Introduction to General Physiology

welcome to the introduction to general

physiology

my name is dr klein lim and i'll be

introducing you to a very interesting

subject

the subject that deals with how you and

i

function physiology is a science that

seeks to explain

the physical and chemical mechanisms

that are responsible for the origin

development and progression of life

each type of life for the simplest form

of virus

to the largest tree or the complicated

human beings

has its own functional characteristics

fishology is a study of the function in

the living organism

functional organization of the human

body and control of the internal

environment

the fact that we remain alive is the

result of a complex control

systems hunger makes us seek food

and fear makes us seek refuge sensations

of cold makes us look for warmth

other forces cause us to seek fellowship

and to reproduce

the fact that we are sensing feeling and

eligible beings

is part of this automatic sequence of

life

these special attributes allow us to

exist

under widely varying conditions which

otherwise

would make life impossible

cell nope nope not this cell

he's too cool for this topic i meant the

boring kind of cell

this one the boring but most functional

living unit of the body

that makes you me and everyone else

so cells are the living units of the

body

there are approximately a hundred

trillion cells

in the body imagine if that was money i

could just

imagine the possibilities of me being

robbed every day

anyways for example the red blood cell

which are the most abundant cell types

in the body comprises

approximately about 25 trillion cells

and what about the remaining 75 trillion

you may ask

other types per form functions different

from those of the red blood cells

the organization of the body starts from

the smallest atom

to molecules then a group of molecules

makes up a macromolecule an aggregation

of macromolecules makes up an organelle

which is a cell's very own organ system

similar to the organs seen in humans

such as your heart

your lungs and your intestines or etc

cells aggregate to form tissues

tissues become organs in k in this case

this is the stomach

and organ systems and then you an

organism called human being

although many cells of the body often

differ markley from one another

all of them have certain basic

characteristics that are alike

for instance oxygen which is carried by

the previously mentioned red blood cells

and delivered two different cells so

that

requires nutrition so the second one is

actually energy production

so anyways from oxygen to carbohydrates

to fats and to

proteins so the next one is to deliver

the end products of the chemical

reactions to the surrounding fluid

and in this case would be the

extracellular fluid i'll be mentioning

in a while

and lastly is the ability to reproduce

almost all cells also have the ability

to reproduce additional cells of their

own kind

fortunately when cells of a particular

type are destroyed

the remaining cells of this type usually

generate new cells

until the supply is replenished an

example would be your skin cells

so we will discuss about the body fluid

distribution

this is the intracellular fluid and the

extracellular

about 60 percent of the adult human body

is fluid

mainly of water solutions of ions and

other substances

although most of this fluid is inside

the cell and is called

intracellular fluid about one-third is

in the spaces

outside the cells and is called

extracellular fluid

this extracellular fluid is constant

motion throughout the body

much like a water inside a moving basin

in the body fluid is transported rapidly

in the circulating blood and then mixed

in between the blood

and the tissue fluids by diffusion

through the capillary walls

so we go to the extracellular fluid or

also known as the

internal environment

in the extracellular fluid are the ions

and nutrients needed by the cells to

maintain life

thus all cells live in essentially the

same environment

for this the extracellular fluid is also

called the internal environment of the

body

cells are capable of living and

performing their special

functions as long as proper

concentrations

of oxygen glucose different ions

amino acids fatty substances and other

constituents are available in this

internal environment

now in this slide here

there you will also see the parts or the

components

the solid components of an average young

adult so you will see here that proteins

make up of 80

of the body weight minerals makes up 77

and fats and other lipids makes up 15

the extracellular fluid contains large

amounts of sodium

chloride and bicarbonate ions plus

nutrients for the cells such as

oxygen glucose fatty acids and amino

acids

it also contains carbon dioxide that is

being transported from the cells to the

lungs to be excreted

plus other cellular waste products that

are being transported

to the kidneys for excretion the

intracellular fluid differs

significantly from the extracellular

fluid for example

it contains large amounts of potassium

magnesium

and phosphate ions instead of the sodium

and chloride ions found in the

extracellular fluid

this is the total body water

in relation to age and sex

homeostasis is described as the

maintenance of nearly constant

conditions in the internal environment

a much more relatable definition is that

homeostasis is any self-regulating

process

by which biological systems tend to

maintain stability

or balance essentially

all organs and tissues of the body

perform functions that help maintain

these relative constant

conditions for instance the lungs

provide oxygen to the extracellular

fluid to replenish

the oxygen used by the cells the kidneys

maintain constant ion concentrations

and the gastrointestinal system provides

nutrients

extracellular fluid is transported

through the body in two stages

the first stage is movement of blood

through the body in the blood vessels

and the second is movement of fluid

between the blood capillaries

and the intracellular spaces between the

tissue cells

all the blood in a circulatory system or

in the circulation traverses the entire

circulatory circuit

an average of once each minute when the

body is at rest

in as many as six times each minute when

a person is extremely

active

we go now to the origin of nutrients in

ecf

we will tackle each of the system below

all right so this is how oxygen is

delivered into your cells

when you inhale through your nose or

mouth air travels down the back of the

throat

passes through your larynx or voice box

and into your trachea windpipe

your trachea is divided into two air

passages called bronchial tubes

the bronchial tubes divide into smaller

air passages called bronchi

and then into bronchioles the bronchials

end in tiny air sacs called alveoli

where oxygen is transferred from the

inhaled air to the blood

after absorbing oxygen the blood leaves

the lungs and is carried to the heart

the blood then is pumped through your

body to provide oxygen to the cells of

your tissues and organs

[Music]

when cells use oxygen carbon dioxide is

produced and transferred to the blood

your blood carries the co2 back to your

lungs and it is removed when you exhale

other systems include gip which absorbs

dissolved nutrients into the ecf

the liver and other organs of metabolism

changes chemical composition of

many absorbed substances to usable forms

and the musculoskeletal system aids the

body to

obtain food and provides mortality for

protection against adverse surroundings

next up is the removal of metabolic end

products

alright so we'll first discuss the

removal of carbon dioxide by the lungs

at the same time that blood picks up

oxygen in the lungs

carbon dioxide is released from the

blood into the lung alveoli

and is then carried outside of the body

carbon dioxide is the most abundant of

all the metabolic products passage of

blood through the kidneys removed from

the plasma most of other substances

beside carbon dioxide

are not needed by the cells most of the

other substances that are not needed by

the body

especially metabolic waste products such

as urea are reabsorbed poorly

and pass through the renal tubules into

the urine

the gastrointestinal tract process

undigested materials that enter the

gastrointestinal tract and some waste

products of metabolism

and are then eliminated in the feces

the liver and among the functions of the

liver is a detoxification

or removal of many drugs and chemicals

that are ingested

the liver secretes many of these wastes

into the bile

to be eventually eliminated in the feces

is it getting too boring see i'll make

it a bit more fun for us

for your disclaimer nothing personal so

um there are different systems in the

body that acts to regulate the body for

it to function properly

and this is what we are going to talk

about the regulation of

body functions the nervous system

this is a literally a system that will

make you sweat

fight run sleep or digest that lunch you

just

had for me it was actually a cc bryce

boss with hot shots at kfc

parkman the nervous system is composed

of three major parts

the sensory input portion the central

nervous system or integrative portion

and the motor output portion

sensory receptors detect the state of

the body

or the state of the surroundings for

instance s receptors in the skin alert

us whenever an object touches the skin

at any point the eyes are sensory organs

that give us a visual image of the

surrounding area

and the ears are also sensory organs

the central nervous system is composed

of the brain and the spinal cord

the brain can store information generate

thoughts

create ambition and determine reactions

that the body performs in response to

the sensation

appropriate signals are then transmitted

through the motor output portion of the

nervous system

to carry out at once desires an

important segment of the nervous system

is called the autonomic system

it operates at the it operates at a

subconscious level

and controls many functions of the

internal organs including the

level of pumping activity of the heart

movements of the gastrointestinal trap

and secretions by many of the body's

glands

located in the body are eight major

endocrine glands and several organs and

tissues that secrete chemical substances

called

hormones hormones are transported in the

extracellular fluid

to other parts of the body to help

regulate cellular function

oxytocin is a hormone secreted by

posterior lobe of the

pituitary gland a pea-sized structure at

the base of the brain

and some might argue that this is

actually the love hormone

and these are some other boring examples

which you will need to learn later

on to pass the subject

the nervous system regulates many

muscular and secretory activities of the

body

whereas the hormonal system regulates

many metabolic functions

so in summary the nervous and the

hormonal systems

normally work together in a coordinated

manner to control essentially

all of the organ systems of the body

then we go to the protection of the body

for the systems that protect the body

from harmful organisms like your ex

you only have two only two doki you may

ask

yes that's your immune system which acts

like your family that supports you and

you just broke up

and the other one is your skin the

integumentary system which acts like

more like yourself

sorry

for the immune system the immune system

consists of the wide

varieties of white blood cells tissue

cells derived from white blood cells the

thymus lymph nodes

and lymph vessels that protect the body

from pathogens such as bacteria

viruses parasites and fungi

so that's why i mentioned that they act

like a family because they support you

and fight for you

the immune system provides a mechanism

for the body

to number one distinguish its own cells

from foreign cells and substances like

your mom

and n2 destroys the invader by

phagocytosis

your dad who eats your ex alive or by

producing lymphocytes or

specialized proteins example antibodies

that is destroy

or neutralize the invaders like your

siblings

the integumentary system the skin and

its various appendages

including the hairs the nails the glands

etc

cover cushion and protect the deeper

tissues and organs of the body

and generally provide a boundary between

the body's internal environment which is

your emotions

and outside world your ex

please the integrity the integumentary

system

is also important for temperature

regulation and excretion of wastes

and it provides a sensory interface

between the body

and external environment the skin

generally comprises about twelve

to fifteen percent of the body weight

reproduction

sorry a tabler

ain't a covalent angler is a powerpoint

sometimes reproduction is not considered

a homeostatic function

it does however help maintain

homeostasis by generating

new beings to take the place of those

that are dying

this may sound like a permissive usage

of the term homeostasis

but it illustrates that essentially all

body structures are organized

such that they help maintain the

automaticity

and continuity of life all right so

let's just take a break

around 10 to 15 minutes

lecture

all right so this topic explains a

different access that you might

or may have in the future

in three minutes

so this is actually the control systems

of the body

the human body has thousands of control

systems

so some of the most intricate of these

systems are the generic control systems

that

operate in all cells to help control

intracellular and

extracellular functions

for instance the respiratory system

operating in association with the

nervous system regulates the

concentration of carbon dioxide

in the extracellular fluid the liver and

the pancreas regulate

the concentration of glucose in the

extracellular fluid

and the kidneys that regulate

concentration of hydrogen

sodium potassium phosphate

and other ions in the extracellular

fluid

here are examples of control systems so

number one we have regulations of oxygen

and carbon dioxide concentrations in the

extracellular fluid

and the other one is a regulation of

arterial blood pressure

so now we are going to first discuss the

regulation of oxygen

and carbon dioxide concentrations in the

extracellular fluid so this story is

actually

a bit relatable so imagine that you are

a sedentary individual

here like cell and you originally

planned to take the school elevator to

get in class

but found out that it was not working

mugs get close

and so you decide to take the stairs all

the way up to the fourth floor

as you go up the stairs

there is an increase in the carbon

dioxide concentrations

which excites respiratory centers in the

brain

breathing increases rapidly and deeply

thus eliminating carbon dioxide

from the blood and the ecf

and thus you have a happy cell so this

is how the nervous system mechanisms

maintains constant and reasonable co2

concentrations in the ecf

all right so for the second one that

we're going to talk about is the

regulation of

arterial pressure and as a definition

bioreceptors are pressure receptors in

walls of blood vessels

such as the carotids and the aorta

an increase in the arterial pressure

stretches

walls of the big arteries and inhibits

the vasomotor center such as the medulla

and the pons

thereby the number of impulses to the

heart and the blood vessels via

sympathetic nervous system

also decreases which leads to a decrease

in activity of the heart as it pumps

at the same time blood flow through the

peripheral vessels also decreases

thus arterial pressure is lowered back

to normal

a fall in arterial pressure relaxes the

stretch receptors

which allows the vasocenters or the

vasomotor centers

to become more active than usual thereby

causing

pressure to rise back towards normal

all right so this is the last topic this

is the characteristics of control

systems

we will be talking about negative

feedback mechanism and the positive

feedback mechanism

[Music]

did you know just sitting here right now

you're doing something

absolutely remarkable well you

your cells tissues organs organ systems

yes we just leveled up those biological

levels of organization

they're all working towards something

called homeostasis

it's a state of balance yes homeostasis

means many things in your body

for example that your blood stays within

a certain ph level range

it means that your blood glucose remains

within a certain range

it means your internal body temperature

stays within a certain range

see we've mentioned the major body

systems before and that they work

together

and today we're going to talk about how

they work together using something

called

positive and negative feedback and also

how this relates to homeostasis

so many years ago i had a pet bearded

dragon

her name was debbie and she was the best

lizard ever debbie used to sit on her

couch with me when i'd watch tv

and she'd love to have her chin

scratched i even got her a bearded

dragon leash

so i could take her outside yeah they

make those anyway debbie loved her heat

lamp

she would sit under the heat lamp on her

rock and when she got too hot

she would get off her rock and out of

the heat lamp range and

go somewhere else she had a huge

enclosure too because

i wanted debbie to be a happy lizard so

she could find an ideal temperature why

all this talk about debbie

well debbie is an example of an animal

that some people refer to as

cold blooded or a fancier term ectotherm

we actually like the fancier term a bit

better though because her blood isn't

necessarily

cold her body temperature can fluctuate

with the environment but not you you are

warm blooded or the fancier term an

endotherm

your body works hard to keep the

internal temperature it keeps

it's also a beautiful example of

something called negative feedback

before we define it let us show you this

example say you're in an environment

that is very hot

like being outside in the texas summer

heat that's typically hot

thanks to nerves which can act as

sensors the brain notices this

it will send signals to counteract this

variable

sweat glands do what they do best sweat

what heat is lost is that sweat

evaporates off your skin you may have

some redness too that's because

your blood vessels are getting wider

dilating

in order to help get rid of that heat

the result

whether you realize it or not helps you

lower your body temperature

but wait what if you go inside now and

the ac is blasting

you'll stop sweating you may even shiver

the muscle contractions of shivering can

generate heat

and those blood vessels will now

decrease in diameter size

constrict to help you conserve the heat

because that makes it harder for

the heat to escape your body temperature

can increase then

this is negative feedback so a

simplified definition

negative feedback is when some variable

triggers a counteracting response

in order to come back to some set point

if we consider that this whole thing is

actually a negative feedback loop we can

see that the negative feedback

brings the body back to the set point

which in this case

is a stable temperature keeping

homeostasis

negative feedback is also going on in

the regulation of your glucose

your blood sugar okay we're really

simplifying this here

as we often do but when glucose blood

sugar

is too high one hormone that is released

is insulin

i always imagine insulin is this hormone

that makes the cells say bid me

because it has the ability to make cells

take in glucose

on the flip side if glucose is too low

in the blood

a hormone called glucagon can be

released

this hormone can have many effects and

one of them is that it can cause the

liver

to release glucose into the blood

there's more to the regulation of blood

sugar than this but

you can see how this is negative

feedback you have counteracting

responses here in order to keep

homeostasis

so what about positive feedback positive

feedback is when

instead of getting a counteracting

response to some variable

you instead intensify the variable

positive feedback can be like

more and more instead of let's

counteract this

the example that always stuck with me

when i was a student

is the example about the human baby

being born biology classrooms everywhere

it's a classic example

when a human baby is ready to be born

there is pressure on the cervix

and that pressure and the hormones

involved cause contractions of the

uterus

because that's a big part about how the

baby is going to be born

more release of hormones will equal more

contractions and pressure

which will cause more release of

hormones and more release of hormones

will mean more contractions and pressure

contractions help get the baby out but

it's also a part of a beautiful

illustration

of what positive feedback can do so why

do we care about feedback

other than you know the importance of

negative feedback in maintaining

homeostasis

and the role of positive feedback in

many body processes

well we also need to understand feedback

so we can understand

what is happening when there is a

problem helping back systems

one example perhaps you've heard of type

1 diabetes

it's a disorder that can mean that your

pancreas which is an organ that is

involved with making some hormones like

insulin

is not working correctly insulin is not

produced

and because of that one issue is that

you're not going to be able to get

glucose the blood sugar into your cells

glucose outside of the cells cannot be

used in cellular respiration

the cells need to take the glucose in to

make atp energy and cellular respiration

therefore your cells need to be able to

take in the glucose to survive so many

type 1 diabetics

need to give themselves insulin and

monitor their blood sugar

because the negative feedback may not

work as it should

well well that's it for the amoeba

sisters and we remind you to stay

curious

[Music]

all right so why do most control systems

are too badly operate by negative

feedback

rather than positive feedback if one

considers the nature of positive

feedback

it is obvious that positive feedback

leads to instability

rather than stability and in some cases

can cause death

but positive feedback can sometimes be

useful

in some instances the body uses positive

feedback to its advantage

blood clotting is an example of a

valuable use of positive feedback

and as stated in the video also during

childbirth

all right so sorry this is actually a

busy slide

so as a clarification from the video

there are more complex types of control

systems known as adaptive control as we

proceed

in depth with general physiology you

will learn that systems contain a great

number of interconnected control

mechanisms

adaptive control is also known as a

delayed negative feedback

for instance some movements of the body

occur so rapidly

that there is not enough time for nerve

signals to travel from the peripheral

parts of the body all the way to the

brain and then back to the periphery

again to control the movement

therefore the brain uses a principle

called feed

forward control to cause required muscle

contractions that is

sensory nerve signals from the moving

parts

apprise the brain whether the movement

is performed correctly

or if not the brain corrects the feed

forward signals that it sends

to the muscles the next time the

movement is required

then if still further correction is

needed this

process will be performed again for

subsequent movements

so again and again is your brain's way

of learning think about it

and an example of which might be when

something falls from a table at first

you won't be able to catch it

but as it subsequently occurs during the

times

you immediately catch it correct

all right so this is actually my last

slide the purpose of this chapter has

been to point

out first the overall organization of

the body

and second is the means by which the the

different parts of the body operate in

harmony so to summarize the body

is actually a social order of about 100

000 trillion cells organized into

different functional structures

some of which are called organs and each

functional structure contributes its

share to the maintenance of homeostatic

conditions

in the extracellular fluid which is

called

the internal environment as long as the

normal conditions are maintained in this

internal environment

the cells of the body continue to live

and function properly

each cell benefits from homeostasis and

in turn

each cell contributes its share

toward the maintenance of homeostasis

this reciprocal interplay provides

continuous automaticity of the body

until one or more functional systems

lose their ability to

contribute their share of function

when this happens all the cells of the

body suffer

extreme dysfunction leads to death

moderate dysfunction leads

to sickness or diseases so

congratulations for making it to the end

of this video

i hope you had fun watching it as much

as much as i

enjoyed making this video i hope you

learned something from this introduction

thank you