stimulated receptor can produce. Action potential only produced if it reaches threshold level.

87
Q

High Visual Acuity

A

Each cone cell can synapse individually with its own bipolar neurone so can provide own discrete image in vision which allows them to provide highly precise colour vision of high red allowing distance perception.

88
Q

Sensitivity

A

Ability to operate in low light intensities.

89
Q

Skeletal Muscle

A

Muscle under conscious/voluntary control. Alternating pattern of myosin + actin forms striated pattern.

90
Q

M-Line

A

Thin disc linking myosin filaments which it runs perp to.

91
Q

Z-Line

A

Thin disc linking actin filaments. Connective tissue.

92
Q

A-Band

A

Ansiotropic Band. Part of sarcomere containing myosin. Includes areas where actin penetrates between myosin filaments. Darker.

93
Q

I-Band

A

Isotropic Band. Part of sarcomere containing just actin. Lighter

94
Q

H-Zone

A

Zone in centre of A-Band where only myosin present.

95
Q

Sliding Filament Mechanism

A

The mechanism of muscle contraction. How myosin + actin filaments slide past each other, reducing overall length of sarcomere.

96
Q

Myelin Sheath

A

Insulating covering that surrounds axon with layers of myelin.

97
Q

Depolarisation

A

Loss of diff in charge between inside + outside of plasma membrane.

98
Q

Propogation

A

Transmission of motiom in certan direction/through medium.

99
Q

Iodopsin

A

Photosensitive violet pigment in retinal cones, formed from vitamin A.

100
Q

Stereoscopic Vision

A

Single perception of slightly diff image from each eye, resulting in depth perception.

101
Q

Rods

A

Specialised photoreceptor in retina that provides side vision + night vision.

102
Q

Cones

A

Photoreceptors in retina. Responsible for colour vision.

103
Q

Muscle Fibre

A

Muscle cell, especially cylindrical, multinucleate cells that make up skeletal muscles.

104
Q

Muscle

A

Bundle of fibrous tissue that can contract, producing movement.

105
Q

Tropomyosin

A

Protein involved in muscle contraction.

106
Q

BCC

A

Bright, circular, contracted.

107
Q

Alcohol

A

Hyperpolarises neurone, makes action potentials less likely.

CCEA A2 Biology Unit 1 (15 decks)

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