brain physiology

1. Gross Anatomy
of the Brain
Tatia Gakharia, MD, PhDs, 2023

2. The brain performs the most complex neural functions—those associated with
intelligence, consciousness, memory, sensory-motor integration
• the brain also controls basic life-sustaining activities—heart rate, respiratory rate,
and maintenance of blood pressure
• Furthermore, through the cranial nerves that attach to it, the brain is involved in
innervation of the head

3. Part of the central nervous system (CNS) that lies within the cranial
vault—the encephalon.
Weighs 350 g in the newborn and 1,400 g in the adult.

4. Its surface is
convoluted
and exhibits
gyri and
sulci.

5. • consists of the cerebrum (cerebral
hemispheres and diencephalon), the
brainstem (midbrain, pons, and medulla), and
the cerebellum.

6. The brain is classified into six postembryonic divisions: telencephalon,
diencephalon, mesencephaIon, pans, medulla oblongata, and
cerebellum.

7. 4th week of development- three primary brain vesicles appear three
vesicles are the prosencephalon or forebrain; the mesencephalon , or midbrain; and the rhombencephalon or
hindbrain.
4th week the three primary vesicles give rise to five secondary brain vesicles .The
prosencephalon divides into the telencephalon (“endbrain”) and the diencephalon (“through-brain”). The
mesencephalon remains undivided, but the rhombencephalon divides into the metencephalon (“afterbrain”) and
the myelencephalon (“brain most like the spinal cord”).

8. • Finally, the central cavity of
the neural tube enlarges in
certain regions to form the
hollow ventricles
Note that the word stem encephalos
means “brain.”)

9. Telencephalon-
Cerebrum
consists of the cerebral hemispheres and the basal nuclei. The
cerebral hemispheres contain the lateral ventricles.
1. Cerebral hemispheres separated by the longitudinal
cerebral fissure and the falX cerebri.
2. interconnected by commissural fiber bundles (e.g., corpus
callosum).
3. consists of 6 lobes and the olfactory structures:
Frontal, parietal, temporal,occipital, insular, limbic
• Elevated ridges of tissue called gyri
• shallow grooves called sulci
• Deeper grooves, called fissures, separate large regions of the brain

10. Brodmann, the cerebral cortex mapped

11. Bordering the central sulcus are two important
gyri, the precentral gyrus anteriorly and the
postcentral gyrus posteriorly. The occipital lobe,
which lies farthest posteriorly, is separated from
the parietal lobe by several landmarks, the most
conspicuous of which is the parieto-occipital sulcus
on the medial surface of the hemisphere. On the
lateral side of the hemisphere,the flaplike temporal
lobe is separated from the overlying parietal and
frontal lobes by the deep lateral sulcus, which is
so deep that, despite its name, it is actually a
fissure.
Sulci:
• Central sulcus
• Lateral sulcus
• Parieto-occipital sulcus
• Calcarine sulcus

12. a. Frontal lobe-extends from the central sulcus to the frontal pole. lies superior to the lateral sulcus and
anterior to the central sulcus.
• made up of the following gyri:
• 1.Precentral gyrus consists of the primary motor
area (area 4)
• 2.Superior frontal gyrus contains supplementary
motor cortex on the medial surface (area 6).
• (3) Middle frontal gyrus contains the frontal eye
field (area 8).
• (4) Inferior frontal gyrus contains the Broca speech
area in the dominant hemisphere (areas 44 and
45).
• (5) Gyrus rectus and orbital gyri separated by the
olfactory sulcus.
• (6) Anterior paracentral lobule found on the medial
surface between the superior frontal gyrus
(paracentral sulcus) and the central sulcus.
represents a continuation of the precentral gyrus
on the medial surface

13. Frontal Lobe
• Neurological deficits
• The following neurological deficits occur with unilateral or bilateral
• deficits arising from unilateral dominant side lesions:
• Broca aphasia: expressive aphasia
• problems with repetition
• destruction of frontal eye field: impaired gaze to the contralateral side
• hemiparesis/hemiplegia
• deficits arising from unilateral non-dominant side lesions:
• hemiparesis/hemiplegia
• deficits arising from bilateral lesions:
• intellectual impairment
• personality change
• disinhibition
• apathy
• abulia (loss of drive)
• urinary incontinence
• Foster Kennedy syndrome (lesions in the olfactory groove
contralateral papilloedema

14. Parietal lobe extends from the central sulcus
t0 the occipital lobe and lies superior to the
temporal lobe. contains the following lobules
and gyri:
• (1) Postcentral gyrus the primary somatosensory area of the cerebral
cortex (areas 3, 1, and 2).
• (2) Superior parietal lobule comprises association areas involved in
somatosensory functions (areas 5 and 7).
• (3) Inferior parietal lobule Supramarginal gyrus a. interrelates
somatosensory, auditory, and Visual inputs (area 40). Angular gyrus
(area 39) b. receives impulses from primary Visual cortex.
• (4) Precuneus located between the paracentral lobule and the
cuneus. (5) Posterior paracentral lobule located on the medial surface
between the central sulcus and the precuneus. represents a
continuation of the postcentral gyrus on the medial surface

15. Parietal Lobe
• Neurological deficits
• The following neurological deficits occur with unilateral or bilateral lesions of the parietal lobes 4:
• deficits arising from unilateral lesions involving the dominant hemisphere:
• Gerstmann syndrome: right-left disorientation, finger agnosia, agraphia (without
• contralateral hemianopia
• sensory loss
• contralateral neglect (less common than non-dominant)
• bilateral astereognosis: inability to identify an object by touch alone
• deficits arising from unilateral lesions involving the non-dominant hemisphere:
• contralateral sensory loss
• contralateral neglect
• contralateral hemianopia
• topographic memory loss
• anosognosia: impaired self-awareness
• dressing apraxia
• irritative lesions involving either lobe can give rise to focal seizures involving the contralateral
march (seizures spreading up/down the sensory strip (begins on one side; may begin with
forearm, arm, face and leg; Todd's paresis may ensue))

16. Temporal lobe- extends from the
temporal pole to the occipital lobe,
lying inferior to the lateral sulcus.
extends from the lateral sulcus to the
collateral sulcus. contains the following
gyri:
• (1) Transverse temporal gyri of Heschl found within
the lateral sulcus. extends from the superior
temporal gyrus toward the medial geniculate body).
contains the primary auditory areas ofthe cerebral
cortex (areas 41 and 42).
• (2) Superior temporal gyrus associated with auditory
functions. contains the Wernicke speech area in the
dominant hemisphere (area 22). contains the
planum temporale on its superior (hidden) surface.
• (3) Middle temporal gyrus
• (4) Interior temporal gyrus
• (5) Lateral occipitotemporal gyrus (fusiform gyrus)
lies between the inferior temporal sulcus and the
collateral sulcus

17. Temporal Lobe
• Neurological deficits
• The following neurological deficits occur with unilateral or bilateral
lesions of the temporal lobes 7:
• deficits arising from unilateral lesions involving the dominant
hemisphere:
• alexia: acquired dyslexia (inability to read)
• agraphia: inability to write
• acalculia: inability to calculate
• Wernicke's dysphasia: receptive dysphasia
• nominal dysphasia: inability to name objects (lesions involving the
superior temporal lobe)
• contralateral homonymous superior quadrantanopia: 'pie in the
defect (due to disruption of Meyer's loop which dips into the
• deficits arising from unilateral lesions involving the non-dominant
hemisphere:
• contralateral homonymous superior quadrantanopia
• prosopagnosia: failure to recognise faces
• irritative lesions involving either lobe can give rise to the following:
• formed visual hallucinations
• focal seizures
• memory disturbances (e.g. déjà vu and other memory
disturbances)

18. Occipital lobe lies posterior to a line connecting the parieto-occipital sulcus and the preoccipital notch
• contains two structures:
• (1) Cuneus situated between the
parieto-occipital sulcus and the
calcarine sulcus. contains the
Visual cortex (areas 17, 18, and
19). (2) Lingual gyrus lies inferior
to the calcarine sulcus. contains
the Visual corteX (areas 17, 18,
and 19).

19. Occipital Lobe
• Neurological deficits
• The following neurological deficits occur with
bilateral lesions of the occipital lobes 11:
• deficits arising from unilateral lesions
hemisphere:
• hemianopia: retrochiasmal lesion (lesions involving
thalamic lateral geniculate nucleus, occipital lobe)
• colour dysnomia: interruption of fibres streaming
cortex to the Wernicke's area
• Anton syndrome: those who suffer cortical blindness
adamantly that they are able to see
• irritative lesions involving either lobe can give
following:
• visual hallucinations (e.g. seeing flashes of light)

20. Insular lobe (insula)- lies within the lateral sulcus. has short and long gyri. f. Limbic lobe a C-shaped
collection of structures found on the medial hemispheric surface that encircles the corpus callosum and the lateral aspect of
the midbrain. includes the following structures:
• (1) Paraterminal gyrus and
subcallosal area located anterior
to the lamina terminalis and
inferior to the rostrum of the
corpus callosum.
• (2) Cingulate gyrus parallel and
superior to the corpus callosum.
merges with the
parahippocampal gyrus.
• (3) Parahippocampal gyrus1 lies
between the hippocampal and
collateral sulci and terminates in
the lIIIClIS.
• (4) Hippocampal formation lies
between the choroidal and
hippocampal fissures. connected
to the hypothalamus and septal
area Via the fornix. includes
three structures: a. Dentate
gyrus b. Hippocampus and c.
Subioulum

21. Olfactory structures- found on the orbital surface
of the brain and include the following:
• (1) Olfactory bulb and tract
an outpouching of the
telencephalon. (2) Olfactory
bulb receives the olfactory
nerve (CN 1).
• (3) Olfactory trigone and
striae
(4) Anterior perforated substance created
by penetrating striate arteries.
(5) Diagonal band of interconnects the
amygdaloid nucleus and the septal area

22. Basal nuclei (ganglia) constitute
the subcortical nuclei of the
telencephalon.
• include the following structures:
• a. Caudate nucleus part of the
striatum, together with the
putamen. b. Putamen part of the
striatum, together with the
caudate nucleus. part of the
lentiform nucleus along with the
globus pallidus.
• c. Globus pallidus part of the
lentiform nucleus, together with
the putamen.
• d. Subthalamic nucleus part of
the diencephalon that functions
with the basal nucle

23. Basal nuclei: caudate nucleus putamen, and
globus pallidus
• caudate nucleus +the
putamen= forms the striatum
• the putamen + globus pallidus
= lentiform nucleus
in motor activity, the basal nuclei are particularly
important in starting, stopping, and monitoring
the intensity of movements executed by the
cortex, especially those that are relatively slow or
stereotyped, such as arm-swinging during
walking. Additionally, they inhibit antagonistic or
unnecessary movements. Disorders of the basal
nuclei include Huntington’s disease and
Parkinson’s disease

24. White matter includes the
cerebral commissures and
the internal capsule.
•
•

25. • Anterior commissure located in
the midsagittal section
between the lamina terminalis
and the column of the forniX.
interconnects the olfactory
bulbs with the middle and
inferior temporal lobes.
• (3) Hippocampal commissure
(commissure of the fornix)
located between the fornices
and inferior to the splenium of
the corpus callosum.

26. Internal capsule consists of the
white matter located between
the basal nuclei and the
thalamus. has five parts:
• (1) Anterior limb located between the caudate nucleus
and putamen. contains a mixture of ascending and
descending fibers.
• (2) Genu located between the anterior and posterior
limbs. contains the corticobulbar fibers.
• (3) Posterior limb located between the thalamus and
lentiform nucleus (comprising the putamen and the
globus pallidus). made up primarily of corticospinal
fibers.
• (4) Retrolenticular portion located posterior to the
lentiform nucleus. contains the optic radiations.
• (5) Sublenticular portion located inferior to the lentiform
nucleus. contains auditory radiations

27. Surface Anatomy of the Cerebral Hemispheres in
Detail- the lateral surface
the frontal lobe bounded posteriorly by
the central sulcus,
The gyrus running in front of the
central sulcus -the precentral gyrus. T
the lateral frontal surface is divided
into the superior, middle, and inferior
frontal gyri by the superior and inferior
frontal sulci.
Similarly, the lateral temporal lobe-
superior, middle, and inferior temporal
gyri by the superior and middle
temporal sulci.
The most anterior portion of the
parietal lobe is the postcentral gyrus
The intraparietal sulcus divides the
superior parietal lobule from the
inferior parietal lobule. The inferior
parietal lobule consists of the
supramarginal gyrus (surrounding the
end of the Sylvian fissure) and the
angular gyrus

28. the corpus callosum is clearly visible,
consisting of the rostrum, genu, body,
and splenium.
The cingulate (“Belt”) gyrus surrounds the
corpus callosum
The central sulcus does not usually
extend onto the medial surface, but the
region surrounding it is called the
paracentral lobule.
The portion of the medial occipital lobe
below the calcarine fissure is called the
lingula (meaning “little tongue”), while the
portion above the calcarine fissure is
called the cuneus (meaning “wedge”).
Just in front -the precuneus.
The Medial Surface

29. The inferior surface
the orbital frontal gyri, the
olfactory sulcus (containing
the olfactory bulb) separates
the orbital frontal gyri from
the gyrus rectus (“straight
gyrus”).
inferior surface of the
temporal lobe, the inferior
temporal sulcus separates
the inferior temporal gyrus
from the occipitotemporal, or
fusiform, gyri.
medially, the collateral
sulcus, continuing anteriorly
as the rhinal sulcus,
separates the fusiform gyri
from the parahippocampal
gyrus

30. Midsagittal MRT t1 weighted
https://mrimaster.com/anatomy%20brain%20sagittal.html

31. https://mrimaster.com/anatomy%20brain%20sagittal.html

32. • The cortex contains billions of neurons arranged in six layers. In 1909 a
German neurologist, Korbinian Brodmann, mapped the cerebral cortex into
47 structural areas based on subtle variations in the thickness of the six
layers. With Brodmann’s structural map emerging, early neurologists were
eager to localize functional regions of the cerebral cortex.
• Neurologists have established that structurally separate areas of the cerebral
cortex perform distinct motor and sensory functions. However, some higher
mental functions, such as memory and language, are spread over very large
cortical areas.
• sensory areas, which allow conscious awareness of sensation; association
areas, which integrate diverseinformation to enable purposeful action; and
motor areas, which control voluntary motor functions
sensations, to communicate,
remember, understand, and
initiate voluntary movements.
• The cerebral cortex is composed of gray matter: neuron cell bodies, dendrites, associated glia and blood vessels, but no fiber tracts. It contains billions of neurons
arranged in six layers. Although only 2–4 mm (about 1/8 inch) thick, it accounts for roughly 40% of total brain mass. Its many convolutions effectively triple its
surface area.
• The cerebral cortex contains three kinds of functional areas: motor areas, sensory areas, and association areas.

33. Functional areas of the
brain
• Primary motor cortex
• Motor cortex
• Primary somatosensory cortex
• Gustatory cortex
• Primary Auditory cortex
• Auditory association area
• Primary visual cortex
• Visual association area
• Brocas’s area
• Wernike’s area
• Prefrontal cortex
• Frontal eye field (movement of eye)

34. Motor Areas
The following motor areas of the cortex, which control voluntary movement, lie in
the posterior part of the frontal lobes:
• primary motor cortex
• premotor cortex
• Broca’s area
• frontal eye field
all lie in the posterior part of the frontal lobe.

36. • 1)the body is “mapped” - each region of
the cortex receives sensory stimuli from
a specific area of the body. This
mapping reflects a general principle
called somatotopy(“body mapping.”) - a
sensory and motor homunculus (; “little
man”), can be constructed for the
postcentral gyrus
• 2) the contralateral projection

37. Sensory Areas
• Areas concerned with conscious awareness of sensation, the sensory
areas of the cortex, occur in
• the parietal, insular, temporal, and occipital lobes

38. Visual areas
The primary visual cortex is on the posterior and medial part
of the occipital lobe. buried within the deep calcarine sulcus
(“spur-shaped”)The largest of all cortical sensory areas, the
primary visual cortex receives visual information that
originates on the retina of the eye. If this cortical area is
damaged, the person has no conscious awareness of what is
being viewed and is functionally blind.
• Visual information proceeds anteriorly through these visual
areas in two streams:
• The ventral stream extends through the inferior part of the
entire temporal lobe and is responsible for recognizing
objects, words during reading, and faces (facial recognition
involves
• the right hemisphere only). It is referred to as the “what”
pathway because it identifies what things are.
• The dorsal stream extends through the posterior parietal
cortex, a multimodal association area, to the postcentral
gyrus and perceives spatial relationships among various
objects. This is referred to as the “where” pathway,
identifying the spatial location of objects.

39. • Wernicke’s area
• A functional brain region involved in recognizing and understanding
spoken words. Damage to Wernicke’s area interferes with the ability
to comprehend speech.
Speech Broca’s area:
Located in the inferior frontal gyrus.
In the majority of individuals it is
importanat on the left or dominant
hemisphere. Ablation will result in paralysis
of speech.
Ablation of the nondominant hemisphere
has no effect on speech.
The broca speech area brings about the
formation of words by its connection
adjucent primary motor areas; muscles of
the larynx, mouth, tongue, soft palate and
respiratory muscles

40. Vestibular (equilibrium) cortex.
Researchers have had difficulty locating the part of the
cortex responsible for conscious awareness of the sense of
balance; that is, of the position of the head in space. Both
electrical stimulation and neuroimaging studies now place
this region in the posterior part of the insula, deep to the
lateral sulcus.
Gustatory cortex. The gustatory (gus tah-to re) cortex
• is involved in the conscious awareness of taste stimuli. It
• lies on the roof of the lateral sulcus.
Olfactory cortex. The primary olfactory cortex lies on
• the medial aspect of the cerebrum in a small region called
• the piriform lobe (pir ı˘-form; “pear-shaped”), which is
• dominated by the hooklike uncus

41. Multimodal
association cortex
• The multimodal association areas can be broadly divided into three parts:
• the anterior association
• posterior association
• limbic association areas.

42. The anterior association
area in the frontal lobe,
also called the prefrontal
cortex
• involved with intellect, complex
learning abilities (called cognition),
recall, and personality. It contains
working memory, which is necessary
for abstract ideas, judgment,
reasoning, persistence, and planning.
These abilities develop slowly in
children, which implies that the
prefrontal cortex matures slowly and
depends heavily on feedback from our
social environment.

43. Posterior Association Area The posterior association area is a large region encompassing parts of the
temporal, parietal, and occipital lobes. This area plays a role in recognizing patterns and faces, localizing us
and our surroundings in space, and binding different sensory inputs into a coherent whole.
Limbic Association Area The limbic association area includes the cingulate gyrus, parahippocampal gyrus,
and hippocampus
Part of the limbic system -the limbic association area provides the emotional impact that makes a scene
important to us
• AGNOSIA Damage to a sensory association area causes agnosia, the inability to comprehend sensory
stimuli from the sense receptors of the PNS. Thus an individual with damage to the visual association
area could have excellent vision but have no understanding of what she is seeing. If the auditory
association cortex is damaged, one could hear sounds but not distinguish a siren from a trumpet.
Damage to the somatosensory association area would disable you from identifying the item in your
pocket as keys by touch alone; you would have to take them out and look at them to determine what
they are.

44. memory:
Declarative (fact) memory
(names, faces, words, and
dates),
procedural (skills) memory
(piano playing),
motor memory (riding a
bike),
emotional memory
Declarative memory storage
involves two distinct stages:
short-term memory and
long-term memory
Short-term memory (STM),
also called working memory,
is the preliminary step, as
well as the power that lets
you look up a telephone
number, dial it, and then
never think of it again. STM
is limited to seven or eight
chunks of information, such
as the digits of a telephone
number or the sequence of
words in an elaborate
sentence. In contrast, long-
term memory (LTM) seems
to have a limitless capacity.
Although our STM cannot
recall numbers much longer
than a telephone number,
we can remember scores of
telephone numbers by
committing them to LTM.
However, long-term
memories can be forgotten,
and so our memory bank
continually changes with
time. Furthermore, our
ability to store and retrieve
information declines with
aging.

45. • The hippocampus
• belongs to the limbic system and plays important roles in the
consolidation of information from short-term memory to long-term
memory, and in spatial memory that enables navigation.
• The hippocampus is located under the cerebral cortex.
• Alzheimer's disease (and other forms of dementia), the
hippocampus is one of the first regions of the brain to suffer
damage; short-term memory loss and disorientation are included
among the early symptoms.

46. • In most people (90% to 95%),
the left cerebral hemisphere has
greater control over language
abilities, math, and logic,
whereas the right hemisphere is
more involved with visual-
spatial skills, reading facial
expressions, intuition, emotion,
and artistic and musical skills
• Whereas the right hemisphere
deals with the big picture, the
left deals with the details, which
it then interprets logically

47. BRS Neuroanatomy 6th edition, Chapter 1
1-9 pp , A. Telencephalon
dokumen.pub_brs-neuroanatomy-6th-edition-9781496396303.pdf
https://radiopaedia.org/cases/neuroanatomy-lateral-cortex-diagrams?lang=gb
https://mrimaster.com/anatomy%20brain%20sagittal.html

48. Part 2- Diencephalon,Brainstemm

49. • diencephalon, the brainstem (midbrain,
pons, and medulla), and the cerebellum.

50. Diencephalon
Slide
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
∙ Sits on top of the brain stem
∙ Enclosed by the cerebral
heispheres
∙ Made of three parts
∙ Thalamus
∙ Subthalamus
∙ Hypothalamus
∙ Epithalamus

52. •Thalamus( Greek “inner room,”) –
• large ovoid mass of gray matter that forms the major part of
the diencephalon.
• is situated on each side of the third ventricle.
• It is a region of great functional importance and serves as a
cell station to all the main sensory systems (except the
olfactory pathway).
• The activities e closely related to that of the cerebral cortex
and damage to the thalamus causes great loss of cerebral
function.
• Right and left portion of thalamus are joined by interthalamic
adhesion

54. Hypothalamus
is that part of the diencephalon that extends from the region of the optic
chiasma to the caudal border of the mammillary bodies.
It lies below the hypothalamic sulcus on the lateral wall of the third
ventricle.
Anatomically the hypothalamus is a relatively small area of the brain
that is placed close to the
• limbic system,
• thalamus,
• ascending and descending tracts,
• hypophysis.
Microscopically, the hypothalamus is composed of small nerve cells that
are arranged in groups or nuclei.
When observed from below, the hypothalamus is seen to
be related to the following structures, from anterior to posterior:
• optic chiasma,
• tuber cinereum and the infundibulum
• mammillary bodies

55. • Functionally, the hypothalamus is the main
visceral control center of the body, regulating
many activities of the visceral organs
• Control of the autonomic nervous system.
• Control of emotional responses.
• Regulation of body temperature.
Hypothalamic centers also induce fever.
• Regulation of hunger and thirst sensations
• Control of motivational behavior.
• Regulation of sleep-wake cycles.
• Regulation of sleep-wake cycles.
• regulate the complex phenomenon of sleep
• The suprachiasmatic nucleus is the body’s
biological clock. It regulates the timing of daily
(circadian) rhythms in response to daylight-dark
cycles sensed via the optic nerve. In response to
such signals, the preoptic nucleus induces sleep
• Control of the endocrine system. The
hypothalamus controls the secretion of hormones
by the pituitary gland,which in turn regulates many
functions of the visceral organs
• Formation of memory. The brain nucleus in
the mammillary body receives many inputs from
the major memory-processing structure of the
cerebrum, the hippocampal formation
• Thus, injuries to the hypothalamus can result in
severe weight loss or obesity, sleep disturbances,
dehydration, and a broad range of emotional
disorders.

56. Connections of Hypothalamus
• Connects with limbic system
• Connects with brainstem and spinal cord
• Connects with dorsal thalamus
• Connects with hypophysis

57. Pineal body – contains brain send
(accumulates with age)
Function: Inhibition of endocrine glands,
produce melatonin and regulate circadian
rhythm,Regulate reproductive function.
Melatonin
signals the body to prepare for the nighttime
stage of the sleep-wake cycle.

58. Midbrain (Mesencephalon )
measures about 2cm in length and connects pons and cerebellum with the forebrain.
Cerebral aqueduct (Sylvian Aqueduct) – connects 3rd and 4th ventricle
• the physiological reactions associated with fear.
• Specifically, the periaqueductal gray matter
• 1) elicits a terror-induced increase in heart rate and skyrocketing
blood pressure, wild fleeing or defensive freezing, and the
suppression of pain when the person is injured.
• 2) seems to mediate the response to visceral pain (for instance,
nausea), during which it decreases heart rate and blood pressure,
produces a cold sweat, and discourages movement.
• The largest of brain nuclei form the corpora Quadrigemina
• the superior and inferior colliculi.
• The two superior colliculi ( “little hills”) are brain nuclei act in
visual reflexes, ( when the eyes track and follow moving objects
even if the person is not consciously looking at the objects.)
• The two inferior colliculi, belong to the auditory system.

61. • embedded in the white
matter of the midbrain are
two pigmented brain nuclei:
substantia nigra (nigra black)
and the red nucleus The oval
red nucleus lies deep to the
substantia nigra.
• (Its reddish hue is due to a
rich blood supply and to the
presence of iron pigment in
the cell bodies of its neurons)
It has a minor motor function:
helping to bring about flexion

63. Brainstem
1. It acts as a passageway for all the fiber
tracts running between the cerebrum and
the spinal cord;
2. It is heavily involved with the innervation
of the face and head, as 10 of the 12 pairs
of cranial nerves attach to it;
3. It produces the rigidly programmed,
automatic behaviors necessary for
survival.
The brain stem has the same structural plan as
the spinal cord, with outer white matter
surrounding an inner region of gray matter.
There are also brain nuclei of gray matter
located in the white matter of the brain stem.

64. • Cranial nerves

65. the pons
the pons (“bridge”) form
Several cranial nerves attach
to the pons, pontine nuclei,
middle cerebellar peduncles,
cerebral aqueduct, which
divides the midbrain into a
tectum (“roof”) dorsally and
paired cerebral
peduncles ventrally.
5th, 6th, 7th nerve
emerges

67. Brain stem,
Medula
(externally visible landmarks)
Pyramids- Flanking the ventral midline,
two longitudinal ridges formed by the
pyramidal Tracts
pyramidal fibers cross over to the opposite
side of the brain at a point -the
decussation of the pyramids (crossover
is that each cerebral hemisphere controls
the voluntary movements of the opposite
side of the body)
the inferior cerebellar peduncles and
the olives
The inferior cerebellar peduncles are
fiber tracts that connect the medulla to
the cerebellum dorsally

69. III and IV from the midbrain;
V and VI from the pons;
VII and VIII from the junction of
the pons and medulla;
IX, X, and XII from the medulla.
Specific nerve deficits
can indicate the region
of injury or
lesion.

70. Reticular Formation (the term "reticular," meaning net-like or mesh-like in
appearance)
⮚ The reticular formation is a central core of nuclei that run through the
entire length of the brainstem.
⮚ It is continuous rostrally with certain diencephalic nuclei and caudally with
the intermediate zone of the spinal cord.
⮚ The rostral reticular formation of the mesencephalon and upper
pons function together with diencephalic nuclei to maintain an alert
conscious state in the forebrain.
⮚ the caudal reticular formation of the pons and medulla works
together with the cranial nerve
nuclei and the spinal cord to carry out a variety of important motor, reflex,
and autonomic functions.
The most important nuclei in the medulla’s reticular formation involved
with visceral activities are these four:
1. The cardiac center adjusts the force and rate of the heartbeat.
2. The vasomotor center regulates blood pressure by stimulating or
inhibiting the contraction of smooth muscle in the walls of blood
vessels
3. The medullary respiratory center controls the basic rhythm and rate of
breathing.
4. Additional centers regulate hiccuping, swallowing, coughing, and
sneezing.

71. Reticular formation is present in all level !!!

72. .
CEREBELLUM -control of posture and voluntary movements.
situated in the posterior cranial fossa and is covered superiorly by the tentorium cerebelli.
It is the largest part of the hindbrain and lies posterior to the fourth ventricle, the pons, and the
medulla oblongata.
The cerebellum is connected to the posterior aspect of the brainstem by three symmetrical
bundles of nerve fibers called the superior, middle, and inferior cerebellar peduncles.
To coordinate body movements, the cerebellar cortex
continuously receives three types of information about how
the body is moving:
✔Information on equilibrium relayed from receptors in the inner ear through the vestibular
nuclei in the medulla oblongata.
✔Information on the current movements of the limbs, neck, and trunk, which travels from
the proprioceptors in muscles, tendons, and joints up the spinal cord to the vermis and medial
portions of the anterior and posterior lobes.
✔Information from the cerebral cortex, which passes from the cerebral cortex through the
pontine nuclei in the pons to the lateral portion of the anterior and posterior lobes.

73. The cerebellum consists of two expanded cerebellar
hemispheres
connected medially by the wormlike vermis
The surface of the cerebellum is folded into many
platelike ridges called folia (“leaves”), which are
separated
by deep grooves called fissures.
Each cerebellar hemisphere is subdivided into three
lobes: the large anterior and posterior lobes, and the
small flocculonodular.
The cerebellum has three regions: an outer cortex of gray
matter, internal white matter called the arbor vitae (“tree of
life”), and deeply situated gray matter called
deep cerebellar nuclei

74. • As noted in preceding sections, the superior, middle,
and inferior cerebellar peduncles are thick tracts of
nerve fibers that connect the cerebellum to the
brain stem .These fiber tracts carry the information
that travels from and to the cerebellum.
• All fibers that enter and leave the cerebellum are
• ipsilateral (ipsi same), which means that
• they run to and from the same side of the body.

75. Cerebellum
Functional areas
vermis - influences the movements of the
long axis of the body, namely, the neck, the
shoulders, the thorax, the abdomen, and the
hips;
intermediate zone - This area has been
shown to control the muscles of the distal
parts of the limbs, especially the hands and
feet;
The lateral zone - each cerebellar
hemisphere appears to be concerned with
the planning of sequential movements of
the entire body;
Flocculonodular lobe - adjust posture to
maintain equilibrium and coordinate head
and eye movements.

76. White matter
• Arbor vitae
• folia
• The intrinsic fibers do not leave the cerebellum but
connect different regions of the organ. Some interconnect
folia of the cerebellar cortex and vermis on the same side;
others connect the two cerebellar hemispheres together.
• The afferent fibers form the greater part of the white
matter and proceed to the cerebellar cortex. They enter
the cerebellum mainly through the inferior and middle
cerebellar peduncles.
• The efferent fibers constitute the output of the cerebellum
and commence as the axons of the Purkinje cells of the
cerebellar cortex. The great majority of the Purkinje cell
axons pass to and synapse with the neurons of the
cerebellar nuclei (fastigial, globose, emboliform, and
dentate).