Nerve and development Flashcards
nervous tissue
- ectoderm
- detect and analyze sensory input, coordinate body activities, store and recal experiences
- parts=PNS and CNS
somatotopic organiztion
- different brain areas dedicated to different body parts or different modes of info
- gyri=bumps on outer portion
- sulci=groves on outer cortical portion of brain
- primary motor cortex=precentral gyrus, anterior to central sulcus
- primary sensory cortex=postcentral gyrus posterior to central sulcus
spinal chord
- ascending tracts carry sensory info to brain, located dorsally
- descending tracts send motor information, located ventrally
peripheral nervous system
=all nerves except brain and spinal chord, mixed motor and sensory
afferent sensory nerves enter spinal chord via dorsal roots
efferent motor nerves exit via ventral nerve roots
somatic portion of PNS
- carry consciously percieved info like voluntary mm contraction
- consists of single neuron connections
autonomic/visceral portion of PNS
-unconscious info like proprioception and contraction of involuntary or cardiac muscle, gland secretion
-multiple nerve connections and lots of integration
divided into parasympathetic (nerves origionating in midbrain, cervical, and sacral regions) and sympathetic (thoracic and lumbar region nerves)
nervous tissue cell types
- neurons-excitable
- neuroglial cells-non-excitable but enhance transmission
- support cells (from mesoderm) includes blood vessel cells like endothelium and fibroblasts and microglia (CNS immune cells)
neurons
soma has nucleus, cytoplasm with cytoskeleton, nissal bodies (ribosome rich RER)
dendrites has mitochondria, SER, microtubules and neurofilaments but no golgi
axon has mitochondria and SER but few/no ribosomes and many microtubules
axon terminal
axonal transport
anterograde=from soma to axon terminal
retrograde from terminal to soma
ganglion
PNS-cluster of nerve cell bodies where many synapses occur
nucleus
CNS-cluster of cell bodies where many synapses occur
six steps of synaptic transmission
- vesicle transport 2. vesicle loading 3. depolarization 4. exocytosis 5. binding of neurotransmitter and 6. further depolarization
glia
different cell types that contribute to neurotransmission
-help speed up impulses my forming myelin sheath around axons in CNS
schwann cells
myelinate axons in PNS
1 schwann cell/1-2mm of axon
can swallow axons (10) but not myelinate them-they can communicate w/extracellular space still
oligodendrocytes (CNS)
myelinate CNS neurons
protoplasmic and fiberous astrocytes (CNS)
- send out processes that contact blood vessels and maintain blood flow, scavange ions and maintain homeostasis
- facillitate transport accross BBB
- protoplasmic in grey matter, fiberous in white
microglia (CNS)
-immune phagocytic cells, extend and retract processes and attracted to damaged neurons
ependymal cells (CNS)
- form simple epithelium
- line surface of brain beneath pia matter, inner surface of ventricles, and inner surface of central canal of spinal chord
- synthesize, secrete, and exchange CSF
- blood-CSF barrier maintained by tight junctions
PNS connective tissue
all derived from mesoderm
epineurium-dense irregular CT around nerves
perineurium-dense irregular CT around fasicles
endoneurium-loose irregular connective tissue
meninges
dura matter outermost and dense irregular connective tissue,
arachnoid mater dense irregular w/ some elastic fibers
pia mater b/t dense and loose connective tissue
subarachnoid space contains blood vessels that supply and drain brain and spinal chord and is where CSF is outside ventricular system
BBB
- formed by epithelium that lines blood vessels of brain (capillary endothelium)
- many tight junctions to prevent diffusion
- lipid substances can pass and macromolecules can be actively transported across
ventricular system
CSF=liquid cushion, nutrient suport, neurotransmitters, waste material
choroid plexus transports things from capillaries into ventricles to make CSF
CSF flows into subarachnoid spaces where it is returned to venous blood via aracnoid villi, which pierce dura matter
periods of pre-natal development
- pre-embryonic-first 2 weeks
- embryonic-weeks 3-9
- fetal-week 9-birth
fertalization to blastocyst formation
- fertalization occurs in the uterine tube
- receptor mediated process leads to membrane fusion of sperm and egg that generates a totipotent single cell zygote
- the zygote proliferates w/out differentiated until a mass (morula) of cells is formed, morula moves to uterus proper
- morula pumps fluid into its center to form a cavity called blastocyst
- differentiation occurs to form embryoplast cells that form embryo proper
- embryo proper=embryonic stem cells and trophoblasts