NEURONAL COMMUNICATION Flashcards

1
Q

State the basic plan of a nervous system

A
Change in enviro of receptor stimulus 
Receptor generates nerve impulses 
Sensory neurone 
Relay neurones in CNS
Motor neurone 
Effector (muscle of GLAND)
Response
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2
Q

What is a neurone

A

Specialised cells that transmit an ACTION POTENTIAL from one part of the body to another

  • protect body
  • maintain homeostasis
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3
Q

What are dendrites

A

Small extensions on cell body, creating larger SA carrying impulses towards cell body
-one= dendron

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4
Q

What is the axon

A

Single long fibre carries impulse AWAY from cell body

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5
Q

Function of axon terminals

A

Large SA

Lots of connections

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6
Q

What does the cell body contain

A

Nucleus and other organelles

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7
Q

Benefits of having long neurones

A

Transmit action potential over long distance

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8
Q

Benefits of sodium potassium pumps

A

Actively transport sodium out of the cell and potassium into the cell (ATP)
3 sodium out, 2 potassium in

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9
Q

Benefits of gated ion channels

A

Controls entry/exit of sodium/potassium/calcium ions

Ions= polar= repelled by bilayer

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10
Q

Benefits of organelles in the cell body

A

Mitochondria, nucleus, ribosomes, ER, Golgi- for production of neurotransmitters

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11
Q

Benefits of the myelin sheath

A

Fatty sheath insulates neurone from other electrical activity
20-30 layers of schwa cell membrane

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12
Q

Describe the myelin sheath

A

Wrap themselves around the axon
Made of myelin (lipid)
1/3 of cells are myelinated (speeds up conduction, 1ms-100ms)

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13
Q

What are gaps between schwa cells called

A

Nodes of Ranvier

2-3 um wide

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14
Q

Function of sensory neurone

A

Carry an action potential from sensory receptor to CNS

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15
Q

Function of motor neurone

A

Carry action potential from CNS to an effector (e.g. muscle or gland)

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16
Q

Function of relay neurone

A

Connect sensory and motor neurone

17
Q

Sensory neurone:
Position of cell body
Length of dendrites
Length of axon

A

Outside CNS
Long, dendrites end axon
Short- outside CNS- inside CNS (spinal cord)

18
Q

Motor neurone:
Position of cell body
Length of dendrites
Length of axon

A

Inside CNS
Many short dendrites
Long (outside CNS- effector)

19
Q

Relay neurone:
Position of cell body
Length of dendrites
Length of axon

A

Within CNS
Short
Short

20
Q

What is a nerve impulse

A

Temporary reversal of the electrical potential difference across the neurone membrane

21
Q

What is the resting potential

A

Potential difference across the neurone cell membrane while membrane is at rest
Polarised membrane approx -70mV

22
Q

How is the resting potential maintained

A

Phospholipid bilayer impermeable to ions
Sodium-potassium pump actively transports (ATP) 3NA+ out, 2K+ in
Potassium can diffuse back through open channel proteins
Sodium channels are closed, diffusion of potassium is passive- down a concentration gradient
Cytoplasm contains negatively charged ions (e.g. protein molecules)
Interior of neurone= negative

23
Q

Function of channel proteins

A

Voltage gated- whether open or closed depends on voltage across membrane, changes of ion concentration changes protein shape
Stimulus sensitive- increase pressure, increase NA+ channels open

24
Q

What is the action potential

A

Brief reversal of the potential across the membrane of a neurone causing a peak of +40mV compared to resting potential -70mV

25
Q

Explain the concept of all or nothing

A

Below threshold value, no impulse generated
Above threshold, impulse generated
AP is the same size
Larger stimulus= more frequent the impulses

26
Q

What is the refractory period

A

Follows AP, short period of time where another AP is impossible
V-gated Na+ channels are closed
Keeps AP going in one direction
Separates AP