CNS includes
Brain and spinal cord
White matter consists of
lots of bundled, myelinated axons in fiber tracts
Job of white matter
communication
Grey matter and White matter location in Brain
outer cortex and inner area
Grey matter and White matter location in Spinal Cord
inner H area and outer area
Grey matter consists of
unmyelinated axon fibers, dendrites, cell bodies, and glial cells - all superficial stuff
Four regions of the brain
cerebrum, cerebellum, brain stem and diencephalon
Four ventricles of the brain
(2) lateral ventricle
(1) Third ventricle
(1) Fourth ventricle
location of lateral ventricle
cerebrum
location of third ventricle
diencephalon
location of fourth ventricle
brain stem
What are Gyri?
elevated ridges in the CNS
What are Sulci?
shallow grooves in the CNS that divide the cerebrum into frontal, parietal, temporal, occipital and insular lobes.
What are fissures?
deep grooves that separate the brain longitudinally (left and right hemispheres) and transverse (separates cerebrum and cerebellum)
What are the names of Cerebral Lobes and how many are there?
(5) Frontal lobe, Parietal lobe, Occipital lobe, Temporal lobe, Gyri of Insula
What is the Cerebral Cortex?
- Consists of the outer gray matter region (everything except the myelinated fibers).
- The outside or superficial portion of the cerebrum.
- Contains neuron cell bodies, dendrites, glial cells, but no fiber tracts
Where is the conscious mind found?
Cerebral Cortex
What are the functions of the Cerebral Cortex?
awareness
sensation
memory
communication
understanding
voluntary movements
What are the functional areas of the Cerebral Cortex?
Sensory, motor, and association
*All made up of interneurons (inside CNS)
How does Hemisphere specialization affect the function of each side of the brain?
- Cerebral dominance designates the hemisphere that's dominant for language, math and logic.
- Less dominant hemisphere involves in visual-spatial, artistic, musical skills, emotion and intuition
- the dominant side of the brain controls the opposite side of the body
What are the three basic regions of each cerebral hemisphere?
(1) a superficial cortex of gray matter (looks gray in fresh brain tissue)
(2) internal white matter (the myelinated axons in fiber tracts running in three different directions)
(3) Basal Nuclei (islands of gray matter situated deep within the white matter)
Where is Cerebral white matter located?
Deep to the cortex layer - internal
What does the cerebral white matter consist of?
consists of axons bundled into tracts
What does the cerebral white matter communicate between?
communicates between cerebral cortex and lower CNS center and different areas within cerebrum.
How are white matter tracts named and what are those names?
named based on the directions they run
Commissures
Association
Projection
Commissures: definition
tracts that communicate between two hemispheres - corpus callosum is largest
Association fibers: definition
tracts that connect different parts of the same hemisphere - draped like curtains
Projection fibers: definition
tracts that connect cerebrum to lower brain or spinal cord - project outward from the diencephalon in rays
Where is the diencephalon located and what does it consist of?
- its a very small area, embedded in the middle of the brain, surrounded by the cerebellum
- consists of the thalamus, epithalamus and the hypothalamus*
- encloses the third ventricle
*most important of the 3
Where is the Thalamus and what does it do?
- biggest part of the diencephalon
- projects & receives fibers from the cerebral cortex - lots of relay work b/c lots of neurons, lots of sensory nerves come out here.
*senses from all parts of body converge and synapse here - gateway to the cerebral cortex
Where is the Epithalamus and what does it do?
- above and to the back to the Thalamus (superior-dorsal portion of diencephalon)
- includes the pineal gland
Where is the pineal gland located and what does it do?
*A part of the endocrine system.
- extends externally from the posterior border of the epithalamus
- secretes Melatonin (a hormone involved with sleep-wake cycles (along with hypothalamus) and mood)
Where is the Hypothalamus and what are its parts?
- front and bottom of the the thalamus
- *most important of the three parts
- consists of three parts - optic chiasma, mammillary bodies, and the infundibulum (connects the pituitary gland to the hypothalamus by a stalk of hypothalamic tissue)
Where is the Optic chiasma located and what does it do?
- located in the hypothalamus
- spot where the optic nerves cross over
Where are the mamillary bodies located and what do they do?
- located in the hypothalamus
- relay station for the olfactory senses
Where is the pituitary gland and what does it do?
located between the optic chiasma and mammillary bodies on the infundibulum (a stalk of hypothalamic tissue.
secretes 8 hormones (ex. Antidiuretic, growth hormones and oxytocin)
part of the endocrine system
What are the functions of the Hypothalamus?
SA TALE
Sleep Cycle - via light darkness cues
Autonomic control center - BP, HR, breathing rate, digestive tract motility, pupil size
Temperature - regulates set point of body temp*
Appetite - food intake and fluid balance
Libido - control of the endocrine system (pituitary glands)
Emotion - biological rhythms, drives, emotions of pleasure, fear and rage.
*the only function that is only controlled by this part of the brain.
What are the parts and function of the Brain stem?
Encloses the fourth ventricle
- midbrain
- pons
- medulla oblongota
Functions:
- controls autonomic functions
- communicates between higher and lower CNS
- associated with 10 pairs of cranial nerves
Function and action of the Midbrain?
- It has a cerebral aqueduct connecting the third (diencephalon) and fourth (brainstem) ventricles
- center for visual and auditory reflexes
- pathway that controls fight-or-flight response
Function and action of the Pons?
- Helps the medulla oblongota maintain normal breathing rhythms
- acts as a relay point between the cerebrum and the cerebellum
Function and action of the Medulla Oblongata?
Relay point between the cerebrum and the spinal cord.
- When you are asleep/unconscious it keeps your heart and lungs working
- in charge of methods of expelling something (vomiting, hiccuping, swallowing, coughing, and sneezing)
What are the functions of the Cerebellum?
- coordinates skeletal muscle movement by providing precise timing and appropriate patterns
- recognizes and predicts sequences of events and can make adjustments
- word association and puzzle solving
*lots of balancing things *makes small adjustments (balance etc) *stores information for quick access (like in typing) - almost like a reflex.
What is the vermis?
a fissure that connects the two hemispheres of the cerebellum
What is a physical difference between cerebellum and cerebrum?
one has transversely oriented gyri ONLY
Where is the Arbor Vitae located?
the white pattern in the cerebellum
What protect the brain?
Skull bones, meninges, CSF, Blood-Brain Barrier
What is the Meninges?
A system of membranes that envelopes the CNS.
What are the layers of the Meninges?
Pia mater, Arachnoid Mater, Dura Mater
Dura Mater
Thick, durable outer layer of the meninges.
Three dural septa fold inward to limit excessive movement of the brain.
Arachnoid Mater
The fine elastic middle layer of the meninges.
- extensions secure it to the layer below and create a space that is filled with CSF.
Subarachnoid space
the space between arachnoid and pia maters; filled with CSF.
Pia Mater
Deep, delicate layer that hugs the brain - flows over the gyri and into the sulci.
Contains LOTS of tiny blood vessels
What is Cerebrospinal Fluid (CSF)?
a water solution found in between the cerebral cortex and the meninges and fills the inside of the brain body.
Similar to plasma but has less protein and different ion concentrations.
What are the functions of Cerebrospinal Fluid (CSF)?
It forms a cushion - provides protection from blows and other trauma.
Gives buoyancy and reduces brain weight
Provides nourishment.
Where is the CSF made and how?
Choroid plexuses in all 4 ventricles.
It is made up of capillaries and ependymal cells.
The capillaries filter plasma fluid whole ependymal cells change ion concentrations.
It then drains out by the arachnoid villi into venous (de-oxygenated) blood.
Arachnoid villi
little pockets in arachnoid mater poke through lower level of dura mater.
Provide a route for CSF to drain into venous (deoxygenated blood)
How much CSF is located in the human body?
150mL, replaced every 8 hours -- formed and drained at the same rate.
How is CSF Circulated?
It is made in individual ventricles but circulates through the brain in a specific pattern, cilia on ependymal cells beats and helps circulate.
Path of CSF Circulation?
secreted by the villi in the ventricle...
-->so it starts from the lateral ventricle
-->reaches the third ventricle via the foramen of monroe
-->then to the fourth ventricle via the aqueduct of sylvius
-->then to the arachnoid granulations via the foramen of lushka and magendie{anyone of them}
-->them from the subarachnoid space into the spinal cord
What is the Blood-Brain Barrier?
(BBB)
Like the group of the same name - it's a protective mechanism that maintains a stable environment for the brain.
How does the BBB function?
Capillaries are very thin veins made of a single layer of squamous epithelial, but the capillaries in the brain have special modifications to keep substances away from neurons.
What special modifications do brain capillaries have?
- a continuous endothelium of capillary walls
- relatively thick connective tissue on capillaries
How is the BBB selective?
It's very picky in a smart way:
it takes all the good stuff (nutrients enter freely - oxygen, glucose, amino acids, electrolytes)and expels wastes (metabolic and CO2) into blood vessels easily.
What is the BBB ineffective against protection against?
alcohol, nicotine and anesthetics
What is the length of the spinal cord in relation to verterbrae?
It runs from C1 to L2
What are the functions of the spinal cord?
- provides two way communication with the brain
- a major reflex center
What protects the spinal cord?
vertebrae, meninges, and Cerebrospinal fluid
Is the spinal cord uniform throughout its length?
No - the Cervical and lumbar regions are enlarged
How many pairs of spinal nerves (part of PNS) are attached to the spinal cord?
31 pairs
What is internal of the spinal cord
Inner gray(really brown) matter shaped like a butterfly - the dorsal edge of the wing (faces the back) is the Dorsal horn, the opposing edge is the ventral horn.
Dorsal horn
- dorsal edge of the butterfly wing.
- contain interneurons (cell bodies)
- sensory neuron axons enter via dorsal root and synapse with the interneurons.
- includes the Dorsal root ganglion
What is the Dorsal root ganglion?
the bulging area of dorsal root - where sensory neuron cell bodies gather
Ventral horns
- ventral side of the butterfly wing
- contains motor neurons
- send their axons via ventral roots to skeletal muscles and glands
What is the white matter in the spinal cord?
*like an elecator - impulses go up to brain and down to the spinal cord.
What are the parts of the spinal cord white matter?
divided into three columns (dorsal, ventral, and lateral) and two tracts that run continuously with the brain -- Sensory (afferent)and Motor (efferent)
What are the tracts in the spinal cord and what is their purpose?
Sensory (afferent) -- ascending tracts conduct impulses toward the brain
Motor (efferent) -- descending tracts conduct downward in the spinal cord
**Impulses run continuously up to brain and down to spinal cord <-- like an elevator
Where is the CSF in the Spinal Meninges?
Fills the subarachnoid space from C1 to S2
Where are the layers of the meninges located in the spine?
normal except pia mater continues to coccyx and anchors spinal cord and CSF continues till S2
What is the best place to do a lumbar puncture or spinal tap and why?
Between L2 and S2 because the spinal cord stops at the L2 so this area is all fluid.