Chapter 1: Specialized Cell/Tissue Types and Homeostasis

Specialized Cell and Tissue Types

There are four main types of specialized cells/tissues in the human body, each with distinct functions:

• Nervous tissue: Specialized for communication via electrical and chemical signals.

• Muscle tissue: Responsible for movement and force generation.

• Epithelial tissue: Covers body surfaces, lines cavities, and forms glands; involved in protection, absorption, and secretion.

• Connective tissue: Provides support, binds tissues, and stores energy; includes bone, blood, and adipose tissue.

Fluid Compartments and Boundaries

The body contains distinct fluid compartments:

• Intracellular fluid (ICF): Fluid within cells.

• Extracellular fluid (ECF): Fluid outside cells, including interstitial fluid (between cells) and plasma (in blood vessels).

Boundaries: The cell membrane separates ICF from ECF; capillary walls separate plasma from interstitial fluid.

Homeostasis and Feedback Mechanisms

Homeostasis is the maintenance of a stable internal environment. It is regulated by feedback loops:

• Negative feedback: Counteracts changes, returning variables to a set point (e.g., body temperature regulation).

• Positive feedback: Amplifies changes, moving the system away from a set point (e.g., blood clotting).

Variables: Regulated variables include temperature, pH, and ion concentrations.

Key Terms Table

Chapter 4: Epithelial Transport and Gradients

Epithelial Transport

Epithelial cells regulate the movement of water and solutes across barriers. Transport can be passive (diffusion, osmosis) or active (requiring energy).

• Passive transport: Movement down a concentration gradient (e.g., diffusion, osmosis).

• Active transport: Movement against a gradient, requiring ATP (e.g., Na+/K+ pump).

Concentration and Electrochemical Gradients

Gradients drive the movement of ions and molecules:

• Concentration gradient: Difference in solute concentration across a membrane.

• Electrochemical gradient: Combined effect of concentration and electrical charge differences.

Highest concentrations: Na+ and Cl- are higher outside the cell; K+ is higher inside.

Osmosis and Tonicity

Osmosis is the diffusion of water across a semipermeable membrane. Tonicity describes the effect of a solution on cell volume:

• Isotonic: No net water movement; cell volume remains constant.

• Hypotonic: Water enters cell; cell swells.

• Hypertonic: Water leaves cell; cell shrinks.

Membrane Potential

The resting membrane potential is the voltage difference across the cell membrane, mainly due to Na+ and K+ gradients.

Additional info: The Nernst equation above gives the equilibrium potential for a single ion.

Chapter 5: Chemical Messengers and Signal Transduction

Types of Chemical Messengers

Chemical messengers mediate communication between cells:

• Paracrine: Acts on nearby cells.

• Autocrine: Acts on the same cell that secreted it.

• Endocrine: Hormones travel via blood to distant targets.

• Neurotransmitters: Released by neurons to act on adjacent cells.

Lipophilic vs. Lipophobic Messengers

• Lipophilic: Can cross cell membranes; receptors are often intracellular (e.g., steroid hormones).

• Lipophobic: Cannot cross membranes easily; receptors are on the cell surface (e.g., peptide hormones).

Signal Transduction and Amplification

Signal transduction involves converting a chemical signal into a cellular response, often with amplification via second messengers (e.g., cAMP, Ca2+).

Key Terms Table

Chapter 6: Endocrine System and Hormone Action

Endocrine Organs and Hormones

The endocrine system consists of glands that secrete hormones into the bloodstream to regulate body functions.

• Primary endocrine organs: Pituitary, thyroid, adrenal glands, pancreas, etc.

• Hormones: Chemical messengers that regulate physiology and behavior.

Hormone Interactions

• Synergism: Two hormones produce a greater effect together.

• Permissiveness: One hormone enables another to act.

• Antagonism: One hormone opposes the action of another.

Hormone Disorders

• Primary disorder: Problem in the gland that produces the hormone.

• Secondary disorder: Problem in the regulatory pathway (e.g., pituitary or hypothalamus).

Key Terms Table

Chapter 7: Nervous System Structure and Function

Neurons and Action Potentials

Neurons are specialized cells for communication. They generate electrical signals called action potentials.

• Graded potential: Local change in membrane potential; can lead to action potential if threshold is reached.

• Action potential: Rapid, all-or-none electrical signal along the axon.

Synapses and Neurotransmitters

Synapses are junctions where neurons communicate. Neurotransmitters are released from presynaptic neurons and bind to receptors on postsynaptic cells.

• Excitatory neurotransmitters: Increase likelihood of action potential (e.g., glutamate).

• Inhibitory neurotransmitters: Decrease likelihood (e.g., GABA).

Key Terms Table

Chapter 9: Central Nervous System (CNS) Organization

Gray and White Matter

Gray matter contains neuron cell bodies; white matter contains myelinated axons. Organization varies in brain and spinal cord.

Brain and Spinal Cord Structure

• Cerebrum: Higher brain functions (thought, memory, voluntary movement).

• Cerebellum: Coordination and balance.

• Brainstem: Basic life functions (breathing, heart rate).

Cerebrospinal fluid (CSF): Cushions brain and spinal cord; produced by choroid plexus and recycled via arachnoid villi.

Key Terms Table

Chapters 10 & 11: Sensory Receptors and Somatosensory System

Types and Classes of Sensory Receptors

Sensory receptors detect specific types of stimuli:

• Photoreceptors: Light (vision)

• Mechanoreceptors: Touch, pressure, vibration

• Thermoreceptors: Temperature

• Nociceptors: Pain

• Proprioceptors: Body position

Somatosensory Pathways

Somatosensory pathways transmit information from receptors to the CNS, where it is processed and interpreted.

Autonomic Nervous System

The autonomic nervous system (ANS) regulates involuntary functions. It has two divisions:

• Sympathetic: Prepares body for 'fight or flight'

• Parasympathetic: Promotes 'rest and digest'

Key Terms Table