Animal Structure, Function, and Physiology: Study Guide

Chapter 39: Animal Structure and Function

Adaptations, Traits, and Fitness

• Adaptation: A heritable trait that increases an organism's fitness in a particular environment. Adaptations arise through natural selection.

• Trait: Any observable characteristic of an organism, such as morphology, physiology, or behavior.

• Fitness: The ability of an organism to survive and reproduce, contributing genes to the next generation.

• Example: The thick fur of arctic foxes is an adaptation for cold climates, increasing their fitness.

Trade-Offs in Structure and Function

• Trade-off: A compromise between two traits that cannot be optimized simultaneously. For example, increased muscle mass may improve strength but reduce endurance.

• Trade-offs influence the evolution of traits and their impact on fitness.

Experimental Design: Cricket Immune Function

• Strengths: Controlled variables, measurable outcomes.

• Weaknesses: May not account for all environmental factors; limited sample size can affect generalizability.

Animal Tissue Types

• Epithelial Tissue: Covers body surfaces and lines cavities; functions in protection, absorption, and secretion.

• Connective Tissue: Supports, binds, and protects other tissues; includes bone, blood, cartilage, and adipose tissue.

• Muscle Tissue: Responsible for movement; includes skeletal, cardiac, and smooth muscle.

• Nervous Tissue: Conducts electrical impulses; composed of neurons and supporting cells.

Digestive System Anatomy and Function

• Mouth: Mechanical and chemical digestion begins.

• Esophagus: Transports food to the stomach.

• Stomach: Protein digestion; acidic environment.

• Small Intestine: Major site of nutrient absorption.

• Large Intestine: Water absorption and feces formation.

Surface Area, Volume, and Basal Metabolic Rate (BMR)

• As animals increase in size, surface area increases by the square of length, while volume increases by the cube of length.

• BMR: The rate at which an animal consumes oxygen while at rest. Smaller animals have higher BMR per unit mass due to higher surface area-to-volume ratios.

• Equation: $BMR \propto \text{mass}^{3/4}$

Organ Features Increasing Surface Area

• Structures such as villi in the intestine, alveoli in the lungs, and capillary networks increase surface area for exchange.

Negative Feedback and Homeostasis

• Negative Feedback Loop: A process that detects deviations from a set point and triggers responses to return to that set point.

• Components: Sensor, integrator, effector.

• Example: Regulation of body temperature in mammals.

Chapter 40: Osmoregulation

Osmolarity and Solutions

• High Molarity: Solution with a high concentration of solutes.

• Low Molarity: Solution with a low concentration of solutes.

Ion Pumps and Electrochemical Gradients

• Pumps (e.g., Na+/K+ ATPase) use energy to move ions, establishing gradients across membranes.

• These gradients drive passive movement of ions and water, influencing cell volume and function.

Excretion of Urea in Humans

• Humans convert toxic ammonia to urea in the liver, which is less toxic and excreted in urine.

Anatomy and Flow in the Kidney and Nephron

• Kidney: Filters blood, removes waste, regulates water and electrolyte balance.

• Nephron: Functional unit; includes renal corpuscle, proximal tubule, loop of Henle, distal tubule, and collecting duct.

• Filtrate flows from the glomerulus → Bowman's capsule → proximal tubule → loop of Henle → distal tubule → collecting duct.

Filtrate Formation and Reabsorption

• Renal Corpuscle: Blood pressure forces water and small solutes into Bowman's capsule (filtration).

• Proximal Tubule: Reabsorbs Na+, glucose, amino acids, and water back into the blood.

Countercurrent Osmotic Gradient in the Loop of Henle

• Descending Limb: Permeable to water, not solutes; water exits, concentrating filtrate.

• Ascending Limb: Impermeable to water; actively transports Na+ and Cl- out, diluting filtrate.

• Establishes a gradient that allows for water reabsorption in the collecting duct.

Antidiuretic Hormone (ADH)

• ADH increases water reabsorption in the collecting duct, reducing urine volume.

Chapter 42: Gas Exchange and Circulation

Endotherms vs. Ectotherms

• Endotherms: Generate heat metabolically (e.g., mammals, birds).

• Ectotherms: Rely on external sources for body heat (e.g., reptiles, amphibians).

Countercurrent Exchangers

• Require two fluids flowing in opposite directions, maximizing exchange efficiency (e.g., fish gills, loop of Henle).

Steps in Gas Exchange

• Ventilation → Diffusion at respiratory surface → Circulation → Diffusion into tissues → Cellular respiration.

Partial Pressure and Fick's Law

• Partial Pressure: The pressure exerted by a single gas in a mixture.

• Fick's Law: Describes the rate of diffusion:

$\text{Rate of diffusion} = k \cdot A \cdot \frac{(P_2 - P_1)}{D}$

• Where k is the diffusion constant, A is surface area, P2 - P1 is the difference in partial pressures, and D is the thickness of the barrier.

Blood and Its Components

• Plasma: Liquid matrix; transports nutrients, hormones, waste.

• Red Blood Cells: Carry oxygen via hemoglobin.

• White Blood Cells: Immune defense.

• Platelets: Blood clotting.

Hemoglobin, Cooperative Binding, and the Bohr Shift

• Cooperative Binding: Binding of one O2 molecule increases hemoglobin's affinity for more O2.

• Bohr Shift: Lower pH or higher temperature reduces hemoglobin's O2 affinity, facilitating O2 release during exercise.

CO2 Transport and pH Buffering

• CO2 is transported dissolved in plasma, bound to hemoglobin, or as bicarbonate ions.

• Buffering maintains blood pH:

$\mathrm{CO}_2 + \mathrm{H}_2O \leftrightarrow \mathrm{H}_2\mathrm{CO}_3 \leftrightarrow \mathrm{H}^+ + \mathrm{HCO}_3^-$

Blood Vessel Types and Characteristics

Vessel Type	Structure	Function
Arteries	Thick, muscular walls	Carry blood away from heart; high pressure
Veins	Thinner walls, valves	Return blood to heart; low pressure
Capillaries	Single-cell thick	Exchange of gases, nutrients, wastes

Partial Pressures in Circulation

• O2 partial pressure decreases and CO2 increases as blood moves from arteries to veins.

Heart Anatomy and Blood Flow Path

• Blood flows: Vena cava → Right atrium → Right ventricle → Pulmonary artery → Lungs → Pulmonary vein → Left atrium → Left ventricle → Aorta → Body.

Electrical Activation of the Heart

• Sequence: SA node (pacemaker) → AV node → Bundle branches → Purkinje fibers.

• Coordinates contraction and regulates blood pressure.

Blood Flow Regulation

• Blood flow is regulated by pressure and resistance:

$\text{Flow} = \frac{\text{Pressure}}{\text{Resistance}}$

• Arteries have the highest pressure in the circulatory system.

Chapter 43: Neurons and Electrical Signaling

Central Nervous System (CNS) and Neurons

• CNS: Brain and spinal cord; integrates information and coordinates responses.

• Neurons: Functional units of the nervous system; transmit electrical signals.

Neuron Structure and Information Flow

• Dendrites: Receive signals.

• Cell Body (Soma): Integrates signals.

• Axon: Transmits signals to other cells.

• Information flows: Dendrite → Soma → Axon → Synapse.

Types of Neurons

• Sensory Neurons: Detect stimuli.

• Interneurons: Connect neurons within CNS.

• Motor Neurons: Stimulate muscles or glands.

Membrane Potential

• Calculated using the Nernst equation:

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

• Generated by ion gradients and selective permeability of the membrane.

Action Potentials

• All-or-none electrical impulses that travel along axons.

• Key properties: threshold, depolarization, repolarization, refractory period.

Neuronal Communication

• Action potential reaches axon terminal → neurotransmitter release → binds to receptors on postsynaptic cell → generates postsynaptic potential.

Chapter 44: Sensory Mechanisms

Synapse Components

• Presynaptic terminal, synaptic cleft, postsynaptic membrane.

EPSPs and IPSPs

• EPSP (Excitatory Postsynaptic Potential): Depolarizes the postsynaptic membrane, increasing likelihood of action potential.

• IPSP (Inhibitory Postsynaptic Potential): Hyperpolarizes the membrane, decreasing likelihood of action potential.

Divisions of the Nervous System

• CNS: Brain and spinal cord.

• PNS: All neural tissue outside CNS; includes somatic and autonomic divisions.

Brain Organization and Functional Specialization

• Cortical lobes (frontal, parietal, temporal, occipital) have specialized functions (e.g., movement, sensation, hearing, vision).

Learning and Memory Encoding

• Thought to involve synaptic plasticity—changes in synaptic strength and connectivity.

Autonomic Nervous System (ANS) Divisions

• Sympathetic Nervous System (SNS): "Fight or flight" responses; increases heart rate, dilates pupils.

• Parasympathetic Nervous System (PNS): "Rest and digest"; slows heart rate, stimulates digestion.

• Somas of SNS mostly in spinal cord; PNS in brainstem and sacral spinal cord.

Encoding Sound in the Inner Ear

• Sound waves vibrate the cochlea, stimulating hair cells that convert mechanical energy to electrical signals sent to the brain via the auditory nerve.

Visual Information Pathway

• Photoreceptors in the retina → optic nerve → thalamus → visual cortex in the occipital lobe.

Gustatory System Anatomy and Pathway

• Taste buds on the tongue detect chemicals → signals sent via cranial nerves to the gustatory cortex.

Chapter 47: Animal Reproduction

Asexual vs. Sexual Reproduction

• Asexual Reproduction: Offspring genetically identical to parent; common in stable environments.

• Sexual Reproduction: Involves gamete fusion; increases genetic diversity.

• Regulation in Daphnia: Environmental cues (e.g., crowding, food availability) trigger switch between modes.

Gamete Production and Structure

• Gametes (sperm and eggs) are haploid (n); produced by meiosis.

• Sperm: Small, motile; Egg: Large, nutrient-rich.

Oogenesis and Fertilization

• Oogenesis: Formation of eggs; involves unequal cytokinesis, producing one ovum and polar bodies.

• Internal Fertilization: Sperm deposited inside female; common in terrestrial animals.

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

Prevention of Polyspermy

• Fertilized egg blocks entry of additional sperm via fast (membrane depolarization) and slow (cortical granule release) blocks.

Germ Layers and Gastrulation

• Gastrulation forms three germ layers: ectoderm, mesoderm, endoderm.

• These layers give rise to all tissues and organs.

Human Reproductive System Functions

• Male: Produces and delivers sperm; testes, vas deferens, prostate, penis.

• Female: Produces eggs, supports embryo; ovaries, oviducts, uterus, vagina.

Sex Hormones and Regulation

• Major Hormones: Testosterone (testes), estrogen and progesterone (ovaries).

• Regulated by hypothalamic-pituitary-gonadal axis.

Ovulation Phases and Hormones

• Follicular phase (FSH, estrogen), ovulation (LH surge), luteal phase (progesterone).

Function of hCG

• Human chorionic gonadotropin (hCG) maintains corpus luteum and progesterone production in early pregnancy.