Essential Concepts in Anatomy & Physiology: Study Guide

Homeostasis and Feedback Loops

Role of Feedback Loops in the Body

Feedback loops are fundamental mechanisms that help maintain the body's internal environment within stable limits, a process known as homeostasis.

• Maintaining stability and balance: Feedback loops detect changes and initiate responses to restore equilibrium.

• Types: Negative feedback (most common, reduces deviation) and positive feedback (amplifies changes).

• Example: Regulation of body temperature and blood glucose levels.

Biomolecules and Their Functions

Structure and Classification of Biomolecules

Biomolecules are organic compounds essential for life, classified based on their structure and function.

• Fatty acids: Have lengthy chains of hydrocarbons linked to a carboxyl group (R-COOH).

• Amino acids: Building blocks of proteins, contain amino and carboxyl groups but not lengthy hydrocarbon chains.

• Carbohydrates: Composed of monosaccharides, provide energy.

• Nucleic acids: DNA and RNA, store genetic information.

• Example: Palmitic acid is a fatty acid with a long hydrocarbon chain.

Genetic Code and Central Dogma

The genetic code is the set of rules by which information encoded in DNA is translated into proteins.

• Nucleotides: The building blocks of the genetic code; each consists of a sugar, phosphate, and nitrogenous base.

• Central Dogma: Describes the flow of genetic information: DNA → RNA → Protein.

• Equation: $\text{DNA} \xrightarrow{\text{transcription}} \text{RNA} \xrightarrow{\text{translation}} \text{Protein}$

• Example: mRNA is transcribed from DNA and then translated into a polypeptide.

Enzymes and Inhibition

Enzyme Activity and Inhibitors

Enzymes are biological catalysts that speed up chemical reactions. Their activity can be inhibited by various substances.

• Inhibitors: Substances like Zn2+ can bind to enzymes and reduce their activity.

• Types of inhibition: Competitive, non-competitive, and uncompetitive.

• Example: Heavy metals such as zinc can act as non-competitive inhibitors.

Cellular Respiration and Electron Transport Chain

Electron Carriers in Mitochondria

The electron transport chain (ETC) is a series of protein complexes in mitochondria that transfer electrons to produce ATP.

• Sequence: NADH Dehydrogenase → Ubiquinone → Cytochrome bc1 Complex → Cytochrome c → Cytochrome c Oxidase

• Function: Each carrier passes electrons, pumping protons to generate a gradient for ATP synthesis.

• Equation: $\text{NADH} + \text{H}^+ + \text{O}_2 \rightarrow \text{NAD}^+ + \text{H}_2\text{O}$

Membrane Transport

Primary Active Transport

Primary active transport moves substances against their concentration gradient using energy, typically from ATP.

• Necessary components: Semipermeable membrane, energy source, concentration gradient.

• Carrier proteins: Not always required for primary active transport (e.g., some pumps use channels).

• Example: Sodium-potassium pump ($\text{Na}^+/\text{K}^+$-ATPase).

Endocrine System and Hormones

Hormones Involved in Immune Function

The endocrine system produces hormones that regulate various body functions, including immunity.

• Thymosin: Produced by the thymus, essential for T-cell development and immune response.

• Other hormones: Aldosterone (regulates sodium), dopamine (neurotransmitter), insulin (regulates glucose).

Cardiac Physiology

Pacemaker Cells and Action Potentials

Cardiac muscle cells can generate action potentials spontaneously due to specialized cells called pacemaker cells.

• Pacemaker cells: Located in the sinoatrial (SA) node, initiate heartbeats without external input.

• Other cells: Bundle of His, Purkinje fibers, and AV node cells conduct impulses but do not initiate them.

Nervous System Structure and Function

Axon Characteristics

Axons are long, slender projections of neurons that transmit electrical impulses.

• Structure: Typically appear as long, unbranched fibers, not short branches.

• Function: Conduct signals away from the neuron's cell body.

Sensation vs. Perception

Sensation and perception are distinct processes in the nervous system.

• Sensation: Receiving sensory information from the environment.

• Perception: The physiological response and interpretation of sensory input.

• Example: Feeling heat (sensation) and recognizing it as dangerous (perception).

Autonomic Nervous System

The autonomic nervous system controls involuntary bodily functions.

• Sympathetic division: Prepares the body for 'fight or flight' responses.

• Parasympathetic division: Promotes 'rest and digest' activities, including salivation.

• Example: Salivation in response to food stimuli is typically mediated by the parasympathetic system.

• Additional info: The question's answer may be incorrect; salivation is usually parasympathetic, not sympathetic.

Muscle Physiology

Muscle Contraction Cycle

Muscle contraction involves a series of steps that allow actin and myosin filaments to interact.

• Order: Active-site exposure → Cross-bridge formation → Myosin head pivoting → Cross-bridge detachment → Myosin reactivation

• Equation: $\text{ATP} + \text{Myosin} \rightarrow \text{Myosin-ATP} \rightarrow \text{Myosin-ADP} + \text{P}_i$

• Example: Skeletal muscle contraction during movement.

Reflex Arcs

Integration Center for Reflexes

Reflex arcs are neural pathways that mediate automatic responses to stimuli.

• Spinal cord: The main integration center where afferent neurons synapse with interneurons.

• Additional info: The quadriceps muscle is the effector, not the integration center.

Endocrine Regulation of Blood Glucose

Insulin and Glucagon Secretion

Blood glucose levels are regulated by hormones secreted by the pancreas.

• Pancreas: Secretes insulin (lowers glucose) and glucagon (raises glucose).

• Liver: Stores and releases glucose but does not secrete these hormones.

Major Veins of the Arm

Basilic Vein

The basilic vein is a major superficial vein of the upper limb.

• Location: Runs along the medial side of the arm.

• Function: Drains blood from the hand and forearm to the axillary vein.

Renal Physiology

Podocytes in the Glomerulus

Podocytes are specialized cells in the kidney's glomerulus that play a key role in filtration.

• Foot processes: Long extensions that interdigitate to form filtration slits.

• Function: Formation of a tight membrane around the glomerulus, essential for selective filtration.

Developmental Physiology

Infant Skin Characteristics

Infant skin appears 'dewy' due to physiological differences compared to adults.

• High body water content: Main reason for the appearance of dewy skin.

• Low bone mass: Not directly related to skin appearance.

Cardiac Electrophysiology

Atrial Flutter and ECG Findings

Atrial flutter is a type of arrhythmia detectable on an electrocardiogram (ECG).

• ECG characteristics: Sawtooth-shaped P waves are typical; inverted T waves may indicate other abnormalities.

• Additional info: The correct ECG finding for atrial flutter is sawtooth-shaped P waves.

Summary Table: Key Concepts

Topic	Key Point	Example/Application
Homeostasis	Feedback loops maintain stability	Body temperature regulation
Biomolecules	Fatty acids have long hydrocarbon chains	Palmitic acid
Genetic Code	Nucleotides are building blocks	DNA, RNA
Enzyme Inhibition	Zn2+ inhibits enzymes	Heavy metal toxicity
Electron Transport	NADH → Ubiquinone → Cytochrome bc1 → Cytochrome c → Oxidase	ATP synthesis
Endocrine System	Thymosin regulates immunity	T-cell development
Cardiac Physiology	Pacemaker cells generate action potentials	SA node
Muscle Contraction	Active-site exposure → Cross-bridge formation → Pivoting → Detachment → Reactivation	Skeletal muscle movement
Renal Physiology	Podocytes form filtration membrane	Glomerular filtration