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Biomedicine: MEDSCI142 COPY COPY > Nervous System (Textbook) > Flashcards

Nervous System (Textbook) Flashcards

1
Q

What does the cerebrum consist of?

A

1) Outer cerebral cortex
2) Internal region of cerebral white matter
3) Grey matter nuclei deep within the white matter.

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2
Q

What is the cerebral cortex?

A

A region of grey matter that forms the outer rim of the cerebrum.

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3
Q

How thick is the cerebral cortex?

A

2-4mm

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4
Q

What does the cerebral cortex contain?

A

Billions of layers of neurones

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5
Q

Why does the cortical region roll and fold in on itself?

A

During embryonic development, the grey matter of the cortex enlarges much faster than the deeper white matter.

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6
Q

What are the folds called?

A

Gyri

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7
Q

Distinguish between fissures and sulci.

A

Fissures: deepest grooves between folds.
Sulci: shallower grooves between folds.

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8
Q

What is the most prominent fissure and what does it separate?

A

Longitudinal fissure separates the cerebral hemispheres.

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9
Q

Where is the falx cerebri found?

A

Within the longitudinal fissure.

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10
Q

By what are the cerebral hemispheres internally connected by?

A

Corpus callosum.

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11
Q

Describe the corpus callosum.

A

A broad band of white matter containing axons that extend between the hemispheres.

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12
Q

List the four lobes of the cerebrum.

A

Frontal, parietal, occipital, temporal

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13
Q

What does the central sulcus separate?

A

The frontal lobe from the parietal lobe.

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14
Q

Where is the pre-central gyrus located?

A

Immediately anterior to the central sulcus.

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15
Q

What does the pre-central gyrus contain?

A

Primary motor area

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16
Q

Where is the post-central gyrus located?

A

Immediately posterior to the central sulcus.

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17
Q

What does the post-central gyrus contain?

A

Primary somatosensory area

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18
Q

What separates the frontal lobe from the temporal lobe?

A

Lateral cerebral sulcus

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19
Q

What separates the parietal lobe from the occipital lob?

A

Parieto-occipital sulcus

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20
Q

Where is the insula found?

A

Lies within the lateral cerebral sulcus, deep to the parietal, frontal and temporal lobes.

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21
Q

What does cerebral white matter consist primarily of?

A

Myelinated axons in three types of tracts.

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22
Q

What are the three types of tracts found in cerebral white matter?

A

1) Association tracts
2) Commissural tracts
3) Projection tracts

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23
Q

What do the association tracts contain?

A

Axons that conduct nerve impulses between gyri in the same hemisphere.

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24
Q

What do commissural tracts contain?

A

Axons that conduct nerve impulses from gyri in one hemisphere to corresponding gyri in the other.

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25
Q

What are the three groups of commissural tracts?

A

1) Corpus callosum
2) Anterior commissure
3) Posterior commissure

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26
Q

What do projection tracts contain? Give an example of one.

A

Axons that conduct nerve impulses from the cerebrum to lower parts of the CNS or from lower parts of CNS to cerebrum. E.g. internal capsule

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27
Q

What do the association areas of the cerebral cortex deal with?

A

More complex integrative functions such as memory, emotions, reasons etc.

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28
Q

Where do sensory impulses arrive mainly?

A

In the posterior half of both hemispheres, in regions behind the central sulci.

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29
Q

What do primary sensory areas receive?

A

Sensory information that has been relayed from peripheral sensory receptors through lower regions of the brain

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30
Q

What is usually adjacnet to the primary sensory areas?

A

Sensory association areas.

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31
Q

What do sensory association areas receive input from?

A

Both from the primary areas and from other brain regions.

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32
Q

What do sensory association areas do?

A

Integrate sensory experiences to generate meaningful patterns of recognition and awareness.

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33
Q

Where is the primary somatosensory area located?

A

Directly posterior to the central sulcus of each hemisphere in the postcentral gyrus.

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34
Q

What does the primary somatosensory area receive?

A

Nerve impulses for touch, pressure, vibration, itch, tickle, temperature, pain, proprioception

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35
Q

What is meant by sensory homunculus?

A

The size of the cortical area receiving impulses from a particular part of the body depends on the number of receptors there rather than on the size of the body part.

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36
Q

Where is the primary visual area located?

A

At the posterior tip of the occipital lobe mainly on the medial surface.

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37
Q

Where is the primary auditory area located?

A

In the superior part of the temporal lobe near the lateral cerebral sulcus.

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38
Q

Where is the primary gustatory area located?

A

At the base of the postcentral gyrus superior to the lateral cerebral sulcus in the parietal cortex.

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39
Q

Where is the primary olfactory area located?

A

In the temporal lobe on the medial aspect.

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40
Q

Where does the motor output flow mainly from?

A

The anterior part of each hemisphere.

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41
Q

Where is the primary motor area located?

A

In the precentral gyrus of the frontal lobe.

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42
Q

What is meant by the motor homunculus?

A

More cortical area is devoted to those muscles involved in skilled, complex, or delicate movement.

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43
Q

Where is Broca’s speech area located?

A

In the frontal lobe close to the lateral cerebral sulcus.

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44
Q

Where do impulses pass from Broca’s speech area?

A

To the premotor regions that control muscles of the larynx, pharynx and mouth.
Also to primary motor area, which controls breathing muscles for proper flow of air past vocal cords.

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45
Q

What does a cerebrovascular accident in Broca’s speech area result in?

A

Nonfluent aphasia: Can still have clear thoughts but unable to form words.

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46
Q

How are association areas connected?

A

By association tracts

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47
Q

Where is the somatosensory association area located?

A

Just posterior to and receives input from the primary somatosensory area, as well as thalamus.

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48
Q

What is the purpose of the somatosensory association area?

A
  • Allows you to determine shape and orientation of an object by feeling it.
  • Storage of memories of past somatic sensory experiences.
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49
Q

Where is the visual association area located?

A

In the occipital lobe.

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50
Q

What is the purpose of the visual association area?

A

Relates past and present visual experiences. Essential for recognising and evaluating what is seen.

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51
Q

What does the facial recognition area receive nerve impulses from?

A

The visual association area.

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52
Q

What is Wernicke’s area?

A

A broad region in the left temporal and parietal lobes.

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53
Q

What is the purpose of Wernicke’s area?

A

Interprets the meaning of speech by recognising spoken words.

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54
Q

What are the consequences of having CVA in Wernicke’s area?

A

Fluent aphasia: Can still speak but cannot arrange words in a coherent fashion.

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55
Q

What is meant by hemispheric lateralisation?

A

The asymmetry between the two cerebral hemispheres.

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56
Q

What is the first layer of protection for the central nervous system?

A

The hard bony skull and vertebral column.

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57
Q

What is the second protective layer of the central nervous system?

A

The meninges: three membranes that lie between the bony encasement and the nervous tissue.

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58
Q

What does the space between two of the meningeal membranes contain?

A

Cerebrospinal fluid

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59
Q

What is the cerebrospinal fluid and what does it do?

A

A buoyant liquid that suspends the central nervous tissue in a weightless environment while surrounding it with a shock absorbing, hydraulic cushion.

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60
Q

What are the three types of meninges from superficial to deep?

A

1) dura mater
2) arachnoid mater
3) pia mater

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61
Q

From where to where does the spinal cord extend in adults?

A

From the medulla oblongata, the inferior part of the brain, to the superior border of the second lumbar vertebra.

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62
Q

From where to where does the spinal cord extend in newborn infants?

A

From the medulla oblongata to the third or fourth lumbar vertebra.

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63
Q

What are the two enlargements of the spinal cord?

A

Superior enlargement: cervical enlargement

Inferior enlargement: lumbar enlargement

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64
Q

Where is the facial recognition area located?

A

In the inferior temporal lobe

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65
Q

Where is the auditory association area found and what does it allow us to do?

A

Located inferior and posterior to the primary auditory area in the temporal cortex. Recognition of a particular sound as speech, music, or noise.

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66
Q

Where is the orbitofrontal cortex found? Where does it receive impulses from? What does it allow us to do?

A

Found along the lateral part of the frontal lobe. Receives sensory impulses from the primary olfactory area. Identification of odours and discrimination.

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67
Q

What is the common integrative area bordered by? What is its purpose?

A

Somatosensory, visual, and auditory association areas. Integrates sensory interpretations for appropriate response.

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68
Q

Where is the premotor area located? What are its purposes?

A

A motor association area immediately anterior to the primary motor area. Deals with learned motor activities of a complex and sequential nature.

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69
Q

Where is the prefrontal cortex found? What is it responsible for?

A

Extensive area in the anterior portion of the frontal lobe. Makeup of personality, intellect, complex learning etc.

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70
Q

Where is the frontal eye field area located?
What is it often included in?
What does it control?

A

Frontal cortex
Premotor area
Voluntary scanning movements of the eyes.

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71
Q

Where does the spinal cord taper?

A

At a conical structure called the conus medullaris.

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72
Q

How many pairs of cervical nerves are there?

A

8 pairs

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73
Q

How many pairs of thoracic nerves are there?

A

12 pairs

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74
Q

How many pairs of lumbar nerves are there?

A

5 pairs

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75
Q

How many pairs of sacral nerves are there?

A

5 pairs

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76
Q

How many pairs of coccygeal nerves are there?

A

1 pair

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77
Q

What are the spinal nerves?

A

Paths of communication between the spinal cord and specific regions of the body.

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78
Q

What are bundles of axons called?

A

Roots

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79
Q

What do roots connect? With what do they connect with?

A

Each spinal nerve to a segment of the cord by even smaller bundles of axons called rootlets.

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80
Q

Why does the spinal cord appear segmented?

A

Because the 31 pairs of spinal nerves emerge at regular intervals from intervertebral foramina.

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81
Q

Each pair of spinal nerves is said to arise from a _______ _________

A

Spinal segment

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82
Q

What are roots?

A

Bundles of axons which connect each spinal nerve to a segment of the cord by even smaller bundles of axons called rootlets.

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83
Q

What is another name for the posterior root?

A

Dorsal root

84
Q

What types of axons do posterior roots contain?

A

Sensory axons

85
Q

Each posterior root has a _________

A

Swelling called the posterior root ganglion

86
Q

What does a root ganglion contain?

A

Cell bodies of the sensory neurones

87
Q

What does the anterior root contain?

A

Axons of motor neurones, which conduct nerve impulses from the CNS to effectors (muscles and glands)

88
Q

What is the structure of a transverse section of the spinal cord?

A

Regions of white matter surrounding an inner core of grey matter.

89
Q

What does the white matter of the spinal cord consist primarily of?

A

Bundles of myelinated axons of neurones.

90
Q

How is the spinal cord divided into right and left sides?

A

Two grooves penetrate the white matter of the spinal cord.

91
Q

What is each groove of the spinal cord called?

A

Anterior median fissure and posterior median sulcus.

92
Q

What does the grey matter of the spinal cord consist of? What shape is it?

A

Dendrites and cell bodies of neurones, unmyelinated axons, and neuroglia. H shaped

93
Q

What forms the crossbar of the grey matter H?

A

Gray commissure

94
Q

What is in the centre of the grey commissure?

A

A small space called the central canal which extends the entire length of the spinal cord and is filled with cerebrospinal fluid.

95
Q

Where is the white commissure located?

A

Anterior to the grey commissure, which connects the white matter of the right and left sides.

96
Q

With regard to the spinal cord, what are nuclei?

A

Functional groups of clusters of neuronal cell bodies in the grey matter of the spinal cord and brain.

97
Q

What are the two types of nuclei in the spinal cord?

A

Sensory nuclei: receive input from receptors via sensory neurones.
Motor nuclei: provide output to effector tissues via motor neurones. Provide nerve impulses for muscle contraction.

98
Q

What is the grey matter on each side of the spinal cord subdivided into?

A

Regions called horns

99
Q

The posterior grey horns contain _________

A

Cell bodies and axons of interneurons as well as axons of incoming sensory neurones.

100
Q

What do the anterior grey horns contain?

A

Somatic motor nuclei

101
Q

What lies between posterior and anterior grey horns?

A

Lateral grey horns

102
Q

Where are lateral grey horns found ONLY?

A

In thoracic and upper lumbar segments of the spinal cord.

103
Q

What do lateral grey horns contain?

A

Autonomic motor nuclei, which are clusters of cell bodies of autonomic motor nuclei that regulate activity of cardiac muscle, smooth muscle and glands.

104
Q

What is the white matter of the spinal cord divided into?

A

Columns:

1) Anterior white columns
2) Posterior white columns
3) Lateral white columns

105
Q

What does each column contain? What are they called?

A

Distinct bundles of axons having a common origin or destination and carrying similar information. Tracts

106
Q

Distinguish between tracts and nerves.

A

Tracts are bundles of axons in the CNS, whereas nerves are bundles of axons in the PNS.

107
Q

What are the two types of tracts? What do they do?

A

Sensory tracts: conduct nerve impulses toward the brain.

Motor tracts: Carry nerve impulses from the brain.

108
Q

How do nerve impulses reach the posterior root?

A

1) Sensory receptors detect stimulus.
2) Sensory neurones convey this input as nerve impulses, extending from receptor to spinal nerve.
3) Impulse travels to posterior root.

109
Q

What are the three possible pathways after the impulse has reached the posterior root?

A

1) Axons of sensory neurone may extend into white matter and ascend to brain as part of sensory tract.
2) Axons may enter posterior grey horn and synapse with interneurones whose axons extend into white matter of spinal cord and into brain.
3) Axons may enter posterior grey horn and synapse with interneurones that synapse with somatic motor neurones involved with spinal reflex pathways.

110
Q

What does motor output from the spinal cord involve?

A

Somatic motor neurones of the anterior grey horn.

111
Q

Where do motor tracts descending from the brain enter?

A

White matter of spinal cord. There they either synapse with interneurones or motor neurones.

112
Q

Autonomic

A

Involuntary nervous system

113
Q

How do the upper segments of the spinal cord differ from the lower segments?

A

In the cervical and lumbar segments. More sensory and motor tracts present. Less white matter but more grey matter.

114
Q

Define sensation

A

The conscious or subconscious awareness of changes in the external or internal environment.

115
Q

When do we become consciously aware of sensory stimuli?

A

When the sensory impulses reach the cerebral cortex.

116
Q

What is a sensory modality?

A

Each unique types of sensation such as touch, pain, vision, or hearing.

117
Q

A given sensory neurone carries information for how many sensory modalities?

A

Only ONE

118
Q

What are general senses?

A

Both somatic and visceral senses

119
Q

What are somatic senses?

A

Tactile sensations, thermal sensations, and proprioperceptive sensations

120
Q

What are visceral senses?

A

Provide information about conditions within internal organs

121
Q

What are special senses?

A

Include the sensory modalities of smell, taste, hearing, and equilibrium

122
Q

Define stimulus

A

A change in the environment that can activate certain sensory receptors.

123
Q

What is meant by selectivity of sensory receptors?

A

It responds only weakly or not at all to other stimuli.

124
Q

What are the 4 steps leading to a sensation arising?

A

1) Stimulation of the sensory receptor
2) Transduction of the stimulus
3) Generation of nerve impulses
4) Integration of sensory input

125
Q

What are first-order neurones?

A

Sensory neurones that conduct impulses from the PNS into the CNS.

126
Q

What are free nerve endings?

A

Bare dendrites. Receptors for pain and temperature are free nerve endings.

127
Q

What are encapsulated nerve endings/receptors?

A

Receptors for other somatic sensations such as touch and pressure.

128
Q

What is the structure of an encapsulated nerve ending?

A

Dendrites are enclosed in a connective tissue capsule.

129
Q

What is a generator potential?

A

The potential produced by free nerve endings and encapsulated nerve endings when first stimulated.

130
Q

What happens when a generator potential is large enough to reach threshold?

A

It triggers one or more nerve impulses in the axon of a first-order sensory neurone.

131
Q

What is meant by adaptation of sensory receptors?

A

The generator potential decreases in amplitude during a maintained constant stimulus.

132
Q

What are the receptors for touch called?

A

Meissner corpuscles

133
Q

What are the receptors for pressure called?

A

Pacinian corpuscles

134
Q

What are the receptors for pain called?

A

Nociceptors

135
Q

From where to where do upper motor neurones extend?

A

From the brain to lower motor neurones

136
Q

What is the direct motor pathway?

A

Provides input to lower motor neurones via axons that extend directly from the cerebral cortex

137
Q

What is the indirect motor pathway?

A

Provides input to lower motor neurones from motor centres in the basal nuclei, cerebellum, and cerebral cortex.

138
Q

What are the three types of neurones in the somatic sensory pathway?

A

1) First-order neurones
2) Second-order neurones
3) Third-order neurones

139
Q

What do first-order neurones do?

A

Conduct impulses from somatic receptors into the brain stem or spinal cord.

140
Q

What nerves do impulses from the facial region travel along?

A

Cranial nerves

141
Q

What nerves do impulses from areas apart from the face travel along?

A

Spinal nerves

142
Q

What do second-order neurones do?

A

Conduct impulses from the brain stem and spinal cord to the thalamus.

143
Q

Where do axons of second-order neurones decussate (cross over)?

A

In the brain stem or spinal cord before ascending to the ventral posterior nucleus of thalamus.

144
Q

All somatic sensory information from one side of the body reaches the thalamus on the ________ side.

A

Opposite

145
Q

What do third-order neurones do?

A

Conduct impulses from the thalamus to the primary somatosensory area of the cortex on the same side.

146
Q

What does the thalamus act as?

A

A relay station

147
Q

Which pathway do nerve impulses for touch and pressure follow?

A

Posterior column-medial lemniscus pathway

148
Q

Why is the posterior column-medial lemniscus pathway called as such?

A

Comes from the names of two white matter tracts that convey the impulses: the posterior column of the spinal cord and the medial lemniscus of the brain.

149
Q

In the spinal cord, what do the axons of first order neurones in the posterior column - medial lemniscus pathway form?

A

The posterior columns, which consist of two parts: gracile fasciculus and cuneate fasciculus.

150
Q

What do the first order neurones of the posterior column - medial lemniscus pathway synapse with?

A

The dendrites of second-order neurones whose cell bodies are located in the gracile nucleus or cuneate nucleus of the medulla.

151
Q

Choose the correct pathway for sensory neurones along the posterior column - medial lemniscus pathway:

a) nucleus –> fascisculus

b) fasciculus –> nucleus

A

b)

152
Q

Where do the axons of the second-order neurones cross to? What do they enter?

A

The opposite side of the medulla and enter the medial lemniscus.

153
Q

What do second-order neurones synapse with? Where does the impulse go from there?

A

Third-order neurones, which project their axons to the primary somatosensory area of the cerebral cortex.

154
Q

What path do nerve impulses for pain and temperature take?

A

Anterolateral pathway

155
Q

Describe the first step of the anterolateral pathway.

A

First-order neurones connect a receptor with the spinal cord.

156
Q

Describe the second step of the anterolateral pathway.

A

Synapse with second-order neurones, whose cell bodies are located in the posterior grey horn of the spinal cord.

157
Q

Where do the axons of the second-order neurones cross to?

A

The opposite side of the spinal cord.

158
Q

What does the anterolateral pathway pass upward to the brain stem as?

A

The spinothalamic tract

159
Q

What are the relative sizes of regions in the somatosensory area proportional to?

A

The number of specialised sensory receptors within the corresponding part of the body.

160
Q

What is sensory homunculus?

A

The distorted somatic sensory map of the body.

161
Q

What orchestrates all voluntary and involuntary movements in the brain and spinal cord?

A

Neural circuits

162
Q

From the brain stem, LMN’s extend though ______ ______ to innervate skeletal muscles of the face and head.

A

Cranial nerves

163
Q

From the spinal cord, LMN’s extend through ______ ______ to innervate skeletal muscles of the limbs and trunk.

A

Spinal nerves

164
Q

Where do LMN’s have their cell bodies?

A

In the brain stem and spinal cord

165
Q

How many neural circuits are there in the somatic motor pathways? What do they do?

A

4 - Control movement by providing input to LMN’s

166
Q

What are the local circuit neurones?

A

Input arrives at LMN’s from nearby interneurones called local circuit neurones.

167
Q

Where are local circuit neurones located?

A

Close to the LMN cell bodies in the brain stem and spinal cord.

168
Q

Which neurones receive input from the UMN’s?

A

Both local circuit neurones and lower motor neurones.

169
Q

What do most UMN’s synapse with?

A

Local circuit neurones, which in turn synapse with LMN’s

170
Q

What are the UMN’s from the cerebral cortex essential for?

A

Execution of voluntary movements of the body

171
Q

What is the function of basal nuclei neurones?

A

Assist movement by providing input to UMN’s. Help initiate and terminate movements, suppress unwanted movements, and establish a normal level of muscle tone.

172
Q

What is the function of cerebellar neurones?

A

Aid movement by controlling the activity of UMN’s. Coordinates body movements and helps maintain posture and balance.

173
Q

What are direct motor pathways?

A

Provide input to LMN’s via axons that extend directly from the cerebral cortex.

174
Q

What are indirect motor pathways?

A

Provide input to LMN’s from motor centers in the basal nuclei, cerebellum, and cerebral cortex.

175
Q

How does the premotor area contribute to the control of body movements?

A

It contributes axons to the descending motor pathways.

176
Q

More cortical area is devoted to those muscles involved in ________, ________, or ________ movements.

A

Skilled, complex, or delicate

177
Q

Which pathway do nerve impulses for voluntary movements use?

A

The direct motor pathway

178
Q

What is another name for the direct motor pathways?

A

Pyramidal pathways - consist of axons that descend from pyramidal cells.

179
Q

What are pyramidal cells?

A

UMN’s with pyramid shaped cell bodies located in the primary motor area and the premotor area of the cerebral cortex

180
Q

What types of impulses do the corticospinal pathways conduct?

A

Impulses for the control of muscles of the limbs and trunk.

181
Q

What forms the corticospinal tract?

A

Axons of UMN’s in the cerebral cortex

182
Q

What do the corticospinal tracts descend through?

A

Internal capsule of the cerebrum

183
Q

What are the pyramids in the medulla oblongata formed from?

A

The axon bundles of the corticospinal tracts.

184
Q

What percentage of the corticospinal axons decussate to the opposite side in the medulla oblongata?

A

90%

185
Q

Where do the remaining 10% of corticospinal axons decussate?

A

At the spinal cord levels where they synapse with a local circuit neurone or LMN.

186
Q

What are the two types of corticospinal tracts?

A

Lateral corticospinal tract and the anterior corticospinal tract

187
Q

What forms the lateral corticospinal tract?

A

Corticospinal axons that decussate in the medulla form the lateral corticospinal tract in the lateral white column of the spinal cord.

188
Q

Where do the axons in the lateral corticospinal tract synapse with local circuits or LMN’s?

A

In the anterior grey horn of the spinal cord.

189
Q

Where do axons of the lateral corticospinal tract terminate? What are these muscles responsible for?

A

Skeletal muscles that control movements of the distal parts of the limbs. The distal muscles are responsible for precise, agile, and highly skilled movements of the hands and feet.

190
Q

What forms the anterior corticospinal tract?

A

Corticospinal axons that do not decussate in the medulla form the anterior corticospinal tract in the anterior white column of the spinal cord.

191
Q

Where do the axons of the anterior corticospinal tract decussate?

A

At each spinal cord, some of the axons decussate via the anterior white commissure.

192
Q

What do the axons of the anterior corticospinal tract synapse with?

A

Local circuit neurones or LMN’s in the anterior grey horn.

193
Q

Where do the axons of the anterior corticospinal tract terminate?

A

Skeletal muscles that control movements of the trunk and proximal parts of the limbs.

194
Q

What is Parkinson’s disease? At what age does it usually occur?

A

A progressive disorder of the CNS that typically affects its victims around age 60.

195
Q

What degenerates in PD?

A

Neurones that extend from the substantia nigra to the putamen and caudate nucleus, where they release the neurotransmitter dopamine (DA)

196
Q

What do the neurones of the caudate nucleus liberate?

A

ACh

197
Q

What imbalance causes the symptoms of PD?

A

Imbalance between the levels of ACh and DA.

198
Q

Define tremor

A

When the muscles of the upper limb alternately contract and relax, causing the hand to shake.

199
Q

What are the symptoms of PD?

A

Tremor (most common)
Increased muscle tone - rigidity
Bradykinesia
Hypokinesia

200
Q

What is meant by Bradykinesia?

A

Slowness of movements

201
Q

What is meant by hypokinesia?

A

Decreasing range of movement

202
Q

What is treatment of PD directed towards?

A

Increasing levels of DA and decreasing levels of ACh.

203
Q

Why is taking dopamine orally useless?

A

DA cannot cross the blood-brain barrier

204
Q

What occurs during a pallidotomy?

A

A part of the globus pallidus that generates tremors and produces muscle rigidity is destroyed.

205
Q

What does deep-brain stimulation involve?

A

The implantation of electrodes into the subthalamic nucleus.

Biomedicine: MEDSCI142 COPY COPY (19 decks)

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