1. The nervous system chapter 12, 13 and 14
Central Nervous System (CNS)
Brain
Spinal Cord
Peripheral Nervous System (PNS)
Sensory Neurons
Motor Neurons
Somatic Nervous System
Autonomic Nervous System
Sympathetic
Parasympathetic
The Nervous System

2. Our approach will be to cover functional systems:
Subjects we will cover
Our approach will be to cover functional systems:
Somatic nervous system – sensory and motor
Autonomic nervous system
Special senses
All system will cover both the central and peripheral nervous systems

3. Neurons in the nervous system link together to form circuits with specific functions.

4. Nervous system functions
Motor functions
Control contraction of skeletal muscles – somatic nervous system
Control contractions of smooth and cardiac muscle – autonomic nervous system
Control of glands function – autonomic nervous system
Sensory and integrative functions
Process incoming information to ensure appropriate motor response
More than 99% of the incoming information is classified as irrelevant and unimportant

5. 3 Major levels of the CNS Spinal cord
involved in walking movement, reflexes of both skeletal muscles and the autonomic nervous system effectors
Lower brain/subcortical level
Subconscious activities of both the autonomic and somatic nervous system. Involved in several emotional patterns
Higher brain/cortical level
Very large memory storage, place of higher functions like thoughts, awareness

6. Peripheral nervous system components
Includes nerves and ganglia
Most nerves are mixtures of afferent and efferent fibers and somatic and autonomic (visceral) fibers
Pure sensory (afferent) or motor (efferent) nerves are rare
Peripheral nerves classified as cranial or spinal nerves
Ganglia contain neuron cell bodies associated with nerves
Dorsal root ganglia (sensory, somatic) (Chapter 12)
Autonomic ganglia (motor, visceral) (Chapter 14)

7. CNS protection
Bony protection by the skeleton – brain by skull and spinal cord by vertebrae
3 layers of membrane collectively called meninges that are found between the bone and the CNS tissue
Cerebro-spinal fluid – CSF - found in the ventricles, central canal and subarachnoid space
Blood brain barrier - BBB

8. http://tle. westone. wa. gov

9. Choroid Plexuses and CSF
Clusters of capillaries and the ependymal cells

10. The choroid plexus forms tissue fluid filters
CSF production
The choroid plexus forms tissue fluid filters
Have ion pumps that selectively pump ions from the plasma into the ventricles.
The ions pumps create osmotic pressure that draws water to the CSF
the choroid plexus of the lateral ventricles producing the most.
The rate of formation is approximately 0.35 ml/min or 500 ml/day; a rate which replaces the total volume of CSF approximately 2-3 times over in 24 hours.

11. CSF – cerebrospinal fluid functions
Liquid cushion for brain and spinal cord
Nourishes brain
Removes waste
Conducts chemical signals between parts of CNS

12. Why are the capillaries in the BBB less permeable?
Endothelial cells form tight junctions that prevent solutes movement between cells
Astrocytes
Selective transport properties of the endothelial cells
The BBB
Helps maintain a stable environment for the brain
Separates neurons from some bloodborne substances

14. Blood-Brain Barrier: Functions
Selective barrier that allows nutrients to pass freely
Is ineffective against substances that can diffuse through plasma membranes (ex. Ethanol, caffeine)
Absent in some areas:
Ex. - hormones generally do not penetrate the brain from the blood, so in order to control the rate of hormone secretion effectively, there are specialized sites where neurons can "sample" the composition of the circulating blood. At these sites, the blood-brain barrier is 'leaky‘ (pituitary gland)
Capillaries of the choroid plexus
The BBB can break down under certain conditions:
hypertension, radiation, infection and brain trauma

15. Spinal Cord
Because the cord does not reach the end of the vertebral column, the lumbar and sacral spinal nerve roots angle sharply downward and travel inferiorly before reaching their intervertebral foramina
This collection of nerve roots at the inferior end of the vertebral canal is called the cauda equina

16. Gray Matter: Organization
Dorsal root (sensory)
Dorsal root ganglion
Dorsal horn (interneurons)
Somatic
sensory
neuron
Visceral
sensory
neuron
Visceral
motor
neuron
Spinal nerve
Ventral horn
(motor neurons)
Ventral root
(motor)
Somatic
motor neuron
Interneurons receiving input from somatic sensory neurons
Interneurons receiving input from visceral sensory neurons
Visceral motor (autonomic) neurons
Somatic motor neurons
Figure 12.32

17. White Matter in the Spinal Cord
Composed of both myelinated and unmyelinated fibers that run in three directions
Ascending – to higher centers; sensory
Descending – to lower levels from brain or higher places in the cord; motor
Transversely – from one side of the cord to the other
Divided into three funiculi (columns) – posterior, lateral, and anterior
Each funiculus contains several fiber tracks with similar destination and function
Fiber tract names reveal their origin and destination
Fiber tracts are composed of axons with similar functions

18. Structure of a Nerve
Nerve – cordlike organ of the PNS consisting of peripheral axons enclosed by connective tissue
Connective tissue coverings include:
Endoneurium – loose connective tissue that surrounds axons
Perineurium – coarse connective tissue that bundles fibers into fascicles
Epineurium – tough fibrous sheath around a nerve

19. Spinal Nerves: Rami Small dorsal ramus Larger ventral ramus
The short spinal nerves branch into three or four mixed, distal rami
Small dorsal ramus
Larger ventral ramus
Tiny meningeal branch – innervate the meninges and blood vessels within the vertebral canal
Rami communicantes at the base of the ventral rami in the thoracic region that contain autonomic nerve fibers

20. Nerve Plexuses
All ventral rami except T2-T12 form nerve networks called plexuses
Plexuses are found in the cervical, brachial, lumbar, and sacral regions
Each resulting branch of a plexus contains fibers from several spinal nerves
Fibers travel to the periphery via several different routes
Each muscle receives a nerve supply from more than one spinal nerve
Damage to one spinal segment cannot completely paralyze a muscle

21. Plexus
Main spinal nerves
Regions innervated
Major nerves
Cervical
C1-C5
Skin and muscles of head & neck. Superior chest and shoulder
Phrenic (diaphragm)
Brachial
C5-C8, T1
Shoulder and upper limbs
Axillary Musculocutaneous Radial
Median
Ulnar
Lumbar
L1-L4
Antero-lateral abdominal wall, external genitalia, part of lower limbs
Femoral
Sacral
L4-L5, S1-S4
Buttocks, perineum, lower limbs
Sciatic