L15- Nervous System I- cellular

What two organ systems are dedicated to maintaining internal coordination

Endocrine system and Nervous system

How is the nervous system like a control center

It receives, integrates and responds to information

Central Nervous System (CNS) is comprised of?

Brain: Central processing center

Spinal cord: Gateway between brain and trunk/limbs. It takes information from the brain and communicates it with the rest of the organs (think about how it runs through the whole body)

Tracts

What is the Peripheral Nervous System (PNS) comprised of?

Nerves: conducting wires

Ganglia

THIS IS WHAT THE EFFERENT (motor) AND AFFERENT (sensory) FIBERS PASS THROUGH

What are nerves?

Cordlike structures that conduct information.

What are nerves composed of?

A bundle of axons (also called nerve fibers) of neurons

What pathway does PNS use to give input to the brain (CNS: control center)

Afferent Pathway

What pathway does PNS use to give output away from the brain and to the body? (CNS: control center).

Efferent pathway

What are the two center categories in the CNS that encompass the centers that integrate information?

Lower and Higher center

What are the lower centers of the CNS in charge of? What do they consist of ?

They consist of the spinal cord and brainstem. It carries out essential body functions (ex, breathing, heartbeat).

What are the higher centers of the CNS in charge of? What do they consist of?

Consists of the brain (mostly in the cortex). Controls more sophisticated processing of information.

When someone touches something that is hot, what happens?

The SENSATION (stimuli) of something hot is transferred through SENSORY neurons/ Afferent fibers to the CNS. Then the CNS will send a response through MOTOR neurons/ Efferent fibers to the organs.

What do Sensory/ Afferent fibers do?

They carry sensory information from sensory receptors to the CNS

What do Motor/ Efferent fibers do?

Conduct motor instructions from the CNS to effector organs (the muscles and glands)

What is a mixed nerve?

Nerves that contain both sensory and motor fibers

What are the two divisions of the sensory fibers?

Somatic and Visceral

What does the somatic sensory division detect changes in?

Sensory nerves from the skin, skeletal muscles, bones and joints.

For example, in the issue of something hot touching the skin, the somatic sensory fibers would be the ones transferring the information to the CNS because the sensation was caused to the SKIN

What does the visceral sensory division detect change in?

The organs in the viscera (thoracic and abdominal cavities). Think of anything that could be in the chest (lungs, heart, etc) and anything in the lower stomach (spleen,liver, etc)

What does the somatic motor division control?

Voluntary muscle contractions and involuntary muscle reflexes

Basically deal with skeletal muscles

This makes sense because in order for the motor fibers to fix the issue that the sensory fibers sensed they need to be able to MOVE.

What does the visceral motor division control?

Cardiac muscle, smooth muscle and glands

It is known as the autonomic NS

The major functional divisions of the PNS are __________ divisions which convey impulses from peripheral organs and tissues to the CNS

Sensory/ afferent

The _____ division conveys impulses from the CNS to different organs and tissues

Motor/ efferent

What 2 divisions the visceral motor division also break into

Sympathetic and parasympathetic divisions

T/F Our ability to shake our hands as we greet somebody is controlled by the autonomic nervous system

What is the correct answer?

False

Correct Answer: Somatic motor division of the peripheral nervous system

This is the correct answer because shaking hands has to do with the SKIN (skeletal muscle)

T/F When our bladder is full of urine, it will transmit this information to the brain through the visceral afferent fibers

True

This is true because the viscera is the lower stomach region and afferent is TOWARD THE BRAIN

T/F A cut into your skin will be transmitted to your brain through the somatic sensory division

True

sensory=afferent=toward CNS

What is a nuclei?

Collection of neuron cell bodies in the interior of the CNS

What is a Ganglia?

Collections of neuron cell bodies in the PNS

Whats the difference between a ganglia and a Nuclei

The Ganglia is in the PNS and the nuclei is in the CNS

What are tracts?

Bundles of CNS axons that share a common origin, destination and function

What is the difference between nerves and tracts?

Nerves are in the PNS and tracts are in the CNS

What are columns?

Several tracts grouped together that form an anatomically distinct mass

What are the neurons in the CNS that are in-between sensory and motor

Interneurons

Are interneurons in the CNS or PNS

CNS

What is the function of interneurons?

Integrative function

What is integrative function?

Process, store and retrieve information and ‘made decisions’ that determine how the body responds to stimuli

What are the 3 neurons that are involved in the process of the body responding to someone touching something hot?

1. Sensory Afferent neurons sense the pain and send it to 2. interneurons in the CNS process the pain and send a signal on what to do to 3. motor neurons and they take an action.

What are the 3 parts of a neuron?

Dendrites, cell body and Axon

What do dendrites do?

They receive + convey incoming messages to the cell body

Are also called the receptive or input regions

Where do the dendrites send their signal?

Cell body

What is the cell body?

The control center

What does the cell body do?

Integrates information

What does the Axon do?

Generates and conducts nerve impulses away from the nerve cell

Also called the conducting region

What is the purpose of dendritic spines?

They make more surface on the dendrites

This allows for the integration of multiple inputs (more surface means it can hold more receptors and receive more neurotransmitters from different neurons)

What are the receptors on dendrites called?

Chemically regulated ion gates or channels

What enters through the chemically regulated ion gates at the dendrites?

Na+/sodium

What do chemically regulated ion gates/channels do?

Respond to stimulation by NTs

What are other names for the cell body?

Soma, neurosoma, perikaryon

What is the Axon hillock

The line right before the axon that is attached to the cell body (soma)

Why is the Axon hillock important?

It plays an important role in initiating nerve signals

Where is the trigger zone?

Axon hillock and initial segment

What does only the axon have?

Voltage regulated ion gates

This is where the action potential starts

Can action potential start at the dendrites? Why?

No because the dendrites dont have VOLTAGE regulated ion gates and voltage is very important

What is the terminal arborization? What does it do?

The secretion channel.

Releases the neurotransmitter to communicate the info with the next neuron

What do the terminal buttons contain?

Synaptic vesicles full of neurotransmitters, NTs.

What does a multipolar neuron structure have? Where is it located

Multiple dendrites and only one axon’

Located in CNS (brain)

What are the examples of multipolar neurons?

Purkinje cell of cerebellum and pyramidal cell

What does a bipolar neuron structure have? Where are they located

1 dendrite and 1 axon

They are sensory neurons located in some sense organs

What are examples of bipolar neurons?

Olfactory and retinal cells

What does a unipolar neuron structure have? What do they do?

Only one axon. It has 2 names peripheral and central axon

Carry sensory signals to the spinal cord

What is an example of a unipolar neuron?

Dorsal root ganglion cell

What are anaxonic neurons?

They have multiple dendrites but no axon

Identify the incorrect example concerning structural classes of neurons according to the number of processes extending from the soma:

a) Bipolar neurons-olfactory cell

b) Multipolar neurons- Pyramidal cell

c)unipolar neurons- Purkinje cell of cerebellum

d) Bipolar neurons- retinal cell

C) is the incorrect one. purkinje cell of cerebellum falls under multipolar

What do the Neuroglia neurons do?

They support and maintain neurons

What are the 4 types of CNS glial cells?

Oligodendrocytes, Ependymal cells, Astrocytes and Microglial Cells

What do oligodendrocytes do?

Their processes form myelin sheaths are nerve fibers

What do Ependymal cells do?

Line cavities and produce cerebrospinal fluid (CSF)

What do Astrocytes do?

• Convert glucose to lactate and supply this to neurons

• Produce growth factors

• Regulate the extracellular environment (chemical composition)

• Form the blood-brain barrier

• THESE ARE THE MOST ABUNDANT

What do Microglial (macrophages) cells do?

They are defensive cells (phagocytic)

They remove damaged neurons and microorganisms (infections)

What are the 2 types of glial cells in the PNS?

The Schwann cell and Satellite cell

What is the function of the Schwann cell?

Myelinate certain axons in the PNS

They wrap around the axons and help form the myelin sheeth

What is the function of satellite cells?

• Surround and support cell bodies

• Provide electrical insulation

• Regulate the chemical environment

What is the composition of the myelin sheath

Insulation around the axon- 80% lipid

Formed by plasma mb of glial cells

Speeds up signal conduction

How are myelin sheath formed in the CNS?

Each oligodendrocyte reaches out to myelinate several fibers. The myelin wraps around the axon

What are the myelin covered segments called?

Internode

What are the gaps called?

Node of Ranvier

How are myelin sheaths formed in the PNS?

Schwann cell spirals repeatedly around a single nerve fiber.

Each segment of axon is wrapped by a different Schwann cell

What are the parts of the myelin sheath in the PNS?

Axoplasm ( cytoplasm), Axolemma (plasma mb) and Neurilemma

What is the Neurilemma? Why is it important?

The outmost nucleated cytoplasmic layer pf Schwann cells

Its important because it helps the damaged cells regenerate. Which is NOT avaliable in CNS

Regeneration of damaged PNS nerve fiber (axon) can occur if:

Soma is intact and at least some neurilemma remains

What is the nervous pathway?

A series of cells separated by gaps (synapses)

What does action potential consist of?

A sudden, fast transitory and propagating change of the resting membrane potential

It includes the process of Depolarization, repolarization and hyperpolarization

What happens during the resting state? What is the mV

No ions move through voltage-gated channels

The mV is -70

what is the threshold mV

-55

What happens during depolarization?

Na+ flows into cell

What happens during repolarization?

K+ flows out of the cell

What happens during hyperpolarization?

k+ continues to leave the cell

What is an electrical potential?

A difference in the concentration of charged particles between 1 point to another

What is local or graded potential?

Before reaching the threshold, the small depolarization that occurs at -70 is local or graded potential

Where does local or graded potential happen?

In the soma but mostly in the dendrites

Local (or Graded) Potential event location

Cell body and dendrites

Local (or Graded) Potential distance traveled

Shirt distance (stays local)- typically within cell body to axon hillock

Signals decay with distance

Is distance traveled reversible or irreversible in local (or graded) potential?

Reversible

Local (or Graded) Potential stimulus for opening ion channels

Chemical (neurotransmitter) or sensory stimulus (light,pressure,temp)

Local (or Graded) Potential ion channels

Ligand gated Na+ channels

Local (or Graded) Potential peak membrane potential

Excitatory- depolarizes; moves toward 0 mV

Inhibitory- hyperpolarizes; moves towards -90 mv

Action potential event location

Axon hillock and axon

Action potential distance traveled

Long distance- from trigger zone at axon hillock through entire length of axon

Constitutes nerve impulses

Do signals in action potential decay with distance?

No

Is distance traveled reversible or irreversible in action potential?

Irreversible: Cant be stopped once it begins