anatomy exam 3

nervous system

• includes various organs

  • brain and spinal cord

  • receptors of sense organs (eyes, ears)

  • nerves that connect to other systems

nervous tissue

2 types of calls

• neurons: intercellular communication

• neyroglia/glial cells

  • for survival and function of neurons

  • preserve structure of nervous tissue

anatomical division of nervous system

central and peripheral

cns

• brain and spinal cord

• made of nervous tissue, connective tissue and blood vessels

• process and coordinate sensory data from inside and outside body

• motor commands skeletal muscles

• higher functions of brain, inteligence

pns

• somatic nervous system: sense organs and voluntary muscles

  • both voluntary and involuntary reflexes

  • controls skeletal muscles contract

• autonomic nervous system: comminicate w internal organs and glands

  • controls subconscious contracts of smooth and cardiac muscle and gland secreations

• delivers sensory info in cns

• cranial nerves connect to brain and spinal nerves connect to spinal cord

autonomic nervous system

sympathetic division: stimulate

parasymatheic division: relaxing

somatic nervous system/ pns

sensory, afferent nervous system= sensory input

• carries sensory info

• from receptors in peripheral tissues and organs to cns

motor, efferent system, sensoru output

• carries motor commands

• from cns to muscles, glands, adipose

enteric nervous system

neurons in digestive tract

• use same nt is brain

• iniates and coordinate reflexes, without instructions from cns

• can be influences by ans

neurons

basic functional units of nervous system

• send and receive signals

• lack centrioles, cannot divide, cannot be replaces after injury or disease

cell body/soma

• Large nucleus and nucleolus

• Perikaryon (cytoplasm)

• Mitochondria (produce energy)

• RER and ribosomes (synthesize proteins)

Cytoskeleton of perikaryon

– Neurofilaments and neurotubules

• Similar to intermediate filaments and microtubules

– Neurofibrils

• Bundles of neurofilaments that provide support for

dendrites and axon

nissl bodies

• dense area of rer and ribosomes in perikaryon

• make nervous tissue appear gray, gray matter

dendrites

– Short and highly branched processes extending from cell

body

– Dendritic spines

• Fine processes on dendrites

• Receive information from other neurons

• 80–90 percent of neuron surface area

axon

– Single, long cytoplasmic process

• Up to a meter in length

– Propagates electrical signals (action potentials)

– Axoplasm

• Cytoplasm of axon

• Contains neurofibrils, neurotubules, enzymes, and

organelles

initial segment

base of axon

axon hillock

thick region that attaches initial segment to cell body

collaterals

branches of axon

telodendria

Fine extensions of distal axon

Axon terminals (synaptic terminals)

• Tips of telodendria

• Play a role in communication with another cell

–synapse: neuron communicates with another

cell

axonal axoplasmic transport

• movement of materials btwn cell body and axon terminals

• materoa;s move along neurootubules w/in axon

• Powered by mitochondria, kinesin, and

  dynein (“molecular motor proteins”)

• Anterograde transport: kinesin

  – Forward flow: from cell body to

  axon

• Retrograde: dynein, backward flow from axon to cell body

rabies

axaxonic neurons

• no axons

• small

• All cell processes look similar

• Found in brain and special sense organs

bipolar neurons

• Small and rare

• One dendrite and one axon

• Found in special sense organs (sight, smell,

hearing)

Unipolar neurons (pseudounipolar neurons)

• Axon and dendrites are fused

• Cell body to one side

• Most sensory neurons of PNS

• Longest unipolar neurons

– Carry sensations from the tips of the toes to the

spinal cord

multipolar neurons

• Have one long axon and two or more dendrites

• Common in the CNS

• All motor neurons that control skeletal muscles

Functional classifications of neurons

– Sensory neurons

– Motor neurons

– Interneurons

sensory neurons (afferent neurons)

– Unipolar

– Cell bodies grouped in sensory ganglia

– Processes (afferent fibers) extend from sensory

receptors to CNS

Somatic sensory neurons

• Monitor external environment

Visceral sensory neurons

Monitor internal environment

Interoceptors

• Monitor internal systems(e.g., digestive, urinary)

• Internal senses (stretch, deep pressure, pain)

Exteroceptors

• Monitor external environment (e.g., temperature, skin)

• Complex senses (e.g., sight, smell, hearing)

Proprioceptors

Monitor position and movement of skeletal muscles and joints

2 types of motor neurons/efferent neurons

– Carry instructions from CNS to peripheral effectors

• Via efferent fibers (axons)

somatic and visceral

Somatic motor neurons of SNS

Innervate skeletal muscles

visceral motor neurons of ans

• Innervate all other peripheral effectors

• Smooth and cardiac muscle, glands, adipose

motor neurons

– Signals from CNS to visceral effectors cross autonomic

ganglia that divide axons into

• Preganglionic fibers

• Postganglionic fibers

interneurons

• most in brain and spinal cord

  • some in autonomic ganglia

• located between sensory and motor neurons

• responsible for distributing sensory info

• coordinate motor activoty

• higher functions

neuroglia

• support and protect neurons

  • provide support framework, suport and repair neurons in cns and pns

• makeup half the volume of nervous system

  • outnumber neurons

• cns has more variability

types of neuroglia in cns

– Astrocytes

– Ependymal cells

– Oligodendrocytes

– Microglia

types neuroglia in pns

satelite and schwann cells

astrocytes

• type of cns neuroglia

• large cell body

• maintain blood brain barrier

• – “Feet” of the astrocytes

  form a complete blanket

  around the capillaries

  • Create three-dimensional

  framework for CNS

  • Repair damaged nervous

  tissue

  • Guide neuron development

  • Control interstitial environment:

  ions;

ependymal cells

• form epitheliam that lines spinal cord and central canal and ventricle of brain

• produce and monitor cerebral spinal fluid

• have cilia that moves csf

oligodendrocytes

• have small cell bodies with few processes

• form myelin sheath

  • increase speed of action potential, makes nerve look white

demyelination

• lose myelin in pns and cns

diphtheria

• bacteria disease that damages schwann cells and destroys myelin sheath in pns

• fatal paralysis