Lecture 7 - Functional Neuroanatomy Flashcards
What are the 3 axes to describe anatomy?
- Ventral/dorsal
- Anterior/Posterior (or Rostral/Caudal)
- Lateral/Medial
What is the rostral side of the brain?
Front of head
What is the caudal side of the brain?
Back of head
Describe the directional terms in bipeds.
The directional terms are relative to the midline which bends 60 degrees at the forebrain
What is the dorsal part of the brain? Other name?
Toward sky = superior
What are the 3 major planes used in cutting/imaging of the brain?
- Coronal (rostral/caudal)
- Horizontal (dorsal/ventral)
- Sagittal (medial/lateral)
What is the ventral part of the brain? Other name?
Toward floor = inferior
What are the 2 primary functions of the NS?
- Bring sensory input to the body through afferent neurons for integration
- Controlling motor output by activating effector organs through efferent neurons
What are the 4 types of effector organs that the NS activates?
- Skeletal muscles
- Smooth muscles
- Cardiac muscles
- Glands
What are the 3 main components of the PNS?
- 31 pairs of spinal nerves
- 12 pairs of cranial nerves*
- Ganglia
*one of them, the optic tract, is actually part of the CNS
Describe the afferent pathway of the NS.
Internal/External environment => sensory receptors => sensory ganglia and nerves => cerebral hemispheres, diencephalon, cerebellum, brainstem, and spinal cord
What are the 2 parts of the PNS and what does each include?
- Somatic = skeletal muscles and skin
2. Visceral/Autonomic = smooth muscle, cardiac muscle, glands, hair raising muscles
When does the folding of the ectoderm happen? What is this called? What does it form? What does each become?
First month of gestation = neurulation
Forms:
- Neural tube = CNS
- Neural crest cells = PNS
Describe the closing of the neural tube. Is it complete?
Begins in the middle of the rostral-caudal axis and progresses in both the anterior and posterior directions
Complete in normal development
What 2 structures are formed through the closure of the neural tube? What does each become?
- Anterior neuropore = brain
2. Posterior neuropore = spinal cord
What is anencephaly? What is it due to? Survival rate?
Severe reduction in brain development due to failed closure of anterior neuropore
The babies die a few hours or days after birth
What are some diseases due to an improper closing of the neural tube?
- Anencephaly
2. Spina Bifida
What is spina bifida due to? What are the 3 types in order of increasing severity?
Failed closure of caudal neuropore
3 types:
- Occulta
- Meningocele
- Myelomeningocele (can cause infection)
How can neural tube abnormalities be prevented?
Folic acid
Where is folic acid found?
- Spinach
- Liver
- Yeast
- Eggs
- Beans
- All OTC vitamins
How does brain development start? Describe the different parts and what their fate is.
Differentiation of the anterior/rostral neural tube in the anterior neuropore forming 3 primary vesicles (from rostral to caudal):
- Prosencephalon = forebrain
- Mesencephalon = midbrain
- Rhombencephalon = hindbrain
What is the rhombencephalon connected to?
The spinal cord
What stage follows the 3 primary vesicle stage of brain development? Describe it.
5 secondary vesicle stage (from rostral to caudal):
- Telencephalon (from prosencephalon)
- Diencephalon (from prosencephalon)
- Mesencephalon
- Metencephalon (from rhombencephalon)
- Myelencephalon (from rhombencephalon)
What 2 flexures happen at the 3 vesicle stage of brain development? Where is each located?
- Cephalic flexure between mesencephalon and rhombencephalon
- Cervical flexure between rhombencephalon and spinal cord
What flexure happens at the 5 vesicle stage of brain development?
Pontine flexure between metencephalon and myelecephalon
What do the eyes develop from in brain development?
The optic vesicles of the diencephalon
What controls brain development? What experience proves this?
- The dorsal blastopore lip governs the differentiation of neural tissue by secreting organizing factors
- EXPERIMENT: If we replace the ventral epididermis of an fish embryo with a dorsal blastopore lip from a donor embryo we obtain a fish with 2 neural axis - Inhibitors of Bone Morphogenetic Protein (BMP): noggin, follistatin, and chordin all block the ability of ectodermal cells to acquire an epidermal fate, thus promoting neural character
Fate of the telencephalon?
Cerebrum
2 parts of the cerebrum?
- Cerebral cortex
2. Basal ganglia
Fates of the diencephalon?
- Thalamus
- Hypo
- Pit
- Retina + optic tract
Fates of the mesencephalon?
- Tectum
2. Tegmentum
Fates of the metencephalon?
- Pons
2. Cerebellum
Fate of the myelencephalon?
Medulla
What are the 3 parts of the brainstem? What vesicles of the 5 vesicle stage does each correspond to?
- Midbrain from mesencephalon
- Pons from metencephalon
- Medulla from myelencephalon
What does the tectum form?
Roof of midbrain
What does the tegmentum form?
Floor of midbrain
What are the pons and cerebellum used for?
Motor coordination
What are the 3 main systems of the human NS?
- Sensory systems
- Motor systems
- Associational systems
What is the role of associational systems?
Integration at the cortex level to achieve proper behavioral outcomes in response to sensory inputs
What part of the cerebrum does the cerebral cortex make up?
The outer-most gray matter of the cerebrum
Describe the structure of the cerebral cortex.
Contains convolutions: sulci and gyri and is divided into hemispheres and lobes by fissures (except for the occipital lobe)
What are the 3 major functions of the cerebral cortex?
- Sensory systems
- Motor systems
- Associational systems
What are the 2 components of the autonomic motor division of the PNS?
- Sympathetic
2. Parasympathetic
What part of the cerebrum does the basal ganglia make up?
Deep gray matter
Which is largest: the cerebral cortex or the basal ganglia?
Basal ganglia
What is the function of the basal ganglia?
Initiation/Regulation of voluntary movement
What 2 pathologies are related to the basal ganglia? Describe each.
- Parkinson’s: hypokinesia = decrease in voluntary movement
2. Huntington’s: hyperkinesia = increase in unwanted movement
What is the largest gray matter structure found in the brain?
Basal ganglia
What part of the cerebrum is lateral to the diecenphalon?
Basal ganglia
What is the main function of the thalamus?
Relay center connecting sensory systems to the cerebral cortex
Describe the structure of the thalamus.
2 lobes
What are the 2 functions of the hypo?
- Master controller of autonomic NS
2. Regulates hormone release
What is the function of the midbrain?
Relay info between cerebrum and spinal cord
Where is the midbrain located?
Right below the diencephalon and right above the pons
What is the reticular formation made of?
Part of the midbrain and the medulla
Functions of the tectum of the midbrain?
Auditory and visual processing
What are the 4 structures of the tectum?
4 corpora quadrigemina = the four colliculi—two inferior, two superior
Function of tegmentum?
Reflexes
Function of pons?
Relay center connecting cerebral cortex to cerebellum
Relay stations of the brain?
- Thalamus
2. Pons
What part of the brain touches the spinal cord?
Medulla
What is the function of the reticular formation?
Contains centers that regulate heart rate and breathing
What are the 3 elements of the cerebral ventricular system? Where is each located?
- 2 lateral ventricles in forebrain
- Third ventricle in forebrain
- Fourth ventricle in hindbrain
What connects the 3rd and 4th ventrical?
The cerebral aqueduct
What is the cerebrospinal fluid produced by?
Ependymal cells of the choroid plexus in each brain ventricle and the central canal of the spinal cord
What are the 2 parts of each 2 lateral ventricles?
- Anterior horns
2. Inferior horns
What are the 3 functions of the cerebrospinal fluid?
- Shock absorber
- Delivers nutrients and removes wastes
- Compensates for changes in intracranial pressure by flowing from brain to spinal cord
How much cerebrospinal fluid do ependymal cells make each day?
700 mL
What is the pathway of CSF through the brain?
Ependymal cells of choroid plexus in lateral ventricles => interventricular foramina => 3rd ventricle => cerebral aqueduct => 4th ventricle => central canal OR through apertures (Foramina of Luschka and Magendie) to subarachnoid space => subarachnoid villi => venous fluid compartment = BBB
Where is the subarachnoid space?
All around the brain
What is another name for the interventricular foramina?
Foramina of Monro
What is the purpose of the interventricular foramina?
Connects the 2 lateral ventricles to each other and to the 3rd ventricle
What is hydrocephalus?
Excess CSF causes enlargement of ventricles due to a clog in movement or drainage of CSF
What is the effect of hydrocephalus in adults?
Increased intracranial pressure => cell death
What are 4 underlying causes of hydrocephalus?
- Meningitis
- Tumors
- Inflammation
- Trauma
What is the treatment for hydrocephalus?
Shunt to abdomen to drain the fluid into the peritoneal space
What are the 2 types of hydrocephali?
- Congenital
2. Acquired
What are the meninges?
Protective coating of the CNS
What are the 3 different meninges?
- Dura mater
- Arachnoid mater
- Pia mater
What is meningitis? 2 types? Most severe?
Infection of the meninges:
- Bacterial (severe)
- Viral
Describe the dura mater.
Thick and tough
Describe the arachnoid mater.
Spider-web like
Describe the pia mater. Where is it located?
Thin and slightly associated in all grooves
Where is the dura mater located?
Outermost layer of the brain
Where is the arachnoid mater located?
Surrounds the subarachnoid space
List the 6 layers of the head.
- Skin
- Periosteum
- Bone
- Epidural space (potential space because they are fused together)
- Dura mater
- Arachnoid mater
- Subarachnoid space
- Pia mater
Does the spinal cord have meninges?
YUP, same ones
What do the spinal meninges coat?
Nerves that exit from the spinal cord including their ventral and dorsal roots, dorsal root ganglion, and spinal nerve
Why is a lumbar puncture performed?
To assay the presence of bacterial or viral infection of the CSF
Where is a lumbar puncture performed? Why?
Between spinal nerves L3 and 4 into the subarachnoid space because at this point we are below the conus medullaris/terminalis (caudal most extent of spinal cord proper) and where the cauda equina are (spinal nerves at the base of the spinal cord)
What are 2 side effects of a lumbar puncture? Explain each
- Paresthesia = altered sensation which may indicate damage to cauda equina and is generally temporary
- Hemorrhage = abnormal vasculature causing paralysis
Where is epidural anesthesia done?
Any level of the spinal cord
Why is epidural anesthesia referred to as segmental anesthesia?
Because it reduces sensation of the spinal nerves surrounding the injection
How far does the needle go in the epidural anesthesia?
Epidural space