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communication, homeostasis and energy > neuronal communication > Flashcards

neuronal communication Flashcards

you will prefer stepping on legos once you complete this

1
Q

describe the sensory neurones structure and function

A
  • dendron from receptors in skin
  • axon leading to another neurone
  • cell body joining dendron and
    axon
  • transmits impulse from sensory receptor cell to relay neurone, motor neurone or brain (CNS)
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2
Q

what is homeostasis?

A

maintenance of a stable internal environmental within tolerable limits

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3
Q

describe the structure and function of a relay neurone

A
  • cell body in centre with lots of dendrites and axons coming out of it
  • transmits impulses between neurones
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4
Q

describe the structure and function of a motor neurone

A
  • cell body with dendrites coming off it
  • one long axon in direction of impulse
  • myelinated
  • schwann cells and nodes of ranvier
  • transmits impulse from sensory or relay neurone to effector
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5
Q

what are the key features of a neurone?

A

cell body
- DNA in a nucleus and lots of RER and mitochondria
dendrons
- protrusions from cell body connected to other cells
axons
- carry impulse away from cell body

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6
Q

what is the myelin sheath and why is it important?

A
  • made of many layers of schwann cell membranes
  • insulates the axon which helps increase speed of impulse
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7
Q

what are nodes of ranvier and why are they important?

A
  • gaps between adjacent schwann cells where saltatory conduction occurs
  • where axon depolarises
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8
Q

what is saltatory conduction?

A
  • depolarisation of the axon
  • impulse can “jump” from one node to another
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9
Q

what is the role of a receptor?

A

detect a stimulus

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10
Q

what structure are receptors?

A

specialised cells or peripheral endings of neurone

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11
Q

what transduction of energy occurs at receptors?

A

stimulus/mechanical energy (light, touch) to electrical energy

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12
Q

what are pacinian corpuscles?

A

mechanoreceptors found deep in skin of hands or feet

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13
Q

describe the structure of a pacinian corpuscle

A
  • non myelinated terminal of a neurone
  • surrounded by connective tissue
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14
Q

what ions channels are located in the neurone ending at the corpsucle?

A

stretch mediated ion channels

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15
Q

describe how a stretch mediated ion channel works in a corpuscle

A
  • high conc sodium ions outside axon and is less positive inside
  • when pressure is applied the gates open and sodium ions diffuse into sensory neurone down electrochemical gradient and becomes depolarised
  • this creates a generator potential
  • if enough pressure is applied, an action potential is produced
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16
Q

describe the components and events involved in a reflex arc

A
  • receptor cells detect a stimulus and sends an electrical impulse along sensory neurone
  • it passes over synapse to relay neurone in CNS and the motor neurone to effector cells which triggers them to react
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17
Q

describe how resting potential is generated

A
  • active transport of 2 K+ into cell for every 3 Na+ out of cell which uses a sodium potassium pump
  • results in more Na+ outside and more K+ inside
  • the uneven distribution causes facilitated diffusiondown electrochemical gradient
  • membrane is more permeable to K+ as more K+ ion channels are open than sodium ones so ends up more Na2+ and K+ outside than K+ inside
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18
Q

what is the value of resting potential?

A

-70mV

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19
Q

describe how an action potential is generated

A
  • energy of stimulus causes Na+ voltage gated ion channels to open and increase membrane permeability to Na+
  • sodium ions diffuse into axon making the outside less negative
  • change of pd causes more voltage gated ion channels to open and more Na+ to diffuse in (positive feedback)
  • continues until pd hits +40mV
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20
Q

describe the propagation of a nerve impulse as localised circuits

A
  • depolarisation can only occur at nodes of ranvier where no myelin is present
  • Na+ can pass through membrane at nodes
  • longer localised circuits arise between nodes
  • action potential jumps from nod to node
  • repolarisation uses ATP so having fewer nodes makes the impulse more efficient
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21
Q

describe how a resting potential is re-established after and action potential

A
  • once membrane reaches pd +40mV Na2+ channels close and K+ channels open
  • more k+ outside the membrane causes hyperpolarisation
  • eventually k+ channels close and sodium ions start diffusing down the electrochemical gradient
  • sodium potassium pump starts working again and re-establishes the resting potential
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22
Q

how does myelination affect speed of impulse?

A

allowing depolarisation at certain points in the membrane makes transmission faster as it doesn’t have to occur at every point along the membrane

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23
Q

how does axon diameter affect speed of impulse?

A

large diameter means faster flow as there is less resistance to flow of ions in cytoplasm

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24
Q

how does temperature affect speed impulse?

A
  • ions diffuse faster at a higher temperatures
  • occurs up to 40C as proteins denature
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25
Q

what is the all or nothing principle?

A

if the stimulus is not strong enough then there is not enough depolarisation to reach threshold value so action potential doesn’t occur

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26
Q

what is the refractory period?

A

hyperpolarisation after the action potential which prevents a stimulus leading to a second action potential

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27
Q

what is the importance of the refractory period?

A

ensures action potential:
- are discrete impulses
- do not overlap
- are unidirectional

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28
Q

what is the synaptic cleft?

A

gap that separates axon of one neurone and dendrite of the next which is 20-30nm across

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29
Q

what is the synaptic knob?

A

swollen end of the presynaptic neurone that contains lots of endoplasmic reticulum and mitochondria

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30
Q

what are the two types of neurotransmitter?

A

excitatory and inhibitory

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31
Q

why are mitochondria and ER in abundance in knob?

A

bulk transport required energy and synthesis of vesicles

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32
Q

what does an excitatory neurotransmitter do?

A

results in the depolarisation of the postsynaptic neurone which results in an action potential if threshold is reached

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33
Q

what does an inhibitory neurotransmitter do?

A

results in the hyperpolarisation of the postsynaptic neurone which prevents an action potential

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34
Q

what is the process of synaptic signal transmission?

A
  • action potential arrives at the presynaptic neurone and depolarises the membrane causing Ca2+ voltage gated ion channels to open
  • ions diffusion into presynaptic knob which causes synaptic vesicles containing neurotransmitters to fuse to the membrane and release them via exocytosis
  • they diffuse across the synaptic cleft and bind to specific receptor molecules on the post synaptic membrane
  • Na+ ion channels open and sodium ions diffuse into postsynaptic neurone and cause a new action potential
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35
Q

what molecule breaks down ACh and into what?

A

acetylcholinesterase into acetate and choline

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36
Q

what is summation?

A

combination of graded potentials in postsynaptic neurone

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37
Q

what is spatial summation?

A

the sum of excitatory potentials from different neurones triggering an action potential

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38
Q

what is temporal summation?

A

many excitatory potentials from one neurone in quick succession

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39
Q

how do synapses ensure unidirectional impulses?

A

receptors are only present on postsynaptic membrane

40
Q

what are the terms for impulses from a single neurone passing to many neurones and vice versa?

A

divergence and convergence

41
Q

what is the benefit of filtering out background stimulation?

A

ensures that only stimulation that is strong enough will be passed on

42
Q

outline the ways motor and sensory neurone are similar

A

both have
- dendrites
- axons
- cell body
- myelin sheath and schwann cells

43
Q

suggest how the immune system causes damage to the nervous system

A
  • antigens on neurones activate immune system
  • antibodies against neurones are produced
44
Q

where are acetylcholine receptors found ?

A

postsynaptic membrane

45
Q

suggest and explain the effect that nicotine has on the nervous system

A
  • nicotine slows down rate of transmission
  • binds to receptors
  • receptors remain in refractory period for longer
46
Q

suggest how GABA is released from the inhibitory neurone and why an action potential may not occur if both GABA and acetylcholine are released

A
  • nerve impulse causes influx of Ca2+ into presynaptic neurone
  • causes vesicles to fuse with the membrane and release GABA via exocytosis to diffuse across the synaptic cleft
  • binds to complementary receptors on post synaptic membrane
  • causes Cl- ion channels to open and the influx of chloride ions causes postsynaptic neurone to become hyperpolarised
  • when Na+ enters the postsynaptic membrane from acetylcholine, there isnt enough +ve charge to reach threshold voltage so no action potential occurs
47
Q

describe structure of the mammalian nervous system

A

(mention CNS, PNS, brain, spinal cord, motor system, sensory system, somatic system, autonomic system, sympathetic, parasympatheticf)

48
Q

what does the autonomic nervous system do?

A

controls involuntary processes using centres located near the medulla oblongata eg. swallowing, breathing, HR

49
Q

what do sympathetic nerves do?

A
  • release noradrenaline to mobilise body systems (fight or flight)
  • increase HR
  • open airways and dilate pupils
  • vasodilation
  • glucose release
50
Q

what do parasympathetic nerves do?

A
  • releases acetylcholine to relax body systems
  • rest HR
  • regular airways and pupils
  • regular glycogen and insulin levels
51
Q

how do reflexes increases survival?

A
  • doesnt involve decision making so more rapid so brain can deal with more complex responses
  • present from birth
  • fast
52
Q

what is a reflex?

A

an involuntary fixed response to a stimulus

53
Q

explain the knee jerk patella reflex

A
  • occurs when patellar tendon stretched
  • reflex arc followed but relay neurone also inhibits motor neurone of flexor muscle
  • extensor muscle contracts
  • determines the presence of spinal lesion
54
Q

explain the blinking corneal reflex

A
  • cornea touched/light
  • sensory neurone (5th cranial nerve) and motor neurone (7th cranial nerve) are involved
  • very rapid response to close eyes
  • tests brain stem function in unconscious patients
55
Q

what is the structure of cardiac muscle?

A
  • contract without stimulation (myogenic)
  • branched allowing faster signal propagation and contractions in 3D
  • connected by gap junctions at intercalated discs
  • more mitochondria as reliant on aerobic respiration
56
Q

what are the unique properties of cardiac muscles?

A
  • longer period of contraction and refraction which is needed to maintain a viable heart beat
  • tissue doesnt become fatigued allowing for continuous, lifelong contractions
  • interconnected network of cells is separated between atria and ventricles allowing them to contract separately
57
Q

what are the unique properties of smooth muscles?

A
  • long but slow contractions
  • controls involuntary contractions
  • not striated
  • spindle shape
  • uninucleated
58
Q

what are the unique properties of skeletal muscles?

A
  • short, rapid contractions
  • attached to the skeleton
  • voluntary movement
  • multinucleated tubular fibres that are heavily striated
59
Q

how are skeletal muscles organised?

A
  • muscular bundles containing multiple muscle fibres
  • enclosed by the sarcolemma
  • fibres are multinucleate and longer than normal cells
  • have a shared cytoplasm called the sarcoplasm
  • many mitochondria
  • T-tubules connected by sarcoplasmic reticulum
60
Q

how are muscle fibres formed?

A

individual embryonic muscle cells fusing together

61
Q

what is the sarcolemma?

A

plasma membrane that envelopes muscle fibres

62
Q

what are T-tubules?

A

points where membrane folds inwards to help spread electrical impulses throughout the sarcoplasm

63
Q

why are there many mitochondria in muscle fibres?

A

provide ATP for muscle contractions

64
Q

what is the sarcoplasmic reticulum?

A

modified ER that contains calcium ions for contraction

65
Q

what are myofibrils?

A

long cylindrical organelles made of proteins specialised for contractions

66
Q

what is the structure and function of myofibrils?

A
  • lined up in parallel to provide maximum force when contracting together
  • made of 2 different protein filaments (actin and myosin)
  • divided into repeating sections called sarcomeres
67
Q

what is in a sarcomere?

A
  • Z disc
  • I band
  • A band
  • H zone
  • M line
68
Q

describe the structure of a sarcomere

A

(refer to a diagram)

69
Q

where is tropomyosin found?

A

wrapped around the actin filaments

70
Q

where is the M line found?

A

down the centre of only the myosin filaments

71
Q

where is the Z line found?

A

down the centre of only the actin filaments

72
Q

where are I (light) bands found?

A

around where there are only actin filaments

73
Q

where are A (dark) bands found?

A

around areas with only myosin and also where myosin and actin overlap

74
Q

where are H zone found?

A

around areas with only myosin

75
Q

which part of the brain controls learning, memory and conscious thoughts?

A

cerebrum

76
Q

which part of the brain controls unconscious actions including posture and balance?

A

cerebellum

77
Q

which part of the brain controls breathing rate and heart rate?

A

medulla oblongata

78
Q

which part of the brain is the regulatory centre for temperature and water balance?

A

hypothalamus

79
Q

what is the structure of myosin?

A
  • globular heads that are hinged to allow them to move forwards and backwards
  • one head binds to ATP and the other to actin
  • two filaments wound around eachother
80
Q

what is the structure of actin?

A
  • binding sites for myosin (actin-myosin binding sites)
  • these are blocked by tropomyosin and held in place by troponin
  • two filaments wound around eachother
81
Q

what happens at neuromuscular junctions?

A
  • action potential initiated in motor neurone
  • acetylcholine released into synaptic cleft
  • depolarisation spreads along the sarcolemma and T-tubules
  • Ca2+ are released from the sarcoplasmic reticulum
  • sarcomere contraction is triggered, shortening the muscle fibres
82
Q

how is tropomyosin removed from myosin binding site on actin?

A
  • the arrival of an action potential means an impulse penetrates the muscle via transverse(T) tubules causing Ca2+ ion channels in the sarcoplasmic reticulum to open
  • calcium ions diffuse into muscle fibres and bind to troponin molecules
  • they change shape which causes the tropomyosin to move to a different position
83
Q

what happens when tropomyosin moves away from binding site?

A

myosin head is free to bind to actin which forms an actinomyosin bridge

84
Q

how does the actinomyosin birdge break?

A
  • ATP binds to active site on one myosin head
  • hydrolysed into ADP and Pi
  • energy releases moves the head back down to the starting position
85
Q

what is another name for the ATP binding myosin head?

A

ATPase

86
Q

what is the sliding filament theory?

A

movement of calcium ions to move tropomyosin, and the hydrolysis of ATP in the myosin head to move the actin filament long the myosin

87
Q

how does a sarcomere change when it contracts?

A
  • whole sarcomere shortens
  • I band and H zone become narrower
  • Z lines move closer together
  • A band remains the same
88
Q

what is white matter?

A

bundles of myelinated axons

89
Q

what is grey matter?

A

neuronal cell bodies and dendrites and unmyelinated nerve fibres

90
Q

what is the role of creatine phosphate in muscle contraction?

A

act as backup supply of phosphate ions to reform ATP quickly during short bursts of high activity

91
Q

energy from the hydrolysis of ATP is needed for what two processes during muscle contraction?

A
  • movement of myosin heads
  • active transport of calcium ions back into the sarcoplasmic reticulum
92
Q

explain how it is possible for ACh to have an effect on cells in the skin of the squid

A
  • secreted into the blood as it can be a hormone
  • binds to receptors on cell surface membrane of skin
93
Q

which subdivision of the peripheral nervous system supplies the SAN?

A

autonomic nervous system

94
Q

which part of the brain are the nerves that the SAN attach to connected to?

A

medulla oblongata

95
Q

explain how blocking calcium channels could inhibit insulin secretion

A

calcium ions cant enter the cell so dont trigger vesicles to release insulin via exocytosis

communication, homeostasis and energy (6 decks)

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