Comprehensive Study Guide for 11th Grade Biology

Organization of the Human Body

• General Concepts: Cells and tissues form organs, and organs group into systems to perform main functions: relation, nutrition, and reproduction. Organs do not function in isolation but work in correlation. Internal organs are commonly referred to as viscera.

• Body Segments:     * Head: Formed by the cranial part (neurocranium) and facial part (viscerocranium).     * Neck: Connects the head to the trunk; contains somatic elements (muscles, bones, joints) and viscera (larynx, trachea, esophagus, thyroid, parathyroids).     * Trunk: Comprises the thorax, abdomen, and pelvis. These contain cavities (thoracic, abdominal, pelvic) housing viscera. The diaphragm muscle separates the thoracic and abdominal cavities. The pelvic cavity is limited inferiorly by the perineal diaphragm.     * Limbs:         * Superior Limbs: Connected by the scapular girdle; segments are the arm, forearm, and hand.         * Inferior Limbs: Connected by the pelvic girdle; segments are the thigh, leg, and foot.

• Anatomic Orientation:     * Axes: Tridimensional and intersect at right angles.         * Longitudinal Axis: Vertical, has two poles: superior (cranial) and inferior (caudal).         * Sagittal (Anteroposterior) Axis: Axis of thickness, has anterior and posterior poles.         * Transversal Axis: Axis of width, horizontal, has left and right poles.     * Planes:         * Sagittal Plane: Passes through the longitudinal and sagittal axes. The medio-sagittal plane divides the body into two symmetrical halves (bilateral symmetry).         * Frontal Plane: Parallel to the forehead; passes through the longitudinal and transversal axes. Divides the body into anterior (ventral) and posterior (dorsal) parts.         * Transversal (Horizontal) Plane: Passes through the sagittal and transversal axes. Divides the body into superior (cranial) and inferior (caudal) parts. It is known as the plane of metamerism.

• Anatomical Nomenclature:     * Proximal: Closer to girdles.     * Distal: Farther from girdles.     * Volar/Palmar: For hand palm formations.     * Plantar: For the sole of the foot; Dorsal for the upper surface of the foot.     * Superficial and Profound: Indicate the degree of closeness to the body surface.

The Cell and Tissues

• The Cell: The basic morphofunctional and genetic unit of living matter.

• Size and Shape: Initially globular, but can become fusiform, stellate, cubic, or cylindrical. Red blood cells (hematocrit) are $7.5\,\mu$, the ovum is $150–200\,\mu$, and striated muscle fibers are $5–15\,cm$. Average size is $20–30\,\mu$.

• Structure:     * Cell Membrane (Plasmalemma): Phospholipid bilayer with proteins (Fluid Mosaic Model). Hydrophilic portions face outward, hydrophobic portions point inward to restrict water-soluble molecules and ions. Contains carbohydrates (glycoproteins/glycolipids) with strong negative charges on the outer face.     * Cytoplasm: A colloidal system (water dispersion medium, colloidal micelles as the dispersed phase).         * Hialoplasm: Unstructured part.         * Common Organelles:             * Endoplasmic Reticulum (ER): Intracitoplasmic circulatory system. Smooth ER (metabolism of glycogen) and Rough ER (Ergastoplasm, contains ribosomes for protein synthesis).             * Ribosomes (Palade's corpuscles): Rich in ribonucleoproteins ($150–250\,\text{\AA}$); site of protein synthesis.             * Golgi Apparatus (Dictyosomes): Near the nucleus; involved in substance excretion.             * Mitochondria: Trilaminar wall (lipoprotein); inner membrane folds into mitochondrial cristae containing enzymes for oxidative phosphorylation (ATP synthesis).             * Lysosomes: Spherical; contain hydrolytic enzymes for digestion.             * Centrosome: Two cylindrical centrioles; involved in cell division (absent in neurons).         * Specific Organelles: Myofibrils (muscles), Neurofibrils (neurons), Nissl bodies (tigroid bodies in neurons).     * Nucleus: Coordinates fundamental biological processes. Most cells are mononucleated, but hepatocytes can be binucleated, muscle fibers polynucleated, and mature RBCs are anucleated. Consists of a porous double nuclear membrane, carioplasm (chromatin granules forming chromosomes: DNA, RNA, histon/non-histone proteins, ions like $Ca^{2+}$ and $Mg^{2+}$), and nucleoli.

• Cell Membrane Transport:     * Passive Transport (No energy required):         * Diffusion: Movement of molecules (gases like $O_2$, steroids, $CO_2$, urea) down a concentration gradient.         * Osmosis: Diffusion of solvent (water) across a semipermeable membrane from high solvent concentration to low. Osmotic pressure is proportional to the number of dissolved particles.         * Facilitated Diffusion: Uses transport proteins for large polar molecules (glucose) down a gradient.     * Active Transport (Requires ATP):         * Primary Active Transport: Pumps requiring direct ATP hydrolysis (e.g., $Na^+/K^+$ pump).         * Secondary Active Transport (Cotransport): Energy obtained via another energy transfer.     * Vesicular Transport: Endocytosis (phagocytosis and pinocytosis) and Exocytosis.

• Membrane Potential:     * Resting Potential: Average value of $-65\,mV$ to $-85\,mV$ (close to $K^+$ equilibrium). Maintained by the $Na^+/K^+$ pump (expels $3\,Na^+$ for every $2\,K^+$ brought in).     * Action Potential: Temporary change due to ion flow through voltage-dependent channels.         * Phases: Threshold (critical level), Ascending slope (depolarization via $Na^+$ influx), Descending slope (repolarization via $K^+$ efflux).         * Refractory Periods: Absolute (cannot fire again) and Relative (needs stronger stimulus).

• Tissues Classification:     * Epithelial: Covering (simple, pseudostratified, or pluristratified), Glandular (endocrine, exocrine, or mixed), Sensory.     * Connective: Soft (lax, reticulated, adipose, fibrous, elastic), Semi-hard (cartilaginous: hyaline, elastic, fibrous), Hard (osseous: compact/haversian or spongy/trabecular), Fluid (blood).     * Muscular: Striated (skeletal), Smooth (visceral/multi-unit), Cardiac (striated cardiac).     * Nervous: Neuron (nerve cell) and Neuroglia (glial cell).

The Nervous System

• General Organization: Regulates muscles and glands. Separated into Somatic SN (skeletal muscles) and Autonomic/Vegetative SN (visceral muscles/glands).

• Neuron Physiology:     * Structure: Perikaryon (body), dendrites (cellulipetal), and axon (cellulifug). Axons end in terminal buttons with neurotransmitter vesicles.     * Neuron Types: Unipolar (retina), Pseudounipolar (spinal ganglion), Bipolar (ear, nose, retina), Multipolar (cerebral/cerebellar cortex).     * Neuroglia: 10 times more numerous than neurons. Do not contain neurofibrils or Nissl bodies but divide intensely. Types: Schwann cells, astrocytes, oligodendroglia, microglia.     * Sheaths:         * Myelin Sheath: Electrical insulator. Produced by Schwann cells (PNS) or oligodendrocyte (CNS). Found in axons >2\,\mu.         * Schwann Sheath: Outside myelin in PNS.         * Henle Sheath: Separates Schwann cell from surrounding connective tissue.     * Conduction: Saltatory in myelinated fibers ($100\,m/s$) vs. continuous in unmyelinated fibers ($10\,m/s$).

• The Synapse: Connection between a neuron and another cell (neuron, muscle, or gland).     * Types: Chemical (uses mediators like Acetylcholine) and Electrical (bidirectional; found in myocardium, smooth muscle).     * Mechanism: Presynaptic terminal $\rightarrow$ Synaptic cleft $\rightarrow$ Postsynaptic receptors. Results in Excitatory Postsynaptic Potential (EPSP).

• The Reflex: The fundamental mechanism of SN function.     * Reflex Arc Components: Receptor (converts energy to impulse), Afferent path (sensory neurons), Reflex centers (CNS structures), Efferent path (motor axons), Effector (muscle or gland).

• Spinal Cord (Medulla Spinalis):     * Located in the vertebral canal from $C_1$ down to $L_2$, ending in the medullary cone and filum terminale. Below $L_2$, nerves form the cauda equina.     * Meninges: Dura mater (outer, fibrous), Arachnoid (middle, separated from pia by CSF), Pia mater (inner, vascular, nutritive).     * Internal Structure: Grey matter inside ("H" shape), White matter outside (funiculi/columns).         * Grey Matter: Anterior horns (somatomotor), Posterior horns (sensory), Lateral horns (autonomic sympathetic).         * White Matter: Ascending (sensory: spinothalamic, spinocerebellar, gracilis/Goll, cuneatus/Burdach), Descending (motor: Pyramidal/Corticospinal for voluntary movement; Extrapyramidal for involuntary/automated movement), and association paths.

• Spinal Nerves: $31$ pairs (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal). Roots: Anterior (motor) and Posterior (sensory, contains spinal ganglion). Branches: Ventral (form plexuses), Dorsal, Meningeal, Communicating (white and grey).

• Brain (Encephalon):     * Brainstem (Bulb, Pons, Midbrain): Origin of 10 cranial nerve pairs; centers for vital reflexes (heart, breathing).     * Cerebellum: Posterior fossa; coordinates tone, posture, and balance. Extirpation causes asthenia, astasia, atonia.     * Diencephalon: Thalamus (sensory relay), Metathalamus (visual/auditory relay), Epithalamus (epiphysis), Hypothalamus (superior autonomic integration, metabolism, behavior).     * Cerebral Hemispheres: Features lobes (Frontal, Parietal, Temporal, Occipital). Grey matter forms the cortex and basal ganglia (corpus striatum).         * Paleocortex: Limbic system; emotional behavior and smell.         * Neocortex: Basis of learning, thinking, memory (Higher Nervous Activity - ANS).

• Cranial Nerves Summary:     * I (Olfactory): Sensory.     * II (Optic): Sensory.     * III (Oculomotor), IV (Trochlear), VI (Abducens): Motor for eye movement. III has parasympathetic fibers for pupil.     * V (Trigeminal): Mixed; face sensation, mastication.     * VII (Facial): Mixed; mimicry, taste (ant. 2/3 tongue), parasympathetic for glands.     * VIII (Vestibulocochlear): Sensory; hearing and balance.     * IX (Glossopharyngeal): Mixed; taste (post. 1/3 tongue), pharynx motor, parasympathetic for parotids.     * X (Vagus): Mixed; taste (tongue base), larynx/pharynx motor, parasympathetic for thorax/abdomen viscera.     * XI (Accessory): Motor; neck muscles.     * XII (Hypoglossal): Motor; tongue movement.

• Autonomic Nervous System (ANS):     * Sympathetic: Fight or flight; preganglionic fibers in lateral horns ($T_1–L_2$); uses Noradrenaline at target.     * Parasympathetic: Rest and digest; preganglionic fibers in brainstem and sacral cord ($S_2–S_4$); uses Acetylcholine.     * Antagonistic Effects: Sympathetic dilates pupils (midriasis), increases heart rate, decreases GI motility. Parasympathetic constricts pupils (miosis), decreases heart rate, increases GI motility.

The Analysers

• General Structure: Peripheric segment (receptor), Intermediate segment (conduction paths), Central segment (cortical area).

• Cutaneous Analyser (Skin):     * Structure: Epidermis (keratinized epithelium), Dermis (papillary and reticular layers), Hypodermis (adipose tissue).     * Receptors: Free nerve endings (pain/algoreceptors), Merkel disks/Meissner corpuscles (touch), Ruffini (heat/pressure), Krause (cold), Vater-Pacini (vibration).

• Kinesthetic Analyser:     * Monitors body position via proprioceptors in muscles (neuromuscular spindles), tendons (Golgi neurotendinous corpuscles), and joints (Ruffini corpuscles, Vater-Pacini).

• Olfactory Analyser: Chemoreceptors in nasal mucosa (bipolar neurons). Axons form the olfactory tract (I). Projects to the temporal lobe.

• Gustatory Analyser: Chemoreceptors in taste buds (tongue papillae: circumvallate, fungiform, foliate). Four primary tastes: bitter, sour, sweet, salty.

• Visual Analyser:     * Eyeball: Tunics (Sclerotica/Cornea, Choroid/Ciliary body/Iris, Retina) and Refractive media (aqueous humor, lens, vitreous body).     * Retina: Photoreceptors (125 million rods for night vision; 6–7 million cones for day/color vision). Pigments: Rhodopsin and Iodopsins.     * Acommodation: Ciliary muscle contraction for near vision (lens bulges).     * Defects: Myopia (eyeball too long, corrected with divergent lenses), Hypermetropia (eyeball too short, corrected with convergent lenses), Astigmatism (uneven cornea curvature), Presbyopia (loss of lens elasticity with age).

• Acoustico-vestibular Analyser:     * Ear: External, Middle (ossicles: malleus, incus, stapes), and Internal (bony and membranous labyrinth).     * Hearing: Spiral organ of Corti in the cochlea; reacts to sound frequencies ($20–20,000\,Hz$).     * Balance: Maculae (static equilibrium/linear acceleration) and Cristae ampulares (dynamic equilibrium/circular acceleration).

The Endocrine Glands

• Hormones: Specific chemicals acting at a distance.

• Pituitary (Hypophysis):     * Adenohypophysis: Secretes STH (Growth), Prolactin, ACTH (Adrenals), TSH (Thyroid), FSH and LH (Gonads).     * Neurohypophysis: Releases ADH (Vasopressin - increases water reabsorption) and Oxytocin (uterine contraction/milk expulsion).

• Thyroid: Secretes Thyroxine ($T_4$), Triiodothyronine ($T_3$) (increase metabolism), and Calcitonin (lowers blood calcium).

• Parathyroids: Secretes Parathormone (PTH - increases blood calcium, activates osteoclasts).

• Adrenals:     * Cortex: Mineralocorticoids (Aldosterone - sodium retention), Glucocorticoids (Cortisol - stress response/metabolism), Sexosteroids.     * Medulla: Catecholamines (Adrenaline/Noradrenaline - sympathetic mimics).

• Pancreas (Islets of Langerhans): Alpha cells (Glucagon - increases blood sugar), Beta cells (Insulin - decreases blood sugar).

• Dysfunctions: Gigantism/Acromegaly (Excess STH), Diabetes insipidus (Lack of ADH), Basedow-Graves (Hyperthyroidism), Mixedema (Hypothyroidism in adults), Diabetes mellitus (Lack of insulin), Addison's Disease (CSR insufficiency).

Movement and the Skeletal System

• Osteogenesis: Desmal (membrane) and enchondral (cartilage) ossification. Long bones grow in length via growth plates and in thickness via periosteum.

• Skeleton: Cap (22 bones), Trunk (Vertebral column, ribs, sternum), Girdles, and Limbs.     * Bones: Long (humerus, femur), Late/Flat (parietal, scapula), Short (carpals).     * Composition: $20\%$ water, $80\%$ solid (Osein matrix + hydroxyapatite minerals).

• Joints: Sinarthroses (immobile), Amphiarthroses (semi-mobile), Artrodiae (mobile/synovial).

• Muscular System: Skeletal muscles are the active components.     * Contraction: Unit is the sarcomer. Sliding filament theory (actin and myosin).     * Types: Isometric (tension increases, length constant), Isotonic (length changes, tension constant), Auxotonic.     * Summation: Secus (single twitch), Tetanos (summed contractions - incomplete or complete).

Nutrition Functions

• Digestive System:     * Mouth: Mastication (reflex) and Saliva (Amilase breaks starch into maltose).     * Stomach: Chyme formation. Gastric juice contains HCl (activates pepsin) and Pepsin (protein digestion). Lab-ferment (infants).     * Pancreas: Secretes Trypsin/Chymotrypsin (proteins), Lipase (lipids), Amilase (carbs).     * Liver: Bile salts (emulsify lipids, aid absorption).     * Small Intestine: Absorption via villi (glucose/amino acids to portal vein; lipids to lymph as chylomicrons).     * Large Intestine: Water/electrolyte absorption; fecal storage.

• Circulation:     * Blood: Hematocrit ($45\%$ elements, $55\%$ plasma).         * Systems: OAB and Rh. Group 0 (Universal Donor), AB (Universal Recipient).         * Hemostasis: 1. Vasculo-platelet time, 2. Plasmatic time (Coagulation: Fibrinogen $\rightarrow$ Fibrin).     * Heart: $4$ chambers. Cardiac cycle ($0.8\,s$). Properties: Excitability, Automatism, Conductivity, Contractility.     * Vascular: Arteries (high pressure, elastic), Veins (low pressure, valves/muscle pump).

• Respiration:     * Ventilation: Inspiration ($P_{\text{alv}} = -1\,cm\,H_2O$) and Expiration ($P_{\text{alv}} = +1\,cm\,H_2O$).     * Volumes: Tidal volume ($VC = 500\,mL$), Vital Capacity ($CV = VC + VIR + VER \approx 3500\,mL$).     * Gas exchange: $O_2$ binds to hemoglobin (98.5%); $CO_2$ transported mostly as bicarbonate (90%).

• Excretion:     * Nephron: Glomerular filtration ($125\,mL/min = 180\,L/day$).     * Urine Formation: $99\%$ of filtrate is reabsorbed. Reabsorption of water is mandatory in proximal tubule ($80\%$) and facultative in distal/collecting tubules (via ADH).

• Metabolism:     * Intermediate: Catabolism (energy production/ATP) vs. Anabolism (tissue building).     * Energy: Glucose is primary fuel ($4.1\,kcal/g$); Lipids are reserve ($9.3\,kcal/g$).     * Basal Metabolism (MB): Minimum energy for vital functions ($1\,kcal/kg/hour$).     * Vitamins: Liposoluble (A, D, E, K) and Hydrosoluble (C, B complex).

Reproduction and Life Stages

• Physiology:     * Male: Spermatogenesis (via FSH); Testicular secretion (Testosterone via LH).     * Female: Ovarian cycle (28 days). Ovulation (Day 14, triggered by LH peak). Progesterone (maintains pregnancy).

• Health: Conception happens in the fallopian tube. Pregnancy (Gestation) lasts approx. $280$ days.

• Homeostasis: Maintenance of dynamic constants (Temperature, pH, Glycemia) via feedback loops. Integration provided by the Nervous and Endocrine systems.