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Year 13 Biology > Neuronal communication > Flashcards

Neuronal communication Flashcards

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1
Q

What features are common to all sensory receptors?

A

They are transducers which establish a generator potential

They respond to specific stimuli

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2
Q

Describe the basic structure of a Pacinian corpuscle

A

A single nerve fibre, with connective tissue and gel in a capsule

Stretch mediated Na+ channels on the plasma membrane

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3
Q

How and why does a Pacinian corpuscle respond to stimuli?

A
  1. Pressure deforms the membrane causing Na+ channels to widen
  2. Na+ diffuse into the neuron. If threshold potential is met then a generator potential is produced
  3. The action potential moves along the sensory neuron
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4
Q

Describe the features of all neurons

A

Cell body has organelles and many RER

Dendrons branch into dendrites which carry the impulses TOWARD body

Axon is a long fibre that carries impulses AWAY from body

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5
Q

Describe the structure and function of a sensory neuron

A

Transmits impulses from receptors to CNS

Long axon with cell body in the middle

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6
Q

Describe the function and structure of the relay neuron

A

Transmits impulses BETWEEN neurons

Highly branched dendrites

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7
Q

Describe the function and structure of the motor neuron

A

Transmits impulses from relay to effectors

Has cell body at end of axon

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8
Q

Describe the additional features of a myelinated neuron

A

Schwann cells

Myelin sheath (made of schwann cells)

Nodes of Ranvier

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9
Q

Why do myelinated axons conduct faster than unmyelinated axons?

A

Saltatory conduction- the impulse jumps from one node of ranvier to another

Depolarisation can’t occur where the myelin sheath acts as an electrical insulator

So impulse doesn’t travel whole axon length

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10
Q

Where are non/myelinated neurons found in the body?

A

Myelinated- Central and periphery system, involved in the spinal reflex

Non myelinated- nerve fibers that transmit secondary pain

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11
Q

What is resting potential?

A

The voltage across a neuron membrane when not stimulated (-70mv in humans)

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12
Q

How is resting potential established?

A

The membrane is more permeable to K+ ions than Na+ ions

The pump actively transports and removes 3 Na+ ions for every 2 K+ ions, creating an electrochemical gradient

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13
Q

Name the stages in generating an action potential

A

Depolarisation
Repolarisation
Hyperpolarisation
Return to resting potential

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14
Q

What are the seven stages in generating an action potential

A
  1. Stimuli causes sodium channels to open
  2. Threshold potential is reached at -40mv
  3. Sodium ions rush in, inside of cell becomes positive
  4. The potential difference reaches +40mv
  5. Voltage gated sodium channels close
  6. Potassium channels open and potassium diffuses out
  7. Potential difference falls below resting potential
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15
Q

Explain the importance of the refractory period

A

Na+/K+ pump must restore ion concentration after an action potential

Ensures a unidirectional impulse

Limits frequency of impulse transmission as no action potential can be generated in this period

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16
Q

Why is frequency of impulse transmission significant?

A

Allows organisms to distinguish size of stimulus despite all action potentials being the same magnitude

17
Q

What is the function of synapses? (3)

A

Allow neurons to communicate

Ensure transmission in one direction only

Filters out low level stimuli

18
Q

Describe the structure of synapses

A

Presynaptic neuron ends in synaptic knob which has a lot of mitochondria, ER and vesicles

Synaptic clefts exists between neurons

Pre and post synaptic neurons have complimentary receptors

19
Q

Describe the 7 steps involved in transmission across a cholinergic synapse

A
  1. A wave of depolarization arrives at the presynaptic neuron
  2. Calcium ion channels open and calcium ions move in by facilitated diffusion
  3. Synaptic vesicles fuse to the membrane of the knob releasing acetylcholine into the cleft
  4. Acetylcholine diffuses across and binds with sodium ion channels
  5. These channels open (on the postsynaptic neuron) and move in by facilitated diffusion
  6. Triggers an action potential
  7. Acetylcholine is broken down by an enzyme to diffuse out of the cleft
20
Q

Define summation and name the two types

A

Neurotransmitters from several sub threshold impulses accumulate to generate action potential

Temporal and spatial

21
Q

Temporal vs spatial summation?

A

Temporal- neurotransmitter released several times in quick succession

Spatial- multiple neurons release NT

Year 13 Biology (8 decks)

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