Chapter 11 slides lecture 1 narrated

Nervous system does three things

1. sensory input
   - information gathered by sensory receptors about internal and external changes
   - vision, taste, hear, touch, etc
   - sensory information comes from peripheral receptors into CNS where there is integration

2. Integration:
   - interpretation of sensory input
   - only takes place in CNS (spinal cord or brain)
   - have input have to decide what to do, this is where the output or motor comes in

3. Motor output:
   - activation of effector organs (muscles and glands) produces a response
   - ex: contract skeletal muscle, smooth muscle, cause glandular secretion, or nothing

How is the nervous system organized?

• Central Nervous System (CNS)
  - made up of neurons and supporting cells (glial cells)
  - receives information from and sends information to the peripheral nervous system
  - brain and spinal cord
  - integrative and control centers, where conscious thought takes place

• Peripheral Nervous System (PNS)
  - made up of cranial nerves (nerves that branch off brainstem) and spinal nerves (nerves that branch off the spinal cord)
  - these nerves carry information away or to the CNS
  - Sensory (afferent) division
  - carries information toward the CNS
  - Somatic (body):
  - carries information from the body surface to the CNS
  - Visceral (organ)
  - carries information from the organs to the CNS
  - Motor (efferent) division
  - all about output
  - carries information away from the CNS
  - can carry information to skeletal muscle, to smooth muscle or to glands
  - Somatic (body):
  - voluntary motor system
  - controls and how we chose to stimulate certain muscles to contract
  - Autonomic:
  - involuntary
  - visceral mater: controls organ functions, glandular secretion, smooth muscle, cardiac muscle, glands, NOT SKELETAL MUSCLE
  - Sympathetic division:
  - associated with flight or fight
  - mobilizes body systems during activity
  - parasympathetic division:
  - rest and digest
  - aids in digesting food
  - conserves energy
  
  

Histology of Nervous Tissue

• There are two principal cell types in the nervous system
  1. Neuroglia (glial cells)- supporting cells:
  - makes neurons function better
  - support the functions of the neurons
  1. Astrocytes (CNS)
  2. Microglia (CNS)
  3. Ependymal cells (CNS)
  4. Oligodendrocytes (CNS)
  5. Satellite cells (PNS)
  6. Schwann cells (PNS)
  2. Neurons
  - excitable cells that transmit information at synapses signals

Astrocytes

• they have soma, then lot of projections out like starburst

• most abundant, versatile and highly branched glial cells

• cling to neurons, synaptic endings, and capillaries

• support and brace neurons

• help determine capillary permeability
  - the cells of the capillaries are normally bound together by tight junctions and astrocytes can regulate the tightness of these tight junctions
  - astrocytes can make tight junctions tight or loose to let nutrients to cross or not

• help regulate access to nutrients for neurons

• hold large portions of the CNS together
  - hold blood vessels in place, neurons in place, etc because there is little connective tissue

• clean up and take care of the environment of the neurons

• help regulate the whats in the interstitial fluid such as potassium which can be toxic if theres to much

Microglia

• immune cell

• can phagocytosis a macrophage
  - this is how it “sounds the alarm”

• dendritic cell

• helps clean injured neurons, dead neurons and removes them

• small ovoid cells with thorny processes

• migrate toward injured neurons
  
  

Ependymal cells

• line the central cavities of the brain and spinal column

• separate the CNS interstitial fluid from the cerebrospinal fluid

• produce CSF at choroid plexuses (location within the ventricles)

• may be ciliated
  - cilia helps the CSF move through the canal like system

• range in shape from squamous to columnar

• line all of the ventricles and the spaces associated with the ventricles in the CNS such as:
  - cerebral aqueduct
  - central canal
  - spinal cord

• some areas the ependymal cells have tight junctions, other areas tight junctions are present but not as tight

Oligodendrocytes

• cells within the central nervous system that produce myelin
  - myelin sheath is insulator, wraps around the axons of neurons and this helps to speed up the conduction of action potentials down the length of the axon

• branched cells

• processes wrap around multiple axons in CNS which is what forms the myelin sheath

• multiple sclerosis (demyelination, lost of oligodendrocytes, in the CNS)
  - oligodendrocytes die and are no longer present

Satellite cells

• PNS

• surround nueron cell bodies in the PNS

• regulate environemnt and access to nutrients for neurons

• help hold and bind things together

• similar to astrocytes

Schwann cells (neurolemmocytes)

• PNS

• surround peripheral nerve fibers and form myelin sheaths

• vital to regeneration of damaged peripheral nerve fibers

• produce myelin similar to the way oligodendrocytes produce myelin

• wrap around axons and help speed up the conduction of action potentials down the length of the axon

• pathology: degenerative disease where schwann cells die: Lou Gehrig's disease or ALS
  - ALS leads to death of neurons and loss of overall function

Neurons (nerve cells)

• primary cell in the nervous system

• long lived: 100 years or more

• amitotic- few exceptions

• expensive to maintain because they consume large amounts of energy

• plasma membrane functions in:
  - electrical signaling
  - cell-to-cell interactions during development