Nervous System
Neuron Structure
Schwann cell - type of neuroglia(only found in PNS - Peripheral Nervous System)
axon - connects cell body to axon terminals(with synaptic vesicles inside); carries impulses away from cell body to axon terminals
cell body - has typical cell structures
dendrites - recieving portion(impulses from other neurons) are seen as projections off of cell body
Functional Classification of Neurons
motor(efferent) - outward, away; exciting; ventral, comes out front of spinal cord
interneuron - between sensory & motor neurons; totally enclosed in CNS; routes impulses where they need to go
sensory(afferent) - approaching, entering; goes into back of spinal cord(dorsal)
Meninges
Spinal Cord: meninges are in the same order except there is an epidural space between the bone & Dura Mater with blood vessels running through it(where epidurals are administered)
transverse & sagittal sinus that are flattened blood vessels
innermost layer of meninges is Pia Mater; covers brain like shrink wrap in all sulcus & sulci; contains blood capillaries known as choroid plexus that make cerebrospinal fluid that circulates above the Pia Mater; closest to brain
Arachnoid Mater - 2nd, mid layer; web-like, thin like a spider web, beneath is subarachnoid space with CSF circulating
outside part of meninges is called Dura Mater(outermost layer of meninges under subdural space); closest to skull
looks like a sac that covers brain & ic connected to bone & christa galli
meningitis - inflamation of meninges
meninges - protective covering for brain and spinal cord
Spinal Cord
ganglion - clusters of cell bodies(neurons) forms swollen area on dorsal in PNS vs. nuclei - clusters of cell bodies in CNS
nerves - only in PNS, not in brain or spinal cord vs. tracts - only in CNS
2 functions: spinal reflexes; conduct ascending(sensory) -posterior entry is also sensory; descending tracts(motor) - anterior exit is also motor
from foramen magnum to vertebral foramen
Ventricles & Location of Cerebro Spinal Fluid
location: ventricles, central canal(SC), & subarachnoid space
4 ventricles(fluid-filled sacs with CSF) in brain
Reflex Arc
ex: step on a tac, lifts foot immediately
ex: feel something burning, pulls hand away asap
example: hitting the patellar ligament on knee; simplest of all reflexes, same thing happens everytime, same action that cannot be controlled
direct route from sensory nueron to effectors(always travels the same path); rapid, predictable, involuntary response
Cerebrospinal Fluid
hydrocephaly - "water on the brain"; fontanel membrane has not ossified * so it keeps stretching to fit the liquid and head is very large; fluid must be removed by channeling the fluid out and into a tube in the neck
spinal tap/lumbar puncture - between L3 and L4 vertebrae(below spinal cord); goes into subarachnoid space and examines fluid for infection
secretes 500 ml; only 140 ml present in a day, rest of it goes to sinuses
functions: maintain stable ionic concentrations for CNS; protective cushion
clear, viscous(thick) fluid secreted by choroid plexus into subarachnoid space
5 Types of Neuroglia
5. Schwann - PNS; only cell of Perioheral Nervous System
4. Ependymal - CNS; in fluid-filled cavities of brain are ventricles, in spinal cord is central canal; controls composition of this fluid & circulate the cerebrospinal fluid
3. Astrocytes - CNS; star-shaped, large cells with processes that come in contact with blood capillaries & neuron; handle exchange/transport of substances between blood & neuron
2. Oligodendrocytes - CNS; form myelin in CNS; wherever they are, there is also white matter; without them, there is gray matter in CNS
1. Microglial - CNS; phagocytize(eat) cell bacteria & cell debris; numbers of these will increase when infection arises
Nerve Structure
wrapping around the entire structure is the epineurium
surrounding the perineuium is many fasicles
wrapping around endoneurium is the perineuium
connected to axon is the endoneurium
nerve cell connected to nerve by axon
2 Divisions
Peripheral Nervous System (PNS)
motor division - somatic and autonomic nervous systems
sensory division - input of receptors
spinal nerves
12 pairs of cranial nerves
all other nerves
Central Nervous System (CNS)
spinal cord
brain
Nervous Tissue
located in spinal cord, brain, and nerves (these are made up of nervous tissue)
neuroglia - netted support tissue for neuron
neuron - entire (single) cell
Myelin Formation
node of Ranvier (ron-vee-ay) - important when transmitting & conducting impulses along the axon
all Schwann cells together form myelin
myelinated axons - white matter unmyelinated axons - grey matter
made up of phospholipids(fat) - protein and cholesterol
5 Characteristics of Neurons
Also study:
12 Cranial Nerves
nerve impulse physiology
nerve impulse/action potential
events leading to the release of a neurotransmitter
comparison of somatic & autonomic nervous systems
special senses
conductivity - transmits impulses from one nerve to another
excitable - sensitive to changes in environment and pH is relevant(acidosis depresses, alkalosis excites)
high metabolic rate - chemical reations are happening very quickly
amniotic - do not divide; won't be replaced
extreme longevity - lives a long time(your life span)
