Animal Form and Function II: Endocrine, Reproductive, Nervous, Sensory, and Muscular Systems

Endocrine System

Major Endocrine Glands and Their Hormones

• Hypothalamus: Produces releasing and inhibiting hormones that regulate the pituitary gland.

• Pituitary Gland:

  • Anterior Pituitary: Secretes growth hormone (GH), prolactin (PRL), follicle-stimulating hormone (FSH), luteinizing hormone (LH), thyroid-stimulating hormone (TSH), and adrenocorticotropic hormone (ACTH).

  • Posterior Pituitary: Releases oxytocin and antidiuretic hormone (ADH).

• Thyroid Gland: Secretes thyroxine (T4), triiodothyronine (T3), and calcitonin.

• Parathyroid Glands: Secrete parathyroid hormone (PTH).

• Adrenal Glands:

  • Adrenal Cortex: Produces corticosteroids (cortisol, aldosterone).

  • Adrenal Medulla: Produces epinephrine and norepinephrine.

• Pancreas: Secretes insulin and glucagon.

• Gonads (Testes and Ovaries): Produce sex hormones (testosterone, estrogen, progesterone).

Hormonal Effects on Target Cells

• Hormones act as chemical messengers, binding to specific receptors on target cells to regulate metabolism, growth, reproduction, and homeostasis.

• Effects can be rapid (e.g., epinephrine) or long-term (e.g., growth hormone).

Hypothalamus and Pituitary Gland

• The hypothalamus links the nervous and endocrine systems, controlling the pituitary gland via releasing/inhibiting hormones.

• The pituitary gland is the "master gland," regulating other endocrine glands.

Posterior vs. Anterior Pituitary Hormones

• Posterior Pituitary: Stores and releases hormones made by the hypothalamus (oxytocin, ADH).

• Anterior Pituitary: Synthesizes and secretes its own hormones in response to hypothalamic signals.

Reproductive System

Asexual vs. Sexual Reproduction

• Asexual Reproduction: Offspring arise from a single parent; common in stable environments (e.g., budding in hydra).

• Sexual Reproduction: Involves fusion of gametes; increases genetic diversity, favored in changing environments.

Fertilization Types

• Internal Fertilization: Sperm fertilizes egg inside the body; common in terrestrial animals.

• External Fertilization: Eggs fertilized outside the body; common in aquatic environments.

Male Reproductive Anatomy and Sperm Pathway

• Structures: Testes (sperm production), epididymis (sperm maturation), vas deferens, seminal vesicles, prostate gland, urethra, penis.

• Pathway: Seminiferous tubules → epididymis → vas deferens → ejaculatory duct → urethra → exit body.

Female Reproductive Anatomy

• Structures: Ovaries (egg production), oviducts (fallopian tubes), uterus, cervix, vagina.

Spermatogenesis vs. Oogenesis

• Spermatogenesis: Continuous production of sperm; four functional sperm per meiosis.

• Oogenesis: Cyclical; one functional ovum and polar bodies per meiosis.

Ovarian and Menstrual Cycles

• Ovarian Cycle: Follicular phase (FSH, LH), ovulation (LH surge), luteal phase (progesterone).

• Menstrual Cycle: Menstrual flow, proliferative phase (estrogen), secretory phase (progesterone).

Conception to Birth

• Conception: Occurs in the oviduct.

• Pregnancy Trimesters: First (organogenesis), second (growth), third (preparation for birth).

• Labor: Initiated by hormonal changes (oxytocin, prostaglandins).

Contraceptive Methods

• Barrier methods, hormonal methods, intrauterine devices, sterilization, behavioral methods.

Embryonic Development and Germ Layers

• Stages: Zygote → cleavage → blastula → gastrula.

• Germ Layers: Ectoderm (nervous system, skin), mesoderm (muscle, bone), endoderm (digestive tract).

• Extraembryonic Membranes: Amnion (protection), chorion (gas exchange), yolk sac (nutrients), allantois (waste).

Nervous System

Neuron Structure and Function

• Parts: Dendrites (input), cell body (integration), axon (output), axon terminals (signal transmission).

Types of Neurons

• Sensory Neurons: Transmit sensory information to CNS.

• Interneurons: Integrate information within CNS.

• Motor Neurons: Transmit signals from CNS to effectors (muscles/glands).

Neuronal Pathways

• Simplest: Reflex arcs (e.g., knee-jerk reflex).

• Complex: Multisynaptic pathways involving integration and processing.

Resting and Action Potentials

• Resting Potential: Membrane potential at rest, typically -70 mV; maintained by sodium-potassium pump.

• Action Potential: Rapid change in membrane potential due to Na+ influx and K+ efflux.

• Depolarization: Membrane potential becomes less negative (Na+ in).

• Repolarization: Return to resting potential (K+ out).

• Hyperpolarization: Membrane potential becomes more negative than resting.

Key Equation: Nernst Equation

$E = \frac{RT}{zF} \ln \left( \frac{[\text{ion outside}]}{[\text{ion inside}]} \right)$

Myelin and Conduction

• Myelin: Insulating sheath produced by Schwann cells (PNS) and oligodendrocytes (CNS); increases conduction speed via saltatory conduction.

Synapses and Neurotransmitters

• Chemical Synapses: Use neurotransmitters (e.g., acetylcholine, dopamine).

• Electrical Synapses: Direct cytoplasmic connections (gap junctions).

Central vs. Peripheral Nervous System

• CNS: Brain and spinal cord; integration and processing.

• PNS: Nerves outside CNS; subdivided into somatic (voluntary) and autonomic (involuntary) systems.

Autonomic Nervous System: Sympathetic vs. Parasympathetic

Feature	Sympathetic	Parasympathetic
Function	"Fight or flight"	"Rest and digest"
Neurotransmitter	Norepinephrine	Acetylcholine
Effect on Heart Rate	Increases	Decreases
Pupil	Dilates	Constricts

Major Brain Structures and Functions

• Cerebrum: Higher cognitive functions.

• Cerebellum: Coordination and balance.

• Brainstem: Basic life functions (breathing, heart rate).

• Hypothalamus: Homeostasis, endocrine regulation.

Sensory Systems

Functions of Sensory Pathways

• Reception: Detecting stimuli.

• Transduction: Converting stimulus to electrical signal.

• Transmission: Sending signal to CNS.

• Perception: Interpretation by the brain.

Types of Sensory Receptors

• Mechanoreceptors: Touch, pressure (e.g., Pacinian corpuscles).

• Photoreceptors: Light (e.g., rods and cones in eye).

• Chemoreceptors: Chemicals (e.g., taste buds, olfactory cells).

• Thermoreceptors: Temperature changes.

• Nociceptors: Pain.

Statocysts and Lateral Line Organs

• Statocysts: Balance organs in invertebrates; detect gravity and motion.

• Lateral Line Organs: Found in fish; detect water movement and vibrations.

Human Ear Structure and Hearing

• Structures: Outer ear (pinna, auditory canal), middle ear (ossicles), inner ear (cochlea, semicircular canals).

• Hearing Sequence: Sound waves → tympanic membrane → ossicles → oval window → cochlea → hair cells → auditory nerve.

Light Detecting Organs

• Range from simple eyespots (planarians) to complex camera-type eyes (vertebrates).

Vertebrate Eye Structure and Visual Pathway

• Structures: Cornea, lens, retina, optic nerve.

• Pathway: Light → cornea → lens → retina (photoreceptors) → optic nerve → visual cortex.

Muscular and Skeletal Systems

Skeletal Muscle Structure

• Composed of muscle fibers containing myofibrils (actin and myosin filaments).

Sliding Filament Model and Calcium Role

• Muscle contraction occurs as myosin heads "walk" along actin filaments, shortening the sarcomere.

• Calcium ions bind to troponin, exposing binding sites on actin.

Types of Skeletons

• Hydrostatic: Fluid-filled cavity (e.g., earthworms).

• Exoskeleton: External skeleton (e.g., arthropods).

• Endoskeleton: Internal skeleton (e.g., vertebrates).

Types of Joints and Functions

• Ball-and-socket: Multidirectional movement (shoulder, hip).

• Hinge: Movement in one plane (elbow, knee).

• Pivotal: Rotation (neck).

Additional info: Where details were not specified, standard textbook knowledge was used to expand and clarify topics for completeness.