Resting Membrane Potential

Definition and Maintenance

The resting membrane potential is the electrical potential difference across the plasma membrane of a cell at rest. It is essential for the function of excitable cells such as neurons and muscle fibers.

• Ions Involved: Primarily sodium (Na+), potassium (K+), chloride (Cl-), and negatively charged proteins.

• Maintenance: Maintained by the sodium-potassium pump (Na+/K+ ATPase), which actively transports 3 Na+ ions out and 2 K+ ions into the cell, and by selective permeability of the membrane to K+.

• Typical Value: Approximately -70 mV in neurons.

Equation:

Additional info: This is the Nernst equation for a single ion; the Goldman-Hodgkin-Katz equation is used for multiple ions.

Cell Biology

Functions of Organelles

• Mitochondria: Site of ATP production via cellular respiration.

• Ribosomes: Sites of protein synthesis.

• Endoplasmic Reticulum (ER): Rough ER synthesizes proteins; smooth ER synthesizes lipids and detoxifies chemicals.

• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.

• Lysosomes: Contain digestive enzymes for breaking down waste.

Cell Growth and Reproduction

• DNA Replication: Occurs during the S phase of the cell cycle, prior to cell division.

• Mitosis vs. Cytokinesis:

  • Mitosis: Division of the nucleus and its contents.

  • Cytokinesis: Division of the cytoplasm, resulting in two daughter cells.

Protein Synthesis

• Transcription: The process of copying DNA into messenger RNA (mRNA) in the nucleus.

• Translation: The process by which ribosomes synthesize proteins using mRNA as a template.

• Product: Transcription produces mRNA; translation produces a polypeptide (protein).

• Types of RNA: mRNA (messenger), tRNA (transfer), rRNA (ribosomal).

• Steps:

  1. Initiation

  2. Elongation

  3. Termination

• Role of Each RNA:

  • mRNA: Carries genetic code from DNA to ribosome.

  • tRNA: Brings amino acids to the ribosome.

  • rRNA: Forms the core of the ribosome's structure and catalyzes protein synthesis.

Histology

Definition of Tissue

A tissue is a group of similar cells that perform a common function.

Epithelium

• General Functions/Characteristics: Covers body surfaces, lines cavities, forms glands; cells are closely packed with minimal extracellular matrix.

• Classification: Based on cell shape (squamous, cuboidal, columnar) and number of layers (simple, stratified).

• Types of Glands: Exocrine (secrete into ducts), endocrine (secrete into blood).

Connective Tissue

• General Functions/Characteristics: Supports, binds, and protects other tissues; contains cells, fibers, and ground substance.

• Classification: Loose (areolar, adipose), dense (regular, irregular), cartilage, bone, blood.

Nervous Tissue

• General Functions/Characteristics: Conducts electrical impulses; coordinates body activities.

• Cell Types: Neurons (transmit impulses), neuroglia (support neurons).

Membranes

• Types: Cutaneous (skin), mucous (lines cavities open to exterior), serous (lines closed cavities).

• Distinguishing Features: Cutaneous is dry, mucous is moist, serous secretes lubricating fluid.

Tissue Repair

• Process: Involves inflammation, proliferation, and remodeling phases.

• Different Tissue Types: Epithelial tissues regenerate well; connective tissues vary; nervous and muscle tissues have limited capacity.

Integumentary System

Epidermis

• Cell Types: Keratinocytes (produce keratin), melanocytes (produce melanin), Langerhans cells (immune), Merkel cells (sensory).

• Layers (from superficial to deep):

  1. Stratum corneum

  2. Stratum lucidum (only in thick skin)

  3. Stratum granulosum

  4. Stratum spinosum

  5. Stratum basale

Dermis

• General Characteristics/Function: Provides strength, flexibility, and nourishment to the epidermis; contains blood vessels, nerves, glands, and hair follicles.

• Layers:

  • Papillary layer: Superficial, areolar connective tissue, forms dermal papillae.

  • Reticular layer: Deep, dense irregular connective tissue.

Pigments Involved in Skin Color

Hair

• Characteristics/Functions: Protection, sensation, reduces heat loss.

Nails

• Characteristics/Functions: Protect distal phalanges, aid in grasping objects.

Glands

• Types: Sebaceous (oil), sudoriferous (sweat), ceruminous (earwax).

• Functions: Lubricate skin/hair, regulate temperature, protect against microbes.

Skin Cancer

• General Terms: Uncontrolled growth of skin cells.

• Types:

  1. Basal cell carcinoma

  2. Squamous cell carcinoma

  3. Melanoma

Burns