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bio Mod 5 > Neuronal Communication > Flashcards

Neuronal Communication Flashcards

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1
Q

What are sensory receptors?

A
  • Specialised cells that can detect changes in our surroundings
  • Most are transducers that convert one form of energy to another
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2
Q

How is a change in light detected and processed?

A

Rods and cones in the retina convert light energy to electrical

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3
Q

How is a change in temperature detected and processed?

A

Temperature receptors in the skin and hypothalamus convert heat energy to electrical

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4
Q

How is a change in pressure detected and processed?

A

Vibration receptors in the cochlea of the ear convert movement to electrical energy

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5
Q

How is a change in movement detected and processed?

A

Hair cells within ear convert movement to electrical energy

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6
Q

How is a change in muscle length detected and processed?

A

Muscle spindles in skeletal muscles convert movement to electrical energy

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7
Q

How is a change in pressure detected and processed?

A

Pacifism corpuscles in the skin convert movement to electrical energy

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8
Q

Explain the structure and function of a pacinian corpuscle

A
  • Rings of connective tissue wrapped around the end of a nerve cell
  • pressure changes on the skin deforms the rings of connective tissue which push against the nerve ending
  • when pressure is constant they stop responding
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9
Q

What happens when a membrane is deformed by changes in pressure?

A
  • Sodium channels open allowing a large influx of sodium ions
  • This produces a generator potential
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10
Q

What is the role of sodium/potassium pumps?

A
  • When the channel proteins are all closed they help to maintain a concentration gradient by pumping -3 sodium ions pumped out of the cell for every 2 potassium ions that get pumped in
  • membrane is more permeable to potassium ions so some leak out of the cell
  • membrane is less permeable to sodium so few are able to leak into the cell
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11
Q

What is the role and structure of motor neurones?

A

Carry an action potential from the CNS to an effector such as a muscle or gland

-have a long axon and their body in the CNS

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12
Q

What is the role and structure of sensory neurones?

A

Carry an action potential from a sensory receptors to the CNS

Have a long dendron and a cell body positioned just outside CNS, short axon carrying the action potential to the CNS

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13
Q

What is the role and structure of relay neurones?

A

Have short dendrites and a short axon connecting the sensory and motor neurones together in the CNS

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14
Q

What is the myelin sheath?

A
  • possessed by myelinated neurones(most sensory and motor)
  • Schwann cells wrapped tightly round the neurone consisting of layers of membrane and cytoplasm
  • Intervals/gaps are called nodes of ranvier
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15
Q

Why does the myelin sheath make conduction more rapid?

A

Movement of ions across the membrane can only occur at the nodes of Ranvier, meaning that the action potential jumps from one node to the next: saltatory conduction

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16
Q

What are non-myelinated neurones?

A
  • several neurones covered by one loosely wrapped Schwann cell
  • action potential moves along the neurone in a wave rather than jumping
  • often used in coordinating body functions
17
Q

What are the stages of an action potential?

A
  1. Membrane at resting state- polarised- inside of cell -60 mV. Higher concentration of sodium ions outside than inside and vice versa
  2. Sodium ion channels open and sodium diffuses into the cell
  3. membrane depolarises, less negative with respect to outside of the cell -50 mV
  4. positive feedback causes nearby voltage-gated sodium channels to open and sodium ions flood in
  5. Cell has become more positive compared to the outside +40 mV, the neurone will transmit the action potential
  6. Sodium ion channels close and potassium channels open allowing potassium to diffuse out of the cell- depolarisation
  7. PD overshoots slightly making the cell hyperpolarised but PD is soon restored
18
Q

What is the resting potential of a membrane?

A

-60 mV

19
Q

What is the threshold value for an action potential?

A

+40mV

20
Q

What is the refractory period?

A

After an action potential the sodium/potassium pumps restore the right concentrations and ensures that action potentials are only transmitted in one direction

21
Q

Explain local currents and their impact

A
  1. When an action potential occurs sodium ion channels open at that point in the neurone
  2. Open sodium ion channels allow sodium ions to diffuse across the membrane into the neurone increasing their concentration inside the neurone
  3. This causes sodium ions to diffuse sideways along the neurone along a conc gradient
  4. This causes a slight depolarisation along the neurone causing voltage-gated sodium channels to open allowing rapid influx and action potential further along
22
Q

What is saltatory conduction?

A
  • In myelinated neurones when ionic movements create an action potential only at the nodes of Ranvier.
  • This means that local currents are elongated so sodium ions diffuse along the neurone from one node to the next, action potential jumps
23
Q

How do we determine the intensity of the stimulus?

A
  • All action potentials have the same magnitude

- However a higher frequency means a more intense stimulus

24
Q

What is the pre-synaptic bulb? And what does it contain?

A

Neurone ends in a swelling which contains:
•many mitochondria- active process requires ATP
•Large amount of SER which package the neurotransmitter into vesicles
•large numbers of vesicles containing acetylcholine, the neurotransmitter
•voltage-gated calcium ion channels

25
Q

What is the post-synaptic membrane?

A

Neurotransmitter diffuses across the synaptic cleft until it reaches the post-synaptic membrane:
-Contains specialised sodium ion channels which have receptor sites complementary to acetylcholine

26
Q

Explain transmission across a synapse

A
  1. Action potential arrives at pre-synaptic bulb
  2. Voltage gated calcium ion channels open and calcium ions diffuse into bulb
  3. Calcium ions cause synaptic vesicles to move to and fuse with the pre-synaptic membrane
  4. Acetylcholine is released by exocytosis and diffuse across cleft
  5. Acetylcholine binds to receptor sites on sodium channels in post-synaptic membrane causing them to open
  6. Sodium ions diffuse across post-synaptic membrane causing an EPSP
  7. If sufficient generator potentials combine the potential across the post-synaptic membrane reach the threshold
27
Q

What is the role of acetylcholinesterase?

A
  • Enzyme found in the synaptic cleft which hydrolyses acetylcholine to ethanoic acid and choline
  • This stops the transmission of signals so the synapse does not continue to produce action potentials
28
Q

What is an excitatory post-synaptic potential? (EPSP)

A

The small depolarisation in the post-synaptic membrane caused by an action potential

29
Q

What is a summation?

A

When ESPSs accumulate to form another action potential
Temporal summation: Several from one pre-synaptic neurone
Spatial summation: from several different pre-synaptic neurones

30
Q

What are IPSPs?

A

Inhibitory- reduce the effect of summation

31
Q

What happens when we become habituated to a stimulus?

A

When a synapse runs out of vesicles containing the Mauro transmitter, the synapse is fatigued

bio Mod 5 (6 decks)

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