Anatomy chap. 13 nervous system

• Central nervous system
• Peripheral nervous system

Dorsal body cavity

• Integration, processing,
• Interperts incoming sensory information
• Directs motor responses (both visceral
• & organs)
• Seat of higher functions
• Intelligence, memory, learning
• Emotion

As a mass of neural tissue organizing into hollow tubes

All neural tissue outside the CNS

• Communication link with the CNS
• Provides sensory input
• Carries motor output

Nerves extend to/from brain & spinal cord

To & from brain

To & from the spinal cord

• Afferent
• Efferent

Functional divisons

Begins at receptors

Begins inside the CNS

Toward

Exiting

Brings information to the CNS

Carry motor commands from the CNS to the body

Sensory nerves

Motor nerves

• Muscle cell
• Gland cell

Perform specific functions

• May be a dendrite, specialized cell or cluster of cells
• Or a complex sense organ

Somatic & visceral

• Skeletal muscles, joints & the skin
• Voluntary of Involuntary

• Smooth muscle, cardiac muscle, glands
• Ventral body cavity system
• ANS outside awareness of control
• Homeostasis

• Nervous tissue
• Neurons
• Neuroglia

• Specialized for the conduction of electrical impluses from one
• Region of the body to another sends signals that are
• Rapid, specific and usually cause immediate response

• Cell body
• Or Soma

• Usually has several branching dendrites, is attached to an
• Elongated axon that ends at one or more synaptic terminal

• Organelles responsible for energy production & biosynthesis
• Of organic molecules such as enzymes

Transfer & process information

Transmit the electrical impulse along their cell membrane

• Excitable cells
• Highly specialized

• Neurons
• 1 meter

• It cannot divide or repair
• Lacks centrioles and centrosomes

• Glue
• Supporting

• Astrocytes
• Oligodendrocytes

• Supporting framework for neural tissue
• Provides nutrients to neurons
• Isolate and protect neurons

5 times as many as neurons

Can divide and repair

4 types

2 types

Glial cells

Because of the chemical synapse

Star cells

• Shield neurons from direct contact with other neurons & fluid
• Maintain blood-brain barrier
• Structural repairs
• Absorbs and recycles neurotransmitters

Process of the astrocyte.

Contacts the surface & covers most of the surface of capillaries within the CNS

A large number of cytoplasmic processes

• By facilitating the exchange of ions and
• Other molecules within the extracellular fluid
• Within the CNS

Packed with microfilaments that extend across the breadth of the cell.

By forming a structural framework

Chemical secretions of the astrocyte

• Secreted astrocyte chemicals involved in directing growth &
• Interconnection of developing neurons

Few

Myelinate CNS axons

Myelin helps prevent the electrical current from leaving the axon

Large area wrapped in myelin

• Gaps between the myelin sheaths
• Produced by adjacent oligodendrocytes

Nodes of Ravier

• Regions dominated by myelinated axons of the CNS
• Lipids

• Regions dominated by neuron cell bodies, dendrites, & unmyelinated axons
• Ribosomes

Phagocytic cells

Microglial

Smallest glial cells, posess slender cytoplasmic processes with many fine branches

Appear early in embroynic development through the division of mesodermal stem cells

• Cubodial to columnar in form. Unlike typical epithelial cell axon
• They have a slender process that branch extensively, making direct
• Contact with glial cells in surrounding neural tissue

A thin epithelial membrane(made up of ependymal cells) that lines ventricles or the brain, central canal of the spinal cord. A type of neuroglial

Circulation of the cerebrospinal fluid

Cerebrospinal fluid

Outside brian and spinal cord

Ganglia

They surround neuron cell bodies within ganglia

• Insulate the neuron from other stimuli
• Regulate the exchange of nutrients & wastes with extracellular fluid

Schwann cell

Regrowth of damaged axons

The superficial cytoplasmic covering of schwann cells

• Organelles that provide energy and perform biosynthetic activities.
• Neurons, mitochondria, free & fixed ribosomes & membranes of the
• Rough endoplasmic reticulum

The axon hillock

Centrioles

An inability to divide

Bundles of neurofilaments. Cytoskeleton elements that extend into the dendrites and axon

Neurofilaments & neurotubules

Ribosomal clusters

Chromatophilic substance

• At the axon when it is exposed to appropiate stimuli, producing a localized change in the
• Transmembrane potential

A property resulting from the equal distribution of ions across the neurilemma

A long cytoplasmic process capable of propagating an action potential

A special region in the multipolar neuron that connects the initial segments of the axon to the soma

Cytoplasm of the axon

• Neurofibrils, neurotubules, numerous small vesicles, lysosomes, mitochondria and various
• Enzymes

Collaterals

• Telo=end
• dendria=tree

• The main trunk & the collateral end
• In a series of fine terminal extentions

At the synaptic terminal

• Where the neuron contacts another neuron or effector
• Part of the synapse

Movement of organelles, nutrients, synthesized molecules & waste products between the cell body and synaptic terminals. Complex process. Consumes energy & relies on movement along the neurofibrils of the axon and it's branches

Specialized site where the neuron comminicates with another cell

Where one neuron synapses on another

Synaptic knob

To limit the number & type of stimuli

• Anaxonic
• Bipolar
• Pseudounipolar
• Multipolar

• Small, cannot distinguish from dendrites
• Only found in CNS and in special sense organs

A number of fine dendrites that fuse to form a single dendrite. Cell body lies between this dendrite & a single axon. Relatively rare

• Relaying sensory information concerning sight, smell, & hearing
• Axons are not myelinated

• Continious dendrite & axonal processes & cell body lies off to one side. The initial segment lies at the base of the dendrite branches. May be myelinated
• Usually sensory neurons

Multipolar

All motor neurons that control skeletal muscles. Myelinated axons. Several dendrites & a single axon that may have one or more branches.

Axons extending from the CNS to a ganglion

Axons connecting the ganglion cells with the peripheral effectors

Axons of sensory neurons. Extend between sensory receptor and the spinal cord or brain

• Exteroceptors
• Proprioceptors
• Interoceptors

• Sensory (PNS)
• Interneurons (CNS)
• Motor (PNS)

Transmits impulses from sensory receptors to CNS using afferent fibers

• Somatic
• Visceral

• Information about the outside world and our position in it
• Consciously controlled

Muscles, joints, skin, sense organs

Information on internal conditions & status of other organs

Smooth muscle, cardiac muscle, organs, glands

• Analysis of sensory inputs & coordination or motor outputs
• Within the CNS
• May be between the sensory & motor neurons

Interneurons

Multipolar

The greater the number of interneurons involved

Carry impulses away from the CNS to stimulate or modify the activity of a peripheral tissue or organ

Efferent fibers

Innervate skeletal muscles consciously controlled

• Autonomic(ANS)
• Effects organs, tissues, other muscles
• Little conscious control

• The presences or absence of a myelin sheath
• The diameter of the axon

Ion movement

After the plasmalemma is stimulated to a level known as threshold. Once threshold has been reached, the membrane permability to sodium & potassium ions changes

Ability of cell membrane (plasmalemma) to conduct electrical impulses

Propagation of action potentials

Chemical synapse

Ach

Neuroeffector junction where axon interacts with another neuron, muscle or gland

• Action potential arrives at end of presynaptic axon
• Synaptic vesicles release neurotransmitter
• Neurotransmitter diffuses across synaptic cleft
• Neurotransmitters bind to postsynaptic membrane receptors
• Effects channels in postsynaptic membrane (close or open)
• Result=stimulation or inhibition
• Neurotransmitters are broken down by enzymes or transported back into presynaptic terminal.

Gap junctions between the CNS & PNS neurons

Only one way from presynaptic to postsynaptic

Can convey nerve impulses in either direction

• Organized interneurons into smaller numbers
• Group of neurons with specific functions
• Defined by function soley

Over 50