Transcript central nervous system

Human Body Systems
Understanding how our body’s
systems work and how they interact
1. The Digestive System
The role of the digestive system is to process the
food you eat so that the nutrients and minerals
become available to your body.
We will take a closer look at the journey of food from
the time it enters your mouth, its fate inside the body,
until it is finally excreted as waste.
Types of Digestion
When we are referring to digestion there are two
types:
mechanical digestion - involves the physical
breakdown of food onto very small pieces
chemical digestion - involves the breakdown of
large particles into smaller particles by chemical
substances called enzymes
These two types occur in several places along the
path
The Major Organs
The food you eat will follow the digestive pathway
through the following major organs:
1. mouth (oral cavity)
2. esophagus
3. stomach
4. small intestine
5. large intestine
6. rectum
We will take a closer look at the role of each organ.
The Supporting Cast
Alongside the major organs, there are other organs
that play a role in the digestion of your food. These
include:
- pancreas
- liver
- gall bladder
Though food never enters these organs, they also
have an important role in digestion.
The Mouth
Digestion begins as soon as food enters the mouth.
- mechanical digestion happens when you chew food
- your food mixes with your saliva which contains
enzymes, thus chemical digestion also occurs in
your mouth
- the enzymes in your saliva help to digest large
starch molecules into smaller sugar molecules
You are ready to swallow... your tongue helps!
The Esophagus
The esophagus is the soft-tissue tube that connects
your mouth to your stomach.
- as you swallow, food is funneled into the
esophagus
- food is moved down to your stomach by a wave-like
movement known as peristalsis (contraction of
muscles that lines the esophagus)
The Stomach
Food enters the stomach and chemical digestion
occurs with a bit of mechanical help.
- the muscular wall of the stomach churns up the
food mixing it with secretions from the wall of the
stomach, known as gastric juice
- gastric juice is composed of mucus, hydrochloric
acid, water and digestive enzymes
- enzymes and acid chemically digest proteins into
smaller particles
The Small Intestine
The stomach slowly releases food, which is now
liquid, into the small intestine.
- chemical digestion continues here
- together with enzymes produced by the wall of the
intestine, the pancreas sends digestive enzymes into
the small intestine which work to complete the
breakdown of starches and particles into very tiny
particles
- bile is produced by the liver and stored in the gall
bladder
Small Intestine... continued
- the gall bladder sends bile into the small intestine
where it breaks up large fat globules into smaller
ones
- the small intestine absorbs nutrients and transfers
them to the blood stream to be circulated in the body
- the inner wall surface of the small intestine is lined
with finger-like projections called villi
- villi increase the surface area through which the
nutrients are absorbed
The Large Intestine
Mechanical and chemical digestion are complete by
the time food reaches the large intestine.
- the role of the large intestine is to reabsorb water,
along with some vitamins and minerals that the body
needs
The Rectum
The undigested parts of food are formed into feces
and collected in the rectum until the body is ready to
excrete it as waste from the body.
2. The Respiratory
System
The respiratory system is responsible for supplying
your blood with oxygen and removing the carbon
dioxide from your blood and returning it to the air
outside your body.
Your body performs this gas exchange through a
process called breathing.
Major Structures
The respiratory system includes the following
structures:
1. nasal/oral cavity
2. trachea
3. bronchi
4. bronchioles
5. alveoli
Your breathing also relies on the diaphragm.
The Nasal/Oral Cavity
The first part of the respiratory tract is made up of
the nose and nasal cavity.
Air that enters through the nasal cavity is warmed,
moistened, and cleaned before it travels any further.
Air can also enter the respiratory tract via the oral
cavity, however this air will not be warmed,
moistened, or filtered as is air that enters through the
nasal cavity.
The Trachea
The trachea is a rigid tube made up of cartilage
located at the front of the neck and acts as a
passage for air traveling to and from the lungs.
The structure needs to be rigid so that the trachea
will not collapse while breathing.
The Bronchi
The bronchi are a set of tube-like passageways that
branch off the main trachea toward each of the
lungs.
They are lined with tough connective tissue to
prevent collapsing.
The Bronchioles
The main bronchi then branch off into several
bronchioles which are much more narrow and will
allow the air to pass through.
The branching produces progressively smaller
diameter tubules.
The Alveoli
Alveoli are tiny air filled sacs found at the ends of the
bronchioles.
The alveoli are made up of specialized epithelial
tissue which is only a single cell layer thick.
Alveoli are surrounded by capillaries (tiny blood
vessels)
Gas exchange occurs at the alveoli by way of
diffusion
Gas Exchange
Oxygen-rich air is transferred from the lungs to the
bloodstream at the alveoli. Oxygen is then carried
throughout the body to cell that are in need.
Blood rich in carbon dioxide is transferred from the
bloodstream to the lungs, again, through the alveoli.
Gases are exchanged by means of diffusion through
the membranes of cells.
(diffusion - the tendency of material to move from
an area of high concentration to an area of low
concentration)
The Role of the
As stated previously,
your breathing relies on the
Diaphragm
contraction and relaxation of muscles in the
diaphragm.
Inhalation - when you inhale, your diaphragm
muscles contract causing it to be pulled down and
your ribs to be pulled up. This creates and increase
in the size of your chest and lungs, thus pulling air
into your lungs.
Exhalation - when you exhale, the opposite is true.
The muscles in the diaphragm relax; ribs go down;
diaphragm goes up; decrease size; thus forcing air
out.
3. The Circulatory
System
The circulatory system is your body’s transportation
network.
The role of the circulatory system is to transport and
deliver nutrients absorbed by your digestive system,
transport oxygen to your cells, and to remove waste
products.
Major Players
Your blood constantly travels throughout your body
through a complex network that includes:
1. heart
2. arteries
3. capillaries
4. veins
5. blood
Let’s take a closer look at each of these...
The Heart
The heart is the body’s main pumping station. It is
made up of muscular tissue that contracts and
relaxes to allow blood to flow both into and out of the
heart.
Your heart pumps carbon dioxide-rich blood to the
lungs so that the carbon dioxide waste can be
exhaled; while the blood that is high in oxygen is
pumped to all other parts of your body.
Your heart muscles are strong enough to force blood
to travel up to your brain and all the way dow to your
toes!
Blood Vessels
Blood vessels are made up of three types of tissue:
- connective tissue on the outside
- muscle tissue in the middle
- epithelial tissue on the inside
Each type of blood vessel carries out a specialized
function and therefore each a bit different in
structure.
The Arteries
These are the blood vessels that carry the oxygenrich blood away from your heart to be delivered to all
parts of the body.
Arteries have a thick, muscular layer that expands
and contracts to help push blood along
You can feel this expansion of your arteries as a
pulse.
The Veins
These blood vessels return blood that is rich in
carbon dioxide back to your heart so it can then be
pumped into your lungs where it will undergo an
exchange of gases.
Veins are thinner and have valves that stop the blood
from flowing backward.
The Capillaries
These are highly specialized blood vessels that are
located between arteries and veins.
Capillaries have two adaptations that make them
suitable for exchanging gases and nutrients:
1. they are made up of specialized epithelial tissue
that
is only one cell layer thick
2. they are very narrow so that blood cells must pass
through in single file
These adaptations increase the rate of diffusion.
The Blood
Believe it or not... Blood is the second largest
example of connective tissue in your body!
Blood is made up of red blood cells, white blood
cells, platelets, and plasma (the liquid portion of your
blood).
Plasma makes up 55% of your blood while the other
parts combine to make up the other 45%.
Plasmas transports nutrients to your cells and carries
wastes such as CO2 away.
Blood... continued
RBCs are the oxygen carriers. To maximize the
amount of oxygen they carry, RBCs have no
nucleus.
WBCs are specialized to fight infection. Some are
capable of ‘eating’ bacteria at infectious sites like
cuts.
Platelets are cells that help stop bleeding at cuts.
They are responsible for clotting of the blood.
The Circulatory system and the Respiratory system
work together very closely to ensure the proper
function of the body.
4. The Excretory System
Your body produces a number different wastes.
These wastes are poisonous an can cause serious
harm if they are not removed from the body.
The role of the excretory system is to get rid of
waste!
What Kind of Waste?
As we have discussed previously, the body produces
carbon dioxide as a waste product and it is removed
from the blood by the lungs.
Ammonia is a very toxic waste product that is
produced when cells break down proteins.
Water and Salts are produced as waste when certain
chemical processes take place in the cells.
Major Organs
Some of the organs required for waste removal are
also a part of other systems in the body. They
include:
1. liver
2. kidneys
3. bladder
4. ureters and urethra
5. skin
We will discuss the processes for the removal of
different of waste products.
The Liver
Although the liver is involved in digestion, it plays a
major role in the excretory system as well.
It is responsible for taking the highly toxic ammonia,
that is produced by cells, out of the bloodstream and
converting it into a less harmful substance called
urea.
Urea is less harmful but must still be disposed of.
Urea is released into the bloodstream on its way to
the kidneys
The Kidneys
The kidneys act as filters for the blood as they strain
out any unwanted urea, water, and other salts, and
they produce urine.
Every drop of your blood is filtered 300 times a day!
Even though about 180 L of blood pass through the
kidneys, you produce only about 1.5 L of urine.
The amount of urine depends on how much water
you drink.
The Formation of Urine
The blood enters the kidney by the renal artery. This
artery branches into smaller and smaller vessels.
These capillaries enter filtering units called
nephrons.
Nephrons are microscopic units that remove waste
from the blood and produce urine.
The “clean” blood returns to the body through the
renal vein, while the urine flow out a separate vessel
and into the ureter.
Ureters, Bladder, &
Urethra
Ureters are long tubes that connect the kidneys to
the bladder.
The bladder is a sac covered in muscle tissue. The
bladder expands as the urine enters. Your bladder
can store about one litre of urine!
When the bladder is full, the muscles contract and
push the urine out though the urethra.
The Skin
Your skin has thousands of tiny sweat glands just
below the surface.
In addition to producing sweat to keep you cool,
these glands remove excess salt from your blood.
When you sweat, you are excreting waste!
Did You Know...
Urine can reveal disease.
Certain diseases can affect how the kidneys
function, and these changes will show up in urine
samples.
Proteins in the urine will denote kidney failure.
Glucose in the urine is often a sign of diabetes.
Doctors analyze urine samples to gain insight to how
well your body systems are functioning.
5. The Nervous System
The role of the nervous system is to monitor and
respond to internal and external stimuli.
A stimulus is anything that causes a response in an
organism. For example, you shiver when it’s cold; a
goalie makes a save; your stomach produces gastric
juice in response to food arriving in the stomach; etc.
Major Role Players
The nervous system is mostly made up of one type
of tissue called nervous tissue.
Nervous tissue is made entirely of specialized cells
called neurons.
The nervous system is made up of:
1. brain
2. spinal cord
3. nerves
How the Nervous System
is Organized
The nervous system can be thought of as two major
systems:
- the central nervous system (composed of the
brain and spinal cord)
- the peripheral nervous system (made up of the
cranial and spinal nerves)
Peripheral Nervous
System
Each nerve in the peripheral nervous system is
made of of sensory neurons (which carry information
from the body to the CNS) and motor neurons
(which carry information from the CNS to the
muscles or organs.
The peripheral nervous system can be sub-divided
into two categories:
1. somatic nervous system - control voluntary
responses
2. autonomic nervous system - control automatic
responses
Central Nervous System
The brain receives stimuli from the outside world,
gathered by the sense organs: eyes, ears, mouth,
nose, and skin.
The brain also receives stimuli from the body itself.
The brain reacts to stimuli and sends messages to
the appropriate body parts.
The spinal cord connects the brain to the PNS, and
acts as a highway for messages b/w brain and body.
Reflex Response
A reflex is when sensory and motor neurons work
together and respond without involving the brain. It
is an automatic response by the nervous system to
an external stimulus.
Reflexes protect you from injury by reducing the time
it takes to react to harmful stimuli.
Sense of Touch
Unlike your other senses, the sense of touch is found
in all areas of your skin (making it the largest sense
organ).
When blind people read braille, there is a reason
why they use their fingers... they are loaded with
touch receptors.
Neuron
Question?
How might the structure of a neuron help to carry out
its function?