Chapter 1 - General Plan of the Nervous System Flashcards
Nervous system divided based on anatomy/structure
- central nervous system (CNS) – brain and spinal cord
- peripheral nervous system (PNS) – cranial and spinal nerves
Nervous system divided based on physiology/function
- somatic nervous system – controls body structures (voluntary)
- autonomic nervous system – controls smooth muscles, glands, blood vessels (involuntary)
Spinal cord
connects brain and PNS
Somatic nervous system
controls voluntary muscles and transmits sensory information to the CNS
Autonomic nervous system
- controls involuntary body functions
- made up of sympathetic nervous system and parasympathetic nervous system (which are constantly competing to control arousal state)
Sympathetic nervous system
arouses body to expend energy
Parasympathetic nervous system
calms body to conserve and maintain energy
Ventral, anterior
on the front (belly) side
Dorsal, posterior
on the back side
Superior
on the top (skull) side
Inferior
on the lower side
Caudal
in the lowermost position (at the tail end)
Rostral
on the forward side (at the nose end)
Medial
close to or toward the middle
Median
in the middle, the midplane (midsagittal)
Lateral
toward the side (away from the middle)
Sagittal plane
- vertical line which divides the brain into a left section and a right section
- mid-sagittal is when brain is split right down the middle
- does not show bilateral symmetry
Coronal plane
- vertical line which divides the brain into a front (anterior) section and a back (posterior) section
- shows bilateral symmetry
Transverse/horizontal plane
- horizontal line which divides the body into an upper (superior) section and a lower (inferior) section
- horizontal plane is used for brain and transverse plane is used for spinal cord
- shows bilateral symmetry
Central Nervous System (CNS)
- comprised of the brain (encephalon) and spinal cord
- brain has a tiered structure – 3 main subdivisions of the brain
- – cerebrum (forebrain) – most rostral
- – cerebellum
- – brain stem – most caudal
- each subdivision is further divided into discrete regions
Cerebrum
- most phylogenically advanced
- responsible for complex functions (cognition)
- comprised of telencephalon and diencephalon
Telencephalon
- comprised of:
- – cerebral cortex gray matter (neuron cell bodies)
- – subcortical white matter (myelinated axons going to and from cortex) (this includes corpus callosum)
- – commissures
- – basal ganglia (subcortical gray matter)
Diencephalon
- comprised of:
- – thalamus
- – hypothalamus
- – epithalamus
- – subthalamus
Cerebellum
- collections of gray matter and white matter tracts (2 lateral lobes joined by the vermis)
- comprised of cerebellar cortex and deep cerebellar nuclei
Brain stem
- collections of gray matter and white matter tracts
- comprised of midbrain (mesencephalon), pons, and medulla oblongata
Ventricles
hollow spaces within the brain and spinal cord filled by cerebral spinal fluid (CSF)
Spinal cord - neuronal somata (cell bodies) and tracts
- neuron cell bodies lie in the center of the spinal cord in an area called the Central Gray (gray matter)
- connections (or pathways) between neurons in CNS exist as fiber bundles or tracts (white matter)
- – aggregates of tracts in the spinal cord are called columns
Gray matter
contains neuronal and glial cell bodies, axons, dendrites, and synapses
White matter
contains myelinated axons and associated glial cells
Tracts and commissures in brain and spinal cord
- connections/pathways between neurons in CNS exist as fiber bundles or tracts called fasciculi
- – aggregates of fasciculi in the spinal cord are called columns
- – vertical pathways may remain on the same side (ipsilateral) or cross (decussate) to the opposite side (contralateral)
Ipsilateral
on the same side
Contralateral
on the opposite side
Bilateral
on both sides
Symmetry of the Nervous System
- nervous system is bilaterally symmetrical
- – organized into left and right hemispheres
- – some functions are unilaterally strong (e.g. language in the left hemisphere)
Functional maps exist within the brain
- at many levels, the brain maps the outside world
- – e.g. sensory and motor homunculous (sensory and motor neural representation of the body surface)
- – topographically faithful map
- —– body relationships preserved
- —– size of part reflects disproportional sensitivity
Peripheral Nervous System (PNS)
- spinal nerves, cranial nerves, and ganglia (collections of cell bodies) outside of the CNS
- PNS nerve fibers conduct information to (afferent) or from (efferent) the CNS
- peripheral nerves connect to spinal cord by dorsal (sensory) and ventral (motor) roots
Spinal nerves branch off from the spinal cord
each nerve is split into dorsal and ventral nerve roots
Dorsal roots
sensory
Ventral roots
motor
D.S.A.
dorsal sensory afferent
V.M.E.
ventral motor efferent
Afferent
to
Efferent
from
Longitudinal axes of CNS
- longitudinal axis of brain stem and spinal cord
- longitudinal axis of forebrain
Ventral side of brain
underside of brain
Dorsal side of brain
overside of brain
Ventral side of spinal cord
side towards nose
Dorsal side of spinal cord
side towards back of head
Rostral end of spinal cord
end towards brainstem
Caudal end of spinal cord
end towards bottom of the spinal cord
ependymal cells
- produce and absorb CSF
