PHGY 210 Lecture : Endocrinology- Lecture 1

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28 Sep 2011

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Midterm exam: monday march 8th, 6:30pm-8:00pm (30 mc, 30%) Endocrinology is self attenuating (eg: negative feedback loops). The essence of endocrinology: it"s all about communication. In a living organism there must be coordination of number of physiological activities taking place simultaneously such as: movement, respiration, circulation, digestion, excretion and metabolism. Endocrine system and nervous system both signal anatomical parts of the body. The central nervous system and the endocrine system represent the two major means by which these functions are coordinated. Communication between cells that are not in contact is achieved through a number of chemical substances (hormones), which are secreted by releasing cells and interact with specific receptors on distant target cells (bind to them). Signaling through these receptors leads to a specific physiological effect. Cells of the immune system release factors that act in a hormonal way (eg: cytokines). Therefore what we learn about endocrinology can apply to other parts of the body as well!

Related Questions

A mass m on an inclined plane that makes an angle of Î¸ with thehorizontal is attached via a string over a pulley to a mass M thathangs vertically from the edge of the inclined plane. When themasses are released, mass M accelerates vertically downward andmass m accelerates up the ramp. The coefficient of kinetic frictionbetween the mass m and the surface of the inclined plane isu_k.

a.) Draw a diagram of the situation and label all forces andaccelerations. Be
sure to indicate their directions with an arrow.

b.) Draw free body diagrams for each of the two masses. Be sure todraw a coordinate system and indicate the positive and negativedirections. Be sure to resolve any forces that are not acting alongeither the x or y directions of your coordinate system into their xand y components using right triangle trig.

c.) Use your free body diagrams and Netwonâs 2nd law to writeequations for this scenario. Do not use any numbers in theseequations.

d.) Given that m = 20-kg , M = 90-kg , = 30 , and = 0.14 . Find thenormal force acting on mass m.

e.) Find the force of friction acting on mass m.

f.) Find the acceleration of the masses. (You will have to use twoequations.)

g.) Find the tension on the string.

Good Vibes: Introduction to Oscillations

The conditions that lead to simple harmonic motion are as follows:

There must be a position of stable equilibrium.

There must be a restoring force acting on the oscillating object. The direction of this force must always point toward the equilibrium, and its magnitude must be directly proportional to the magnitude of the object's displacement from its equilibrium position. Mathematically, the restoring force F⃗ is given by ⃗, where is the displacement from equilibrium and k is a constant that depends on the properties of the oscillating system.

The resistive forces in the system must be reasonably small.

Consider a block of mass m attached to a spring with force constant k, as shown in the figure(Figure 1) . The spring can be either stretched or compressed. The block slides on a frictionless horizontal surface, as shown. When the spring is relaxed, the block is located at x=0. If the block is pulled to the right a distance A and then released, A will be the amplitude of the resulting oscillations.

Assume that the mechanical energy of the block-spring system remains unchanged in the subsequent motion of the block.

Part A

After the block is released from x=A, it will

(a) remain at rest

(b) move to the left until it reaches equilibrium and stop there.

(d) move to the left until it reaches x=−A and then begin to move to the right.

The time it takes the block to complete one cycle is called the period. Usually, the period is denoted T and is measured in seconds.

The frequency, denoted f, is the number of cycles that are completed per unit of time: f=1/T. In SI units, f is measured in inverse seconds, or hertz (Hz).

Part B

If the period is doubled, the frequency is

(a) unchanged

(b) doubled

Part C

An oscillating object takes 0.10 s to complete one cycle; that is, its period is 0.10 s. What is its frequency f?

Express your answer in hertz.

Part D

If the frequency is 40 Hz, what is the period T?

Express your answer in seconds.

The following questions refer to the figure (Figure 2) that graphically depicts the oscillations of the block on the spring.

Note that the vertical axis represents the x-coordinate of the oscillating object, and the horizontal axis represents time.

Part E

Which points on the x-axis are located at a distance A from the equilibrium position?

(a) R only

(b) Q only

Part F

Suppose that the period is T. Which of the following points on the t-axis are separated by the time interval T?

(a) K and L

(b) K and M

(d) L and N

(e) M and P

Now assume for the remaining Parts G - J, that the x coordinate of point R is 0.12 m and the t coordinate of point K is 0.0050 s.

Part G

What is the period T?

Express your answer in seconds.

Part H

How much time t does the block take to travel from the point of maximum displacement to the opposite point of maximum displacement?

Express your answer in seconds.

Part I

What distance d does the object cover during one period of oscillation?

Express your answer in meters.

Part J

What distance d does the object cover between the moments labeled K and N on the graph?

Express your answer in meters.

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PHGY 210 Lecture : Endocrinology- Lecture 1

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