LECTURE 6 spinal cord Flashcards
function of nervous system
coordinates the activity of muscles, organs, senses, and actions (control)
3 steps of nervous system function
1: receives sensory input
2: integrate all input and determine response
3: send motor output/command
structural divisions of the nervous system
central nervous system (CNS) and peripheral nervous system (PNS)
components of central nervous system
brain and spinal cord
functions of central nervous system
(represents step 2) interprets incoming sensory signals, dictates motor response
components of peripheral nervous system
cranial and spinal nerves, nerve plexuses (enteric system)
function of peripheral nervous system
(represents steps 1 & 3) communication between regions of the body and the central nervous system
how reflex arc works
sometimes the nervous system needs to protect the body by skipping connection of sensory input and motor output through the use of an interneuron, allowing the motor output to occur more quickly
definition of reflex arc
rapid, automatic motor response
where reflex arc usually occurs
spinal cord or brainstem
examples of reflexes
skeletal muscle movement when touching something burning, smooth muscle of stomach moving to induce vomiting if toxin ingested
are reflex arcs voluntary or involuntary?
involuntary
lifespan of neurons
neurons have high longevity, so there is no regeneration/mitosis, which is why they need to be protected
features of neuron
cell body, dendrite, axon, myelin sheath (sometimes)
structure of myelin sheath
surrounds thicker axons, forms insulating layer
functions of myelin sheath
prevents leakage of electrical current, speeds up the impulse conudction
are neurons or neuroglia more common?
neuroglia
what type of cells produce myelin sheath?
neuroglial cells
organization of a nerve
3 layers: endoneurium, perineurium, epineurium; nerves are bundles of axons carrying signals throughout the body (in PNS); CT layers contain blood vessels
endoneurium of nerve
most deep level, surrounds each axon (nerve fiber), myelinated and unmyelinated axons, motor and sensory nerve fibers, loose CT
perineurium of nerve
middle level, bundles axons into fascicles, CT
epineurium of nerve
most superficial level, bundles fascicles into a nerve, fibrous CT
2 types of nerve signals/fibers
sensory (afferent), motor (efferent)
description of sensory nerve signals
picked up by sensory receptors throughout body, carried by nerve fibers of PNS into CNS
description of motor nerve signals
carried away from the CNS by nerve fibers into PNS, innervate muscles and glands, causes these organs to contract or secrete
somatic vs. visceral signals
somatic information coming from outside body cavity, visceral information coming from inside body cavity
somatic sensory signal examples
body senses: touch, pressure, temperature, vibration of body, muscles stretching, balance
visceral sensory signal examples
organ senses: stretch, pain, temperature in organs, eg: nausea, hunger, cramps
somatic motor signal examples
body movement: voluntary contraction of skeletal muscles
visceral motor signal examples
organ movement: contraction of smooth muscle, gland secretion, contraction of cardiac muscle, aka autonomic nervous system (ANS) (involuntary)
two components of autonomic nervous system
sympathetic system, parasympathetic system
special somatic sensory signals
hearing, equilibrium, vision, smell
special visceral sensory signals
taste
location of spinal cord
runs through vertebral canal of the vertebral column
spinal cord protected by
bone, meninges, cerebrospinal fluid
spinal cord made up of
a core of gray matter surrounded by white matter
spinal nerve description
31 pairs of spinal nerves branch off spinal cord through intervertebral foramen
description of meninges of spinal cord
membranes surrounding the spinal cord
3 layers of meninges of spinal cord
dura mater, arachnoid mater, pia mater (all made of CT)
functions of meninges of spinal cord
protect spinal cord, contains cerebrospinal fluid (CSF), protect blood vessels serving spinal cord
description of dura mater of meninges of spinal cord
most superficial, fibrous CT, spinal dural sheath (one layer), does not attach to bone (creates epidural space), merges with epineurium of spinal roots and nerves (more protective, better connection)
description of arachnoid mater of meninges of spinal cord
middle layer, impermeable barrier to contain CSF, raised off pia mater by rootlets, creates subarachnoid space that holds CSF
description of pia mater of meninges of spinal cord
deepest layer, adheres to brain/spinal cord tissue, highly vascular, creates the denticulate ligaments, thin and delicate
functions of denticulate ligaments
create extra protection to spinal cord, attach spinal cord laterally to help anchor within vertebral canal
description of epidural space of meninges of spinal cord
loose CT, fat and veins, nerves; between dura mater and vertebra, not present around brain
description of subdural space of meninges of spinal cord
between dura mater and arachnoid mater, potential space that blood can enter during trauma
description of subarachnoid space of meninges of spinal cord
between arachnoid mater and pia mater, contains CSF, contains large blood vessels, runs to level of S2
regions of spinal cord (5)
cervical, thoracic, lumbar, sacral, coccygeal
enlargements of spinal cord (2)
cervical enlargement (innervates upper limbs), lumbosacral enlargement (innervates lower limbs)
description of conus medullaris of spinal cord
located around L1-L2, tapered end
description of filum terminale of spinal cord
CT and pia mater, attaches to coccyx, anchors spinal cord caudally to form conus medullaris
description of cauda equina of spinal cord
nerve bunch that extends caudally from spinal cord, looks like horse’s tail
description of gray matter of spinal cord
consists of neuron cell bodies, unmyelinated axons, dendrites, and neuroglia; shaped like an “H”/butterfly
components of gray matter
2 posterior horns (sensory information coming in), 2 anterior horns (motor information going out), gray commissure, central canal (contains CSF)
description of posterior horns of gray matter
consists of interneurons that transmit in from outside spinal cord into it, dorsal root contains sensory fibers (somatic and visceral)
description of anterior horns of gray matter
consists of cell bodies of motor neurons that send info out of spinal cord to muscles and glands; ventral root contains motor fibers (somatic and visceral)
description of white matter of spinal cord
surrounds gray matter, composed of myelinated and unmyelinated axons (only cell part present), divided into white columns (funiculi) that create tracts, allow for communication between parts of the spinal cord (commissurally) and between spinal cord and brain
definition of tract (in spinal cord)
bundles of axons traveling to similar destination
tracts in white matter of spinal cord
2 posterior funiculi, 2 anterior funiculi, 2 lateral funiculi
types of nerve fibers in white matter of spinal cord
ascending nerve fibers, descending nerve fibers, commissural nerve fibers
description of ascending nerve fibers of white matter of spinal cord
carry sensory info from sensory neurons of body to brain (touch, pressure, pain, temperature)
description of descending nerve fibers of white matter of spinal cord
carry motor instructions from brain to spinal cord, contraction of muscles and secretion of glands (controlling precise, skilled movement, eg: writing, maintaining balance, create movement)
description of commissural nerve fibers of white matter of spinal cord
cross from one side of spinal cord to the other
