Resting Membrane Potential

Definition and Maintenance

The resting membrane potential is the electrical potential difference across the plasma membrane of a cell when it is not actively sending signals. It is essential for the function of excitable cells such as neurons and muscle cells.

• Ions involved: Mainly sodium (Na+), potassium (K+), and chloride (Cl-).

• Maintenance: The sodium-potassium pump (Na+/K+ ATPase) actively transports 3 Na+ out and 2 K+ into the cell, maintaining the potential.

• Typical value: Approximately -70 mV in neurons.

Equation:

(for a membrane permeable only to K+) (Nernst equation)

Cell Biology

Functions of Organelles

Cells contain specialized structures called organelles that perform distinct functions necessary for survival and growth.

• Mitochondria: Site of ATP production via cellular respiration.

• Ribosomes: Responsible for protein synthesis.

• Nucleus: Contains genetic material (DNA).

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

• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.

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.

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

Protein Synthesis

Protein synthesis involves two main processes: transcription and translation.

• Transcription: DNA is used as a template to synthesize messenger RNA (mRNA).

• Translation: mRNA is decoded by ribosomes to assemble amino acids into a polypeptide chain.

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

• Role of each:

  • mRNA: Carries genetic code from DNA to ribosome.

  • tRNA: Brings amino acids to the ribosome.

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

Equation:

Histology

Definition of Tissue

Tissue is a group of similar cells that perform a specific function.

Epithelium

• General functions/characteristics: Protection, absorption, secretion, and sensation.

• 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: Support, protection, transport, storage, and immune defense.

• Classification: Loose connective tissue, dense connective tissue, cartilage, bone, blood.

Nervous Tissue

• General functions/characteristics: Conducts electrical impulses, processes information.

• Types of cells: Neurons (transmit signals), neuroglia (support neurons).

Membranes

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

• Function: Protection, secretion, absorption.

Tissue Repair

• Process: Involves inflammation, proliferation, and remodeling.

• Different tissue types: Epithelial tissues regenerate well; connective tissues vary; nervous tissue has limited repair.

Integumentary System

Epidermis

• Cell characteristics: Mainly keratinocytes; also melanocytes, Langerhans cells, Merkel cells.

• Layers (from superficial to deep):

  • Stratum corneum

  • Stratum lucidum (only in thick skin)

  • Stratum granulosum

  • Stratum spinosum

  • Stratum basale

Dermis

• General characteristics/function: Provides strength, elasticity, and houses blood vessels, nerves, and glands.

• Layers:

  • Papillary layer (loose connective tissue)

  • Reticular layer (dense irregular connective tissue)

Pigments Involved in Skin Color

Hair

• Characteristics/functions: Protection, sensation, thermoregulation.

Nails

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

Glands

• Types: Sebaceous (oil), sweat (eccrine and apocrine).

• Functions: Lubrication, thermoregulation, excretion.

Skin Cancer

• General terms: Carcinoma (cancer of epithelial cells), melanoma (cancer of melanocytes).

• Types:

  • Basal cell carcinoma

  • Squamous cell carcinoma

  • Melanoma

Burns

Additional info: Academic context and definitions have been expanded for clarity and completeness.