Neural Tissue Anatomical subdivisions of NS Made up of neurons and neuroglia cells www.freelivedoctor.com
Functional Overview of NS
Integration, processing and coordination of sensory data and motor commands
Sensory or afferent division with sensory neurons. Brings sensory info to CNS. Begins as receptors, ends in?
Motor or efferent division with motor neurons. Brings motor commands to peripheral tissue. Ends at effector cells.
Peripheral Nervous System www.freelivedoctor.com
Cellular Organization of Neural Tissue
Two cell types:
General Neuron Structure
Cell body or Soma with Perikaryon
Axon with axon hillock
Astrocytes : largest & most numerous
structural framework & repairs
regulation of ions, nutrients, gases
Smaller than astrocyte
Produce myelin in CNS (white matter vs. gray matter!)
Myelin = ?
Phagocytosis of ?
# during infection or injury
Lining of ventricles & central canal
Some regions ciliated
Some specialized to produce CSF
Schwann Cells and Peripheral Axons
Responsible for myelination, but surround all peripheral axons!
Involved in repair mechanism after injury Wallerian Degeneration
Structural Neuron Classification
Also called pseudounipolar
Axon hillock See fig. 13-10 www.freelivedoctor.com
Structural Neuron Classification cont. . .
Rare, but important in special senses
All motor neurons
Functional Neuron Classification
1) somatic vs. visceral sensory or afferent
monitoring of ?
2) somatic vs. visceral motor or efferent carry instructions to ?
3) Inter- or association neurons
Site of communication between two nerve cells or nerve cell and effector cell
neuro-effector junctions (example?)
Electrical vs. chemical synapses
Chemical Synapse vs. Electrical Synapse
Space between two cells
Signal transduction via NT
Direct physical contact between cells = gap junctions
Direct signal transduction
Rare, but occurs in CNS and heart
Chem. Synapse Structure
Axon terminal of presynaptic cell
Dendrite or cell body of postsynaptic cell
Divergence - One neuron synapses with several, effectively "spreading the word".
Convergence - Several neurons synapse with a single neuron, concentrating the input.
Serial processing - step-wise, sequential
Parallel processing - simultaneous processing of different information
Anatomical Organizatin of NS
Collections of cell bodies - ganglion in PNS, center or nucleus in CNS
Bundles of axons - tracts in CNS, nerves in PNS
“ White” = myelinated axons, both nerves and tracts
“ Gray” = non-myelinated material, dendrites, synapses and cell bodies as well as nonmyelinated axons. In CNS – nucleus; in PNS - ganglia
Brain and Cranial Nerves
Discuss the organization of the brain, including the major structures and their functions
Describe the meninges of the spinal cord and brain, and integrate the formation and flow of CSF with this information.
Describe the structures that constitute the BBB and their functions
Review the cranial nerves, again giving a brief function of each.
Major Brain Subdivisions
Telencephalon (= Cerebrum)
Diencephalon (Thalamus and hypothalamus)
Metencephalon (Pons and cerebellum)
Myelencephalon (= Medulla oblongata)
Gray & White Matter Organization
In brain stem similar to spinal cord ( nuclei around ventricles, tracts on outside)
In cerebrum and cerebellum : white matter covered with layer of neural cortex (grey)
1. Dura mater - strong, "tough mother"
a. falx cerebri
b. falx cerebelli
c. tentorum cerebelli
2. Arachnoid - spidery, holds blood vessels 3. Pia mater - "delicate mother"
Arachnoid granulations: This is where the CSF produced in the choroid plexuses of the ventricles and which has circulated into the subarachnoid space is reabsorbed. Longitudinal fissure
CSF filled chambers
Communicating with central canal of spinal cord
Lined by ependymal cells
Formation in ventricles by specialized ependymal cells of choroid plexuses (~500 mL/day; total volume ~ 150 mL)
transport medium, in
buoyancy (floats the brain)
CSF circulation: Ventricles -> central canal -> subarachnoid space
Reabsorption into circulation via arachnoid granulations into superior sagittal sinus.
CSF: Cerebro-Spinal Fluid Fig 15.6
Blood Brain Barrier (BBB)
what is it?
3 areas in brain don’t have BBB
portion of hypothalamus
pineal gland (in diencephalon)
Two hemispheres separated by longitudinal fissure
Gyrus (gyri) separated by sulcus (sulci)
Major lobes named after overlaying bones
Cerebral Hemispheres . . .
. . have functional regions (motor, sensory and association areas)
. . . have some functional differences (in spite of anatomical resemblance) -> Lateralization of cortical functioning
. . . receive information and generate commands for opposite side of body
Cerebral Cortex and Central White Matter
Gray surface (cortex) with white tracts internally
Commissures – connect corresponding gyri of the two hemispheres
1) corpus callosum
2) anterior commissure
Projection tracts (fibers) – connect more or less vertically
Association tracts (fibers) – connect one gyrus to another in the same hemisphere
Basal (or cerebral) Nuclei Misnomer: basal ganglia Gray matter internal to the cerebral cortex, below floor of lateral ventricles. Function: modulate motor output from the cerebral cortex. Subconscious control of skeletal muscle tone and coordination of learned movement patterns. Parkinson's disease is caused by the loss of at least 80% of the dopaminergic neurons in basal nuclei and substantia nigra (resting tremor) Fig 15.11
Diencephalon Epithalamus Pineal gland - produces melatonin, sets diurnal cycles Thalamus (~12 nuclei) Hypothalamus Just superior to optic chiasma Infundibulum - connects to pituitary gland Some functions: Control of autonomic nervous system Coordination of nervous and endocrine systems Secretion of hormones - ADH and oxytocin
Corpora quadrigemina = 2 pairs of sensory nuclei
Superior colliculi (relay station for visual information)
Inferior colliculi (relay station for auditory information
Substantia nigra - regulates motor output
Cerebral peduncles - ascending and descending tracts to thalamus
Nuclei of ori for CN III and IV
Metencephalon: Cerebellum Hemispheres and lobes Cortex -gray surface with folia - fine ridges and sulci - grooves between the ridges Purkinje cells , axons of which become arbor vitae (white matter) in center Regulation of posture and balance
O: sensory from taste receptors of anterior 2/3 of tongue / motor from pons
D: Sensory to sensory nuclei of pons / motor muscles of facial expression, visceral motor to tear gland.
Vestibulocochlear (N VIII)
Glossopharyngeal (CN IX) C: mixed O: sensory from posterior 1/3 of tongue / motor from medulla oblongata D: medulla / muscles for swallowing, parotid gland
Vagus (N X)
O: Sensation from pharyngeal area and outer ear / motor from medulla
D: Sensory to medulla / visceral motor to thoracic and abdominal cavities and their organs. Major motor pathway for ANS
Accessory (N XI) and
O: Motor nuclei of medulla and spinal cord
D: Swallowing, trapezius & scm muscles
Hypoglossal (N XII)
O: Motor nuclei of medulla
D: Tongue musculature
Spinal Cord and Spinal Nerves Explain spinal cord anatomy, including gray and white matter and meninges (give the general functions of this organ). Discuss the structure and functions of the spinal nerves and plexuses. Describe the structural components of reflexes.
Resides inside vertebral canal
Extends to L1/ L2
31 segments, each associated with a pair of dorsal root ganglia
Adult spinal cord:
1. Cervical Enlargement Gray matter expanded to incorporate more sensory input from limbs and more cell bodies for motor control of limbs
Spinal Meninges 3) Pia mater 2) Arachnoid 1) Dura mater Three membranes surround all of CNS 1) Dura mater - "tough mother", strong 2) Arachnoid meninx - spidery looking, carries blood vessels, etc. Subarachnoid space 3) Pia mater - "delicate mother", adheres tightly to surface of spinal cord
Inferior End of Spinal Cord
Conus medullaris - inferior end of spinal cord proper
Cauda equina - individual spinal nerves within spinal canal
Filum terminale - filamentous end of meninges, "tie-down"
Lumbar Puncture (= Spinal Tap) For clinical examination of CSF or administration of radiopaque dyes, drugs and sometimes anesthetics However: mostly “epidurals” for anesthetics L3 L4
Organization of Cord Cross Section
Gray matter - interior horns
posterior - somatic and visceral sensory nuclei
anterior (and lateral) gray horns – somatic and visceral motor control
gray commissures - axons carrying information from side to side
White matter - tracts or columns
posterior white column -
anterior white column
lateral white column
anterior white commissure
ascending tracts - sensory toward brain
descending tracts - motor from brain
Peripheral Nerves Definition: bundles of axons. AKA tracts in CNS Organization – coverings: Epineurium wraps entire nerve Perineurium wraps fascicles of tracts Endoneurium wraps individual axons
Anatomy of a Peripheral nerve Function: sensory - afferent motor - efferent mixed - contains axons of both
Organization of Spinal Nerves:
1. Root – inside vertebral canal
a. dorsal sensory root with a ganglion
b. ventral motor
2. Mixed spinal nerve
a. dorsal - mixed to skin and muscles of back
b. ventral - mixed “spinal nerve” to ventrolateral body surfaces and limbs
c. white ramus communicans motor ANS
d. gray ramus communicans motor ANS
1. Fig 14-7
Sensory innervations by specific spinal nerves Each pair of spinal nerves monitors specific region of body surface.
Clinical significance ?
4 Principal Plexuses Braids of ventral rami of cervical, thoracic, lumbar or sacral spinal nerves Cervical Plexus Phrenic nerve - innervates diaphragm
Autonomic Division of NS Compare and contrast the structures of the sympathetic and the parasympathetic divisions, including functions and neurotransmitters. Show the levels of integration in the ANS, and compare these with the SNS. www.freelivedoctor.com
Overview of ANS
Pathway for Visceral Motor Output
ANS has two antagonistic divisions:
ANS output always involves two neurons between spinal cord (CNS) and effector.