Chapter 14 SG

Central nervous system (CNS)

includes brain and spinal cord

Peripheral Nervous System (PNS)

includes central nerves, spinal nerves, ganglia

Three functions of Nervous system

1. Collect information

2. Process and evaluate information

3. Initiate response

Organization of nervous system (CNS) & (PNS)

Two organizations of PNS:

1. Sensory (afferent) neurons: receives info then sends to CNS

2. Motor (efferent) neurons: Sends impulses from CNS to muscles and glands

** Both have parts in somatic and autonomic systems

Sensory (afferent) neurons subdivided in two:

1. Somatic sensory: conscious (general senses)- Somatic

2. Visceral sensory: not conscious (impulse of blood and viscera)- autonomic

Motor (efferent) neurons subdivided in two:

1. Somatic motor (SNS): voluntary (contraction of skeletal muscles) - somatic

2. Autonomic motor (ANS): involuntary (regulates smooth M, cardiac M, glands) - autonomic

Classifications of Neurons

-Excitable

-Conductive

-Secretory

-Long-Lived

-Amitotic

-Highly Metabolic

Structure of Neurons

-Cell body

-Dendrites

-Axon- axon hillock, synaptic knob

Three functional classes of neurons:

1. Sensory (afferent) neurons

2. Interneurons (in between communication)

3. Motor (efferent) neurons

Four types of Glial cells in (CNS):

1. Astrocytes

2. Obligodendrocytes

3. Microglial

4. Ependymal

Astrocytes characteristics

-Most abundant in CNS

-Helps form BBB-perivascular feet

Ependymal characteristics

-Ciliated cuboidal epi. cells that line ventricles of brain, central central canal of spinal cord

-Helps produce CFS (CNS)

Microglial characteristics

- Removes debris and dead or damage tissue (CNS)

Oligodendrocytes characteristics

-ONLY in CNS

-Is myelin sheets around axons (short portions)

Two type of glial cells in (PNS):

-Satellite

- Neurolemmocytes (Schwann cells)

Satellite characteristics

-Regulate fluid around neuron cell body in (PNS)

Neurolemmocytes (schwann) characteristics

-Helps with axon regeneration

-Is myelin sheets around axon in (PNS) (outside layer-Neurilemma)

Nerves connective tissue wrapping (three types)

1. Endoneurium- areolar around each axon

2. Perineurium- dense irregular around each fascicle

3. Epineurium- dense irregular around entire nerve

What is a Synapses?

Is a junction between two neurons, between a neuron and muscle or gland

Characteristic of a synaptic between two neurons

-Presynaptic neuron: has synaptic knobs

-Synaptic cleft: that narrow space

-Postsynaptic neuron: receives signals

Synpatic Communication (two)

1. Electrical Synapses: involves gap junctions, rapid ion flow, rare in nervous system

2. Chemical synapses: involves release of neurotransmitter like (Acetylcholine), (review system w/ synaptic knob)

Neural Circuites (grouped neurons)

-Converging

-Diverging

-Reverberating

-Parallel after discharge

Converging (Grouped neurons)

Impulses come together to a single postsynaptic neuron

Diverging (Grouped neurons)

Impulses spread from one presynaptic neuron to many postsynaptic neurons

Reverberating (Grouped neurons)

Cyclical stimulation of the circuit

Parallel after discharge (Grouped neurons)

Several neurons process the information simultaneously (in parallel)