Anatomy & Physiology Study Guide: Skeletal, Muscular, and Nervous Systems

Skeletal System

Types and Functions of Cartilage

Cartilage is a specialized connective tissue that provides support, flexibility, and resilience in various parts of the body. There are three main types: hyaline cartilage, elastic cartilage, and fibrocartilage.

• Hyaline cartilage: Maintains the shape of a structure while allowing great flexibility.

• Fibrocartilage: Resists compression and provides great tensile strength.

• Elastic cartilage: Provides support with flexibility and resilience.

Locations of Cartilage Types in the Body

Type of cartilage	Location in the body
Hyaline cartilage	Covers the ends of most bones at movable joints
Elastic cartilage	The cartilage of the external ear; forms the epiglottis
Hyaline cartilage	The cartilages that support the external nose
Fibrocartilage	Disc of cartilage that joins the hip bones anteriorly; menisci of the knee joint
Hyaline cartilage	Costal cartilage that connects a rib to the sternum (breastbone)
Elastic cartilage	Forms the epiglottis (the flap that bends to cover the larynx)
Hyaline cartilage	Cartilage that reinforces the walls of the trachea

Functions of Skeleton and Bone Tissue

• Support: Provides a framework for the body and supports soft tissues.

• Protection: Protects vital organs (e.g., skull protects the brain, rib cage protects the heart and lungs).

• Movement: Acts as levers for muscles to produce movement.

• Mineral storage: Stores minerals such as calcium and phosphorus.

• Blood cell formation: Houses bone marrow, which produces blood cells (hematopoiesis).

• Triglyceride storage: Stores fat in yellow bone marrow.

• Hormone production: Produces osteocalcin, which helps regulate bone formation and protects against obesity and diabetes.

Bone Structure and Cells

Bones are composed of compact and spongy bone tissue, each with distinct structures and functions.

• Osteons: Structural units of compact bone, consisting of concentric lamellae around a central canal.

• Trabeculae: Needle-like or flat pieces of bone in spongy bone, forming a honeycomb structure.

• Osteocytes: Mature bone cells that monitor and maintain bone matrix.

• Canaliculi: Tiny canals filled with tissue fluid and extensions of bone cells, allowing communication between osteocytes.

• Lacunae: Chambers that contain mature bone cells.

• Osteoblasts: Bone-forming cells that secrete bone matrix.

• Osteoclasts: Cells that resorb (break down) bone.

Types of Bone Fractures

Type of Fracture	Description
Spiral fracture	Bone breaks due to excessive twisting forces; common in sports injuries.
Compression fracture	Bone is crushed; common in the vertebral column.
Depressed fracture	Broken bone portion is pressed inward; typical of skull fractures.
Greenstick fracture	Bone breaks incompletely; common in children.
Comminuted fracture	Bone fragments into three or more pieces; more common in older adults.
Epiphyseal fracture	End of a long bone separates from the shaft; tends to occur where cartilage cells are dying and calcification of the matrix is occurring.

Bone Disorders

Bone disorder	Descriptive phrases
Osteoporosis	Bone resorption outpaces bone deposit resulting in decreased bone density throughout the skeleton; more common in postmenopausal females.
Paget's Disease	Excessive and abnormal bone deposit and resorption results in bone with an abnormally high ratio of spongy bone to compact bone; usually a localized condition.
Rickets	Bones are soft and weak; disorder in children in which bowed legs and deformities of the pelvis, skull, and rib cage are common.
Osteomalacia	Bones are poorly mineralized; caused by insufficient calcium in the diet or by a vitamin D deficiency.

Muscular System

Functions of Skeletal Muscle Tissue

• Movement: Responsible for voluntary movements of the body.

• Posture maintenance: Maintains body posture and position.

• Joint stabilization: Stabilizes joints during movement.

• Heat generation: Produces heat as a byproduct of muscle activity.

Muscle Proteins and Their Functions

• Myosin: Makes up most of the thick filament; binds calcium ions.

• Actin: Makes up most of the thin filament.

• Troponin: Binds calcium ions; regulates muscle contraction.

• Tropomyosin: Blocks binding sites on the thin filament.

Muscle Contraction Cycle

The cross bridge cycle is the process by which muscles contract at the molecular level.

1. Cross bridge formation: Myosin head attaches to actin.

2. Power stroke: Myosin head pivots, pulling actin filament toward the center.

3. Cross bridge detachment: ATP binds to myosin, causing it to detach from actin.

4. Cocking of myosin head: ATP is hydrolyzed, re-energizing the myosin head.

Types of Muscle Contractions

• Isometric contraction: Muscle does not change in length; load is not moved.

• Isotonic contraction: Muscle changes in length; load is moved.

Aerobic vs. Resistance Exercise Effects

	Aerobic exercise	Resistance exercise
Increase in muscle strength and size		X
Increase number of capillaries surrounding muscle fibers	X
Conversion of fast oxidative fibers to fast glycolytic fibers		X
Conversion of fast glycolytic fibers into fast oxidative fibers	X
Increase in muscle endurance	X

Types of Muscle Tissue

• Skeletal muscle: Voluntary, striated, attached to bones.

• Cardiac muscle: Involuntary, striated, found in the heart.

• Smooth muscle: Involuntary, non-striated, found in walls of hollow organs.

Nervous System

Major Functions of the Nervous System

• Sensory input: Receives information from sensory receptors.

• Integration: Processes and interprets sensory input and decides what should be done.

• Motor output: Activates effector organs (muscles and glands) to cause a response.

Central and Peripheral Nervous System

• CNS (Central Nervous System): Consists of the brain and spinal cord; responsible for integration and command.

• PNS (Peripheral Nervous System): Consists of nerves outside the CNS; transmits signals between the CNS and the rest of the body.

Neuroglia (Glial Cells) and Their Functions

• Ependymal cells: Line cerebrospinal fluid-filled CNS cavities.

• Schwann cells: Form myelin sheaths around PNS nerve fibers.

• Microglia: Defensive cells in the CNS; engulf microorganisms and debris.

• Satellite cells: Surround and support neuron cell bodies in the PNS.

• Astrocytes: Assist in exchanges between blood capillaries and CNS neurons.

• Oligodendrocytes: Form myelin sheaths around CNS nerve fibers.

Neuron Structure and Function

• Cell body (soma): Contains the nucleus and most organelles.

• Dendrites: Receive information from other neurons.

• Axon: Generates and transmits nerve impulses.

Classification of Neurons

• Motor neurons: Transmit impulses from the CNS to muscles or glands.

• Sensory neurons: Transmit impulses from receptors in the skin or internal organs toward the CNS.

• Interneurons: Also called association neurons; connect sensory and motor neurons within the CNS.

Membrane Channels and Action Potentials

• Chemically gated channels: Open when a neurotransmitter binds.

• Voltage-gated channels: Open and close in response to changes in membrane potential.

• Mechanically gated channels: Open in response to physical deformation of the receptor.

• Leakage channels: Always open, allowing ions to move along their gradient.

Action Potential Generation

• Action potential starts at the axon hillock and propagates along the axon.

• Nodes of Ranvier allow for saltatory conduction, increasing the speed of action potential transmission.

Equations and Formulas

• Nernst Equation: Used to calculate the equilibrium potential for an ion: $E_{ion} = \frac{RT}{zF} \ln \left( \frac{[ion]_{out}}{[ion]_{in}} \right)$

• Ohm's Law (for membrane potential): $V = IR$

Additional info:

• Some content inferred for completeness, such as the full list of bone functions and the effects of exercise on muscle fibers.

• Tables reconstructed and expanded for clarity and academic context.