Lecture Notes in Medical Physiology (Nervous System) for Pharmacy Students...

1. The Nervous System/Part VI
Dr. Fawaz A. Mustafa
PhD in Medical Physiology and Pharmacology
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3. Cerebellum
• The cerebellum consists of functional units of
unique features, that are about 300 million in
number arranged basically as cerebellar nuclei
which give the output of the cerebellum. These
nuclei are of three types: dentate, interposed and
fastigial nuclei. Each one of these nuclei is
concerned with certain pathway. E.g. the fastigial
nucleus is concerned with pathway related to
balance. How do these nuclei function?

4. Cerebellum
• Any tract that comes to the cerebellum for purpose
of coordination, it must, at end go to the cerebellar
nuclei as two types of fibres: climbing fibres and
mossy fibres
• These climbing and mossy fibres go to the
cerebellar cortex, and during this pathway, they
send excitatory impulses (collaterals) to the
cerebellar nuclei. Thus, excitation of the cerebellar
nuclei occurs

5. Cerebellum
• Then, the climbing fibres ascend upward to
synapse with many neurons. The most important
ones of these neurons are the purkinje neurons or
cells. Purkinje cells are inhibitory to the cerebellar
nuclei

6. Cerebellum
• At the beginning of the movement, activation of the
cerebellar nuclei occurs, and these nuclei send output
signals to the cerebral cortex. The activation of these nuclei
leads eventually to a quick and forceful movement, but we
don’t want the movement to go too far or too rapid
• To stop the movement, the cerebral cortex sends signals
(through input fibres) to activate the purkinje cells which are
going to inhibit the cerebellar nuclei
• So, there is a balance, usually in favor of excitation
(slightly). This consequently leads to turn on the agonist
muscle and turn off the antagonist muscles at the beginning
of movement and turn off the agonist and turn on the
antagonist muscles to stop the movement

7. Cerebellum
• The cerebellum is composed of about 300 million
functional units (for more information about the
functional units, see textbook of Medical
Physiology, by Guyton and Hall 13th Ed, page 721)
• The cerebellum can be also divided into three
functional zones:
1. Central zone known as the vermis
2. Intermediate zone
3. Lateral zone

8. Cerebellum
• The vermis is concerned with coordination of
movement in the truncal (proximal) region of the
body (such a, the pelvis, shoulder, trunk .. etc.).
Here, the centre of the body is presented (upside
down)
• The intermediate zone is concerned with
coordination of movement in the peripheral parts of
the body (hand, toes) since these parts are
represented in this zone
• The lateral zone involved in the planning of the
movement along with the three motor areas in the
precentral gyrus and basal ganglia

9. Cerebellum
• The cerebellum controls the same side of the body;
thus, the right cerebellar hemisphere controls the
movement in the right side of the body and vice
versa.
• Therefore, if there is anything wrong with the right
hemisphere, the movement in the right side will be
affected, and vice versa. This is because there is
double crossing in the pathway that leads to the
cerebellum and from it

10. Cerebellum
• The cerebellum, therefore, is concerned with movement
coordinating.
• For example, when the eyes move to one side, this requires
the contraction of medial rectus of one eye and the lateral
rectus of the other. The medial rectus is supplied by
oculomotor nerve while the lateral rectus is supplied by the
abducent nerve. Both of these nerves are coordinated by
the cerebellum. Rapid involuntary movement of the eye
(stagmus) is partial caused by cerebellar diseases.
• To produce speech, the cerebellum coordinates he
movement of lips, pharynx, larynx, vocal cords, and muscles
of respiration. Position of our body is coordinated and sent
to the organ of balance (ear)………

11. Brainstem
• It consists of midbrain, pons, and medulla
oblongata which continues as the spinal cord
• The brainstem is very important although it is short,
Why?

13. Brainstem
a. The sensory tracts (as dorsal columns) that pass
through the brainstem on their way upward to the
thalamus. Also, the corticospinal tracts and
descending motor tracts pass through the
brainstem. Nuclei of the cranial nerve are also
present in the brainstem (both oculomotor and
trochlear at the midbrain, trigeminal at pons, and
so until we reach the medulla oblongata in which
there is the hypoglossal ganglia). These cranial
nerves are either motor, sensory or autonomic.

14. Brainstem
b. Respiratory centre is collection of neurons
concerned with expiration and inspiration. This
centre is present in the brainstem, and so do many
other centres such as cardiovascular centre
• Therefore, the brainstem is very important for our
daily life activities
• Dysfunction of brainstem leads to clinical death

15. Brainstem
• In the brainstem, there are many neurons that are
connected to each other, forming a reticulum.
• This system of neurons is always activated,
because sensation that goes to the thalamus is
going to give collaterals to the reticular system of
neuron. This is why it is called “reticular activating
system”

16. Brainstem
• Since this system is always active, it sends nerve
fibres to many areas of the cortex and activates
them. The cortex is activated by two pathways:
1. Ascending pathways from the thalamus to the
parietal lobe of the brain, by specific pathways for
each sensory and motor
2. Collaterals of the reticular activating system

17. The Brain
1. Cerebrum: responsible for
- conscious thought processes, intellectual functions.
- memory storage & processing.
- conscious & subconscious regulation of skeletal
muscle contractions
2. Cerebellum: responsible for
- coordinating complex somatic motor patterns.
- adjust out put of other somatic motor centers in
brain & spinal cord

18. The Brain
3. Diencephalone:
- thalamus:- relays & processing centers for sensory
information.
- Hypothalamus:- controls emotions, autonomic
functions ( such as bl. Pressure, Temp.)
- hormone productions.
4. Mesencephalon:
- processing of visual & auditory data.
- generation of reflexive somatic motor responses.
- maintenance of consciousness.

19. The Brain
5. Pons:
- relays sensory information to cerebellum &
thalamus.
- subconscious somatic & visceral motor centers.
6. Medulla Oblongata: -relays sensory information
to thalamus & to other portions of the Brainstem.
- autonomic centers for regulation of visceral
functions (cardiovascular, respiratory & digestive
systems activities).

20. The Brain
• The Cranial Meninges: the layers that make up
the cranial meninges are the dura mater, arachnoid
& pia mater these are continuous with those of the
spinal cord

21. CSF
The CSF completely surrounds & bathes the exposed
surfaces of the CNS. The CSF has several
functions:
1. Cushioning delicate structures.
2. Supporting the brain. The brain floats in the CSF,
human brain weight 1400g in air but only about
50g when supported by the CSF.
3. Transporting nutrients, chemical messengers &
waste products.

22. The Cranial Nerves

23. The Cranial Nerves

24. The Cranial Nerves
1. The Olfactory Nerves (I)
Primary function: special sensory (smell).
Origin: receptors of olfactory epithelium.
Destination: olfactory bulbs.
2. The Optic Nerves (II)
Primary function: special sensory (vision).
Origin: retina of eye.
Destination: diencephalons via the optic chiasm.

25. The Cranial Nerves
3. The Oculomotor Nerves (III)
Primary function: motor (eye movements).
Origin: mesencephalon.
Destination: Somatic motor=superior, inferior &
medial rectus muscles, inferior oblique muscle,
levator palpebrae superioris muscles.
Visceral motor=intrinsic eye muscle.
4. The Trochlear Nerves (IV)
Primary function: motor (eye movement).
Origin: mesencephalon.
Destination: superior oblique muscle.

26. The Cranial Nerves
5. The Trigeminal Nerves (V)
Primary function: mixed (sensory & motor) to face.
Origin:
- ophthalmic branch (sensory)= orbital structure, nasal
cavity, skin of the forehead, upper eyelids and nose.
- maxillary branch (sensory)= lower eye-lid, upper lip, gum &
teeth, cheek, nose, palate & pharynx.
- mandibular branch (mixed)= Sensory from lower gum,
teeth & lips, palate & tongue.
Motor from motor nuclei of pons.
Destination: ophthalmic & maxillary branches to sensory
nuclei in pons, mandibular branch innervate muscles of
mastication.

27. The Cranial Nerves
6. The Abducent Nerves (VI)
Primary function: motor (eye movement).
Origin: pons.
Destination: lateral rectus muscle.

28. The Cranial Nerves
7. The Facial Nerves (VII)
Primary function: mixed (sensory & motor) to face.
Origin: sensory from taste receptors on the tongue.
motor from motor nuclei of pons.
Destination: sensory to sensory nuclei of pons.
Somatic motor= muscles of the facial expression.
Visceral motor= lacrimal (tear) glands, nasal
mucous glands, submandibular & sublingual
salivary glands.

29. The Cranial Nerves
8. The Vestibulocochlear Nerves (VIII)
Primary function: special sensory = balance &
equilibrium(vestibular branch) & hearing(cochlear
branch).
Origin: monitor receptors of the inner ear(vestibule &
cochlea).
Destination: vestibular & cochlear nuclei of pons &
medulla oblongata.

30. The Cranial Nerves
9. The Glossopharyngeal Nerves (NX)
Primary function: mixed (sensory & motor) to head &
neck.
Origin: Sensory= from posterior one-third of the tongue,
part of the pharynx & palate, carotid arteries of the
neck.
Motor= from the motor nuclei of medulla oblongata.
Destination: Sensory= to sensory nuclei in medulla
oblongata.
Motor= somatic: pharyngeal muscles (involve in
swallowing).
Visceral: parotid salivary gland.

31. The Cranial Nerves
10. The Vagus Nerves (X)
Primary function: mixed (sensory & motor) widely distributed in
thorax & abdomen.
Origin: sensory= from pharynx(part), pinna & external auditory
canal, diaphragm & visceral organ in thoracic &
abdominopelvic cavities.
motor= from nuclei in medulla oblongata.
Destination:
sensory= fibers to sensory nuclei & autonomic centers of
medulla oblongata.
motor (visceral )= fibers to muscles of the palate, pharynx,
digestive, respiratory & cardiovascular system in thoracic &
abdominal cavities.

32. The Cranial Nerves
11. The Accessory Nerves (XI)
Primary function: motor to muscles of the neck & upper
back.
Origin: motor nuclei of spinal cord & medulla oblongata.
Destination: medullary branches innervate, spinal
branches control sternocleidomastoid muscle.
12. The Hypoglossal Nerves (XII)
Primary function: motor (tongue movement).
Origin: motor medulla oblongata.
Destination: muscles of the tongue.