A&P unit 3 - neurons and neurotransmitters (copy)

components of CNS vs PNS

CNS = brain, spinal cord

PNS = nerves, ganglia (bundles of nerves)

Afferent nervous system

sensory neurons, go TO CNS

(afferent = arrive)

-somatic and visceral

somatic sensory system

-afferent

-detect stimuli we consciously perceive

→ 5 senses, propioreceptors

visceral sensory system

-afferent

-detect unconscious stimuli

→ signals from internal organs

Efferent nervous system

initiate motor output FROM CNS

(efferent = effect)

→ somatic and autonomic motor systems

→ sympathetic and parasympathetic

somatic motor system

-efferent

-send voluntary signal to skeletal muscles

autonomic/visceral motor system

-efferent

-send involuntary signal to cardiac and smooth muscle

-includes sympathetic and parasympathetic

sympathetic vs parasympathetic

sympathetic = fight or flight

parasympathetic = rest and digest

afferent, efferent motor system diagram (photo)

nerve diagram

need to know

-epineurium

-perineurium

-endoneurium

-fasicle

neuron diagram

dendrites = receive input

-cell body/soma = integrate incoming signals

-axon hillock = trigger zone for new signal

-pre-synaptic terminals/axon terminals = send output to other cells

What are the 5 characteristics of neurons?

1) excitability - respond to a stimulus

2) conduct signal across axon

3) secrete neurotransmitter

4) longevity - lasts across your lifetime

5) amototic - can’t do mitosis

anterograde transport

move FROM cell body

-move newly synthesized material toward synaptic knob

retrograde transport

move TO cell body

-moves used materials from axon for breakdown/recycling

Fast axonal transport (image)

Kinesin = anterograde

Dynein = retrograde

*both require ATP

-move 400mm per day

slow axonal transport

-move 0.1-3mm per day

-flow of axoplasm (axon cytoplasm)

-only in anterograde direction (from body)

-moves enzymes, cytoskeletal components, new axoplasm

multipolar neuron

-many dendrites

-1 axon

→ all motor neurons

bipolar neuron

-1 dendrite

-1 axon

-soma in middle

→ sensory neurons of 5 senses

unipolar neuron

-single short process from cell body → 1 axon

-one side of axon in peripheral direction (to PNS), one side in central direction (to CNS)

→ sensory neurons

anaxonic neuron

-no axons

-dendrites come directly off cell body

→ interneurons

neuron input, output diagram

sensory neurons

-afferent (conduct input to CNS)

-unipolar and bipolar

motor neurons

-efferent (conduct input from CNS to effectors)

-multipolar

interneurons

-in between afferent and efferent neurons

-receive and process info from other neurons

-multipolar or anaxonic

-make up 99% of neurons

components of glial cells

-non-excitable

-capable of mitosis

-protect & nourish neurons

-physical scaffold for neurons

-90% of cells in CNS

what kind of cells do brain tumors form from?

glial cells → they are capable of mitosis and neurons are not

Astrocytes

-most common glial cell

-form blood brain barrier

-structural support

-assist neuronal development

-occupy space of dying neurons

-regulate tissue fluid composition (ex. can regulate [K+])

Ependymal cells

-glial cell

-line cavities in brain and spinal cord

-cushion neurons and provide nutrients

-produce CSF of CNS

Microglia

-smallest glial cells

-phagocytic, immune system

-wander CNS and replicate during infection

-also remove debris

Oligodendrocyte

-very large glial cells

-form myelin sheath of CNS

Neurolemmocytes

-glial cells

-Schwann cells

-form myelin sheath of PNS

synaptic plasticity / plasticity

neuron signal pathway can be strengthened or weakened over time depending on how much we use it → how learning happens

post synaptic facilitation/inhibition vs

presynaptic facilitation/inhibition

post = EPSP/IPSP thru synapse

→it is axosomic = axon to soma of next cell, 2 cell action

pre = axoaxonal - axon release directly onto axon, 3 cell action

postsynaptic facilitation/inhibition image

how does presynaptic inhibition work?

(ADD IMAGE)

cell B release NT → opens chem gated Cl- channel on Cell A

Cell A gets more negative → prevent Ca VGC opening → no new NT release onto cell C

result = AP is not transferred

NT chemical structure category

1) Acetylcholine (ACH)

-needed for skeletal muscle contraction

-different structure than amino acid based categories

NT chemical structure category

2) biogenic amines

-modified Amino acid

-decarboxylase takes carboxyl off an AA

-includes catecholamine and indolamine

catecholamines

-subclass of biogenic amine

-has single ring catechol + R group

epinephrine

norepinephrine

dopamine

indolamines

-subclass of biogenic amine

-has double ring indole + R group

histamine

serotonin

NT chemical structure category

3) Amino acids

-unchanged form of AA acting as a NT

GABA - EPSP

glutamate - IPSP

glycine - IPSP

NT chemical structure category

4) neuropeptides

-long chains of AAs

endorphins

NT chemical structure image/graph

NT function category

effects

divided into excitatory (EPSP) or inhibitory (IPSP)

NT function category

actions - Ionotropic

-NT directly opens ion channels by binding to receptor

-immediate postsynaptic effect

NT function category

actions - Metabotropic

-NT indirectly causes response by binding to GPCR

-slower, but more diverse effects

NT function image/graph

Acetylcholine synthesis

A) synthesis = acetate + choline, then gets stored in vesicles. released when AP signal

-more signal → more ACH release

Acetylcholine removal

B) removal from cleft = acetylcholinesterase breaks ACH into acetate and choline. binds to muscarinic receptors

-type of muscarinic determines if it’s EPSP or IPSP

how do MAOI’s work?

“monoamine oxidase inhibitors”

monoamine oxidase = enzyme that breaks down NT

→ MAOI inhibits this enzyme so NT doesn’t get broken down

→ more NT available = more released = more binding to post-synaptic cell

How do tricyclics and SSRI’s work?

both block reuptake so NT stays in synapse longer = greater chance NT will bind to post-synaptic cell

→ tricyclics = serotonin & norepinephrine

→ SSRIs = serotonin ONLY

What are the 3 types of Antidepressants?

Selective Serotonin Reuptake Inhibitors (SSRI’s)

Monamine Oxidase Inhibitors

Tricyclic

How does an SSRI work?

They block the reuptake of Serotonin allowing it to continue to pass messages.

How does an MAOI work?

They block the destruction of Neurotransmitters that are outside vesicles.

How do Tricyclic antidepressants work?

They block reuptake of serotonin and norepinephrine.

They also act as antagonists for other receptors such as Histamine.

Multipolar

All motor Neurons

Bipolar

Sensory Neurons

Unipolar

Sensory Afferent Neurons

Anaxonic

Interneurons

Name the Motor Proteins

Kinesin and Dynein

3 Chemically Gated Channels

Cation

Cl

K

Glutamate is what kind of NT?

Ammino Acid

GABA is what type of NT?

Ammino Acid

Glutamate is what kind of NT?

Ammino Acid

Serotonin, Histamine, Dopamine are all kinds of what NT?

Biogenic Ammines

Endorphin is what kind of NT?

Peptide

Function of acetylcholine

Muscle Contraction

Define Axosomatic

Inhibition/Facilitation occurs from the axon towards the Soma of the Postsynaptic cleft.

Define Axoaxonal

Inhibition/Facilitation occurs at the axon of one of the competing nerves.