Unit 9: Nervous System

Izzy was an active 22 year old when she

started to notice that her legs and arms

felt “heavy” and her vision was blurred.

One day, while jogging, she wasn’t fully

able to lift her left foot from the pavement,

and kept veering off the sidewalk. She

said it felt like she was “drunk.”

She called the doctor and discovered that

she couldn’t speak on the phone, her

words wouldn’t come and when she could

speak, the words were slurred.

Izzy’s Youtube ChannelWhen she made it to the doctor, the,

he immediately had her admitted to the

hospital.

There, she saw several neurologists

who asked her to perform several

tasks such as:

● touch your nose

● walk in a straight line

● read a passage of text

An MRI was ordered to scan her brain.

What do you notice about this image?Neurologists have proposed

several possible diagnoses

for Izzy.

1. Stroke

2. Brain tumor

3. Epilepsy

4. InfectionIzzy’s next test was a

lumbar puncture.

A needle is placed between

the lumbar and spinal fluid

is drawn to check for

inflammation and bacterial

infection.

Izzy was in the hospital for all of these tests, and

her symptoms were getting worse, not better. She

could not move, go to the bathroom or feed herself.With physical therapy, Izzy was able to

leave the hospital after 6 weeks. She

was referred to a specialist.

At this appointment, the specialist

showed her the brain scan and said

“These white spaces are lesions, or

scar tissue. They shouldn’t be there

and are signs of brain damage.“

Diagnosis:

Aggressive Onset Multiple SclerosisThe Nervous System

- Includes the brain, spinal cord and the nerves

So what happened to Izzy?

*Recall her main symptomsOverall function - coordinate

the body’s systems by receiving

and sending information;

maintaining homeostasis

● Sensory - receives information

● Integrative - determines where information is sent

● Motor - responds to signals

How were these systems working

(or not working) in Izzy’s case?Two Divisions of the Nervous System

Central Nervous System (CNS)

Brain and spinal cord

Peripheral Nervous System (PNS)

Nerves throughout the body

31 pairs of spinal nerves

12 pairs of cranial nervesSomatic Nervous

System

- skeletal

- voluntary

Autonomic Nervous

System

- smooth muscles

- glands

- involuntaryAutonomic Nervous

System (2 branches)

Parasympathetic

(rest and digest)

Sympathetic

(fight or flight)What was going on with Izzy? Why did she have lesions on

her brain that caused so many problems? The answer lies

within the cells of her nervous system: the NEURONS.

Symptoms associated with MS:

● Sensory loss: numbness in limbs, burning or prickly sensations

● Spinal cord symptoms (motor): muscle cramping, paralysis

● Vision problems: blindness or blurred vision

● Constitutional symptoms: fatigue and dizziness

● Cognitive difficulties: concentration, memory, and judgment

● Mental health: depression, bipolar disorder or dementiaNeurons = masses of nerve cells that

transmit information

*functional unit of the nervous system

1. Cell Body - contains the nucleus and

other cell organelles

2. Dendrites – shorter, more numerous,

receive information

3. Axons - single long fibers, conducts

information away from the cell

1

2

3Chromatophilic substance (rough ER) - transport system

-insulation surrounding axons

- gaps in the insulation

Myelin Nodes of Ranvier Neurofibrils are

fibers within the

axon.Neuroglial Cells - Support for neurons

node of ranvier1. Microglial Cells - Immune function; digest debris, kills

bacteria2. Oligodendrocytes -

make myelin sheath

that provides insulation

around the axons3. Astrocytes - connect blood vessels to neurons

I connect to

blood

vessels4. Ependymal Cells - forms membranes around tissue5. Schwann

cells: form the

insulating myelin

sheath around

the neurons in

the PNS

(same function as

oligodendrocytes,

which are found in the

CNS)Myelin Sheaths - insulate axons

Schwann cells supply the

myelin for peripheral neurons.

Oligodendrocytes myelinate the

axons of the central nervous

system.

Gaps in the sheath are called:

NODES OF RANVIERWhat is wrong with Izzy’s neurons?

Nerves lose their

myelin sheath, this is

called demyelination the neurons lose their

myelin, the nerves are

unable to send or receive

signals.

What aspects of Izzy’s

symptoms indicate loss of

these signals?How nerve impulses travelA

Which cell….

1. Creates myelin sheath

2. Has an immune

function

0

3. Forms a membrane

M

4. Connects to a blood

supply

E

Practice with neuroglia coloring!Myelinated (white matter) – myelinated axons

matter) - unmyelinated

Unmyelinated (grey Lesions are evidence of

nerve cell damage in your

brain or spinal cord.

Symptoms can vary depending on

the location of the lesion.

- lesions on the spinal cord may

cause motor problems

- lesions on the back of the brain

may cause balance problemsWhy are the neuron’s in

Izzy’s brain demyelinating?

- Why is this called

an AUTOIMMUNE

disease?

- What does

“sclerosis” mean?Fun Facts about Neurons

-Longevity – can live and function for a lifetime

-Do not divide – fetal neurons lose their ability to undergo

mitosis; neural stem cells are an exception

-High metabolic rate – require abundant oxygen and glucose

-The nerve fibers of newborns are

unmyelinated - this causes their

responses to stimuli to be coarse and

sometimes involve the whole body.

Try surprising a baby!Nerve Impulses = weak electric current, like a wave1. Neuron membrane

maintains resting potential

2. Threshold stimulus is

received

3. Sodium channels open

4. Sodium ions diffuse inward,

depolarizing the membrane

channels open

6. Potassium ions diffuse

outward, repolarizing the

membrane

5. Potassium 7. The resulting action

potential causes a local

that

bioelectric current stimulates the

membrane.

8. Wave of action

potentials travel the

length of the axon as a

nerve impulseIons in the cell and outside the

cell create a positive and

negative side, which produces

an electric current.Depolarization:

loss of the difference in

charge between the

inside and outside of the

plasma membrane of a

muscle or nerve cell due

to a change in

permeability and

migration of sodium ions

to the interiorLabel the Graph:

1. Resting

2. Depolarization

3. Repolarization

4. RestingNerve Impulse

the size Speed is proportional to

of the axon

greater diameter =

faster impulse

Myelinated axons conduct

than

unmyelinated one

impulses faster Treatments for MS

Most treatments focus on

suppressing the immune system

so that immune cells do not

continue to attack neurons.

Chemotherapy

Anti-inflammatory drugs

(steroids)

Physical therapyautologous hematopoietic stem cell transplantation (AHSCT)Meet Izzy!

No one really knows

why a person gets MS,

but it is more common

in women.

Izzy’s Youtube

ChannelCommunication Between Neurons

Synapse = junction between two communicating neurons

Nerve pathway - nerve impulse travels from neuron to neuron

Dendrite → cell body → along axon -> synapse (gap) → dendriteTo complete the signal, a

NEUROTRANSMITTER is

released at the gap to signal

the next neuron.

Receptors on the dendrite

receive the chemical

messageAnatomy of the Synapse

A: Neuron (axon)

B: Neuron (dendrite)

1. Mitochondria

2. Vesicle

3. Receptor

4. Synapse

5. Receptor

6. Calcium Channel

7. Releases neurotransmitter

8. Re-uptakeTypes of Neurotransmitters

Excitatory - increase membrane

permeability, increases chance for

threshold to be achieved

Inhibitory - decrease membrane

permeability, decrease chance for

threshold to be achievedExamples of Neurotransmitters

Acetylcholine - stimulates muscle contraction

Dopamine - mood, happiness

Serotonin = sleepiness and mood

Endorphins = pain reduction, moodAgonist = molecule that has

the same effect on the

postsynaptic neuron as the

neurotransmitter itself does.

Antagonist = molecule that

blocks the effect that the

neurotransmitter normally has

on the postsynaptic neuron. Anatomy of a Nerve Impulse (Coloring)Antidepressants

Zoloft is part of a class of drugs called

selective serotonin reuptake inhibitors

it inhibits the uptake of

serotonin back into the cell,

keeping mood elevated for a

longer time.Cocaine

If cocaine is present, it

attaches to the dopamine

transporter and blocks the

normal recycling process,

resulting in a buildup of

dopamine in the synapse,

which contributes to the

pleasurable effects of

cocaine.Your

neurotransmitters

on cocaineEcstasy (MDMA)

The neurotransmitter serotonin is vital in

regulating many of our basic functions.

Serotonin is, among other things, the feel

good neurotransmitter and helps to

regulate body temp.

Our brain cells are recycle serotonin back

into the cells and out of the synapse using

serotonin reuptake transporters.

Ecstasy essentially takes these upkeep

transporters and reverses their roles. This

causes a massive flood of serotonin from

the brain cells into the synapse.

The most common cause of

Ecstasy-related death is

overheating (hyperthermia).Heroin

Activates opiate receptors

Blocks release of GABA

More dopamine is released

Dopamine Receptors

DOPAMINEAmphetamines

Mimic dopamine - binding to

receptors

Dopamine does not re-enter

the cell, depleting the cell’s

supplyDisorders Related to Neurons

ALS - (Lou Gehrig’s Disease) Amyotrophic Lateral Sclerosis

Progressive degeneration of

nerve cells in the spinal cord

and brain

NEURODEGENERATIVE

- this means symptoms will

get worse over time.

- most patients die within 5

years of diagnosisEpilepsy

Epileptic seizures are caused by

excessive electrical activity within

networks of neurons in the brain.

A fine balance between excitation and

inhibition must be maintained in order

for the brain to function normally.

If there is too much glutamate, neurons

can become hyperexcitable and a

seizure may result. Too little GABA

(inhibitory) can also result in a seizure.

2 Minute Neuroscience - EpilepsyMyasthenia Gravis

autoimmune disorder in

which antibodies destroy

neuromuscular

connections

We did a case study on

this during the muscle

chapter, do you

remember it?

The Meninges

= membranes located between bone and soft tissues

What is

meningitis?Meningitis

Meningitis can be

bacterial of viral.

● fever

● stiff neck

● photosensitive

● vomiting

● rash

*There is a vaccine!

Can cause

serious

complications,

even death.Cerebrospinal fluid

(CSF) is a clear liquid that

bathes the brain and

spinal cord; cushions the

brain and serves as a

shock absorber.Subdural Hematoma

Associated with

traumatic brain

injury. Bleeding

within the brain,

puts pressure

on the brain

and can be life

threateningSpinal Cord

passes down the vertebral canal,

(each with a pair

has 31 segments of spinal nerves)

They are named for their location

C1 - C8

T1 - T12

L1 - L5THE BRAIN Cerebrum

3 Major

Parts of the

Brain

Brain Stem

CerebellumCEREBRUM -

wrinkly large part

of the brain

(cerebral cortex)

higher mental

function, solving

problemsCEREBELLUM

Balance and coordination

White matter within the

cerebellum give it a

tree-like appearance -

this is called the

ARBOR VITAE

(“Tree of Life”)Brain Stem -

regulates visceral

functions

(autonomic system)Anatomy of the Brain (Coloring)

hypothalamus

Medulla oblongataPARTS OF THE BRAIN

Split brain

experiments?

Cerebral Hemispheres

- left and right side separated by the ....

Corpus Callosum - connects the two hemispheresCorpus callosumBrain Convolutions

- the wrinkles and

grooves of the cerebrum

Fissures = deep groove

Sulcus = shallow groove

= bump

Gyrus Each sulcus has a name based upon its location on the brain.Central Sulcus

Frontal Lobe Parietal Lobe

executive

functions perception,

sense-making,

math

Lateral

Fissure

Occipital

Lobe

vision

Temporal

Lobe

memory,

languageLongitudinal fissure - separate right and left sides

Transverse fissure - separates cerebrum and cerebellumVENTRICLES OF THE BRAIN

Fluid filled cavities, contain CSF

3rd

Ventricle

(1st and 2nd

ventricles)Association Areas

- interpreting and analyzing informationBRAIN STEM

Thalamus

Hypothalamus

Pituitary

Midbrain

Pons

Medulla OblongataDiencephalon

has 2 parts.....

Hypothalamus -

hormones, heart rate,

blood pressure, body

temp, hunger, attaches to

(red)

Thalamus - relay station

pituitary Optic Tract / Chiasma - optic nerves cross over each other

The left side

of the brain

controls the

right side of

the body!Midbrain – visual

reflexes, eye

movements

Pons - relay sensory

information

Medulla – heart,

respiration, blood

pressurePituitary Gland

The "master gland" of

the endocrine system.

It controls hormones.Corpus callosum

Thalamus

Hypothalamus

Pituitary glandMedulla

Oblongata Pons

MidbrainHIPPOCAMPUS

(“sea horse”) - storage and retrieval of memories

Amygdala - storage of

memories associated with

emotion.

~Also associated with fear

response and aggressionThe LIMBIC SYSTEM

-hypothalamus

-hippocampus

-amygdala

has a role in emotions

Why are

teenagers

impulsive?