Anatomy 1 Flashcards
What is decussation?
- Axons crossing the midline
- Important example: The corpus callosum is the major fiber tract connecting the L & R hemispheres of the brain.
Lateral vs. medial
- Lateral = away from midline
- Medial = towards midline
Contralateral
Opposite side of body or brain as another structure
Ipsilateral
Same side of body or brain as another structure
Directional terms with mouse
Rostral
Sounds like nostril!
Towards the nose/front in a quadruped
Dorsal
Towards back (dos in French)
Directional terms & neuraxis
Directional terms ending with -ior vs. -al
- Ends with -ior: Directions are perpendicular or parallel to the ground
- Ends with -al: Directions are relative to the neuraxis
Planes of section
Transverse sections
Starts coronal rostrally –> becomes horizontal caudally
Transverse sections are always ___ to the neuraxis
Perpendicular
Examples of directional terms (separate into flashcards)
White vs. grey matter
- White matter is mostly axons
- Grey matter is mostly cell bodies
Afferent vs. efferent
- Afferent fibers arrive into the central nervous system (ex. sensory axon
carrying information from fingertips into the dorsal root of the spine). - Efferent fibers exit the central nervous system (ex. motor axon exiting the
ventral root of the spine to control fingertips). - We will be using these terms to describes fibers as they arrive in or exit the
central nervous system (brain and spine), but you will encounter these terms
in the future to refer to specific regions (ex. afferent fibers arriving into the
thalamus)
Divisions of the NS - flow chart
What does the central nervous system include?
Brain and spinal chord
What does the peripheral nervous system include?
Everything except the brain and spine, e.g. spine nerves
What are the two divisions of the peripheral NS?
- Somatic (voluntary)
- Visceral/autonomic (involunary)
Somatic nervous system
- Voluntary
- Motor axons control muscle contractions (soma in CNS vs. axons in PNS)
- Sensory nerves entering spine containing info from skin, muscles, and joints
Visceral/autonomic nervous system
- Involuntary
- Innervates internal organs, blood vessels, and glands
- Motor axons control relaxation or contraction of walls of blood vessels and intestines i.e. smooth muscles
- Sensory axons carry info on visceral function (e.g. pressure in blood vessels)
- Divided into sympathetic (fight or flight) and parasympathetic (rest and digest)
Diagram of spinal cord
Components of spinal nerve (look at pink box in diagram)
- Afferent dorsal root (going into spine)
- Efferent ventral root (going out of spine)
- There is one spinal nerve for each level of the spinal cord
- The dorsal root ganglia contain the cell bodies of sensory neurons BUT there are no ventral root ganglia
How many spinal nerves are there for each level of the spinal cord?
1
Dorsal root ganglia
- Contain the cell bodies of sensory neurons
- No ventral root ganglia
Meninges (look at blue box)
- Also cover spinal cord and follow same order as spinal (outermost to innermost): Dura mater, subdural space, arachnoid, subarachnoid space, membrane, pia mater
Cross-section of spinal cord
- Gray matter (middle) can be divided into dorsal horn, intermediate zone, or ventral horn
- White matter (outside) can be divided into dorsal column (pink), lateral column (blue), or ventral column (purple)
Diagram of meninges
What are the three meninges?
- Dura mater
- Arachnoid membrane
- Pia mater
The CNS is protected by the ___, a layer of _ membranes
Menings, 3
Dura mater
Outermost and leather-like layer
Subdural space
Between dura mater and arachnoid membrane
What causes a subdural hematoma?
When blood vessels passing through the dura burst
Arachnoid membrane
Spider web-like meningeal layer
Subarachnoid space
- Between arachnoid and pia mater
- Contains CSF (cerebro-spinal fluid)
- Lies just under arachnoid membrane
Pia mater
- Thin, innermost membrane
- Adheres closely to the surface of the brain
- Many blood vessels run along this membrane
Which is the thinnest layer of the meninges?
Pia mater
Meningitis
Infection of meninges
What are the three layers of the embryo?
- Endoderm
- Mesoderm
- Ectoderm
Endoderm of embryo
- Innermost/ventral layer of cells
- Develops into internal organ lining
Mesoderm of embryo
- Middle layer of cells
- Develops into bones and muscle
Ectoderm of embryo
- Outermost layer of cells
- Develops into nervous system and skin
Neural plate
Portion of the ectoderm that develops into the nervous system
What is the neural tube?
A tube that develops from an inward folding of the neural plate and is the actual precursor to the entire CNS
What is neurulation?
- The process that creates the neural tube
- The actual conformational change of the neural plate into the neural tube
- Occurs early in embryonic development (~22 days)
Steps of neurulation/neural tube development
- The neural plate sinks/folds inward in a U-shape to form a groove (entire green structure in diagram)
- The lateral ends of the neural plate (purple structure) become the walls of the neural groove and are called the neural folds
- The two neural folds come together medially to fuse and form the neural crest, which also leads to the closing of the neural groove into the neural tube
Development of PNS vs. CNS
Medial Neural Plate → Neural Groove → Neural Tube
→ CNS
Lateral Neural Plate → Neural Fold → Neural Crest →
PNS
A failure to close the rostral end of the neural tube can cause ___
Anencephaly, lack of brain (fatal)
Neuropore (neural tube defect)
- Opening/gaps in the neural tube.
- Failure to seal and close neuropores during embryonic development leads to neural tube
defects that leave infants with undeveloped brains and spinal cords at
birth
Anencephaly (neural tube defect)
- Neural tube defect that results from a failure to close the anterior/rostral end of the neural tube
- Results in infants having incomplete brains and skulls
- Incurable and leads to death shortly after birth
Spina bifida
- Neural tube defect that results from a failure to close the posterior/caudal end of the neural tube
- Typically results in a sac of spinal fluid protruding from the mid to lower back that sometimes impairs ability to walk, damages bladder and bowel control, and causes hydrocephalus
- Can be treated through surgery
Anencephaly results from failure to close the ___ end of the neural tube
Anterior/rostral
Spina bifida results from failure to close the ___ end of the neural tube
Posterior/caudal
Neural tube differentiation
Forebrain neural differentiation
Midbrain differentiation
Hindbrain differentiation
Neurogenesis
- BrdU substitutes for thymidine in DNA, so any cells dividing would pair BrdU instead of A-T pair
- Post-mortem, neurons (not just glia or stem cells) showed up BrdU positive
Where do neural stem cells exist?
- Subventricular zone (SVZ): development
- Dentate gyrus of hippocampus in temporal lobe of adults
- Olfactory bulbs
- Adult humans are still capable of growing a few new neurons in these selective neurons
Ventricular system
- The ventricular system is a series of connected fluid-filled chambers and canals called ventricles.
- The fluid filling these chambers is cerebrospinal fluid (CSF).
3rd vs. lateral ventricles
- If the cross-section is more rostral, the 3rd ventricle will be absent or very small
- Paired chambers are good evidence that the ventricles you are looking at are the lateral ventricles (general rule but not always the case)
- If you ever see ventricle in the very lateral areas of the cortex (e.g. in the temporal lobe, bordering the hippocampus or amygdala, this is lateral ventricle due to its ram horn-like shape
LLC - lateral ventricles
LLC = Lateral to the Lateral ventricle is the Caudate
- If the lateral ventricles and 3rd ventricle are both present in the same cross-section, the caudate will be lateral to the lateral ventricles vs. the thalamus will be lateral to the 3rd ventricle
Errors in the development of the neural crest in the developing embryo would most likely lead to ___
Loss of neurons in the dorsal root ganglia
All of the following brain structures develop from the neural tube except:
a) cerebellum
b) medulla
c) dorsal root ganglia
d) red nucleus
c) Dorsal root ganglia (develops from neural crest)
Which of the following structures develops first
a) neural tube
b) neural crest
c) neural plate
d) neural groove
c) neural plate
