Nervous System (Pt. 1)

Nervous system

Control and communication center of the body

How nervous system carries out function

variety of receptors to monitor changes (inside and outside the body)

Sensory input

Summation of information gathered by receptors

Integration

Body takes in information and decides what to do with it

Motor output

response determined by nervous system

Central Nervous System (CNS)

1. Command center of body

2. Spinal cord and brain

3. Lacks neurilemma

Peripheral Nervous System (PNS)

1. Nerves extending from CNS

2. Delivers information to CNS (Afferent nerves)

3. Carries instructions from CNS to motor component (Efferent nerves)

2 Classifications of nervous system

Structural, Functional

Structural classification

1. Contains ALL nervous system organs

2. Broken into CNS and PNS

Functional classification

Involves ONLY PNS,Breaks PNS into subdivisions

2 Subdivisions of PNS

1. Sensory

2. Motor

Sensory

1. Afferent (Arrives)

2. Carries impulses TO CNS from sensory organs

3. Keeps body informed on what is happening

Motor

Efferent (Exits), Carries impulse FROM CNS to body, Contains 2 subdivisions

2 Subdivisions of Motor

1. Somatic controls

2. Autonomic controls

Somatic controls

1. Skeletal muscle

2. AKA voluntary nervous system

Autonomic controls

1. Smooth muscle, cardiac muscle and glands

2. AKA involuntary nervous system

2 Main cells of nervous system

1. Supporting cells

2. Neurons

Support cells

1. AKA neuroglia or glia cells

2. Support, insulate and protect neurons

3. Each neuroglia has special function

4. Unable to transmit information

5. Retain ability to divide

4 Neuroglia cells

1. Astrocytes

2. Microglia

3. Ependymal cells

4. Oligodendrocytes

Astrocytes

Star shaped, Account for 1/2 of neural tissue, numerous projections connecting to neurons anchoring them to capillaries, Barrier between capillaries and neurons (assist permeability), assist taking in leaked potassium ions and neurotransmitters in the brain

Microglia

1. Spider-like cells

2. Phagocytic in nature

3. Function to dispose of debris (dead cells and bacteria in brain)

Ependymal

1. Line central cavity of brain and spinal cord

2. Beating of cilia attached helps circulate the CSF

Oligodendrocytes

Wrap flat extension around nerve fibers,Produce fat insulation coverings (AKA myelin sheaths)

2 types of PNS support cells

1. Schwann cells

2. Satellite cells

Schwann cells

Form myelin sheaths around nerve fibers in PNS

Satellite cells

Act as protective and cushioning cells

Neurons

1. Highly specialized cells

2. Transmit impulses from one part of the body to another

3. Differ structurally (many common features)

4. Loose ability to divide (reason for gliomas)

5. ALL have a cell body and one or more processing extending from body

Neuron cell body

Metabolic center, cytoplasm contain all expected organelles (except for centrioles), Rough ER AKA Nissl bodies

Neuron processes

1. Long extensions or fibers from cell body

2. Dendrites and Axons

Dendrite

1. Extensions transmitting information TO cell body

2. Can be hundreds

Axon

1. Transmit information FROM cell body

2. May only have one originating from axon hillock

3. Branch at terminal into hundreds and thousands ds of terminals

Axon terminal

1. Contain neurotransmitters

2. Separate from neuron by synaptic cleft

Myelin sheath

1. Insulates fibers

2. Increases transmission speed of nerve impulse

Neurilemma

1. Outermost layer of myelin sheath

2. Assists fiber regeneration

Nodes of ranvier

Gaps between individual cells of myelin sheath

3 Main types of nerve structure

1. Sensory (Afferent)

2. Motor (Efferent)

3. Association (Interneuron)

Association (Interneuron)

1. Connect sensory and motor neurons in neural pathway

2. Cell bodies found in CNS

5 Functional classifications of Neurons

1. Free nerve endings

2. Meissner's corpuscle

3. Lamellar corpuscle

4. Golgi tendon organ

5. Muscle spindle

Free nerve endings

Temperature and threat

Meissner's corpuscle

touch

Lamellar corpuscle

Deep touch

Golgi tendon organ

proprioceptor and tension

Muscle spindle

proprioceptor and stretch

3 structural classifications of neurons

1. Multipolar

2. Bipolar

3. Unipolar

Multipolar

1. Several projections

2. Most common

3. ALL motor neurons

Bipolar

Found in special sense organs (Optic, olfactory)

Unipolar

Sensory neurons in PNS ganglia