PSIO 201 Lecture Final

Define homeostasis.

Homeostasis is the condition in which the body’s internal environment remains relatively constant within physiological limits, despite changes in the external environment.

What are the elements of a feedback loop?

Receptor (sensor), Control center (integrator), Effector.

What is negative feedback? Give an example.

Negative feedback reverses the original stimulus to maintain homeostasis; e.g., body temperature regulation, blood glucose control.

What is positive feedback? Give an example.

Positive feedback amplifies the original stimulus until a specific endpoint; e.g., childbirth contractions.

List the five classes of organic compounds.

Lipids, carbohydrates, proteins, nucleotides, nucleic acids.

Describe the composition and function of lipids.

Composed of C and H; nonpolar, hydrophobic; includes fats, oils, phospholipids, steroids.

Describe the composition and function of carbohydrates.

Composed of C, H, O; used for energy and structural support.

Describe the composition and function of proteins.

Composed of C, H, O, N; built from amino acids; function as enzymes, transporters, receptors, structural components.

Describe the composition and function of nucleotides.

Composed of C, H, O, N, P; building blocks of nucleic acids, energy carriers.

Describe nucleic acids.

Polymers of nucleotides (DNA, RNA); store and transmit genetic information.

Compare passive diffusion and active transport.

Passive diffusion: down concentration gradient, no energy; Active transport: against gradient, requires energy (ATP or ion gradient).

What distinguishes facilitated diffusion from simple diffusion?

Facilitated diffusion uses specific protein channels or carriers; still down gradient and passive; limited by number of carriers (saturation).

What is carrier-mediated transport?

Transport via specific proteins; can be passive (facilitated) or active; shows saturation at high substrate concentrations.

Describe normal Na⁺ and K⁺ gradients across cell membranes.

Na⁺: high outside, low inside; K⁺: high inside, low outside.

How does the Na⁺/K⁺ ATPase maintain these gradients?

Pumps 3 Na⁺ out and 2 K⁺ in using ATP; maintains gradients and contributes to negative membrane potential.

Define resting membrane potential (RMP).

Baseline electrical potential of a cell at rest, typically –70 mV in neurons, mainly determined by K⁺ permeability.

Name the four main bone cell types and their function.

Osteogenic (stem, divide → osteoblasts), Osteoblasts (build bone), Osteocytes (maintain matrix), Osteoclasts (resorb bone).

What are the extracellular components of bone?

Organic matrix (osteoid, collagen) for flexibility; Inorganic matrix (hydroxyapatite) for hardness.

Differences between compact and spongy bone.

Compact: outer layer, osteons, strength/protection. Spongy: inner layer, trabeculae, lighter, houses marrow.

Major steps in bone remodeling.

Resorption by osteoclasts → formation by osteoblasts → maintenance by osteocytes.

Role of PTH in calcium regulation.

Increases osteoclast activity, kidney reabsorption, calcitriol production → raises blood Ca²⁺.

Role of calcitonin in calcium regulation.

Inhibits osteoclasts, promotes bone deposition → lowers blood Ca²⁺.

Role of calcitriol in calcium regulation.

Increases intestinal Ca²⁺ absorption, works with PTH → raises blood Ca²⁺.

List the steps of the crossbridge cycle.

Formation → power stroke → detachment → reactivation → repeat/relaxation.

Describe events at the neuromuscular junction.

AP → Ca²⁺ influx → ACh release → binds nicotinic receptors → Na⁺ entry → EPSP → AP in muscle → ACh breakdown.

Strategies to increase muscle force.

Motor unit recruitment, frequency of activation, optimal muscle length (length-tension).

ATP sources for muscle contraction and durations.

Stored ATP (1–2 s), creatine phosphate (~10 s), anaerobic glycolysis (1–2 min), aerobic metabolism (minutes–hours).

Role of neurons.

Receive, process, transmit electrical and chemical signals; generate action potentials.

Role of neuroglia.

Support neurons structurally, metabolically, ion balance, myelination, synaptic function.

Difference between nucleus/ganglion and tract/nerve.

Nucleus = CNS cell bodies; Ganglion = PNS cell bodies. Tract = CNS axons; Nerve = PNS axons.

Path of sensory info in spinal cord.

Enters dorsal root → dorsal horn → synapse/interneurons → higher centers.

Path of motor info in spinal cord.

Exits ventral root → somatic efferents to skeletal muscle; visceral motor neurons via lateral horn → autonomic ganglia.

Sympathetic vs parasympathetic differences.

Sympathetic: thoracolumbar, short pre, long post, ACh (pre), NE (post), fight/flight. Parasympathetic: craniosacral, long pre, short post, ACh (both), rest/digest.

Five components of a reflex arc.

Sensory receptor → sensory neuron → integration center → motor neuron → effector.

Predict effect on membrane potential if Na⁺ permeability increases.

Na⁺ enters → depolarization → more positive membrane potential.

Predict effect if K⁺ permeability increases.

K⁺ leaves → hyperpolarization → more negative membrane potential.

What is depolarization?

Membrane potential becomes less negative (inside more positive).

What is repolarization?

Return to resting membrane potential after depolarization.

What is hyperpolarization?

Membrane potential becomes more negative than resting potential.

Difference between graded potentials and action potentials.

Graded: local, variable size, decay with distance. Action: all-or-none, uniform, propagate without decay.

EPSP vs IPSP.

EPSP: depolarizing, moves toward threshold. IPSP: hyperpolarizing, moves away from threshold.

Absolute vs relative refractory periods.

Absolute: no AP possible. Relative: AP possible if stimulus stronger than normal.

Saltatory vs continuous conduction.

Continuous: unmyelinated, slow. Saltatory: myelinated, jumps nodes, faster.

Role of oligodendrocytes and Schwann cells.

Oligodendrocytes: CNS myelination, multiple axons. Schwann cells: PNS myelination, single axon.

Synapse structure and astrocyte function.

Presynaptic terminal, synaptic cleft, postsynaptic membrane; astrocytes regulate neurotransmitter, ions, and support synapse.

Ionotropic vs metabotropic receptors.

Ionotropic: ligand-gated ion channels, rapid response. Metabotropic: G-protein coupled, slower, longer-lasting.

General vs special senses.

General: touch, pressure, vibration, pain, temp, proprioception. Special: vision, hearing, balance, taste, smell.

Receptive field and receptor potential.

Receptive field: area where stimulus affects neuron. Receptor potential: graded potential in sensory receptor after stimulation.

How is sensory resolution affected by receptive field size?

Smaller receptive fields → higher resolution; larger → lower resolution.

Sensory transduction definition.

Conversion of a physical stimulus into an electrical signal in a sensory receptor.

Olfactory epithelium cell types.

Olfactory receptor neurons, supporting cells, basal stem cells, mucus-secreting glands.

Olfactory transduction steps.

Odorant binds receptor → G-protein → cation channels open → depolarization → action potentials → olfactory bulb.

Eye parts that refract light.

Cornea (major), lens (fine focus), aqueous & vitreous humor (minor).

Visual pathway from retina to cortex.

Photoreceptors → bipolar cells → ganglion → optic nerve → optic chiasm → LGN → optic radiations → V1.

Mechanism of accommodation.

Ciliary muscle contracts → lens rounds → near vision. Ciliary muscle relaxes → lens flattens → far vision.

Presbyopia cause.

Loss of lens elasticity and reduced ciliary muscle efficiency → impaired near focus.

Rod vs cone differences.

Rods: high sensitivity, low-light, no color, peripheral. Cones: low sensitivity, bright light, color, fovea.

Rod photoreceptor structure & rhodopsin function.

Outer segment: rhodopsin discs. Inner: metabolism. Synapse: bipolar cells. Rhodopsin absorbs photons → phototransduction.

Phototransduction effect on Na⁺ channels.

Light → rhodopsin → cGMP decreases → Na⁺ channels close → hyperpolarization → decreased glutamate → signal to bipolar cells.

Auditory structures for sound detection.

Pinna, external canal, tympanic membrane, ossicles, cochlea, organ of Corti, tectorial membrane.

Hair cell transduction mechanism.

Stereocilia bend → mechanically gated K⁺ channels open → depolarization → Ca²⁺ influx → neurotransmitter release → AP in auditory nerve.

Loudness vs pitch coding.

Loudness: firing rate & neuron recruitment. Pitch: location on basilar membrane (base = high, apex = low).

Rotational vs linear acceleration detection in vestibular system.

Rotational: semicircular canals, cupula, endolymph. Linear/gravity: utricle & saccule, otoliths. Both: hair cells, mechanically gated channels.