Chapter 1- Homeostasis

physiology

the study of how living organisms function

-It spans the range from individual molecules and cells to integrated organ systems and whole-organism behavior.

- central theme: function + integration as physiologists are most interested in

How complex is physiology?

Physio is one protein: an ion channel in a cell

It is neuron or muscle tissue in response to a stimulus

Its kidney regulating Na and Bp

Its progressive of CAD and eventual MI

Greek word for physiology

nature or origin

pathophysiology

The study of altered physiological processes associated with disease or injury. Study of disease states and physiological dysfunction

“Gone wrong”

- bodies inability to maintain homeostasis

- disease=disruption of normal physiological processes

Anatomy

the study of the structures of body parts

Core Theme

Structure and function are tightly integrated; physical structures determine, enable, and constrain physiological processes.

Cell

simplest structural units into which a complex multicellular organism can be divided and still retain the functional characteristics of life

cell differentiation

Unspecialized stem cells differentiate into specialized functional cell types during development. processes by which unspecialized cells become specialized

How many cells can be identified in the body?

200 kinds that have different structures and functions

Functional units

Sub-units within an organ that perform the essential functional work of that organ (e.g., nephrons in the kidney, alveoli in the lungs, lobules in the liver).

Structural Hierarchy & Body Organization

Cells- tissues- organs-organ systems- organism

Dynamic Constancy:

Physiological variables fluctuate over time around a predictable set point, but are maintained within a narrow, non-lethal range.

Levels change over short periods of time, but remain relatively constant over long periods of time

Steady State vs. Equilibrium:

• Dynamic Steady State: A system where a variable is kept constant over time, but energy expenditure (ATP) is required to maintain it (e.g. Na +/ K+ ATPase pump)

• Equilibrium: A variable remains constant without any input of energy.

hierarchy

cell, tissue, organ, organ system, organism

tissue

an aggregate of a single type of specialized cell

general cellular fabric of any organ/structure

list the 4 tissue types

muscle, nervous, epithelial, connective

list the 3 types of muscle cells

cardiac, skeletal, smooth

involuntary

cardiac (involuntary, striated, found only in the heart)- when cardiac muscle muscles generate force, the heart contracts and consequently pumps blood into circulation and smooth (involuntary, non-striated, lines blood vessels and visceral organs) ex. Gi tract and blood vessels. contraction of these muscles decreases the diameter or the length of the tubes

voluntary

skeletal (voluntary, striated, attached to bone)- produce movements of the limbs or trunk. May attach to the skin for facial expressions

voluntary movement

you can choose to contract and relax muscle consciously

muscle tissue function

produces force and movement

neuron

Specialized to initiate, integrate, and conduct electrical signals to other cells. Means to controlling other cells

main cell types:

Neurons (signal transmission) and Glial Cells (support, protection, and nourishment). Nephron (functional unit of a neuron)

nervous tissue

collection of neurons makes nervous tissue

major communication system of the body. ex. such as that of the spinal cord or brain

nerve

axons from many neurons packaged together along with connective tissue

epithelial cells

specialized for selective secretion and absorption of ions, and molecules, and for protection

- characterized by name: cuboidal (cube-shaped), columnar (elongated), squamous (flattened), and ciliated

Epithelial tissue

known as epithelium may form form any type of epithelia cell

ex. simple= single cell. numerous cells= stratified.

Where is epithelial tissue (epithelia) located

Surfaces that cover the body or individual organs, they line the inner surfaces of the tubular and hollow structures within the body such as the trachea, forms glands

function

shape dictates this

tubular lumen

inside vessel of a tract. faces the interior

basement membrane

extracellular protein layer anchoring epithelium

apical membrane

• Faces the interior (called the lumen), cavity, or exterior environment.

ex. trachea, the tubules of kidneys

basolateral surface

anchored to basement membrane and faces the interstitial fluid

Main idea of epithelia

The two sides of all of these cells may perform different physiological functions

Such that the basolateral membrane may be specialized to a certain molecule going through on this side compared to what apical membrane may allow

Example of glucose here

the kidney tubule, the apical membranes transport useful solutes such as the sugar glucose from the tubule lumen into the epithelial cells; the basolateral sides of the cells transport glucose out of the cell and into the surround fluid where it can reach the bloodstream. tight junction prevent glucose from leaving “backwards”

tight junctions

hold cells together, form selective barriers between compartments, helps regulate the exchange of molecules

The apical and basolateral membranes are held together along their lateral surfaces by this

connective tissue

connects, anchor, and support structures of the body

types of connective tissue

loose connective (loose meshwork of cells and fibers underlying most epithelial layers), dense connective (the tough, rigid tissue that makes up tendons and ligaments) blood, cartilage, bone

Bloods connection to connective tissue

it has the same embryonic origin as other connective tissue bc it connects the various organs and tissues the body through delivery of nutrients, removal of wastes, and transport of chemical signals

extracellular matrix

Made by connective tissue

Its forms the ECM

Mostly proteins and polysaccharides. surrounds each individual cell in the body; consists of ropelike collagen fibers and rubber band like elastin fibers; mixture of non fibrous proteins that contain carbohydrate

ECM functions

1) scaffold for cellular attachments

2) transmits information in the form of chemical messengers to cells to regulate activity, migration, growth, and differentiation

organ

Composed of two or more of the four kinds of tissues arranged in various proportions and patterns such a sheets, tubes, layer, bundles, and strips

organ systems

contain multiple organs that work together

- major systems: circulatory, digestive, endocrine, immune, integumentary, lymphatic, musculoskeletal, nervous, reproductive, respiratory, urinary

body fluid

watery solution of dissolved substances such as oxygen, nutrients, and soluble wastes. It is within and around all cells of the body, and within blood vessles, and it known as internal environment

three body fluid compartmentss

1) intracellular fluid

2) plasma

3) interstitual fluid

Intracellular fluid

the fluid contained within all the cells of the body and accounts for about 67% of all the water in the body

extracellular fluid

fluid in blood and surrounding all cells.

plasma

Fluid portion of the blood in which blood cells are suspended in. 25% of extracellular fluid in body is this. 7% of total body water

interstitial fluid

the 75% of extracellular fluid that lies around and between cells (space is called interstitium). Accounts for 26% of total-body water

What two parts are in the extracellular fluid

plasma and interstitial fluid. (extracellular fluid accounts for 1/3 of water in the body)

Internal environemnt

total-body fluid, made of 2/3 intracellular and 1/3 extracellular

critical

maintaining differences in fluid composition across the cell membrane is ____________ to cell activity and survival

Compare the extracellular fluid from the intracellular

it is very different from one another. Such that plasma exchanges oxygen, nutrients, wastes within the interstitial fluid while extracellular is very different. Maintaining differences in composition is important way in which cells regulate their own activity

Plasma Membrane: Separates

ICF and ECF; selectively permeable to maintain distinct ion concentrations.

Capillary Wall:

Separates Plasma and Interstitial Fluid; allows free exchange of water and small solutes, but retains plasma proteins.

fluid

moves between compartments and molecules also move but with more control

Compartmentalization

the property of barriers determine which substance can move between compartments, then in turn account for differences in composition of the different compartments.

What are the interstitial fluid and the plasma seperated by?

by walls of their blood vessels

Fluid compartment percentage and location

Fluid Compartment	Location / Definition	Proportion of TBW
Intracellular Fluid (ICF)	Fluid contained inside all cells.	~67% (2/3)
Extracellular Fluid (ECF)	Fluid outside cells (includes ISF + Plasma).	~33% (1/3)
Interstitial Fluid (ISF) that and plasma has very similar comp.	Extracellular fluid surrounding non-blood cells.	~80% of ECF
Plasma greater proteins than ISF	Liquid portion of the blood within blood vessels.	~20% of ECF

Differences in compositions of the compartments reflect what?

Reflects the activities of the barriers separating them

How many liters of fluids are in an average human?

whole body 70L

42L water

5L blood

3L plasma averavge in/out per day

Assuming a person’s water constitutes 60% of a persons body weight. what percentage is due to extracellular body water?

.33 times .60 = .20

homeostasis

The state of dynamic constancy, not static of the internal environment (ECF).

• most physiological variables are maintained within a predictable range

- maintenance of stable, internal environment

- ex: blood pressure, body temperature, blood glucose levels

Claude Bernard was the first idea, while Walter Cannon coined the term

Homeostasis is what type of process?

a dynamic, not static process

Explain blood glucose concentration

The blood glucose concentration increases within a short time after eating. Large changes are not consistent with the idea of stability or static internal environment. Once the concentration of glucose increases, compensatory mechanisms restore it towards the concentration it was before the meal.

The homeostatic compensatory mechanisms do not significantly overshoot to a degree in the opposite direction

dynamic constancy

- variables are not perfectly constant

- fluctuate within normal ranges

- stability exists over time despite short term changes

- levels change over short periods of time, but remain relatively constant over long periods

- ex: blood glucose rises affect meals then go back down between meals

Explain homeostatic

describes the body's active process of maintaining a stable, balanced internal environment despite constant changes in the outside world.The compensating mechanisms that mediate such responses

one may be homeostasis for one variable but not homeostatic for another. Ex. as long as the Na+ in the blood are a normal range, Na+ homeostasis exists. But if a person’s Na+ concentration is homeostasis the person may suffer from disturbances such as low pH from kidney disease and can be fatal

When one variable becomes slightly out of balance, other variable sin the body become nonhomeostatic at a consequence ex. sweating and maintaining body temperature. When homeostasis is disturbed for one variable, other variables will compensate

disease

loss of homeostasis

set point

target value around which variable is regulated

ex. the steady state temperature

steady state

condition on which a variable ex. temperature, is not changing but in which energy such as heat, it must be continuously added to maintain a stable, homeostasis condition

equilibrium

A particular variable is not changing but requires no energy input.

Explain

arrows mean “lead to” or “causes”. Arrows in box mean increasing or decrease

homeostatic control systems maintain body temps when room temperature decreases. Shows homeostatic systems.

Decreased room temperature tends to cause an increase in heat loss form the body, curling up causes a decrease in heat loss from the body.

-The variable (body temp) remains constant bc of the heat production (input) equals the loss of the body (output)

negative feedback

most common; system shuts the system off once the set point has been reached. Increases or decreases in the variable being regulated brings about responses that tend to move the variabel in the direction opporist (negative to) the direction of the original change

- stabilizes system, minimalized deviations, essential for homeostasis and stability

- ex: body temperature regulation, blood glucose regulation, feedback inhibition of biochemical pathways, thermoregulatory system, production of adenosine triphosphate within cells

The active product

controls the sequence of chemical reactions by inhibiting the sequences rate-limiting enzyme

Example of ATP in negative feedback

As ATP accumulates in the cell, it inhibits activity of the enzymes involved in the breakdown of glucose. As ATP increases within the cell, further production of ATP slows down due to negative feedback. If ATP decreased within a cell, negative feedback is release and more glucose is broken down so more ATP can be produced

positive feedback

Less common!

• The response amplifies or accelerates the original variable

• Purpose: Drives a process to a rapid conclusion/completion; does not maintain homeostasis.

- characteristics: amplifies change, drives process to completion, away from set point

- ex: blood clotting, birth, inflammation

Blood clotting example

when a vessel is ruptured, damaged cells in the vessel release chemicals into the blood that attract plateelets to the injury sits and activate them. The the cells stick together to form clots and seal the wound

feedforward regulation

Changes in regulated variables are anticipated and prepared for they actually occur

-fine tunes homeostatic responses

- reduces fluctuation and improves efficiency, Minimizes the deviation from the set point before the change actually occurs.

- ex: responses to cold before body temperature falls, digestive responses triggered by sight/smell of food, increased heart rate before exercise

What does feedforward regultion utilize?

A set of external or internal environmental detectors. It’s a result of the phenomenon: learning. Overtime our nervous systems learn to anticipate them and resist them for effectively.

Common set point

fever that increases the body temperature due to infection.

or

set point of body temp is higher during the day, when we are active, than at night

Classing demands

explains the phenomenon between body temp and water balance during exercise. Our set points are adaptive in some cases. Not everything can be held at a constant homeostasis control system

Homeostasis is a what state?

A steady state in which a variable is unchanging but only as long as energy is provided (equilibrium does not require input of energy)

Homeostatic control systems

minimize chnages but cannot maintain complete constancy of regulated variable

reflexes

A reflex is a specific involuntary, unpremeditated, unlearned “built in response” to a stimulus

• ex. pulling your hand away from a hot stove of shutting your eyes as an object approaches your face, kneww-jerk reflex, surprised at a loud noise

Reflexes

are learned or acquired

can be altered by learning

Reflex arc

pathway mediating a reflex

reflex pathway

stimulus, reception, afferent pathway, integrating center, efferent pathway, effector, response

Stimulus

a detectable change in the internal or external environment ex. change in temp, plasma conc

receptor

detects change in environment

afferent pathway

carries info to integrating center; central nervous system

integrating center

acts upon a receptor to produce a signal that is relayed to the center.

efferent pathway

carries commands away from integrating center; send info of what change needs to be out to body

effector

Actions produces response.

- ex: muscles, glands are the majority.

- typically a hormone secreted into the blood

If a response produced by the effector causes a decrease in the magnitude of the stimulus that triggered the sequence of events

Then the reflex leads to negative feedback and there is a typical homeostatic control system

hormones

a type of chemical messenger secreted form glands or cells in the blood. They act on many different cells simultaneously because they circulate throughout the body.

Example of a hormone as a reflex

when glucose concentration in the blood is increased, this is detected by gland cells in the pancreas (receptor). The same cells then release the hormone insulin (effector) into the blood, which lowers the blood glucose conc.

local homeostatic responses

responses are initiated by a change in the external or internal environment and they induce an alteration of cell activity with a net effect of countering the stimulus

involves stimulus-response sequences

occurs only in the area of the stimulus (no nerves or hormones are involved) like reflexes do

Non-nerve reflexes

are essentially feedback loops by another name

Almost all body cells can act as effectors in homeostatic reflexes, yet—muscle and gland—are the major effectors of biological

control systems.

• In the case of glands, the effector is typically a hormone secreted into the blood.

Two primary signals for feedback control

Hormones: released from glands or cells into blood

Neurotransmitters are chemical messengers released from endings of neurons onto other neurons, muscle cells, or gland cells.

endorine

signal reaches often distant targets after transport in blood

ex. insulin, human growth

from gland to area