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nerve impulses Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

define a stimulus

A

any change in the internal or external environment of an organism

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2
Q

what are receptors

A

receptors detect stimuli, they can be cells or proteins on cell surface membrane

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3
Q

what are effectors

A

effectors are cells that bring about a response to a stimulus, to produce an effect. they include muscle cells and cells found in glands

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4
Q

compare nervous communication to the endocrine communication

A
  • nervous communication is faster
  • nervous communication is short-lived
  • nervous communication is localised
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5
Q

how is the nervous response localised

A
  • when an electrical impulse reaches the end of a neurone
  • neurotransmitters are secretly directly onto target cells
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6
Q

what is the central nervous system made up of?

A
  • brain
  • spinal cord
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7
Q

what is the peripheral nervous system made up of?

A

neurones that connect the central nervous system to the rest of the body

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8
Q

what is the peripheral nervous system split into?

A
  1. somatic nervous system
  2. autonomic nervous system
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9
Q

what does the somatic nervous system control?

A

controls conscious activities (kicking a ball)

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10
Q

what does the autonomic nervous system control?

A

controls unconscious activities (heart rate

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11
Q

what are sensory neurones

A

they transmit electrical impulses from receptors to the central nervous system - the brain and spinal cord

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12
Q

what are motor neurones

A

they transmit electrical impulses from the CNS to effectors

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13
Q

what are relay neurones

A

they transmit electrical impulses between sensory neurones and motor neurones

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14
Q

explain why the neurone cell membrane is polarised at resting potential

A
  • there are more positive ions on the outside of the cell membrane than on the inside
  • creating a potential difference across it
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15
Q

what does the autonomic system split into?

A
  1. sympathetic nervous system
  2. parasympathetic nervous system
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16
Q

what does the sympathetic nervous system control?

A
  • controls the flight or fight response
  • speeds things up via noradrenaline
17
Q

what does the parasympathetic nervous system control?

A
  • calms the body down, it is the rest and digest system
  • slows things down via acetylcholine
18
Q

describe the structure of an myelinated motor neurone

A
  1. cell body - contains the nucleus and large amounts of rough endoplasmic reticulum for the production of protein and neurotransmitters
  2. dendrons - small extensions of the cell body dividing into dendrites that carry nerve impulses
  3. axon - carries nerve impulses away from the cell body
  4. schwann cells - surround the axon, provide electrical insulation, carry out phagocytosis (removal of cell debris) and nerve regeneration
  5. myelin sheath - forms covering of the axon made up of membranes of schwann cells
  6. nodes of ranvier - gaps between adjacent schwann cells where there is no myelin sheath, part of saltatory conduction
19
Q

what are the adaptations of a myelinated motor neurone

A
  1. presence of schwann cells means that saltatory conduction is able to occur where electrical impulses jump from one node to the next, speeding up the conduction of impulses and its transfer from one cell to another
  2. neurone cell bodies contain dendrites, so they can connect to many other neurones and receive impulses from them, forming a network for easy communication
  3. nodes of ranvier contain a lot of Na+ and K+ ion channels so depolarisation can only occur in the nodes
  4. highly branched dendrites provide a large surface area for axon terminals of other neurones
20
Q

describe saltatory conduction

A

where an action potential jumps between nodes of ranvier, speeding up transmission of nerve impulses

21
Q

what is the resting potential

A

when the inside of the axon has a negative electrical potential compared to outside the axon

22
Q

what two factors contribute to establishing and maintaining the resting potential

A
  1. active transport of Na+ and K+
  2. differential membrane permeability
23
Q

outline how a resting potential is established via the sodium-potassium pump

A

active transport of Na+ and K+:

  • carrier proteins actively transport 3 sodium ions out of the axon for every 2 potassium ions that are actively transported in
  • against the concentration gradient
  • using the hydrolysis of ATP
  • there is a larger concentration of positive ions outside the axon than there is inside the axon
  • the movement of ions via the sodium-potassium pump establishes an electrochemical gradient
24
Q

why does oxygen consumption increase when a neurone transmits a series of impulses

A
  • more respiration
  • more ATP released
  • for active transport of ions in the sodium-potassium pump
25
Q

outline how a resting potential is established via differential membrane permeability

A
  • cell surface membrane of neurones contains selective protein channels that allow sodium and potassium ions to move across the membrane via facilitated diffusion
  • protein channels are less permeable to sodium ions than potassium ions, so there is a high concentration of potassium ions inside the axon
  • potassium ions diffuse down their concentration gradient out of the axon at a faster rate than sodium ions
26
Q

list the mechanisms that take place when an action potential is generated

A
  1. stimulus
  2. depolarisation
  3. repolarisation
  4. hyper polarisation
  5. resting potential
27
Q

outline the stimulus in generating an action potential

A
  • excites neurone cell membrane opening Na+ channels
  • membrane becomes more permeable to sodium
  • Na+ diffuse into neurone down electrochemical gradient
  • makes inside of neurone less negative
28
Q

outline depolarisation in generating an action potential

A
  • potential difference reaches the threshold
  • more sodium ion channels open
  • more sodium ions diffuse rapidly into neurone
29
Q

outline repolarisation in generating an action potential

A
  • voltage-gated sodium ion channels close
  • voltage-gated potassium ion channels open
  • membrane is more permeable to potassium so K+ diffuses out of neurone down concentration gradient via facilitated diffusion
30
Q

outline hyperpolarisation in generating an action potential

A
  • K+ voltage gated channels are slow to close so there is an overshoot of potassium ions out of neurone
  • potential difference becomes more negative than resting potential
31
Q

outline resting potential in generating an action potential

A
  • ion channels are reset
  • sodium-potassium pump returns membrane to resting potential
32
Q

explain the all-or-nothing principle

A
  • once the threshold is reached, an action potential will always fire with the same change in voltage, no matter how big the stimulus is.
  • if the threshold isn’t reached, an action potential won’t fire
  • bigger stimulus won’t cause a bigger action potential, but it will cause them to fire more frequently
33
Q

describe the importance of the refractory period

A
  • ensures that action potentials are discrete events - new action potentials are generated further along the axon rather than behind the original action potential
  • ensures that action potentials are unidirectional
  • impulses only travel in 1 direction, ensures efficient transmission of nerve impulses
34
Q

list the factors that affect a neurones conductance

A
  1. myelination
  2. diameter of the axon
  3. temperature
34
Q

list the factors that affect a neurones conductance

A
  1. myelination
  2. diameter of the axon
  3. temperature
35
Q

explain how myelination affects a neurones conductance

A
  • myelin sheath is an electrical insulator that increases the speed of conduction
  • in myelinated neurone, depolarisation only occurs in the nodes of ranvier which contain sodium ion channels. the neurone’s cytoplasm conducts enough electrical charge to depolarise the next node, so impulses jump node to node
  • in non-myelinated neurone, impulse travels as a wave along the whole length of the membrane, this makes it slower
36
Q

explain how the diameter of an axon affects a neurones conductance

A
  • action potentials are conducted quicker along axons with bigger diameters because there is less resistance to the flow of ions than in the cytoplasm of a smaller axon
  • with less resistance depolarisation reachers other parts of the neurone cell membrane quicker
37
Q

explain how temperature affects a neurones conductance

A

speed of conduction increases as temperate increases because ions diffuse faster

38
Q

explain how temperature affects a neurones conductance

A

speed of conduction increases as temperate increases because ions diffuse faster

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