Human Body Organization and Cell Physiology

Study Notes

The human body is composed of cells, tissues, organs, and systems.
Cells are the smallest functional units of the body.
A group of cells with similar functions form a tissue.
Primary types of tissues: Muscle, Nervous, Epithelial, and Connective.
Two or more types of tissues come together to form an organ.
Types of organs: Tubular/hollow and Compact/parenchymal.
A group of organs working together to carry out specific functions form a system.

Digestive System: responsible for digestion of food.
Excretory System: responsible for elimination of unwanted substances.
Cardiovascular System: responsible for transport of substances between organs.
Respiratory System: responsible for supply of oxygen and removal of carbon dioxide.
Reproductive System: responsible for reproduction.
Muscoskeletal System: responsible for stability and movement.
Nervous System: controls locomotion and bodily function, including intellectual function.
Endocrine System: responsible for growth and regulation of body functions.

The cell membrane is a semi-permeable and fluid-like structure composed of hydrophobic and hydrophillic components.
The cell membrane has integral proteins that interact with the lipid bilayer to form passive transport pores and channels, active transport pumps and carriers, and membrane-linked enzymes, receptors, and transducers.
Sterols, such as cholesterol, stabilize the lipid bilayer.

Nucleus: contains chromatin, DNA, and a nucleolus.
Mitochondria: responsible for generating energy for the cell through the conversion of food into ATP.
Endoplasmic Reticulum: site where cell membrane and exported materials are made.
Golgi Apparatus: receives and modifies materials, and directs new materials to their destinations.
Lysosomes: responsible for intracellular digestion and breakdown of waste.
Peroxisomes: generate and degrade hydrogen peroxide.
Cytosol: a water-based gel where chemical reactions take place.
Cytoskeleton: composed of filaments, such as actin, intermediate, and microtubules, and provides structure and movement to the cell.

Homeostasis is the ability of the body to maintain a stable internal environment despite changes in the external environment.
Homeostasis is crucial for maintaining health and preventing disease.
The body has mechanisms to regulate various physiological processes, such as heart rate, blood pressure, and body temperature.

The nervous system is composed of the central nervous system (CNS) and peripheral nervous system (PNS).
The CNS consists of the brain and spinal cord, while the PNS consists of nerves that connect the CNS to the rest of the body.
Neurons are the basic units of the nervous system, responsible for transmitting electrical impulses.
Dendrites carry information to the cell body, while the axon sends information to the next unit.

The synapse is the junction between two neurons.
The synapse allows for communication between neurons through the release of neurotransmitters.
Neurotransmitters bind to receptors on the postsynaptic neuron, generating an action potential.

Each sensory system is specialized to detect a specific type of stimulus.
Sensory systems have a specific region of the cortex dedicated to processing information.
There are regions of overlap between sensory systems, known as association areas.

Action potentials are signals transmitted along axons.
Action potentials are generated by a rapid change in the membrane potential of the neuron.
The synapse is the site of transmission of action potentials from one neuron to another.
Neurotransmitters are released from the presynaptic neuron and bind to receptors on the postsynaptic neuron, generating an action potential.

Muscles are responsible for movement and contraction.
The motor unit is the functional unit of the muscle, consisting of a motor neuron and the muscle fibers it innervates.
Muscle contraction is regulated by the frequency of action potentials and the number of functional motor units.