Synapse junction between neurons - PowerPoint Presentation

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Synapse

junction between neurons or junction between neurons & effectorsSynapses rarely involve just 2 neuronsneurotransmitters (chemicals) are released into the synapse by axon terminal of the pre-synaptic neuronneurotransmitters stimulate the dendrites on post-synaptic neurons or receptors on effectors

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Synapse

each axon terminal is a swollen synaptic knobmakes sure that an impulse can only go in one directionSpeed of transmission is slowed with an increased number of synapses (supporting the reason why reflex arc is quick).

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Neurotransmitters:

Alter the membrane potentials of the postsynaptic neurons.

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The Synapse

What Exactly Happens Here?

An action potential reaches the axon

terminal and triggers vesicles containing

neurotransmitter to move to the

presynaptic membrane. Neurotransmitter

is released into the synaptic cleft.

The neurotransmitter binds to specific

receptors on the post-synaptic dendrite

membrane and causes sodium gates to

open (begins an action potential).

When stimulus is finished, an enzyme (released

from the pre-synaptic neuron) specific to the neurotransmitter binds to it and breaks it down. The broken neurotransmitter is reabsorbed into the pre-synaptic axon terminal to be recycled until the next stimulus.Slide6

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Neurotransmitters can be

Excitatory or Inhibitory

EXITATORY –

when bound to postsynaptic neuron, causes an action potential (depolarization - sodium gates open)

INHIBITORY

–

membrane actually becomes more permeable to K+ ions instead of Na+ (K+ goes out of axon).

-the outside of the axon then becomes even more positively charged than normal in the resting state.

-such neurons are said to be

hyperpolarized

(-100 mV)

because the resting membrane is even more negative

. – NO ACTION POTENTIALSlide7

Neurotransmitter Examples:

AcetylcholineFound at the end plates of many nerve cellsExcites the postsynaptic neurons by opening sodium ion channels; thereby, causing depolarization to occur.

The presynaptic membrane will then release

cholinesterase

, which will destroy acetylcholine. This will cause the Na+ channels to close and the recovery phase can begin.

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Neural Pathways Are Quite ComplexSlide9

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Summation of Nerve Impulses

Summation :

effect produced by the accumulation of

Neurotransmitters from 2 or more neurons.

Neurotransmitters from

neuron A and B are excitatory

but no action potential when

they depolarize separately

-summed together, they can

create an action potential.

-neurotransmitter from neuron

C is inhibitorySlide10

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Why is it important to have inhibitory

neurotransmitters in the body?

In the CNS (brain):

-inhibitory neurotransmitters allow less important information to be

ignored while the brain focuses on more important info.

(sensory information is always the most important)

Ex: GABA

In the PNS:

-inhibitory neurotransmitters allow certain muscles to relax to ensure efficient movement.

Ex: flexing arm musclesSlide11

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There are numerous neurotransmitters

in your body to control all of your actions,

thoughts, moods, etc.

Neurotransmitter

Action

Secretion Sites

Major Effects

acetylcholine

Excitatory to skeletal muscles: excitatory & inhibitory at other locations

Neuromuscular junctions: CNS, PNS

Skeletal muscle contraction

norepinephrine

Excitatory or inhibitory

CNS, PNS

wakefulness

dopamine

Generally excitatory

CNS, PNS

Voluntary movement & emotions

serotonin

Generally inhibitory

CNS

sleep

GABA

inhibitory

CNS

Motor

behaviour

Do Section 11.1 Review p. 384 #1-8Slide12

Common Neurological Conditions

Alzheimer’s DiseaseCharacterized by the deterioration of memory and mental capacity.Related to a decrease in production of acetylcholine.

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Parkinson’s Disease

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Parkinson’s Disease



Characterized by involuntary muscle contractions and tremors.

This is caused by inadequate production of dopamineSlide14

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Drugs & the Synapse

Meth MouseSlide15

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Reminder:

Parts of the Nervous SystemSlide16

The CNS

The brain, in conjunction with the spinal cord, regulates non-conscious processes and coordinates most voluntary movement. Furthermore, the brain is the site of consciousness, allowing humans to think and learn.

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The Spinal Cord

The spinal cord carries sensory nerve messages from receptors in the brain and relays motor nerve messages from the brain to muscles, organs, and glands.

2 types of nerve tissues are present in the spinal cord:

Grey

Matter

:

nonmyelinated interneuron's.connect the spinal cord with the brain

White Matter: myelinated nerves from sensory and motor neurons.

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It is enclosed by the skull and vertebrae –hard and bony structures

Three protective and nourishing membranes, the meninges, lie between the skull and the brain tissue itself and around the spinal cord.

Dura mater: Anchors brain to skull, has large arteries pass through this layer

Arachnoid Layer: Cobweb appearance; contains CSF and holds it close to the brain

Pia Mater (

blood brain barrier

): Fragile, inner most layer consists of blood vessels

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Protection of the Brain and Spinal CordSlide20

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3. The brain floats in a special cerebrospinal fluid (CSF)

Made in the brain, circulates and is reabsorbed by the blood

Provides protection from bumping into the skull

Bathes nerves with metabolites, ions, and nutrients (eases exchange of materials between body fluid and the brain)

4. A highly selective blood-brain barrier limits access of harmful materials to vulnerable brain tissue

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Protection of the Brain and Spinal CordSlide22

Meningitis

Bacterial or viral infections found in the CNS’s CSF.One symptom is inflammation, which causes pressure on the brain.This pressure can lead to delirium, and if left untreated, to drowsiness, stupor, coma and even death.Usually begins with a severe headache, vomiting, fever and stiff neck.

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Nail Through Brain

This computer-generated graphic shows how, in 1848, a 3-foot long, pointed rod penetrated the skull of Phineas Gage, a railway construction foreman. The rod entered his skull below his left eye, passed through his brain, and exited through the top of his skull. Gage survived the accident but suffered lasting personality and behavioral problems.

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Can you Read the paragraph below?

I cnduo't bvleiee taht I culod aulaclty uesdtannrd waht I was rdnaieg. Unisg the icndeblire pweor of the hmuan mnid, aocdcrnig to rseecrah at Cmabrigde Uinervtisy, it dseno't mttaer in waht oderr the lterets in a wrod are, the olny irpoamtnt tihng is taht the frsit and lsat ltteer be in the rhgit pclae. The rset can be a taotl mses and you can sitll raed it whoutit a pboerlm. Tihs is bucseae the huamn mnid deos not raed ervey ltteer by istlef, but the wrod as a wlohe. Aaznmig, huh? Yaeh and I awlyas tghhuot slelinpg was ipmorantt! See if yuor fdreins can raed tihs too.

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Mind Games

Playing Video Games with your mind!Playing Games.

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Brain Trivia

The average number of neurons in the brain = 100 Trillion

A newborn baby’s brain is as soft and gooey as tapioca pudding!

The adult brain comprises about 1/15 of the weight of the whole body, averaging 3 pounds and 2 ounces.

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Brain Plasticity

Brain Plasticityhttp://youtu.be/2MKNsI5CWoU

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THE HINDBRAIN

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Cerebellum

Referred to as the little brain

Responsible for coordinating gross motor coordination of movement, muscles and balance (equilibrium)

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Brain Parts

Unconscious functionsSlide32

Medulla Oblongata

First extension of the spinal cordVery important in maintaining vital functions; breathing, heart rate and blood pressure (diameter of blood vessels)

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Brain Parts

Automatic functions– the ones you don’t want to think aboutSlide33

Pons

Acts as a bridge or relay center – has fibers which connect two hemispheres of cerebrum and cerebellum to the rest of the brain

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Brain Parts