BIO 123 Exam 3 Study Guide: Hormones, Reproduction, Development, Nervous and Sensory Systems

Ch. 45: Hormones and the Endocrine System

Hormone-Receptor Interactions

Hormones are chemical messengers that regulate physiological processes by binding to specific receptors on target cells, triggering cellular responses.

• Hormone Binding: Hormones bind to receptors either on the cell surface (for water-soluble hormones) or inside the cell (for lipid-soluble hormones).

• Signal Transduction: Binding initiates a signal transduction pathway, leading to changes in gene expression, enzyme activity, or cellular function.

• Specificity: Only cells with the appropriate receptor respond to a given hormone.

• Example: Epinephrine binds to receptors on liver cells, triggering glycogen breakdown.

Negative Feedback and Nervous System Coordination

Hormone pathways are often regulated by negative feedback and interact with the nervous system to maintain homeostasis.

• Negative Feedback: A process in which the end product of a pathway inhibits its own production, maintaining balance.

• Coordination: The hypothalamus integrates nervous and endocrine signals, controlling the pituitary gland.

• Example: Regulation of blood glucose by insulin and glucagon.

Hormonal Regulation in Homeostasis, Development, and Behavior

• Homeostasis: Hormones like insulin regulate blood sugar; antidiuretic hormone (ADH) controls water balance.

• Development: Thyroid hormones regulate metamorphosis in amphibians; sex hormones drive puberty.

• Behavior: Oxytocin influences social bonding and reproductive behaviors.

Ch. 46: Animal Reproduction

Types of Reproduction

Animals reproduce asexually or sexually, each with distinct mechanisms and evolutionary advantages.

• Asexual Reproduction: Offspring arise from a single parent without gamete fusion. Types include:

  • Budding: New individuals form from outgrowths (e.g., hydra).

  • Fission: Parent splits into two (e.g., sea anemones).

  • Parthenogenesis: Offspring develop from unfertilized eggs (e.g., some lizards).

• Sexual Reproduction: Involves fusion of male and female gametes (sperm and egg) to form a zygote.

Mechanisms of Fertilization

• External Fertilization: Gametes released into the environment; common in aquatic animals.

• Internal Fertilization: Sperm deposited in or near the female reproductive tract; adaptation to terrestrial life.

Gametogenesis and Delivery

• Male Reproductive System: Testes produce sperm via spermatogenesis; sperm delivered through ducts and penis.

• Female Reproductive System: Ovaries produce eggs via oogenesis; eggs travel through oviducts to uterus.

Hormonal Regulation of Sexual Reproduction

• Males: Testosterone regulates sperm production and secondary sexual characteristics.

• Females: Estrogen and progesterone regulate the menstrual/estrous cycle and ovulation.

• Feedback Loops: Hypothalamic-pituitary-gonadal axis controls hormone levels.

From Egg to Embryo

• Fertilization: Sperm and egg fuse to form a zygote.

• Cleavage: Rapid cell divisions without growth, forming a blastula.

• Gastrulation: Cells rearrange to form germ layers.

Ch. 47: Animal Development

Initial Stages of Embryonic Development

• Fertilization: Union of gametes to form a zygote.

• Cleavage: Series of mitotic divisions producing a multicellular embryo.

• Blastula Formation: Hollow ball of cells formed after cleavage.

Morphogenesis: Cell Shape, Position, and Survival

• Gastrulation: Formation of three germ layers (ectoderm, mesoderm, endoderm).

• Cell Movement: Cells migrate to new positions, shaping tissues and organs.

• Apoptosis: Programmed cell death sculpts tissues (e.g., removal of webbing between fingers).

Ch. 48: Neurons, Synapses, and Signaling

Neuron Structure and Function

• Neurons: Specialized cells for information transfer, consisting of dendrites, cell body, and axon.

• Structure-Function Relationship: Dendrites receive signals; axons transmit signals over long distances.

Establishing Resting Potential

• Ion Pumps: Sodium-potassium pumps maintain concentration gradients across the membrane.

• Ion Channels: Allow selective movement of ions, contributing to membrane potential.

• Resting Potential Equation:

$V_m = \frac{RT}{F} \ln \left( \frac{[K^+]_{out}}{[K^+]_{in}} \right)$

• Additional info: This is the Nernst equation for potassium; actual resting potential considers all permeant ions.

Action Potentials

• Definition: Rapid, transient changes in membrane potential that propagate along axons.

• Steps: Depolarization, repolarization, and return to resting state.

• Role: Enable long-distance signaling in the nervous system.

Ch. 49: Nervous Systems

Organization of the Vertebrate Nervous System

• Central Nervous System (CNS): Brain and spinal cord; processes information.

• Peripheral Nervous System (PNS): Nerves and ganglia; transmits signals to and from CNS.

Brain Regions and Functions

• Cerebrum: Voluntary movement, sensory processing, cognition.

• Cerebellum: Coordination and balance.

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

• Diencephalon: Thalamus and hypothalamus; sensory relay and homeostasis.

Cerebral Cortex

• Role: Controls voluntary movement, language, reasoning, perception, and higher cognitive functions.

• Example: Motor cortex initiates movement; prefrontal cortex involved in decision-making.

Ch. 50: Sensory and Motor Mechanisms

Sensory Transduction and Signal Transmission

• Transduction: Conversion of sensory stimuli into electrical signals by sensory receptors.

• Transmission: Sensory neurons relay signals to the CNS for processing.

Mechanoreceptors: Hearing and Equilibrium

• Hearing: Hair cells in the cochlea detect sound vibrations.

• Equilibrium: Vestibular system senses head position and movement.

Vision in Vertebrates

• Light Detection: Photoreceptors (rods and cones) in the retina absorb light.

• Signal Processing: Visual information is transmitted via the optic nerve to the brain's visual cortex.

Chemoreceptors: Taste and Smell

• Taste: Taste buds detect chemicals dissolved in saliva.

• Smell: Olfactory receptors in the nasal cavity bind odor molecules.

Muscle Movement and Protein Filaments

• Muscle Contraction: Sliding of actin and myosin filaments shortens muscle fibers.

• Equation:

$\text{Muscle contraction:} \quad \text{Actin} + \text{Myosin} \rightarrow \text{Sliding Filaments}$

Skeletal Systems in Animals

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

• Exoskeleton: Hard external covering (e.g., insects, crustaceans).

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

• Comparison Table:

Skeleton Type	Structure	Examples
Hydrostatic	Fluid-filled cavity	Earthworm
Exoskeleton	External hard covering	Insect, crab
Endoskeleton	Internal bones/cartilage	Human, fish