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ME2017 Science A > nerves MW%% (+ > Flashcards

nerves MW%% (+ Flashcards

1
Q

What are the subdivisions of the
nervous system?

A
  • The brain
  • The spinal cord
  • The peripheral nerves
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2
Q

Describe the four cerebrum components?

A

–Frontal lobe

–Temporal lobe

–Parietal lobe

–Occipital lobe

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3
Q

What are the components of Diencaphlon?

A

–Thalamus

–Hypothalamus

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4
Q

What are the components of the Brainstem?

A

–Midbrain

–Pons

–Medulla oblongata

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5
Q

What are the components of the spinal cord?

A
  • 31 pairs of spinal (plus 12 pairs of cranial) nerves
  • 8 cervical (7 vertebrae)
  • 12 thoracic
  • 5 lumbar
  • 5 sacral
  • 1 coccygeal
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6
Q

What is a vertebra made up of? (pic)

A
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7
Q

What is a neurons made up of?

A
  • Cell body (soma)
  • Dendrites –receive information
  • Initial segment (axon hillock ) –triggers action potential
  • Axon–sends action potential
  • Axon (presynaptic) terminals –release transmitter
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8
Q

What are the types of neurones?

A
  • Afferent (sensory) neurones (PNS⇒ CNS)
  • Interneurones (CNS)
  • Efferent (motor) neurones (CNS⇒PNS)
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9
Q

What are the different types of Glia?

A

•Astrocytes

–maintain the external environment for the neurones

–surround blood vessels & produce the blood brain barrier

•Oligodendrocytes

–form myelin sheaths in the CNS

•Microglia

–phagocytic hoovers mopping up infection

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10
Q

Name the different types of membrane potentials?

A
  • Action potentials –transmit signals over long distances
  • Graded potentials –decide when an action potential should be fired
  • Resting membrane potential –keeps cell ready to respond
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11
Q

Describe ionic bases of the resting membrane potenial?

A
  • In the cell membrane, there are Na/K pumps.2 K+ in 3 Na+ out.
  • Leaky K+ channels in the membranes
  • Allow K+ to flow out down the conc. gradient.
  • Creates an electrical gradient pulling the potassium back in.
  • Eventually, an equilibrium poteintial is reached where the electrical gradient is equal and opposite to the conc. gradient pushing the ions out of the cell (membrane potential).
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12
Q

The blood brain barrier

A

–Capillaries of the brain are especially “tight”

–Due to astrocytes & tight junctions between endothelial cells

–This protects the brain from changes in plasma [K+]

–The heart is not so lucky

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13
Q

Why is the normal RMP closer to -70mV?

A
  • Other “leaky” channels, especially Na+ & Cl-
  • Electrogenic nature of the Na/K pump
  • Large intracellular -ve charged molecules
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14
Q

Give Examples of graded potentials?

A
  • Generator potentials–at sensory receptors
  • Postsynaptic potentials–at synapses
  • Endplate potentials–at neuromuscular junction
  • Pacemaker potentials -in pace maker tissues
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15
Q

What are the properties of graded potentials?

A
  • Decremental ⇒ only useful over short distances
  • Graded ⇒ can signal stimulus intensity in their amplitude
  • Can be depolarising or hyperpolarising
  • Summate ⇒ important in synaptic integration
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16
Q

What is synaptic integration?

A
  • The process of summing all those inputs in space and time, to determine whether or not the initial segment reaches threshold.
  • Spatial, many to one
  • Temp: One to one, but frequent bursts
17
Q

Describe the ionic bases of the action potential?

A
  • Once a graded potential hits the threshold,
  • Voltage dependent Na channels open almost immediately,
  • Na floods in and depolarises the cell.
  • These change the potential of the neurone to around +40mV.
  • Causes volatage gated K+ channels to open
  • K+ goes out
  • Cell repolarises then hyperpolarises.
18
Q

What are the properties of action potentials?

A
  • They have a threshold
  • They are all or none
  • They cannot encode stimulus intensity in their amplitude, only in their frequency
  • Self propagate
  • Have a refractory period- local current flow also spreads back, NOT evoke a new AP there.
19
Q

What is the effect of large axons in increasing conduction velocity ?

A
  • A bigger axon has a lower axial resistance – means the depolarisation evoked at one channel can spread further
  • Means the Na+ channels can be spread out further
  • And the depolarisation from one will still be big enough by the time it gets to its neighbour to reach threshold and make its neighbour open.
20
Q

What is the effect of myelination on conduction velocity?

A
  • Na channels are only found in the nodes of Ranvier between these sheats
  • Which allow the transmission to travel further
  • And is still big enough by the time it reaches the next node to reach threshold and trigger another action potential.
21
Q

What is the effect of de-myelination?

A
  • Big local current decays quicker
  • Does not depolarise to next node to threshold.
  • And conduction fails.
22
Q

What is compound action potential?

A
  • Mammals have small and large unmyelinated
  • And small and large myelinated axons.
  • Therefore extracellular recording from a bundle of axons (a nerve trunk) evokes a “compound” action potential
23
Q

Descibe the mechanisms of neuromuscular junction?

A
  • Action potential in motor neurone
  • Opens voltage-gated Ca2+ channels in presynaptic terminal
  • Triggers fusion of vesicles
  • Acetylcholine (ACh) released
  • Diffuses across synaptic cleft
  • Binds to ACh (nicotinic) receptors
  • Opens ligand-gated Na+/K+ channels
  • Evokes graded (local) potential (end plate potential)
  • Always depolarises adjacent membrane to threshold
  • Opens voltage-gated Na+ channels - evokes new AP
  • ACh removed by acetylcholinesterase
24
Q

Name 4 chemical inhibitors at a neuromuscular junction?

A

–tetrodotoxin ⇒ blocks Na+ channels, no AP made

–joro spider toxin ⇒blocks Ca2+ channels. No ACh released in pre

–botulinum toxin ⇒ disrupts the release machinery. No ACh released

–curare ⇒ blocks Ach receptors. No end plate potential

– Acetylcholinesterase ⇒ no ACh broken down, so increased transmission at NMJ

25
Q

Name an excitory transmitter at a neuromuscular junction?

A
  • Anticholinesterases – block ACh breakdown
26
Q

What are the differences between central nervous system synapses and neuromuscular synapses?

A

In the Central nerrvous system synapses:

  • Range of neurotransmitters.
  • Range of postsynaptic potentials
  • Anatomical arrangement of synapse
  • Synaptic connectivity
27
Q

what are the ranges of postsynaptic potentials?

A
  • Fast EPSPs (ionotropic)
  • Slow EPSPs (metabotropic)
  • Fast IPSPs
  • Slow IPSPs
  • Enables complex synaptic integration
28
Q

what are the different types of Anatomical arrangement of synapse?

A
  • Axo-somatic
  • Axo-dendritic
  • Axo-axonal
29
Q

What are the different types of synaptic connectivity?

A
  • Convergence
  • Divergence
  • Feedback inhibition
  • Monosynaptic vs polysynaptic pathways

ME2017 Science A (26 decks)

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