Understanding Muscle Types and Contraction Mechanisms
Striated Muscle Characteristics
Light microscopy reveals that both skeletal and cardiac muscle fibers exhibit alternating light and dark bands, or striations. These bands change relative size during contraction. Striated muscle fibers contract rapidly but fatigue easily; they require periods of rest before contracting again.
Cardiac Muscle Details
Located in the walls of the heart, cardiac muscle is involuntary, controlled by the autonomic nervous system. Its fibers are joined end-to-end, branching
Read MoreHuman Body Systems: Muscles, Skeleton, Anatomy, Circulation
Human Body Systems Fundamentals
Muscular System Basics
Muscle Types
- Skeletal: Striated, voluntary, multinucleated.
- Smooth: Non-striated, involuntary, single-nucleated.
- Cardiac: Striated, involuntary, single/binucleated.
Muscle Properties
- Contractility: Shortens with stimulation.
- Extensibility: Stretches without damage.
- Elasticity: Returns to original shape.
Muscle Fiber Types
- Slow-Twitch (Type I): Endurance, aerobic.
- Fast-Twitch (Type II): Quick, anaerobic (Type IIa, Type IIb).
Muscle Contraction Mechanism
Contraction:
Read MoreMuscle Physiology: Contraction, Fatigue, and Fiber Types
Muscle Fatigue
Muscle Fatigue: Muscle Damage (high tension), Substrate Depletion (CrP depletion for highly-intense exercise), Metabolite build up
Muscle Fiber Types and Metabolism
Twitch Velocity: Speed of contraction
- Fast Fiber: Contracts quickly
- Slow Fiber: Contracts Slowly
Metabolic: How ATP is replenished
- Oxidative: Lots of mitochondria & capillaries
- Glycolytic: Anaerobic, uses stored glycogen
- Slow-oxidative fibers: Smaller & slow contract velocity, fatigue resistant
- Fast-oxidative glycolytic:
Understanding Muscles: Types, Properties, and Function
Muscles: The Engine of Movement
Muscles are the active part of the locomotor system, soft organs responsible for bodily movement. They are susceptible to stimuli and have the ability to contract and relax.
Muscle Properties
- Excitability: The ability to react to stimuli received from the motor nerve.
- Conductivity: The power of a fiber to transmit electrical impulses via depolarization of the cell membrane.
- Elasticity: The ability of the fiber to recover its original shape.
- Contractility: The ability to
Lipids: Structure, Properties, and Biological Roles
Lipids: An Overview
Lipids are a diverse group of biomolecules characterized by their insolubility in water and solubility in nonpolar solvents. They are primarily composed of carbon, hydrogen, and oxygen, with a lower proportion of oxygen compared to carbohydrates. Some lipids also contain phosphorus, nitrogen, or sulfur.
Classification of Lipids
Lipids can be broadly classified into two categories:
- Saponifiable Lipids: These lipids can be hydrolyzed by alkali (e.g., NaOH) to yield soap. Examples include:
Hormone Pathways: Adrenal Insufficiency, Thyroid, and Diabetes
Corticotropin-Releasing Hormone (CRH) – Adrenocorticotropic Hormone (ACTH) – Cortisol Pathway
Adrenal Insufficiency (Cortisol Hyposecretion)
Because cortisol is needed to permit cardiovascular action of epinephrine, and decreased aldosterone secretion increases sodium/water loss, this can lead to hypotension.
Because cortisol promotes the release of glucose into the bloodstream, this can lead to hypoglycemia.
Primary Adrenal Insufficiency (Addison’s Disease): Loss of adrenal cortisol function due