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Biology > Nervous and hormonal control (8.1-8.7) > Flashcards

Nervous and hormonal control (8.1-8.7) Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Sensory neurone

A

​A type of neurone that transmits impulses from receptors to relay neurones in the CNS.

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2
Q

Motor neurone

A

Carries impulses from relay/sensory neurones to effectors (muscles/glands)

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3
Q

Relay neurone

A

​A type of neurone that exists in the CNS and connects sensory neurones with motor neurones.

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4
Q

Structure of motor neurone

A

Cell body (situated in CNS) at one end and dendrites at the other

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5
Q

Structure of sensory neurone

A

Cell body on stalk with dendron and axon either side

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6
Q

Structure of relay neurone

A

Cell body in between axon with dendrites at both ends

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7
Q

Neurones

A

Individual nerve cells that conduct impulses in one direction only

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8
Q

Nerves

A

Bundles of neurones protected by a sheath

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9
Q

Myelination

A

The formation of a myelin sheath around nerve cells by Schwann cells
It causes saltatory conduction, allowing impulses to travel faster

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10
Q

Schwann cells

A

Cells that form the myelin sheath around nerve cells in the peripheral nervous system.
Contain myelin which insulates the axon, leading to saltatory conduction

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11
Q

Reflex

A

A rapid involuntary response to a stimuli

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12
Q

Why are reflex arcs important

A

Protect the body from harm
Fast response time
Involuntary

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13
Q

What type of nervous system is the pupil reflex controlled by

A

Autonomic nervous system

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14
Q

Stages of pupil contraction

A

High light intensity detected by photoreceptors on retina
Electrical impulse arises
Passes along sensory neurone to the optic nerve to the brain
The impulse travels down a parasympathetic neurone to a motor neurone
To the circular muscles which contract and decreases the pupil aperture

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15
Q

Pupil dilation stages

A

Low light intensity detected by photoreceptors on retina
Electrical impulse arises
Passes along sensory neurone to optic nerve
Impulse travels down sympathetic neurone to a motor neurone
To the radical muscle which contract and increase pupil aperture

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16
Q

Where are Na+ transported by co transporter pumps

A

out of the cell/axon

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17
Q

Where are K+ transported by co transporter pumps

A

Into the cell

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18
Q

Dendron

A

​An extension from a nerve cell that carries impulses towards the cell body.

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19
Q

Axon

A

An extension from a nerve cell that carries impulses away from the cell body.

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20
Q

Stimulus

A

A change in internal or external conditions which brings about a response.

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21
Q

Receptor

A

A structure which acts as a transducer by detecting changes in the environment and converting them into electrochemical impulses

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22
Q

Effector

A

A muscle or gland which produces a response to a stimulus.

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23
Q

Pupil

A

The hole in the centre of the iris which can contract and dilate using the iris to alter the amount of light which contacts the retina.

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24
Q

Iris

A

The pigmented muscular ring that surrounds the pupil and controls its diameter

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25
Q

Retina

A

​The structure at the back of the eye which is composed of photoreceptors and is specialised to detect light

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26
Q

Saltatory conduction

A

When the nerve impulse jumps from node to node, due to the myelinated sections of the neurone blocking the electrical impulse, it is extremely fast

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27
Q

Nodes of Ranvier

A

Unmyelinated sections of nerve cells which allow for the propagation of an action potential due to their clusters of voltage gated Na+ channels

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28
Q

Depolarisation

A

The rapid influx of sodium ions into the cell which cause it to lose its negative charge and the membrane potential to increase.

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29
Q

Hyperpolarization

A

​The drop in membrane potential below the resting potential after repolarization due to open potassium ion channels.

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30
Q

Resting potential

A

When there is a point of electro chemical equilibrium so no ions are diffusing in or out of the neurone
Usually occurs at around -70mV

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31
Q

Acetylcholine

A

A neurotransmitter used in the parasympathetic nervous system
Removed from the cleft by enzyme, acetylcholinesterase

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32
Q

Synapse

A

​The junction between two nerve cells or a nerve cell and an effector.

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33
Q

Neurotransmitter

A

​A chemical which diffuses across the synaptic gap to stimulate other neurones or effector cells.

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34
Q

All-or-nothing principle

A

If the threshold is reached then the impulse will fire at the same voltage, amplitude and duration
All action potentials are equal and there is not want of controlling the degree of of depolarisation

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35
Q

Rods

A

A type of photoreceptor found in the retina which is specialised to work in dim light.

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36
Q

Rhodopsin

A

​A protein found in rod cells that converts dim light into an electrochemical
impulse.

37
Q

Opsin

A

​A GPCR that forms part of rhodopsin along with retinal and is involved in converting detected photons into electrochemical signals

38
Q

Retinal

A

A protein that makes up rhodopsin along with opsin and forms the light sensitive part of the complex.

39
Q

Phytochrome

A

Light sensitive pigments found in plants used to detect changes to external light conditions.

40
Q

IAA

A

A type of auxin mainly produced at growing plant tips which is used to promote cell growth and elongation

41
Q

Action potential stages

A
  • Stimulus excites the neurone membrane causing voltage gated NA+ channels to open
  • NA+ diffuse into axon down their electrochemical gradient making inside of the axon less
    negative - DEPOLARISATION
  • When the potential difference reaches the threshold potential of around -50mV then more NA+
    ions move in triggering more NA+ channels to open
  • Depolarisation continues until the potential difference has been reversed from -70mV to +40mV
    (action potential)
  • The NA+ channels close and voltage gated K+ channels open
  • K+ ions diffuse out of axon causing REPOLARISATION
  • The voltage gated K+ channels return the membrane to its resting potential
42
Q

Refractory period

A

The time taken to return from the peak to the resting potential

  • This gives a delay between impulses
  • Ensures that impulses only travel in one direction so the membrane in the refractory period cannot be depolarised
43
Q

What is the intensity of the stimulus determined by

A
  • Frequency of impulses

- Number of neurones in a nerve that are conducting impulses

44
Q

What is the speed of conduction determined by

A

Determined by axon diameter

  • Travels faster along larger diameter axons
  • There is less resistance to ion flow in the cytoplasm
  • So depolarisation reaches other parts of the cell membrane quicker - There is less leakage of ions back across the membrane
45
Q

Myelin

A

Acts as an electrical insulator

Stops the diffusion of Na+ and K+ ions

46
Q

Impulse travelling along synapse stages

A
  • Action potential arrives at the synaptic knob which causes the opening of voltage gated ion channels
  • The influx of ions causes the vesicles continuing neurone transmitters to move and fuse with the presynaptic membrane
  • Released neurotransmitters diffuse across the synaptic cleft and bind to complementary receptors on the post synaptic membrane
  • The binding of the neurotransmitters increase the permeability of the post synaptic neurone to NA+
  • This initiates depolarisation of post synaptic neurone
47
Q

What are neurotransmitters inactivated by

A
  • Taken back up presynaptic knob
  • Broken down by enzymes and reabsorbed
  • Diffuse away and taken up by another neurone
48
Q

Why do neurotransmitters have to be removed

A

So that there is not a prolonged action potential and so that the receptors are available for future use

49
Q

Excitory synapses

A

Associated with a process called summation
They make the post synaptic membrane more permeable to NA+ but sometimes a single impulse is not enough to cause neurotransmitters to be released so no AP is formed so summation has to occur

50
Q

Inhibitory synapses

A

Block transmission making a generation of an impulse less likely
This occurs when neurotransmitters open up different ion channels that are not NA+ This leads to hyperpolarisation which makes it difficult to depolarise the membrane

51
Q

Summation

A

Adding together the effects of a number of weak AP at a synapse to reach a threshold because sometimes there isn’t enough neurotransmitters diffusing across to reach the threshold and bring about an action potential

52
Q

Spacial summation

A

The convergence of a number of presynaptic neurones and synapses and one synaptic neurone Needs enough neurotransmitters to diffuse across to achieve an AP

53
Q

Temporal summation

A

Where a single presynaptic neurone fires a number of times in quick succession so that the neurotransmitters build up in the synaptic cleft

54
Q

What reflex are the circular muscles controlled by

A

Parasympathetic because they relax to let in more light

55
Q

What reflex are radial muscles controlled by

A

Sympathetic reflex, because they contract to let in more light

56
Q

Stages of pupil constriction

A
  • High light intensity detected by photoreceptors on retina
  • Electrical impulse arises
  • Passes along sensory neurone to the optic nerve to the brain
  • The impulse travels down a parasympathetic neurone to a motor neurone - To the circular muscles which contract and decreases the pupil aperture
57
Q

stages of pupil dilation

A
  • Low light intensity detected by photoreceptors on retina
  • Electrical impulse arises
  • Passes along sensory neurone to optic nerve
  • Impulse travels down sympathetic neurone to a motor neurone
  • To the radical muscle which contract and increase pupil aperture
58
Q

Structure of retina

A

Consists of 2 layers

- Photoreceptor cells (roads and cones) at the back - Neurones at the front connecting to the topic nerve

59
Q

Cones

A

Located in the fovea and used to detect colour and in high visual acuity

60
Q

Photoreception in rod cells in light

A
  • When rhodopsin absorbs light the retinal component changes shape
  • The rhodopsin breaking down into retinal and opsin
  • The opsin binds to the cell surface membrane and activates a cascade of reactions that close
    the cation channels and decrease the permeability of the plasma membrane
  • Therefore less NA+ ions can diffuse into the rod cell
  • This leads to a change in the potential difference of the rod membrane which becomes
    hyperpolarised
  • If the hyperpolarisation is large enough then no neurotransmitter is released and the bipolar cell
    membrane depolarises and an action potential is sent to the sensory neurone of the optic nerve
61
Q

Photoreception in rod cells In the dark

A
  • NA+ diffuse into the outer segment of the rod cell via non specific cation channels
  • NA+ diffuses within the rod cell down its concentration gradient to the inner segment where
    sodium ions are continuously and actively pumped out of the cell
  • The influx of NA+ causes there membrane to be slightly depolarised
  • The neurotransmitter binds to the bipolar cells stopping its membrane from depolarising leading
    to no action poetical in the optic nerve
62
Q

Plant growth substances

A

Used for when a stimuli needs to bring about a direction of growth Produced in the apical meristem regions
Transported by diffusion or the phloem

63
Q

How IAAs stimulate cell elongation

A
  • Produced in the meristem and diffuses away from the tip building up a zone of elongation - Results in active transport of H+ into the cell wall
  • This acidification of the cell wall weakens the H bonds and weakness the cell wall
  • This also increases the potential difference across the cell - Water molecules enter as a result by osmosis
  • Turgor pressure increases and the cell elongates
64
Q

How phytochrome and IAAs alter development in plants

A
  • They bind to receptors in target cells or interact with other proteins/enzymes
  • This leads to the activation of intracellular second messenger signal molecules
  • Pfr can directly enter the nucleus and bind to transcription factors
  • The second messenger molecules enter the nucleus and activate transcription factors which
    bind to DNA
  • Leads to transcription of light regulated genes
  • The proteins translated lead to metabolic changes that result in response
65
Q

What reflex are radial muscles controlled by

A

Sympathetic reflex

66
Q

What reflex are the circular muscles controlled by

A

Parasympathetic reflex

67
Q

Why is the resting potential of a cell -70mV

A

The co transporter pumps move 3 Na+ out of the neurone for every 2 K+ moved in

68
Q

Why do K+ ions move back into the neurone

A

The membrane is around 50X more permeable to K+ ions than Na+ ions so K+ passively diffuses back down its concentration gradient
Co transporter pumps also transport K+ back into the neurone

69
Q

Action potential

A

The change in potential difference across an axon membrane which occurs during the passage of a nerve impulse, where the inside becomes more positive than the outside

70
Q

Refractory

A
71
Q

Why do action potentials move in only one direction

A

The refractory period ensures that Na+ channels behind the action potential don’t open and trigger depolarisation, instead the Na+ channels ahead of the action potential are stimulated to open

72
Q

Role of mitochondria in the synapse

A

Pumps the ions back across the membrane to reset the knob

73
Q

Importance of synapses

A

Control the nerve pathways (allowing for flexibility) and integrate information from different neurones (allowing coordinated responses)

74
Q

How do synapses achieve flexible and coordinated responses

A

They are unidirectional (one direction)
They filter out low levels of stimuli
They are modifiable
Involved with divergence

75
Q

Unidirectional

A

Travel in one direction

76
Q

Filtration of stimuli

A

There is a maximum level of stimulation before a neurotransmitter is released

77
Q

Modifiable

A

Synaptic connections are not fixed especially to the CNS

78
Q

Divergence

A

A single stimuli in one neurone results in a number of complex responses in several other neurones

79
Q

Convergence

A

Where several stimuli come together to cause one single response

80
Q

Receptor for light

A

Photoreceptors

81
Q

Receptor for stretching and compression

A

Mechanoreceptors

82
Q

Receptors for temperature

A

Thermoreceptors

83
Q

Receptors for chemicals

A

Chemoreceptors

84
Q

How does an electrical impulse arise

A

The stimulus causes a change in the permeability of the receptor membrane to Na+, and the receptor is able to convert the energy of the stimulus into electrical energy of the nerve impulse

85
Q

Nature of receptors

A

Specific so only respond to one stimulus

86
Q

Structure of the retina

A

Inverted and consisting of 2 layers, with rods and cones at the back, and neurones in front of them

87
Q

Structure of rod cells

A
88
Q

Photoperiodism

A

Plant response to light duration

89
Q

Phytochrome

A

The light sensitive pigment found in plants

Biology (18 decks)

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