Human Skeletal System

Comprises 206 bones that provide support, protection, and movement for the body
Divided into two main parts:
- Axial skeleton (80 bones): skull, spine, ribs, and sternum
- Appendicular skeleton (126 bones): upper and lower limbs, pelvis, and shoulder girdle
Functions:
- Supports the body's weight and maintains posture
- Protects internal organs (e.g., brain, heart, lungs)
- Provides attachment points for muscles
- Produces blood cells (in bone marrow)
Types of bones:
- Long bones (e.g., femur, humerus): characterized by length > width
- Short bones (e.g., carpals, tarsals): cube-shaped
- Flat bones (e.g., ribs, sternum): thin and flat
- Irregular bones (e.g., vertebrae, pelvis): complex shapes

Consists of the central nervous system (CNS) and peripheral nervous system (PNS)
- Central nervous system (CNS): brain and spinal cord
  - Controls and integrates body functions
  - Interprets and processes sensory information
- Peripheral nervous system (PNS): nerves that connect CNS to the rest of the body
  - Transmits signals between CNS and muscles, glands, and sensory receptors
Functions:
- Controls movement, sensation, and cognitive functions
- Regulates body temperature, blood pressure, and other autonomic functions
- Enables learning, memory, and emotions
Types of nerve cells:
- Neurons: transmit signals
- Glial cells: provide support and maintenance for neurons

Comprises over 600 muscles that control movement, maintain posture, and regulate body functions
Types of muscles:
- Skeletal muscles (voluntary): attached to bones, responsible for movement
- Smooth muscles (involuntary): found in walls of hollow organs, regulate contraction and relaxation
- Cardiac muscles (involuntary): found in the heart, responsible for heart contraction
Functions:
- Movement and locomotion
- Maintenance of posture and balance
- Regulation of body temperature
- Support for joints and bones
Muscle contraction:
- Involves sliding filament theory: actin and myosin filaments slide past each other to shorten muscle length
- Types of muscle contractions:
  - Isotonic: muscle length changes, force remains constant
  - Isometric: muscle force changes, length remains constant

The human skeletal system comprises 206 bones that provide support, protection, and movement for the body.
It is divided into two main parts: the axial skeleton (80 bones) and the appendicular skeleton (126 bones).
The axial skeleton includes the skull, spine, ribs, and sternum, while the appendicular skeleton includes the upper and lower limbs, pelvis, and shoulder girdle.
The skeletal system has four main functions: supporting the body's weight and maintaining posture, protecting internal organs, providing attachment points for muscles, and producing blood cells in the bone marrow.
There are four main types of bones: long bones, short bones, flat bones, and irregular bones.
Long bones are characterized by their length being greater than their width, whereas short bones are cube-shaped.
Flat bones are thin and flat, and irregular bones have complex shapes.

The nervous system consists of the central nervous system (CNS) and the peripheral nervous system (PNS).
The central nervous system includes the brain and spinal cord, and controls and integrates body functions, interprets and processes sensory information.
The peripheral nervous system includes nerves that connect the CNS to the rest of the body, transmitting signals between the CNS and muscles, glands, and sensory receptors.
The nervous system has three main functions: controlling movement, sensation, and cognitive functions, regulating body temperature, blood pressure, and other autonomic functions, and enabling learning, memory, and emotions.
There are two main types of nerve cells: neurons, which transmit signals, and glial cells, which provide support and maintenance for neurons.

The muscular system comprises over 600 muscles that control movement, maintain posture, and regulate body functions.
There are three main types of muscles: skeletal muscles, smooth muscles, and cardiac muscles.
Skeletal muscles are voluntary and attached to bones, responsible for movement.
Smooth muscles are involuntary and found in the walls of hollow organs, regulating contraction and relaxation.
Cardiac muscles are involuntary and found in the heart, responsible for heart contraction.
The muscular system has four main functions: movement and locomotion, maintenance of posture and balance, regulation of body temperature, and support for joints and bones.
Muscle contraction involves the sliding filament theory, where actin and myosin filaments slide past each other to shorten muscle length.
There are two main types of muscle contractions: isotonic and isometric contractions.
Isotonic contractions involve a change in muscle length, while the force remains constant.
Isometric contractions involve a change in muscle force, while the length remains constant.