Anatomy & Physiology Review: Chapters 5–10 (Membrane Dynamics, Communication, Endocrine, Neurons, CNS, Sensory Physiology)

Chapter 5: Membrane Dynamics

Concentration Gradients

Concentration gradients are differences in the concentration of a substance between two regions. They drive the movement of molecules across cell membranes.

• Definition: A concentration gradient exists when the concentration of particles is higher in one area than another.

• Application: Gradients are essential for processes such as diffusion and osmosis.

Diffusion

Diffusion is the passive movement of molecules from an area of higher concentration to an area of lower concentration.

• Key Properties: No energy required; rate depends on temperature, size of molecules, and gradient steepness.

• Example: Oxygen diffuses from alveoli into blood.

Osmosis

Osmosis is the diffusion of water across a selectively permeable membrane.

• Key Point: Water moves from areas of low solute concentration to high solute concentration.

• Example: Water absorption in kidney tubules.

Chemical and Electrical Disequilibrium

Chemical and electrical disequilibrium across membranes creates electrochemical gradients, which are crucial for cell signaling and transport.

• Electrochemical Gradient: Combination of concentration gradient and electrical potential difference.

• Application: Drives ion movement, e.g., Na+ and K+ across neuron membranes.

Cell Structure

Cell structure includes the plasma membrane, cytoplasm, and organelles, each contributing to membrane dynamics.

• Plasma Membrane: Phospholipid bilayer with embedded proteins.

• Function: Regulates entry and exit of substances.

Chapter 6: Communication, Integration, and Homeostasis

Local Communication (Fig 6.1)

• Gap Junctions: Direct cytoplasmic connections between adjacent cells.

• Contact-Dependent Signals: Require interaction between membrane molecules.

• Autocrine/Paracrine Signals: Act on the same cell or nearby cells.

Signal Receptors (Fig 6.3 a,b)

• Intracellular Receptors: Bind lipophilic signals inside the cell; slower response.

• Cell Membrane Receptors: Bind extracellular signals; rapid cellular responses.

Signal Transduction (Fig 6.5, 6.6a, 6.6b)

• Transduction: Conversion of a signal from one form to another.

• Cascade: Series of reactions amplifying the signal (Fig 6.6a).

• Amplification: Small signal produces a large effect (Fig 6.6b).

Ligands and Receptors (Fig 6.13)

• Primary Ligand: Activates receptor.

• Agonist: Also activates receptor.

• Antagonist: Blocks receptor activity.

Chapter 7: Introduction to the Endocrine System

Hormone Types and Properties (Table 7.1)

Property	Peptide Hormones	Steroid Hormones	Amine Hormones
Synthesis & Storage	Made in advance, stored	Synthesized on demand	Made in advance or on demand
Release from Parent Cell	Exocytosis	Simple diffusion	Exocytosis or diffusion
Transport in Blood	Dissolved in plasma	Bound to carrier proteins	Dissolved or bound
Half-Life	Short	Long	Short or long
Location of Receptor	Cell membrane	Cytoplasm or nucleus	Cell membrane or nucleus
General Target Response	Modification of proteins	Gene activation	Modification of proteins or gene activation
Examples	Insulin, parathyroid hormone	Estrogen, cortisol	Epinephrine, thyroid hormone

Anterior Pituitary and Hormone Pathways (Fig 7.8, 7.8c, 7.1)

• Anterior Pituitary: Releases hormones that regulate other endocrine glands.

• Portal System: Connects hypothalamus to pituitary for hormone transport.

• Trophic Hormones: Regulate hormone levels via feedback loops (Fig 7.1).

Chapter 8: Neurons: Cellular and Network Properties

Glial Cells (Fig 8.5)

• Central Nervous System: Ependymal cells, astrocytes, microglia, oligodendrocytes.

• Peripheral Nervous System: Schwann cells, satellite cells.

• Functions: Support, insulation, immune protection, nutrient supply.

Action Potentials

• Ions Involved: Na+, K+, Ca2+.

• Graded vs Action Potentials: Graded are variable in size; action potentials are all-or-none.

• Speed: Influenced by axon diameter and myelination.

• Divergent/Convergent Pathways: Neuronal circuits that spread or integrate signals.

• Synaptic Inhibition: Reduces likelihood of action potential firing.

Resting Membrane Potential & Nernst Equation

• Resting Membrane Potential: Electrical potential across the cell membrane at rest.

• Nernst Equation: Calculates equilibrium potential for an ion: $E_{ion} = \frac{61}{z} \log \left( \frac{[ion]_{out}}{[ion]_{in}} \right)$

• Example: Use sodium ion concentrations to calculate $E_{Na}$.

Ion	Extracellular Fluid (mM)	Intracellular Fluid (mM)	Equilibrium Potential (mV)
K+	4	150	-90
Na+	145	15	+60
Cl-	108	10	-63
Ca2+	1	0.0001	+120

Refractory Periods (Fig 8.12)

• Absolute Refractory Period: No new action potential can be initiated.

• Relative Refractory Period: Stronger stimulus required for action potential.

Chapter 9: The Central Nervous System

Development of the CNS (Fig 9.2)

• Neural Tube Formation: By day 23, neural tube forms CNS; neural crest forms PNS.

• Brain Regions: Hindbrain, midbrain, forebrain differentiate by 6 weeks.

Cell Body Location: Gray vs White Matter (Fig 9.3)

• Gray Matter: Cell bodies, dendrites, unmyelinated axons.

• White Matter: Myelinated axons.

• Meninges: Dura mater (veins), arachnoid (CSF), pia mater (arteries).

Energy Source for Brain and Oxygen Consumption

• Glucose: Primary energy source for neurons.

• Oxygen: Essential for ATP production; high consumption rate.

CSF Production and Composition

• Cerebrospinal Fluid (CSF): Produced by choroid plexus; cushions brain and removes waste.

Cranial Nerves

• Function: Sensory and motor innervation of head and neck.

Stages of Sleep

• Non-REM: Stages N1, N2, N3 (slow-wave sleep).

• REM: Rapid eye movement, dreaming.

• EEG Patterns: Alpha waves (awake), delta waves (deep sleep).

Types of Memory and Memory Loss

• Short-Term Memory: Temporary storage.

• Long-Term Memory: Permanent storage.

• Memory Loss: Can result from injury, disease, or aging.

Referred Pain

• Definition: Pain perceived at a location other than the site of origin.

• Example: Heart attack pain felt in left arm.

Chapter 10: Sensory Physiology

Receptive Fields and Sensory Discrimination (Fig 10.2)

• Large Receptive Fields: Less precise localization (e.g., leg).

• Small Receptive Fields: More precise localization (e.g., finger).

Lateral Inhibition (Fig 10.5)

• Definition: Enhances contrast and sharpens sensory perception.

• Mechanism: Inhibition of neighboring neurons increases stimulus discrimination.

Somatosensory Pathways (Fig 10.8)

• Pathway: Primary, secondary, and tertiary sensory neurons transmit signals to the brain.

• Integration: Occurs in the somatosensory cortex.

EEG Patterns in Sleep and Wakefulness

• Alpha Waves: Awake, relaxed state.

• REM Sleep: Rapid, irregular waves.

• Non-REM Sleep: Progression from light to deep sleep (delta waves).

Additional info:

• Some figures and tables were interpreted and expanded for clarity and completeness.

• Key terms and processes were defined and contextualized for exam preparation.