CNS Spine, Brainstem, Cerebellum, Diencephalon Flashcards
1
Q
spinal cord functions
A
- spinal nerves attach to spinal cord and are involved with sensory and motor innervation of body below the head
- provides two-way conduction pathway for signals between the body and the brain
- major center for reflexes
2
Q
spinal cord location
A
runs through the vertebral canal of the vertebral column extending along successive vertebral foramina
extends from the foramen magnum at the base of the skull to the level of L3 in infants and L1 or L2 in children and adults
3
Q
parts of the spinal cord
A
conus medullaris: inferior end of the spinal cord tapers into the conus medullaris
filum terminale: long filament of connective tissue extending from the conus medullaris down to the coccyx inferiorly, anchoring the spinal cord in place
cauda equina: collection of spinal nerve roots in inferior/caudal end of vertebral canal
cervical and lumbar enlargements: where nerves for upper and lower limbs arise
4
Q
conus medullaris
A
inferior end of the spinal cord tapers into the conus medullaris
5
Q
filum terminale
A
long filament of connective tissue extending from the conus medullaris down to the coccyx inferiorly, anchoring the spinal cord in place
6
Q
cauda equina
A
collection of spinal nerve roots in inferior/caudal end of vertebral canal
7
Q
cervical and lumbar enlargements
A
where nerves for upper and lower limbs arise
8
Q
spinal nerves
A
31 pairs of spinal nerves (PNS) attach to the spinal cord through dorsal and ventral nerve roots
8 cervical, 12 thoracic, 5 lumbar, 1 sacral, 1 coccygeal
pass through transverse foramina of cervical vertebrae, intervertebral foramina of thoracic and lumbar vertebrae, pass through lumbar foramen in sacrum
9
Q
spinal cord segments
A
vertebral location where spinal nerve fibers emerge from the spinal cord
10
Q
spinal cord deep grooves
A
spinal cord is wider laterally than anterioposteriorly
two deep grooves run the length of the cord and partly divide it into the right and left halves
1) dorsal (posterior) median sulcus
2) wider ventral (anterior) median fissure
11
Q
white matter of the spinal cord
A
outer region of the spinal cord
composed of mainly myelinated axons (fibers) as well as unmyelinated axons, which allows communication within the spinal cord between spinal cord and brain
12
Q
white matter funiculi
A
the white matter on each side of the spinal cord is divided into funiculi (“long ropes”)
dorsal (posterior) funiculus
ventral (anterior) funiculus
lateral funiculus
13
Q
fiber classification in white matter of spinal cord
A
ascending fibers: most carry sensory information from sensory neurons up to the brain
descending fibers: most carry motor information from the brain to spinal cord to stimulate muscle contraction or gland secretion
commissural fibers: fibers that carry information from one side of the spinal cord to another
commissure: bundle of axons that crosses from one side of the CNS to another
14
Q
types of fibers in white matter of the spinal cord
A
ascending fibers
descending fibers
commissural fibrers
commissure
15
Q
ascending fibers
A
most carry sensory information from sensory neurons up to the brain
16
Q
descending fibers
A
most carry motor information from the brain to spinal cord to stimulate muscle contraction or gland secretion
17
Q
commissural fibers
A
fibers that carry information from one side of the spinal cord to another
18
Q
commissure
A
bundle of axons that crosses from one side of the CNS to another
19
Q
gray matter of the spinal cord
A
gray matter transverse section shaped like the letter “H” or a butterfly
gray commissure (cross bar of the H) - composed of unmyelinated axons and contains the narrow central cavity (central canal)
dorsal horns (posterior of H)
ventral horns (anterior of H)
lateral horns: small lateral columns in the thoracic and superior lumbar segments of the spinal cord
20
Q
dorsal root ganglia (gray matter in spinal cords)
A
sensory neuron cell bodies lie outside the spinal cord
21
Q
dorsal roots (gray matter in spinal cords)
A
sensory neuron axons reach the spinal cord via dorsal roots
22
Q
dorsal horn interneurons (gray matter in spinal cords)
A
receive information from sensory neurons
23
Q
ventral and lateral horns of gray matter in spinal cords
A
contain cell bodies of motor neurons and interneurons
motor neurons send their axons out of the spinal cord via the ventral roots to supply muscles and glands
ventral horns are the largest in the cervical and lumbar segments of the cord, which innervate upper and lower limbs
24
Q
why are ventral horns largest in the cervical and lumbar segments of the cord?
A
they innervate the upper and lower limbs
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paresthesia
damage to the dorsal horn or sensory neuron cell bodies in dorsal root ganglia can lead to paresthesia
loss of sensory function
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paralysis
damage to the ventral horn or ventral motor roots destroys the motor neurons and causes paralysis of skeletal muscles served
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protection of the spinal cord
vertebrae
meninges
cerebrospinal fluid
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meninges
three connective tissue membranes that lie just external to the brain and spinal cord
cover and protect CNS
enclose and protect blood vessels that supply CNS
contain cerebrospinal fluid
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meninges: external to internal
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epidural space
dura mater
subdural space
arachnoid mater
subarachnoid space
pia mater
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epidural space
fat-rich cushioning space just external to the dura mater
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subdural space
thin fluid-filled space in between dura mater and arachnoid mater
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subarachnoid space
filled with cerebral spinal fluid and large blood vessels that supply the neural space
space is spanned by web-like threads that anchor the arachnoid mater to the pia mater
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pia mater
innermost layer of meninges
clings tightly to the surface of the spinal cord
delicate layer of connective tissue is richly vascularized with small blood vessels
extends to the coccyx covering the filum terminale
denticulate ligaments: lateral extensions of pia mater anchor the spinal cord laterally to the arachnoid and dura mater throughout the length of the cord
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denticulate ligaments
lateral extensions of pia mater
| anchor the spinal cord laterally to the arachnoid and dura mater throughout the length of the cord
35
cerebrospinal fluid
watery fluid that fills the subarachnoid space and hollow cavities of the brain and spinal cord
provides a liquid cushion and buoyancy for the spinal cord and brain
nourishes brain and spinal cord
removes wastes produced by neurons
carries chemical signals between parts of the CNS
36
functions of cerebrospinal fluid
- provides liquid cushion and buoyancy for spinal cord and brain
- nourishes brain and spinal cord
- removes waste produced by neurons
- carries chemical signals between parts of the CNS
37
lumbar puncture/spinal tap
because the adult spinal cord ends the level of vertebrae L1-L2, a lumbar puncture (spinal tap) needs to be done below this site
a needle is inserted between L4 and L5 into the subarachnoid space to obtain CSF or inject medicine
38
protection of the brain
skull
meninges
cerebrospinal fluid
blood-brain barrier
39
function of meninges
cover and protect the CNS
enclose and project the vessels that supply the CNS
contain the cerebrospinal fluid between pia and arachnoid maters
40
two layered dura mater
strongest part of meninges
two layered sheet of fibrous connective tissue layer
periosteal layer (=periosteum) is the outer layer that attaches to the internal surface of the skull bones
meningeal layer is deepest layer that forms external covering of the brain and is continuous with dura mater that surrounds the spinal cord
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periosteal layer
outer layer of dura mater
| attaches to the internal surface of the skull bones
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meningeal layer
deepest layer of dura mater
| forms external covering of the brain and is continuous with dura mater that surrounds the spinal cord
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dura sinuses
two layers of dura mater are fused except where they separate to enclose the blood-filled dural sinuses
collect blood and CSF from the brain and conduct it to the internal jugular veins of the neck
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superior sagittal sinus
largest dural sinus
| positioned in the superior midline
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dura mater
extends inward to form flat partitions to subdivide the cranial cavity and stabilize the brain
falx cerebri, falx cerebelli, tentorium cerebelli
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falx cerebri
large sickle shaped vertical sheet in the median plane in the longitudinal fissure between the cerebral hemispheres
attaches anteriorly to crista galli of ethmoid bone
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falx cerebelli
vertical partition extends inferiorly from posterior part of falx cerebri and runs along vermis of cerebellum in the posterior cranial fossa
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tentorium cerebelli
this almost horizontal sheet lies in the transverse fissure between the cerebrum and cerebellum
encloses transverse sinus
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arachnoid villi
arachnoid granulations
- knoblike projections formed by arachnoid mater
- project through the dura mater over the superior part of the brain into superior sagittal sinus and dural sinuses
- villi act as valves that allow CSF to pass from subarachnoid space into dural blood sinuses
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function of arachnoid villi
act as valves that allow CSF to pass from subarachnoid space into dural blood sinuses
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meningitis
inflammation of meningeal tissues from infection
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encephalitis
inflammation of brain or spinal cord from infection
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the brain
average adult brain weighs 1500 grams
performs the most complex neural functions: intelligence, conscientiousness, memory, sensory-motor integration, cranial nerves involved in innervation of the head
brain also controls and maintains: autonomic nervous system, endocrine system
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functions performed by the brain
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intelligence
conscientiousness
memory
sensory-motor integration
cranial nerves are involved in innervation of the head
autonomic nervous system
endocrine system
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embryonic development of the brain: week 4
brain arises from the rostral part of the neural tube int he 4th week of development
caudal portion of the neural tube becomes the spinal cord
three primary brain vesicles emerge in 4-week-old embryo: prosencephalon (forebrain), mesencephalon (midbrain), rhombencephalon (hindbrain)
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embryonic brain development: week 5
secondary brain vesicles:
prosencephalon splits into telencephalon and diencephalon
mesencephalon stays the same
rhombencephalon splits into metencephalon and myelencephalon
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secondary brain vesicles develop into brain structures
telencephalon--> the cerebral hemispheres
diencephalon--> thalamus, hypothalamus, and epithalamus
mesencephalon--> midbrain
metencephalon--> pons and cerebellum
myelencephalon--> medulla oblongata
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telencephalon develops into
cerebral hemispheres
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diencephalon develops into
hypothalamus, thalamus, epithalamus
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mesencephalon develops into
midbrain
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metencephalon develops into
pons and cerebellum
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myelencephalon develops into
medulla oblongata
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cortex
additional layer of gray matter that is external to white matter
64
ventricles of the brain
expansions of the brain's central cavity
filled with cerebrospinal fluid
lined with ependymal cells (neuroglial cell of the CNS)
continuous with each other and with the central canal of the spinal cord
paired lateral ventricles, third ventricle, fourth ventricle
65
vesicles and ventricles of the brain
telencephalon: lateral ventricles
diencephalon: 3rd ventricle
mesencephalon: cerebral aqueduct
metencephalon/myencephalon: 4th ventricle
66
paired lateral ventricles
located in cerebral hemispheres
horseshoe-shaped from bending of the cerebral hemispheres
each ventricle has anterior horn, posterior horn, inferior horn
anterior horn of each lateral ventricle is separated by a septum pellucidum
67
septum pellucidum
separates the anterior horn of each lateral ventricle
68
3rd ventricle and cerebral aqueduct
third ventricle lies in diencephalon
anteriorly, the third ventricle is connected with lateral ventricles by interventricular foramina
cerebral aqueduct in the midbrain connects 3rd and 4th ventricles
69
4th ventricle
lies in hindbrain brainstem dorsal to pons and superior (rostral) half of the medulla oblongata
three openings in the walls of the 4th ventricle: paired lateral apertures in the side walls and median aperture in the roof
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openings in the 4th ventricle
paired lateral apertures in the side walls
median aperture in the roof
aperture holes connect the ventricles with the subarachnoid space so that CSF can fill both the ventricles and subarachnoid space
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choroid plexuses
capillary rich membranes located in the roofs of the 4th ventricle, 3rd ventricle, and lateral ventricles
where CSF is formed
consists of: knot of porous capillaries surrounded by a single layer of ependymal cells joined by tight junctions and bearing long cilia
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choroid plexuses consist of:
knot of porous capillaries surrounded by a single layer of ependymal cells joined by tight junctions and bearing long cilia
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components in CSF formed by choroid plexuses
glucose
oxygen
vitamins
ions eg. Na, Cl, Mg
74
CSF movement
1. CSF is produced from blood plasma by the choroid plexus of each ventricle
2. CSF enters ventricles
3. most CSF enters subarachnoid space through the lateral and median apertures in walls of 4th ventricle, some CSF enters the central canal of spinal cord
4. CSF flows through subarachnoid space and bathes outer surfaces of brain and spinal cord
5. CSF passes through the arachnoid villi and is absorbed into the blood through the venous dural sinuses
75
hydrocephalus
excessive accumulation of CSF in ventricles and/or the subarachnoid space
76
blood-brain barrier
rich supply of capillaries provides nutrients to the brain
some blood borne molecules can cross other capillaries, but cannot cross the brain capillaries
tight junctions join the endothelial cells in the brain capillaries making them the least permeable capillaries in the body
77
functions of blood-brain barrier
prevents some blood-borne toxins (eg urea, bacterial toxins) and some drugs from entering the brain
vital nutrients such as oxygen and glucose pass through easily
some fat soluble molecules eg alcohol, nicotine, and anesthetics pass through
78
brain stem functions
passageway for all fiber tracts running between the cerebrum and spinal cord
heavily involved with the innervation of the face and head
9 of the 12 pairs of cranial nerves originate in the brainstem
generates automatic behaviors necessary for survival
79
the brain stem: medulla oblongata
conical shaped
continuous with the spinal cord at level of foramen magnum of the skull
most caudal level of the brainstem
part of 4th ventricle lies dorsal to rostral half of medulla
80
medulla oblongata: pyramids
two longitudinal ridges which lie on ventral surface
formed by pyramidal tracts, which carry voluntary motor output from the cerebrum to the spinal cord
decussation of pyramids
81
decussation of pyramids
in the caudal part of the medulla, most of the pyramidal motor fibers cross over the opposite side of the brain to enable each cerebral hemisphere to control the voluntary movements of the opposite sides of the body
82
inferior olivary nucleus
large wavy fold of gray matter
relay station for sensory information traveling to cerebellum via the inferior cerebellar peduncle, especially for proprioceptive information ascending from the spinal cord
83
reticular formation
loose cluster of brain nuclei that run through the core of the brainstem
stimulate cerebral alertness and regulates muscles
reticular formation form three columns that extend the length of the brainstem
1) midline raphe nuclei
2) median nuclear group
3) lateral nuclear group
84
visceral motor nuclei
part of reticular formation in medulla
cardiac center regulates force and rate of heart beat
vasomotor center regulates blood pressure
respiratory center regulates breathing
centers for hiccuping, sneezing, swallowing, and coughing
85
the pons
- a bulge in the brainstem between the midbrain and the medulla oblongata
- forms a ventral bridge between the brainstem and the cerebellum
- dorsally it is separated from the cerebellum by the 4th ventricle
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medial lemniscus
has ascending sensory tracks and is ventral to the reticular formation
87
pontine nuclei
relay brain nuclei in a path that connects a portion of the cerebral cortex with the cerebellum which contributes to coordination of voluntary movements
88
pons: gray and white matter
gray matter: cranial nerve nuclei V, VI, VII
pontine nuclei
reticular formation nuclei
white matter: pyramidal descending motor tracts
medial lemniscus ascending sensory tracts
middle cerebellar peduncles with tract from cerebrum to cerebellum
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the brain stem: the midbrain
most rostral region of brainstem, lies between pons and diencephalon
central cavity of the midbrain: cerebral aqueduct
reticular formation
medial lemniscus with ascending sensory tract
pyramidal descending motor tract (crus cerebri)
tectum is dorsal midbrain
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the brain stem: the midbrain (dorsal and ventral)
ventral surface: cerebral peduncles contain pyramidal (corticospinal) tracts descending from the cerebrum to the spinal cord
ventral part of each peduncle is called the crus cerebri
dorsally, a pair of superior cerebellar peduncles carry instructions away from cerebellum to midbrain and up the to the cerebral cortex
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crus cerebri
ventral part of the cerebral peduncles
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periaqueductal gray matter
surrounds the cerebral aqueduct
involved in sympathetic (fright-flight) reaction
midbrain link between part of brain that perceives fear and autonomic pathway that triggers the sympathetic reaction
mediates response to visceral pain
93
what part of the midbrain mediates response to visceral pain?
periaqueductal gray matter
94
corpora quadrigemina
dorsal midbrain
largest of brain nuclei that make up tectum ("roof") of dorsal midbrain and from four bumps of the dorsal surface of the midbrain
inferior and superior colliculi
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superior colliculi
nuclei that act in visual reflexes
96
inferior colliculi
nuclei that act in reflexive responses to sound
97
brain nuclei in midbrain: substantia nigra
gray matter that is embedded into midbrain white matter
contain neuronal cell bodies with melanin in band-like distributions
positioned deep to pyramidal tracts of cerebral peduncle
functionally linked to the basal nuclei and deep gray matter of cerebrum
degeneration of neurons in the substantia nigra contribute to Parkinson's Disease
98
brain nuclei in the midbrain: red nucleus
gray matter that is embedded in white brain matter
lies deep to the substantia nigra
reddish hue due to rich blood supply and presence of iron pigment in neuron cell bodies
associated with cerebellum
99
the cerebellum
smoothes and coordinates body movements directed by other brain regions
helps maintain posture and equilibrium
consists of two hemispheres connected by vermis
surface folded into ridges called folia
100
cerebellar cortex is ____ matter
gray
101
each cerebellar hemisphere is subdivided into:
anterior lobe
posterior lobe
flocculonodular lobe (vestibulocerebellum)
102
flocculonodular lobe
vestibulocerebellum
on anteroinferior surface of cerebellum
two flocculi are connected to the midline structure called the nodulus by thin pedicles
important connections to the vestibular nuclei in the medulla
103
three regions of cerebellar hemispheres
1. cortex - outer gray matter
2. arbor vitae - internal white matter
3. deep cerebellar nuclei - deeply situated gray matter
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cortex
outer gray matter which is a neuron rich calculator that smooths out body movements
105
arbor vitae
internal white matter rich in axons which carry information to and from the cortex
106
deep cerebellar nuclei
deeply situated gray matter gives rise to axons that relay the instructions from the cerebellar cortex to other parts of the brain
107
to coordinate body movements, the cerebellar cortex receives three types of information
1. information on equilibrium - relayed from receptors in the inner ear through the vestibular nuclei (CN VIII)
2. information on current movements of the limb and trunk - travels from proprioceptors up the spinal cord through the olivary nuclei to anterior/posterior lobes
3. information from the cerebral cortex - moves through pontine nuclei in the pons to the lateral portions of anterior and posterior lobes
108
cerebellar peduncles
three thick tracts of nerve fibers connect the cerebellum to the brainstem
109
coordinating movement by the cerebellum
1. the cerebellum receives information on movement from the motor cortex of the cerebrum, the inner ear vestibular apparatus, as well as from the trunk and extremities
2. the cerebellum gauges intended movement with body position
3. the cerebellum sends instructions back to the cerebral cortex to continuously coordinate, adjust and fine tune motor commands it sends to the spinal cord
110
higher cognitive functions of the cerebellum
refines movements when learning a new motor skill and establishing a motor memory
participates in cognition of language, problem-solving, task planning
111
damage to floccundonodular lobe
leads to disorders in equilibrium related to vestibular nuclei and inner nuclei of the brain
112
damage to anterior/poster lobes of cerebellum
leads to disorders in coordination
113
coordination
ability to move different parts of the body smoothly and efficiently
114
ataxia
an inability to coordinate voluntary muscle movements that is symptomatic of some central nervous system disorders and injuries and not due to muscle weakness
115
alcohol effects on cerebellum
- high enough levels of alcohol in the blood results in a reduction of coordinated movement and balance along with an ataxic gait
- proposed that one of the main mechanisms through which alcohol affects the cerebellum is through triggering the release of neurotransmitter GABA from Golgi which creates an increase GABAergic inhibition of cerebellar granule cells
- chronic alcohol consumption can cause cerebellar degeneration
116
the diencephalon
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forms the center of the forebrain
surrounded by the cerebral hemispheres
composed of: hypothalamus, thalamus, epithalamus
border the third ventricle
primarily composed of gray matter
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117
thalamus of the diencephalon
paired structure that makes up 80% of the diencephalon
encloses much of 3rd ventricle
forms superolateral walls of the 3rd ventricle
contains approximately a dozen major brain nuclei, each of which sends axons to regions of the cerebral brain cortex (act as relay stations)
thalamus is the "gateway" to the cerebral cortex
118
nuclei of the thalamus
act as relay stations for sensory information
ventral posterolateral nuclei - relay station for sensory information ascending to the primary sensory areas of the cerebral artex
medial geniculate body - receives auditory input
lateral geniculate body - receives visual input
119
ventral posterolateral nuclei
nuclei of the thalamus
| relay station for sensory information ascending to the primary sensory areas of the cerebral cortex
120
medial geniculate body
receives auditory input
121
lateral geniculate body
receives visual input
122
hypothalamus of the diencephalon
forms inferolateral walls of 3rd ventricle (inferior to thalamus)
lies between the optic chasm and the posterior border of mammillary bodies
pituitary gland projects inferiorly
contains approximately a dozen brain nuclei
main visceral control center of the body
123
hypothalamus contribution to regulation of sleep-wake cycles
suprachiasmatic nucleus - body's biological clock, regulates timing of circadian rhythms in response to daylight-dark cycles sensed via the optic nerve
preoptic nucleus - responds to signals from the suprachiasmatic nucleus to induce sleep
other nuclei near mammillary body - mediate arousal from sleep
124
suprachiasmatic nucleus
body's biological clock
| regulates timing of circadian rhythms in response to daylight-dark cycles sensed via the optic nerve
125
preoptic nucleus
responds to signals from the suprachiasmatic nucleus to induce sleep
126
mammillary bodies
located on undersurface of the brain (part of the diencephalon)
part of the limbic system
act as a relay of impulses coming from the amygdala and the hippocampus
127
functions of the hypothalamus
- control of the endocrine system
- control of the autonomic nervous system
- regulation of body temperature
- regulation of hunger and thirst sensations
- control of emotions: pleasure, sex drive, rage
- control of motivational behavior
- formation of memory
- regulation of sleep-wake cycles
128
hypothalamus: feeding-initiation and feeding-inhibition
feeding-initiation centers: lateral part of the hypothalamus
| feeding-inhibition centers: ventromedial part of the hypothalamus
129
epithalamus of the diencephalon
most dorsal part of diencephalon
forms part of the "roof" of 3rd ventricle
contains one tiny group of brain nuclei
contains the pineal gland (pineal body)
130
pineal gland
influenced by the hypothalamus
secretes the hormone melatonin
contributes to control of circadian rhythms
