Week 1 CNS Organization: Objectives 1-2 Flashcards
Anatomical Organization of the Nervous System (3 pts)
CNS: brain and spinal cord
PNS: Cranial nerves and spinal nerves
ANS: Sympathetic and Parasympathetic
What structure does the nervous system directly arise out of?
the neural tube
the brain possess how many cranial nerves, and how many parasympathetic fibers?
12 cranial nerves, 4 of which are parasympathetic (III, VII, IX, X)
General functional categories of the brain
Sensory, motor, cognitive
Spinal Cord, 3 small details
- spinal cord first structure encountered by most incoming sensroy information except in cranial nerves
- spinal cord is the last relay station for most motor information except ANS motor fibers
- Spinal cord is the site of coordination of most reflex arcs
Afferent/Efferent pathways
PNS
Afferent (sensory) pathways
Efferent (motor) pathways
ANS (overview)
Subdivision of PNS
entirely motor
innervates smooth muscle and glands (viscera)
ANS (subdivisions)
Sympathetic: Fight or flight
Also called thoracolumbar
Parasympathetic: Feed and breed
also called carniosacral
Parasympathetic system
feed or breed
Also called craniosacral
Cell body is called (something weird) _____
trophic unit
perikaryon
Dendrites
receptive unit
Axon
conductive unit
Dendrites…..definition and description
branches off cell body, carries information to the cell body
has several to many dendrites per neuron
relatively short, especially compared to the axon
often branched
have receptors for neurotransmitters
conduct local potentials
Axons….D & D
part of neuron that carries signal relatively long single, one per neuron conducts action potential release neurotransmitters
ENDS with telodendria
have “Collateral branches”
has mitochondria, neurofilaments and neurotubules
telodendria
give off endings called terminal boutons
terminal boutons contain synaptic vesicles filled with neurotransmitters
Axoplasm vs Axolemma
axolemma = axon membrane axoplasma = cystoplam of an axon
Axon is covered by a
neurolemma
neurolemma is made of
schwann cells
the neurolemma is often
myelinated
TRUE/FALSE all Schwann cells indicated axon is myelinated
false
Nucleus/Ganglion/Nerve/Tract/Commissure/White matter/Gray matter
Nucleus = aggregation of dendrites and nerve cell bodies in CNS
Ganglion = aggregation of dendrites and nerve cell bodies in the PNS
Nerve: bundle of fibers (axons) in the PNS
Tract: bundle of fibers (axons) in the CNS
Commissure = tract in the CNS that crosses from one side to the other
White matter = areas of myelinated axons
Gray matter = unmyelinated axons, cell bodies, dendrites
PNS system includes
12 cranial nerves
31 spinal nerves
Sensory receptors in the skin, wall of gut tube, tendons in skeletal muscles
motor end plates between motor neurons and skeletal muscle fibers
Spinal nerve branches
spinal nerves divide into two major branches (rami)
each spinal nerve in the thoracolumbar region, before branching into primary rami, gives off
two small branches:
white ramus communicans (carries myelinated preganglionic fibers)
gray ramus (carries unmyelinated postganglionic fibers back to spinal nerve)
Paravertebral ganglia (3 things))
linked together in long chain on either side of the vertebral column
site of cell bodies of postganglionic sympathetic nerves
site of synapses between preganglionic myelinated sympathetic neurons and non myelinated sympathetic neurons
Splanchnic nerve
nerve supplying viscera
Preverterbral ganglion
typically anterior to abdominal aorta
site of synapses between preganglionic myelinated sympathetic neurons and postganglionic non-myelinated neurons
Reflex arc
path that leaves from and returns to the central nervous syste,. consists minimally of sensory pathway and a motor pathway
somatic afferent pathways carry sensation from non-visceral structure such as the skin and skeletal muscle
Somatic afferent pathways carry sensation from
non-visceral structures such as the skin and skeletal muscle
Splanchnic afferent pathways carry sensations from
viscera
Efferent (motor) pathways: Somatic and Visceral
Somatic efferent pathways carry motor signals to skeletal muscles
Visceral efferent pathways carry motor signal to smooth or cardiac muscles (also called visceral motor pathways)
Somatic efferent pathways carry
motor signals to skeletal muscles
Visceral motor pathways carry
motor signal to smooth or cardiac muscles
Thoracolumbar
Fight or flight sympathetic
Craniosacral
Feed and breed, parasympathetic
Somatic Afferent Pathways
Visceral Afferent Pathways
Somatic Efferent Pathways
Visceral Efferent Pathways
Somatic Afferent (sensory, to the brain) Pathways: carry sensory information from non-visceral regions like skin and skeletal muscle to the brain
Visceral Afferent (sensory, to the brain) Pathways carry sensations from viscera to the brain
Somatic Efferent (motor, to target region) Pathways: carry motor signals to skeletal muscles
Visceral Efferent pathways (Visceral motor pathways): carry motor signals to smooth or cardiac muscles
Association Neuron
interneuron
Most reflex arc consist of a afferent and efferent neuron with an interneuron in the CNS to modulate their interactions, some don’t.
Components of a Synapse
Presynaptic membrane (associatied with synaptic vesicles filled with neurotransmitters)
synaptic cleft
postsynaptic membrane (associated with receptors for neurotransmitters)
Monosynaptic pathway
Pathways consisting only of afferent neurons and efferent neurons. Each pathway has only one synapse
Polysynaptic pathways
Pathways that include interneurons as well as afferent and efferent neurons. Each pathway has multiple synapses
Secondary messenger system
Transmitter– >receptor protein –> G protein –> G protein opens channel, activates one or more intracellular enzymes (with corresponding chemical reactions), activates gene transcription (proteins and structural changes), activates enzyme that converts ATP to cAMP or GTP to cGMP
Physiological States of a Neuron: Resting, Excited, Inhibited
Resting = -65 mV Excited = -45 mV Inhibited = -70 mV (due to influx of chloride or efflux of potassium)
Extracellular concentrations of N, K and Cl
Na = 142 mEg/L K = 4.5 MEg/L Cl = 107 mEq/L
Intracellular concentrations of Na, K, Cl
Na = 12 mEq/L K = 120 mEq/L Cl = 8 mEq/L
Excitatory Postsynaptic Potentials (2)
Simultaneous firing of a few synapses will not summate to produce an action potential on a postsynaptic neuron
superimposed action potential can be caused by the simultaneous firing of many synapses on the postsynaptic neuron
8-4 synapses firing at once will produce
not enough potential to cause an action potential
Somatosensory Axis
refers to the sequence of events leading to the firing of a signal from the peripheral to the higher brain centers
Somatosensory Axis Components
Peripheral receptors —> Afferent neurons —> spinal cord or brainstem —> Reticular substance (medulla, pons, mesencephalon) —> cerebellum —> thalamus —> somesthetic areas of cerebral cortex
Somatosensory Axis: Afferent Neurons
Arranged in a series of three
- Primary Afferent synapses in the posterior horn of the spinal cord or sensory nuclei
- Secondary Afferent Synapses in the thalamus
- Tertiary Afferent synapses in the somesthetic areas of cerebral cortex
Skeletal Motor Nerve Axis
Skeletal motor nerve Axis refers to the sequence of structures involved in the transmission of an action potential from the higher functions of the brain to the skeletal muscle
Skeletal motor nerve axis: origin of action potential
Motor cortex of cerebrum
Efferent pathways of the Skeletal Motor Nerve Axis + “effectors”
upper motor neurons extending from cortical areas to the anterior horns of the spinal cord
alpha motor neurons (lower motor neurons) extending to the skeletal muscles
effector = skeletal muscles
smooth muscle and glands are taken care of by ANS, and have a different pattern.
Skeletal motor nerve axis: processing areas of the skeletal motor nerve axis
- Basal ganglia
a. putamen
b. Globus pallidus
c. Subthalamic nuclei
Thalamus in the diencephalon
Spinal cord reflexes
