Lecture 2 Anatomy (CNS Overview) Flashcards
What is the brain made up of?
100 billion neurons
1 trillion neuroglia
-Neurons are primarily interneurons (associative) involved in associative function (intellect, emotions, behavior, and memory)
Brain development:
Describe the stages -
Ectoderm -> neural fold -> neural tube -> 3 primary vesicles -> 5 secondary vesicles
5 Principle parts of the brain (derived from secondary vesicles):
- Telencephalon - cerebral hemispheres, basal ganglie, limbic system
- Diencephalon - thalamus, hypothalamus, epithalamus
- Mesencephalon (midbrain) - cerebral peduncles, corpus quadrigemina
- Metencephalon - cerebellum, pons
- Myelencephalon - medulla oblongata
Brain stem (parts):
- Medulla oblongata (myelencephalon)
- Pons
- Midbrain (mesencephalon)
Protective covering of brain:
Start with scalp -
1. Scalp - skin, CT, aponeurosis, lipid, and periosteum 2 Cranial bones (skull) 3. Epidural space with far 4. Dura matter 5. Subdural space - with interstitial fluid 6. Arachnoid mater 7. Subarachnoid space - with CSF 8. Pia matter
Folds of the dura matter (hold brain in place)
Falx cerebri -
Falx cerebelli -
Tentorium cerebelli -
Falx cerebri - sagittal between cerebral hemispheres
Falx cerebelli - sagittal between cerebellar hemispheres
Tentorium cerebelli - transverse between cerebrum and cerebellum
What is brain’s normal fuel source and how much does it use during rest?
Glucose (unable to store)
Uses 20% of bodies oxygen and glucose
Blood brain barrier composed of 3 parts:
- Tight junctions between blood vessel endothelial cells
- Continuous endothelial cell basement membrane
- Astrocytes (neuroglia) wrapped around endothelial cell basement membrane
What can/can’t cross BBB?
Not found in which organs (give general name and name 3 organs)?
Can - lipid soluble, hydrophobic substances Can't - Water, hydrophilic substances Circumventricular organs: 1. Hypothalamus 2. Pituitary 3. Pineal Gland
Medulla Oblongata (Myelencephalon): Overall Functions -
- Contains nuclei for vital centers and cranial nerves
2. Signal Propagation via ascending (sensory signals) and descending (motor signals) tracts
Medulla Oblongata (Myelencephalon): Nerve tracts -
Nerve tracts - (bundles of axons) both sensory (ascending) and motor (descending)
Medulla Oblongata (Myelencephalon): Pyramids -
Pyramids - paired ventral surface ridges that contain motor descending tracts
Medulla Oblongata (Myelencephalon): Decussation of pyramids -
Decussation of pyramids - motor tracts from the right brain cross to control muscles on the left side and motor tracts from left brain cross to control muscles on the right side
*motor
Medulla Oblongata (Myelencephalon): Olives -
Olives - paired bulges lateral to pyramids which contain the inferior olivary nuclei which links brain and spinal cord motor signals to the cerebellum for perception of time
Medulla Oblongata (Myelencephalon): Fasciculus gracilis and fasciculus cutaneous -
Fasciculus gracilis and fasciculus cutaneous - ridges found on dorsal medulla which relay sensory ascending input to opposite side of the brain
Medulla Oblongata (Myelencephalon): Decussation of the medial lemniscus -
Decussation of the medial lemniscus - crossover of ascending sensory input to the contralateral brain hemisphere
*sensory
Medulla Oblongata (Myelencephalon): Nuclei
Nuclei - masses of neuronal cell bodies
- Vital body functions: cardiovascular, respiratory
- CN nuclei for CN 8, 9, 10, 11, & 12
Pons: Where is it found? What part of brain is it? Contains - Functions -
- Found on ventral surface of brain stem
- Apart of metencephalon with cerebellum (which is not apart of the brain stem)
Contains - CN nuclei 5, 6, 7 and ascending and descending tracts
Functions - information relay for cerebellar hemispheres
Midbrain:
Where is it found?
What CN?
- Mesencephalon
- CN 3, 4
Midbrain:
Superior colliculi -
Superior colliculi - reflex movement of eye, head, and neck to visual and other stimuli
Midbrain:
Inferior colliculi -
Inferior colliculi - reflex movement of head and neck to auditory stimuli
Midbrain:
Cerebral peduncles -
Cerebral peduncles - contain descending motor axon tracts from cerebral hemispheres to spinal cord, medulla and pons
-Ascending sensory axons going to cerebrum
Midbrain:
Cerebral peduncles -
Cerebral peduncles - contain descending motor axon tracts from cerebral hemispheres to spinal cord, medulla and pons
-Ascending sensory axons going to cerebrum
Midbrain:
Red nucleus and substantia nigra -
Red nucleus and substantia nigra - function to modify motor signals
Functions of the midbrain?
- Relay motor impulses from cerebral cortex
1. Relay sensory impulse from spinal cord to thalamus
Reticular (net) formation -
Diffuse structure, composed of areas of gray matter interspersed among areas of white matter in central portions of diencephalon, brain stem, and spinal cord
Reticular functions -
- Alerting cerebral cortex to sensory signals
- Reticular activating system function in maintaining consciousness and awakening from sleep by stimulating the cortex
- Filter sensory input to remove unimportant input (prevent sensory overload)
- Efferent motor function in maintaining muscle tone
Cerebellum:
What part of brain?
Compose of?
-Metencephalon with pons Composed of: 1. Vermis (worm) which splits the two hemispheres 2. Cerebella hemispheres 3. Peduncles
Cerebellum: Cross section anatomy Cortex - Folia - Arbor vitae nerve tracts - Cerebellar nuclei -
Cortex - gray matter
Folia - ridges
Arbor vitae nerve tracts - white matter
Cerebellar nuclei - gray matter within arbor nuclei
Cerebellar Functions:
- Smooth and coordinate cerebral control of skeletal muscle movements to facilitate complex muscle activity
- Regulate muscle tone
- Posture and balance
Diencephalon:
Composed of -
- Not part of brainstem Composed of: 1. Thalamus 2. hypothalamus 3. Epithalamus 4. Subthalamus
Diencephalon:
1. Thalamus
What is it composed of?
What are functions?
- Composed of paired masses of mixed gray nuclei and white tracts connected by intermediate mass (crossover point)
Functions: - Sensory (visual, auditory, smell, taste, somatic sensation) relay to the correct region of the cerebral cortex
- Refine motor signals with the basal nucleus
Diencephalon:
2. Hypothalamus
Function (general) -
Composed of -
- Function: maintain homeostasis
- Circumventricular organ
Composed of: - mammillary bodies visible on inferior surface
-infundibulum connects pituitary (hypophysis) to the hypothalamus
Diencephalon:
2. Hypothalamus
Specific Functions -
- Control of autonomic nervous sustem (heart, gut, bladder)
- Control endocrine system - control pituitary
- Regulate emotional behavior (limbic system)
- Regulate eating and drinking
- Control body temp
- Regulate circadian rhythms and state of consciousness
Diencephalon:
3. Epithalamus
Composed of -
Functions -
Composed of:
1. Pineal gland - endocrine gland secretes melatonin
2. Habenular nuclei (paired)
Functions:
1. Pineal gland melatonin production to set biological clock
2. Habenular - emotional response to smell
Diencephalon:
4. Subthalamus
Composed of -
Functions -
Composed of: 1. Subthalamic nuclei 2. Parts of red nuclei 3. Parts of substantia nigra Functions: 1. Connects to cerebellum and motor cortex for control of body movements
Circumventricular Organs:
What are they?
Function?
Name the 3
- Areas of brain that do not have BBB therefore are able to monitor chemical changes in blood
- Function as part of body’s internal sensory system to maintain homeostasis
- Hypothalamus, pineal, pituitary (hypophsysis)
Basal Ganglia:
What part of brain?
What does is consist of?
Function?
- Telencephalon
- Consists of paired nuclei (gray matter)
- Function in control of skeletal muscle movement (motor neuron) and muscle tone
Limbic system:
What part of brain?
Composed of what?
Describe what it is
- Telencephalon and Diencephalon
- Composed of paired nuclei, tracts, and cortex (parts of frontal/parietal/ and temporal lobes)
- Primitive brain function in emotional aspects of behaviors and memory/pain, pleasure, affection, and anger to determine feelings
Cerebrum:
Composed of -
-Telencephalon
Composed of:
1. Cerebral cortex (gray matter) - 10s of billions of associative (inter) neurons typically arranged in 6 layers to allow vertical integration
2. Cerebral white matter containing 2 types of neurons:
-Association fibers - connect diff gyri in same hemi
-Commissural fibers - connect diff gyri in opposite hemi
-Projection fibers - connect cerebrym to rest of body (sensory/motor)
Cerebrum:
Functions
- Conscious sensation (receive conscious sensory input)
- Voluntary motor activity (sends voluntary motor output)
- Higher brain function (cognition, association of sensory input with memory to produce more memory, language, abstract thought - humanity)
Cerebrum: Surface anatomy Gyri - Sulci - Fissures - Longitudinal fissure - Hemispheres - Corpus callosum -
Gyri - Ridges
Sulci - shallow grooves (valleys)
Fissures - deep grooves
Longitudinal fissure - separates R/L hemispheres (contains falx cerebri)
Hemispheres - R/L sides of cerebrum
Corpus Callosum - Large connection of commissural tracts connecting R/L hemispheres
Cerebrum: Surface anatomy Lobes - Central sulcus - Precentral gyrus - postcentral gyrus -
Lobes - frontal, parietal, temporal, occipital, insula
Central sulcus - Separates frontal and parietal lobes
Precentral gyrus - ant to central sulcus, voluntary somatomotor area
postcentral gyrus - post to central sulcus, conscious somatosensory area
Cerebrum: Surface anatomy
Lateral cerebral fissure (sulcus) -
Parieto-occipital sulcus -
Lateral cerebral fissure (sulcus) -separates frontal and temporal lobes (leads to insula)
Parieto-occipital sulcus - separates parietal and occipital lobes
Frontal Lobe -
Location
Frontal lobe - located anterior of central sulcus and medial the lateral sulcus
Frontal Lobe:
Precentral Gyrus -
Somatotopic -
Homunculus -
- Primary motor cortex controlling voluntary movement on contralateral side of the body
- Somatotopic - specific regions of the precentral gyrus control muscles in specific body regions
- Homunculus - depicts somatotopic organization of precentral gyrus and relative cortical contributions to a particular body region
Frontal Lobe:
Frontal eye field -
Broca’s area -
Frontal eye field - coordinated R andL eye movements (conjugate eye movements)
Broca’s Area - L hemisphere only (dominant hemi), coordinates motor speech
Frontal Lobe: Prefrontal cortex - Location? Input? Output? Functions?
Prefrontal cortex - rostral most part of frontal lobe (primary target for lobotomy)
- Input from all regions of cortex and limbic system
- Output to wide variety to subcortical nuclei thalamus, basal ganglia and brain stem
- Functions to regulate visceral, emotional, and cognitive (intellectual) processes
Frontal Lobe:
Cingulate Gyrus -
Cingulate Gyrus - medial surface (within longitudinal fissure) of frontal and parietal lobs
- Limbic cortex for emotional behavior, autonomic response, and learning
Insula:
Location?
Functions?
- Located within the lateral sulcus where frontal, parietal, and temporal lobes come together
- Functions in integration of sensory input for:
- Taste and olfaction
- Viscerosensation (interoreceptors)
- Pain
- Balance??
Parietal Lobe:
Post central gyrus -
Post central gyrus
- Primary sensory area - tactile and proprioceptive sensation
- Somatotopic - specific regions receive sensory input from specific body regions
- Homunculus - depicts somatotopic organization of post central gyrus and relative cortical contributions to a particular body region
Parietal Lobe:
Supramarginal and Angular gyrus -
Supramarginal and Angular gyrus - Receive visual and auditory input for perceptional discrimination and integration
Parietal Lobe:
Wernicke’s area
Location?
Function?
- Located in both parietal (supramarginal and angular gyri) and temporal lobes of the left hemi (dom hemi)
- Functions in comprehension of spoken language and works with Broca’s area to formulate a verbal response
Parietal Lobe:
Superior parietal lobe -
- Association area integrating sensory and motor areas to program complex motor responses
Occipital Lobe:
Superior medial surface -
Visual association cortex (nothing on back)
- Located caudal to the parietal-occipital sulcus on the medial border
Superior medial surface - (next to longitudinal fissure) primary visual cortex
Temporal Lobe: Transverse gyri Heschl - Superior temporal gyrus - Middle temporal gyrus - Inferior temporal gyrus - Parahippocampal gyrus and uncus -
Transverse gyri Heschl - medial aspect of superior temporal gyris = primary auditory cortex
Superior temporal gyrus - auditory association cortex
Middle temporal gyrus - perception and analysis of motion in the visual field
Inferior temporal gyrus - facial recognition in response to visual input
Parahippocampal gyrus and uncus - located on the inferior surface of temporal lobe, function with limbic system
Hemispheres: (separated and connected by?)
- Separated by longitudinal fissure
- Connected by commissural fibers
Hemispheres:
Hemispheric localization -
Hemispheric localization - functional difference exist between hemispheres = cerebral dominance
Describe L vs R Hemi
Left - language interpretation and execution, numerical and scientific (abstract), reasoning
Right - musical, artistic, special and pattern interpretation, facial recognition, emotional content of language, mental images of visual, auditory, somatic, taste, and olfactory input
Cerebral dominance due to -
- Unequal cortical representation of function in homologous regions of the 2 hemis
- Diminished commissural cross connections between regions
- Visual cortex: temporal eye field is uncrossed
- Primary motor and sensory areas of the distal arm (handedness) and leg
Arterial blood supply:
Origin of R internal carotid A
Origin of R internal carotid A: L ventricle -> ascending aorta -> brachiocephalic A -> R common carotid -> R internal carotid
Arterial blood supply:
Origin of L internal carotid A
Origin of L internal carotid A -> L ventricle -> ascending aorta -> aortic arch -> L common carotid -> L internal carotid
Arterial blood supply:
Origin of R vertebral A
Origin of R vertebral A -> L ventricle -> ascending aorta -> brachiocephalic A -> R subclavian a -> R vertebral a
Arterial blood supply:
Origin of L vertebral A
Origin of L vertebral A-> L ventricle -> ascending aorta ->aortic arch -> L subclavian a -> L vertebral a
Course of Internal Carotids through skull:
Start with External opening of carotid canal in temporal bone ->
Carotid canal in petrous portion of temporal bone -> Internal opening of carotid canal in temporal bone -> crosses over foramen lacerum -> runs along base of sella turcica in carotid groove ->Turns up to join optic nerve at prechiasmatic groove
Branches of internal carotids:
Opthalmic -
Opthalmic - runs with CN 2 supplying blood to the choroid/retina of the eye via central artery of the retina
Branches of internal carotids:
Posterior communicating A -
Posterior communicating A - part of circle of willis supplying the pituitary (hypophysis), infundibulum, hypothalamus, and thalamus (diencephalon)
Branches of internal carotids:
Anterior choroidal A
Anterior choroidal A - Arises near middle cerebral a to supply choroid plexus of lateral ventricle, optic tract, internal capsule, and globus pallidus (basal nucleus)
- Deep structures of telencephalon
Branches of internal carotids:
Anterior Cerebral A
What body regions and function would be affected by a stroke here?
Anterior Communicating -
Anterior Cerebral A - runs in longitudinal fissure above corpus callosum to medial aspect of frontal and parietal lobes
- Feet/legs
1. Anterior communicating - anastomosis between R/L anterior cerebral A
2. Other branches - to basal nucleus and limbic (deep telencephalon, inferior surface of frontal lobe = deep structures in telencephalon)
Branches of internal carotids:
Middle Cerebral Artery
Middle Cerebral Artery - runs in lateral sulcus to:
- Lateral frontal lobe (Broca’s, trunk, arm, face of precentral gyrus)
- Lateral parietal (Wernicke’s, trunk, arm, face of postcentral gyrus)
- Insula (limbic: pain, olfaction, taste)
- Lateral occipital
- Medial/lateral temporal (primary auditory)
- Sub-cortical deep structures (basal ganglia, internal capsule, limbic structures)
Course of Vertebral Arteries:
Start with Transverse foramen of cervical vertebra->
From C1 transverse foramen -> bends medial to foramen magnum -> passes through foramen magnum -> ascends clivus -> R/L vertebrals fuse into basilar A
Branches of Vertebral A:
Anterior Spinal A -
Posterior inferior cerebellar -
Posterior Spinal A -
Anterior Spinal A - to medial medulla (pyramids, medial lemniscus, MLF)
Posterior inferior cerebellar - Lateral medulla (spinothalamic tract, spinocerebellar tracts, spine nucleus of CN 5)
Posterior Spinal A - Branches of posterior inferior cerebellar a to dorsal medial medulla (cuneatus and gracilis)
Branches of basilar A: Anterior Inferior cerebellar - Labyrinthine A - Pontine A - Superior cerebellar A -
Anterior Inferior cerebellar - to cerebellum and pons
Labyrinthine A - enters internal acoustic meatus to cochlea and vestibular apparatus
Pontine A - to pons
Superior cerebellar A - cerebellum ,, pons, and midbrain
Branches of basilar A:
Posterior cerebral A -
Posterior cerebral A -
- Cortex - medial (primary visual) and inferior occipital, inferior temporal
- Subcortical structures - midbrain, subthalamus, and thalamus
Circle of Willis -
What arteries makes up?
Circle of Willis - anastomosis between internal carotid a’s and basilar a
- Anterior communicating A
- Anterior cerebral a
- Posterior communicating A
- Posterior cerebral A
Dural Artery -
Middle meningeal from maxillary A (off external carotid) via foremen spinosum
Venous Drainage of Brain:
Dural Sinuses - (4)
Dural Sinuses:
- Superior sagittal sinus - formed from superior margins of falx cerebri
- Inferior sagittal sinus - formed from inferior margins of falx cerebri drains into ->
- Straight sinus formed from junction of falx cerebri and tentorium cerebella
- Occipital sinus - formed by junction of falx cerebella at attachment to occipital bone
All dural sinuses drain into ->
Confluence of sinuses - intersection of superior sagittal, straight, transverse, and occipital sinuses ->
- Transverse sinus formed from junction of tentorium cerebella with occipital bone
- Superficial veins
- > sigmoid sinus - continuation of transverse sinus in groove at junction of occipital and temporal bones
- > Internal Jugular vein
Venous Plexi:
Cavernous sinus Pterygoid sinus Basilar Superior and inferior petrosal -> drain into venous sinuses or jugular veins
Spinal Cord:
Runs from where to where?
Ends at…
Runs from medulla oblongata at foramen magnum/C1 (atlanto occipital joint) to L1/L2 intervertebral joint ending in conus medullaris
Protective coverings of spinal cord:
Skin -> hypodermis -> muscle
epidural space - with fat
dura mater - continuous with spinal nerve epineurium
subdural space - interstitial fluid
arachnoid mater
subarachnoid space - csf
pia mater - denticulate lig link pia to arachnoid mater
filum terminal links pia of conus medularis to sacrum/coccyx
31 pairs spinal nerves (how many per area?)
8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal
Dorsal roots from spinal nerves -
- Sensory axons
- Somatosensory neurons
1. touch and proprioception are located medially
2. pain and temp are located laterally - viscerosensory
Ventral roots from spinal nerves -
- Motor axons
Somatomotor neurons (ventral horn)
Autonomic (viscero) motor neurons (lateral horn)
How do spinal nerves exit the spinal cord (what foramen)?
Via intervertebral foramen
Cauda Equina -
What regions is it found in?
What is the space that is resides known as?
- Roots of spinal nerves from lumbar, sacral, and coccygeal regions
- Resides in enlarged subarachnoid space known as the lumbar cystern
Cervical enlargement -
Lumbar enlargement -
Cervical enlargement - C5-T1 brachial plexus
Lumbar enlargement - L1-S2 lumbosacral plexus
How is the spinal cord connected to the vertebral column and skull?
Denticulate Ligaments
Filum terminal:
-pial portion = filum terminal internum
-dural portion = filum terminal externum
Movement of spinal cord: Trunk extension - Trunk flexion - 1. Unfolding of axon within endoneurium -> 2. Elastic deformation ->
Trunk extension - reduces stretch of cord
Trunk flexion - increase stretch
-Flex head at neck = cord stretches 10% post/6% ant
-Unfolding of axon within endoneurium -> 70% increase of length
-Elastic deformation (stretch thin) -> 30%
Movement of spinal cord:
Trunk Rotation -
Trunk Rotation - stretches nerve roots and spinal nerves around bones forming the intervertebral foramen
Nerves/roots protected by:
1. Extra space of intervertebral foramen accommodates stretch (spinal n/roots occupy 23-50% of space)
2. Epidural fat in intervertebral space
3. Covering of dura mater
Spinal cord cross section anatomy:
Grooves -
Grooves:
Anterior median fissure
Posterior median fissure
Spinal cord cross section anatomy:
Gray matter -
Gray matter - H shaped central core containing neuron and neuroglia cell bodies, and unmyelinated neuron processes (axons and dendrites)
Spinal cord cross section anatomy (Gray matter):
Dorsal (posterior) Horn -
Dorsal (posterior) Horn - composed of interneurons involved in sensory signaling
Spinal cord cross section anatomy(Gray matter):
Ventral (anterior) Horn -
Ventral (anterior) Horn - composed of somatomotor neurons and interneurons (Renshaw cells) involved in motor signaling somtotopically organized
- Medial ventral horn - axial muscles
- Lateral ventral horn - appendicular muscles
- posterior ventral horn - flexors
- Anterior ventral horn - extensors
Spinal cord cross section anatomy(Gray matter):
Lateral (intermediolateral) Horn -
Lateral (intermediolateral) Horn -
T1-L2 sympathetic preganglionic neurons
S2-S4 parasymp preganglionic neurons
Spinal cord cross section anatomy(Gray matter):
Rexed’s Laminae -
Rexed’s Laminae - 10 histologic/functional regions of gray matter in dorsal and ventral horn
lamina 1 - marginal layer for noxious stimuli
lamina 2 - substantia gelatinosa for noxious stimuli
Spinal cord cross section anatomy(Gray matter):
Grey Commissure -
Grey Commissure - connection between right and left gray matter
- Allows for signals to cross to opposite side
Spinal cord cross section anatomy:
White matter -
White matter - contains ascending (sensory) and descending (motor) tracts (fasciculi) which are bundles of myelinated axons with a similar origin and terminal destination
Spinal cord cross section anatomy(White matter):
Dorsal (post) column (funiculus) -
Lateral Column (funiculus) -
Anterior (ventral) column (funiculus) (nothing on other side)
Propriospinal -
Dorsal (post) column (funiculus) - bundle of tracts (fascicula)
Lateral Column (funiculus) - posterior and anterior
Anterior (ventral) column (funiculus)
Propriospinal - axons that begin and end within the cord providing interconnection between tracts and gray matter for context
Spinal cord cross section anatomy:
Central Canal -
Central canal - continous with fourth ventricle of the brain
- contains csf
Spinal Cord function -
Describe function
Flow
- Nerve impulse propagation between periphery (primarily trunk and appendiges) and the brain occurring in tracts of white matter
- Flow of impulses is two directional from periphery to brain (ascending sensory) and brain to periphery (descending motor)
- Somatic reflex control center
Spinal cord vasculature:
1. Primary arterial supply:
- Primary arterial supply:
Cervical - vertebral arteries
Thoracic - posterior intercostal a
Lumbar - Lumbar a
Spinal cord vasculature:
2. Spinal branches off primary supply -
- Branch into dorsal and ventral segmental arteries that form:
1. Ant spinal a to deep ant cord regions
2. 2 posterior spinal a to feep posterior cord regions
3. Ant/post radicular to superficial spinal cord regions
Spinal cord vasculature:
Veins -
- Anterior Median Spinal v
- Anterolateral spinal v
- Posteromedian spinal v
- Posterolateral spinal v
