Intro to Neuro Flashcards
CNS
brain
spinal cord
white matter - axons and oligodendrocytes
gray matter - soma/cell body and unmyelinated fibers
PNS
cranial and spinal nerves
relays info to and from the CNS
afferent and efferent
contains somatic and autonomic NS
afferent versus efferent
afferent (ascending) –> to the CNS; sensory input
efferent (descending) –> away from the CNS; motor output
somatic NS
motor and sensory pathways regulating voluntary control of skeletal muscle
What neuron is used in somatic NS and what does it release?
alpha motor neuron; releases acetylcholine on effector organs
Autonomic NS
motor and sensory components involved in regulating involuntary control of organs and internal environment
consists of sympathetic and parasympathetic
What motor neurons are used in autonomic NS
two motor neurons: pre-ganglionic and post-ganglionic
Sympathetic
thoracolumbar
Parasympathetic
craniosacral
Afferent
ascending pathway that takes sensory info from PNS to CNS
sensory info always enters through the Doral horn of spinal cord
Ascending tracts
pain and temperature: lateral spinothalamic tract
light touch and pressure: anterior spinothalamic tract
discriminative touch, vibration, and proprioception: posterior white column
Efferent
descending pathway that takes motor info from CNS to PNS
motor info exits through the ventral horn (anterior) of spinal cord
Descending tracts
pyramidal tracts: voluntary movement, fine motor; begins in the pre central gyrus (motor area);
Extrapyramidal tracts: reflexes, postural control, complex movements
Parasympathetic cranial nerves
Oculomotor nerve (III)
Facial nerve (VII)
Glossopharyngeal nerve (IX)
Vagus nerve (X)
Oculomotor nerve (III) function - parasympathetic
narrows pupils and focuses lens
Facial nerve (VII) function - parasympathetic
tear, nasal, and salivary glands
Glossopharyngeal nerve (IX) function - parasympathetic
parotid salivary gland
Vagus nerve (X) function - parasympathetic
cardiac (decreased HR)
pulmonary (bronchoconstriction)
GI: up to proximal 1/2 of colon – increases motility
Sacral nerves & function - parasympathetic
S2-S4
bladder, distal colon, genitals
The sympathetic system is directed primarily by
the limbic system and hypothalamus
T1-4/5 ascend up chain ganglia (sympathetic) to innervate eye for
dilation
decrease salivation
Sympathetic system function
increased HR
increased contractility
increased cardiac output
increased BP
direct effect on adrenal gland to release episodes and NE into system –> widespread vasoconstriction –> increase BP
Excitation in neurotransmission
opening Na+ channels
closing K+ channels
leads to depolarization –> postsynaptic neuron stimulated
Inhibition in neurotransmission
closing Na+
opening K+
leads to hyperpolarization –> postsynaptic neuron not stimulated
Excitatory NT function
stimulate action potential of the post synaptic neuron
increase permeability of post-synaptic membrane allowing Na+ ions to diffuse into postsynaptic neuron –> depolarization and generation of action potential
Excitatory NT and neuropeptides
Acetylcholine
Glutamate
Nitric oxide
Substance P (associated w pain pathway)
Acetylcholine
mostly excitatory (few parasympathetic inhibition functions)
active in skeletal muscle contractions
part of autonomic nervous system synapses
Glutamate
most common excitatory transmitter in CNS
Inhibitory NT function
NT binds to receptor causing opening of K+ or Cl- channels –> membrane potential decreases (hyper polarization of membrane) –> neuron is now insensitive to stimulus and depolarization
Inhibitory NT and neuropeptides
dopamine
GABA
serotonin
glycine
Dopamine
originates mostly in substantial nigra; generally inhibitory
GABA
major inhibitory in the brain, some in spinal cord
mostly local effects
Glycine
mostly local effects of inhibition in spinal cord
Acetylcholine – excitatory plus inhibitory
peripheral parasympathetic inhibition of heart via vagus nerve
Norepinephrine —–
excitatory plus inhibitory
Neuroglial cells
most abundant cells of nervous system
surround neuron cell bodies
provide metabolic and structural support
maintain environment that allows neurons to function
form myelin
regulate clearance of NT from synaptic space
Types of neuroglial cells
astrocytes
oligodendroglia
ependymal cells
microglia
Astrocytes
help regulate movement of metabolites and waste into/out of neurons (control blood flow and regulate permeability of blood/brain barrier)
control ionic concentration extracellularly (CSF)
maintain microenvironment in CNS
highest amount of all types of neuroglial cells
Oligodendroglia
provide myelination for multiple axons in CNS
Ependymal cells
Cell lining in brain ventricles
Form blood-CSF barrier and blood-retina barrier
Microglia
brain macrophages
immune support
phagocytosis
Spinothalamic tract decussation
at level of the spinal column
Dorsal column decussation
decussates at level of lower medulla
Corticospinal tracts
pyramidal tract
efferent tract from cortex to limbs and trunk
comprised of lateral and anterior tract
Lateral tract (corticospinal)
decussates in medulla
85-90% of fibers
controls digits and limbs
Anterior tract (corticospinal)
remains ipsilateral until it reaches its intended spinal level and decussates at that level in the spinal cord
controls trunk, neck, shoulders
Corticobulbar tract
efferent pathway from cortex to medulla
control CN V, VII, IX, X, XI, XII
indirect control of CN III, IV, VI through MLF
has upper motor neuron that generally synapses bilaterally
Corticobulbar tract exception to bilateral innervation
VII nuclei (facial) is split into upper and lower
upper - bilateral innervation
lower - only contralateral innervation
STROKE = only lower bc contralateral innervation
BELL’S PALSY = upper and lower
Hyperreflexic could indicate
upper motor neuron lesion
Hyporeflexic coud indicate
lower motor neuron lesion
Baroreflex
stretch receptors in carotid sinus and aorta
respond to smooth muscle fiber changes
increased pressure = increased AP
signal to medulla to cardiac control center
Baroreflex function
decrease sympathetic discharge (decrease cardiac contractility, decrease HR, increase arteriolar and venous dilation)
increase parasympathetic discharge (decrease HR)
net effect = decreased BP
Dysfunction of baroreflex
can cause postural hypotension
Where do pyramidal tracts begin
pre central gyrus (motor area)
Pyramidal tracts
Corticospinal (cortex to spine)
Corticobulbar
Corticospinal tract
movements of limbs and trunk
Corticobulbar tract
movement of non-oculomotor cranial nerves
