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Nervous System Lydiann Guzman Per.5 - Coggle Diagram
Nervous System Lydiann Guzman Per.5
Major Functions of the Nervous System
Nervous System
master controlling and communicating system of body
3 overlapping functions:
Intergration
processing of interpretation of sensory input
Motor Output
activation of effector organs (muscles and glands) produces a response
Sensory Input
information gathered by sensory receptors about internal and external changes
Classification of Neurons
number of processes
1) Multipolar
3 or more processes (1 axon, others dendrites)
most common and major neuron type in CNS
2) Bipolar
2 processes (1 axon, 1 dendrite)
rare (ex: retina and olfactory mucosae)
3) Umpolar
1 T-like process (2 axons)
also called pseudounipolar
by which direction nerve impulses traveld relative to CNS
1) Sensory
transmits impulses from sensory receptors toward CNS
almost all are unipolar; cell bodies are located in ganglia in PNS
2) Motor
carry impulses from CNS to effectors
Multipolar; cell bodies are located in CNS
3) Interneurons
lie between motor and sensory neurons
entirely withing CNS; 99% of body neurons are interneurons
Action Potential and the Nerve Impulse
an electrical charge that travels along the membrane of a neuron; resting membrane potential - approx 70 mv
potential generated by:
differences in ionic composition (charge)
differences in plasma membrane permeability
changes when:
concentration of ions across membrane change
membrane permeability to ions change
changes produce 2 types of signals:
graded potential
incoming signals operating over short distances
action potential
long distance signals of axons
changes in membrane potential are used as signals to receive, integrate, and send info
depolarization
decreased in membrane potential (moves toward zero and above)
hyperpolarization
increase in membrane potential (away from zero)
action potentials
so not decay over distance as graded potentials do; involves opening of specific voltage-gated channels
brief reversal membrane potential w/ a change in voltage of 100 mv
generating an action potential
2) Depolarization
Na+ channels open
3) Repolarization
Na+ channels are inactivating, and K+ channels open
1) Resting State
all gated Na+ and K+ channels are closed
4) Hyperpolarization
some K+ channels remain open, and Na+ channels reset
all or none:
an AP either happens completely, or does not happen at all
propagation:
allows AP to be transmitted from origin down entire axon length toward terminals
refractory period:
time in which neuron cannot trigger another AP
conduction velocity
continuous conduction
slow conduction that occurs in nonmyelinated axons
saltatory conduction
occurs only in myelinated axons and is about 30x faster
Compare and Contrast the Autonomic Nervous System
both have motor fibers bud differ in:
effectors
SNS
innervates skeletal muscles
ANS
innervates cardiac muscle, smooth muscle, and glands
efferent pathways and ganglia
SNS
cell body in CNS, a single, thick myelinated group A axon extends in spinal or cranial nerves directly to skeletal muscle
ANS
pathway uses a two neuron chain
1) preganglionic neuron
cell body in CNS with thin, lightly myelinated preganglionic axon extending to ganglion
2) postganglionic neuron (outside CNS)
cell body synapses with preganglionic axon in Autonomic ganglion with nonmyelinated postganglionic axon that extends to effectors organ
target organ responses to neurotansmitters
SNS
all motor neurons release acetylcholine
ANS
preganglionic fibers release Ach
postganglionic fibers release norepinephrine or Ach at effectors
Disorders/Diseases
stroke
damage to areas of primary motor cortex; paralyzes muscles controlled by those areas
hypothalamic disturbances
obesity
emotional imbalances
severe body wasting
sleep disturbances
dehydration
meningitis
inflammation of the meninges
epileptic seizure
torrent of electrical discharges by groups of neurons
hydrocephalus
obstruction blocks CSF circulation or drainage, results in increased pressure
concussion
temporary alternation in function
contusion
permanent damage
subdural or subarachnoid hemoorhage
pressure from blood may force brain stem through foramen Magnum, resulting in death
more disorders/diseases
cerebral edema
swelling of brain associated with traumatic head injury
ischemia
tissue deprived of blood supply, leading to death of brain tissue
hemiplegia
paralysis on 1 side of face or sensory and speech deficits may result
transient ischemic attacks (TIAs)
temporary episodes of reversible cerebral ischemia
alzheimer's disease
progressive degenerative disease of brain that result in dementia
memory loss, short attention span, disorientation, eventual language loss, irritability, moodiness, confusion, hallucinations
parkinson's disease
degeneration of dopamine-releasing neurons of substantia nigra
basal nuclei deprived of dopamine become overactive, resulting in tremors at rest
Huntington's disease
fatal hereditary disorder cause by accumulation of proteins huntingtin in brain cells
initial symptoms include wild, jerky, "flapping" movements
spinal cord trauma
localized injury to spinal cord or its roots leads to functional losses
paresthesias
caused by damage to dorsal roots or sensory tracts
paralysis
caused by damage to ventral roots or ventral horn cells
more disorders/diseases
spinal shock
transient period of functional loss caudal to lesion
amyotrophic lateral sclerosis (ALS)
destruction of ventral horn motor neurons and fibers of pyramidal tract
loss ability to speak, swallow, and breathe
cerebral palsy
neuromuscular disability involving poorly controlled or paralyzed voluntary muscles
spasticity, speech difficulties, motor impairments, seizures, deaf, visual impairment
anencephaly
cerebrum and parts of brain stem never develop because neural fold fails to fuse
spinal bifida
incomplete formation of vertebral arches; typically involves lumbosacral region
large cysts, hydrocephalus, paralysis, and bowel and bladder dysfunction
multiple schoerosis (MS)
autoimmune disease that affects primarily young adults
visual disturbances, weakness, loss of muscular control, speech disturbances, incontinence
hypertension (high blood pressure)
heart must work harder, and artery walls are subject to increased wear and tear
raynaud's disease
painful, exaggerated vasoconstriction in fingers and toes (digits turn pale)
Autonomic dysreflexia
blood pressure skyrockets, posing increased risk for stroke
Autonomic neuropathy
damage to Autonomic nerves that is a common complication of diebetes mellitus
Major divisions and subdivisions of the nervous system
Nervous System
master controlling and communicating system of body
central nervous system (CNS)
brain and spinal cord of dorsal body cavity
integration and control center: interprets sensory input and dictates motor output
peripheral nervous system (PNS)
portion of NS outside of CNS
consists mainly of nerves that extend from brain and spinal cord
spinal nerves to and from spinal cord
cranial nerves to and from brain
2 function divisions
sensory (afferent) division
somatic sensory fibers
convey impulses from skin, skeletal muscles, and joints to CNS
visceral sensory fibers
convey impulses from visceral organs to CNS
motor (efferent) division
transmits impulses from CNS to effector organs
somatic nervous system (voluntary)
somatic motor nerve fibers conduct impulses from CNS to skeletal muscle
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autonomic nervous system (involuntary)
consists of visceral motor nerve fibers
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Drugs of Abuse
Ecstasy
neurotransmitters that interfere: serotonin neurotransmitters
mimics serotonin and is taken up by serotonin transporters; transporter becomes confused and starts to transport seotoning out of the cell. Serotonin becomes trapped in synaptic cleft causing to bind over and over again to receptors, overstimulating the cell
affects pathways responsible for mood, sleep, perception, and appetite; indirectly interacts with rewards pathway
Marijuana
neurotransmitters that interfere: inhibitory neurotransmitters and dopamine neurotransmitters
THC mimics anandamide and binds to connbinoid receptors. Inhibition is turned off and dopamine is allowed to quirt into synapse
removing unnecessary short term memories; responsible for slowing down movement, making us feel relaxed and calm
Methamphetamine
neurotransmitters that interfere: dopamine neurotransmitters
meth enters dopamine vesicles forcing the dopamine molecules out. The excess dopamine in cell causes transporters to start pumping dopamine out of cells and into synapse. Excess dopamine gets trapped in synaptic cleft, binding over and over again, overstimulating the cell
works directly on the brains reward pathway; makes you feel intense pleasure and exhilaration
Heroine
neurotransmitters that interfere: inhibitory neurotransmitters and dopamine neurotransmitters
heroine binds to opiate receptors, turning off dopamine inhibition, flooding the synapse
immediate feelings of sedation and wellbeing, relieves pain
Alcohol
neurotransmitters that interfere: GABA inhibitory neurotransmitter and glutamate neurotransmitter
makes GABA receptors more inhibitory after interacting. While also binding to glutamate receptors, preventing glutamate from exciting the cell
affects areas of brain; affects memory formation, decision making, and impulse control
Cocaine
neurotransmitters that interfere: dopamine neurotransmitters
cocaine blocks transporters, leaving dopamine trapped in synaptic cleft. Resulting in dopamine binding again and again to receptors, overstimulating the cell
concentrates reward pathway; active in parts of brain controlling voluntary movements; causing fidgeting and inability to be still
LSD
neurotransmitters that interfere: serotonin transmitters
LSD elicits effect of serotonin by binding to serotonin receptors. LSD interacts with particular receptors in different ways. Sometimes LSD inhibits them and sometimes it may excite them.
complex sensory effects; excites locus coeruleus (LC); responsible for feelings of wakefulness and evoking a startle response to unexpected stimulus
Spinal Nerves
31 pairs of spinal nerves
supply all body parts except head and part of neck
5 pairs
of lumbar nerves
( L1 - L5 )
5 pairs
of sacral nerves
( S1 - S5 )
each spinal nerve is connected to spinal cord via 2 roots:
ventral roots
contain motor (efferent) fibers from ventral horn motor neurons that innervate skeletal muscles
dorsal roots
contain sensory (afferent) fibers from sensory neurons in dorsal root ganglia that conduct impulses from peripheral receptors
12 pairs
of thoracic nerves
( T1 - T12 )
1 pair
of tiny coccygeal nerves
( C0 )
8 pairs
of cervical nerves
( C1 - C8 )
Major Parts and Functions of the Brain
diencephealon
hypothalamus
located below thalamus
forms cap over brain stem and forms inferolateral walls of third ventricle
main visceral control and regulating center that is vital to homestasis
chief homestasis controls:
controls autonomic nervous system
ex: blood pressure, rate and force of heartbeat, digestive tract motility, pupil size
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initiates physical responses to emotions
part of limbic system: perceives pleasure, fear, rage, biological rhythms, and drives (sex drive)
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epithalamus
most dorsal portion of diencephalon
forms roof of third ventricle
contains pineal gland (body); extends from posterior border; secretes melatonin that helps regulate sleep-wake cycle
thalamus
act as relay station for information coming into cortex
sorts, edits, and relats ascending input
acts to mediate sensation, motor activities, cortical arousal, learning, and memory
brain stem
controls automatic behaviors necessary for survival
midbrain
cerebral peduncles
2 ventral bulges that contain pyramidal motor tracts
cerebral aqueduct
channel running through midbrain that connects third and fourth ventricles
corpora quadrigemina
paired dorsal productions
superior colliculi
visual reflex centers
inferior colliculi
auditory relay centers
substantia nigra
functionally linked to basal nuclei
pons
some nuclei play role in reticular formation, and some help maintain normal rhythm of breathing
medulla oblongata
contains choroid plexus: capillary rich membrane that forms cerebral spinal fluid
functions of the medulla oblongata
cardiovascular center
cardiac center adjusts force and rate of heart contraction
vasomotor centers adjusts blood vessel diameter for blood pressure regulation
respiratory centers
generate respiratory rhythm
control rate and depth of breathing (w/pontine centers)
various other centers regulates
hiccuping
swallowing
vomiting
coughing
sneezing
cerebral hemispheres
form superior part of brain and responsible for communication between cerebral areas, between cortex and lower CNS
surface markings
sulci
shallow grooves
several sulci divide each hemisphere into 5 lobes
temporal
occipital
parietal
insula
frontal
major sulci that divide lobes
central sulcus
seperates precentral gyrus of frontal lobe and post central gyrus of parental lobe
parieto-occipital sulcus
seperates occipital and parietal lobes
lateral sulcus
outlienes temporal lobes
fissures
deep groups
longitudinal fissure
seperates 2 hemispheres
transverse fissure
seperates cerebrum and cerebellum
gyri
ridges
cerebral cortex
site if conscious mind: awareness, sensory perception, voluntary motor initiation, communication, memory storage, understanding
4 general considerations of cerebral cortex:
each hemisphere is concerned with contralateral (opposite) site of body
lateralization (specialization) of cortical function can occur in only 1 hemisphere
conscious behavior involves entire cortex in one way or another
contains 3 types of functional areas
association areas
integrate diverse information
sensory areas
conscious awareness of sensation
motor areas
control voluntary movement
matter and ventricles
gray matter
short, no myelinated neurons and cell bodies
white matter
myelinated and nonmyelinated axons
ventricles
cerebrospinal fluid filled chambers that are continuous to one another and to central canal of spinal cord
third ventricle
connected to lateral ventricle via interventicular foramen; lies in diencephalon
fourth ventricle
connected to 3rd ventricle via cerebral aqueduct; lies in hindbrain
lateral ventricle
large, c-shaped chambers located deep in each hemisphere
cerebellum
contains thin cortex of gray matter with distinctive treelike pattern of white matter called arbor vitae
functions:
processes input from cortex, brain stem, and sensory receptors to provide precise, coordinated movements of skeletal muscles
plays role in thinking, language, and emotion
balance and coordination
Cranial Nerves
( II )
Optic Nerves
Sensory (visual) function
( III )
Oculomotor Nerves
motor nerves to eye
Somatic: directs eyeball, raising upper eyelid
Parasympathetic:
( IV )
Trochlear Nerves
primarily motor nerve that directs eyeball
( V )
Trigeminal Nerves
(V1)
oprithalmic passes through superior orbital fissure
(V2)
maxillary passes through foramen roturidum
(V3)
mandibular passes through the foramen ovale
( I )
Olfactory Nerves
Sensory nerves of smell
( VI )
Abducens Nerves
a motor, inntervatinf lateral rectus muscle
( VII )
Facial Nerves
facial expression, parasympathetic impulses to lacrimal and salivary glands
sensory function (taste) from anterior 2-3rds of tongue
( VIII )
Vestibulocochlear Nerves
sensory function, adjustment of sensitivity of receptors
( IX )
Glossopharyngeal Nerves
motor functions
innervate part of tongue and pharynx for swallowing and provide parasympathetic fibers to parotid salivary glands
sensory functions
fibers conduct taste and general sensory impulses from pharynx and Posterior tongue, and impulses from carotid chemoreceptors and baroreceptors
( X )
most motor fibers are parasympathetic fibers that regulate activities of heart, lungs, and abdominal viscera
sensory fibers carry impulses from thoracic and abdominal viscera, barareceptors, chemoreceptors, and taste buds of posterior tongue and pharynx
( XI )
Accessory Nerves
formed from C1-C5 region of spinal cord (not brain)
supply motor fibers to trapezius and sternocleidomastoid muscles, which together move head and neck, and convey proprioceptor impulses from same muscles
( XII )
Hypoglossal Nerves
intervate extrinsic and intrinsic muscles of tongue that contribure to swallowing and speech
Connective Tissue Coverings
perineurium
coarse connective tissue that bundles fibers into fascicles
epineurium
tough fibrous shealths around all fascicles to form the nerve
endoneurium
loose connective tissue that encloses axons and their myelin shealths
Tissues
nervous tissue consists of 2 principal cell types
neuroglia (glial cells)
small cells that surround and wrap delicate neurons
neuroglia of the PNS
Satellite cells
surround neuron cell bodies in PNS
Schwann cells (neurolemmocytes)
surround all peripheral nerve fibers and form myelin shealths in thicker nerve fibers
vital to regeneration of damaged peripheral nerve fibers
neuroglia of the CNS
astrocytes
most abundant, versatile, and highly branched of glial cells
cling to neurons, synaptic endings, and capillaries
functions: support and brace neurons; guide migration of young neurons of young neurons; respond to nerve impulses and neurotransmitters; influence neuronal functioning; plays role in exchanges between capillaries and neurons; control chemical environment around neurons; participate in information processing in brain
microglial cells
small, ovoid cells with thorny processes that touch and monitor neurons
migrate toward injured neurons
can transform to phagocytize microorganism and neuronal debris
ependymal cells
range in shape from squamous to columnar
may be ciliate; line the central cavities of brain and spinal column; form permeable barrier between cerebrospinal fluid (CSF) in cavities and tissue fluid bathing CNS cells
oligodendrocytes
branched cells
processes wrap CNS nerve fibers, forming insulating myeling shealths in thicker nerve fibers
neurons (nerve cells)
excitable cells that transmit electrical signals
all have cell body and 1 or more processes
extreme longetivity
amitotic
high metabolic rate: requires oxygen and glucose
Neurotransmitters
major of ANS are acetylcholine (Ach) and norepinephrine (NE)
Ach is release by cholinergic fibers at:
all ANS preganglionic axons and all parasympathetic postganglionic axons
effects of neurotransmitter depends on whether it binds to cholinergic receptors or adrenergic receptors
adrenergic receptors
2 respond to NE or epinephrine
alpha (α) receptors
beta (β) receptors
cholinergic receptors
2 bind Ach
Nicotinic receptors
Muscarinic receptors
NE is released by adrenergic fibers at:
almost all sympathetic postganglionic axons, except at sweat glands (release Ach)
Reflex Arc
the pathway that a reflex takes in the body
3) INTERGRATION CENTER
either monosynaptic or polysynaptic region withing CNS
reflexes are classified functionally
Somatic Reflexes
activate skeletal muscles
Autonomic (visceral) Reflexes
activate visceral effectors (smooth or cardiac muscle or glands)
4) MOTOR NEURON
conducts efferent impulses from integration center to effector organ
2) SENSORY NEURON
transmits afferent impulses to CNS
1) RECEPTOR
site of stimulus action
5) EFFECTOR
muscle fiber or gland cell that responds to efferent impulses by contracting or secreting
Major Parts and Functions of the Spinal Cord
functions: provides 2 way communication to and from brain and body; major reflex center: reflexes are initiated and completed at spinal cord
gross anatomy and protection
epidural space
cushions of fat and network of veins is space between vertebrae and spinal dura mater
denticulate ligaments
extensions of pia mater that secure cord to dura mater
cervical and lumbar enlargements
areas where nerves servicing upper and lower limbs arise from spinal cord
cauda equina
collection of nerve roots at inferior end of vertebral canal
fillum terminal
extends to coccyx
spinal cord cross section anatomy
2 lengthwise grooves that run length of cord partially divide it into right and left halves
ventral (anterior) median fissure
dorsal (posterior) median sulcus
neuronal pathways
major spinal tracts are part of multineuron pathways; 4 key points about spinal tracts and pathways
decussation
most pathways cross from one side of CNS to other at some point
relay
consist of chain of 2 or 3 neurons
somatotopy
precise spatial relationship in CNS correspond to spatial relationship in body
symmetry
pathways are paired symmetrically (right and left)
central canal
runs length of cord; filled with CSF
gray matter and spinal roots
3 areas of gray matter are found on each side of center and are mirror images
ventral horns
some interneurons; somatic motor neurons
lateral horns
only in thoracis and superior lumbar regions; sympathetic neurons
dorsal horns
interneurons that receive somatic and visceral sensory input
divided into 4 groups based on of somatic or visceral innervation
somatic sensory (SS)
visceral sensory (VS)
visceral autonomic motor (VM)
somatic motor (SM)
gray commissure
bridge of gray matter that connects masses of gray matter on either side
ventral roots
bundle of motor neuron axons that exit the spinal cord
dorsal roots
sensory input to cord
dorsal root (spinal) ganglia
cell bodies of sensory neurons
spinal nerves
formed by fushion of dorsal and ventral roots
white matter
myelinated and nonmyelinated nerve fibers allow communication between parts of spinal cord, and brain
run in 3 sections
descending
ascending
transverse
divided into 3 white columns (funiculi) on each side
lateral
ventral (anterior)
dorsal (posterior)