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Jessica Velazquez Period 3 Nervous System - Coggle Diagram
Jessica Velazquez
Period 3
Nervous System
Major parts and functions of the spinal cord
Enclosed in vertebral column; extends from foramen magnum to L1/L2.
Protected by vertebrae, meninges, CSF.
Functions:
two-way communication, reflex center.
Gross Anatomy
Conus medullaris, Filum terminale, Cauda equina.
Cross-Section
Gray Matter:
dorsal horns (sensory), ventral horns (motor), lateral horns (sympathetic), central canal.
White Matter:
myelinated fibers; dorsal, lateral, ventral columns; ascending, descending, transverse tracts.
Spinal Roots
Dorsal roots:
sensory; dorsal root ganglia.
Ventral roots:
motor.
Fuse to form spinal nerves.
Action potential & the Nerve Impulse
An action potential (AP) is the neuron’s primary long-distance signal, created by a brief reversal of membrane potential (~100 mV). The resting membrane potential (–70 mV) is maintained because K+ diffuses out more than Na+ enters, stabilized by the Na+/K+ ATPase pump (3 Na+ out, 2 K+ in).
Signal Types:
Graded potentials:
short-distance.
Action potentials:
long-distance.
Terminology:
Depolarization:
membrane potential moves toward zero; increased AP probability.
Hyperpolarization:
membrane potential moves farther from zero; decreased AP probability.
AP Generation:
Resting state:
all gated Na+ and K+ channels closed.
Depolarization:
voltage-gated Na+ channels open; threshold (–55 to –50 mV) triggers full spike to +30 mV.
Repolarization:
Na+ inactivation gates close; voltage-gated K+ channels open.
Hyperpolarization:
excess K+ efflux; Na+ channels reset.
Major functions of the nervous system
Master controlling and communicating system using electrical and chemical signals
Responses are rapid, specific, and immediate
Three Functions:
Sensory Input: Sensory receptors detect internal/external changes.
Integration: CNS processes and interprets input (control center).
Motor Output: Activates effector organs (muscles/glands).
Tissues
Neuroglia (Glial Cells)
CNS (4 types):
Astrocytes:
support neurons, maintain chemical environment, guide migration, information processing.
Microglial Cells:
monitor neurons; phagocytize debris.
Ependymal Cells:
line ventricles; circulate CSF.
Oligodendrocytes:
form CNS myelin sheaths.
PNS (2 types):
Satellite Cells:
support neuron cell bodies.
Schwann Cells:
form PNS myelin, vital for regeneration.
Neurons:
Excitable, transmit electrical signals; long-lived, high metabolic rate, amitotic.
Cell Body (Soma):
biosynthetic center.
Dendrites:
receptive region; graded potentials.
Axon:
conducting region; generates and transmits impulses; axon terminals release neurotransmitters.
Spinal nerves
There are 31 mixed spinal nerve pairs: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal.
Ventral roots:
motor (efferent).
Dorsal roots:
sensory (afferent). They unite to form a spinal nerve.
Dermatomes:
skin regions served by a single spinal nerve (except C1); overlapping prevents complete anesthesia.
Connective Tissue Coverings
Myelin Sheath
Protein-lipid insulation that speeds impulse transmission.
PNS
: Schwann cells; Nodes of Ranvier.
CNS:
oligodendrocytes (one cell to many axons).
PNS Connective Tissue Layers
Endoneurium
: surrounds axon + myelin.
Perineurium:
surrounds fascicles.
Epineurium
: surrounds the entire nerve.
Meninges (CNS Protection)
Dura mater (outer), Arachnoid mater (middle; CSF in subarachnoid space), Pia mater (inner, vascular).
Reflex arc
A reflex is a rapid, automatic, predictable response.
Types:
inborn, learned, somatic, autonomic.
Reflex Arc:
Receptor
Sensory neuron
Integration center (mono-/polysynaptic)
Motor neuron
Effector
Major divisions and subdivisions of the nervous system
Peripheral Nervous System (PNS)
Nervous system outside the CNS.
Cranial nerves + spinal nerves.
PNS Functional Divisions
Sensory (Afferent) Division:
Somatic sensory fibers: skin, skeletal muscle, joints to CNS.
Visceral sensory fibers: organs to CNS.
Motor (Efferent) Division:
Somatic Nervous System (Voluntary): somatic motor fibers to skeletal muscle.
Autonomic Nervous System (ANS): visceral motor fibers to smooth muscle, cardiac muscle, glands.
Sympathetic
Parasympathetic
Central Nervous System (CNS)
Brain + Spinal cord (dorsal body cavity).
Main integration and control center; interprets sensory input and directs motor output.
Cranial nerves
There are 12 pairs of cranial nerves (I–XII); most are mixed, except I and II which are sensory.
I Olfactory: smell
II Optic: vision
III Oculomotor: eyelid elevation, ocular movement, iris, lens
IV Trochlear: superior oblique muscle
V Trigeminal: facial sensation; mastication
VI Abducens: lateral rectus muscle
VII Facial: facial expression; lacrimal/salivary glands; taste (anterior 2/3)
VIII Vestibulocochlear: hearing & equilibrium
IX Glossopharyngeal: swallowing; parotid gland; taste/sensory posterior tongue
X Vagus: parasympathetic control of heart, lungs, viscera; visceral sensory
XI Accessory: trapezius & sternocleidomastoid
XII Hypoglossal: tongue movements
Major parts and functions of the brain
Cerebral Hemispheres
83% of brain; gyri, sulci, fissures; lobes (frontal, parietal, temporal, occipital, insula).
Cerebral Cortex (Gray Matter) - Conscious mind: sensory perception, memory, voluntary motor control.
Functional Areas:
Motor areas:
Primary motor cortex, premotor cortex, Broca’s area.
Sensory areas:
Primary somatosensory cortex.
Association areas:
integrate information.
Lateralization:
Left:
language, math, logic
Right:
visual-spatial, intuition, emotion, artistic/musical
Cerebral White Matter
Communication between cortical areas and CNS.
Basal Nuclei
Regulate movement intensity, inhibit unnecessary movements; linked to Parkinson’s & Huntington’s.
Diencephalon
Thalamus:
relay/sorting center for sensory input.
Hypothalamus:
visceral control center; ANS, temperature, hunger, thirst, endocrine control.
Epithalamus:
pineal gland to melatonin (sleep-wake cycle).
Brain Stem
Coordination of precise skeletal muscle movements; also involved in balance, language, emotion; has arbor vitae.
Cerebellum
Midbrain:
superior colliculi (visual reflexes), inferior colliculi (auditory), substantia nigra.
Pons:
breathing rhythm.
Medulla Oblongata:
cardiovascular & respiratory centers; controls swallowing, vomiting, coughing.
Disorders/Diseases
Nervous Tissue/Conduction:
Multiple sclerosis:
CNS demyelination.
Meningitis:
meninges inflammation.
Paresthesias
: sensory loss.
Paralysis:
motor loss.
Brain/Fluid Disorders:
Concussion, contusion, cerebral edema, hydrocephalus, stroke (ischemia).
Degenerative/Hereditary:
Alzheimer’s:
β-amyloid plaques; neurofibrillary tangles.
Parkinson’s:
loss of dopamine neurons.
Huntington’s:
mutant huntingtin; neuronal degeneration.
ALS:
motor neuron destruction.
How it affects people:
Congenital:
Cerebral palsy:
motor impairment.
Spina bifida:
incomplete vertebral arches.
Autonomic Disorders:
Autonomic neuropathy, hypertension, Raynaud’s disease.
Drugs of abuse
Heroine:
Neurotransmitters:
Inhibitory & Dopamine
Receptors:
Dopamine & Opiate
How neurotransmitters are affected in the brain:
Inhibitory signals normally stop dopamine release.
Heroin mimics natural opiates and binds to opiate receptors, shutting off that inhibition.
This allows dopamine to flood the synapse.
How it affects people:
Immediate feelings of sedation and well-being
Transmission of pain signals, stress response and emotional attachment
Ecstasy:
Neurotransmitters/receptors/transporters:
Serotonin
How neurotransmitters are affected in the brain:
Serotonin is removed from the synaptic cleft.
A serotonin-like molecule is taken up by transporters.
It reverses the transporters, pushing serotonin out of the cell.
Extra serotonin gets stuck in the cleft and keeps activating receptors.
How it affects people:
Serotonin pathways control mood, sleep, perception, and appetite.
Extra serotonin triggers a mild dopamine release, giving ecstasy its addictive effect.
Marijuana:
Neurotransmitters:
Inhibitory & Dopamine
Receptors:
Dopamine & cannabinoid
How neurotransmitters are affected in the brain:
Cannabinoid receptors shut off inhibitory neurotransmitters.
THC mimics anandamide and binds to these receptors.
Inhibition stops, so dopamine is released into the synapse.
How it affects people:
Anandamide affects short-term memory and slows movement.
THC causes a stronger, longer “high” than natural anandamide.
Methamphetamine:
Neurotransmitters/receptors/transporters:
Dopamine
How neurotransmitters are affected in the brain:
Meth enters dopamine vesicles and pushes dopamine out.
Transporters reverse and pump dopamine into the synapse.
Extra dopamine gets trapped and keeps activating receptors.
How it affects people:
Strong activation of the reward pathway causes intense pleasure and energy.
Alcohol:
How it affects people:
Hurts memory, decision-making, and impulse control.
Receptors:
Gaba inhibitory
Neurotransmitters:
Glutamate
How neurotransmitters are affected in the brain:
Boosts GABA’s inhibitory effect.
Blocks glutamate receptors so excitation can’t happen.
Cocaine:
How it affects people:
Strong reward pathway activation.
Causes restlessness and inability to stay still.
Neurotransmitters/receptors/transporters:
Dopamine
How neurotransmitters are affected in the brain:
Normally, transporters remove dopamine.
Cocaine blocks these transporters, so dopamine stays and keeps activating receptors.
LSD:
How it affects people:
Heightened awareness, wakefulness, and strong reactions to unexpected stimuli.
How neurotransmitters are affected in the brain:
Can inhibit or excite serotonin receptors.
Strongly excites the locus coeruleus (LC), which connects to many sensory areas.
Neurons/receptors:
Serotonin
Classification of neurons
Structural
Multipolar
: 3+ processes; most common; CNS.
Unipolar (Pseudounipolar):
one T-shaped process; mostly sensory.
Bipolar:
2 processes; rare (retina, olfactory mucosa).
Functional
Sensory (Afferent):
impulses → CNS; mostly unipolar; cell bodies in ganglia.
Motor (Efferent):
impulses → effectors; multipolar; cell bodies in CNS.
Interneurons:
integrate info within CNS; 99% of all neurons.
Compare & contrast the autonomic nervous system
The ANS provides involuntary motor control of cardiac muscle, smooth muscle, and glands.
Feature
Effectors
Pathway
Neurotransmitter
Response
Somatic Nervous System
Skeletal muscle
Single neuron
ACh
Stimulatory
Autonomic Nervous System
Cardiac, smooth, glands
Preganglionic + postganglionic
ACh or NE
Stimulatory or inhibitory
Parasympathetic ("Rest-and-Digest"):
craniosacral; long preganglionic, short postganglionic; maintains homeostasis and conserves energy.
Sympathetic ("Fight-or-Flight"):
thoracolumbar; increases HR, dilates bronchioles, redirects blood; innervates sweat glands and vascular smooth muscle.
Neurotransmitters
Neurotransmitters are chemical messengers of the nervous system (50+ identified).
Major Classes:
Acetylcholine (ACh):
NMJ, ANS, CNS.
Biogenic amines:
dopamine, norepinephrine, epinephrine, serotonin, histamine.
Amino acids:
some act as neurotransmitters.
Peptides:
e.g., endorphins (natural opiates).
Endocannabinoids:
bind THC receptors.
Functions:
Excitatory or inhibitory (receptor-dependent).
Direct vs. indirect actions via ion channels or second messengers.
ANS Neurochemistry:
ACh:
all preganglionic fibers; parasympathetic postganglionic; nicotinic/muscarinic receptors.
NE:
most sympathetic postganglionic; α and β receptors.