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Nervous system Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

neurones

A

highly specialised cells that contain organelles such as nucleus, endoplasmic reticulum, golgi, ribosomes and mitochondria in the cell body, as well as dendrites and axons

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2
Q

motor neurone

A
  • cell body in spinal cord or brain
  • axons can be very long
  • cell body and dendrites on one end of the axon, axon terminals on the opposite end
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3
Q

sensory neurone

A
  • cell body in dorsal root ganglia just outside spinal cord
  • dendrites and dendron on one end, cell body in middle on a stalk, axon and axon terminals on other end
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4
Q

relay/intermediate neurone

A
  • cell body in brain or spinal cord and connects with sensory and motor neurones
  • cell body in the middle surrounded by dendrites with axon shown as more defined part
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5
Q

schwann cells

A
  • wrap their cell membranes around the axon resulting in layers of fatty substance called myelin
  • the protein P0 locks the schwann cell together - mutations of the gene coding for this protein results in neuropathies
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6
Q

nodes of ranvier

A
  • gaps in myelin - 1-3mm
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7
Q

differences between myelinated and non-myelinated neurones

A

Myelineated;
- diamter 1-25 micrometers
- speed 6-120ms-1
- in 1/3 of sensory and motor neurones
Non-myelinated
- diameter <1 micrometer
- speed 0.2-0.5ms-1
- tend to be in CNS and neurones over short distances

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8
Q

nerve

A
  • bundle of neurones surrounded by perineurium
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9
Q

how does the myelin sheath allow signals to travel faster down a neurone?

A
  • myelin does not conduct electricity well so it prevents the loss of electrical signal from an action potential
  • myelin also isolates axons from one another in the white matter of the brain preventing the short-circuiting of signals in the central nervous system
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10
Q

sensory receptors

A
  • external or internal
  • detect changes in our surroundings (stimuli) and produce an electrical discharge by converting energy into electro-chemical signals (they’re transducers)
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11
Q

what is the information pathway of an impulse?

A
  • receptor, sensory neurones, relay neurones, spinal cord/brain, motor neurone, effector
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12
Q

what determines the strength of an electrical signal?

A

the frequency of impulses produced by the receptor

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13
Q

mechanoreceptor

A
  • pressure/movement
  • eg. parcinian corpuscle in skin
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14
Q

chemoreceptor

A
  • detects chemicals
  • eg. in nose
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15
Q

thermopreceptor

A
  • detects heat
  • eg. on tongue
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16
Q

photoreceptor

A
  • detects light
  • eg. cones in eye
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17
Q

transducer

A

a device that converts one form of energy to another

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18
Q

how does the parcinian corpuscle produce an electrical signal?

A
  • they are mechanoreceptors that detect pressure and movement
  • when pressure is applied, the lamellae will bend or stretch causing sodium ion channels to open in the axon membrane
  • sodium ions rush through the channel, if enough sodium ions make it through the channel, voltage gated Na+ channels open, it reaches the threshold and creates an action potential
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19
Q

action potential - resting state

A
  • 3 Na+ ions being pumped out the axon for every 2 K+ ions pumped in
  • inside of axon negatively charged at -70mV
  • Na+ ion channels closed
  • K+ ion channels open
  • voltage gated channels only open when a certain voltage is reached
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20
Q

action potential - depolarisation

A
  • some Na+ ion channels open and there is rapid influx of sodium ions down electro-chemical gradient
  • inside of cell becomes less negative
  • the change in charge causes more voltage gated Na+ ion channels to open and more sodium ions diffuse in - this is positive feedback
21
Q

action potential - repolarisation

A
  • when the potential difference reaches around +40mV, voltage gated sodium ion channels close and voltage gated potassium channels open
  • potassium ions move out of the cell restoring the negative charge but the position of the ions is reversed
  • so many K+ ions leave the axon that the potential difference becomes even more negative than the resting potential briefly - hyperpolarisation
22
Q

action potential - refractory period

A
  • sodium and potassium ion channels close
  • sodium potassium ion pump was always working but the action can be seen
  • resting potential restored as Na+ ions return to outside and K+ ions to the inside of the neurone
  • this area of the membrane is now able to generate another action potential
23
Q

how to action potentials travel across a neurone?

A
  • an action potential at one point in an axon membrane generates another action potential in the next part of the membrane as voltage gated sodium ion channels further along the channel open due to changes in charge
  • temporary depolarisation of the membrane causes a ‘local circuit’ to be set up and voltage-gated Na+ ion channels open
  • due to the refractory period, the action potential flows one way
24
Q

where on a neurone can action potentials occur?

A
  • at nodes of ranvier - they jump from node to node speeding up conduction by up to 50 times
25
Q

saltatory conduction

A
  • movement of an action potential across a myelinated neurone
  • once axon membrane is depolarized (Na+ on inside), Na+ move along axon as they’re attracted to negative charge
  • a long localised electrical circuit is created at the nodes of Ranvier
  • voltage gated Na+ channels open and more Na+ move into the axon in this region
  • this repeats along the axon at the nodes of Ranvier
  • this speeds up conduction by up to 50 times
26
Q

synapse

A
  • when neurones meet but do not join
  • made up of the ends of neurones and the gap between them - around 20nm
  • eg. neuromuscular junctions - where motor neurone end plate meets muscle fibres causing contraction
27
Q

how does an impulse travel across a synapse?

A
  • action potential arrives
  • Ca+ channels open and they move in to activate cytoskeleton to move vesicles
  • vesicles containign neurotransmitter move to presynaptic membrane
  • vesicles fuse with membrane and release neurotransmitter into synaptic cleft
  • neurotransmitter diffuses across synaptic cleft to post-synaptic membrane and binds with receptors
  • Na+ channels open - membrane is depolarised an action potential produced
28
Q

brain function

A
  • processes all info from sensory neurones from internal and external environment
  • processes info from hormones in blood
  • produces coordinated response via motor neurones and release of hormones
29
Q

cerebrum

A
  • controls voluntary actions eg. learning and memory
30
Q

cerebellum

A
  • controls unconscious functions eg. balance and non-voluntary movement
31
Q

medulla oblongata

A

autonomic control eg. breathing and heart rate

32
Q

hypothalamus

A

regulates things like temperate and water balance

33
Q

pituitary gland

A

stores and releases hormones that regulate body functions

34
Q

4 lobes of cerebral hemispheres

A

parietal
frontal
occipital
temporal

35
Q

part of brain that helps 2 hemispheres communicate

A

corpus callosum

36
Q

cerebral cortex

A

thick layer of grey substance that covers the 2 hemispheres

37
Q

how is nervous system split up

A

CNS and PNS
CNS - spinal cord and brain
PNS - somatic NS and autonomic NS
autonomic NS - sympathetic NS and parasympathetic NS

38
Q

autonomic NS

A
  • operates unconsciously
  • governs homeostatic mechanisms
  • stress response
  • non-myelinated neurones
  • connections to effectors are at least 2 neurones - pre-ganglionic and motor - connected by a ganglion
39
Q

parasympatheic NS

A
  • active during sleep and relaxation
  • neurones are linked at a ganglion within target tissue
  • pre-ganglionic neurones are variable in length
  • post-ganglionic neurones secrete acetylcholine at the synapse between neurone and effector
40
Q

sympathetic NS

A
  • active when stressed
  • neurones of pathway linked at ganglion just outside spinal cord
  • pre-ganglionic neurones are short
  • post-ganglionic neurones secrete noradrenaline at synapse between neurone and effector
41
Q

smooth muscle

A
  • found in walls of intestine, blood vessels, uterus etc.
  • involuntary movement
  • contraction initiated from autonomic NS and hormones such as adrenaline and oxytocin
  • contract slower and more steadily
  • tire less easily
  • not stripy
  • cells with own nucleus lying parallel to each other
  • long thin
  • contract by sliding actin and myosin but do not form sarcomere or myofibrils
42
Q

cardiac muscle

A
  • stripy
  • each cell contains fibrils made up of sarcomeres, is smaller than skeletal, has one nucleus
  • each cell branches to form connections with neighbouring cells
  • intercalculated discs separate fibres from each other
  • gap junctions in discs allow depolarisation to spread across cells
  • high oxygen requirement so lots of mitochondria
  • can only respire aerobically - uses fatty acids as respiratory substrate
  • doesn’t tire
    eg. atrial and ventricular muscle
43
Q

skeletal muscle

A
  • stripy
  • contracts quickly and powerfully but fatigues quickly
  • muscle cells form fibres (syncytium) containing several nuclei
  • each fibre surrounded by sarcolemma (membrane) with many infoldings - T-tubules
  • contain sarcoplasm, many mitochondria and sarcoplasmic reticulum
  • contain many myofibril organelles
44
Q

myofibrils

A
  • contractile elements of skeletal muscle
  • contain 2 types of myofilaments - thin actin, thick myosin
  • consist of chain of smaller units called sarcommere
45
Q

sarcomere structure

A
  • made up of thick myosin filaments and thin actin filaments
  • space between two Z lines is one sarcomere
  • M line - down middle of myosin
  • Z line - middle of actin
46
Q

thin filaments in sarcomere

A
  • made up of actin
  • tropomyosin coiled around actin
  • troponin attached to tropomyosin and contains 3 polypeptide chains connected to actin, tropomyosin and calcium ions
47
Q

thick filaments in sarcomere

A
  • made up of bundles of myosin
  • each myosin molecule consists of a tail and 2 heads which stick out
48
Q

power stroke / sliding filament model

A
  1. tropomyosin prevents myosin head attaching to binding site on actin
  2. Ca2+ from action potential released from sarcoplasmic reticulum bind to troponin and cause tropomyosin to pull away from binding sites on actin
  3. myosin head attaches to binding site on actin
  4. myosin head changes shape, moving actin filament along - ADP is released
  5. Atp molecule fixes to myosin head causing it to detach from the actin filament
  6. hydrolysis of ATP to ADP by myosin provide energy to change myosin head back to normal position
  7. myosin head reattaches to binding site further along actin filament and cycle repeated
49
Q

why and how is ATP created in muscle fibres?

A
  • only enough ATP in muscle fibre to support 1-2 secs of contraction so it must be regenerated
  • aerobic or anaerobic respiration is used
  • phosphtate group from creatine phosphate is transferred from ADP to form ATP using the enzyme creatinine phosphotransferase

Biology (17 decks)

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