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Biology 9.2 > The mammalian nervous system > Flashcards

The mammalian nervous system Flashcards

1
Q

What is the nervous system made up of

A

Interconnected neurons specialized for the rapid transmissions of impulses throughout the body

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2
Q

What do neurons carry

A

Impulses from special receptor cells and specialized effector cells

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3
Q

Where are sense organs

A

Eyes, ear

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4
Q

What are sensory neurons

A

Neurons that only carry information from the internal or external environment into the central processing areas of the nervous system

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5
Q

What happens as animals increase in size and complexity

A

They develop more specialized concentrations of nerve cells, which form the central nervous system

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6
Q

What is the central nervous system (CNS)

A

Incoming information from sensory neurons is processed, and from where impulses are sent out through motor neurons

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7
Q

Where is the CNS in vertebrates

A

Brain and spinal cord

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8
Q

What are neurons made up of

A

Individual cells and each one has a long nerve fibre that carries the nerve impulse

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9
Q

What are nerves

A

Bundles of nerve fibres called axons and dendrons

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10
Q

What are:
motor nerves
sensory nerves

A

Nerves that only carry motor fibres

Nerves that only carry sensory fibres

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11
Q

What is the peripheral nervous system (PNS)

A

The parts of the nervous system that are not within the central nervous system

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12
Q

What are neurons

A

The basic unit of a nervous system

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13
Q

What are nerve impulses

A

Neuron cells specialized in the transmission of electrical signals

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14
Q

What is the structure of a neuron

Why does it contain these components

A 
The cell body contains:
cell nucleus 
mitochondria 
RER
Needed for the synthesis of the neurotransmitter molecules
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15
Q

What are dendrites

What does it do

A

The cell body of the neurons have slender finger-like processes
connects to the neighboring nerve cells

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16
Q

What is the most distinctive feature on a nerve cell

How does it look

A

Nerve fibre

extremely long and thin and carries the nerve impulse

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17
Q

What are axons

A

Fibres that carry impulses away from the nerve cell body

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18
Q

What are dendrons

A

Fibres that transmit impulses towards the cell body

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19
Q

What connects the motor and sensory neurons

A

Short relay neurons that are found in the CNS

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20
Q

What does a Schwann cell do

What is a myelin sheath

A

The membrane wraps itself repeatedly around the nerve fibre, forming a fatty layer known as a myelin sheath

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21
Q

What are the nodes of Ranvier

A

Gaps between the Schwann cell

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22
Q

Give two reasons why the myelin sheath is important

A

1) It protects the nerves from damage

2) Speeds up the transmission of nerve impulse

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23
Q

What is the role of the nervous system

A

To quickly carry electrical impulses from one area of the body to another

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24
Q

What two factors do the speed at which impulses can be carried in the nervous system depend on

A

1) Diameter of the nerve fibre (The thicker the fibre, The more rapidly impulses travel)
2) Presence or absence of the myelin sheath (myelinated nerve fibes carry impulses faster)

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25
Q

Which of the two don’t have myelin sheath on the nerves:
Invertebrates
Vertebrates

A

Invertebrates hence the reason they travel so slow

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26
Q

In Vertebrate animals which neurons are myelinated

and which are unmyelinated

A

Voluntary motor neurons

Autonomic neurons

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27
Q

What is one of the most effective ways you can investigate nerve impulses

A

Nerve impulses are electrical so to record and measure the tiny electrical changes

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28
Q

What is the basis of nerve impulse

A

The fact that the concentration of sodium ions, potassium ions, and other charged particles outside the axon is different from the inside

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29
Q

Is the membrane of the axon permeable

A

YES

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30
Q

What gives the axon its special conducting properties

A

The difference in permeability of this membrane to positively charged sodium and potassium ions

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31
Q

Explain the partial permeability of the axon membrane

A

It’s impermeable to the sodium ions but quite freely permeable to potassium ions

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32
Q

When is the axon ‘at rest’

A

When it is not conducting a nerve impulse

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33
Q

What’s greater than the concentration in the cytoplasm of the axon

A

The extracellular concentration of ions

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34
Q

How is the gradient in the axon created

A

By a very active sodium/potassium ion pump

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35
Q

What enzyme does the sodium/potassium pump have and how does this help

A

Na+/K+ ATPase that uses ATP to move sodium ions out of the axon and potassium ions in

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36
Q

What is a resting potential

A

The potential difference across the membrane of around -70mV

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37
Q

What is the key event when an impulse travels along an axon

A

A change in the permeability of the cell membrane to sodium ions

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38
Q

What causes a change in the permeability of the cell membrane to sodium ions

A

Either response to a stimulus or the arrival of a neurotransmitter in a motor neuron

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39
Q

What happens when a neuron is stimulated

A

The axon membrane shows a sudden or dramatic increase in its permeability to sodium ions

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40
Q

When sodium gates open what does it allow to happen

A

Allows sodium ions to diffuse rapidly down their concentration and electrochemical gradient

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41
Q

How long does the depolarisation last

A

A millie second

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42
Q

What is the action potential

A

The potential difference across the membrane at this point

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43
Q

What happens at the end of the depolarization

A

Sodium ion channels close again and excess sodium ions are rapidly pumped out by the active sodium pump

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44
Q

Why do potassium ion channels open

A

As a result of repolarisation

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45
Q

What happens as a result of repolarisation

What happens to the axon after this

A

Potassium ions diffuse out of the axon down the concentration gradient and an electrochemical gradient attracted by the negative charge on the outside of the membrane
The axon becomes negatively charged relative to the outside

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46
Q

How can the event of the action potential be recorded

A

It can be recorded clearly using the internal/external electrode combinations you already have

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47
Q

What is the threshold for any nerve fibre

A

The point when sufficient sodium ion channels open for the rush of the sodium ions into the axon to be greater than the outflow of potassium ions

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48
Q

What happens once the threshold is reached

A

The action potential occurs

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49
Q

What is the refractory period

A

The time it takes for an area of the axon membrane to recover after an action potential, that is the time it takes for ionic movements to repolarise the membrane and restore the resting potential

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50
Q

What does the refractory period depend on

A

Both on the sodium/potassium pump and the membrane permeability to potassium ions.

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51
Q

What happens after the first millisecond or so after the action potential
What is this known as

A

it is impossible to restimulate the fibres
the sodium channels are completely blocked and the resting potential has not been restored
This is known as the absolute refractory period

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52
Q

What is the relative refractory period

A

After the absolute refractory period, there is a period where the action potential is restored for a millisecond and the threshold has been effectively raised

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53
Q

Why is the refractory period important in the functioning of the nervous system

A

It limits the rate at which impulses may travel to 500-1000 per second
ensures impulses flow in one direction along nerves

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54
Q

What cannot take place until the resting potential is restored?

A

The part of the nerve fibre that impulse has just left cannot conduct another impulse

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55
Q

What happens once the action potential is set up in response to the stimulus

A

It will travel the entire length of the nerve fibre

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56
Q

What is the movement of the nerve impulse along the fibre a result of

A

Local currents set up by the ion movements at the action potential itself

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57
Q

Why can’t the sodium ion channels behind the action potential open

A

Due to the refractory period of the membrane behind the spike

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58
Q

Where can ions pass through in the myelinated neurons

What does this mean

A

The node of Ranvier

This means that action potential can only occur at the nodes

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59
Q

What is the Saltatory conduction

A

Speed up the transmission as the ionic movements associated with the action potential occurs much less frequently, taking less time

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60
Q

Where must receptors pass their information

A

The sensory nerves, which in turn must pass the information to the CNS

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61
Q

What happens wherever two neurons meet

A

They are linked by a synapse

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62
Q

What is every cell in CNS covered with

A

Synaptic knobs from other cells

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63
Q

What increases the permeability of the presynaptic membrane to calcium ions as calcium ion channels open up

A

The arrival of an impulse at the synaptic knob

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64
Q

What is the effect of the influx of calcium ions

A

to cause the synaptic vesicles to move to the presynaptic membrane

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65
Q

What do some of the vesicles fuse with

A

The presynaptic membrane and release the transmitter substance into the synaptic cleft.

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66
Q

What opens the sodium channels

A

Molecules diffuse across the gap and become attached to specific protein receptor sites on the sodium channels of the post-synaptic membrane

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67
Q

What are the excitatory post-synaptic potentials (EPSP)

A

The potential difference across the post-synaptic membrane caused by an influx of sodium ions into the nerve fibres, as the result of the arrival of a molecule of a neurotransmitter on the receptors of the post-synaptic membrane that makes the inside more positive than the normal testing potential, increasing the chance of a new action potential

68
Q

What are the inhibitory post-synaptic potentials (IPSP)

A

The potential difference across the post-synaptic membrane caused by an influx of negative ions as a result of the arrival of a molecule of neurotransmitters on the receptors of the post-synaptic membrane that makes the inside more negative than the normal testing potential, decreasing the chance of a new action potential

69
Q

What is one of the most common neurotransmitters found in humans

A

acetylcholine (ACh)

70
Q

Where is acetylcholine (ACh) synthesized

A

In the synaptic knob using ATP produced in the many mitochondria present

71
Q

What are cholinergic nerves

A

Nerves using acetylcholine as their transmitters

72
Q

What happens to the acetylcholine once it has done its job

A

It is rapidly hydrolyzed by the enzyme acetylcholinesterase

73
Q

What happens once the neuroreceptors have bounded to the receptor and initiated a response
What does it ensure

A

It is rapidly hydrolysed into acetate and choline.

That it no longer affects the postsynaptic membrane and releases the components to be recycled

74
Q

Where do the components rapidly diffuse

A

Across the synaptic cleft down a concentration gradient and are taken back to the synaptic knob through the presynaptic membrane

75
Q

What happens in the presynaptic membrane

A

They are resynthesized into more acetylcholine

76
Q

What is Acetylcholine

A

The neurotransmitter in all motor neuron, the parasympathetic nervous system, and cholinergic synapses in the CNS

77
Q

What does nicotine do

A

Mimics the effect of acetylcholine and binds to specific acetylcholine receptors in post-synaptic membranes known as nicotinic receptors

78
Q

What does nicotinic receptors trigger

A

An action potential in the post-synaptic neuron, but then the receptors remain unresponsive to more stimulation for some time

79
Q

What does nicotine cause

What does it trigger

A

Causes raised heart rate and blood pressure

The release of another type of neurotransmitter in the brain called dopamine

80
Q

What is dopamine associated with

A

Pleasure sensations

81
Q

Is nicotine bad at high doses only

A

No even at low it releases a large amount of dopamine and still has a big effect on your acetylcholine

82
Q

What is Lidocaine and when is it used?

A

A drug used as a local anesthetic

commonly used by dentists when drilling or removing a tooth

83
Q

What does Lidocaine do

what two things does it prevent

A

Block voltage-gated sodium channels, preventing the production of an action potential in sensory nerves and so preventing you from feeling pain

84
Q

What does Lidocaine block

A

It blocks sodium channels, raising the depolarization threshold

85
Q

What is cobra venom

A

A substance made by several species of a cobra that is toxic and often fatal in snake bite

86
Q

What does Cobra venom do?

A

It binds reversibly to the acetylcholine receptors in the post-synaptic membrane and neuromuscular junctions between motor neurons and muscles. Makes people paralyzed as a result

87
Q

What happens once the toxin from cobra venom reaches the muscles involved in breathing

A

You will die

88
Q

Is cobra venom always bad

A

No, in low concentrations it can relax the muscle of the trachea and bronchi in severe asthma attacks

89
Q

What do sensory receptors play a vital role in

A

Providing an animal with information about both its internal and external environment

90
Q

What are simple sensory receptors

A

Neurons with a dendrite that is sensitive to one particular stimulus

91
Q

What happens when the dendrite in simple sensory receptors receive a stimulus
What is this type of cell known as

A

Chemical events occur that result in an action potential in the nerve fibre of the neuron
Primary receptor

92
Q

What is a secondary receptor

A

It consists of one or more completely specialised cells that are sensitive to a particular type of stimulus

93
Q

What do secondary receptor cells do

Give an example of a secondary receptor

A

These cells synapse with a normal sensory neuron, which carries the impulse to the central nervous system
The retinal cells in the retina of the eye

94
Q

What happens to the sensory systems as animals become more complex

A

The sensory systems are more complex

95
Q

What do receptor cells have

A

A resting potential that depends on maintaining the charge of the cell interior negative in relation to the outside, by using membrane sodium pumps

96
Q

What happens when receptor cells receive a stimulus

What does this generate

A

Sodium ions move rapidly across the cell membrane along with concentration and electrochemical gradient, and this sets up a generator potential

97
Q

What happens if the generator potential is not large enough

A

There will be no action potential, the action potential obeys the all or nothing rule whereas the general potential doesn’t

98
Q

What is the common process in most sensory receptors

A

Stimulus –> Local change –> Gernerator —-> action

in permeability potential potential

99
Q

What happens if the generator potential for a single receptor cell is insufficient to set up a synapse
What is this known as

A

The potential from several may add together or summate and trigger an action potential
Convergence

100
Q

What is Convergence useful for

A

It is a useful adaption for increasing the sensitivity of a sensory system to low-level stimuli

101
Q

What does a weak stimulus result in

A

A low frequency of action potentials along a sensory neuron

102
Q

What does a strong stimulus result in

What happens as a result of this

A

A rapid stream of action potentials being fired along the sensory neuron
The axon obeys the all or nothing rule in terms of action potential

103
Q

What is our eye sensitive to

What does this allow

A

EM radiation with a wavelength of 400-700nm

It allows clear and sophisticated vision

104
Q

What does the retina do

A

.Focusing light

.Preceive the light and provide the brain with info needed to make sense of the image

105
Q

What does the retina contain

What are the two main ones

A

Photoreceptors (light-sensitive cells)

Rods and cones

106
Q

What are rods and cons described as

A

Secondary exteroceptors- they signal changes in the external environment

107
Q

Where are there no rods

A

In the fovea

108
Q

What do rods provide

What are they mainly used for

A

Greyscale vision

To see low light intensities or at night

109
Q

Why do rods not give clear vision

A

They are not tightly packed together and several of them synapse with the same sensory neuron

110
Q

What can trigger an action potential to the CNS

A

Several small generator potentials

111
Q

Where are cones found

How many cones are there

A

They are found tightly packed together in the fovea

6 million cones

112
Q

What are cones

A

They are receptors in the retina that are used mainly for vision in bright light and they also provide color vision

113
Q

Why do cones provide a great visual acuity in bright lights

A

They have tight packing in the fovea and has its own sensory neurons

114
Q

Why is the arrangement of the retina seen as weird

A

It appears to be arranged back to front

115
Q

Explain the structure of the retina

A

The outer segments are next to the choroid, and the neurons are the interior edge of the eyeball
The light needs to pass through the synapses and the inner segments before reaching the outer segments containing visual pigments.

116
Q

What is the reason for the weird arrangement of the retina

A

The origin of the retinal cells in the embryo and the way in which the eye is formed during the embryonic development

117
Q

What is the visual pigment in the rod

What is it formed from

A

rhodopsin (visual purple)

opsin and retinal

118
Q

What is Opsin

A

A lipoprotein and retinal is a light-absorbing derivative of vitamin A

119
Q

What two forms of retinal exists

What form is it in the dark

A

cis-retinal and trans-retinal

In the cis form in the dark

120
Q

What happens to the cis-retinal when a small unit of light hits it
What effects does it have

A

It converts the cis-retinal to trans-retinal

It changes the shape of the retinal and puts a strain the bonding between the retinal and opsin

121
Q

What are rod cell membranes permeable to

A

Sodium Ions

122
Q

What is bleaching

A

The breaking up of the molecule rhodopsin

123
Q

Explain how rods work?

What is hyperpolarisation known as

A

1) Sodium ions move into the rod cells through Sodium ion channels, and sodium pump moves them out again
2) When rhodopsin is bleached, it triggers a cascade of reactions that results in the closing of the sodium ion channels, so the rod cell membranes become much less permeable to sodium ions and fewer sodium ions diffuse into the cell
3) The sodium pump continues to work at the same rate, pumping sodium ions out the rod cell, so the interior becomes more negative than usual.
4) This hyperpolarisation is known as the generator potential in the rod

124
Q

What does the size of the general potential depend on

A

The amount of light hitting the rod, and therefore the amount of rhodopsin bleaching that takes place

125
Q

What happens if the general potential is large enough to reach the threshold
What is then set up

A

Neurotransmitter substances are released into the synapse with the bipolar cell
An action potential is then set up

126
Q

What forms the optic nerve leading to the brain

A

All the sensory neurons leave the eye at the same point to form the optic nerve

127
Q

Once the visual pigment has been bleached, When can the rod be stimulated

A

The rods cannot be stimulated again until the rhodopsin is resynthesised

128
Q

How do you convert the trans-retinal back to cis-retinal

A

ATP produced by the mitochondria in the inner segment of the rod to convert the trans-retinal to cis-retinal and rejoin it to the opsin to form rhodopsin again

129
Q

Why can’t rods respond to daylight

A

They are almost entirely bleached

130
Q

What is the Cods visual pigment

A

iodopsin

131
Q

How many types of iodopsin are there and what are they sensitive to

A

Three

Sensitive to one of the primary colors of light

132
Q

How can iodopsin be broken down

A

If it hit it with light that has more energy than rhodopsin

133
Q

How do cones provide color vision

A

The brain interprets the number of different types of cones stimulated by different colors

134
Q

How did the brain form

A

As a swelling in the hallow neutral tube at the front or anterior end of a vertebrate embryo that folds back on itself

135
Q

What are the three distinct areas of the brain

A

Forebrain, midbrain, and hindbrain

136
Q

Why is the brain hard to see

A

The cerebrum is folded back over the entire brain

137
Q

What is the brain made up of

A

Made up of a combination of grey matter, neuron cell bodies, and white matter

138
Q

What does the brain contain

A

Centers or nuclei made up of cell bodies that make intercommunication between million of cells possible

139
Q

What does the nerve from the spinal cord do and why

A

They cross over as they enter and leave the brain so that the left-hand side of the brain receives information from and control the righthand side of the body and vice versa

140
Q

What does cerebrum consist of

A

Two cerebral hemispheres

141
Q

How is the cerebrum described

A

The biggest and developer of the human brain

142
Q

What abilities does the cerebrum give us

A

See, think learn and feel emotions

143
Q

What does the cerebrum control

A

Our motor function (all the conscious movements)

144
Q

Whats the outer layer of the cerebral and explain the structure

A 
Cerebral cortex
2-4nm thick
made up of grey matter
nerve cell bodies
dendrites
synapses
deeply folded to give a large surface area 
divided into lobes eg: frontal lobe
145
Q

What is the corpus callosum

A

The left and right cerebral hemisphere are connected by a band of axons known as the corpus callosum

146
Q

What does the hypothalamus do in the brain

A

Coordinates the autonomic nervous system and plays a major role in thermoregulation (Regulation of core temperature of the body)
monitors chemistry of the blood
controls hormone secretion in the pituitary gland
Controls thirst, hunger, aggression and reproductive

147
Q

What does the medulla oblongata do

A

The most primitive part of the brain

contains reflux centers that control functions such as breathing rate, heart rate, blood [presusre and saliva production

148
Q

What is the spinal cord

A

A tube made up of a core of grey matter surrounded by white matter, which runs out from the base of the brain through the vertebra
Approx. 43-45cm

149
Q

What is an important function that the spinal cord carries out

A

Important coordination centre in its own right

150
Q

What are most of the actions in the complex animal result of

A

Result of the unconscious reflux actions

151
Q

Give examples of human refluxes

A

Touching something hot and moving your hand

blinking when something goes in your eye

152
Q

What are reflex arcs

A

They are nerves that control unconditioned reflexes

153
Q

What is the function of the reflex arc

A

To bring about an appropriate response to a particular stimulus as rapidly as possible without the time delay that occurs when the conscious centers become involved

154
Q

What are the two main reflexes

A 
spinal reflexes (hand moving from a hot object)
cranial reflexes (blinking, pupil reflex)
155
Q

What do the sensory nerves carry in the peripheral nervous system

A

Impulses from the receptors about changes in both the internal and external environment into the CNS

156
Q

What does the motor nerve carry in the peripheral nervous system

A

Impulses out from the CNS to the effectors of the body

157
Q

What are the two main types of motor nerves

A

The voluntary nervous system and autonomic nervous system

158
Q

What is a voluntary nervous system

A

It involves motor neurons that are under voluntary or conscious control involving the cerebrum,

159
Q

Give an example of something that is controlled by the voluntary nervous system

A

Carrying things such as a drink

160
Q

What is the autonomic nervous system

A

Involves motor neurons that are not under the control of the conscious area of the brain

161
Q

Give an example of something that is controlled by the autonomic nervous system

A

heart rate and breathing

162
Q

What can the autonomic nervous system be subdivided into

A

Sympathetic nervous system and parasympathetic nervous system

163
Q

What are the structural differences between sympathetic and parasympathetic nervous systems
What does this tell you about the fibres

A

In sympathetic, the ganglia are very close to the CNS
.Preganglionic fibres are short and postganglionic fibres are long
In parasympathetic, the ganglia are near to or in the effector organ
.Preganglionic fibres are long and postganglionic fibres are short

164
Q

What are the similarities between sympathetic and parasympathetic nervous systems

A

Myelinated preganglionic fibres leave the CNS and synapse in the ganglion with unmyelinated post-ganglionic fibre

165
Q

What are the functional differences between the sympathetic and parasympathetic nervous systems

A

Sympathetic produce noradrenaline at the synapse. It is referred to as the fight or flight response
When under physical or psychological stress the sympathetic pathway shall take over

Parasympathetic is slower and produces acetylcholine at the synapse
Restores calm after a stressful situation
it is sometimes referred to as the rest or digest system

166
Q

Give an example of how the parasympathetic and sympathetic nervous system act antagonistically

A

the sympathetic system speeds up the heart rate whereas parasympathetic slows it down

Biology 9.2 (1 decks)

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