BIO21011

I.Nervous Tissue

A.functions

1.senses changes in environment

a.stimuli

b.sensory input

c. receptors, sensory nerves

2.processes sensory input

a.integration - brain

3.response elicited

a.motor output

b. motor nerves

c. effector

B.organization

1.CNS

a.brain

b.spinal cord

2.PNS

a.nerves

(1)spinal nerves

(2)cranial nerves

b. afferent branch

(1)sensory

(2)goes to CNS

c.efferent branch

(1)motor fibers

(2)from CNS to

(a)somatic nervous system

i)voluntary skeletal muscle control

(b)autonomic nervous system (ANS)

i)smooth muscle

ii)cardiac muscle

iii)glands - regulate secretions

iv)divided into branches

a)sympathetic

b)parasympathetic

(c)enteric nervous system (ENS)

i)involuntary to gut

ii)effectors-sm m, glands, endocrine cells of GI

C.Histology

1. Cells

a.Neurons

i).excitable cells

ii).conduct nervous impulse

iii).do not undergo mitosis (amitotic)

iv) life span (100 yrs)

v).high metabolic activity

(1)need glucose and oxygen

(2)die within a few minutes if oxygen absent

b. neuroglial cells (glia)

i)supporting cells

ii) ‘glue’ and assist neurons

2. Neuron.structure

a.cell body (soma)

b.nucleus

(1)nucleolus

c.mitochondria

d.no centrioles

e.Nissl bodies (RER)

f.dendrites

(1)receptive area

g.axon hillock

(1)where axon leaves cell body

h.axon

(1)conduction component

i.axon terminal

(1)secretory for neurotransmitters

(2)synapse

j.Schwann cell

(1)encircles axon

(2)myelin sheath

k.neurolemma

(1)sheath of Schwann cell

l.node of Ranvier

(1)junction between adjacent Schwann cells

3, arrangement of neurons

a. Cell processes (dendrites/axons)

i).CNS = tract

ii).PNS = nerve

b.Cell bodies

i).CNS = nuclei

ii).PNS = ganglia

c.long axon = nerve fiber

i).larger diameter = conducts faster

d.Myelin sheath

i).fatty white material

ii).covering of axon

iii).insulation

iv).permits faster transduction of impulse

e.White matter = myelinated fibers in CNS

f.gray matter = cell bodies and unmyelinated fibers

4.Neuroglia in CNS

(1)astrocytes

(a)barrier between neurons and capillaries, maintain chemical environment

(2)microglia

(a)macrophages to engulf microbes

or dead tissue

(3)ependymal

(a)line central cavities

(b)cilia beat to circulate fluid

(4)oligodendrocytes

(a)few branches

(b)forms myelin in CNS

a.supporting cells in PNS

(1)Schwann cells

(a)myelin

(2)satellite

(a)control chemical environment

D.Structural classification of neurons

1.multipolar (most)

2.bipolar

3.unipolar

E.functional classification of neurons

1.afferent

2.efferent

3.interneurons

b.between afferent and efferent in a complex pathway

c.most are in CNS for integration

c. also called association neurons

II.Neurophysiology

A.ion flux

1.mV potential across membrane = electrical signal

a.due to ions

b.resting membrane potential (-60mV)

c.depolarize - Na moves in

d.repolarize - K moves out and inside becomes -

2.voltage gated channels

3.chemical gated channels

B.Na/K ATP ase

1.takes 3 sodiums out

2.takes 2 potassiums in

3.maintains resting membrane potential

4.stimulus opens channels so that sodium rushes in and depolarization occurs

C.hyperpolarize

1.make resting membrane potential more negative

2.do not get signal to cross

D.conduction of impulse

1.threshold , all or none

2.stimulus signal is graded

a.dendrite/cell body receives signal

b.if it is threshold it will become action potential at the axon hillock and be propagated down the axon

c.depolarization

d.repolarization

e.Na/K ATPase restores ion balance

3.refractory period

E.Conduction Velocities

1.axon diameter

a.faster conduction with thick axon

2.myelin sheath

a.insulates, makes thicker to conduct faster

b.signal can jump an nodes of Ranvier to speed up conduction = Saltatory conduction

c.Multiple sclerosis

(3)loss of myelin sheath - slow impulse conduction

F.Synapse

1.electrical

a.flow of ions

2.chemical

a.neurotransmitter released

b.EPSP

(1)excitatory post-synaptic potential

(2)depolarization at cell after synapse

(3)action

(b)ionotropic- opens ion channels

(c)metabotropic-2nd messenger cascade c.IPSP

(4)inhibitory post synaptic potential

(5)hyperpolarization of cell after synapse

(6)inhibitory neurotransmitter

G..Neurotransmitters

1. chemicals made in neuron and stored/released at axon terminal

a.behavior,mood modified by NT release

b.drugs can alter NT binding

2. removal of neurotransmitter

a. enzyme

b. reuptake

3. Made from amino acids, modified amino acids (biogenic amines) other type compounds

a. examples

(1)acetylcholine

(a)excitatory on skeletal muscle

(2)norepinephrine

(a)excitatory or inhibitory depends on receptors

(b)in sympathetic nervous system

(3)dopamine

(a)generally excitatory

(b)feeling good NT

(c)uptake blocked by cocaine

(d)release enhanced by amphetamines

(4)serotonin

(a)generally inhibitory

(b)plays role in sleep,mood,appetite

(5)endorphins

(a)inhibitory

(b)inhibit pain

(c)iffet micked by morphine, heroin

(6)glutamate

(7)glycine

(8) NO

II.Neural Circuits

A.neurons organized into neuronal pools

B.input fiber synapses onto many neurons in a pool

C.circuits are arrangements of neurons within a pool

D.many diverge to multiple or the same pathway

E.may have converging of input signals to one or many outputs

F.processing may be

1.serial all or none

a.predictable

b.example = reflexes

2.parallel

a.input separated into many pathways

b.example hear a song

(1)process to recognize song

(2)determine if you like or dislike

(3)associate with an experience