Central Nervous System - Lecture Notes - A&P 2

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What does the CNS consist of?
* Brain
* Spinal Cord
What happens during the first 26 days of embryonic development?
* Ectoderm thickens to form neural plate
* Neural plate invaginates forming the neural groove
* Neural groove fuses dorsally to form the neural tube
What are the 3 primary brain vesicles (embryonic development)?
* Prosencphalon
* Mesencephalon
* Rhombencephalon
What does an embryo's Prosencephalon become?
The Forebrain
What does an embryo's Mensencephalon become?
The Midbrain
What does an embryo's Rhombencephalon become?
The Hindbrain
What are the secondary brain vesicles (embryonic development, usually appearing after week 5 gestation)?
* Telencephalon & Diencephalon (developed from prosencephalon)
* Mesencephalon (midbrain)
* Metencephalon & Myelencephalon (developed from hindbrain)
Forebrain & Telencephalon are to an embryo as...........
..........Cerebrum is to an adult
Forebrain & Diencephalon are to an embryo as.........
........Diencephalon is to an adult
What does the adult diencephalon consist of?
* Thalamus
* Hypothalamus
* Epithalamus
Midbrain & Mesencephalon are to an embryo as..........
.......Midbrain (part of brainstem) is to an adult
Hindbrain & Metencephalon are to an embryo as.........
.........Pons & Cerebellum are to an adult
Hindbrain & Myelencephalon are to an embryo as..........
.........Medulla Oblongata is to an adult
What are the adult neurocoel regions of the brain?
* Telecephalon
* Diencephalon
* Mesencephalon
* Metencephalon & Myelencephalon
What ventricles are in the telencephalon?
Lateral ventricles
What ventricle is in the diencephalon?
Third ventricle
What is the in the mesencephalon that connects the forebrain to the hindbrain?
The cerebral aqueduct
What ventricle is in the metencephalon & the myelencephalon?
Fourth ventricle
What protects the brain?
* Bone
* Meninges
* Cerebrospinal fluid
* Blood-Brain barrier (shields brain from harmful substances)
What order are the brain meninges in, from top to bottom?
* Dura Mater
* Arachnoid Mater
* Pia Mater
Dura Mater, of the brain
* Outer meninges layer
* Thickest layer
Arachnoid Mater, of the brain
* Middle meninges layer
* Layer with most structure to it
Pia Mater, of the brain
* Innermost meninges layer
* Thinnest layer
* Goes with the contours of the brain
Cerebrospinal Fluid Properties
* Watery solution
* Less protein & different ion concentrations that plasma
* Forms liquid cushion, giving buoyancy to CNS organs, including skull
* Nourishes brain & carries chemical signals throughout it
* Allows brain to float inside skull
Choroid Plexus Properties
* Clusters of capillaries
* Form tissue & fluid filters
* Hand from roof of each ventricle
* Ion pumps that alter ion concentrations of CSF
* Filter & remove waste
Blood Brain Barrier Properties
* Protective mechanism that helps maintain a stable environment for the brain
* Bloodborne substances separated from neurons
Bloodborne substances separated from neurons by:
* Continuous endothelium of capillary walls
* Relatively thick basal lamina
* Bulbous feet of astrocytes
~ helps maintain barrier
Cerebral hemisphere properties:
* Forms superior part of the brain
* Makes up 83% of the brain's mass
* Hemisphere divisions: left, right, front, back
* Has 3 basic regions
Three basic cerebral hemisphere regions:
* Cortex (gray matter)
* White matter (inner material)
* Basal nuclei (gray matter) (in the center)
Cerebral Cortex properties:
* Superficial gray matter
* Accounts for 40% of brain mass
* Enables sensation, communication, memory, understanding, & voluntary movements
* Each hemisphere acts contralaterally
* Hemispheres not equal in function
* No functional area acts alone
Purpose of longitudinal sulcus:
To separate right from left brain
What are the purpose of Gyri & Sulci?
To increase surface area
Are Gyri in or out?
They are out
Are Sulci in or out?
They are in
Trick to remember Gyri & Sulci
Gyri grow & Sulci sink
The 3 fibers of white matter of the brain
* Association Fibers
* Commissural Fibers
* Projection Fibers
Commissural Fibers
* Connect right & left hemispheres
* Corpus commissure at top
* Anterior commissure at bottoms
Projection Fibers
* Form cerebrum to rest of brain
* Connects cerebral cortex to anything that isn't cerebrum
* "projects from top to bottom"
Basal Nuclei Properties
* Masses of gray matter found deep within the cortex within the cerebrum
* Corpus Stratum
What the Corpus Stratum is composed of:
* Caudate nucleus
* lentiform nucleus (putamen & globus pallidus)
* Amygdaloid body (limbic system)
Limbic System
Emotional responses
What are the functions of the basal nuclei?
* Influence muscular activity
* Regulate attention & cognition
* Regulate intensity of or stereotyped movements
* Inhibit antagonistic & unnecessary movement
Functional areas of the Cerebral Cortex
* Motor areas
* Sensory areas
* Association areas
What is the function of motor areas?
To control voluntary movement
What is the function of sensory areas?
Conscious awareness of sensation
What is the function of association areas?
To integrate diverse information
Different motor areas of the Cerebral Cortex
* Primary motor cortex
* Premotor cortex
* Broca's Area
* Frontal eye field
Primary motor cortex properties
* Located in the precentral gyrus
* Pyramidal cells whose axons make up the corticospinal tracts
* Allows conscious control of precise, skilled, voluntary movements
Premotor Cortex properties
* Located anterior to the precentral gyrus
* Controls learned, repetitious, or patterned motor skills
* Coordinates simultaneous or sequential actions
* Involved in the planning of movements
Broca's Area properties
* Located anterior to the inferior region of the premotor area
* Present in only one hemisphere (usually the left)
* A motor speech area that directs muscles of the tongue
* Is active as one prepares to speak
Frontal Eye Field properties
* Located anterior to the Premotor Cortex & superior to Broca's Area
* Controls voluntary eye movement
* Helps control the 6 muscles associated with the eyes
Sensory Areas properties
* Posterior to central sulcus
* Primary somatosensory cortex
* Somatosensory association cortex
* Visual and auditory areas
* Olfactory, gustatory (taste), & Vestibular (balance) cortices
Primary Somatosensory Cortex properties
* Located in the post-central gyrus
* Receives information from the skin and skeletal muscles
* Exhibits spatial discrimination
Somatosensory Association Cortex
* Located posterior to the primary somatosensory cortex
* Integrates sensory information
* Forms comprehensive understanding of the stimulus
* Determines size, texture, & relationship of parts
Primary Visual (Striate) Cortex properties
* Receives visual information from the retinas
* Very tip of Occipital Lobe
* Most of it buried in the calcarine sulcus
Visual Association area
* Surrounds the primary visual cortex
* Interprets visual stimuli
Primary Auditory Cortex
* Located at the superior margin of temporal lobe
* Receives information related to pitch, rhythm, & loudness
Auditory Association Area
* Interprets info
* Located posterior to primary auditory cortex
* Stores memories of sounds
* Permits perception of sounds
* Wernicke's Area
Auditory Association Areas
* Prefrontal Cortex
* Language areas
* General interpretation area
* Visceral association area
Prefrontal Cortex
* Located in anterior portion of frontal lobe
* Involved with intellect, cognition, recall, & personality
* Necessary for judgment, reasoning, persistence, & conscience
* Closely linked to limbic system
Language Areas
* Wernicke's Area
* Broca's Area
* Lateral prefrontal cortex
* Lateral & ventral temporal lobe
Wernicke's Area
* Used in sounding out unfamiliar words
* Develops during reading in childhood
Broca's Area
Speech preparation & production
Lateral Prefrontal Cortex
* Language comprehension
* Word analysis
Lateral & Ventral Temporal Lobe
* Reading
* Coordinate auditory & visual aspects of language
Lateralization of Cortical Function
* Each hemisphere has abilities not shared with respective side
* Cerebral dominance
* Left Hemisphere
* Right Hemisphere
Left Hemisphere
Controls language, math, & logic
Right Hemisphere
Controls visual-spatial skills, emotion, & artistic skills
Diencephalon anatomy
* Central core of forebrain
* 3 paired structures: thalamus, hypo & epi thalamus
* Encloses the third ventricle
Groups of the Thalamic Nuclei
* Anterior Group
* Medial Group
* Ventral Group
* Posterior Group
* Lateral Group
Function of the Hypothalamus
* Endocrine system
* Perception of pleasure, fear, & rage
* Maintain body temperature
* Regulates sleep cycle
**This is the first physical connection between endocrine & nervous system
Epithalamus Properties
* Most dorsal portion of diencephalon
* Forms roof of third ventricle
* Pineal glad
* Choroid Plexus
Pineal Glad functions
* Secretes Melatonin
* Involved with sleep regulation, sleep-wake cycles, & mood
Choroid Plexus
* structure that secretes CSF
Brain Stem properties
* Consists of Midbrain, Pons, & Medulla Oblongata
* Controls automatic behaviors necessary for survival
* Provides the pathway for tracts between higher & lower brain centers
* Associated with 10 of the 12 pairs of cranial nerves (all but olfactory & optic)
Midbrain properties
* Between diencephalon & pons
* Has 3 structures: Cerebral Peduncles, Cerebral Aqueduct, & Various nuclei
Cerebral Peduncles
Two bulging structures that contain descending pyramidal motor tracts
Cerebral Aqueduct
Hollow tube that connects the third & fourth ventricles
Various Nuclei
* Superior colliculi
* Inferior colliculi
* Corpora quadrigemina
* Substantia nigra
Pons properties
* Bulging brainstem region between Midbrain & Medulla Oblongata
* Forms part of anterior wall of fourth ventricle
* Has fibers that:
~Connects higher brain centers & spinal cord
~Relays impulses between motor cortex & cerebellum
Medulla Oblongata properties
* Last part of brain before spinal cord
* Most inferior part of brain stem
* Forms ventral wall of fourth ventricle
* Contains a choroid plexus of fourth ventricle
* Cardiovascular control center
* Other centers include: vomit regulation, hiccupping, swallowing, coughing, & sneezing
Cerebellum Properties
* Second larges structure of the brain
* makes up 11% of brain's mass
* provides precise timing & appropriate patters of skeletal muscle patterns
* Subconscious activity
* Superior peduncles, middle peduncles, & inferior peduncles
* Balance
Superior Peduncles
Connects Cerebellum to Midbrain
Middle Peduncles
Connect the Pons to Cerebellum
Inferior Peduncles
Connect the Medulla to the Cerebellum
What does the Amygdala deal with?
* Part of limbic system
* Anger
* Danger
* Fear responses
What role does the Cingulate Gyrus play?
*Expresses emotions via gestures
* Resolves mental conflict
Reticular Activating System (RAS)
Sends impulses to Cerebral Cortex to keep it conscious & alert
Properties of brain waves
* Continuous electrical activity
* Can be recorded by an electroencephalogram (EEG)
* Each person's are unique
* Continuous train of peaks & troughs
* Expressed in Hertz
* 4 different types
Alpha Waves
* Regular & rhythmic
* Low-amplitude
* Slow
* Synchronous waves, indicates "idling brain"
Beta Waves
* Rhythmic
* More irregular waves
* Occurs during the awake & mentally alert state
Theta Waves
* More irregular than alpha waves
* Common in children
* Abnormal in adults
Delta Waves
* High-amplitude waves
* Seen in deep sleep
* Also seen when RAS is damaged
Cerebrovascular Accidents (Strokes)
* Caused when blood circulation to brain is blocked & brain tissue die
* Most commonly caused by blockage of cerebral artery
* Could also be caused by brain compression by hemorrhage or edema & atherosclerosis
* Long lasting
Transient Ischemic Attacks (TIAs)
* Temporary episodes of reversible cerebral ischemia
* Tissue plasminogen activator (TPA) is the only approved treatment for stroke
* Short lasting
* Reversible
Alzheimer's Disease
* Degenerative brain disorder
* Progressive
* Results in dementia
* Recently linked to 2 chromosomes
Parkinson's Disease
* Degenerative brain disorder
* Degeneration of dopamine-releasing neurons of the substantia nigra
* Substantia Nigra turns to al dopa which turns to dopamine
Huntington's Disease
* Degenerative brain disorder
* Fatal
* Inherited (autosomal dominate)
* Caused by accumulation of the Huntington protein, which leads to degeneration of basal nuclei
Spinal Cord properties
* Goes from Medulla to foramen magnum
* CNS tissue is enclosed within vertebral column from foramen magnum to L1
* Provides 2-way communication to & from brain
* Protected by bone, meninges, & CSF
* Epidural space (between vertebrae & dura mater)
* Has 31 pairs of nerves (that attach to cord by paired roots)
Cervical & Lumbar Enlargements
Sites where nerves serving the upper & lower limbs emerge
Cauda Equina
* Translates to "horse's tail"
* Collection of nerve roots at the inferior end of vertebral canal
Gray Matter & Spinal Roots properties
* Makes "H" or butterfly pattern
* Consists of soma, unmyelinated processes, & neuroglia
* Has 4 components: gray commissure, dorsal horns, ventral horns, lateral horns
Gray Commissure
* Connects masses of gray matter
* Encloses central canal
Dorsal Horns
Interneurons
Ventral Horns
* Interneurons
* Somatic motor neurons
Lateral Horns
Sympathetic nerve fibers
Finiulus
White matter around gray matter
Gray Matter Organization
* Dorsal half
* Ventral half
* Dorsal & ventral roots fuse laterally, forming spinal nerves
* 4 zones: Somatic sensory, visceral sensory, visceral motor, somatic motor
Ganglia
Cluster of cell bodies
Dorsal half contains:
* Sensory roots
* Ganglia
Ventral half contains:
Motor roots
Spinal Cord White Matter properties
* Has fibers that run in 3 directions (ascending, descending, transversely)
* Divided into 3 funiculi (posterior, lateral, anterior)
* Each finiculus contains several fiber tracts
White matter funiculus fiber track properties
* Their names reveal origin & destination
* Composed of axons with similar functions
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