2.11 Brainstem Networks Flashcards
Describe the brainstem
The brainstem connects the cerebrum to the spinal cord, it is made up of the midbrain then the pons then the medulla. It gives a pathway for tracts running between higher and lower neural centres. It is deep grey matter surrounded by white matter fibre tracts and it is responsible for a lot of the automatic behaviours.
What are the functions of the midbrain
vision, hearing and motor control
What is the function of the pons
pneumotaxic centre (regulating respiration and vascular tone)
What are the functions of the medulla oblongata
cardiac, respiratory, vasomotor and vomiting
Describe the structure of the midbrain
The midbrain is located between the diencephalon and the pons. It has 2 cerebral peduncles on it’s ventral side and these peduncles have descending fibres that go to the cerebellum via the pons as well as descending pyramidal tracts. There is a hollow cerebral aqueduct running through the midbrain which connects the 3rd and 4th ventricles of the brain. The roof of this aqueduct (tectum) contains the corpora quadrigemina which has 2 superior colliculi that controls the reflex movements of the eyes head and neck in response to visual stimuli and 2 inferior colliculi controlling reflex movements of head neck and trunk in response to auditory stimuli.
What are 2 structures on each side of the midbrain
on each side of the midbrain theres a red nucleus and substantia nigra
red nucleus- has many blood vessels and receives info from cerebrum and cerebellum and issues subconscious motor commands concerned with muscle tone and posture
substantia nigra- is lateral to the red nucleus, is a dopamine high area that secretes dopamine to inhibit the excitatory neurons of the basal nuclei
What are the 2 dopaminergic pathways projecting from the midbrain
nigrostriatal pathway - projects from the substantia nigra to the corpus striatum of the basal nuclei (affecting motor coordination)
mesolimbic pathway - projecting from the VTA to the nucleus accumbens (affecting behavioural reward)
Describe the pons
The pons is the bridge between the midbrain and the medulla. It contains lots of nuclei and tracts that process and relay information to and from the cerebellum. These include respiratory nuclei such as apneustic and pneumotaxic centres that work with the medulla to maintain respiratory rhythm as well as the sensory and motor nuclei for cranial nerves 5-8. It has ascending, descending, and transverse tracts that interconnect other portions of the CNS.
Describe the structure of the medulla oblongata
The medulla oblongata is the most inferior brainstem region, it becomes the spinal cord at the level of the foramen magnum (open of the base of the skull). Ventrally, the 2 medullary ridges (formed by the large motor corticospinal tracts) are visible, most of these fibres cross over (aka decussate) right above the medulla/spinal cord junction.
Describe the nuclei within the medulla
Nuclei within the medulla are associated with autonomic control, cranial nerves, and motor/sensory relay.
Autonomic nuclei include;
Cardiovascular centers- alter the rate and force of cardiac contractionsand alter the tone of vascular smooth muscle
Respiratory rhythmicity centers- receive input from the pons
Additional Centers- emesis, deglutition, coughing, hiccupping, and sneezing
The medulla also has the sensory and motor nuclei of cranial nerves 8-12
The medulla also has relay nuclei such as;
-nucleus gracilis and nucleus cuneatus pass somatic sensory information to the thalamus
-Olivary nuclei relay info from the spinal cord, cerebral cortex, and the brainstem to the cerebellar cortex.
Describe reticular formation in the brainstem
An extensive network of neurons going through the medulla and projecting to the thalamic nuclei that influence large areas of the cerebral cortex. They function as a filter for sensory input, allowing important stimuli through and filtering out repetitive stimuli
