Brainstem: Midbrain, Pons, Medulla Oblongata & Reticular Formation Flashcards
What does the CNS and PNS consist of?
- CNS - brain and spinal cord
- PNS - peripheral nerves and ganglion
What is the gross divison of the brain
- cerebrum - cerbral hemisphere
- diencephalon
- cerebellum
- brainstem
What is the function of the brainstem?
they help to regulate breathing, heart rate, blood pressure, and several other important functions
- Produce automatic behaviors necessary for survival.
Embryonic development of the brain
- At the front end, the ventricles and cord swell to form three vesicles that are the precursors of the prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain)
- At the next stage, the forebrain splits into two vesicles called the telencephalon (which will contain the cerebral cortex, basal ganglia, and related structures) and the diencephalon (which will contain the thalamus and hypothalamus)
- At about the same time, the hindbrain splits into the metencephalon (which will contain the cerebellum and pons) and the myelencephalon (which will contain the medulla oblongata)
What does Proscencephalon develop into?
What does Mesencephalon develop into?
What does Rhombencephalon develop into?
Describe the neural tube and how it develops
- (in an embryo) a hollow structure from which the brain and spinal cord form
- Defects in its development can result in congenital abnormalities such as spina bifida.
brainstem & its location
- between the cerebrum and spinal cord
- The brainstem is a stalk-like projection extending caudally from the base of the cerebrum. It facilitates communication between the cerebrum, cerebellum, and spinal cord.
3 parts of the brainstem
consists of midbrain, pons and medulla oblongata
- Microscopically, it consists of deep gray matter surrounded by white matter fiber tracts.
What does the brainstem provide?
- provides a pathway for tracts running between higher and lower neural centers
Describe the Basilar portion of the brainstem
- It has importance in the conveyance of motor and sensory pathways from the rest of the brain to the body, and from the body back to the brain
Descending fibers from cerebral cortex:
- corticospinal and corticobulbar tracts - pyramidal tracts
- Corticopontocerebellar Fiber: Cortipontine, Pontocerebellar Fibers and Pons Proper (Ventral Pons)
Describe the roof plate of brainstem
- formed by two paired rounded swellings, the superior and inferior colliculi.
Contains
- Midbrain
- superior colliculus: vision
- inferior colliculus: hearing
Closed medulla
- nucleus gracilis et cuneatus: discriminiative touch sensation
Describe the structure of the tegmentum section of the brainstem
- ventral part of the midbrain
- located between the ventricular system and distinctive basal or ventral structures at each level
- forms the floor of the midbrain (mesencephalon)
Describe the function of the tegmentum
- a multisynaptic network of neurons that is involved in many subconscious homeostatic and reflexive pathways
- It is a motor center that relays inhibitory signals to the thalamus and basal nuclei preventing unwanted body movement
contains:
- Cranial nerve nuclei
- precerebellar nuclei
- reticular formation
- Ascending cortical pathway
- cerebellar circuits, descending, composite bundle tracts
Cranial Nerves Column of Brain Stem
Motor column
GSE - general somatic efferent?
SVE - special visceral efferent
GVE - general visceral efferent
Sensory Column
VA - Visceral afferent - general and special
GSA - General somatic afferent
SSA -Special somatic afferent
- A cranial nerve nucleus is a collection of neurons (gray matter) in the brain stem that is associated with one or more cranial nerves
- In general, motor nuclei are closer to the front (ventral), and sensory nuclei and neurons are closer to the back (dorsal)
- This arrangement mirrors the arrangement of tracts in the spinal cord.
Close to the midline are the motor efferent nuclei, such as the oculomotor nucleus, which control skeletal muscle. Just lateral to this are the autonomic (or visceral) efferent nuclei.
There is a separation, called the sulcus limitans, and lateral to this are the sensory nuclei. Near the sulcus limitans are the visceral afferent nuclei, namely the solitary tract nucleus.
More lateral, but also less posterior, are the general somatic afferent nuclei. This is the trigeminal nucleus. Back at the dorsal surface of the brainstem, and more lateral are the special somatic afferents, this handles sensation such as balance.
Another area, not on the dorsum of the brainstem, is where the special visceral efferents nuclei reside. These formed from the pharyngeal arches, in the embryo. This area is a bit below the autonomic motor nuclei, and includes the nucleus ambiguus, facial nerve nucleus, as well as the motor part of the trigeminal nerve nucleus.
Cranial Nuclei
- A cranial nerve nucleus is a collection of neurons (gray matter) in the brain stem that is associated with one or more cranial nerves
- In general, motor nuclei are closer to the front (ventral), and sensory nuclei and neurons are closer to the back (dorsal)
- This arrangement mirrors the arrangement of tracts in the spinal cord.
Close to the midline are the motor efferent nuclei, such as the oculomotor nucleus, which control skeletal muscle
- Just lateral to this are the autonomic (or visceral) efferent nuclei.
There is a separation, called the sulcus limitans, and lateral to this are the sensory nuclei
Components of the cranial nerves