Transcript INTEGUMENTARY SYSTEM

NERVOUS SYSTEM
CENTRAL & PERIPHERAL NERVOUS
SYSTEMS
General – CNS
CNS Protected by Bone
- Skull (Brain)
- Vertebrae (Spinal Cord)
Protected by Meninges
CNS – General continued
 Meninges
- CT Membranes between Bone & CNS
* Dura Mater
Outer, Tough, Fibrous, Double
Extends down vertebral cavity, beyond
end spinal cord
Dural Sinuses – Veins between layers
Dural Folds – Innermost layer extents
into fissures
Epidural Space – Between walls of
vertebral cavity & Dura of spinal cord
CNS – General continued
* Arachnoid Mater
Thin, Spidery, Middle
Extends past spinal cord
Subdural Space – Between Dura &
Arachnoid
Subarachnoid Space – Between Arachnoid &
Pia; Contains CSF; Sampled via spinal tap
* Pia Mater
Innermost, Delicate
Attached to Surface of Brain & Spinal Cord
Highly Vascular
CNS – Brain Structure
Cerebrum
Diencephalon
Brainstem
Cerebellum
CNS – Brain Structure
 Cerebrum
- Largest, Superior
- Two Hemispheres Separated By Longitudinal
Fissure & Bridged by Corpus Callosum
(myelinated fibers)
* Cerebral Cortex (Higher Thought Processes)
Outer, Convoluted Gray Matter
Gyri (Ridges); Sulci – Grooves
* White Matter (Surrounds Nuclei)
* Nuclei (Basal helps with posture & movement)
Brain Structure continued
- Each Cerebral Hemisphere has 5 Lobes:
* Frontal – Personality, Judgment, Behavior,
motor areas assoc. with skeletal muscle
* Parietal – Sensory Input from Skin &
Organs
* Temporal – Hearing, Smell
* Occipital - Vision
* Insula – Monitors Internal Organs &
Responsible for Aversions
Brain Structure continued
Diencephalon
-
Enclosed by Cerebrum
Between Cerebrum & Brainstem
Epithalamus
Thalamus
Hypothalamus
Epithalamus
Part of Diencephalon
Superior to Thalamus & Third Ventricle
Contains the Pineal Gland, Produces
Hormones
Thalamus
“Switchboard” for all Sensory Impulses to
Cerebral Cortex
Hypothalmus
* Coordinates Neural & Endocrine Functions
* Regulates Basic Visceral Functions
Fig. 8.24
Brain Structure continued
 Brain Stem
- Inferior to Diencephalon; Mergers with
Spinal Cord
- Controls visceral functions
- Midbrain
* Colliculi – Visual & Auditory Nuclei
- Pons – Below Midbrain, Fiber Tracts, Joins
Cerebellum to brainstem
- Medulla Oblongata – Below Pons,
Cardiovascular & Resp. Rhythmicity
Centers, Joins Brain & Spinal Cord
Fig. 8.23
Brain Structure continued
Cerebellum
-
Inferior to Cerebrum, Posterior to Brain Stem
Connects to brainstem at Pons
Outer Gray Matter
Arbor Vitae (Inner, Branching White Matter)
Controls learned motor skills
Coordinates Skeletal Muscles, Maintains
Body Tone & Equilibrium, Posture
Brain Structure continued
Ventricles
- Cavities within Brain, Filled with CSF
- Continuous with Subarachnoid Space &
Central Canal of Spinal Cord
- Lateral – Largest Two, within Cerebral
Hemispheres
- Third – Narrow, Midline, Diencephalon
- Fourth – Brain Stem, Continuous with
Central Canal of Spinal Cord
Fig. 8.36
CNS - Cerebrospinal Fluid
(CSF)
 Secreted by Choroid Plexuses (capillaries in
ventricles)
 Clear, Similar to Blood Plasma
 Most CSF produced by Lateral Ventricles
 Circulates through Ventricles, Subarachnoid
Space, Central Canal
 Supports, Absorbs Shocks, Provides Nutrients
 Sample via Spinal Tap (Subarachnoid Space,
L-4)
CNS – Spinal Cord
Protected by Bone, Meninges, CSF
Vertebral Cavity
Extends from Medulla Oblongata (Through
Foramen Magnum) to L2
16-18 inches
Two Enlargements (Limb Control):
- Cervical (Shoulder & Arms)
- Lumbar (Pelvis & Legs)
CNS – Spinal Cord continued
 Conus Medullaris – Inferior tip of spinal cord
 Cauda Equina – Nerve roots inferior to cord
tip
 Filum Terminale – Pia Mater attached to
coccyx
Fig. 8.21
CNS – Spinal Cord continued
 Outer White Matter - Bundles Myelinated
Axons
 Ascending Tracts or Pathways
- Sensory
- From Sensory Receptors to CNS
 Descending Tracts or Pathways
- Motor
- From CNS to Glands or Muscles
CNS – Spinal Cord continued
 Inner Gray Matter
- Neuron Cell Bodies & unmyelinated
processes
- Dorsal & Ventral Horns project towards outer
surface
- Dorsal Gray Horn – Interneuron Somas
- Ventral Gray Horn – Somas of Motor
Neurons
- Central Canal through Grey Commissure
CNS – Spinal Cord continued
 31 Pairs of Spinal Nerves (PNS)
- Sensory: Dorsal Roots/Ganglia, Ascending
Tracts
- Motor: Ventral Roots, Descending Tracts
 Dermatomes – skin segments supplied by
spinal nerves
Peripheral Nervous System PNS
Consists of:
- Peripheral Nerves:
* Cranial Nerves
* Spinal Nerves
* Nerve Plexuses
- Ganglia
Carries Sensory Information & Motor
Commands
PNS – Peripheral Nerves
 Nerves (PNS)
- Sensory
* Carries from Receptors towards CNS
- Motor
* Carries from CNS towards effector
- Mixed
* Both Sensory & Motor
PNS – Peripheral Nerves
Bundles of Axons
Sensory, Motor or Mixed
CT Reinforced
- Endoneurium – Surrounds each axon
- Perineurium – Around groups of axons
- Epineurium – Tough, Fibrous C.T. around
Nerve
PNS – Cranial Nerves
Twelve Pairs
I Arises from Cerebrum
II – XII from Brain Stem
Function
- Sensory
- Motor
- Mixed
PNS – Spinal Nerves
 31 Pairs:
- 8 Cervical
- 12 Thoracic
- 5 Lumbar
- 5 Sacral
- 1 Coccygeal
 All are Mixed; both Sensory (Afferent) & Motor
(Efferent)
 1 Pair at each Spinal Segment
 Attach to Spinal Cord by Ventral & Dorsal Root
 Supply Dermatomes (skin segments)
Fig. 8.21
PNS – Nerve Plexuses
Networks of Spinal Nerve Branches
-
Cervical
Brachial
Lumbar
Sacral
Reflex Arcs
 Simple Conduction Pathway
 Results in Reflex
- Fast, Predictable
- Automatic motor response
 Five Components:
- Receptor
* End of dendrite of sensory neuron
* Responds to specific stimuli
- Sensory Neuron (Receptor to CNS)
Fig. 8.18
Reflex Arcs continued
- Interneuron
* CNS Gray Matter
* Usually one but may be 0 or >1
* Transmits, Inhibits, or Reroutes to Motor
Neuron
- Motor Neuron (CNS to Effector)
- Effector
* Muscle or Gland; responds to motor impulse
* Response is Reflex (e.g. knee jerk, secretion of
digestive juices, pain withdrawl)
PNS – Somatic Nervous System
Voluntary
Controls Skeletal Muscles
Neurotransmitter=Acetylcholine
Cell Body in CNS
Axons extend to Skeletal Muscles
PNS - Autonomic Nervous
System (ANS)
Involuntary
Motor/Efferent
Chain of two Motor Neurons
Receives info from CNS; Regulates:
- Cardiac Muscle
- Smooth Muscle
- Glandular Activity
Fig. 8.39
PNS – ANS continued
Two Antagonistic Branches that Serve
same Organs:
- Parasympathetic
* “Housekeeping”
* Conserves Energy
* Craniosacral Origin (CN X)
* Effects include: Increased Gastrointestinal
Activity, Decreased heart & resp. rates
PNS – ANS continued
- Sympathetic
* “Fight or Flight”
* Expends Energy
* Thoracolumbar Origin
* Effects Include: Increased heart & resp.
rates, Constriction of blood vessels,
Increased blood pressure, Pupil dilation,
Bronchiole dilation, inhibition of G.I.
activity