Ch 12 - CNS (2)

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Ch 12 - CNS (2)
2013-04-10 20:11:45
part two

part two
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  1. functional brain systems
    • networks of neurons that work together but span wide areas of brain
    • example - limbic system
  2. limbic system
    • structures on medial aspects of cerebral hemispheres and diencephalon
    • includes parts of diencephalon and some cerebral structures that encircle brain stem
    • puts emotional responses to odors (ex: skunks smell bad)most output relayed via hypothalamus

    Emotional of affective brain = amygdaloid body: recognizes angry or fearful facial expressions, assesses danger, and elicits fear resonse; cingulate gyrus: role in expressing emotions via gestures, and resolves mental conflict
  3. limbic system: emotion and cognition
    • limbic system interacts with prefrontal lobes (react emotionally to things we consciously understand to be happening; consciously aware of emotional richness in our lives)
    • hippocampus and amygdaloid body - play a role in memory
  4. brain wave patterns and EEG
    • brain waves are patterns of neuronal electrical activity generated in the cortex
    • each person's brain waves are unique
    • can be grouped into four classes based on frequency measured as hertz (Hz): alpha, beta, theta, and delta waves
    • EEG = electroencephalogram
    • records electrical activity that accompanies brain function (brain waves of the cortex)
  5. protection of the brain
    • bone (skull)
    • membranes (meninges)
    • watery cushion (cerebrospinal fluid)
    • blood brain barrier
  6. meninges
    • cover and protect CNS
    • protect blood vessels and enclose venous sinuses
    • contain cerebrospinal fluid
    • form partitions in skull

    3 layers: dura mater; arachnoid mater; pia mater
  7. dura mater (=tough mother)
    • strongest meninx
    • two layers of fibrous connective tissue (around brain) separate to form dural venous sinuses

    • dural septa limit excessive movement of brain =
    • falx cerebri: in longitudinal fissure, attached to crista galli
    • falx cerebelli: along vermis of cerebellum
    • tentorium cerebelli: horizontal dural fold over cerebellum and in transverse fissure
  8. arachnoid mater (spider mother)
    • middle layer with weblike extensions
    • separated from dura mater by subdural space
    • subarachnoid space contains CSF and largest blood vessels of brain
    • arachnoid villi protrude into superior sagittal sinus and permit CSF reabsorption
  9. pia mater (=tender mother)
    • innermost meninx
    • delicate vacularized connective tissue that clings tightly to brain
  10. cerebrospinal fluid (CSF)
    • composition = watery solution formed from blood plasma (less protein and different ion concentrations than plasma); constant volume
    • functions = gives buoyancy to CNS structures (reduces weight by 97%); protects CNS from blows and other trauma; nourishes brain and carries chemical signals
  11. formation, location, and circulation of CSF - fyi
    • 1) the choroid plexus of each ventricle produces CSF
    • 2) CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures
    • 3) CSF flows through the subarachnoid space
    • 4) CSF is absorbed into the dural venous sinuses via the arachnoid villi
  12. choroid plexuses
    • hang from roof of each ventricle; produce CSF at constant rate; keep in motion (clusters of capillaries enclosed by pia mater and layer of ependymal cells)
    • ependymal cells use ion pumps to control composition of CSF and help cleanse CSF by removing wastes
    • normal volume ~ 150ml; replaced every 8 hrs
  13. hydrocephalus
    • obstruction blocks CSF circulation or drainage
    • unfused skull bones of newborn allow enlargement of head
    • brain damage in adult due to rigid adult skull
    • treated by draining with ventricular shunt to abdominal cavity
  14. blood brain barrier
    • helps maintain stable environment for brain
    • separates neurons from some bloodbourne substances
    • composition: continuous endothelium of capillary walls; thick basal lamina around capillaries; feet of astrocytes (provide signal to endothelium for formation of tight junctions)
  15. blood brain barrier: functions
    selective barrier = allows nutrients to move by facilitated diffusion; denies metabolic wastes, proteins, toxins, most drugs, small nonessential amino acids, K+ entry; allows any fat-soluble substances to pass, including alcohol, nicotine, and anesthetics

    absent in some areas, ex: vomiting center and hypothalamus, where necessary to monitor chemical composition of blood
  16. spinal cord: gross anatomy and protection
    • location: begins at the foramen magnum; ends at L1 or L2 vertebra
    • Functions: provides two-way communication to and from brain; contains spinal reflex centers

    • bone, meninges, and CSF
    • epidural space - cushion of fat and network of veins in space between vertebrae and spinal dura mater
    • CSF in subarachnoid space
    • dural and arachnoid membranes extend to sacrum, beyond end of cord at L1 or L2 (site of lumbar punction or tap)
    • terminates in conus medullaris
    • filum terminale extends to coccyx (anchors spinal cord; fibrous extension of conus covered w/pia mater)
    • denticulate ligaments - extensions of pia mater that secure cord to dura mater
  17. spinal cord
    • spinal nerves (part of PNS) - 31 pairs
    • cervical and lumbosacral enlargements - nerves serving upper and lower limbs emerge here
    • cauda equina - collection of nerve roots at inferior end of vertebral canal
  18. gray matter of spinal cord
    • dorsal horns - interneurons that receive somatic and visceral sensory input
    • ventral horns - somatic motor neurons; axons exit cord via ventral roots; some interneurons
    • lateral horns (only in thoracic and superior lumbar regions) - sympathetic neurons
    • dorsal roots - sensory input to cord
    • dorsal root (spinal) ganglia - cell bodies of sensory neurons
  19. zones of spinal gray matter
    • per relative involvement in innervating somatic and visceral regions of body: 
    • somatic sensory (SS); visceral sensory (VS); visceral autonomic motor (VM); somatic motor (SM)
  20. neuronal pathway generalizations
    • major spinal tracts part of multineuron pathways
    • decussation - pathways cross to other side
    • relay - consist of 2 or 3 neurons
    • somatotopy - precise spatial relationship
    • symmetry - pathways paired symmetrically
  21. white matter of spinal cord
    • myelinated and nonmyelinated nerve fibers allow communication between parts of spinal cord, and spinal cord and brain
    • divided into 3 white columns (funiculi) on each side: dorsal; lateral; ventral
    • each spinal tract composed of axons with similar destinations and functions

    • run in 3 directions:
    • -ascending (sensory) = up to higher centers
    • -descending (motor) = from brain to cord or below
    • -transverse (commissural) = from one side to other