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The Nervous System Jessica Dorantes Period 1, ., ., ., . - Coggle Diagram
The Nervous System
Jessica Dorantes Period 1
CNS
Includes: Brain & Spinal Cord
Integration & Control center
Interprets sensory input & dictates motor output
PNS
Sensory (Afferent) Division:
carries messages to CNS.
Somatic Sensory Fibers
: carry impulses from
skin, skeletal muscles, and joints to CNS.
Visceral Sensory Fibers
: carry impulses
from visceral organs to CNS
Motor (Efferent) Division:
carries messages away from CNS
Somatic Nervous System (voluntary):
Somatic Motor Neuron fibers carry impulses
from CNS to skeletal muscle.
Efferent pathway:
single thick, myelinated group that extends its axon from spinal/cranial nerves to skeletal muscle.
all somatic motor fibers release ACh + their effect is stimulatory.
Autonomic Nervous System (involuntary):
Visceral Motor Neuron fibers carry impulses to
smooth + cardiac muscle and glands.
Parasympathetic Division
"rest n digest"
general maintenance
Fibers originate in brain + sacral regions
long preganglionic, short postganglionic fibers!
(ganglia in effector organs)
food digestion
Sympathetic Division
"fight or flight"
increase heart rate
glucose release
blood vessels constrict
Fibers originate in thoraic + lumbar regions
Short preganglionic, long postganglionic fibers!
(ganglia near spinal cord)
Efferent pathway:
2-neuron chain
Postganglionic "neuron" slightlymyelinated, extend to ganglion
Preganglionic neuron: outside CNS, synapses with autonomic ganglion & extends to effector organ
preganglionic fibers release ACH, postganglionic release ACh + NE... their effect is stimulatory and inhibitory.
Sympathetic + Parasympathic interaction =
DUAL INNERVATION
Visceral Reflexes
Visceral Sensory Neurons
send into abt chem. or temp. changes,
stetching, or irriation of viscera
Receptors: free nerve endings scattered in viscera
Cell bodies located @ dorsal and ventral
root ganglia or cranial nerves
Have same arc as
Somatic Reflex Arc!!
3 Main Differences
VR have 2 consecutive motor neurons.
Afferent fibers are vesceral sensory neurons.
Effectors: smooth & cardiac muscle + glands.
Neurotransmitters
ACh
(cholinergic fibers @ all ANS preganglionic and parasympathetic postganglionic axons)
NE
(by andrenergic fibres @ almost all sympathetic postgsnglionic axons, except at swear glands)
Effects of ACh & NE
2 types of Cholinergic receptors
Nicotinic (ACh mimics effect of nicotine)
Muscarinic (ACh mimics effects of mushroom poison)
2 classes of Adrenergic receptors
Alpha (responds to NE)
Beta (responds to Epinephrine)
Includes: Nerves
Cranial Nerves
: carry impulses
to and from the brain!
I-XII
I
- Olfatory
II
- Optic
III
- Oculumotor
IV
- Trochlear
V
- Trigemial
VI
- Abducens
VII
- Facial
VIII
- Vestibulocholear
IX
- Glossopharyngeal
X
- Vagus
XI
- Accessory
XII
- Hypoglossal
Spinal Nerves
:
carry impulses to
and from the spinal cord!
Cervical nerves: 8 pairs (C1-C8)
Thoraic nerves: 12 pairs (T1-T12)
Lumbar nerves: 5 pairs (L1-L5)
Sacral nerves: 5 pairs (S1-S5)
Tiny Coccygeal: 1 pair (C0)
CT Coverings
Endoneurium
loose CT around axons.
Perineurium
tough CT, bundles fibers into fascicles.
Epineurim
:
tough fibrous sheath around all
fascicles to form nerve.
Sensory Receptors
Classifying Receptors
By Type
Mechanoreceptors
: respond to touch, pressure, vibration, stretch.
Thermoreceptors
: changes in temp.
Photoreceptors
: respond to light energy.
Chemoreceptors
: respond to chemicals.
Nocireceptors
: sensitive to pain-causing stimuli.
By Location
exteroreceptors
: respond to stimuli outside of body.
propioreceptors
: respond to stretch in skeletal muscles, tendons, joints, ligaments,CT around bone & skeletal muscle.
interoreceptors/visceroreceptors
: respond to stimuli at internal viscera & blood vessels (chem. + temp. changes, tissue stretch).
Sensory Processing
Somatosensory System
Level 1
Receptor level: sensory receptors
Level 2
Circuit level: processing in ascending pathways
Level 3
Perception level: processing n cortical sensory areas
Pain perception!
Pain Tolerance
Visceral Pain
Referred Pain
Respond to stimuli:
sensation (awareness) &
perception (interpretation)
Motor Endings & Motor Activity
Innvervation of
Skeletal Muscle
At neuromuskular junction, by ACh.
Innvervation of Smooth
& Cardiac Muscle and Glands
Autonomic & visceral effectors,
by ACh and NE at Varicosities.
Cells
Neuroglia
(glial cells):
wrap around delicate neurons
Of the CNS
Astrocytes
: branched cells that cling on to &
support neurons, play role in info. processing in brain.
Microgial Cells:
small & thorny, monitor neurons, defensive cells!
Ependymal Cells:
line cavities of CNS and form
layer between CSF and tissue fluid that bathes other cells.
Oligodendrocytes
: wrap around nerve fibers
and form myelin sheath to protect them.
Of the PNS
Satellite Cells
: surround neuron cell bodies
Schwann Cells
(neurolemmocytes): surround all fibers, form myelin sheaths, vital for regeneration of damaged fibers.
Neurons
(nerve cells):
transmit electrical signals &
are amtiotic, excitable, & long.
Classification
Structural
Multipolar
: +3 processes (1 axon + dendrites)
Bipolar
: 2 processes (1 axon + 1 dendrite)
Unipolar
: 1 T-like process (2 axons)
Functional
Sensory
: from sensory receptor to CNS,
located in ganglia of PNS.
Motor
: carry impulses from CNS to effectors,
located in CNS.
Interneurons
: in between motor & sensory,
signal through CNS pathways.
Myelination
:
protect and make axon
carry impulses faster.
In PNS
Formed by Schwann Cells:
wrap "jelly roll "around neuron
In CNS
Formed by Oligondendrocytes:
wrap around 60 axons at once, form myelin gap
Processes
Dendrites
: info receiver,
sends it into cell body
Axons
: info conductor,
sends info from or to cell body
Axon terminal:
releases
neurotransmitters into other cells
Membrane Potential
Generated by differences in
charge & plasma membrane permeability.
Types of Ion Channels
Chemically gated
: open in response to
binding neurotransmitter with receptor
Voltage-gated
: open in response to
changes in membrane potential.
Changes produce
2 types of signals!
Graded potential & Action potential.
Action Potential
The Synapse
Presynaptic neuron
:
carries impulse towards synapse
Postsynaptic neuron
:
carries impulses away from synapse.
6 Main Steps!
1)
AP arrives @ aoxon terminal
2)
Ca+ voltage gated channels open,
Ca+ enter axon terminal.
3)
Ca+ entry causes synaptic vesicles to
release neurotransmitters into synaptic cleft.
4)
Neurotransmitters diffuse across synaptic cleft
and bind to receptors on postsynaptic membrane.
6)
Neurotransmitter effects are performed ASAP!
5)
Binding causes ion channels to open (4 main steps).
4 Main Steps
Resting State:
All Na+ & K= ions are closed,
resting state is -70mV.
Depolarization
: Na+ channels open,
gradient goes up to -55mV (threshold) &
feedback causes it to strike up to +30mV.
Repolarization
:
Na+ channels start closing,
K+ ones open & K+ ions leave
the cell... gradient drops.
Hyperpolarization
: all Na+ channels close,
K+ ones are still open so gradient goes below -70mV
Neutrotransmitters
Biogenic Amines
Amino Acids
Peptides
Purines
Gases & Liquids
Endocannabinoids
Neural Integration:
groups of neurons
functioning together
Serial Processing:
input travels along 1 pathway
REFLEXES!!
Pathway is called
Reflex Arc.
1) receptor
site of stimulus action
2) Sensory neuron
carry impulse to CNS
3) Integration Center
interprets sensory input
4) Motor neuron
carries impulses to effector organs
5) Effector
muscle fiber or gland cell that responds
to impulse by contracting or secreting
Parallel Processing:
input travels along +1
pathways but still have
1 stimulus.
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