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BioBases Exam #1 Study Guide
Nervous System Organization and Development
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General Nervous System Organization
Central Nervous System (CNS)
1) Structures:
(a) Brain
(b) Spinal Cord
Peripheral Nervous System (PNS)
1) Structures:
(a) everything else besides brain and spinal cord
2) Divisions:
(a) Somatic Nervous System:
(i)
receives sensory input from periphery
(ii)
concsious control of muscles
(iii)
DEALS WITH CONSCIOUS OR WILLFUL ASPECTS OF MOVEMENT and/or
SENSATION
(b) Autonomic Nervous System:
(i)
receives unconscious sensory input from internal organs (e.g., the acid content of
stomach)
(ii)
unconcious control of movement and organs (e.g., heartbeat, breathing, reflexes)
(iii)
Controls itself – it is autonomic and will function without upper cognitive functions.
(iv)
Divisions:
 Parasympathetic: mostly inhibitory – attempts to maintain homeostasis
 Sympathetic: mostly excitatory – fight or flight response
General Anatomy of the Nervous System
Peripheral Gathering and Protection
1) endoneurium: protects solitary neurons in
the outermost periphery.
2) perinuerium: protects neurons gathered
into bundles called fascicles.
3) epineurium: protects bundles of fascicles
and blood vessles.
Organization
1) Collections of neurons with common
function:
(a) CNS: tracts
(b) PNS: nerves
2) Clumps of cell bodies:
(a) CNS: nuclei
(b) PNS: ganglia
Protection of CNS
1) Bones: skull – over 1 cm thick in places – totally
surrounds and protects brain
2) Meninges: fibrous membranes that surround and
protect the brain and spinal cord
(a) Dura Mater: the outermost covering -- “hard
mother”; very tough to puncture, cut, etc. *If
blood vessel breaks beneath dura mater =
subdural hematoma
(b) Arachnoid layer: web-like layer, has “legs” that extend into the sub-arachnoid space. The
subarachnoid space is filled with CSF.
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(c) Pia Mater: the innermost covering -- “gentle mother”. adhears closely to surface of brain; many
blood vessles run along it.
3) Cerebrospinal Fluid (CSF)
(a) Completely surrounds the brain and spinal cord – mostly water
(b) Always circulating
(c) Produced in the ventricles by the choloroid plexis
4) Blood-brain barrier: prevents certain (large) molecules from passing from blood into brain.
CNS Organization and Functions
Note: the lower and more automatic parts of the brain have 2 layers of neurons while the newest
parts have 6 layers (cortex).
Myencephalon: lower-most part of brain (stem)
1) Medulla: contains nuclei that are part of the reticular formation that control:
(a) arousal and attention
(b) heart / respiration rate
(c) smooth muscle tone (cardiovasular)
Metencephalon:
1) Pons: “bridge”
(a) part of reticular formation responsible for sleep and arousal
(b) relay nuclei between cortex and cerebellum
2) Cerebellum: “little brain”
(a) responsible for coordinated movements
(b) receives all sensory input except olfactory
(c) connected to pons
Mesencephalon: “mid-brain” – surrounds cerebral aqueduct
1) Tectum: “roof”
(a) responsible for audiovisual reactions (contains inferior and superior
colliculi)
2) Tegmentum: “covering”
(a) red nucleus: sends motor info from cortex to cerebellum and spinal cord
(b) substantia nigra: “black substance”: communicates with caudate and basil
ganglia; involved in control of voluntary movement.
(c) CONTROLS EYE MOVEMENTS
Diencephalon: “two-brains”
1) surrounds the 3rd ventricle
2) Thalamus:
(a) major relay center for senses – “gateway to the cerebral cortex”
(b) many sensory nuclei
(c) two lobes
3) Hypothalamus:
(a) performs primitive functions
(b) Autonomic control center: the FOUR F’s
(c) Hormonal control: directly or through pituitary
Telencephalon: “end-brain” forms the two cerebral hemisphers
1) Cerebral Cortex
(a) 2 hemispheres communicate through corpus collosum (posterior) and anterior commisure
(anterior)
(b) Lateral Ventricles:2 of them – where CSF is produced
(c) Limbic cortex: involved in emotion and motivation
(d) Basal Ganglia:involved in planned movement
2) Lateralization of Hemispheres:
(a) Left: usually – verbal abilities, analysis, serial behaviors
(b) Right: spatial abilities, synthesis, music, arts, emotions
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Directions and Features of Brain
Directions:
1) Posterior / Anterior: rear / front
2) Superior / Inferior: above / below
3) Dorsal / Ventral: back / front (think spinal cord or dorsal fin)
4) Caudal / Rostral: toward feet / toward nose (nostrals)
5) Lateral / Medial: toward the side / in the middle
6) ipsolateral / contralateral: same side / different sides
Brain Topography:
1) Sulcus: small dip or groove (e.g., central sulcus, parietal-occipital sulcus)
2) Fissure: large valley, deep groove (e.g., the lateral fissure, longitudinal fissure)
3) Gyrus: bump (e.g., post-central gyrus)
Landmarks:
1) Longitudinal Fissure: seperates hemispheres
2) Lateral Fissure: seperates temporal lobe
3) Central Sulcus: Divides brain in half anterior vs. posterior
(a) Precentral gyrus: anterior to the central sulcus
(i)
controls motor commands from brain – nerves leave gyrus to innvervate muscles
(ii)
aka “PRIMARY MOTOR CORTEX”
(b) postcentral gyrus: posterior to the central sulcus
(i)
receives incoming sensory information from peripheral nerves
(ii)
aka “PRIMARY SOMATOSENSORY CORTEX”
4) Parietal-Occipital Sulcus: (internal) demarcates the occipital lobe from the parietal lobe
Major Lobes:
1) Frontal Lobe: anterior to central sulcus
(a) planning, thinking executive function
2) Temporal Lobe: inferior to lateral fissure
(a) hearing, auditory processing
3) Parietal Lobe: posterior to central sulcus
(a) association area
4) Occipital Lobe: posterior of cortex
(a) visual processing
Specialization of Areas:
1) White vs. Gray Matter:
(a) White matter has myelin sheath: the axons of neurons – where information is communicated
(b) Gray matter is cell bodies: where information is processed.
2) 12 cranial nerves: e.g., olfatory, occipital, trigeminal
Spinal Cord:
1) Gray matter: the butterfly in the center.
2) White matter: surrounds gray matter – carries the tracts
3) Dorsal vs. Ventral
(a) Dorsal horns receive incoming sensory information from afferent neurons – joined at the dorsal
root ganlion
(b) Ventral horns relay outgoing motor information from CNS – to efferent neurons (whose somas
are in the ventral horns).