Anatomy and Histology

Das Telencephalon oder Endhirn ist jener Teil des Zentralnervensystems, der aus dem vorderen Bereich des Vorderhirns hervorgeht und bei Säugetieren wie dem Menschen zum größten der fünf Hirnabschnitte wird, so auch Großhirn genannt.

• The embryonic telencephalon gives rise to the cerebrum.

• This is the largest part of the brain and comprises the cerebral cortex as well as other

  sub‐cortical structures, such as the hippocampus, the basal ganglia and the olfactory

  bulb.

• The cerebral cortex is usually classified into 4 lobes:

  • Frontal
  • Parietal
  • Temporal

• And occipital

• The surface of the cerebral cortex is folded into ridges (gyri) and furrows (sulci), which serve to increase the surface area. 

Dysphasia: language disorder marked by deficiency in the generation of speech, and sometimes also in its comprehension, due to brain disease or damage. 

The sensory part is in the parietal lobe and the motor part is in the frontal lobe

The cortical homunculus is a neurological map of the anatomical divisions of the brain. The two types of cortical homunculus are the sensory and the motor
Sensory homunculus – representation of the brain mapped in areas. Each area receives the sensory information from a specific body part
Motor homunculus ‐ representation of the brain mapped in areas. Each area processes motor information from a specific body part 

From the diencephalon originate the:

• Thalamus, sensory relay station

• Hypothalamus, regulates voluntary behaviour

• Epithalamus, choroid plexus and pineal gland (melatonin) 

• The Thalamus, is a midline structure, with two symmetrical halves, located between the cerebral cortex and the midbrain.

• It has 2 egg‐shaped bodies, form the walls of the 3rd ventricle

• Can be divided in 5 areas:

1. Anterior – Limbic system, emotions, memory, learning

2. Medial – conscious awareness of emotions

3. Lateral – regulate emotional state and sensory input

4. Ventral – basal nuclei & cerebrum, plan and fine tune movement

5. Posterior – integrate sensory input, LGN (lateral geniculate nucleus) visual, MGN

   (medial geniculate nucleus) auditory 

One of the main functions od this structure is the link between the NS and the endocrine system, via the pituitary gland
Limbic system is midline, encircle the thalamus, shared parts with thalamus, hypothalamus, cerebrum and diencephalon

1. Autonomic nervous system coordination, reactions to pain, anger, sex, pleasure

2. Body temperature

3. Circadian rhythms

4. Drives (thirst, hunger, sex)

5. Hormones (posterior: ADH and oxytocin; anterior: LH, FSH, TSH, GH)

6. Mammillary body, licking swallowing, gaging 

Limbic System

• Called the “emotional brain”

• Essential for flexible, stable and adaptive

functioning
• Necessary for emotional balance, adaptation to  environmental demands (fearful situations), for creating meaningful connections with others (ability to interpret facial expressions and give an adequate response) 

The limbic system is located in the brain midline and it encircles the thalamus. It includes the :

1. Olfactory bulbous

2. Anterior thalamic nucleus

3. Columns of fornix

4. Septum pedelucidum

5. Hebenular commissure

6. Para hippocampal gyrus

7. Limbic cortex

8. And limbic midbrain

Connected to the nucleus accumbens‐> pleasure centre 

Aka midbrain

Parte of the CNS associated with vision, hearing, motor control, sleep/wake, Arousal, And temperature regulation 

Consists of two main parts:

1. tectum, with a visual function

   1. Superior colliculus (aka optic tectum in other vertebrates) receives visual input directly from the retina and responds almost exclusively to visual stimuli

   2. Inferior colliculus receives auditory input from medulla oblongata

2. The cerebral peduncle, which is subdivided in three areas:

   1. Midbrain tegmentum ‐ forms the floor of the midbrain

   2. Cerebral crus – anterior portion of the cerebral peduncle which contains the

      motor tracts. It connects the cerebrum to the spinal cord/brain stem

   3. Substantia nigra – role in reward and movement

3. The tegmentum forms distinguished divisions in the midbrain: Pons and medulla

4. The midbrain tegmentum is part of the midbrain extending from the subtantia nigra

   (lateral to red nucleus, dopaminergic, regulates motor output (Parkinson’s), also involved in reward and addiction). It includes the red nucleus, the reticular formation (regulates cardiovascular system, breathing, sleep‐wake cycle and filters incoming stimuli) and the subtantia nigra 

From the embryonic myelencephalon develops the medulla oblongata. It is the most posterior structure of the brain. It has a reticular formation.

Myelencephalon (medulla), most posterior, reticular formation, involved in:

sleep
attention
movement
maintaining muscle tone
ardiovascular reflexes
respiratory reflexes

Connected by the Pons to the midbrain and posteriorly is continued buy the spinal cord

Pons and Cerebellum

1. Pons contains an extension of the reticular formation, is involved in:
   sleep; respiration; swallowing; bladder control; hearing; equilibrium; taste; eye movement; facial expressions; facial sensation; and posture
   505 MYO ‐> lampreys
   Connects the midbrain to the medulla oblongata
   Contains an extension of the reticular formation

2. Cerebellum is a sensorimotor structure controlling movements, as well as attention and language, barely developed in lamprey, but can be found in cephalopods, fishes, reptiles, birds, mammals 

Is in the metencephalon

In the Pons we can find several cranial nerve nuclei:

1. Mid pons: trigeminal nerve sensory nucleus (V)

2. Lower down in the Pons is the abducen nucleus (VI), the facial nerve nucleus (VII)

   and the vestibulocochlear nuclei (VIII)

These are all basically sensory and motor nuclei involved in hearing and equilibrium 

Die Formatio reticularis oder Retikulärformation bezeichnet ein ausgedehntes, diffuses Neuronennetzwerk im Hirnstamm, das von der Medulla oblongata (verlängertes Mark) bis zum Zwischenhirn (Diencephalon) reicht. Die Formatio reticularis setzt sich nach vorn in das mediale Vorderhirnbündel fort.

The reticular formation is a set of interconnected nuclei that are located throughout the brainstem. The reticular formation is not anatomically well defined because it includes neurons located in diverse parts of the brain. The neurons of the reticular formation all play a crucial role in maintaining behavioral arousal and consciousness. The functions of the reticular formation are modulatory and premotor. The modulatory functions are primarily found in the rostral sector of the reticular formation and the premotor functions are localized in the neurons in more caudal regions

•  Region of the brain that plays a role in motor control

•  It does not initiate movement, but it contributes to coordination, precision, and

  accurate timing.

•  It receives input from sensory systems of the spinal cord and other parts of the brain

  and integrates inputs to fine motor activity.

•  Two cerebellar hemispheres

•  Based on the surface appearance we can identify 3 lobes:

  1. Anterior or superior – responsible for mediating unconscious proprioception (it can be detreated in alcoholics)

  2. Posterior or neo‐cerebellum – plays a role in fine motor coordination, specially in the inhibition of involuntary movement via inhibitory neurotransmitters, especially GABA

  3. Flocculonodular node – composed by the nodule and the flocculens. Plays a role in balance and eye movement

•  Two main types of neurons in the cerebellum:

  1. Purkinje cells, massive pear‐shaped cells. Form the heart of the cerebral

     circuit

  2. Granule cells – amongst the smaller neurons of the brain. Also the most

     numerous ones. Receive all of their input from Mossy fibbers. 

• As I have mentioned, the brain is the central computer of the organism. It is also one of the most fragile organs. For that reason it is highly protected.

•  Immediately after the bone (skull periost) there are 3 membranes that from the blood‐brain barrier and whose function is to separate the circulating blood from the brain’s extracellular fluid.

•  The blood brain barrier allows the passage of water, some gases and lipid soluble molecules by passive diffusion and also the selective transport of some essential molecules, such as glucose.

•  It works as a barrier that prevents the passage of neurotoxins, bacteria and other large or dangerous particles into the cerebrospinal fluid, hence preventing damage to the brain.

•  The 3 membranes found between the skull periost ant the brain are the meninges: 

  •  The dura mater is continuous with the bone in the skull, but in the spinalcord there is a fat and blood vessel filled space between the periost and the dura mater. It is a dense fibro‐elastic layer, internally lined by fat cells.

  • The arachnoids comes next. Between dura and arachnoid mater is the lamina neurothelialis, comprising fibroblasts with tight junctions, i.e. a barrier. There is also the potential for a subdural space to develop. The Arachnoid trabeculae give a cob‐web appearance. The subarachnoid space is filled with CSF and blood vessels
  • Pia matter – covers the nervous tissue. Mostly made by collagen fibbers, fine elastin fibbers and occasional fibroblast, separated by the astrocyte processes of the underlying CNS by a basement membrane. This membrane is continuous with the arachnoid mater (pia‐mater or leptomeninges). The space between the pia and arachnoid is the subarachnoid space, and sometimes forms large cisterns. The subarachnoid space is lined by flattened arachnoid cells. There is a continuous flow of cerebral spinal fluid from the ventricles to the subarachnoid space.

Die Hauptfunktion des Liquors besteht in der Polsterung des Gehirns und des Rückenmarks. Ernährungsfunktion und Beteiligung an Signalkaskaden sind umstritten und ebenfalls Gegenstand aktueller Forschung.

The cerebral‐spinal fluid is a clear, colorless liquid, found in the brain and spine. It is produced in the choroid plexus of the ventricles of the brain.
It acts as a cushion for the brain’s cortex, provides basic mechanical and immunological protection to the brain. Nourishes the CNS. I regulates the cerebral blood flow.
It occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord 

Als Hirnnerven bezeichnet man Nerven, die nicht aus den Spinalnerven hervorgehen, sondern direkt aus spezialisierten Nervenzellansammlungen (Hirnnervenkernen) entspringen. Hirnnerven besitzen immer mindestens eine Durchtrittstelle innerhalb der knöchernen Struktur des Schädels.

is the basal ganglia