Skeletal Muscles: Structure and Function

Muscles

• There are three types of muscles in the body: skeletal, cardiac, and smooth muscles.
• Skeletal muscles are attached to bones through tendons and have voluntary movement.
• Skeletal muscle structure is composed of bundles of muscle fibers, each containing tubules called myofibrils made of actin and myosin proteins.
• The arrangement of myofibrils creates striated skeletal muscle.
• Skeletal muscles serve various functions, including movement, support, and homeostasis.
• Examples of skeletal muscle conditions include muscular dystrophy, carpal tunnel syndrome, and myasthenia gravis.

Lever Systems

• Lever systems in the body consist of muscles, bones, and joints that provide a mechanical advantage.
• There are four parts of a lever system: a lever (bone), pivot/fulcrum (joint), effort (force generated by muscle contraction), and load (weight moved by the lever).
• The strength of a lever system increases as the force is moved farther away from the load.
• There are three types of lever systems: first-class, second-class, and third-class levers.
• Examples of lever systems in the body include the atlanto-occipital joint (first-class), plantar flexion (second-class), and elbow flexion (third-class).

Basal Metabolic Rate (BMR)

• BMR is the minimum amount of calories required for basic functions at rest.
• BMR is different from Resting Metabolic Rate (RMR).
• Harris and Benedict first published an equation for BMR, which was later revised by Mifflin-St. Jeor.
• BMR is dependent on factors such as temperature, gender, age, and genetics.
• A respirometer can measure an animal's BMR.

Connective Tissue

• Connective tissue supports, protects, and gives structure to other tissues in the body.
• Fibrous connective tissue is composed of sturdy, flexible collagen fibers.
• Types of fibrous connective tissue include ligaments, tendons, and fasciae.
• The Achilles tendon is the largest and strongest tendon in the body.

Glutamine

• Glutamine is one of the 11 non-essential amino acids produced by the human body.
• Glutamine is important during pregnancy, lactation, neonatal growth, and recovery from trauma and chronic illness.
• Glutamine has two amino groups, making it a nitrogen donor and carrier.
• Glutamine is found in dietary sources such as eggs, legumes, and meat products.
• Glutamine deficiency can lead to higher mortality and morbidity rates.

Digestion

• Digestion begins in the mouth and is the breakdown and absorption of food in the body.
• Saliva is a clear liquid produced by salivary glands that contains enzymes to initiate digestion.
• The alimentary canal is the long tube where food passes through and wastes are eliminated.
• Mouth infections can occur if saliva production is inadequate.

Vision

• Photoreceptors (rods and cones) in the retina convert light into electrical signals.
• The optic nerve transmits information from the retina to the brain.
• The brain processes the information to form a picture of what is seen.

Hearing

• The external ear collects sound vibrations and directs them inward.
• The ear canal, or auditory canal, is responsible for collecting sound vibrations.
• The shape and structure of the ear canal amplify and provide details about the vibrations.
• The eardrum, or tympanic membrane, begins to vibrate when air vibrations meet it.
• The vibrations are transferred to the inner ear and become liquid vibrations.
• The cochlea is a tiny curled fluid-filled structure that absorbs the vibrations.
• The movement of microscopic hairs in the cochlea stimulates nerves, creating an electrical signal that travels to the brain.

Cornea

• The cornea is the outermost surface of the eye.
• It is made up of six layers, each serving different functions.
• Minor and severe medical conditions can affect the cornea.
• While minor conditions can be treated with the cornea's self-repair mechanisms, more severe conditions can lead to permanent damage.

Sensitivity to Sound

• Increased sensitivity to sound can be caused by various factors, including fatigue, stress, anxiety, or medical conditions.
• Damage to the facial nerve or brain can lead to increased sensitivity to sound.
• Conditions such as depression, post-traumatic stress disorder, or Williams syndrome may also contribute to increased sensitivity.
• Stress or anxiety can also cause increased sensitivity to sound.

Virology

• Virology is the scientific study of viruses.
• Viruses are small collections of genetic coding with DNA or RNA surrounded by a protective protein coat.
• Viruses can be either small (17 nanometers to 1.5 micrometers) or giant (700 to 1000 nanometers in length).
• Viruses are not considered living because they are not able to reproduce on their own and are metabolically inert.
• Viruses depend on host cells to reproduce and continue infection.

Infections

• Infections are caused by external harmful agents, called pathogens, that invade and cause illness in the body.
• Examples of pathogens include viruses, bacteria, parasites, and prions.
• Infectivity is determined by how effectively a pathogen can cause an infection.
• Diseases are illnesses that arise from perturbations in bodily or biological functions.
• Infectious diseases are caused by pathogens, while noninfectious diseases have different etiologies.

Disordered Eating

• Disordered eating is a pathological and unhealthy pattern to eating.
• Disordered eating can progress to bulimia nervosa, which is an eating disorder.
• Bulimia nervosa is characterized by binge eating and compensatory behavior.
• There are two main subtypes of bulimia nervosa: purging and non-purging.

Dyspnea

• Dyspnea is labored or difficult breathing.
• Dyspnea can be caused by allergic reactions, lung and heart disease, and foreign body aspiration.
• Treatments for dyspnea focus on the underlying disease and may require medical assistance.

Anesthesia

• Anesthesia is medicine used to subdue a patient during medical procedures.
• Anesthesia can be classified into local, regional, and general anesthesia.
• General anesthesia has multiple stages, including the REM stage and the surgical stage.
• Side effects of general anesthesia include lingering numbness, nausea, and fatigue.
• A rare but serious risk of general anesthesia is malignant hyperthermia.

Analgesics

• Analgesics are drugs used to accomplish a state of analgesia, or pain relief.
• Analgesic drugs can be broken down into several groups, based on their uses and functions.
• Examples of analgesic groups include NSAIDs, COX-2 inhibitors, and opioids.

Analgesia

• Analgesia is the relief or reduction of pain through the use of analgesics.
• Analgesics can be classified into OTC medications and opioids.
• Anesthesia is different from analgesia, as it refers to the loss of sensation or even consciousness.
• There are two types of anesthesia: local and general.

Osteology

• Osteology is the scientific study of bones.

• Bones perform an important role by providing structure and protection to the body and its organs.

• Osteology has implications in the fields of medicine, surgery, paleontology, and evolutionary biology.

• The skeletal system of humans is comprised of 206 bones on average.### Human Skeletal System

• The human skeletal system consists of two categories: appendicular bones and axial bones.

• Axial bones are found along the central axis of the body, including the skull and bones of the ribs and sternum.

• The skull is comprised of 22 bones, including 8 neurocranial bones and 14 facial bones.

• The ribs and sternum form the thoracic cage, which protects organs like the heart and lungs.

• The sternum consists of three segments: the manubrium, body, and xiphoid process.

Plant Biology

• Plants are unique in their ability to create chemical energy from light energy through photosynthesis.
• Plant cells are eukaryotic with cell walls made of cellulose.
• Plants can be classified as vascular or nonvascular, based on the presence of xylem and phloem tissues.
• Vascular plants can be further classified as gymnosperms (seed-producing, no flowers) or angiosperms (seed-producing, with flowers).
• Angiosperms can be divided into monocots (one cotyledon, three-petaled flowers, parallel-veined leaves) and dicots (two cotyledons, four- or five-petaled flowers, complex leaves).

Leaf Structure

• Leaves are the primary site of photosynthesis in plants.
• The leaf structure consists of several layers, including the cuticle, upper epidermis, palisade layer, spongy layer, and lower epidermis.
• The palisade layer is where most photosynthesis takes place.
• The spongy layer stores photosynthetic products and contains vascular bundles.
• The lower epidermis is responsible for gas exchange and transpiration through stomata controlled by guard cells.

Muscles

• There are three types of muscles in the body: skeletal, cardiac, and smooth muscles.
• Skeletal muscles are attached to bones through tendons and have voluntary movement.
• Skeletal muscle structure is composed of bundles of muscle fibers, each containing tubules called myofibrils made of actin and myosin proteins.
• The arrangement of myofibrils creates striated skeletal muscle.
• Skeletal muscles serve various functions, including movement, support, and homeostasis.
• Examples of skeletal muscle conditions include muscular dystrophy, carpal tunnel syndrome, and myasthenia gravis.

Lever Systems

• Lever systems in the body consist of muscles, bones, and joints that provide a mechanical advantage.
• There are four parts of a lever system: a lever (bone), pivot/fulcrum (joint), effort (force generated by muscle contraction), and load (weight moved by the lever).
• The strength of a lever system increases as the force is moved farther away from the load.
• There are three types of lever systems: first-class, second-class, and third-class levers.
• Examples of lever systems in the body include the atlanto-occipital joint (first-class), plantar flexion (second-class), and elbow flexion (third-class).

Basal Metabolic Rate (BMR)

• BMR is the minimum amount of calories required for basic functions at rest.
• BMR is different from Resting Metabolic Rate (RMR).
• Harris and Benedict first published an equation for BMR, which was later revised by Mifflin-St. Jeor.
• BMR is dependent on factors such as temperature, gender, age, and genetics.
• A respirometer can measure an animal's BMR.

Connective Tissue

• Connective tissue supports, protects, and gives structure to other tissues in the body.
• Fibrous connective tissue is composed of sturdy, flexible collagen fibers.
• Types of fibrous connective tissue include ligaments, tendons, and fasciae.
• The Achilles tendon is the largest and strongest tendon in the body.

Glutamine

• Glutamine is one of the 11 non-essential amino acids produced by the human body.
• Glutamine is important during pregnancy, lactation, neonatal growth, and recovery from trauma and chronic illness.
• Glutamine has two amino groups, making it a nitrogen donor and carrier.
• Glutamine is found in dietary sources such as eggs, legumes, and meat products.
• Glutamine deficiency can lead to higher mortality and morbidity rates.

Digestion

• Digestion begins in the mouth and is the breakdown and absorption of food in the body.
• Saliva is a clear liquid produced by salivary glands that contains enzymes to initiate digestion.
• The alimentary canal is the long tube where food passes through and wastes are eliminated.
• Mouth infections can occur if saliva production is inadequate.

Vision

• Photoreceptors (rods and cones) in the retina convert light into electrical signals.
• The optic nerve transmits information from the retina to the brain.
• The brain processes the information to form a picture of what is seen.

Hearing

• The external ear collects sound vibrations and directs them inward.
• The ear canal, or auditory canal, is responsible for collecting sound vibrations.
• The shape and structure of the ear canal amplify and provide details about the vibrations.
• The eardrum, or tympanic membrane, begins to vibrate when air vibrations meet it.
• The vibrations are transferred to the inner ear and become liquid vibrations.
• The cochlea is a tiny curled fluid-filled structure that absorbs the vibrations.
• The movement of microscopic hairs in the cochlea stimulates nerves, creating an electrical signal that travels to the brain.

Cornea

• The cornea is the outermost surface of the eye.
• It is made up of six layers, each serving different functions.
• Minor and severe medical conditions can affect the cornea.
• While minor conditions can be treated with the cornea's self-repair mechanisms, more severe conditions can lead to permanent damage.

Sensitivity to Sound

• Increased sensitivity to sound can be caused by various factors, including fatigue, stress, anxiety, or medical conditions.
• Damage to the facial nerve or brain can lead to increased sensitivity to sound.
• Conditions such as depression, post-traumatic stress disorder, or Williams syndrome may also contribute to increased sensitivity.
• Stress or anxiety can also cause increased sensitivity to sound.

Virology

• Virology is the scientific study of viruses.
• Viruses are small collections of genetic coding with DNA or RNA surrounded by a protective protein coat.
• Viruses can be either small (17 nanometers to 1.5 micrometers) or giant (700 to 1000 nanometers in length).
• Viruses are not considered living because they are not able to reproduce on their own and are metabolically inert.
• Viruses depend on host cells to reproduce and continue infection.

Infections

• Infections are caused by external harmful agents, called pathogens, that invade and cause illness in the body.
• Examples of pathogens include viruses, bacteria, parasites, and prions.
• Infectivity is determined by how effectively a pathogen can cause an infection.
• Diseases are illnesses that arise from perturbations in bodily or biological functions.
• Infectious diseases are caused by pathogens, while noninfectious diseases have different etiologies.

Disordered Eating

• Disordered eating is a pathological and unhealthy pattern to eating.
• Disordered eating can progress to bulimia nervosa, which is an eating disorder.
• Bulimia nervosa is characterized by binge eating and compensatory behavior.
• There are two main subtypes of bulimia nervosa: purging and non-purging.

Dyspnea

• Dyspnea is labored or difficult breathing.
• Dyspnea can be caused by allergic reactions, lung and heart disease, and foreign body aspiration.
• Treatments for dyspnea focus on the underlying disease and may require medical assistance.

Anesthesia

• Anesthesia is medicine used to subdue a patient during medical procedures.
• Anesthesia can be classified into local, regional, and general anesthesia.
• General anesthesia has multiple stages, including the REM stage and the surgical stage.
• Side effects of general anesthesia include lingering numbness, nausea, and fatigue.
• A rare but serious risk of general anesthesia is malignant hyperthermia.

Analgesics

• Analgesics are drugs used to accomplish a state of analgesia, or pain relief.
• Analgesic drugs can be broken down into several groups, based on their uses and functions.
• Examples of analgesic groups include NSAIDs, COX-2 inhibitors, and opioids.

Analgesia

• Analgesia is the relief or reduction of pain through the use of analgesics.
• Analgesics can be classified into OTC medications and opioids.
• Anesthesia is different from analgesia, as it refers to the loss of sensation or even consciousness.
• There are two types of anesthesia: local and general.

Osteology

• Osteology is the scientific study of bones.

• Bones perform an important role by providing structure and protection to the body and its organs.

• Osteology has implications in the fields of medicine, surgery, paleontology, and evolutionary biology.

• The skeletal system of humans is comprised of 206 bones on average.### Human Skeletal System

• The human skeletal system consists of two categories: appendicular bones and axial bones.

• Axial bones are found along the central axis of the body, including the skull and bones of the ribs and sternum.

• The skull is comprised of 22 bones, including 8 neurocranial bones and 14 facial bones.

• The ribs and sternum form the thoracic cage, which protects organs like the heart and lungs.

• The sternum consists of three segments: the manubrium, body, and xiphoid process.

Plant Biology

• Plants are unique in their ability to create chemical energy from light energy through photosynthesis.
• Plant cells are eukaryotic with cell walls made of cellulose.
• Plants can be classified as vascular or nonvascular, based on the presence of xylem and phloem tissues.
• Vascular plants can be further classified as gymnosperms (seed-producing, no flowers) or angiosperms (seed-producing, with flowers).
• Angiosperms can be divided into monocots (one cotyledon, three-petaled flowers, parallel-veined leaves) and dicots (two cotyledons, four- or five-petaled flowers, complex leaves).

Leaf Structure

• Leaves are the primary site of photosynthesis in plants.
• The leaf structure consists of several layers, including the cuticle, upper epidermis, palisade layer, spongy layer, and lower epidermis.
• The palisade layer is where most photosynthesis takes place.
• The spongy layer stores photosynthetic products and contains vascular bundles.
• The lower epidermis is responsible for gas exchange and transpiration through stomata controlled by guard cells.