Module 4 - Nervous System Flashcards
central nervous system
- brain & spinal cord
- processing and control center of nervous system
brain
- found in cranial cavity
- four parts: brainstem, cerebellum, cerebrum, diencephalon
spinal cord
- continuous with medulla oblongata and descends into vertebral canal
- consists of 31 segments with 31 pairs of spinal nerves
peripheral nervous system
- cranial & spinal nerves, special sense organs
- somatic, autonomic, and enteric nervous systems
somatic nervous system
- voluntary nervous system
- somatic afferent (sensory) nerve fibers transmit sensory info from body surface receptors to CNS
- somatic efferent (motor) nerve fibers relay impulses from CNS to skeletal muscles
autonomic nervous system
- involuntary nervous system
- autonomic afferent (sensory) nerve fibers transmit sensory info from receptors in visceral organs to CNS
- autonomic efferent (motor) nerve fibers relay impulses from CNS to smooth muscle, cardiac muscle, and glands
enteric nervous system
- nerves extending throughout GI tract
- enteric afferent (sensory) nerves transmit info such as chemical change from GI tract to CNS
- enteric efferent (motor) nerve fibers relay impulses to smooth muscle and GI tract glands
peristalsis
waves of smooth muscle contraction, propelling food through GI tract
sympathetic division
stimulatory role
parasympathetic division
inhibitory role
enteric nervous system
- involuntary
- enteric plexus of nerves extending throughout GI tract
- enteric afferent (sensory) nerve fibers transmit sensory info from GI to CNS
- enteric efferent (motor) nerve fibers relay impulses to smooth muscle and glands of GI tract; responsible for glandular secretions
peristalsis
waves of smooth muscle contraction, propelling food through GI tract
neurons
basic components of nervous system
sensory neurons
transmit stimuli from body to CNS
interneurons
remain within CNS, process and store information
motor neurons
transmit stimuli from CNS to the body
unipolar neuron
only has one nerve process extending from the cell body (found in ganglia)
bipolar neuron
has two nerve processes extending from the cell body (found in retina, inner ear)
multipolar neuron
has multiple nerve processes and dendrites extending from a singular cell body (majority of CNS)
what are the CNS neuroglia?
astrocytes, oligodendrocytes, microglial cells, & ependymal cells
astrocytes
- largest & most abundant
- connections with capillaries, neurons, synaptic endings, pia matter
- function: anchor to neuron, blood-brain barrier, recycle excess ions, secrete chemicals for neuron growth & migration, repair damaged tissue
protoplasmic astrocytes
short, branching cytoplasmic processes in grey matter
fibrous astrocytes
longer, unbranched cytoplasmic processes in white matter
oligodendrocyte
- smaller with fewer cytoplasmic processes
- wrap tightly around axons, covering with layers of myelin sheath for insulation
- form segments of sheath around several axons at once, thought to contribute to axonal regrowth
microglial cells
- smallest of CNS neuroglia
- thorn-like processes extending from ovoid bodies
- remove cellular debris, invading microorganisms, and nervous tissue damaged by phagocytosis
ependymal cells
- single rows of cuboidal to columnar epithelial cells
- line ventricles of brain and central canal of spinal cord
- secrete and monitor cerebrospinal fluid
- form semipermeable membrane between CSF and interstitial fluid of CNS
- microvilli & cilia help circulate CSF
what are the PNS neuroglia?
schwann cells & satellite cells
schwann cells
- similar to oligodendrocytes, form myelin sheath around axons
- play role in regeneration of PNS neurons by guiding & stimulating regrowth
- many myelinate a single axon, gaps called Nodes of Ranvier
satellite cells
- flat cells surrounding neuronal bodies residing within ganglia
- provide structural support & form barrier, regulating exchange of substances
myelin
covering of lipid and protein that surrounds axons & increases with age
nerves
cord-like structure composed of bundles of neuronal axons that transfer sensory information to the CNS and motor information from CNS
anatomy of a nerve
axon –> myelin sheath –> endoneurium –> bundles of nerve fibers –> perineurium –> epineurium
membrane potential
build up of negatively charged ions in membrane, and positively charged outside membrane
ion channels
allow for flow down electrochemical gradient, creating a current
voltage gated ion channel
- open in response to changes in membrane potential
- activation gate closed at rest
ligand gated ion channel
open in response to binding of neurotransmitter/hormone latching to receptor
mechanically gated ion channel
open in response to mechanical forces: stretching, vibration, pressure, etc.
sodium / potassium pump
- Na+ higher outside, K+ higher inside
- pumps 3 Na+ out and 2 K+ in
leakage channel
- open and close randomly
- more K+ than Na+ channels
depolarizaton
- plasma membrane becomes less negatively charged
- reaching threshold of -55mv causes voltage gated channels to open
- sodium rushing in, pushing membrane potential to the positives, action potential then passing through
repolarization
voltage gated potassium channels open, Na+ flows out
hyperpolarization
- no possibility of another stimulus, inactivated Na+ channels
- sodium channels open but only strong stimulus can trigger action potential
- K+ still open, making depolarization harder
saltatory conduction
- occurs in myelinated axons
- myelin sheaths lack voltage gated channels, action potential jumps from node to node
continuous conduction
- occurs in unmyelinated axons
- sodium influx creates local positive charge, depolarizing region of cell
- depolarization of one region triggers depolarization of adjacent region
why does the action potential only propagates towards terminal?
despite current flowing in both directions, voltage gated channels become inactive, pushing current in other direction
what is the speed of propagation determined by?
myelination, axon diameter, temperature
mechanoreceptor
sense mechanical force like touch, vibration, pressure, and stretch
thermoreceptor
sense change in temperature
photoreceptor
sense light
chemoreceptor
chemicals
nociceptor
sensory receptor of painful stimuli
osmoreceptor
sense osmotic pressure
what are the three parts of the brainstem?
medulla oblongata, pons, midbrain
parts of the diencephalon?
thalamus, hypothalamus, epithalamus
thalamus
mood, emotions, movement, visual & auditory info
hypothalamus
sleep/wake cycle, thirst, endocrine system
epithalamus
emotional response to olfaction (smell)
frontal lobe
cognitive thought and memory
temporal lobe
auditory area, Wernicke’s area (speech comprehension), learning and memory, emotions
parietal lobe
body orientation, primary and gustatory cortex (taste)
occipital lobe
visual cortex & interpretation
gyri
folds and bumps of brain
sulci
grooves and indentations of brain
meninges
layers between brain and skull: pia mater, arachnoid mater, dura mater
subarachnoid space
space between pia mater and arachnoid mater, CSF fluid circulated here
sinuses
peristeal and meningeal layers separate to create dural sinuses
why is the blood brain barrier important?
breakdown of the barrier by toxins, inflammation, or trauma is life threatening
