Anatomy & Physiology I: Skeletal System

Bone functions

Support, protection, movement, mineral storage, blood cell production

Osteoblasts

Build bone

Osteoclasts

Break down bone

Osteocytes

Maintain bone

Compact bone

Dense outer layer

Spongy bone

Porous inner layer

Osteon

Functional unit of compact bone

Central canal

Contains blood vessels and nerves

Bone matrix

Collagen + calcium salts

Endochondral ossification

Bone forms from cartilage

Intramembranous ossification

Bone forms directly from connective tissue

Epiphyseal plate

Growth plate in long bones

Epiphyseal line

Remnant after growth stops

Axial skeleton

Skull, vertebral column, ribs

Appendicular skeleton

Limbs and girdles

Types of bones

Long, short, flat, irregular, sesamoid

Joint (articulation)

Point where bones meet

Synarthrosis

Immovable joint

Amphiarthrosis

Slightly movable

Diarthrosis

Freely movable (synovial)

Synovial joint features

Joint cavity, synovial fluid, cartilage

Ligaments

Bone to bone

Tendons

Muscle to bone

Muscle tissue types

Skeletal, cardiac, smooth

Skeletal muscle

Voluntary, striated

Cardiac muscle

Involuntary, striated, heart only

Smooth muscle

Involuntary, non-striated

Muscle function

Movement, posture, heat production

Sarcomere

Functional unit of muscle

Actin

Thin filament

Myosin

Thick filament

Sliding filament theory

Actin and myosin slide to shorten muscle

Neuromuscular junction

Connection between neuron and muscle

Acetylcholine (ACh)

Neurotransmitter that stimulates muscle contraction

Calcium role in contraction

Exposes binding sites on actin

ATP role in muscle

Energy for contraction and detachment

Muscle contraction steps

Stimulus → Ca²⁺ release → cross-bridge → contraction

Origin

Fixed muscle attachment

Insertion

Movable attachment

Agonist

Primary muscle mover

Antagonist

Opposes movement

Types of contractions

Isometric, concentric, eccentric

Isometric

Tension without movement

Concentric

Muscle shortens

Eccentric

Muscle lengthens

Nervous system function

Control and communication

Central nervous system (CNS)

Brain and spinal cord

Peripheral nervous system (PNS)

Nerves outside CNS

Neuron

Basic functional unit of nervous system

Dendrites

Receive signals

Axon

Sends signals

Myelin sheath

Insulates axon, speeds conduction

Action potential

Electrical signal along neuron

Resting membrane potential

~ -70 mV

Depolarization

Na+ enters cell

Repolarization

K+ leaves cell

Synapse

Communication between neurons

Sensory neurons

Carry info to CNS

Motor neurons

Carry info from CNS

Somatic nervous system

Voluntary control

Autonomic nervous system

Involuntary control

Sympathetic

"Fight or flight"

Parasympathetic

"Rest and digest"

Reflex

Rapid automatic response

Spinal cord function

Signal transmission and reflexes

Brain regions

Cerebrum, cerebellum, brainstem

Cerebrum

Thinking, memory, voluntary movement

Cerebellum

Balance and coordination

Brainstem

Vital functions (breathing, heart rate)

Meninges

Protective coverings of brain/spinal cord

Cerebrospinal fluid (CSF)

Cushions CNS

Homeostatic feedback

Negative feedback maintains balance

Negative feedback

Reverses change

Positive feedback

Enhances change