Human A&P 120

Mar. 2, 2008 REVIEW OUTLINE for EXAM II

MATERIAL TO REVIEW from EXAM I:

From LAB--BIOETHICAL PRINCIPLES: be able to apply

A. AUTONOMY-- individual choice/freedom;autonomy of action should not be subjected to controlling constraint by others
B. NON-MALEFICENCE: Above all, do no harm; the first medical principle
C. BENEFICENCE--relationship to others not just self; oft cited as the 2nd medical principle -- 1. Basic version: help others only if they want help
-- 2. Strong version=PATERNALISM: higher authority enforces its idea of good
D. JUSTICE--equal or fair treatment, equal rights, equal goods:
-- 1. Egalitarian--equal goods
-- 2. Libertarian--equal rights/freedoms

PRINCIPLES of SELF-REGULATION

A. HOMEOSTASIS = REGULATED CONSTANCY

WHY needed? There are optimal states for many things such as water content, temperature, etc.

1. HOW to keep at optimum? Basic Negative Feedback System!

--VARIATIONS:

a) Dual effector control: 2 effectors that have opposite corrective effects (e.g., furnace, airconditioner), or 1 effector that can be boosted or inhibited--e.g., control by parasympathetic va sympathetic nerves);

b) effectors may be behaviors, e.g., seeking warm spots;

B. REGULATED CHANGE--not everything has a constant optimum

WHY? Many types of change are useful: growth, puberty, fight-or-flight, cycles, new situations…

HOW? 2 different mechanisms:

1. RESET System: changes the set point of a negative feedback system.

--a) temporary emergencies: e.g., fever; stress

--b) cyclical "clocks": e.g., sleep/wake cycle and hypothalamus SCN clock

2. POSITIVE FEEDBACK System--one which accentuates a change rather than reducing it. Sometimes this is not adaptive but a dangerous malfunction. BUT sometimes it can be useful for desired rapid changes: e.g., nerve APs!!!

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C. ENHANCED REGULATION

1. DELAY PROBLEM: Over and/or Undercompensations!

Delay problems are INHERENT in a simple feedback system because there are always delays in getting a signal from the disturbed state to the effector's response; if delays are too long and/or disturbance too fast, the system may oscillate (over and under-compensation)

-- What to do about delays?

ANTICIPATION system --one which activates a feedback system before the disturbance changes a regulated state; may use a sensor to measure the oncoming disturbance rather than the state itself. May be innate physiology or learned behaviors. Examples: role of Motor Cortex; Cerebellum; Memory in general

2. NEW-SITUATION PROBLEM: existing feedback system may not work well at high altitude, with new diet or activity regime, etc. Solution =

ACCLIMATIZATION or "ADAPTATION" system: change effectiveness/capacity/ability of feedback component. E.g., buy a bigger air conditioner if the climate is getting too hot for your old one

II. Principles of EVOLUTION

A. 2 LEVELS of EXPLANATION in Biology: see lecture & reading examples

1. "Proximate" or mechanistic: "as is"; "how does it work" analysis. Example: how sensors "adapt"

2. Evolutionary=historical/selective reason; "why did it end up this way" E.g, WHY sensors "adapt"

B. Basic steps in Evolution by Natural Selection -- review if needed

HIERARCHY OF BIOLOGY

–How GENES are regulated by PROMOTERS & transcription proteins--apply to MEMORY, hormones!

--LOCK and KEY concept for PROTEINS and molecules that they bind!

--Basic tissue types and how they make organs

NEW STUFF

SELF-REGULATION: Whole-Body Regulatory Systems

OVERVIEW: 1. Old vs. new ideas: 3-part interaction of Neural, Endocrine, Immunal

2. HIERARCHICAL/distributed REGULATION!! Intrinsic vs Extrinsic multiple levels: Why this is important! Robotics, governments, human body--analogy of Individual->City govt->Count Govt-->State govt->Federal govt

I. NERVES, NERVOUS SYSTEM

A. OVERVIEW: Cells

1. NEURONS: know basic structure/parts (dendrites, cell body, axons, axon ending with synapse)

2. GLIAL (specialized connective): nourish, assist neurons; insulation--myelin speeds up signals;

--ORGANIZATION: CNS (brain, spine) and PNS in (sensory) and out (motor)=somatic, parasympathetic, sympathetic

--Study Methods: can study individual cells, and brain regions with scanners, stimulators

B. SIGNALS / COMMUNICATION: ELECTRICAL

NEURON MEMBRANES: have leak channels; gated channels; Na-K ATPase pump

1. RESTING POTENTIAL, -70mV: a) Na/K ATPase pump -- moves 3Na⁺ out and 2K⁺ in per cycle: so EXTRACELLULAR fluid is dominated by Na⁺, INTRACELLULAR fluid by K⁺

b) Cell PROTEINS / DNA are negatively charged and trapped INSIDE the cell

c) Na⁺ has both ELECTRICAL and DIFFUSION gradient inwards, but gates are closed

d) K⁺ freely moves out through LEAK channels, but held mostly inside by negative charges

2. ACTION POTENTIAL (AP):--uses "VOLTAGE-GATED" channel proteins:

a) DEPOLARIZATION: some sort of stimulus causes Na⁺ to enter the neuron (via elect. Attraction and diffusion); cell voltage rises above -70 mV

IF cell voltage does not reach its threshold, some K+ leaves and cell goes back to resting; but if it does reach threshold (about -50mV), then b)--->

b) AP RISE: Positive feedback propogation occurs: at -55mV, Na+ channels snap OPEN. More Na+ to conduct/diffuse in. This cause nearby channels to reach -55 mV and to open. And so on. Thus an all-or-none voltage spike (AP) (about +30mV) propagates down the cell

c) REPOLARIZATION: at +30 mV, Na+ channels CLOSE and K+ channels OPEN. K+, which is higher in the cell, then moves out by conductance at first (repelled by positive charge of cell) and diffusion later:

d) Recovery When cell returns to resting potential

(-70mV), all channels close, and the Na/K pump restores the original Na/K gradients

3. GRADED POTENTIALS occur in neurons where there are no voltage-gated channels; other channels let ions flow in but these then decay over distance.

C. SIGNALS / COMMUNICATION: SYNAPTIC TRANSMISSION: axon ending

1) Stimulus: AP arrives ; 2) Ca++ channels open, and Ca++ ions flow (conduct) in; 3) Ca++ triggers exocytosis of neurotransmitter (NT) vesicles produced by neuron; 4) Diffusion across synaptic cleft; 5) Receptor binding ; 6) Receptor action, e.g.,let Na into target cell: see details below*

7) Shut-off: NT removed by reuptake transporter, or enzymatic breakdown

*Steps 5-6: RECEPTOR DETAILS: "lock and key" analogy:

a) Fast Excitatory: simulate the target by opening chemical-gated Na+ channels;

b) Fast Inhibitory: inhibit the target by opening chemical-gated K+ or Cl- channels;

c) Slow Modulating--"reprogram" the target (altering activity of its proteins and/or genes)--

via receptor-enzyme-2^nd messengers