Comprehensive Study Guide: Exam 3 Prep for Anatomy & Physiology

Anatomical Position and Skeletal Orientation

Understanding Anatomical Position

The anatomical position is a standardized stance used to describe locations and directions on the human body. In this position, the body stands upright, facing forward, with arms at the sides and palms facing forward.

• Hallux (big toe) is medial to the other toes, not lateral to metatarsal V (the little toe).

• Pollex (thumb) is lateral to the other fingers, including metacarpal V (the pinky).

Example: In anatomical position, the right thumb (pollex) is on the lateral side of the right hand.

Homeostasis and Control Centers

Central Nervous System Regulation

• Body Temperature Regulation: The hypothalamus is the main control center for body temperature, not the medulla oblongata.

• Breathing Regulation: The medulla oblongata is the main control center for breathing (respiratory rhythm).

Additional info: The hypothalamus integrates signals for thermoregulation, while the medulla oblongata controls vital autonomic functions such as heart rate and respiration.

The Axial Skeleton

Components of the Axial Skeleton

• The axial skeleton consists of the skull, vertebral column, and thoracic cage (ribs and sternum).

• The pelvis and clavicle are part of the appendicular skeleton, not the axial skeleton.

Example: The sternum is part of the thoracic cage, which is included in the axial skeleton.

Bone Composition and Connective Tissues

Bone Matrix and Hardness

• Hydroxyapatite is the mineral compound that provides bone with its hardness. Its chemical formula is:

$Ca_{10}(PO_4)_6(OH)_2$

• Collagen provides tensile strength and flexibility, but not hardness.

• Adipose tissue is not a component of bone matrix.

Ligaments, Tendons, and Periosteum

• Ligaments and tendons are made of dense regular connective tissue, which resists tension in one direction.

• Periosteum (the membrane covering bones) is made of dense irregular connective tissue, allowing resistance to forces in multiple directions.

Lower Limb Bones and Joints

Key Bones and Features

• The lateral malleolus is part of the fibula.

• There are 7 tarsal bones in the human foot and 8 carpal bones in the human hand.

Membrane Transport and Resting Membrane Potential

Potassium Distribution and Movement

• Potassium (K+) concentration is higher inside the cell than outside.

• If allowed, K+ will flow out of the cell down its concentration gradient.

• When K+ leaks out, the resting membrane potential becomes more negative (hyperpolarization).

• This movement is an example of simple diffusion (if through leak channels) or facilitated diffusion (if through specific protein channels).

Basic Chemistry: Solutions and Redox

Solutions and Redox Reactions

• When KCl dissolves in water, it dissociates into K+ and Cl- ions.

• Solvent: The substance present in the greatest amount (usually water in biological systems).

• Solute: The substance dissolved in the solvent (e.g., KCl).

• Redox Memory Device: "OIL RIG" – Oxidation Is Loss (of electrons), Reduction Is Gain (of electrons).

• The species that gains electrons is reduced.

Muscle Contraction and Biochemistry

Events in Skeletal Muscle Contraction

• Correct order of events:

  1. Motor neuron action potential

  2. Muscle fiber depolarization

  3. RyR (ryanodine receptor) channels open

  4. Myosin binds to actin

• ATP is responsible for detachment of the myosin head from actin during cross-bridge cycling.

ATP Production Pathways

Pathway	ATP Produced (per glucose or per creatine phosphate)	Location in Cell
Creatine phosphate pathway	1 ATP per creatine phosphate	Cytosol
Glycolysis	2 ATP per glucose	Cytosol
Glycolysis + Oxidative Phosphorylation + ETC	~30-32 ATP per glucose	Glycolysis: Cytosol; Oxidative phosphorylation & ETC: Mitochondria

Muscle Fiber Types

• Slow-twitch (Type I) fibers contain the most myoglobin, giving them a red color and high endurance.

Muscle Relaxants

• Dantrolene is an antagonist to the RyR (ryanodine receptor), inhibiting calcium release from the sarcoplasmic reticulum.

Nervous System: Tracts, Neurotransmitters, and Action Potentials

Spinal Cord Tracts

• Spinocerebellar tract does NOT cross the midline; it carries proprioceptive information to the cerebellum.

• The corticospinal tract crosses the midline at the medulla oblongata (pyramidal decussation).

• The spinothalamic tract carries pain and temperature sensations.

Neurotransmitters

• Glutamate is the primary excitatory neurotransmitter in the CNS; GABA and glycine are primary inhibitory neurotransmitters.

• When glycine and GABA ionotropic channels open, Cl- flows into the cell via facilitated diffusion, causing hyperpolarization.

Action Potentials

• Depolarization phase: Caused by influx of Na+.

• Repolarization phase: Caused by efflux of K+.

• Tetrodotoxin (TTX) blocks voltage-gated Na+ channels, inhibiting action potentials.

• Action potential propagation is NOT dependent on axon length, but is affected by axon diameter, myelination, and temperature.

• Myelin sheath is formed by Schwann cells in the PNS and oligodendrocytes in the CNS.

• Lidocaine numbs tissue by inhibiting voltage-gated Na+ channels.

Cell Signaling: GPCR Cascade

Order of Events in a GPCR Cascade

1. 1st messenger binds to receptor

2. GDP unbinds from G protein

3. G protein unbinds from receptor

4. GTP is hydrolyzed by the G protein

Musculoskeletal Levers

Lever Systems in the Body

• A lever consists of a fulcrum (pivot point), effort (applied force), and load (resistance).

• Order for common movements:

  • Elbow flexion: Fulcrum (elbow joint), Effort (biceps muscle), Load (hand/forearm)

  • Neck flexion: Fulcrum (atlanto-occipital joint), Effort (neck muscles), Load (head)

  • Plantarflexion: Fulcrum (ball of foot), Effort (calf muscles), Load (body weight)

Additional info: These are examples of first, second, and third class levers in the human body.