Download Cerebrospinal fluid (CSF)

Bio 160 – Nervous System – Chap. 8
Functions:
- sensory
- integration
- motor
General Organization: (fig. 8-1)
1. Central nervous system (CNS)
2. Peripheral nervous system (PNS)
a. afferent division
b. efferent division
i. Somatic Nervous System (SNS)
ii. Autonomic Nervous System (ANS)
Histology of neural tissue:
1. Neuroglia (glial cells):
a. CNS i. astrocytes
ii. oligodendrocyte
iii. microglia
iv. ependymal
b. PNS i. Schwann cells (neurolemmocytes)
ii. satellite cells
2. Neuron:
Structure:
cell body
dendrites
axon
telodendria
synaptic terminals (synaptic end bulbs/knobs)
myelin sheath:
Classification of neurons:
1. Structural:
a. multipolar
b. bipolar
c. unipolar
2. Functional:
a. sensory (afferent)
b. motor (efferent)
c. association (interneuron)
Reflexes/reflex arc: (fig. 8-28 & 8-29, p. 272)
Anatomical organization of neurons :
PNS - nerves
ganglion
CNS - tracts/pathways
nucleus/center
Neuron Function: Impulse conduction (Action potential (AP))
Polarized membrane
Membrane potential (transmembrane potential)
Resting membrane potential (RMP)
Graded potentials
Threshold stimulus
Action potential
Depolarization
Repolarization
Hyperpolarization
Continuous propagation/conduction vs. Saltatory propagation/conduction
“All or None” principle
Conduction across synapses:
Presynaptic neuron
Synaptic cleft
Postsynaptic neuron
Excitatory neurotransmitters
Inhibitory neurotransmitters
CNS
Meninges –
Dura mater, Arachnoid, Pia mater,
Dural folds, dural sinuses
Epidural space, subarachnoid space, filum terminale
The Spinal Cord
Anatomy:
-cervical enlargement & lumbar enlargement
-conus medularis
-spinal cord segments, dorsal roots, dorsal root ganglion (DRG), ventral roots & spinal nerves (8
cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal)
-cauda equina
-anterior median fissure & posterior median sulcus
-gray matter horns (anterior, posterior & lateral (T1-L2, S2-S4)
-gray commissure, central canal
-white matter columns (anterior, lateral, posterior)
Ascending tracts/pathways: (table 8-4, p. 275)
1. Spinothalamic
-Poorly localized touch, pressure, pain & temperature
2. Posterior Columns
-Discriminative (fine) touch, vibration, conscious proprioception (to cerebrum)
3. Spinocerebellar
-Unconscious proprioception (to cerebellum)
Descending tracts:
1. Corticospinal (pyramidal)
-Conscious (voluntary) control of skeletal muscles
2. Medial & Lateral pathways
- Subconscious coordination of motor activity, posture, muscle tone
The Brain
Principal divisions:
 Brain stem
o Medulla oblongata (MO)
o Pons
o Midbrain
 Diencephalon
o Thalamus
o Hypothalamus
o Epithalamus (pineal gland)


Cerebrum
Cerebellum
Cerebrospinal fluid (CSF):
-functions – protection, nutrient supply, waste removal
-formed by filtration & secretion at “choroid plexuses” in each ventricle ((2) lateral, third, fourth)
-CSF circulation:
lateral ventricles (in cerebral hemispheres) interventricular foramen third ventricle (in
diencephalon)  cerebral (mesencephalic) aqueduct  fourth ventricle (bet. Cerebellum/pons)
central canal of SC & subarachnoid space  reabsorption through arachnoid villi/granulations in
superior sagittal sinus  veins
I. Brain stem
A. Medulla oblongata – continuation of SC above foramen magnum
- pyramidal decussation
- cranial nerve nuclei ( VIII (cochlear), IX, X, XI, XII)
- reflex centers (cardiac, respiratory, vasomotor)
B. Pons – connects cerebellum to SC & parts of brain
-
cranial nerve nuclei (V,VI, VII, VIII (vestibular)
respiratory center
C. Midbrain
- cerebral peduncles
- corpora quadrigemina
- superior colliculi – visual reflex center
- inferior colliculi – auditory reflex center
- cranial nerve nuclei ( III,IV)
- reticular formation – maintains states of consciousness
II. Diencephalon
A. Thalamus
- thalamic nuclei surrounding third ventricle, connected by intermediate mass
- sensory relay station
B. Hypothalamus
- connected to pituitary gland via infundibulum
- functions mainly related to homeostasis include (but are not limited to):
1. integration of ANS from visceral stimuli
2. physical and functional connection between nervous & endocrine systems
3. hormone production (oxytocin & ADH)
4. hunger, satiety, thirst, body temperature regulation
5. coordination (subconscious) of skeletal muscle contractions associated with strong emotions
(rage, pleasure, pain, sexual arousal)
6. mamillary bodies – reflex centers associated with eating & processing of olfactory sensations
C. Epithalamus
- pineal gland – melatonin production
III. Cerebrum
- two hemispheres separated by longitudinal fissure
- cerebral cortex (gray matter) with convolutions (gyri/sulci)
- lobes of cerebral hemispheres, separated by sulci:
a. frontal lobe – separated from parietal by central sulcus, & from temporal by lateral sulcus
b. parietal lobe – sep. from frontal by central sulcus, from occipital by parieto-occipital sulcus
c. temporal lobe – sep. from frontal by lateral sulcus, “insula” lies deep to lateral sulcus
d. occipital lobe – sep. from parietal by parieto-occipital sulcus
-
white matter deep to gray; comprised of myelinated axons connecting areas
a. association fibers – connect gyri within hemisphere
b. commissural fibers – connect gyri in opposite hemispheres (ie. Corpus collosum)
c. projection fibers – connect cerebrum with other parts of brain & SC
-
functional areas of cerebrum:
1. Motor & sensory areas
a. frontal lobe –
 primary motor cortex – pre-central gyrus
 gustatory cortex
b. parietal lobe
 primary sensory area – post-central gyrus
c. temporal lobe
 auditory cortex
 olfactory cortex
d. occipital lobe
 visual cortex
2. Association areas – interpret incoming data or coordinate a motor response
 somatic motor association area (pre-motor cortex)
 visual association area
3. Cerebral processing centers- “higher-order” integrative centers; many are unilateral
 general interpretive area (Wernike’s area)
 motor speech center (Broca’s area)
 prefrontal cortex
IV. Limbic system
- functionally related areas in cerebrum, thalamus & hypothalamus involved in
a. emotional states & subsequent behaviors
b. linking conscious intellectual functions of cerebrum with unconscious & autonomic functions
in brainstem
c. long term memory storage & retrieval
V. Cerebellum
- functions include control of subconscious skeletal muscle movement necessary for balance,
coordination & posture
- separated from cerebrum by transverse fissure
- gray matter “folia” surrounds white matter “arbor vitae”
PNS
Spinal nerves:
-31 pair of “mixed” nerves that supply both sensory receipt from & motor control of specific regions of the body
-Form at union of dorsal & ventral root in intervertebral foramen (IVF) of vertebral column
-branches of most spinal nerves interweave to form specific “nerve plexuses”, which then give rise to specific
peripheral nerves (table 8-3)
a. cervical plexus (C1-C5) - phrenic nerve
b. brachial plexus (C5-T1) - median nerve, radial nerve, ulnar nerve
c. intercostal nerves (T2-T11)
d. lumbar plexus (T12-L4) - femoral nerve
e. sacral plexus (L4-S4) – sciatic nerve
Cranial Nerves: (know name, #, and basic function) (p. 268-270)
I.
II.
III.
IV.
V.
VI.
VII.
VIII.
IX.
X.
XI.
XII.
Olfactory – smell
Optic – sight
Occulomotor – eye movement, ANS for accommodation of lens & pupil constriction
Trochlear – eye movement
Trigeminal – muscles of mastication, sensation to face/mouth
Abducens – eye movement
Facial – muscles of facial expression, taste (ant. tongue), ANS to lacrimal(tears)/salivary glands
Vestibulocochlear – equilibrium & hearing
Glossopharyngeal – swallowing, taste (post. tongue), ANS to salivary gland
Vagus - ANS visceral muscle movement (respiratory, digestive, cardiovascular systems)
(Spinal) Accessory – swallowing, SCM, Trap’s
Hypoglossal – tongue movement
Autonomic nervous system (ANS)
Functions – regulation (motor) of “visceral effectors” (smooth muscle, cardiac muscle, glands & adipose
tissue) through stimulation of “visceral efferent (motor) fibers”
Two divisions – Sympathetic (Σ) & Parasympathetic (PΣ)
- sympathetic – “fight or flight” responses
- parasympathetic – “rest and repose” (“conserve & restore”) responses
Many organs receive both Σ & PΣ = “dual innervation”. One division will be excitatory & other will inhibit activity
General organization of ANS:
Preganglionic neuron (from CNS; myelinated; cholinergic)  autonomic ganglion (excitatory synapse)
 postganglionic neuron (from ganglion; unmyelinated; cholinergic (Ach) or adrenergic (NE) ) 
visceral effector (effect dependent upon neurotransmitter released & upon specific receptors present)
Sympathetic:
- cell bodies of preganglionic neurons in lateral gray horns T1-L2 (“thoracolumbar division”)
- axons (Σ fibers) travel out with spinal nerve to enter ganglion
- Σ ganglia include:
a. sympathetic chain ganglia
b. prevertebral (collateral) ganglia
c. adrenal medullae
- preganglionic fibers release Ach & synapse with many postganglionic neurons in the ganglion
- postganglionic fibers may synapse on different visceral effectors & usually release norepinephrine
(NE)
- effects on visceral effectors are usually excitatory but the actual effect on the organ/tissue depends
on the interaction with the specific receptor present (α or β)
Parasympathetic:
- cell bodies of preganglionic neurons in CN’s III, VII, IX, X, & lateral gray horns S2-S4 (“craniosacral
division”)
- preganglionic fibers travel to “terminal” ganglia or “intramural” ganglia near or in visceral effector
- preganglionic fibers release Ach & synapse with few postganglionic neurons in the ganglion
- postganglionic fibers release Ach but effects on organ depend on interaction with specific receptor
present (nicotinic or muscarinic)
Activities of ANS: (table 8-5)
Sympathetic – “fight or flight” response (energy expenditure)
- increased heart rate; increased BP; increased respiratory rate; bronchodilation; pupil dilation;
vasodilation to brain, heart, muscles, lungs; release of energy reserves (lipids from adipose
tissue & glucose (glycogen) from liver & skeletal muscle); release of Epi & NE from adrenal
medullae to continue effects
Parasympathetic – “rest & repose” response (conserve & restore energy)
- decreased heart rate; decreased BP; decreased respiratory rate; pupil constriction; GIT
stimulation & enzyme secretion; nutrient uptake; energy storage; etc.