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Nervous
Neurons
Dendrite: Receive incoming signals, post synaptic Soma: integrates signals, decides strength ok Axon: conducts impulses (hillock) Myelin Sheath: protective layer, increases signal speed Nodes of Ranvier: gaps between myelin segs, saltatory conduction (action jumping) thru ion channels Terminals : contains vesicles, presynaptic membrane, Glia
- Astrocytes : star shaped, blood-brain barrier, endothelial cells,
- Myelinating
- Schwann : Myelinates PNS neurons, immune cells PNS
- Oligiodendrites : Myelinates CNS, repair damaged nerves
- Microglia : immune cells CNS
- Ependymal : make and circulate CSF, line spine and ventricular
Action Potential
- Threshold: Membrane voltage ~55mV to trigger action potential
- Stimulus: Causes
- Depolarization
- Climax
- Repolarization
- Hyperpolarization
- Resting: Na outside K inside, membrane more permeable to K
Neurotransmitters functions
- *Categories depend on how the neurotransmitter is being used
- Excitatory: gradient less neg
- Inhibitory : more neg
- Modulatory: slower, regulate populations of neurons, impact other neurotransmitters
- Major Neurotransmitters and primary functions
- Glutamate:Excitatory, memory, neural development
- Gaba: Inhibitory, regulates firing, mood, sleep, stress, etc.
- Glycine: Inhibitory in Spinal/Stem, motor reflex reg, protein synthesis, co-agonist NMDA receptors
- Dopamine: hormone, reward system, motivation, nigrostriatal pathway (motor)
- Serotonin: mood regulation, sleep cycle, appetite, cognition, pain, sexual
- Norepinephrine: noradrenaline, arousal, fight/flight, cardiovascular,
- Epinephrine: adrenaline, fight/flight, β 2 adrenergic receptors alpha
- Adrenergic receptors:
- ⍺ 1 : NE, vasoconstriction, inc BP
- ⍺ 2 : NE, inhibitory, regulate SNS, prevent tachycardia and hypertension
- β 1 : EP, heart rate, card output inc
- β 2 : EP, Bronchodilation (bronchi=lungs)
- Acetylcholine: enable muscle contraction (neuromuscular junction), Ca+^ receptors, ANS function, sleep, immune, cognitive,
- Histamine: immune+inflammatory response, arousal, cognitive function,
- Endorphins: pain inhibition, reward, emotions,
- Oxytocin: social behavior, emotion, neural development
Central nervous system (CNS)
Forebrain (Prosencephalon)
Hindbrain
Metecephalon
Myelencephalon
- Medulla Oblongata
- Ventricles
Spinal Cord
Other
- Brain Stem (Midbrain + part of hindbrain)
Peripheral Nervous System (PNS)
Somatic
12 cranial nerve pairs,31 spinal nerve pairs Neuromuscular Junction: Afferent Sensory Neurons: Transmit signals from sensory receptors to CNS. Efferent Motor Neurons: Transmit signals from CNS to muscles/glands.
Cranial Nerves (12 pairs):
- Sensory: Olfactory (smell), Optic (vision), Vestibulocochlear (hearing/balance
- Motor: Oculomotor, Trochlear, Abducens, Spinal Accessory, Hypoglossal
- Mixed: Trigeminal (face sensation + chewing), Facial (expression + taste), Glossopharyngeal, Vagus (visceral sensation + motor) Spinal Nerves (31 pairs):
- Cervical (C1–C8): neck, shoulders, arms, diaphragm
- Thoracic (T1–T12): trunk, intercostal muscles, some abdominal muscles
- Lumbar (L1–L5): lower back, legs
- Alzheimer’s
- Parkinson’s
- Huntington’s
- ALS
- Infections:
- Meningitis, encephalitis PNS
- Neuropathy
- GBS
- CIDP Stroke: brain damage from blocked/burst vessel (clot or bleed) treated with clot removal/meds/rehab; MS: autoimmune CNS demyelination treated with immunosuppressants; Alzheimer’s: progressive memory loss from neuron degeneration treated with symptom-slowing meds; Parkinson’s: movement disorder from dopamine neuron loss treated with dopamine-boosting drugs; Huntington’s: inherited movement/cognitive decline treated symptomatically; ALS: motor neuron degeneration causing paralysis treated with supportive care; Meningitis: inflamed meninges from bacterial/viral infection treated with antibiotics/antivirals; Encephalitis: brain inflammation usually viral treated with antivirals/supportive care; Neuropathy: peripheral nerve damage (diabetes, toxins, injury) treated by addressing cause and pain control; GBS: acute autoimmune ascending paralysis post-infection treated with IVIG/plasmapheresis; CIDP: chronic autoimmune peripheral demyelination treated with steroids or IVIG.
Sense Organs
Eye
- 70% of all sensory receptors
- Adult eye diameter 1 inch
- Accessory Structures - Eyebrows - Protect from perspiration || shade sunlight || supraorbital area (SN - Supercilia/um) - Eyelids - Anterior protection || superior + inferior* eyelids meet at medial and lateral **canthi || Lacrimal Caruncle - sebaceous + sweat glands, secretion of rheum as cleaning mech || Tarsal plates structural support || Levator Palpabrae superioris - lifts top eyelid, Orbicularis Oculi brings eyelids together || activation to blink 3-7 secs, prevent dehydration and flinching || Eyelashes innervated, touches = blinks || Tarsal/Meimbomian glands , tarsal plates, produce Meibum, lubricating agent || (SN - Palpebra+e) - upper + lower - Canthus → pockets of the eye, medial = inner - Conjunctiva - membrane lines inside of eyelids and sclera || produces lubricating/hydrating mucus - Lacrimal Apparatus - Lacrimal gland + ducts || Lacrimal glands produce tears thru excretory ducts || blinking → medial commissure, lacrimal punctum → canaliculi → drains lacrimal secretion → nasal cavity → lacrimal sac → nasolacrimal duct → empty into nasal cavity || tears lubricate and cleanses surface of eye w antibodies & lysozyme - *spreads and into - ** medial canthi area - ***Tear ducts, next to the caruncle, inner edge of eyelid, superior and inferior - Extrinsic Eye Muscles - Lateral Rectus - lateral, Abducens VI - Medial Rectus - medial, Oculomotor III - Superior Rectus - rotate medial, elevate, Oculomotor III - Inferior Rectus - rotate medial, depress, Oculomotor III - Inferior Oblique - rotate lateral, elevate, Oculomotor III - Superior Oblique - rotate lateral, depress, Trochlear IV
- Transparent lens, focuses on Retina
- Signal Pathway
- Photoreceptors* → Bipolar → Ganglion → Optic Nerve → LGN* → Visual Cortex - *light travels to the back of the retina, then travels in the other direction towards ganglion cells - Photoreceptors:
- Rhodopsin : 11-cis-retinal → all-trans-retinal, converts light into signals
- Rods: high light sensitive, low acuity, monochromatic, night vision, peripheral, rhodopsin
- Cones: less light sensitive, high acuity, RGB (LoMedSho), photopsin
- Horizontal Cells - combines info from multiple photoreceptors || Primary Lateral inhibition - feedback to neighboring cells || sharpens image by suppressing an enhancing dim/bright areas exaggeration
- Bipolar Cells - contrast light and dark || Intermediaries
- ON cells - depolarize (activate) in light || hyperpolarize (inhibit) in dark || respond to increase in illumination, light on dark background
- OFF cells - opposite of ON cells, respond to lack of light, dark on light background, contrast, edges
- Amacrine Cells - Link bipolar and ganglion, complex visuals, modulate bipolar cell signals, compensate for loss of detail || excite neurons thru neurotransmitters
- Ganglion Cells - Neurons - form optic nerve w/ long bundled axons || Form signals thru action potentials || lead to LGN*
- Lateral Geniculate Nucleus (Thalamus) - Relay station for visual info
- Visual Cortex - processing and interpreting visual information
- Ventral stream - what, towards temporal lobe
- Dorsal stream - where/how to interact, parietal lobe,
- Rhodopsin Cycle: pigment rhodopsin captures light, signals, regenerates - Rhodopsin contains 11-cis-retinol, absorbs photon, → all-trans-retinol (prevent apoptosis) - Isomerization to reach transducin - Bathorhodopsin, Lumirhodopsin, Metarhodopsin I, Metarhodopsin II (active form)
- Conformational || Enzyme (can activate hundreds of transducin) || Signal amplification Diseases:
- Myopia: light focuses in front of retina, blurred distance vision (nearsighted)
- Hyperopia: light focuses behind retina, difficulty with near vision (farsighted)
- Presbyopia: Age-related, loss of accommodation - decreased lens elasticity near vision
- Astigmatism: Unequal corneal/lens curvature, distorted/blurred vision
- Cataracts: Progressive clouding of the eye’s lens painless, gradual loss of vision.
- Glaucoma: Optic nerve damage, increased intraocular pressure, irreversible visual field loss.
- Conjunctivitis: Inflammation of conjunctiva causing redness, discharge, irritation, tearing.
- Neuritis (Optic Neuritis): Inflammation of ON causing vision loss and pain with eye movement.
- Color Blindness: Defective color perception due to cone photoreceptor dysfunction, usually affecting red–green discrimination. - Strabismus: cross eyed, genetics, nerve damage, stroke
- Diseases - Otitis Media : infection, inflammation of middle ear, Eustachian tube blockage - Otitis Externa : “...”of outer ear canal, moisture trapped in canal breeds bacteria - Conductive loss : sound improperly travels thru outer ear to middle, faint sounds, damaged eardrum - Sensorineural loss: damage to cochlea or auditory nerve, tinnitus, hearing loss, aging, noise, infection - Meniere’s: inner ear disorder - excess/buildup fluid, vertigo, tinnitus, hearing loss,
Nose
- Nasal Cavity - Nasal Conchae (Turbinates): Curved bony, increase surface area, warm and humidify air. - Mucous Membrane: produces mucus to trap dust and microbes. - Olfactory Epithelium: Tissue at top of nasal cavity, small receptors. - Nasal Meatuses: Passages beneath turbinates help direct airflow. - Sinuses - Frontal Sinus: Air-filled cavity above eyes, helps lighten the skull and produce mucus. - Maxillary Sinus: Largest sinus, cheekbones; drains mucus into the nose. - Ethmoid Sinus: Small air cells between the eyes that help filter air. - Sphenoid Sinus: Located behind the nasal cavity; helps with resonance of voice. - Process of Smelling - Air enters through the nostrils and passes into the nasal cavity. - Mucus in the olfactory epithelium traps odor molecules. - Odor molecules bind to receptors on olfactory hair cells. - Olfactory nerve fibers transmit signals to the brain. - The brain interprets these signals as specific smells. - Diseases - Rhinitis: Inflammation of nasal lining - Sinuitis: infection/inflammation of sinuses, fever, headache, - Polyps: soft growths on nasal lining - Deviated Septum, displaced septum, difficulty breathing (trauma) - Epistaxis (nosebleed): bleeding, broken blood vessel in lining - Anosmia: loss of smell, viral infections,
● Definition: Muscles that move the tongue in different directions (out, in, side to side).
- Intrinsic Muscles ● Definition: Muscles inside the tongue that change its shape for speech and swallowing.
Endocrine System
Hormones: chemical messengers → blood; act only on cells w/ correct receptors; slow, long-lasting effects; mostly negative feedback (self-regulating) MAIN GLANDS & HORMONES Hypothalamus: produces ADH, oxytocin, RH/IH; links nervous ↔ endocrine; controls pituitary; maintains homeostasis Pituitary (“master”): controls other glands Ant (front lobe): GH (growth), TSH (stimulates thyroid), ACTH (stimulates adrenal cortex), FSH (egg/sperm), LH (ovulation/testosterone), PRL (milk), MSH (skin pigment) Post (back lobe): ADH (kidneys save water), oxytocin (labor, milk release) Pineal: melatonin → sleep/wake cycle Thyroid: T₃/T₄ → ↑ metabolism, energy, heat; needs iodine; calcitonin → ↓ blood Ca²⁺ Parathyroid: PTH → ↑ blood Ca²⁺ (opposite of calcitonin)
Thymus: thymosins → T-cell immune development (shrinks after childhood) Pancreas (islets): insulin ↓ blood glucose, glucagon ↑ blood glucose → sugar balance Adrenal Glands: stress & emergency response Cortex: cortisol (long-term stress/metabolism), aldosterone (salt & water balance), androgens (sex traits) Medulla: epinephrine, norepinephrine → fight-or-flight Heart: ANP → ↓ blood volume & BP Kidneys: EPO (makes RBCs), calcitriol (calcium balance), renin (raises BP) Digestive Tract: multiple hormones → control digestion Gonads: reproduction Ovaries: estrogen, progesterone, inhibin → female traits, menstrual cycle Testes : testosterone, inhibin → male traits, sperm production
ECG:
EEG:
