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Natalia Hernandez P.2 Nervous system - Coggle Diagram
Natalia Hernandez P.2
Nervous system
Major Divisions & Subdivisions of the Nervous System
Central Nervous System:
brain & spinal cord of dorsal body cavity; Interprets sensory input and dictates motor output (control center)
Neuroglia
Astrocytes: abundant, versatile, and highly branched glial cells; Cling to neurons, synaptic endings, and capillaries; functions: support & brace neurons
Microglial cells: ovoid cells w/ thorny processes that touch & monitor neurons; Migrate toward injured neurons; Can transform to phagocytize microorganisms and neuronal debris
ependymal cells: squamous to columnar; May be ciliated; Line central cavities of brain & spinal column; Form permeable barrier between CSF in cavities & tissue fluid bathing CNS cells
Oligodendrocytes: Branched cells; Processes wrap CNS nerve fibers, forming insulating myelin sheaths in thicker nerve fibers
Nuclei: clusters of neuron cell bodies in CNS
Tracts: Bundles of neuron processes in CNS; CNS contains both neuron cell bodies and their processes; 2 processes are axons & dendrites
Peripheral Nervous System:
system outside of CNS; consists of spinal & cranial nerves & ganglia ; communication lines between CNS & rest of body; major neuroglia include satellite cells & schwann cells (myelin sheaths)
Sensory (afferent) division:
somatic & visceral sensory nerve fibers convey impulses from skin, skeletal muscles, joints, visceral organs to CNS
Sensory receptors class. by stimulus type: mechanoreceptors (touch), thermoreceptors (temp), photoreceptors (light energy), chemoreceptors (chemicals), nocicereceptors (pain)
Sensory receptors class. by location: exteroceptors (stimuli arising outside bod), interceptors (stimuli arising in internal viscera and blood vessels), proprioceptors (stretch in skeletal muscles, tendons, joints, ligaments, and connective
tissue coverings of bones and muscles)
Somatosensory system: part of sensory system serving body wall and limbs
Levels of neural integration in sensory systems:
1) Receptor level: sensory receptors
2) Circuit level: processing in ascending pathways
3) Perceptual level: processing in cortical sensory areas
Motor (efferent) division:
motor nerve fibers conduct impulses from CNS to effectors
Somatic nervous system (voluntary):
Somatic motor nerve fibers conduct impulses from CNS to skeletal muscle; conscious control of skeletal muscles
Autonomic nervous system (involuntary):
visceral motor nerve fibers that conduct impulses from CNS to & innervate smooth muscles, cardiac muscle, and glands; pathway uses a two-neuron chain of pre- and postganglionic neurons; ACh & NE
Parasympathetic division:
promotes maintenance functions (directs digestion, diuresis, defecation), conserves energy; rest-and-digest system; craniosacral division
Sympathetic division:
mobilized body during activity; fight-or-flight system; Exercise, excitement, emergency, embarrassment activates system; thoracolumbar division
Compare & Contrast the Autonomic Nervous System
ANS
Effectors
: innervates cardiac muscle, smooth muscle, & glands
Efferent pathways & ganglia:
uses 2-neuron chain
preganglionic neuron (cell body in CNS), preganglionic axon
postganglionic neuron (outside CNS); cell body synapses w/ preganglionic axon
Target organ responses to neurotransmitters:
all motor neurons release ACh so effect always stimulatory
Somatic Nervous system
Effectors:
innervates skeletal muscles
Efferent pathways & ganglia:
cell body in CNS & myelinated axon extends in spinal or cranial nerves directly to skeletal muscle
Target organ responses to neurotransmitters
: preganglionic fibers release ACh, post. release NE; effect either stimulatory or inhibitory, depending on type of receptors
both have motor fibers ^; most spinal & cranial nerves both somatic & autonomic fibers; adaptation usually involve both skeletal & visceral organs
Connective Tissue Coverings
Endoneurium:
loose CT that encloses axons & their myelin
sheaths (Schwann cells)
Perineurium:
coarse CT that bundles fibers into fascicles
Epineurium:
tough fibrous sheath around all fascicles to form the nerve
Classification of Neurons
Multipolar:
three or more processes (1 axon, others dendrites); most common and major neuron type in CNS
Bipolar:
two processes (one axon, 1one dendrite); rare (ex: retina and olfactory mucosa)
Unipolar
: one T-like process (two axons); slso called pseudounipolar
Action Potential & the Nerve Impulse
Resting membrane potential:
electrical charge of a neuron when not active; average approximately -70mV; cytoplasmic side of membrane is negatively charged relative to the outside (polarized)
Sodium-potassium pump:
stabilizes resting MP by maintaining concentration gradients for sodium & potassium; 3 Na+ pumped out of cell while 2 K+ are pumped into cell
resting membrane potential generated by differences in ionic composition; differences in plasma membrane permeability (sodium-potassium pump); changes generate --->
Graded potentials: incoming signals operating over short distances
Action potential: long distance signals of axons; principal way neurons send signals
Main steps to generating an Action Potentia
l
Depolarization:
Na+ channels open; Na+ entry into cell; @ threshold (-55 to -50 mV), positive feedback opening of all Na+ channels; results in AP spike
Repolarization:
Na+ channels inactivating, K+ channels opening; membrane returns to resting membrane potential
Resting state:
All gated Na+ and K+ channels are closed; only leakage channels open; maintains resting MP
Hyperpolarization:
some K+ channels remain open, Na+ channels reset; inside of membrane becomes more negative than in resting state; slight dip below resting voltage
Refractory period:
time in which neuron cannot trigger another AP' voltage-gated Na+ channels are open, so neuron cannot respond to another stimulus
Nerve impulse:
generated by axon (conducting region of neuron)
transmitted along axolemma (neuron cell
membrane) to axon terminal; terminal is region that secretes neurotransmitters (contained in synaptic vesicles), which are released into extracellular space
Synaptic cleft (fluid-filled space) prevents nerve impulses from directly passing from one neuron to next
Disorders/Diseases
Hypothalamic disturbances:
body wasting, obesity. sleep disturbances, dehydration, emotional imbalances
epileptic seizure:
torrent of electrical discharges by groups of neurons, prevent any other messages from getting thru, causes uncontrollable jereing, stiffness; maybe gentic factors, also brain injuries; treatment; anticonvulsive drugs
Meningitis:
inflammation of meninges, may spread to CNS and cause encephalitis
Hydrocephalus:
obstruction blocks CSF circulation of drainage = increased pressure; cause enlarged head and/or brain damage; treatment: drain CSF w/ ventricular shunt
Alzheimer's:
progressive degenerative disease of brain that results in dementia, memory loss; plaques of beta-amyloid peptides form; neurofibrillary tangles kill neurons; brain shrinks
Parkinson's:
degeneration of dopamine releasing neurons; associated w/ tremors at rest; cause unknown but maybe due to unknown mitochondrial abnormalities; treatment includes L-dopa, gene therapy
Huntington's:
fatal hereditary disorder caused by accumulation of protein in brain cells; leads to degeneration of basal nuclei & cerebral cortex; initial symptoms include wild flapping movements, later mental deterioration; fatal within 15 years; Treated with drugs that block dopamine effects, maybe stem cell implant
Autonomic neuropathy:
damage to autonomic nerves, common complication of diabetes mellitus; signs include sexual dysfunction, dizziness; preventable by maintain good blood glucose levels
Hypertension:
high blood pressure; overactive sympathetic vasoconstrictor response to stress; heart works harder. artery walls subject to wear & tear; treated w/ adrenergic receptor-blocking drugs
Raynaud's disease
: vasoconstriction in fingers and toes, digits turn cyanotic; treated w; vasodilators
Autonomic dysreflexia:
life threatening,uncontrolled activation of autonomic neurons in quadriplegics & people w/ spinal cord injuriesabove T6; blood pressure skyrockets = increased risk for stroke
Hyperaglesia:
pain amplification, can be learned by spinal cord
Multiple sclerosis:
autoimmune disease that progressively destroys the myelin sheaths of neurons in the brain and spinal cord and turns them into lesions called scleroses, primarily young adults; symptoms include visual disturbances, loss of muscular control; treatment includes drugs that modify immune system
Spina bfida:
incomplete formation of vertebral arches, usually lumbosacral region; caused by lack of folic acid pina bifida occulata: least serious,one or few missing vertebrae;
Cerebral palsy:
neuromuscular disability resulting in disconnect between brain & muscle movement; hypoxia a cause; can cause seizures and abnormal gait; no cure but surgical intervention possible
anencephaly:
cerebrum & parts of brain stem never develop. Neural fold fails to fuse, child is vegetative. Death occurs soon after birth
Amyotrophic lateral sclerosis (ALS):
also called Lou Gehrig's Disease; Destruction of ventral horn motor neurons & fibers of pyramidal tract; caused by environmental factors and genetic mutations involving RNA processing; symptoms: loss of ability to speak, swallow, and breathe; death within 5 years
Spinal cord trauma:
Localized injury to spinal cord or its roots leads to functional losses
Spinal shock:
transient period of functional loss caudal to lesion
Paresthesias:
caused by damage to dorsal roots or sensory tracts; sensory function loss
Paralysis:
caused by damage to ventral roots or ventral horn cells; motor function loss; flaccid or spastic; occurs on opposite side of body from damage; control over movement not lost, only impaired
Paraplegia:
paralysis waist down
Quadriplegia
: paralysis of all 4 limbs
Stroke:
caused by interruption in blood flow to the brain due to a blockage or bleeding in a cerebral artery; Tissue plasminogen activator (TPA) only treatment for stroke
Ischemia:
an inadequate blood supply, leading to death of tissue
Hemiplegia
: paralysis of one side of the body, sensory and speech deficits may result
Brain Injuries:
Concussion:
temp alteration in function of brain
Contusion:
permanent damage of brain
subdural/subarachnoid hemorrhage:
pressure from blood may force brain stem thru foramen magnum = death
Cerebral edema:
swelling of brain associated w/ traumatic head injury
Major Parts & Functions of the Spinal Cord
Overall function:
provide 2-way communication to and from brain, contains spinal reflex centers
Epidural space:
cushion of fat & network of veins in space between vertebrae & spinal dura mater; SCF between arachnoid & pia
Filum terminale:
fibrous extension of pia mater; anchors spinal cord to coccyx
Conus medullaris:
cone-shaped structure where spinal cord terminates
Denticulate ligaments:
extensions of pia mater that secure cord to dura mater
Cervical and lumbar enlargements:
areas where nerves servicing upper & lower limbs arise from spinal cord
Spinal nerves:
31 pairs arising from spinal cord; fusion of dorsal & ventral roots
Cauda equina (horse's tail):
collection of nerve roots @ inferior end of vertebral canal
Ventral (anterior) median fissure:
more open of 2 grooves that partially divide spinal cord into left & right
Dorsal (posterior) median sulcus:
narrow groove on posterior midline of spinal cord
Central canal:
tiny channel in cord filled with CSF
Dorsal horns:
inteneurons that receives somatic & visceral sensory input; gray matter
Ventral horns:
2 ventral arms of spinal gray matter; contain interneurons & somatic motor neurons
Lateral horns:
(thoracic & superior lumbar regions only), sympathetic neurons; gray matter
Gray commissure:
bridge of gray matter that connects masses of gray matter on either side; encloses central canal
Ventral roots
: bundle of motor neuron axons, exit spinal cord
Dorsal roots:
sensory input to cord
Dorsal root (spinal) ganglia:
cells bodies of sensory neurons
Spinal Nerves: 31 paired roots arising from spinal cord; part of PNS
8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal
Reflex Arc: neural pathway that controls a reflex.
Somatic reflex arc
1) Receptor
2) Sensory neuron
3) Integration center
4) Motor neuron
4) Effector
Visceral (involuntary) reflex arc:
same components but 3 differences
1) Visceral reflex arc has 2 consecutive neurons in the motor pathway
2) Afferent fibers = visceral sensory neurons
3) Effectors = smooth muscle, cardiac muscle, & glands not skeletal muscles
Major Functions of the Nervous System
Nervous system known as the master controlling & communicating system of the body; 3 overlapping functions
Integration: responsible for processing and interpreting info from sensory receptors
Motor output: activates effector organs (muscles & glands) which then produce a response
Sensory input: info gathered by sensory receptors about internal & external changes
Tissues
Neurons (nerve cells): structural units of nervous system
Large, highly specialized cells that conduct impulses; ex) Presynaptic neuron: conducting impulses toward synapse (sends info) & Postsynaptic neuron: transmitting electrical signal away from synapse (receives info)
characteristics: extreme longevity, amitotic, high metabolic rate; Sensory (unipolar), motor (multipolar), & interneurons (between sensory & motor, 99% of body’s neurons are interneurons)
comprised of cell body (Biosynthetic center that contains nucleus) & one or more processes
Nuclei: clusters of neuron cell bodies in CNS
Ganglia: clusters of neuron cell bodies in PNS
dendrites:
short, tapering, diffusely branched
processes
axon:
long, starts at cone-shaped area called axon hillock; distal endings called axon terminals or terminal boutons
Neuroglia (glial cells): small cells that surround and wrap delicate neurons
of CNS: Astrocytes, microglial cells, ependymal cells, Oligodendrocytes (look at CNS for descriptions)
of PNS:
Satellite cells
(surround neuron cell bodies in PNS, sim. function to astrocytes),
Schwann cells
(neurolemmocytes, surround all peripheral nerve fibers and form myelin sheaths; Vital to regeneration of damaged peripheral nerve fibers)
Major Parts & Functions of the Brain
Cerebral Hemispheres:
form superior part of brain & account for 83% of brain mass
Surface markings
Gyri:
ridges (hills)
Sulci:
shallow grooves
Fissures:
deep grooves; Longitudinal fissure separates both hemispheres & Transverse fissure sep. cerebrum from cerebellum
Lobes
Frontal:
Central sulcus separates precentral gyrus of frontal lobe and postcentral gyrus of parietal lobe
Parietal
Temporal:
Lateral sulcus outlines temporal lobes
Occipital:
Parieto-occipital sulcus separates occipital and parietal lobes
Insula
each hemisphere has 3 basic regions:
White matter
internally
Cerebral cortex:
superficial gray matter, outline
motor areas of cerebral cortex: l
ocated in frontal lobe, motor areas act to control voluntary movement; primary motor cortex, premotor cortex, Broca's area, frontal eye fiel
sensory areas of cerebral cortex
Areas of cortex concerned with conscious awareness of sensation
In parietal, insular, temporal, and occipital lobes
Eight main areas include primary somatosensory cortex, somatosensory association cortex, visual areas, auditory areas, vestibular cortex, olfactory cortex, gustatory cortex, and visceral sensory area
Basal nuclei
deep within white matter; includes caudate nucleus, putamen, & globus pallidus (last 2 make striatum); primary function is motor control
Diencephalon:
3 structures enclose 3rd ventricle
Thalamus:
brain’s sensory control center, located on top of the brainstem; directs sensory messages to the cortex and transmits replies to the cerebellum and medulla.
Hypothalamus:
below thalamus, contains mammillary bodies & infundibulum; is the main visceral control®ulating center vital to homeostasis; controls ANS & Initiates physical responses to emotions
Epithalamus:
most dorsal, forms roof of 3rd ven.; contains pineal body, which secretes melatonin
Brain Stem
Pons:
4th ventricle sep pons from cerebellum; nuclei play role in reticular formation & some help maintain normal rhythm of
breathing
Medulla Oblongata:
Blends into spinal cord at foramen magnum; contains 4th ventricle & choroid plexus (membrane); controls heartbeat and breathing.
Midbrain:
between diencephalon & pons; structures involved include cerebral peduncles, cerebral aqueduct; nuclei scattered thru corpora quadrigemina (superior & inferior), substantia nigra
Cerebellum
the “little brain” at the rear of the brainstem; 11% of brain mass; Cerebellar hemispheres connected by wormlike vermis
functions include processing sensory input, coordinating movement output and balance, and enabling nonverbal learning and memory
arbor vitae: white matter (meyelinated) of cerebellum, looks like a tree
Other structures/features
Ventricles:
Lateral ventricles (large, c-shaped, sep By septum pellucidum) , 3rd ventricle (connected to lateral via interventricular foramen), 4th ventricle (connected to 3rd via cerebral aqueduct)
Drugs of Abuse
Marijuana:
interferes w/ inhibitory & dopamine ntm, inhibition turned off, dopamine released uncontrollably; produces feelings of euphoria and relaxation; users prone to memory loss, confusion, and anxiety
Methamphetamine:
interferes w/ dopamine ntm b/c mimics it, its taken into cell by transporters, dopamine forced out, excess dopamine overstimulates cell; makes user feel intense pleasure & exhilaration
Ecstasy
: interferes w/ serotonin neurotransmitters by taking its place, serotonin transported out of cell, binds again & again to receptors, overstimulating cell; makes user more energized
Alcohol:
interferes w/ GABA inhibitory & glutamate ntm, makes GABA receptors inhibitory & binds to glutamate receptors, glutamate prevented from exiting cell; user's memory, decision making, & impulse control affected
Heroine:
interferes w'/ inhibitory & dopamine neurotransmitters by binding to opiate receptors; stops release of inhibitory, release of dopamine incontrollable' creates feelings of sedation & well being
Cocaine:
interferes w/ dopamine ntm by blocking dopamine receptors, dopamine trapped in cleft, overstimulates cell; affects part of brain controlling voluntary movement, user will be fidgety
LSD:
interferes w/ serotonin ntm by either exciting or inhibiting serotonin receptors; will cause feelings of wakefulness & evoke a startle response to unexpected stimulus
Neurotransmitters
Norepinephrine (NE):
released by adrenergic fibers @ almost all sympathetic postganglionic axons, except @ sweat glands; a biogenic amine
Biogenic amines:
play roles in emotional behaviors and biological clock
Catecholamine:
a class of amines that includes the neurotransmitters dopamine, norepinephrine, and epinephrine
Indolamines:
a class of amines that includes serotonin, histamine
Acetylcholine (ACh):
Released @ neuromuscular junctions; Synthesized from acetic acid & choline by enzyme choline acetyltransferase; used by CNS and ANS neurons, in ANS released by cholinergic fibers @ ANS pre- & postganglionic axons
Amino acids:
building blocks of all proteins, some act as neurotransmitters
Peptides (neuropeptides):
Strings of amino acids that have diverse functions, includes endorphins
Gases and lipids
Endocannabinoids: Act at same receptors as THC (active ingredient in marijuana)
Purines:
monomers of nucleic acids that affect both CNS and PNS
Cranial Nerves: 12 pairs; numbered (I through XII) and named from rostral (front) to caudal (back)
Cranial nerve I: Olfactory
(smell); purely sensory
Cranial Nerve II: Optic
(vision) - purely sensory; arise from retinas; partially cross over at optic chiasma (x-shaped); Optic radiation fibers run to occipital (visual) cortex
Cranial Nerve III: Oculomotor
- fibers extend to 4/6 extrinisic eye muscles, raise eye lids, pupillary constriction, change lens shape
Cranial Nerve IV: Trochlear
, innervates superior oblique; primary motor nerve that directs eyeball
Cranial Nerve V: Trigeminal Nerve
- largest, sensory impulses from various areas of face; 3 divisions including ophthalmic, maxillary, & mandibular; motor fiber for mastication
Cranial Nerve VI: Abducens
- primary motor nerve innervating lateral rectus msucle (eyeball)
Cranial Nerve VII: Facial Nerve
- chief motor nerves of face for facial expression, parasympathetic impulses to lacrimal & salivary glands; sensory function (taste for 2/3 of tongue)
Cranial Nerve VIII: Vestibulocochlear
- hearing & balance; mostly sensory; auditory nerve;
Cranial Nerve IX: Glossopharyngeal
-
motor: depress tongue, & pharynx for swallowing & parasympathetic fibers to parotid salivary glands
sensory: conduct taste, general sensory impulses from pharynx & posterior tongue, carotid chemreceptors & baroreceptors
Cranial Nerve X: Vagus Nerve
- only cranial nerve to extend beyond head & neck; motor fibers help to regulate activities of heart, lungs, & abdominal viscera; sensory fibers carry impulses from thoracic & abdominal viscera, baroreceptors, chemoreceptors and taste buds of tongue and pharynx
Cranial Nerve XI: Accessory nerve
- formed from C1 to C5 of spinal cord; innervates trapezius & sternocleidomastoid so responsible for shrugging
Cranial Nerve XII: Hypoglossal nerve
- innervate extrinsic & intrinsic muscles of tongue (swallowing & speech)