Chapter 7: The Muscular System

General Functions and Characteristics of Muscle Tissue

• Muscle tissue is specialized for contraction, enabling movement of the body and its parts.

• Three types of muscle tissue: skeletal (voluntary, striated), cardiac (involuntary, striated), and smooth (involuntary, non-striated).

• All muscle tissues share properties such as excitability, contractility, extensibility, and elasticity.

• Example: Skeletal muscles move bones, cardiac muscle pumps blood, and smooth muscle moves contents through hollow organs.

Structure and Function of Muscle Types

• Skeletal muscle: Long, cylindrical, multinucleated fibers; attached to bones; voluntary control.

• Cardiac muscle: Branched, single nucleus, intercalated discs; found in heart; involuntary control.

• Smooth muscle: Spindle-shaped, single nucleus; found in walls of hollow organs; involuntary control.

• Comparison: Skeletal muscle contracts quickly, cardiac muscle contracts rhythmically, smooth muscle contracts slowly.

Muscle Anatomy and Connective Tissue Components

• Endomysium: Surrounds individual muscle fibers.

• Perimysium: Surrounds bundles of fibers (fascicles).

• Epimysium: Surrounds the entire muscle.

• Tendon: Dense connective tissue connecting muscle to bone.

Microscopic Structure of Skeletal Muscle

• Skeletal muscle fibers contain myofibrils composed of repeating units called sarcomeres.

• Sarcomeres contain actin (thin) and myosin (thick) filaments responsible for contraction.

• Sliding filament theory: Muscle contraction occurs as actin and myosin filaments slide past each other.

Neuromuscular Junction and Muscle Contraction

• The neuromuscular junction is the synapse between a motor neuron and a muscle fiber.

• Release of acetylcholine (ACh) from the neuron triggers an action potential in the muscle cell, leading to contraction.

• Excitation-contraction coupling: The process linking muscle fiber excitation to contraction.

Types of Muscle Contractions

• Graded responses: Variation in muscle contraction strength due to frequency of stimulation and number of fibers activated.

• Twitch: Single, brief contraction.

• Tetanus: Sustained contraction from rapid stimulation.

• Isotonic contraction: Muscle changes length (concentric or eccentric) while tension remains constant.

• Isometric contraction: Muscle tension increases, but length does not change.

Muscle Fatigue and Oxygen Debt

• Muscle fatigue: Inability to contract due to depletion of ATP or accumulation of lactic acid.

• Oxygen debt: Extra oxygen required after exercise to restore metabolic conditions.

• Possible causes: Lack of oxygen, depletion of energy reserves, accumulation of metabolic byproducts.

Muscle Movements and Roles

• Prime mover (agonist): Main muscle responsible for movement.

• Antagonist: Muscle that opposes the action of the prime mover.

• Synergist: Assists the prime mover.

• Fixator: Stabilizes the origin of the prime mover.

Exercise and Muscle Health

• Regular exercise increases muscle strength, endurance, and flexibility.

• Strengthening and conditioning help maintain muscle mass and function with age.

Isotonic vs. Isometric Contractions

• Isotonic: Muscle changes length (movement occurs).

• Isometric: Muscle length remains the same (no movement).

• Example: Lifting a weight (isotonic) vs. holding a weight steady (isometric).

Chapters 8 & 9: The Nervous System

General Functions and Organization

• The nervous system coordinates body activities by transmitting signals between different body parts.

• Divided into central nervous system (CNS) (brain and spinal cord) and peripheral nervous system (PNS) (nerves outside CNS).

• Functions: Sensory input, integration, motor output.

Structure of Neurons and Neuroglia

• Neuron: Basic functional unit; consists of cell body, dendrites, and axon.

• Neuroglia: Support, protect, and nourish neurons (e.g., astrocytes, oligodendrocytes, Schwann cells).

• Gray matter: Contains neuron cell bodies.

• White matter: Contains myelinated axons.

Synapses and Nerve Impulses

• Synapse: Junction between two neurons or a neuron and effector cell.

• Nerve impulse: Electrical signal (action potential) transmitted along axons.

• Impulse transmission involves depolarization and repolarization of the neuron membrane.

Central and Peripheral Nervous Systems

• CNS: Brain and spinal cord; processes and integrates information.

• PNS: Cranial and spinal nerves; transmits signals to and from CNS.

• Somatic nervous system: Controls voluntary movements.

• Autonomic nervous system: Controls involuntary functions; divided into sympathetic and parasympathetic divisions.

Major Brain Regions and Functions

• Cerebrum: Higher brain functions (thought, memory, voluntary movement).

• Diencephalon: Thalamus and hypothalamus; sensory relay and homeostasis.

• Brainstem: Midbrain, pons, medulla oblongata; controls vital functions.

• Cerebellum: Coordinates movement and balance.

Spinal Cord and Reflexes

• Spinal cord: Transmits signals between brain and body; mediates reflexes.

• Reflex arc: Pathway for reflex action, involving sensory neuron, interneuron, and motor neuron.

Autonomic Nervous System

• Sympathetic division: Prepares body for "fight or flight" response.

• Parasympathetic division: Promotes "rest and digest" activities.

• Comparison: Sympathetic increases heart rate, parasympathetic decreases it.

Chapter 10: The Sense Organs

General Structure and Function

• Sense organs detect changes in the environment and relay information to the nervous system.

• Main sense organs: eyes (vision), ears (hearing and equilibrium), nose (smell), tongue (taste), skin (touch).

The Eye and Vision

• Layers of the eye: Sclera (outer), choroid (middle), retina (inner).

• Retina: Contains photoreceptors (rods for dim light, cones for color vision).

• Pathway of light: Cornea → aqueous humor → lens → vitreous humor → retina.

• Common vision problems: Myopia (nearsightedness), hyperopia (farsightedness), astigmatism, presbyopia.

The Ear: Hearing and Equilibrium

• Ear regions: Outer ear (auricle, canal), middle ear (ossicles), inner ear (cochlea, vestibular apparatus).

• Organ of Corti: Located in cochlea; contains hair cells for hearing.

• Equilibrium: Maintained by semicircular canals (dynamic) and vestibule (static).

• Deafness types: Sensorineural (damage to hair cells or nerves), conductive (blockage or damage to middle/outer ear).

Olfaction and Gustation

• Olfactory receptors: Located in nasal cavity; detect airborne chemicals (smell).

• Taste receptors: Located in taste buds on tongue; detect five basic tastes: sweet, sour, salty, bitter, umami.

• Factors modifying taste: Age, health, medications, and environmental factors.

Age-Related Changes in Sense Organs

• With age, sense organs may lose sensitivity (e.g., presbyopia in eyes, presbycusis in ears).

• Decreased number of receptors and slower nerve conduction can affect perception.

Table: Comparison of Muscle Tissue Types

Key Equations

• Sliding Filament Theory:

• Resting Membrane Potential:

• Ohm's Law (for nerve conduction):