C12 9-12 Flashcards
What is the cerebral white matter made of?
Tracts that connect areas of the cerebral cortex to each other or to other parts of the CNS.
Where is Cerebral/central white matter found?
White matter of the brain between the cortex and nuclei (cerebral medulla)
What type of fibers are found in the cerebral white matter?
commisure, association fiber, projection fiber.
Commissure
Connect corresponding grey areas of the two hemispheres and allow the two hemispheres to function as a coordinated whole.
What is the largest commisure?
Corpus callosum - lies superior to the lateral ventricles deep within the longitudinal fissure (less prominent are the anterior and posterior commissures)
Association fiber
Connect areas of the cortex within the same hemisphere. Short associatioin fibers connect adjacent gyri, long fibers connect different cortical lobes.
Projection fiber
Connect the cerebrum to other parts of the brain and spinal cord.
The projection fibers form the internal capsule.
Where are the basal nuclei found?
Deep within the cerebral white matter
Three nuclei: globus pallidus, putamen, caudate.
What are the major functions of the basal (cerebral) nuclei?
- inhibit muscle tone
- inhibit unwanted muscle movement
- start/stop movement.
Also: help initiate and terminate some cognitive processes - attention, memory, planning.
Input/output of basal nuclei
input - from the cerebral cortex
output - to motor areas of the cortex via the thalamus.
What structures are closely associated with the basal nuclei?
Substantia nigra (plays a role in controlling basal nuclei) of the midbrain and subthalmic nuclei of the diencephalon.
What are some disorders associated with the Basal Nuclei?
Parkinson’s disease, obsessive-compulsive, schizophrenia, chronic anxiety.
-dysfunctions of circuits between the basal nuclei and limbic system.
Location of the diencephalon?
Central core of the forebrain, surrounded by the cerebral hemispheres
Divisions of the diencephalon?
Thalamus, hypothalmus, epithalmus
In which ways does the Thalamus relay information?
- most sensory impulses (not olfaction)
* *spinal cord and brain stem —> primary sensory areas of the cerebral cortex** - motor functions
* *cerebellum and basal nuclei —> primary motor cortex** - between different areas of cerebrum (maintenance of consciousness.)
Why is the thalamus an “executive secretary?”
It acts as an information filter, screening out most sensory info that arrives at the thalamus and fwding only a small portion to the cerebrum.
(i.e., filters out sounds and sights when you are studying)
What portion of the diencephalon does the thalamus occupy?
80%
What is the function of the hypothalmus?
- Regulates ANS activity (SWEET HAT)
- Serves as a relay station for reflexes related to smell and with the limbic system emotional and behavioural patterns.
Hypothalmus - SWEET HAT
Sleep Wake (circadian)
Emotional brain Hq (limbic system)
Endocrine Hq
Thirst
Hunger - Autonomic Hq - Thermostat
Epithalamus function
- Includes the pineal gland which secretes melatonin and helps regulate day/night/circadian rhythms.
- Includes the habenular nuclei which help relay signals from the limbic system to the midbrain and are involved in visceral and emotional responses to odors.
Three major regions of the brainstem? (the mesencephalon)
Midbrain, Pons, Medulla oblongata
What does the midbrain include?
cerebral peduncles
, substantia nigra,
Tegumentum,
tectum
What does the pons include?
Conduction pathways, Pontine sleep center, Pontine respiratory center
What does the Medulla Oblongata include?
Pyramids, cranial nerve nuclei, part of reticular formation,
cardiac center, vasomotor center, medullary respiratory center,
nuclei that are involved in coughing, sneezing, salivation, swallowing, gagging, vomiting.
What are cerebral peduncles (midbrain)?
Motor tracts (midbrain)
What are substantia nigra (midbrain)?
neurons that produce dopamine.
Dopamine affects brain processes to control muscle movement, emotional response and ability to experieince pleasure/pain.
Nigra = black color which is because it contains lots of melatonin (precursor to dopamine).
Degeneration of sn = parkinson’s.
Which structure is responsible for the startle reflex?
Inferior colliculi in the tectum of the midbrain
What is tegumentum (midbrain)?
Houses red nuclei and part of the reticular function.
Integrates info from the cerebrum and cerebellum and issues involuntary motor command to the erector spinae muscles of the back to help maintain posture.
What is the tectum?
Consists of four nuclei that form mounds on the dorsal surface called corpora quadrigemina. Each mound is called a colliculus.
Two superior mounds are called superior colliculi (involved in reflex movements of the head, eyes, and body toward visual, auditory or tactile stimuli.
Two inferior mounds are inferior colliculi (involved in hearing and are important part of the auditory pathways in the CNS. STARTLE REFLEX!)
Pontine sleep center
Initiates rapid eye movement in sleep
Pontine respiratory center
Works with the respiratory centers in the medulla to help control respiratory movements.
Beyond the sleep and respiratory center, what are the other functions of the Pons?
Bridge between brain and spinal cord
(Contains fiber tracts that complete conduction pathways between the brain and spinal cord.)
Pontine nuclei relay information from the cerebrum to the cerebellum. House nuclei for cranial nerves V, VI, VII, VIII and IX.
What are the pyramids of the medulla oblongata?
They house motor projection tracts (corticospinal/pyramidal tracts), most of which cross to the opposite side (why the cerebral hemispheres control the opposite side of the body)
What is the function of the cardiac center and where is it located?
Regulates heart rate and force of contraction
medulla oblongata
What is the function of the vasomotor center and where is it located?
Controls blood pressure (changes diameter of blood vessels)
medulla oblongata
What is the function of the medullary respiratory center?
Regulates respiratory rate
What makes up the corpora quadrigemina, and where are they located?
Located in the tectum, midbrain.
Superior colliculi - reflex movements of the head, eyes, and body toward visual, auditory or tactile stimuli
Inferior colliculi - hearing, integral part of the auditory pathways of cns
What are the nuclei in the medulla oblongata responsible for?
Coughing, sneezing, salivation, swallowing, gagging, vomiting
Hypothalmic disturbances would cause?
Severe body wasting, obesity, sleep disturbances, dehydration, emotional imbalances, failure to thrive.
