BIO 270 Exam 1

What is the mechanistic approach in physiology?

Explaining how the body responds the way it does, focusing on the mechanisms rather than just the purpose.

What is the structural organizational hierarchy of the body?

Chemical -> Organelles -> Cells -> Tissues -> Organs -> Organ Systems -> Organism.

Define homeostasis.

The maintenance of a relatively stable internal environment despite external changes; a dynamic "happy medium."

What is the function of the circulatory system in homeostasis?

It carries materials (nutrients, O2) from one part of the body to another.

How does the urinary system contribute to homeostasis?

It removes excess water, salt, acid, and electrolytes from plasma and eliminates them in urine.

What is the difference between negative and positive feedback?

Negative feedback opposes the initial change to restore stability; Positive feedback amplifies the initial change.

Give an example of positive feedback in the body.

Uterine contractions during childbirth (becoming increasingly stronger until birth).

What are the three main components of a feedback system?

Sensor (monitors variable), Control Center (integrator/compares to set point), Effector (makes response).

What are the three types of muscle tissue?

Skeletal (moves skeleton), Cardiac (pumps blood), and Smooth (controls hollow tubes).

What are the three primary functions of epithelial tissue?

Protection (boundaries), Secretion (glands), and Absorption (nutrients).

Describe the structure of the plasma membrane.

A fluid-mosaic model composed of a phospholipid bilayer with hydrophilic heads, hydrophobic tails, and proteins.

What is the function of the Rough Endoplasmic Reticulum (RER)?

Protein synthesis (manufacturing plant) due to the presence of ribosomes on its surface.

What is the function of the Smooth Endoplasmic Reticulum (SER)?

Lipid synthesis, steroid hormone production, and detoxification in the liver.

What is the function of the Golgi complex?

Modifies proteins secreted by the ER, sorts them, and directs them to their final destination via vesicles.

What is the purpose of lysosomes?

They contain hydrolytic (digestive) enzymes to digest worn-out organelles and pathogens (the "janitors" of the cell).

What is the process of Exocytosis?

Vesicles bind to the plasma membrane and release their contents to the exterior of the cell.

What is the difference between anabolic and catabolic reactions?

Anabolic reactions use energy to build macromolecules; Catabolic reactions break down molecules to release energy.

What are the products of Glycolysis?

2 Pyruvic acids, 2 ATP, and 2 NADH.

Where does the Krebs Cycle occur?

The mitochondrial matrix.

What is the function of the Electron Transport Chain (ETC)?

It uses high-energy electrons from NADH and FADH2 to create a proton gradient, driving ATP synthesis (oxidative phosphorylation).

Is Glycolysis aerobic or anaerobic?

Anaerobic (does not require oxygen).

What happens to Pyruvate if oxygen is unavailable?

It is converted into lactic acid, allowing the cell to regenerate NAD+ so glycolysis can continue.

Why is ATP production important?

It provides the energy for mechanical work, transport across membranes, and building cellular structures.

What is the role of the SNARE hypothesis?

It describes proteins (Synaptobrevin, Syntaxin, Synaptotagmin) that facilitate vesicle fusion with the plasma membrane.

What is the function of cholesterol in the plasma membrane?

It is tucked between phospholipids to contribute to the stability of the membrane.

What is the difference between integral and peripheral proteins?

Integral proteins span the membrane width; peripheral proteins lie loosely on the inner or outer surface.

What is the function of Cell Adhesion Molecules (CAMs)?

They act as "velcro" connections between adjacent cells to bind them into tissues.

What are the three types of cell junctions?

Desmosomes (spot rivets for stretching), Tight junctions (seal off leaks), and Gap junctions (tunnels for communication).

What are the properties of particles that can pass through the membrane via simple diffusion?

Small, uncharged (nonpolar), and lipid-soluble (e.g., O2, CO2).

What is the definition of Osmosis?

The diffusion of water through a selectively permeable membrane toward an area of higher solute concentration.

What is a hypertonic solution?

A solution with a higher concentration of nonpenetrating solutes than normal body cells, causing cells to shrink.

What is the definition of facilitated diffusion?

Passive transport (high to low concentration) using a carrier protein to move large molecules like glucose.

What is Primary Active Transport?

Movement of molecules against a gradient using direct ATP energy (e.g., Na+/K+ ATPase pump).

What is the resting membrane potential of most cells?

-70 mV.

What maintains the resting membrane potential?

The Na+/K+ ATPase pump and the unequal distribution of ions (K+ leakage channels).

Why is the Na+/K+ pump called "electrogenic"?

Because it pumps 3 Na+ out for every 2 K+ in, resulting in a net loss of positive charge inside the cell.

What happens to a cell in a hypotonic solution?

It gains water and swells (potentially bursting).

Define depolarization.

When the membrane becomes less polarized (moves closer to 0 mV) than the resting potential.

Define hyperpolarization.

When the membrane becomes more polarized (more negative) than the resting potential.

What is the threshold potential for a typical neuron?

Approximately -55 mV.

What are graded potentials?

Short-distance signals that occur in small regions of the membrane; their magnitude varies with the stimulus.

What occurs during the depolarization phase of an action potential?

Voltage-gated Na+ channels open, and Na+ rushes into the cell, reversing the potential to +30 mV.

What causes repolarization of the neuron?

Voltage-gated Na+ channels close, and voltage-gated K+ channels open, allowing K+ to flow out of the cell.

What is the role of the myelin sheath?

It insulates the axon and allows for saltatory conduction, increasing the speed of impulse propagation.

What is the synaptic cleft?

The physical space between the presynaptic neuron and the postsynaptic neuron.

What is an EPSP (Excitatory Postsynaptic Potential)?

A graded depolarization caused by neurotransmitter binding that opens cation channels (Na+ enters).

What is an IPSP (Inhibitory Postsynaptic Potential)?

A graded hyperpolarization caused by neurotransmitter binding that opens K+ or Cl- channels.

What is temporal summation?

When rapid, successive impulses from one neuron at the same synapse combine to reach threshold.

What is spatial summation?

When multiple different neuronal inputs arrive at the same time and converge on the axon hillock to reach threshold.

How do drugs modify synapses?

By altering the synthesis, release, reuptake, or degradation of neurotransmitters, or by blocking/activating receptors.

What is the difference between afferent and efferent pathways?

Afferent (sensory) carries impulses to the CNS; Efferent (motor) carries impulses from the CNS to effectors.

What are the functions of Astrocytes?

They hold neurons together, aid in the Blood-Brain Barrier (BBB), and repair brain injuries.

What is the function of the Blood-Brain Barrier (BBB)?

It minimizes the risk of harmful blood-borne substances reaching central nervous tissue by using tight junctions.

What is the function of the Thalamus?

It serves as a relay station and integrating center for sensory input on its way to the cerebral cortex.

What is the role of the Hypothalamus?

It is the "master gland" that regulates internal environment (temp, thirst, food intake, hormone secretion).

What is the function of the Cerebellum?

It coordinates motor activity, maintains balance, and plans/executes voluntary movement.

What is Broca’s area?

A region in the left frontal lobe that governs speaking ability.

What is Wernicke’s area?

A region at the junction of the left parietal, temporal, and occipital lobes concerned with language comprehension.

What are the components of a reflex arc?

Receptor, Afferent pathway, Integrating center, Efferent pathway, and Effector.

What is a monosynaptic reflex?

A simple reflex with only one synapse between the afferent and efferent neurons (e.g., stretch reflex).

What is transduction in sensory receptors?

The process of changing an environmental stimulus into an electrical signal (action potential).

What are the three common steps of every sensory system?

1. Transduction, 2. Afferent transmission, 3. Perception in the cerebral cortex.

What are nociceptors?

Pain receptors that respond to tissue damage or distortion (chemical, mechanical, or thermal).

What do Endogenous opioids (like endorphins) do?

They suppress pain transmission in the pain pathways in the spinal cord.

What is the function of the Iris?

It controls the amount of light entering the eye via smooth muscle (circular/radial).

What is the difference between Rods and Cones?

Rods are for night vision (high sensitivity, no color); Cones are for color vision and sharp acuity (low sensitivity).

What is accommodation in the eye?

The ability to adjust the curvature of the lens to focus on objects at different distances.

What is the difference between conductive and sensorineural hearing loss?

Conductive is an outer/middle ear problem (sound conduction); Sensorineural is a problem with the organ of Corti or auditory nerves.

What are the semicircular canals responsible for?

Dynamic equilibrium (detecting rotational acceleration).

What are the five basic taste qualities?

Salty, Sour, Sweet, Bitter, and Umami.

What are the two main branches of the autonomic nervous system (ANS)?

Sympathetic (fight or flight) and Parasympathetic (rest and digest).

What is the primary neurotransmitter of the Parasympathetic division?

Acetylcholine (ACh).

What are the primary neurotransmitters of the Sympathetic division?

Norepinephrine (NE) and Epinephrine.

Where are the cell bodies of the sympathetic preganglionic fibers located?

In the Thoracolumbar region (T1-L2) of the spinal cord.

What are the two types of Acetylcholine receptors?

Nicotinic and Muscarinic.

What is the function of Acetylcholinesterase?

It is an enzyme that breaks down acetylcholine in the synapse to stop muscle contraction.

What is the Neuromuscular Junction (NMJ)?

The synapse between a motor neuron and a skeletal muscle fiber.

What is the effect of Sympathetic stimulation on the pupil?

Dilation (to let more light in).

What is the effect of Parasympathetic stimulation on the GI tract?

Stimulation of motility and digestion.

What are the adrenergic receptors?

Receptors (Alpha and Beta) on target tissues that bind NE and Epinephrine to mediate the sympathetic response.

What is the functional unit of skeletal muscle?

The Sarcomere.

What defines the A-band in a sarcomere?

The full length of the thick filament (myosin).

What happens to the I-band during muscle contraction?

It shortens.

What is the role of Troponin?

It binds calcium to move Tropomyosin away from the actin binding sites.

What is the "power stroke" in muscle contraction?

The pivoting of the myosin head that pulls the actin filament toward the center of the sarcomere.

What is the T-tubule's function?

To conduct action potentials deep into the muscle fiber to trigger calcium release from the Sarcoplasmic Reticulum.

What is motor unit recruitment?

Increasing the number of active motor units to increase the total force of contraction.

What is the difference between twitch summation and tetanus?

Twitch summation is the additive effect of twitches; tetanus is a smooth, sustained contraction due to rapid stimulation.

What are the primary differences between Type I and Type II fibers?

Type I (slow-twitch) are fatigue-resistant and oxidative; Type II (fast-twitch) are high-power but fatigue quickly.

What is the role of Creatine Phosphate?

It provides a rapid, first-line energy reserve for regenerating ATP during short-term high-intensity exercise.

What are intercalated discs in cardiac muscle?

Structural connections containing desmosomes (mechanical) and gap junctions (electrical) that allow the heart to act as a syncytium.

What causes the plateau phase in cardiac muscle action potentials?

The slow influx of Ca2+ through L-type channels, which prevents tetanus.

How does cardiac muscle differ from skeletal muscle regarding calcium?

Cardiac muscle requires an influx of extracellular Ca2+ to trigger the release of intracellular Ca2+ from the SR.

What is the "pacemaker potential" in the SA node?

The slow, spontaneous depolarization toward threshold, primarily due to the "funny" Na+ current (If).

How does smooth muscle contraction differ from skeletal?

It uses Calmodulin (not Troponin) and relies more on latch-bridging to maintain tension with low energy use.

What is single-unit smooth muscle?

Muscle cells connected by gap junctions that contract as a single coordinated unit (e.g., GI tract).

What is multi-unit smooth muscle?

Cells that act independently and are innervated by the autonomic nervous system (e.g., iris of the eye).

What triggers smooth muscle contraction?

Increased cytosolic Ca2+, which activates Myosin Light Chain Kinase (MLCK).

What is the primary function of plasma?

To transport water, electrolytes, nutrients, waste, gases, and hormones throughout the body.

What is hematocrit?

The percentage of blood volume that is occupied by red blood cells.