

CONTROLS WHAT WE DO AND DETERMINES
WHO WE ARE
SENSE CHANGES IN HOMEOSTASIS , ANALYZE
THE CHANGE AND INITIATE THE CORRECT
RESPONSE



NERVOUS TISSUE MOSTLY
BLOOD VESSELS
CONNECTIVE TISSUE


NEURONS: NERVE CELLS
NEUROGLIA

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
http://vv.carleton.ca/~neil/neural/neu
ron-a.html
http://vv.carleton.ca/~neil/neural/neuron-a.html


SYNAPSE
NEUROTRANSMITTERS
◦ CARRY IMPULSE ACROSS SYNAPSE

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

RECEIVING INFORMATION: SENSORY

INTERPRETING INFORMATION: INTEGRATIVE

REACTING TO INFORMATION: MOTOR
◦ RECEPTORS ON ENDS OF THE PERIPHERAL NEURONS
◦ STIMULATED BY (?) AND FORM IMPULSE OFTEN TO CNS
◦ IMPULSES ARE ANALYZED AND CREATE SENSATIONS,
FORM MEMORIES, PRODUCE THOUGHTS;
◦ SUBCONCIOUS OR CONCIOUS DECISIONS MADE
◦ 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


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
◦
◦
◦
◦
◦
◦
◦
NEUROFIBRILS
IN KITTEN
NEURONS
http://www5.bartleby.com/107/illus629.html
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
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
http://www.lookfordiagnosis.com/mesh_info.php?term=axonal+transport&lang=1
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
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

MOTOR NEURONS/ EFFERENT

◦ IN CNS
◦ MULTIPOLAR
◦ TRANSFER IMPULSES TO BE INTERPRETED
◦ MULTIPOLAR
◦ FROM CNS TO EFFECTORS
◦ SOME VOLUNTARY/ SOME INVOLUNTARY

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
◦ 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
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


SCWHANN CELLS
SATELLITE CELLS
◦ SUPPORT GANGLIA NOT SURE OF S[PECIFIC
FUNCTION
◦ FORM AN ENVELOPE AROUND EACH CELL BODY IN
GANGLIA
A: Satellite cells
B: 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





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
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
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)
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
http://www.jci.org/articles/view/29063/figure/2






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
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?v=9euDb4T
N3b0
http://www.youtube.com/watch?feature=end
screen&v=7EyhsOewnH4&NR=1
http://www.youtube.com/watch?NR=1&v=rW
rnz-CiM7A&feature=fvwp
http://www.youtube.com/watch?feature=endscreen&v=7EyhsOewnH4&NR


IF THRESHOLD IS REACHED THE AXON
RESPONDS COMPLETELY
A GREATER STIMULUS RESULTS IN MORE
IMPULSES PER SECOND NOT A STRONGER
IMPULSE

ABSOLUTE
◦
◦
◦
◦

1/2500 OF A SECOND
SODIUM PERMEABILITY
IS CHANGING/ CAN’T
RESPOND
RELATIVE
http://scienceaid.co.uk/biology/humans/nerves.html
◦ CLOSE TO RESTING POTENTIAL
◦ RESPONDS TO A STRONGER STIMULUS
TAKES 10-30 MILLISECONDS
COULD HAVE UP TO 700 IMPULSES PER SECOND BUT
USUALLY ONLY ABOUT 100

MYELINATED NEURON:

UNMYELINATED

LARGE AXON DIAMETER

SMALL DIAMETER

THICK MYELINATED:

THIN UNMYELINATED:
◦ SALTATORY CONDUCTION
◦ FASTER
◦ WHOLE AXON: SLOWER
◦ FASTER
◦ SLOWER
◦ 120 M/S
◦ .5 M/S

NEUROTRANSMITTERS OPEN OR CLOSE CHEMICALLYGATED CHANNELS WHEN ATTACH TO RECEPTORS
LOCAL POTENTIALS = SYNAPTIC POTENTIALS
EXCITATORY POSTSYNAPTIC POTENTIAL

INHIBITORY POSTSYNAPTIC POTENTIAL




◦ OPENS SODIUM CHANNELS = DEPOLARIZES
◦ 15 MILLISECONDS
◦ 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



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

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


VESSICLE BECOMES PART OF CELL MEMBRANE
MATERIAL CAN BE RETURNED TO CYTOPLASM
AND USED TO FORM NEW VESSICLES

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


ENZYMES IN SYNAPSE AND POSTSYNAPTIC
MEMBRANES DECOMPOSE SOME
NEUROTRANSMITTERS
(ACETYLCHOLINESTERASE)
REUPTAKE: PICKED UP BY PRE OR
POSTSYNAPTIC NEURONS, OTHER NEURONS
OR GLIAL CELLS

NEURONAL POOLS:
◦ GROUPS OF INTERNEURONS WITH A COMMON
FUNCTION
◦ RECEIVE INPUT FORM OTHER NEURONS AND SEND
OUTPUT
◦ EXCITATORY OR INHIBITORY
FACILITATION:
STIMULATION THAT DOESN’T REACH THRESHOLD
BUT MAKES IT EASIER FOR ANOTHER STIMULUS TO
REACH THRESHOLD


RECEIVING IMPULSES FROM TWO OR MORE
NEURONS
CAN SUM IMPULSES FROM DIFFERENT
SOURCES



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