Download University of Jordan Faculty of Medicine L15 –Dr. Loai Physiology

University of Jordan
Faculty of Medicine
Physiology || for Pharmacy
L15 –Dr. Loai
Nervous-System
Note:
1) Make sure you understand everything, exams questions will be based on
understanding NOT memorizing alone
2) Anything between *** was not mentioned during the lecture (only for your
knowledge)
3) make sure you go through the slides for the nervous system by Dr.loai
----------------------------------------------------------------------------------------------------------The central nervous system is a complex network of nerves and cells that carry
messages to and from the brain and spinal cord to various parts of the body.
The nervous system has 3 parts:
1) Enteric nervous system  which is located in the digestive system that
processes in food digestion with minimal control from the CNS
2) Peripheral nervous system  nerves that are located in the peripheral part
of the body  its main function to transport information from the outside
(like sensation information) to the CNS & to receive orders from the CNS.
Note: all the nerves you learnt about in the anatomy course are peripheral
nerves.
3) Central nervous system  mainly we will focus on the nerves that are in
the core of the body (inside the spinal cord & the brain)  its main
function is to process the information
 Q: what does processing mean?
To edit the information and to get the main important info, this will be
sent as an output order that will go back to the peripheral and also
there might be no order!
The peripheral nervous system acts as an input device(sensory part)
and also an output device(motor part)
And between the sensory and the motor there is the integrative part
We will focus on the Central nervous system
The main function for the CNS  processing
The Nervous system from the anatomical part 
The central nervous system is divided into 3 levels:
1) The spinal cord  processing (1st level)
It will receive info and sensation from the peripheral and will send it to
the upper levels of the CNS OR will receive orders from the upper level
and after sorting and editing the info (orders) it will deliver it to the
peripheral
The spinal cord can make motor orders(output) especially those that
need a fast reflex and cannot wait until it receives the order from the
brain  it’s called spinal cord reflexes or general reflexes
For example  when you touch a very hot cup and you remove your
hand directly  this is a spinal cord reflex
2) The cerebral cortex  it is the highest & the most important level in the
CNS (the 3rd level)
Responsible for conscious movements & voluntary actions
 Q: what is the difference between conscious and voluntary?
Conscious: analysis and understanding (as a sensation)
Voluntary: movement
3) The brain stem and subcortical (the 2nd level)
Actually this level is about anything between the cerebral cortex and
the spinal cord
Its main function is processing and taking orders up to the cortex,
because the cortex is the boss of the CNS
Also it might make orders  mainly unconscious and involuntary
actions just like heart rate, pressure, body temp, emotions, and
respiration (internal environment conditions and unconscious
movements or behavior)
Examples on behavior:
1-sexual behavior
2- Hunger behavior
3- Unconscious motor behavior
 Example 1:
If you place your hand on something that causes pain such as a
needle  reflex will be from the spinal cord directly(without waiting the
subcortex or the cortex) in addition to an unconscious feeling of pain
that will reach the cortex  then you’ll figure out that the pain was from
the needle

Example 2:
If the doctor wants to take blood from you  here the cortex will
cancel the spinal cord reflex  so the cortex will keep telling that
you should not move and to relax
Functions of the cortex:
1) To receive information from the lower levels of the CNS
2) Processing and editing information
3) Build up a conscious meaning of the information that was received
4) Can send order to the lower levels to work or not to work (voluntary
movements)
5) Emotions  the cortex will try to relax you when you’re angry
6) Responsible for higher functions that need to be controlled by more
than one information, such as personality, language, thoughts, thinking
& calculations.
7) Memory ( the most important)
As we mentioned that the cortex make processing and translation of
the sensations that was received
If a new person joint us on the lecture  you will ask the doctor if he
was new or not  because when you saw his face you did not
recognize him (lets say the cortex did not recognize him)  so as a
result of the cortex processing it  the result was that he you don’t
know him
Next time he will come to the lecture  the cortex will not tell you that
he is new  and you will recognize him quickly  that is because the
cortex saved his face in the memory  because processing the cortex
is strongly related to the old memory
So we can define processing as a comparison with old memory
As a conclusion there is no memory without processing and no
processing without memory.
That’s why the storage of memory is located in the cortex(where
processing happens)
 Q: where is the memory located in the cortex?
There are four lopes and each one has its own processing and so each
lope has its own memory to use it
 For example the visual information is processed in the occipital
lope so we expect to find the visual memory there
As we mentioned the nervous system will have a sensation that will
input information  processing will occur in the cortex  if a motor
order is needed  the order will be sent from the cortex through lower
levels of the CNS  until it leaves as a motor output
Storage of the Nervous system
The nervous system is mainly composed of neurons  neurons have 4
parts:
-cell body  processing
-dendrites  processing & generating graded potential
-axon  generates and transports action potentials
-axon terminals  sends info from one neuron to another neuron
As a conclusion the shape of the cell body and the dendrites is very
important in processing
Types of neurons:
1) Unipolar dendrites-axon-axon terminal (no cell body  no
processing)
So we expect to find it abundantly in the PNS
2) Bipolar  small processing
It is found in a certain parts of the CNS but mostly in the PNS
 In the special sensations of the peripheral nervous system
3) Multipolar More than 99% of the CNS neurons
It has more than one complex dendritic tree  that converge
together and enter the cell body for processing
 There are about 35 different shapes for the multipolar in the
CNS
 Every shape is abundant in a certain part of the CNS and due to
different shapes  different processing  that is what makes it
unique and special.
 Q: what does the word pathway mean?
Group of cells of the nervous system that information need to pass by
until it reaches its destination
For example :
Visual pathwayinformation will pass from the eye until it reaches as
a special sensation to the cortex  and processing will occur
Another examplespain pathway, motor pathway,
 Q:what is faster & easier ?to use one neuron until reaching the cortex
OR 3 neurons (1 transfers to 2 and 2 transfers to 3)
Any pathway has more than one neuron
For example the pain pathway from the finger to the cortex it uses up
to 3 neurons
The question is that we used 3 neurons while 1 neurons is better !! so
why 3 neurons?
 ITS BECAUSE WE NEED PROCESSING all the way before
reaching the cortex
Processing  means we need to have a synapse
So number of neurons during the pathway  does not affect the length at
all  it affect processing only! (type of sensation)
More complex  more stops (to process) more neurons needed
the 1st neuron in the pathway (somatosensory)  did not need to make
processing  so its Unipolar
in the special sensations  we need A LOT of processing  it will be
Bipolar
 Q: what is the difference between somato-sensation and special
sensation?
Any sensation that is only in the head  special sensation
Like Vision, hearing, balance, face
Any sensation that can be found in the head and the body  somato
Like pain, temp, movement, touch, pressure & vibration
Muscle Movement, muscle length, muscle tension, joint positions 
proprioceptive sensation
*** Proprioceptive sensation: to feel. the feeling of body movement and
position, including motion of the arms and legs, resulting from stimuli
received by special sense organs in the muscles, tendons, joints, and
inner ear***
Other cells that are in the nervous tissue besides neurons:
1) Neuroglia  play a supporting role to the neurons
There are many types of Neuroglia:
 the most famous is Oligodendrocytes --> responsible for
myelination (myelin sheath: sheet that goes all round the axons to
increase speed of axons & decreases consumption of ATP in addition
to isolation)
The 2nd type is Astrocytes  has many functions:
- Mechanical support to the neuron
- Environmental support (O2 and nutrition)
- Forms blood brain barrier
Microglia is the 3rd type  similar to macrophages in the function 
its function is phagocytosis
Ependymal cells  produces cerebrospinal fluid  fills internal
cavities in the brain and the spinal cord and provides protection to the
brain.
Done by:
Rahaf Mihyar