CHAPTER 10NERVOUS SYSTEM 1

CONTROLS WHAT WE DO AND DETERMINES WHO WE ARE

SENSE CHANGES IN HOMEOSTASIS , ANALYZE THE CHANGE AND INITIATE THE CORRECT RESPONSE

FUNCTION

NERVOUS TISSUE MOSTLY BLOOD VESSELS CONNECTIVE TISSUE

COMPOSISTION

NEURONS: NERVE CELLS NEUROGLIA

NERVOUS TISSUE TYPES

FUNCTIONS:◦ STIMULATED BY CHEMICAL OR PHYSICAL

CHANGES IN THE ENVIRONMENT PARTS:

◦ DENDRITES◦ CELL BODY/ SOMA◦ AXON◦ NERVE IMPULSE

**A NERVE IS A COLLECTION OF NEURONS

NEURONS

NEURON

http://vv.carleton.ca/~neil/neural/neuron-a.html

http://vv.carleton.ca/~neil/neural/neuron-a.html

SYNAPSE NEUROTRANSMITTERS

◦ CARRY IMPULSE ACROSS SYNAPSE

PARTS

CENTRAL NERVOUS SYSTEM: CNS◦ BRAIN◦ SPINAL CORD

PERIPHERAL NERVOUS SYSTEM: PNS◦ CRANIAL AND SPINAL NERVES◦ CONNNECTS CNS TO REST OF BODY◦ TWO PARTS:

SENSORY MOTOR: TWO PARTS

SOMATIC NERVOUS SYSTEM TO SKELETAL MUSCLES

AUTONOMIC NERVOUS SYSTEM TO SMOOTH AND CARDIAC MUSCLE AND GLANDS

ORGANS

RECEIVING INFORMATION: SENSORY◦ RECEPTORS ON ENDS OF THE PERIPHERAL NEURONS◦ STIMULATED BY (?) AND FORM IMPULSE OFTEN TO CNS

INTERPRETING INFORMATION: INTEGRATIVE◦ IMPULSES ARE ANALYZED AND CREATE SENSATIONS, FORM

MEMORIES, PRODUCE THOUGHTS; ◦ SUBCONCIOUS OR CONCIOUS DECISIONS MADE

REACTING TO INFORMATION: MOTOR◦ SUBCONCIOUS OR CONCIOUS DECISIONS ARE CARRIED OUT◦ EFFECTORS: MUSCLES AND GLANDS◦ SOMATIC NERVOUS SYSTEM: CONCIOUS; SKELETAL MUSCLES◦ AUTONOMIC NERVOUS SYSTEM: UNCONCIOUS; SMOOTH,

CARDIAC MUSCLE AND GLANDS

GENERAL FUNCTIONS

VARY IN SIZE AND SHAPE; SIZE AND LENGTH OF DENDRITES AND AXONS AND NUMBER OF PROCESSES

CELL BODY: CONTAINS◦ GRANULAR CYTOPLASM◦ MITOCHONDRIA◦ LYSOSOMES◦ GOLGI APPARATUS◦ MICROTUBULES◦ NEUROFIBRILS: EXTEND INTO AXON◦ NISSL BODIES: CHROMATOPHILIC SUBSTANCE: ROUGH ER (?)◦ INCLUSIONS◦ NUCLEUS WITH NUCLEOLUS

PARTS

NEUROFIBRILS

NEUROFIBRILSIN KITTEN NEURONS

http://www5.bartleby.com/107/illus629.html

NISSL BODIES

SMALL ARROWS

http://www.biomedcentral.com/content/figures/1471-2202-6-19-5-l.jpg

DENDRITES◦ USUALLY BRANCHED◦ DENDRITIC SPINES: CONTACT POINTS

AXON◦ AXONAL HILLOCK◦ CYTOPLASM:

MITOCHONDRIA; MICROTUBULES, NEUROFIBRILS◦ COLLATERALS◦ AXON TERMINALS WITH SYNAPTIC KNOB

DENDRITIC SPINES

http://www.udel.edu/biology/Wags/histopage/colorpage/cne/cne.htm

CARRIES MATERIAL MADE IN CELL BODY TO END OF AXON◦ VESICLES, MITOCHONDRIA, IONS, NUTRIENTS,

NEUROTRANSMITTERS

AXONAL TRANSPORT

http://www.lookfordiagnosis.com/mesh_info.php?term=axonal+transport&lang=1

SCHWANN CELLS

www.mc.vanderbilt.edu/histology/slide.php?image_name=myelin&slide_file=images/histology/nervous_tissue/display/schwann3.jpg&image_id=1058

MYELINATED NEURONS◦ HAVE SCHWANN CELLS (PNS) OR

OLIGODENDROCYTES (CNS)◦ WHITE MATTER◦ INCREASE SPEED OF TRANSMISSION

UNMYELINATED◦ NO MYELIN◦ GRAY MATTER

STRUCTURAL◦ MULTIPOLAR

MOST NEURONS WITH CELL BODIES IN CNS

◦ BIPOLAR SPECIALIZED STRUCTURES (EYES)

◦ UNIPOLAR SOME HAVE GANGLIA

CLASSIFICATION OF NEURONS

http://library.thinkquest.org/C0126536/main.php?currentchap=1&currentsect=neuron.htm

SENSORY NEURONS/ AFFERENT◦ TO CNS◦ SENSES/ RECEPTORS◦ MOST UNIPOLAR (SOME BIPOLAR)

INTERNEURONS/ASSOCIATION/ INTERNUNCIAL

◦ IN CNS◦ MULTIPOLAR◦ TRANSFER IMPULSES TO BE INTERPRETED

MOTOR NEURONS/ EFFERENT◦ MULTIPOLAR◦ FROM CNS TO EFFECTORS◦ SOME VOLUNTARY/ SOME INVOLUNTARY

FUNCTIONAL CLASSIFICATION

FUNCTION:◦ SCAFFOLDING; CONTROL SITES OF NEURONAL

CONTACT; EMBRYONIC: GUIDE DEVELOPMENT, PLACEMENT AND SPECIALIZATION OF NEURONS;

◦ PRODUCE GROWTH FACTORS THAT NOURISH NEURONS; REMOVE ACCUMULATING IONS AND NEUROTRANSMITTERS BETWEEN NEURONS; HELP FORMATION AND MAINTAINENCE OF SYNAPSES

NEUROGLIA

◦ ASTROCYTES STAR SHAPED LOCATED BETWEEN BLOOD VESSELS AND NEURONS SUPPOSRT NEURONS, AID METABOLISM OF

SUBSTANCES (GLUCOSE); REGULATE ION CONCENTRATIONS; FORM SCAR TISSUE; MOVEMENT OF SUBSTANCES FROM BLOOD; RELEASE GROWTH FACTORS; PART OF BLOOD BRAIN BARRIER;

GAP JUNCTIONS

CLASSIFICATION OF NEUROGLIACNS

http://medcell.med.yale.edu/systems_cell_biology/nervous/neuroglia.php

OLIGODENDROCYTES◦ SIMILAR SHAPE BUT SMALLER◦ FORM MYELIN BUT ONLY PROCESS WRAP AROUND

NEURONS SO COVER MANY CELLS BUT NO NEURILEMMA

MICROGLIA◦ SMALL WITH FEWER PROCESSES◦ THROUGH OUT CNS◦ PHAGOCYTIZE BACTERIA◦ PROLIFERATE WHEN INJURY OCCURS

EPENDYMA◦ CUBOIDAL, COLUMNAR MAY BE CILIATED◦ FORM INNER LINING OF CENTRAL CANAL OF SPINAL

CORD AND VENTRICLES AND CHOROID PLEXUSES◦ GAP JUNCTIONS: ALLOWING MOVEMENT BETWEEN

CEREBROSPINAL FLIUD AND INTERSTITIAL FLUID OF BRAIN

http://www.google.com/imgres?q=satellite+cells+pns+function&hl

BRAIN TUMORS ALS HUNTINGTON’S DISEASES

ABNORMAL NEUROGLIA

SCWHANN CELLS SATELLITE CELLS

◦ SUPPORT GANGLIA NOT SURE OF S[PECIFIC FUNCTION

◦ FORM AN ENVELOPE AROUND EACH CELL BODY IN GANGLIA

PNS

A: Satellite cellsB: Schwann cells

http://www.google.com/imgres?q=satellite+cells+pns+function&hl=en&sa

INJURY TO CELL BODY = DEATH; NOT REPLACED UNLESS A STEM CELL IS STIMULATED

PNS: AXON MAY REGENERATE:◦ INJURY:

DISTAL PORTION DIES MACROPHAGES REMOVE DEBRIES PROXIMAL END DEVELOPS SPROUTS NEUROGLIA RELEASE GROWTH FACTORS WHICH

STIMULATE ONE SPROUT TO GROW INTO A TUBE FORMED BY BASEMENT MEMBRANE AND CONNECTIVE TISSUE

SCHWANN CELLS PROLIFERATE FORMING NEW MYELIN GROWS 3-4MM/DAY; MAY NOT GROW TO PROPER

POSITION

NEURON REPAIR

CNS:◦ INJURY:

DISTAL PORTION DIES SLOWLY OLIGODENDROCYTES DON’T FORM A NEURILEMMAE

AND DON’T PROLIFERATE SO SPROUT USUALLY ISN’T DIRECTED TO GROW PROPERLY

NEURON REPAIR

physproject-2011.wikispaces.com

PRESYNAPTIC NEURON STIMULATES OR INHIBITS THE POST SYNAPTIC NEURON

IMPULSE REACHES THE AXON TERMINAL AND THE CHANGE IN THE MEMBRANE OPENS THE CALCIUM CHANNELS AND CALCIUM DIFFUSES IN

CAUSING THE SYNAPTIC VESSICLES TO FUSE WITH THE CELL MEMBRANE AND RELEASE THE NEUROTRANSMITTERS BY EXOCYTOSIS

THE NEUROTRANSMITTER ATTACHES TO A RECEPTOR ON THE POST SYNAPTIC NEURON AND STIMULATES OR INHIBITS THE NEURON

THE EFFECT DEPENDS ON THE INPUT FROM 1 TO 100,000+ PRESYNAPTIC NEURONS AND THEIR INPUT

SYNAPTIC TRANSMISSION

http://www.ucl.ac.uk/~sjjgsca/NerveSynapse.html

http://scienceaid.co.uk/biology/humans/nerves.html

USUALLY POLARIZED: THE INSIDE IS MORE NEGATIVE THAN THE OUTSIDE BECAUSE OF THE SODIUM/POTASSIUM PUMP AND THE GATED CHANNELS ARE NOT OPEN

THE MEMBRANE IS MORE PERMEABLE TO POTASSIUM THAN SODIUM, SO POTASSIUM DIFFUSES OUT MORE READILY THAN SODIUM DIFFUSES IN

THERE ARE CELL FORMED ANIONS (PHOSPHATE, SULFATE AND PROTEINS) THAT CAN NOT DIFFUSE OUT OF THE CELL

SO THE OUTSIDE IS MORE POSITIVE AND THE INSIDE IS MORE NEGATIVE

THIS DIFFERENCE IS MEASURED IN MILLIVOLTS; THIS RESTING POTENTIAL IS -70 MILLIVOLTS

THIS NEGATIVE POTENTIAL ALLOWS SODIUM TO DIFFUSE INTO THE CELL BUT INHIBITS THE DIFFUSION OF POTASSIUM OUT OF THE CELL (ABOUT 3Na TO 2 K) WHICH THE PUMP REPLACES (3Na OUT TO 2 K IN)

RESTING CELL MEMBRANE POTENTIAL

http://tle.westone.wa.gov.au/content/items/969144ed-0d3b-fa04-2e88-8b23de2a630c/1/human_bio_science_3b.zip/content/002_nervous_control/media/cc2_g015a.gif

NEURONS ARE HIGHLY EXCITABLE: RESPOND TO CHANGES

USUALLY OPENS A GATED ION CHANNEL◦ IF INSIDE BECOMES MORE NEGATIVE=

HYPERPOLARIZED◦ IF INSIDE IS LESS NEGATIVE= DEPOLARIZED

CHANGES ARE GRADED= GREATER THE STIMULATION/ GREATER THE HYPERPOLARIZATION OR DEPOLARIZATION

IF DEPOLARIZATION REACHES -55MILLIVOLTS = THRESHOLD STIMULATION AND STARTS AN ACTION POTENTIAL= IMPULSE

LOCAL MEMBRANE POTENTIAL CHANGES

HYPERPOLARIZATION

http://www.jci.org/articles/view/29063/figure/2

DEPOLARIZATION

AT AXONAL HILLOCK MEMBRANE IS MOST LIKELY TO BE STIMULATED TO THRESHOLD = TRIGGER ZONE, CONTAINS LOTS OF VOLTAGE-GATED SODIUM CHANNELS

WHEN THRESHOLD IS REACHED THE CHANNELS OPEN AND Na DIFFUSES IN CHANGING POTENTIAL TO +30mV

Na CHANNELS CLOSE AND K CHANNELS OPEN AND K DIFFUSES OUT MAKING INSIDE NEGATIVE AGAIN= REPOLARIZATION

K CHANNELS CLOSE AND RESTING POTENTIAL IS REFORMED ACTION POTENTIAL AT TRIGGER ZONE CUSES AN ELECTRICAL

STIMULTION A SHORT DISTANCE ON THE MEMBRANE CAUSING ANOTHER ACTION POTENTIAL AND SO FORTH ALONG THE WHOLE AXON = IMPULSE

SODIUM IS PUMPED OUT, POTASSIUM IS PUMPED IN RESTORING THE RESTING POTENTIAL

ACTION POTENTIAL/IMPULSE

http://web.lemoyne.edu/~hevern/psy340_10S/graphics/action_potential.jpg

http://www.google.com/imgres?imgurl=http://www.millerandlevine.com/chapter/35/figure35-7.jpg&imgrefurl=http://

http://www.youtube.com/watch?feature=endscreen&v=7EyhsOewnH4&NR=1

http://www.youtube.com/watch?v=9euDb4TN3b0

http://www.youtube.com/watch?feature=endscreen&v=7EyhsOewnH4&NR=1

http://www.youtube.com/watch?NR=1&v=rWrnz-CiM7A&feature=fvwp

HOW THE IMPUPLSE FORMS AND TRAVELS

IF THRESHOLD IS REACHED THE AXON RESPONDS COMPLETELY

A GREATER STIMULUS RESULTS IN MORE IMPULSES PER SECOND NOT A STRONGER IMPULSE

ALL OR NONE

ABSOLUTE◦ 1/2500 OF A SECOND◦ SODIUM PERMEABILITY ◦ IS CHANGING/ CAN’T ◦ RESPOND

RELATIVE ◦ CLOSE TO RESTING POTENTIAL◦ RESPONDS TO A STRONGER STIMULUSTAKES 10-30 MILLISECONDSCOULD HAVE UP TO 700 IMPULSES PER SECOND

BUT USUALLY ONLY ABOUT 100

REFRACTORY PERIOD

http://scienceaid.co.uk/biology/humans/nerves.html

MYELINATED NEURON: ◦ SALTATORY CONDUCTION◦ FASTER

UNMYELINATED◦ WHOLE AXON: SLOWER

LARGE AXON DIAMETER◦ FASTER

SMALL DIAMETER◦ SLOWER

THICK MYELINATED:◦ 120 M/S

THIN UNMYELINATED:◦ .5 M/S

IMPULSE CONDUCTION

NEUROTRANSMITTERS OPEN OR CLOSE CHEMICALLY-GATED CHANNELS WHEN ATTACH TO RECEPTORS

LOCAL POTENTIALS = SYNAPTIC POTENTIALS EXCITATORY POSTSYNAPTIC POTENTIAL

◦ OPENS SODIUM CHANNELS = DEPOLARIZES◦ 15 MILLISECONDS

INHIBITORY POSTSYNAPTIC POTENTIAL◦ OPENS POTASSIUM OR CHLORIDE CHANNELS =

HYPERPOLARIZED INTEGRATED SUM OF EPSPS AND IPSPS DETERMINES

RESPONSE THE TRIGGER ZONE OR IN SOME THE DISTAL

PERIPHERAL PROCESS IS MOST SENSITIVE SO THE DECISION-MAKING PART

SYNAPTIC POTENTIALS

30 – 50; FINDING NEW ONES SOME NEURONS RELEASE ONLY 1; SOME 2 OR MORE TYPES:

◦ Ach SKELETAL MUSCLES

◦ MONOAMINES/BIOGENIC AMINES/MODIFIED AMINO ACIDS NOREPINEPHRINE; DOPAMINE; SROTONIN; HISTAMINE

◦ UNMODIFIED AMINO ACIDS GLYCINE; ASPARTIC ACID; GABA; GLUTAMATE

◦ NEUROPEPTIDES ENKEPHALIN; ENDORPHIN; SUBSTANCE P

◦ GASES NITRIC OXIDE

NEUROTRANSMITTERS

PEPTIDES:◦ ROUGH ER OF CELL BODY AND TRANSPORTED TO

AXON TERMINAL OTHERS

◦ FORMED IN CYTOPLASM OF TERMINALS AND PACKAGED

THE MORE CALCIUM THAT ENTERS THE MORE NEUROTRANSMITTERS RELEASED

NEUROTRANSMITTER PRODUCTION

VESSICLE BECOMES PART OF CELL MEMBRANE

MATERIAL CAN BE RETURNED TO CYTOPLASM AND USED TO FORM NEW VESSICLES

VESSICLE TRAFFICKING

NEUROPEPTIDES THAT MODIFY A NEURON’S RESPONSE TO NEUROTRANSMITTERS OR INHIBITSTHE RELEASE OF NEUROTRANSMITTERS◦ ENKEPHALINS: INCREASE DURING STRESS, BIND

TO OPIATE RECEPTORS, RELIEVE PAIN◦ BETA ENDORPHIN: SAME AS ENKEPHALIN BUT

ACTS LONGER AND IS MORE POTENT◦ SUBSTANCE P: IN NEURONS THAT TRANSMIT PAIN

IMPULSES◦ ENKEPHALIN AND BETA ENDORPHIN MAY INHIBIT

SUBSTANCE P

NEUROMODULATORS

ENZYMES IN SYNAPSE AND POSTSYNAPTIC MEMBRANES DECOMPOSE SOME NEUROTRANSMITTERS (ACETYLCHOLINESTERASE)

REUPTAKE: PICKED UP BY PRE OR POSTSYNAPTIC NEURONS, OTHER NEURONS OR GLIAL CELLS

SIGNAL DURATION

NEURONAL POOLS:◦ GROUPS OF INTERNEURONS WITH A COMMON

FUNCTION◦ RECEIVE INPUT FORM OTHER NEURONS AND

SEND OUTPUT◦ EXCITATORY OR INHIBITORYFACILITATION:

STIMULATION THAT DOESN’T REACH THRESHOLD BUT MAKES IT EASIER FOR ANOTHER STIMULUS TO REACH THRESHOLD

IMPULSE PROCESSING

RECEIVING IMPULSES FROM TWO OR MORE NEURONS

CAN SUM IMPULSES FROM DIFFERENT SOURCES

CONVERGENCE

GOING FROM A NEURON OR POOL AND REACHING TWO OR MORE DIFFERENT NEURONS

CAN CAUSE AMPLIFICATION ALSO IMPULSE COULD GO FROM ONE

SENSORY NEURON TO TWO OR MORE DIFFERENT PLACES IN CNS

DIVERGENCE