Neuro Transmit Tter

8/2/2019 Neuro Transmit Tter

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Central Nervous System (CNS)

Brain Spinal Cord

Peripheral Nervous System (PNS)

Sensory NeuronsMotor Neurons

Somatic Nervous System

voluntary movements viaskeletal muscles

Autonomic Nervous System organs, smooth muscles

Sympathetic

- Fight-or-Flight responsesParasympathetic

- maintenance

THE NERVOUS SYSTEM

The Nervous System


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DIVISIONSOFTHEAUTONOMICNERVOUSSYSTEM


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2 main kinds of cells Neurons

Glial cells

100 billion neurons

10x more glial cells

Glial cells Support neurons (literally, provide physical support,

as well as nutrients) Cover neurons with myelin

Clean up debris

Housewives


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Basic units of the nervous system Receive, integrate and transmit

information

Operate through electrical impulses

Communicate with other neurons

through chemical signals.


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Sensory Neurons

Interneurons: Connects sensory and motor neurons

Motor Neurons


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Sensory (Afferent) vs. Motor (Efferent)

e.g., skin

e.g., muscle

Grays Anatomy 381999

sensory (afferent) nerve

motor (efferent) nerve

Neurons that send signals from the senses,

skin, muscles, and internal organs to the CNS

Neurons that transmit commands from the

CNS to the muscles, glands, and organs


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Axon of another

neuron

Cell BodyDendrites

Axon

MyelinSheath

Dendrites ofanother neuron


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Dendrite

the bushy, branching extensions of a neuronthat receive messages and conduct impulses

toward the cell body Axon

the extension of a neuron, ending in

branching terminal fibers, through whichmessages are sent to other neurons or tomuscles or glands


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Synapse junction between the axon tip of the

sending neuron and the dendrite or cell

body of the receiving neurontiny gap at this junction is called the

synaptic gap or cleft


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Impulse releasesneurotransmitter

from vesicles

Neurotransmitterenters synaptic gap

Neurotransmitter

binds to receptorson the receiving

neuron


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Neurotransmitters are endogenous

chemicals that transmit signals from a

neuron to a target cell across a synapse


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Neurotransmitter Postsynaptic

effectDerived from

Site of

synthesisPostsynaptic

receptorFate Functions

1.Acetyl choline

(Ach)Excitatory Acetyl co-A +

CholineCholinergic

nerve endings

Cholinergic

pathways of

brainstem

1.Nicotinic

2.Muscarinic

Broken by acetyl

cholinesteraseCognitive functions

e.g. memory

Peripheral action e.g.

cardiovascular

system

2. Catecholamines

i. Epinephrine

(adrenaline)

Excitatory in

some but

inhibitory in

other

Tyrosine

produced in

liver from

phenylalanine

Adrenal

medulla and

some CNS

cells

Excites both

alpha &

beta

receptors

1.Catabolized to

inactive product

through COMT &

MAO in liver

2.Reuptake into

adrenergic nerve

endings

3.Diffusion awayfrom nerve

endings to body

fluid

For details refer

ANS. e.g. fight or

flight, on heart,

BP, gastrointestinal

activity etc.

Norepinehrine

controls attention &

arousal.

ii.Norepinephrine Excitatory Tyrosine, foundin pons.

Reticular

formation, locuscoerules,

thalamus, mid-

brain

Begins inside

axoplasm of

adrenergic

nerve ending iscompleted

inside the

secretary

vesicles

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iii. Dopamine Excitatory Tyrosine CNS,concentrated in

basal ganglia

and dopaminepathways e.g.

nigrostriatal,

mesocorticolim

bic and tubero-

hypophyseal

pathway

D1 to D5

receptorSame as above Decreased dopamine

inparkinsons

disease.

Increased dopamineconcentration causes

schizophrenia


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NeurotransmitterPostsynaptic

effectDerived from

Site of



3. serotonin(5HT)

Excitatory Tryptophan CNS, Gut(chromaffin

cells) Platelets

& retina

5-HT1 to 5-HT

7

5-HT 2 A

receptor mediate

platelet

aggregation &

smooth muscle

contraction

Inactivated by MAOto form 5-

hydroxyindoleacetic

acid(5-HIAA) in

pineal body it is

converted to

melatonin

Mood control, sleep,pain feeling,

temperature, BP, &

hormonal activity

4. Histamine Excitatory Histidine Hypothalamus Three types H1,H2 ,H3 receptors

found in

peripheral tissues

& the brain

Enzyme diamineoxidase

(histaminase) cause

breakdown

Arousal, painthreshold, blood

pressure, blood flow

control, gut

secretion, allergic

reaction (involved in

sensation of itch)

5. Glutamate Excitatory

75% ofexcitatory

transmission

in the brain

By reductive

amination ofKrebs cycle

intermediate

ketoglutarate.

Brain & spinal

cord e.g.hippocampus

Ionotropic and

metabotropicreceptors.

Three types of

ionotropic

receptors e.g.

NMDA, AMPA

and kainate

receptors.

It is cleared from the

brain ECF by Na+

dependent uptake

system in neurons

and neuroglia.

Long term

potentiationinvolved in memory

and learning by

causing Ca++ influx.


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NeurotransmitterPostsynaptic

effectDerived from

Site of



6. Aspartate Excitatory Acidic amines Spinal cord Spinal cordAspartate & Glycine form an excitatory /

inhibitory pair in the ventral spinal cord

7. Gama amino

butyric

acid(GABA)

Major

inhibitory

mediator

Decarboxylation

of glutamate by

glutamate

decarboxylase

(GAD) byGABAergic

neuron.

CNS

GABAA

increases the Cl- conductance,

GABAB is

metabotropic

works with G

protein GABA

transaminasecatalyzes.

GABAC

found

exclusively in

the retina.

Metabolized by

transamination to

succinate in the citricacid cycle.

GABAA causes

hyperpolarization

(inhibition)

Anxiolytic drugs like

benzodiazepine cause

increase in Cl- entry

into the cell & causesoothing effects.

GABAB cause

increase conductance

of K+ into the cell.

8. Glycine Inhibitory

Is simple aminoacid having

amino group and

a carboxyl group

attached to a

carbon atom

Spinal cord

Glycine receptormakes

postsynaptic

membrane more

permeable to Cl-

ion.

Deactivated in thesynapse by simple

process of

reabsorbtion by active

transport back into

the presynaptic

membrane

Glycine is inhibitory

transmitted found in

the ventral spinal

cord. It is inhibitory

transmitter to

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