Transcript INTEGUMENTARY SYSTEM

NERVOUS SYSTEM
CENTRAL & PERIPHERAL NERVOUS
SYSTEMS
Structural Divisions of Nervous
System
Central Nervous System (CNS)
- Brain, Spinal Cord
Peripheral Nervous System (PNS)
- Cranial Nerves
- Spinal Nerves
CNS – Brain
Four Major Brain Regions:
- Cerebrum
- Diencephalon
- Brainstem
- Cerebellum
CNS – Cerebrum
Cerebrum
- Largest, Superior
- Two Hemispheres
*Separated By Longitudinal Fissure
*Connected by Corpus Callosum
(myelinated axons)
- Two Layers: Outer Cortex (gray matter) &
Inner White matter
Cerebrum continued
Cerebral Cortex
- Neuron Cell Bodies & Unmyelinated
processes
- Gyri (ridges) & Sulci (grooves)
White Matter (Myelinated axons)
Nuclei (gray matter imbedded in white)
Lobes of Cerebrum
Each Cerebral Hemisphere has 5 Lobes:
- Frontal – Personality, concentration, problem
solving, voluntary control of skeletal muscle
- Parietal – Skin sensation, speech &
language, expression of thought
- Temporal – Hearing, smell
- Occipital – Vision
- Insula – Bodily self-awareness; sense of
disgust to smells, contamination, mutilation
CNS - Diencephalon
Diencephalon
-
Enclosed by Cerebrum
Between Cerebrum & Brainstem
Epithalamus
Thalamus
Hypothalamus
Diencephalon: Epithalamus
Superior to Thalamus & Third Ventricle
Contains the Pineal Gland, Produces
Hormones
Diencephalon: Thalamus
“Relay station” for all sensory impulses to
cerebral cortex
Consists of 2 lobes joined by “Intermediate
Mass” (a bridge of gray matter)
Third ventricle is superior & medial to
thalamus
Diencephalon: Hypothalamus
Below thalamus
Controls pituitary function
Controls regulatory functions
- Helps regulate body temperature
- Feeding/Thirst
CNS - Brain Stem
Between Diencephalon & Spinal Cord
Three parts:
- Midbrain
* Colliculi – visual & auditory nuclei
- Pons – Below midbrain; joins cerebellum to
brainstem
- Medulla Oblongata – Below Pons,
Regulates heartbeat & breathing; has role
in consciousness; joins brain & spinal cord
CNS - Cerebellum
Inferior to Cerebrum, Posterior to Brain
Stem
Joined to brainstem by Pons
Two hemispheres with convoluted surfaces
- Outer Gray Matter
- Arbor Vitae (Inner, Branching White
Matter)
Provides involuntary coordination of body
movements
Protection of the CNS
CNS Protected by:
- Bone
*Skull (Brain)
*Vertebrae (Spinal Cord)
- Meninges (C.T. membranes)
- Cerebrospinal Fluid (CSF)
- Blood-Brain barrier (harmful
substances in blood)
CNS – Meninges
 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 – Meninges
* Arachnoid Mater
Thin, Spidery, Middle
Extends past spinal cord
Subdural Space – Between Dura &
Arachnoid
Subarachnoid Space – Between Arachnoid &
Pia; Contains CSF
* Pia Mater
Innermost, Delicate
Attached to Surface of Brain & Spinal Cord
Highly Vascular
CNS - Brain Ventricles
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 &
ependymal cells 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)
Spinal Tap
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
 Outer White Matter – Bundles of 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 (somas) & unmyelinated
processes
- Dorsal Gray Horn – Interneuron Somas
- Ventral Gray Horn – Somas of Motor
Neurons
- Central Canal in Grey Commissure
Peripheral Nervous System PNS
Consists of:
- Peripheral Nerves:
* Cranial Nerves
* Spinal Nerves & Nerve Plexuses
- Ganglia
- Sensory Receptors
Carries Sensory Information & Motor
Commands
PNS – Nerves
 Bundles of Axons
 Sensory, Motor or Mixed
 CT Reinforced
- Endoneurium –
Surrounds each axon
- Perineurium – Around
each fascicle (group of
axons)
- Epineurium – Tough,
Fibrous C.T. around Nerve
PNS – Cranial Nerves
Twelve Pairs
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)
 Attach to Spinal Cord by Ventral & Dorsal Root
Fig. 8.21
Reflex Arcs
 Simple Pathway
 May not involve brain
 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)
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)
Types of Reflexes
Somatic reflexes:
- Skeletal muscle
Involuntary (Autonomic) reflexes:
-
Smooth muscle
Heart and blood pressure
Glandular secretion
Digestive system regulation