Download Everson Nervous system I. Functional/ Anatomical Divisions A

Everson
Nervous system
I.
Functional/ Anatomical Divisions
A. Central Nervous System: CNS
1. Brain
2. Spinal cord
B. Peripheral Nervous System: PNS
1. functions in general
2. Divisions
1. Afferent division
2. Efferent division
a. Somatic
b. Autonomic
i. Sympathetic
ii. Parasympathetic
II.
Nervous Tissue/Cells
A. Neurons
1. general structure
2. Types
1. Motor neuron
2. Sensory neuron
3. Interneuron
B. Schwann Cells
1. neurolemma
2. PNS cells
1. Glial cells types and functions :
1. Oligodendrocytes
2. Astrocytes
3. Microglia
4. Ependyma
C. Nerve cell impulse transmission: the electricity!
1. Essentially the same as described in muscle impulse.
2. Neuron not carrying an impulse is said to be _______________,
where the Na+ ions are more abundant on the outside and the K+
ions are most abundant on the inside.
3. A stimulus, like a __________________ that is released from
another neuron makes the neuron cell membrane (more or less?)
permeable to Na+. This causes ________________ of the
membrane, where the inside becomes more positively charged
than the outside.
4. This initial reversal of charge is propagated down the axon
(saltatory conduction in myelinated axons) to the axon terminals.
5. The electrical impulse then causes the release of the
_________________________ which diffuses across the
_________________________ and binds with the receptor cells.
CNS structure and Function:
1. Spinal Cord:
a. Protection:
i. bony vertebra inside the vertebral foramen
1. diameter is @ ¾ “
2. spinal cord extends from
_______________________________________
3. Cauda equina ___________________________
a. Lumbar puncture
ii. meninges coverings to L3-L4
1. Three layers of connective tissue coverings
a. Dura mater (hard mother) forms outer most
covering of spinal cord
i. Space between dura mater and walls of
vertebral canal is called the
_____________space = loose c.t,. blood
vessels and fat
ii. Epidural block
b. Arachnoid membrane
i. Made of epithelia tissue, collagen and
elastic fibers for a “cob web” appearance
ii. Cerebral spinal fluid circulates in the
central canal and subarachnoid space
c. Pia Mater (delicate mother) innermost of
meninges
i. Contains connective tissue and all the
blood vessels that service the spinal cord
are found here.
ii. Firmly bound to the neural tissue
iii. Cerebral spinal fluid (CSF)
1. Functions to
a. ____________________________
b. _____________________________
c. _____________________________
2. Formed in the brain by the______________
b. Cross-sectional structure
i. “butterfly” shape of grey matter surrounds central canal.
1. contains the soma of motor neurons and interneurons
ii. white matter surrounds grey matter
1. made of myelinated axons and dendrites of
interneurons
2. nerve tracts: groups of neurons within the CNS
iii. spinal nerves exit spinal cord
1. dorsal root made of sensory neurons = info in and
dorsal root ganglia contain soma of those neurons
a. Shingles and chicken pox
2. ventral root made of motor neurons = info out
3. together form a “spinal nerve” = mixed nerve
c. Spinal Reflexes
i. Reflex arc= pathway of nerve impulses in reflex
ii. Five parts to reflex arc
1. receptors (for pain, stretch, position etc.) detect info
2. sensory neurons relay info to spinal cord
3. CNS (aka spinal cord) integrates info (interneurons)
4. motor neurons transmit response
5. effector organ performs response
iii. Types of reflexes:
1. Stretch reflex occurs when a muscle that is stretched
will automatically contract. Example: Patellar reflex
2. Flexor reflexes or withdrawal reflexes are in response
to a painful stimulus.
3. Babinski reflex: used to test spinal cord integrity.
2. Brain
a. Major “divisions of the brain
i. Brain stem
1. medulla –attaches to the spinal cord
a. functions in “vital signs” with centers for heart
rate, vasoregulation, respiration
b. non”vital” centers like vomiting, coughing,
sneezing and hiccoughing
c. contains motor and sensory nuclei (attachment)
for five cranial nerves (VII, IX, X, XI, and XII)
2. pons
a. anterior to medulla, connects brain to lower
part of brain stem
b. respiratory centers
c. contains motor and sensory nuclei for four
cranial nerves (V, VI, VII and VIII)
3. midbrain
a. encloses the cerebral aqueduct (CSF)
b. visual and auditory reflexes
c. righting reflexes for head
d. areas that release dopamine if damaged result in
Parkinson’s disease (difficulty starting voluntary
movements because opposing muscles never
relax)
e. contains motor and sensory nuclei for two
cranial nerves ( III, and IV)
ii. Cerebellum
1. Two primary functions
a. Adjusting postural muscles of body (balance
and equilibrium)
b. Programming and fine-tuning movements
controlled at conscious and unconscious levels
c. Can be affected by alcohol (temporary), stroke
or trauma (permanently) resulting in ataxia a
disturbance in balance
iii. Hypothalamus
1. Seven functions
2. Regulates and coordinates ANS with CNS
3. Links to endocrine system
4. forms floor of third ventricle (CSF)
iv. Thalamus
1. Encloses the third ventricle (CSF)
2. functions concern sensations
3. integrates sensory info for cerebrum interpretation
v. Cerebrum (Cerebral hemispheres)
1. Right and left cerebral hemispheres
a. Separated by longitudinal fissure
b. Connected by Corpus callosum
c. Sulci and gyri (grooves and bumps)
d. Each contain a lateral ventricle (CSF)
2. Three main points about cerebral hemispheres:
a. Each cerebral hemisphere receives sensory
information from and sends motor information
to the opposite side of the body
b. The two hemispheres have different functions
even though they appear identical
c. Assignment of a specific function to a specific
region of the cerebral hemisphere is imprecise.
3. Regions of the cerebral cortex include:
a. Frontal lobes
b. Parietal lobes
c. Temporal lobes
d. Occipital lobes
e. Association areas
Cerebral Spinal Fluid
b. Formation:
i. Choroid plexuses found in the ventricles of the brain
1. clusters of thin walled capillaries covered by a layer of
ependymal cells
c. Composition:
i. Similar to plasma but has:
1. less protein
2. more Vitamin C
3. more Na+, Cl-, Mg++, H+
4. less Ca++ and K+
d. Hydrocephalus
i. When something (like a tumor) obstructs circulation or
drainage, CSF accumulates and exerts pressure on the brain.
ii. Babies heads swell, due to flexible skull. Adults results in
brain damage.
iii. Treated by placing a shunt in the ventricles of brain to drain the
excess fluid into a vein in the neck
3. Plantar reflex vs. Babinski’s reflex:
a. Plantar reflex normal reaction to rubbing a blunt object along the
lateral aspect of the sole of the foot
i. Toes curl (flex)
ii. Tests for the integrity of spinal cord from L4 to S2 and
indirectly determines if corticospinal tracts are working
b. Babinski sign (reflex)
i. Blunt object on sole of foot results in dorsiflexion of the great
toe and the small toes fan laterally
ii. Normal response in infants < 1 year old due to incomplete
myelination of N.S.
iii. Not normal in adults and is a results from damage to the
primary motor cortex or the corticospinal tracts.
4. Lateralization of brain: unique abilities of each hemisphere or the division of
labor
a. Left cerebral hemisphere is dominant in 90% of people
i. Deals with logic, language and math skills
ii. Most people with left cerebral dominance are right handed
b. Right cerebral hemisphere
i. Deals with visual spatial skills, intuition, emotion and creative
skills
ii. Dominant in 10% of people or will share functions equally
with Left hemisphere
iii. Typically Right cerebral dominant people are left handed and
male