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Nervous System Hugo Ramirez Period 3 - Coggle Diagram
Nervous System Hugo Ramirez Period 3
Spinal nerves
31 pairs total
8 cervical (C1–C8)
12 thoracic (T1–T12)
5 lumbar (L1–L5)
5 sacral (S1–S5)
1 coccygeal (Co1)
All are mixed nerves (sensory + motor)
Form plexuses (cervical, brachial, lumbar, sacral)
Reflex arc
Receptor: detects stimulus (e.g., stretch, pain)
Sensory neuron: carries signal to spinal cord
Integration center: interneuron in spinal cord
Motor neuron: sends command to muscle
Effector: muscle contracts or gland responds
Fast & involuntary response
Tissues
Neurons (Structure & Function)
Dendrites: receive signals
Cell body (soma): contains nucleus; processes info
Axon: sends impulses
Myelin sheath: insulation; increases speed
Nodes of Ranvier: gaps where impulses jump
Axon terminals: release neurotransmitters
Function: transmit electrical impulses rapidly
Neuroglia (Support Cells)
CNS Glial Cells:
Astrocytes: blood-brain barrier; nutrient exchange
Oligodendrocytes: produce myelin in CNS
Microglia: immune defense; remove debris
Ependymal cells: create and circulate CSF
PNS Glial Cells:
Schwann cells: myelin in PNS
Satellite cells: protect and support PNS cell bodies
Drugs of abuse
Cocaine
Blocks dopamine reuptake → floods synapse
Intense high; highly addictive
Methamphetamine
Forces massive dopamine release
Damages dopamine receptors
Heroin
Mimics endorphins
Pain relief + euphoria
Marijuana (THC)
Activates cannabinoid receptors
Alters memory, coordination
Alcohol
Enhances GABA → depressing effect
Impairs motor coordination
Ecstasy (MDMA)
Releases serotonin
Affects mood, empathy
Autonomic nervous system: Similarities and differences
Sympathetic (“Fight or Flight”)
Increases heart rate
Dilates pupils
Increases breathing
Releases adrenaline
Slows digestion
Opens airways
Parasympathetic (“Rest & Digest”)
Slows heart rate
Constricts pupils
Stimulates digestion
Conserves energy
Normal body maintenance
Comparison
Both are involuntary
Both use 2-neuron pathway (preganglionic + postganglionic)
Use different neurotransmitters (ACh vs. NE)
Cranial nerves
I – Olfactory (smell)
II – Optic (vision)
III – Oculomotor (eye movement)
IV – Trochlear (eye movement)
V – Trigeminal (face sensation, chewing)
VI – Abducens (eye movement)
VII – Facial (facial expression, taste)
VIII – Vestibulocochlear (hearing, balance)
IX – Glossopharyngeal (taste, swallowing)
X – Vagus (heart, lungs, digestive organs)
XI – Accessory (neck and shoulder muscles)
XII – Hypoglossal (tongue movement)
Major parts and functions of the brain
Cerebrum
Largest part
Functions: reasoning, thinking, emotions, language, sensory interpretation
Divided into lobes:
Frontal: decision-making, voluntary movement
Parietal: touch, pressure, temperature
Temporal: hearing, memory, language
Occipital: vision
Diencephalon
Thalamus: sensory relay station
Hypothalamus: hormone control, hunger, thirst, temperature
Pineal gland: sleep/wake cycles (melatonin)
Brain Stem
Midbrain: visual/auditory reflexes
Pons: breathing regulation, communication with cerebellum
Medulla: heart rate, blood pressure, breathing; life-sustaining
Cerebellum
Coordination of movement
Balance, posture
Motor learning
Major functions of the nervous system
Sensory Input
Detects internal changes (blood pressure, CO₂ levels)
Detects external stimuli (touch, temperature, pain, sound, light)
Uses sensory receptors throughout the body
Sends information to CNS through afferent neurons
Integration
CNS analyzes sensory information
Makes decisions based on past experience and current condition
Occurs mainly in brain and spinal cord
Creates conscious and subconscious responses
Motor Output
CNS sends commands to effectors
Somatic: skeletal muscle movement
Autonomic: smooth muscle, cardiac muscle, glands
Produces both voluntary and involuntary actions
Classification of neurons
Structural
Unipolar: sensory neurons
Bipolar: rare; vision, smell
Multipolar: most common; motor neurons, interneurons
Functional
Sensory (afferent): detect stimuli and send to CNS
Motor (efferent): send commands to muscles/glands
Interneurons: connect neurons inside CNS; decision-making
Major divisions and subdivisions of the nervous system
Central Nervous System (CNS)
Brain: control center for thoughts, emotions, memory, and coordination
Spinal Cord: pathway for signals; controls reflexes
Peripheral Nervous System (PNS)
All nerves outside CNS
Connects organs and limbs to the CNS
Sensory (Afferent) Division
Carries incoming signals to CNS
Somatic sensory: skin, skeletal muscles, joints
Visceral sensory: organs (heart, stomach, bladder)
Motor (Efferent) Division
Carries outgoing signals to muscles/glands
Somatic NS: voluntary control of skeletal muscles
Autonomic NS (ANS): involuntary control
Sympathetic: stress, danger, exercise
Parasympathetic: rest, calm, digestion
Enteric: gut function (sometimes included
Connective Tissue Coverings
Endoneurium: surrounds each individual axon
Perineurium: wraps groups of axons (fascicles)
Epineurium: wraps entire nerve; protection and strength
Disorders/Diseases
Alzheimer’s: memory loss; neuronal death
Parkinson’s: low dopamine; tremors & stiffness
Multiple Sclerosis (MS): myelin destruction; slow impulses
Epilepsy: uncontrolled electrical activity
Stroke: lack of blood to brain; cell death
Meningitis: inflammation of meninges
Peripheral Neuropathy: nerve damage; numbness/tingling
Major parts and functions of the spinal cord
Functions: sends signals to/from brain; controls reflexes
Gray matter: neuron cell bodies; integration
White matter: myelinated axons; communication pathways
Ascending tracts: sensory info to brain
Descending tracts: motor commands from brain
Central canal: contains cerebrospinal fluid (CSF)
Segmented regions: cervical, thoracic, lumbar, sacral
Neurotransmitters
Acetylcholine (ACh): skeletal muscle movement; parasympathetic
Norepinephrine (NE): sympathetic responses; alertness
Dopamine: reward, movement; linked to addiction & Parkinson’s
Serotonin: mood, sleep, appetite
GABA: main inhibitory; calming
Glutamate: main excitatory; learning & memory
Endorphins: natural painkillers
Action potential & the Nerve Impulse
Resting State
Neuron at –70 mV
More Na⁺ outside, more K⁺ inside
Depolarization
Sodium channels open
Na⁺ rushes in
Inside becomes positive
Repolarization
K⁺ channels open
K⁺ leaves the cell
Inside becomes negative again
Hyperpolarization
K⁺ overshoots; membrane too negative
Return to Resting
Sodium–potassium pump restores balance
Propagation
Impulse travels down axon
Saltatory conduction on myelinated axons = MUCH faster