Lecture 8 & 9: CNS Flashcards
1
Q
Nervous system function
A
Receiving and processing impulses from external and internal environments
Initiating appropriate responses
2
Q
Structural classification of nervous system
A
Central nervous system
Peripheral nervous system
3
Q
Functional classification of nervous system
A
Somatic
Visceral (autonomic)
Enteric
4
Q
Central nervous system structures
A
Brain and spinal cord
Brain: cerebral hemispheres, diencephalon, cerebellum, brainstem
Protected by cranial cavity and vertebral canal
5
Q
Brainstem
A
Midbrain
Pons
Medulla oblongata
6
Q
Peripheral nervous system structures
A
Cranial nerves
Spinal nerves
Associated ganglia
7
Q
CNS Functions
A
Process incoming sensory and outgoing motor messages
Higher mental activity: learning, memory, reasoning
8
Q
CNS Gray matter
A
Nerve cell bodies
Bundles of unmyelinated nerve fibres
Non-neuronal supportive cells - neuroglia
9
Q
CNS White matter
A
Bundles of myelinated nerve fibers - tracts
10
Q
Spinal cord nervous tissue
A
Gray matter forms H shaped core, surrounded by white matter
11
Q
Brain nervous tissue
A
Thin gray matter cortex surrounds white matter core
12
Q
Nucleus
A
Cluster of nerve cell bodies in the CNS
13
Q
Ganglion
A
Cluster of nerve cell bodies outside the CNS
14
Q
Embryonic development of the brain
A
3 weeks: solid tube
5 weeks: expands and folds
13 weeks: cerebrum grows faster and surrounds diencephalon; folds in 1 direction
15
Q
Forebrain
A
AKA Prosencephalon
Telencephalon (cerebrum)
Diencephalon (structures surrounding 3rd ventricle)
16
Q
Midbrain
A
Mesencephalon
17
Q
Hindbrain
A
AKA rhombencephalon
Metencephalon (pons and cerebellum)
Myelencephalon (medulla oblongata)
18
Q
Spinal cord
A
43-45cm in upper 2/3 of vertebral canal
Cylindrical structure
Starts at medulla oblongata at foramen magnum and ends at LI/LII intervertebral disc
Unrelated to height
19
Q
Enlargement of spinal cord
A
Cervical enlargement: more neurons to control upper limb muscles
Lumbar enlargement: more neurons to control lower limb muscles
20
Q
Conus medullaris
A
Distal end of spinal cord tapers
Cone shaped
Around LI/LII intervertebral disc
21
Q
Spinal cord grooves
A
Ventral (anterior) medial fissure [ventral/motor rootlets emerge on either side]
Dorsal (posterior) medium sulcus [dorsal/sensory rootlets emerge on either side]
22
Q
Spinal nerves
A
Union of ventral and dorsal roots
23
Q
Dorsal root ganglion
A
Each dorsal root has dorsal root ganglion
Cell bodies of sensory neurons
24
Q
Spinal cord segment
A
Each spinal cord has spinal nerve 31 segments 8 cervical 12 thoraic 5 lumbar 5 sacral 1 coccygeal
25
Spinal cord gray matter
H shaped
Anterior/ventral horn (motor)
Posterior/dorsal horn (sensory)
Lateral horn (autonomic) - only present at T1-L2 (sympathetic) and S2-S4 (parasympathetic)
Halves are connected by gray commissure with central canal
26
Spinal cord white matter
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Surrounds gray matter
Ventral column
Lateral column
Dorsal column
Has ascending (sensory) tracts and descending (motor) tracts
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27
Sensory Tracts of spinal cord
Relay sensory information from receptors
3 neurons (1st/2nd/3rd order)
1st order: in dorsal root ganglion
2nd order: either dorsal horn of spinal cord, or medulla oblongata
3rd order: thalamus
Then goes to sensory area of parietal lobe
*Some only have 2 neurons; it does not go to thalamus/cerebellum so does not reach conscious level
28
Dorsal column/medial lemniscus pathway
Fine touch and conscious proprioception
1st ON: dorsal root ganglion and brought up spinal cord in dorsal column
2nd ON: medulla to either nucleus gracilis or nucleus cuneatus, then decussates
3rd ON: thalamus and projects to primary somatosensory cortex
29
Spinocerebellar pathways
Unconscious proprioception of trunk and lower limbs
1st ON: dorsal root ganglion
2nd ON: in posterior horn at the same level and ascends on the ipsilateral side in lateral column to project to cortex of cerebellum
30
Lateral spinothalamic pathway
Temperature and pain
1st ON: dorsal root ganglion
2nd ON: posterior horn and immediately decussates and ascends in contralateral side of the spinal cord
3rd ON: thalamus and projects to the primary somatosensory cortex
31
Anterior spinothalamic pathway
Non discriminative (crude) touch
32
Motor tracts of spinal cord
Motor instruction from frontal lobe or nuclei in brainstem
2 neurons: upper motor neuron (in cerebrum [voluntary contraction] or brainstem [muscle tone]) and lower motor neuron (in brainstem to cranial nerves or anterior horn of spinal cord)
33
Pyramidal tracts
Skeletal muscles of limbs and trunks
| Ex. Lateral and ventral corticospinal tract
34
Extrapyramidal tracts
Regulating subconscious/postural body movements
| Ex. Rubrospinal, tectospinal, vestibulospinal, reticulospinal
35
Corticospinal tract
UMN in motor cortex of cerebrum
Lateral corticospinal tract: axons decussate at pyramid in medulla and continue down lateral column to LMN in ventral horn; 80% of pathways; targets limbs
Anterior corticospinal tract: axons descend in anterior column and decussate at level of spinal cord before synapsing with LMN in ventral horn; 20% pathways; targets core muscles
36
Rubrospinal tract
UMN in red nucleus of midbrain
| Axons decussate at midbrain and descend through medulla and lateral column before synapsing with LMN in ventral horn
37
Brainstem
Medulla oblongata
Pons
Midbrain
38
Functions of brainstem
Passage for ascending and descending tracts between cerebrum and spinal cord
Contains nuclei for CNIII-XII
Regulates autonomic behaviours
39
Medulla
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Pyramidal
Separated from pons by ponto-medullary sulcus
Pyramid
Olive
Inferior olivary nucleus
Medial lemniscus pathway
Reticular formation
CN IX, X, XI, XII emerge
Nucleus of CN V, VIII, IX, X, XI, XII
4th cerebral ventricle
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40
Reticular formation
Intranet of CNS
Cluster of nuclei
Keeps you awake/level of alertness
41
Pons
Anterior is convex with basilar sulcus filled with basilar artery
CN V, VI, VII, VIII emerge; also contains their nuclei
White matter has ascending and descending tracts (Ex. medial lemniscus pathway)
Pontine nuclei
Reticular formation
4th ventricle
42
Midbrain
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Cerebral peduncles
Superior colliculus + nucleus
Inferior colliculus + nucleus
Cerebral aqueduct
Nucleus of CN III, IV, V
Ascending and descending pathways
Reticular formation
Red nucleus
Substantia Nigra
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43
Pyramid
On either side of the median anterior fissure of medulla
44
Olive
Lateral to pyramid in medulla
45
Inferior olivary nucleus
Cooperates with cerebellum to learn new motor skills
46
Pontine nuclei
Relay center for motor pathways between cerebrum and cerebellum and coordinates voluntary movement
47
Cerebral peduncles
2 columns anteriorly containing descending pathways
| Ex. Corticospinal and corticobulbar = crus cerebra
48
Superior colliculus
Pair in posterior midbrain
| Visual reflexes
49
Inferior colliculus
Pair in posterior midbrain
| Auditory reflexes
50
Red nucleus
Rubrospinal tract
Coordinates with cerebellum for fine movements
Lesions lead to intention tremor
51
Substantia Nigra
Regulates movements/coordination of gross movements
Linked to basal ganglia
Lesions lead to Parkinson's disease = resting tremor
52
Cerebellum
2 cerebellar hemispheres connected by vermis
Folia: folds in cerebellum, separated by grooves/sulci
Largest sulcus is primary fissure dividing it into the anterior and posterior lobe
Gray matter forms cerebellar cortex and surrounds white matter = arbor vitae; containing 4 pairs of cerebellar nuclei
53
Cerebellum Function
Coordination of voluntary movements and maintenance of posture and balance
54
Cerebellar Peduncles
Cerebellum is behind medulla and pons
Superior cerebellar peduncle: to red nucleus of midbrain and thalamus
Middle cerebellar peduncle: to pontine nuclei of pons
Inferior cerebellar peduncle: to medulla
55
Diencephalon
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Between cerebral hemispheres and midbrain
Surrounds 3rd ventricle
Thalamus
Hypothalamus
Epithalamus
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56
Thalamus
Cluster of nuclei as a relay centre for senses (except smell) before the cortex
Egg shaped
57
Hypothalamus
Inferior and medial to thalamus
Center of autonomic nervous system: regulates appetite, blood pressure, body temperature etc.
Regulates endocrine system through pituitary gland
58
Epithalamus
Posterior and superior to thalamus
| Contains pineal gland: regulates circadian rhythm and melanin in skin
59
Cerebrum
Outer cerebral cortex and inner white matter with nuclei
Anterior and middle cranial fossa
L and R cerebral hemispheres separated by longitudinal fissure
Folds: gyrus
Grooves: sulcus
60
Lobes of cerebrum
Frontal: initiate motor impulses, higher order thinking/reasoning, judging
Parietal: general sensory cortex (touch, temperature, pain)
Temporal: auditory, taste
Occipital: visual
61
Sulci separating the lobes of the brain
Central sulcus: separates frontal and parietal lobe
Lateral sulcus: separates parietal and temporal and frontal
Pareto-occipital sulcus: separates parietal and occipital
62
Basal ganglia/nuclei
Cluster of nuclei in the white matter
Caudate nucleus (tail)
Leniform (head) - contains putamen and globes pallidus
Coordination of motor function
63
Classification of white matter in CNS
Commissural fibers: connecting similar regions of the L and R hemisphere (crosses midline) Ex. corpus callous
Projection fibers: ascending and descending fibers connecting cortex to lower centers of CNS Ex. internal capsule
Association fibers: connecting different areas of the same hemisphere
64
Cerebral ventricles
Cerebral ventricles have choroid plexus which secretes cerebrospinal fluid
2 lateral ventricles in cerebral hemisphere; has anterior, posterior and inferior horn; connects to 3rd ventricle via interventricular foramen of Monro
3rd ventricle: in between diencephalon; connects to 4th ventricle via cerebral aqueduct
4th ventricle: in brainstem and connects to central canal of spinal cord and subarachnoid space
65
Function of cerebrospinal fluid
Fluid extracted from blood plasma to surround CNS
Cushion against trauma
Protects brain from acceleration/deceleration
Carries waste away from the brain
66
Meninges
3 membranes of connective tissue
Dura mater
Arachnoid mater
Pia mater
67
Dura mater
Attaches to inner surface of neurocranium
Ends at level of vertebra SII
In the skull, composed of outer periosteal layer (attached to inner cranial cavities) and inner meningeal layer separates from periosteal layer)
68
Dural reflections
Partitions to divide cranial cavity
Falx cerebra: Dura mater occupying longitudinal fissure partially separating cerebral hemispheres
Tentorium cerebella: horizontal sheet between cerebellum and occipital lobe, notched anteriorly for the mibrain
Falx cerebelli: vertical reflection of dura mater in sagittal plane along the vermis separating the cerebellar hemispheres
69
Dura sinus
Drain venous blood of the brain to the circulatory system
70
Arachnoid mater
Loose connective tissue attached to inner dura mater
| Involved in the circulation of CSF (does not produce it)
71
Epidural space
Dura mater separated from vertebral canal
Filled with fat
Only in spinal cord, does not exist in skull
72
Subarachnoid space
Separates arachnoid and pia mater
Filled with CSF
Surrounds spinal cord and continues inferiorly until level of SII vertebrae
In skull and spinal cord
73
Lumbar cistern
Space between end of spinal cord at LI/LII and vertebrae SII
Contains roots of spinal nerves and CSF
74
Arachnoid granulations (villi)
Finger like projects of arachnoid mater in the superior part of the brain to drain CSF information dural sinuses
75
Pia mater
Delicate thin layer of connective tissue attached to the brain and spinal cord
Carries blood vessels for nutrients/oxygen to the CNS
76
Denticulate ligaments
Lateral triangular extensions of Pia mater that anchor spinal cord to arachnoid and dura mater
77
Filum terminale
Extension of pia mater from conus medullaris extending inferiorly and fuses with arachnoid and dura mater to anchor spinal cord to coccyx
