Cellular Biology and Functions

Cellular Biology

• Cells are the basic units of life.
• Tissues are groups of cells with similar structure and function (e.g., muscle, neural, epithelial, connective).
• Organs are different tissues working together for a specific function (e.g., heart, brain, kidneys).

Cellular Functions

• Movement: Muscle cells generate force, producing motion (e.g., limb movement, colon contraction).
• Conductivity: Cells respond to stimuli via electrical signals (e.g., nerve cells in the brain and heart).
• Metabolic: Cells use nutrients for energy production.
• Absorption: Cells take in and utilize nutrients.
• Secretion: Cells produce and release substances (e.g., mucous gland cells).
• Excretion: Cells remove waste products (e.g., lysosomes breaking down molecules).
• Respiration: Cells use oxygen to transform nutrients into ATP (energy) (e.g., glucose oxidation in mitochondria).
• Reproduction: Cells reproduce for tissue growth and maintenance (e.g., mitosis and meiosis).
• Communication: Cells communicate to maintain a dynamic, steady state.

Plasma Membranes

• Define cell boundaries, allow or exclude molecules.
• Influence metabolic pathways and maintain cellular shape.
• Driven by proteins: Recognition and binding units (receptors), pores or transport channels, enzymes, cell surface markers (glycoproteins), catalysts of chemical reactions.

Cellular Components

• Nucleus: Largest membrane-bound organelle, controls cell division and genetic information.
• Mitochondria: Numerous in cells, responsible for cellular respiration and ATP production.
• Ribosomes: Sites of protein synthesis, proteins are primary workers and are moved via gated transport, protein translocation, and vesicular transport.

Cellular Adaptations

• Normal cells adapt to stress (atrophy, hypertrophy, hyperplasia, metaplasia).
• Injury occurs if adaptation fails.
• Atrophy: Decrease in cell size.
• Hypertrophy: Increase in cell size.
• Hyperplasia: Increase in cell number.
• Metaplasia: Replacement of one cell type by another (e.g., squamous metaplasia in smoker's lungs.).
• Dysplasia: Atypical hyperplasia (not a true adaptation).

Hypoxia

• Cells lack sufficient oxygen; ischemia (reduced blood supply) is a common cause.
• Negatively impacts all cellular functions.
• Causes: reduced oxygen in air, loss of hemoglobin, decreased red blood cell production, respiratory and cardiovascular diseases, poisoning of cellular oxidative enzymes.
• Consequences: negative impact on normal cellular processes (e.g., differentiation, angiogenesis), production of reactive oxygen species (ROS), oxidative stress, cellular damage, and inflammation.

Hypothalamus

• Functions include autonomic nervous system control, sleep-wake cycle regulation, circadian rhythm control, endocrine function control, food intake control, sexual behavior control, temperature regulation, processing emotional responses, and behaviors related to reward and punishment.

Pain

• Subjective experience involving afferent (ascending) and efferent (descending) pathways.
• Characteristics: Pain threshold (lowest pain intensity), pain tolerance (highest tolerable intensity), acute pain (short duration), chronic pain (>3 months).
• Signs and symptoms: Increased heart rate, respiratory rate, hypertension, diaphoresis, dilated pupils (in children, facial expressions, body rigidity, crying, sleep disorders, resistance to touch).

Fever

• Triggered by pyrogens (from leukocytes, other cells, bacteria).
• Mechanism involves resetting the hypothalamic thermostat (both a symptom and a normal immunologic mechanism).
• Role in healing: increased temperature can kill pathogens, decrease serum iron, zinc, and copper needed for bacterial replication, cause lysosome breakdown, prevent viral replication, enhance immune response (e.g. lymphocytic transformation, neutrophil motility, phagocytosis, interferon production).

Febrile Seizures

• May occur in children with temperature > 38°C.
• Commonly in boys younger than 5 years.
• Often self-limiting.

Nervous System Review

• Central nervous system (CNS): Brain and spinal cord.
• Peripheral nervous system (PNS): Network of neurons connecting the body to the CNS.
• Afferent (sensory neurons): Input from body to CNS.
• Efferent (motor neurons): Output from CNS to body.

Neurological Disorders

• Alzheimer's disease: Severe cognitive dysfunction due to increased beta-protein concentration and the formation of amyloid plaques and neurofibrillary tangles.
• Multiple sclerosis: Progressive, chronic, inflammatory, demyelinating, autoimmune disorder of the CNS.
• Guillain-Barré syndrome: Rare, acquired autoimmune disease affecting the peripheral nervous system (demyelination).
• Myasthenia gravis: Chronic autoimmune disease affecting neuromuscular junction function due to immunoglobulin G (IgG) autoantibodies.
• Parkinson's disease: Degeneration of dopamine-producing neurons in substantia nigra, leading to motor impairments including tremor, rigidity, bradykinesia, and postural issues.
• Cerebrovascular diseases (strokes): Disruption of blood flow in the brain causing ischemia (ischemic stroke) or hemorrhage (hemorrhagic stroke).

Explore the fundamental concepts of cellular biology, including the structure and function of cells, tissues, and organs. This quiz will cover essential cellular functions such as movement, conductivity, metabolism, and more. Test your knowledge on how cells contribute to life and the processes vital for their operation.