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Chapter 44 - Osmoregulation

Osmoconformers vs. Osmoregulators

- Osmoconformers: Maintain internal osmolarity equal to their environment (e.g., marine invertebrates).

- Osmoregulators: Actively regulate internal osmolarity regardless of environment (e.g., freshwater fish, terrestrial animals).

Saltwater vs. Freshwater Osmoregulation

- Saltwater Fish: Lose water, drink seawater, excrete excess salts via gills and kidneys.

- Freshwater Fish: Gain water, excrete dilute urine, actively absorb salts through gills.

Kidney Gross Anatomy

- Renal Cortex: Outer layer, contains glomeruli.

- Renal Medulla: Inner layer, contains loops of Henle and collecting ducts.

- Renal Pelvis: Collects urine before transport to ureter.

Nitrogenous Waste Removal Strategies in Land Animals

- Ammonia (fish, amphibians): Requires high water availability.

- Urea (mammals, amphibians): Less toxic, requires energy.

- Uric Acid (birds, reptiles): Insoluble, conserves water.

Filtration, Reabsorption, Secretion, Excretion

- Filtration: Blood pressure forces fluid into nephron.

- Reabsorption: Essential solutes/water reabsorbed into blood.

- Secretion: Additional waste actively added to filtrate.

- Excretion: Processed urine leaves body.

Nephron Structure and Function

- Bowman’s Capsule: Encases glomerulus, filtration site.

- Proximal Tubule: Reabsorption of water, ions, nutrients.

- Loop of Henle: Descending limb (water reabsorption), ascending limb (salt reabsorption).

- Distal Tubule: Regulates pH, electrolyte balance.

- Collecting Duct: Final urine concentration.

Blood Pressure Regulation by Kidney

- Renin-Angiotensin-Aldosterone System (RAAS):

- Renin (kidney) activates Angiotensin → vasoconstriction.

- Aldosterone (adrenal) increases sodium/water retention.

- Antidiuretic Hormone (ADH): Increases water reabsorption in collecting ducts.

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Chapter 45 - Endocrine System

Types of Signaling

- Autocrine: Cell signals itself.

- Paracrine: Local signaling between nearby cells.

- Hormonal (Endocrine): Hormones travel through blood to distant targets.

What is a Hormone?

- Chemical messenger transported via blood, binds receptors to trigger responses.

Hormones vs. Neuron Signaling

- Hormones: Slow, long-lasting, widespread.

- Neurons: Fast, short-lived, targeted.

Water-Soluble vs. Lipid-Soluble Hormones

- Water-Soluble: Bind extracellular receptors (e.g., peptides, amines).

- Lipid-Soluble: Cross membrane, bind intracellular receptors (e.g., steroids).

G Protein-Coupled Receptors (GPCRs)

- Key in hormone signaling, activate second messengers (e.g., cAMP).

Endocrine Organs & Functions

- Hypothalamus: Regulates pituitary.

- Pituitary: Releases growth hormone, oxytocin, ADH.

- Thyroid: Controls metabolism (T3, T4).

- Parathyroid: Regulates calcium (PTH).

- Thymus: Immune function (T-cell development).

- Pancreas: Blood sugar control (insulin, glucagon).

- Kidneys: Erythropoietin (red blood cells), renin.

- Adrenal Glands: Cortisol (stress), aldosterone, epinephrine.

- Gonads: Testosterone, estrogen, progesterone.

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Chapter 48 - Nervous System

Afferent vs. Efferent Signaling

- Afferent: Sensory input to CNS.

- Efferent: Motor commands from CNS.

Neuron Structure

- Dendrites, soma, axon, myelin sheath, synapse.

Action Potential & Ion Flow

- Depolarization: Na+ in.

- Repolarization: K+ out.

- Hyperpolarization: Excess K+ efflux.

Ion Channels & Pumps

- Sodium-Potassium Pump: Restores resting potential.

- Voltage-Gated Channels: Open/close during action potential.

Continuous vs. Saltatory Conduction

- Continuous: Unmyelinated, slow.

- Saltatory: Myelinated, fast (Nodes of Ranvier).

Schwann Cells

- Form myelin in PNS.

Refractory Period

- Prevents back-propagation of signals.

Synaptic Signaling

- Neurotransmitters cross synaptic cleft to receptors.

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Chapter 49 - Central Nervous System

CNS & Nervous System Organization

- Brain, spinal cord, PNS, autonomic (sympathetic/parasympathetic) system.

CNS Cell Functions

- Neurons, glial cells (astrocytes, oligodendrocytes, microglia, ependymal cells).

Nervous System in Other Animals

- Cnidarians: Nerve net.

- Echinoderms: Nerve ring.

- Flatworms: Simple brain.

- Arthropods: Ventral nerve cord.

- Mollusks: Varies (cephalopods have complex brains).

Reflexes

- Involuntary responses via spinal cord pathways.

Brain Areas

- Cerebrum, cerebellum, brainstem, limbic system.

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Chapter 50 - Sensation & Motor Mechanisms

Perception of Sensation

- Stimulus → Sensory receptor → CNS interpretation.

Types of Sensory Receptors

- Pressure (Mechanoreceptors): Touch, vibration.

- Pain (Nociceptors): Injury response.

- Thermoreceptors: Temperature detection.

- Electromagnetic: Light, magnetic fields.

- Chemoreceptors: Taste, smell.

Special Senses

- Hearing: Cochlea, hair cells.

- Equilibrium: Vestibular system, semicircular canals.

- Vision: Retina, photoreceptors (rods: low light, cones: color).

- Taste: Taste buds (sweet, salty, sour, bitter, umami).

- Smell: Olfactory receptors in nasal cavity.

Skeletal Muscle Contraction

- Actin, myosin interaction via ATP.

- Role of calcium and troponin/tropomyosin.

- Neuromuscular junction signaling.