Nervous System

what is the CNS?

Tissue: NT (gray matter and white matter)

• tissue builds the organs

• 2 organs in PNS: nerves, ganglia

• 2 organs in CNS: brain, spinal cord

• forms the organ system: NS

Neurons and Glial cells in NS

Neuron Classification:

Functional types:

• sensory, interneurons, motor neurons

Structural types:

• unipolar, bipolar, multipolar

Reflex Arc: What are the 5 types?

the structures/anatomy that allow you to observe a reflex

1. sensory receptor

2. sensory neuron

3. intraneuron: are all in the CNS

4. motor neuron:

5. effector: muscle (contract) or a gland (secrete)

Vocab:

• dendrites: branching. collecting information from another neuron and sending that information to another body

• axon: end of a nerve cell

• multipolar neuron:

• bipolar neuron: a few sensory neurons are bipolar

• pseudounipolar: only one extension (looks like 2)

• Nissl substance: rough ER. extends into dendrites but not axons

Glial

The 6 Glial cells:

1. astrocyte: physically hold things together (no CT in brain) (found in CNS) fxn=physical support. holds capillaries w/ perivascular meat

2. microglial cell: found in CNS, resident phagocyte

3. ependymal cells: line the tiny opening that runs through the spinal cord and tiny spaces in brain: ventricles

4. oligodendrocyte: form a myelin sheath

   forms the white matter

5. sensory neurons w Schwann cells: they myelate axons in the PNS. have to have gaps btwn schwann cells (nodes of ranvier)

6. satellite cells: pass nutrients to unipolar neuron. found in PNS

Vocab:

• parivascular foot: form blood brain barrier . prevents medicine from going to the brain. protect brain from strange chemicals in the body

• phagocyte: a cell that eats things

the NS is divided into CNS and PNS

• PNS gets divided into sensory and motor

  • 2 divisons of sensory: general and special

  • 2 divisons of motor: SNS (somatic- skeletal muscle) and ANS (autonomic-cardiac m, smooth m, glands)

    • ANS is divided into sympathetic (tells structures what to do in emergency) and parasympathetic (tells structures what to do when resting)

      no neural cell bodies in nerves

Myelin factors

• no myelin, unmyelinated

• myeilnated, by oligodendrocytes

  • axon is myelinated by oligodendrocytes

• myelinated, by Schwann cells

• unmyelinated, but associated w Schwann cells

Synapse: a gap btwn a sensory receptor and a neuron

1. sensory receptior (axon terminal)

2. synaptic cleft (very tiny can only see thru microscope)

3. post synaptic membrane (what the synaptic cleft touches) (transmitters are released)

sympathetic gangilia:

parasympathetic gangilia: usually in the wall of the target organ

epidural space- has adipose fat

Spinal Cord:

characteristics

• connects brain to periphery(sensory receptors & effectors)

• is located in vertebral column (for protection)

Anatomy

1. Spinal Meninges (protection & coverings)
   meninges= CT coverings that encircle brain & spinal cord

• pla mater (inner) delicate CT w collagen, vascular, closely adheres to brain & spinal cord, but there’s a subpial space

• epidural space: areolar+adipose CT (skull only)

• subdural space:potential space

• Arachnoid (middle) collagen & elastic fibers; trabeculae attach arachnoid to pia mater; subarachnoid space contains CSF

• Dura mater (outer) dense fibrous CT

• pia mater: areolar CT

2. external antomy of spinal cord

   • cauda equina (tail)

   • conus medularis

   • terminal filament of pia

   • terminal filament of dura

3. internal anatomy

   (in spinal cord gray matter is inside, white is outside)

   (gray matter forms horns)

• horns (grey matter) have different neuron cell bodies

  • posterior horn

  • lateral horn

  • anterior horn

  • tract

  • nerve

plexus=network

Functions of spinal cord

• “information highway”

• integration-reflexes: simple, complex; somatic, autonomic

grey matter=cortex and nuclei

central nervous system

• brain and spinal cord (housed in bone)

• fxn=processes and integrates information

Organs of the PNS

Ganglia (2 kinds)

• sensory: sensory neuron cell bodies & satellite cells

• autonomic: postganglionic autonomic (neuron cell bodies)

Nerves (2 kinds: cranial and spinal): all spinal nerves are mixes, have sensory & motor fibers

• nerves have CT

• endoneurim around nerve fiber: aerolar CT, covers individiual neural fibers (may be myelinated)

• perineurium around fascicles- covers facicles

• epineurium around entire nerve- fibrous CT outside nerve

Basic Organization

communication, control, coordination “the 3 C’s”

PNS?

peripheral nervous system

• physically connected to CNS; includes nerves, ganglia, receptors

• fxn=deliver info to/from CNS

what are the functional divison of NS?

Sensory NS: responsible for receiving sensory info from receptors and transmitting this info to the CNS

Motor NS: responsible for transmitting motor impulses from the CNS to effectors (muscles or glands)

embryonic development of the human brain

a. neural tube (dorsal hollow nerve cord)

b. primary brain vesicles

• prosencephalon (forebrain)

• mesencephalon (midbrain)

• rhombencephalon (hindbrain)

c. secondary brain vesicles

• telencephalon

• diencephalon

• mesencephalon (middle)

• metencephalon

• myelencephalon

gray matter vs white matter

gray- contains neuron cell bodies, dendrites, and unmyelinated axons. fxns in processing and integration

white= composed of myelinated axons. fxns in transmitting signals between different parts of the CNS

gyri