BIO 114 Exam 3 Study Guide: Gas Exchange, Circulation, Nervous System, Sensory System, Animal Movement, and Chemical Signals

Chapter 42: Gas Exchange and Circulation

Fick’s Law of Diffusion and Gas Exchange

Fick’s Law describes the rate of diffusion of gases across membranes, which is fundamental to respiratory physiology.

• Fick’s Law Equation: The rate of diffusion ($Q$) is given by: $Q = \frac{DA(P_1 - P_2)}{L}$ where:

  • $D$ = diffusion coefficient

  • $A$ = surface area

  • $(P_1 - P_2)$ = difference in partial pressure

  • $L$ = thickness of membrane

• Evolutionary Adaptations: Organisms may increase surface area (A), decrease membrane thickness (L), or maximize partial pressure difference to enhance gas exchange.

• Example: Fish gills have large surface area and thin membranes to maximize diffusion.

Countercurrent Flow in Gills

Countercurrent flow is a mechanism in fish gills that maximizes oxygen uptake.

• Mechanism: Water and blood flow in opposite directions, maintaining a gradient for oxygen diffusion.

• Efficiency: Allows fish to extract up to 80% of oxygen from water.

Breathing Mechanisms in Amphibians, Mammals, and Birds

Different vertebrates have evolved distinct breathing mechanisms.

• Amphibians: Use positive pressure breathing (forcing air into lungs).

• Mammals: Use negative pressure breathing (diaphragm contraction expands thoracic cavity).

• Birds: Use unidirectional airflow and air sacs for highly efficient gas exchange.

• Comparison Table:

Group	Mechanism	Efficiency
Amphibians	Positive pressure	Moderate
Mammals	Negative pressure	High
Birds	Unidirectional flow	Very high

Mammalian Lungs and Fick’s Law

Mammalian lungs are structured to maximize gas exchange efficiency.

• Alveoli: Provide large surface area and thin membranes.

• Partial Pressure: Maintained by ventilation.

Diaphragm and Inhalation

The diaphragm is a muscle that powers inhalation in mammals.

• Contraction: Diaphragm contracts, increasing thoracic volume and decreasing pressure, drawing air in.

CNS Regulation of Breathing

The central nervous system (CNS) regulates breathing rate and depth.

• Medulla Oblongata: Detects CO2 levels and adjusts breathing.

Hemoglobin Structure and Oxygen Binding

Hemoglobin is a protein in red blood cells that binds oxygen.

• Structure: Four polypeptide chains, each with a heme group.

• Oxygen Binding: Cooperative binding increases efficiency.

Bohr Shift and Oxygen Affinity

Hemoglobin’s affinity for oxygen changes with environmental conditions.

• Bohr Shift: Lower pH and higher CO2 decrease affinity, promoting oxygen release.

Carbon Dioxide Transport in Blood

CO2 is transported in three forms:

• Dissolved in plasma

• Bound to hemoglobin

• As bicarbonate ions ($CO_2 + H_2O \rightarrow HCO_3^- + H^+$)

Formed Elements in Blood

Blood contains several types of formed elements:

• Red blood cells (erythrocytes): Transport oxygen

• White blood cells (leukocytes): Immune function

• Platelets: Blood clotting

Cardiac Cycle Elements

The cardiac cycle describes the sequence of heart contractions.

• Systole: Contraction phase

• Diastole: Relaxation phase

Arteries, Arterioles, and Capillaries

Blood vessels have specialized structures to withstand pressure.

• Arteries/Arterioles: Thick, elastic walls to withstand high pressure

• Capillaries: Thin walls for exchange, cannot withstand high pressure

Veins vs. Arteries

Veins and arteries differ in structure and function.

• Veins: Thinner walls, valves to prevent backflow

• Arteries: Thicker, more muscular walls

Lymphatic System Operation

The lymphatic system returns excess fluid to the bloodstream and is involved in immune responses.

• Lymph Vessels: Collect interstitial fluid

• Lymph Nodes: Filter lymph and house immune cells

Chapter 43: Nervous System

Major Divisions of the Vertebrate Nervous System

The vertebrate nervous system is divided into central and peripheral components.

• Central Nervous System (CNS): Brain and spinal cord

• Peripheral Nervous System (PNS): Nerves outside CNS

Production of Resting Potential

The resting potential is the voltage difference across a neuron’s membrane.

• Mechanism: Maintained by sodium-potassium pump ($3 Na^+$ out, $2 K^+$ in)

• Typical Value: About -70 mV

Action Potential Characteristics

An action potential is a rapid change in membrane potential.

• All-or-none: Fires completely or not at all

• Depolarization: Na+ influx

• Repolarization: K+ efflux

Neuron Structure and Support Cells

Neurons have specialized structures and are supported by glial cells.

• Parts: Dendrites, cell body, axon, synaptic terminals

• Support Cells: Schwann cells, oligodendrocytes, astrocytes

Voltage-Gated Channels and Action Potentials

Voltage-gated channels open in response to changes in membrane potential.

• Na+ Channels: Open during depolarization

• K+ Channels: Open during repolarization

Propagation of Action Potentials

Action potentials travel along axons via local depolarization.

• Saltatory Conduction: In myelinated axons, jumps between nodes of Ranvier

Synaptic Communication

Neurons communicate across synapses using neurotransmitters.

• Electrical: Direct ion flow

• Chemical: Neurotransmitter release

Excitatory vs. Inhibitory Neurotransmitters

Neurotransmitters can either excite or inhibit postsynaptic neurons.

• Excitatory: Increase likelihood of action potential (e.g., glutamate)

• Inhibitory: Decrease likelihood (e.g., GABA)

Neuronal Integration

Neurons integrate multiple inputs to determine response.

• Summation: Temporal and spatial summation of signals

Brain Organization in Vertebrates

The vertebrate brain is organized into regions with specialized functions.

• Forebrain: Cerebrum, thalamus, hypothalamus

• Midbrain: Sensory processing

• Hindbrain: Cerebellum, medulla

Human Forebrain (Cerebrum) Areas

The cerebrum is divided into lobes with distinct functions.

• Frontal: Decision-making, motor control

• Parietal: Sensory processing

• Temporal: Hearing, memory

• Occipital: Vision

Somatic, Autonomic, Sympathetic, and Parasympathetic Systems

The PNS is divided into functional systems.

• Somatic: Voluntary control

• Autonomic: Involuntary control

• Sympathetic: "Fight or flight"

• Parasympathetic: "Rest and digest"

Chapter 44: Sensory System

Sensory Information Transmission

Sensory receptors convert stimuli into electrical signals sent to the CNS.

• Transduction: Conversion of stimulus to action potential

Gated Ion Channels

Gated ion channels open or close in response to stimuli.

• Types: Voltage-gated, ligand-gated, mechanically-gated

Types of Sensory Receptors

Sensory receptors are specialized for different stimuli.

• Mechanoreceptors: Touch, pressure

• Chemoreceptors: Chemical detection (taste, smell)

• Photoreceptors: Light detection (vision)

Soundwave Detection in Inner Ear

Soundwaves are converted to action potentials in the cochlea.

• Mechanism: Vibrations move hair cells, opening ion channels

Frequency Differentiation in Mammals

Mammals distinguish sound frequencies via cochlear structure.

• Basilar Membrane: Different regions respond to different frequencies

Olfactory Receptor Function

Olfactory receptors detect odor molecules.

• Mechanism: Binding of odorant opens ion channels, generating action potential

Invertebrate vs. Vertebrate Eyes

Eyes differ in structure between invertebrates and vertebrates.

• Simple Eyes: Single lens (vertebrates)

• Compound Eyes: Multiple lenses (invertebrates)

Rods vs. Cones

Photoreceptors in vertebrate eyes are classified as rods and cones.

• Rods: Sensitive to low light, no color

• Cones: Color vision, less sensitive to light

Photoreceptor Function

Photoreceptors convert light into electrical signals.

• Mechanism: Light changes shape of photopigments, triggering ion channel changes

Chapter 45: Animal Movement

Types of Muscle and Muscle Cells

Animals possess three types of muscle tissue.

• Skeletal Muscle: Voluntary movement

• Cardiac Muscle: Heart contraction

• Smooth Muscle: Involuntary movement (organs)

Sliding Filament Mechanism

Muscle contraction occurs via the sliding filament mechanism.

• Actin and Myosin: Myosin heads bind to actin, pulling filaments past each other

• ATP: Provides energy for contraction

Muscle Contraction and Nerve Impulse

Muscle contraction is initiated by nerve impulses.

• Neuromuscular Junction: Acetylcholine release triggers action potential in muscle

Types of Skeletons

Animals have three main types of skeletons.

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

• Exoskeleton: External shell (e.g., insects)

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

Chapter 46: Chemical Signals

Hormones and Body Regulation

Hormones are chemical messengers that regulate physiological processes.

• Endocrine System: Glands release hormones into bloodstream

Lipophilic vs. Hydrophilic Hormones

Hormones are classified by their solubility.

• Lipophilic: Fat-soluble, cross cell membranes (e.g., steroid hormones)

• Hydrophilic: Water-soluble, bind to membrane receptors (e.g., peptide hormones)

Peptide Hormone Signal Transduction

Peptide hormones use signal transduction to affect target cells.

• Mechanism: Bind to membrane receptor, activate second messenger pathways

Hypothalamus and Pituitary Connections

The hypothalamus controls the pituitary gland, which regulates other endocrine glands.

• Posterior Pituitary: Releases hormones made in hypothalamus

• Anterior Pituitary: Produces and releases its own hormones

Insulin vs. Glucagon Effects

Insulin and glucagon regulate blood glucose levels.

• Insulin: Lowers blood glucose by promoting uptake into cells

• Glucagon: Raises blood glucose by stimulating release from liver