Neuronal Physiology

Neuroglia

support neurons, small and numerous, non-excitable, found in CNS and PNS

Macroglia, Microglia

Classes of Neuroglia

Astrocytes

Neuroglia: Type of Macroglia: Small body and many processes, function as structural support

Guide for Neuronal Navigation, Maintenance of Extracellular Ionic Concentration, Form tight endothelial junctions, Repair of damaged neural tissues, neurotransmitter reuptake (blood brain barrier),

Neuroglia: Type of Macroglia: Function of Astrocytes

Since they surround blood capillaries, the inner wall of it is lined with endothelial cells; Astrocytes project their end feet to capillaries and blood vessels and they form tight endothelial junctions, forming the blood brain barrier

How does it happen? Formation of tight endothelial junctions \> blood-brain

Endothelial Junctions

where cell membrane and adjacent cells are linked together

Blood Brain Barrier

only allows passage of certain substances (e.g. water, glucose), not exactly permeable

Myelin formation and maintenance

Neuroglia: Type of Macroglia: function of Oligodendrocytes and Schwann Cells

Oligodendrocytes

Type of Macroglia: Fewer processes coming out of the body, CNS, Wraps around many segments of the axon. Connections with many axons of the neurons, Looks similar to astrocytes except they have less projections

Schwann Cells

Type of Macroglia: PNS, Wraps around a single segment in axon, only wraps around one

Ependymal Cells

Type of Macroglia: Cuboidal/columnar with cilia

Cilia

hair-like structures

Line ventricles and central canal, Assist in CSF circulation, Form choroid plexus

Type of Macroglia: Ependymal Cells Function

Choroid plexus

responsible for CSF production

Satellite Cells

Type of Macroglia: Cuboidal, Surround the individual neurons in the sympathetic and parasympathetic nervous system, and the sensory system

Maintain microenvironment of ganglion cells

Type of Macroglia: function of satellite

Ganglia

group of neurons

MICROGLIA

Class of Neuroglia: Smallest of neuroglia, Known as "Scavenger" or "macrophage"

migrate to the site of injury and clean debris, mediate immune response, detect and destroy foreign bodies

Type of Macroglia: function of microglia

phagocytic mechanisms

MICROGLIA: Clean debris after neural cell death through

NEURON

Communicate chemical or electrical messages to glands, muscles, and other neurons

Excitable

NEURON: \___, meaning they generate electrical impulses hence why they can communicate electrical messages

Cell Body / Soma / Perikaryon

Parts of Neurons: Internal space made of cytoplasm which contains nucleus, organelles, typical structures,

etc; it actively synthesizes proteins which help maintain the axonal part of the neuron, Surrounded by plasma membrane

plasmalemma

Forms the barrier between the inside of the neuron and the outside extracellular environment

Dendrites

Parts of Neurons: Shorter, more numerous, Receive neural impulses, contain dendritic spines

dendritic spines

Thorn-like protuberances coming out of the branches, Help expand area of contact, Allow electrical messages and impulses to converge to the neuron

Axons

Parts of Neurons: Single, long fiber, Conduct neural impulses away from the cell/neuron, Saltatory transmission

axon hillock to axon terminal/bouton

Neural impulses are conducted from

AXONAL TRANSPORT

movement of proteins, etc. in the axon to maintain the structural integrity of neuron

Anterograde

towards the axon terminal (hillock to terminal) (forward)

Retrograde

axon terminal to body, (terminal to cell body) (backwards)

trophic substances, nerve growth factors, nutrition to neuron

Retrograde help with the movement of

Axon Hillock

PARTS OF AXON: Cone shapes

Axon Terminal/Bouton

PARTS OF AXON: At the end of the axon, looks like a button

Myelin

PARTS OF AXON: Fatty substance, Increase the speed of neural impulse conduction

Nodes of Ranvier

Myelin Segment: allows saltatory transmission, node to node, increasing speed of neural impulse conduction

Multiple Sclerosis

MYELIN DISORDERS: Autoimmune inflammatory response that damages the myelin sheaths, Unknown cause (sometimes said to be genetic or from environmental exposures), Characterized by the appearance of Demyelination of CNS white matter

Sclerosis

\= hardening

autoimmune inflammation response triggered -\> degeneration of myelin sheaths -\> debris is produced -\> microglia cleans up -\> astrocytes come and proliferate -\> causes glial scars -\> formation of multiple plaques -\> weak neural impulses

How does Multiple sclerosis occur?

speech impairment (Dysarthria)

Multiple Sclerosis: 1⁄2 of population \> \___ \___ \___ : Reduced respiratory control, Reduced vocal intensity - slurred or wrong articulation

Multipolar

TYPES of CNS Neurons: Most common type, One single axon, multiple dendrites

Bipolar

TYPES of CNS Neurons: Two processes coming out of either end, Found in retina

Pseudounipolar

TYPES of CNS Neurons: One central process then branches out into peripheral processes which goes to peripheral structures, Peripheral process: contains dendrites, Found transmission sensation of sensory nerves

Plasmalemma (structures and properties)

FACTORS WHICH MAINTAIN THE RESTING POTENTIAL

BILIPID MEMBRANE

Separates intracellular and extracellular material, Two rows of phospholipid molecules, The lipids do not dissolve in water and because of that it separates the intracellular environment from extracellular environment

center, water

BILIPID MEMBRANE: arranged so that the hydrophobic ends are facing to the \___ and hydrophilic ends face to the

concentration

The fluid inside and outside are relatively similar in the chemical composition, the only difference is the \____ of their chemicals

Extracellular fluid

what fluid has a greater concentration of water

negative

Net charge of intracellular fluid is

potassium

The inside of your cell has greater concentration of \____.

sodium, chloride, and calcium

The extracellular contains greater concentration of

potassium

Remember: \___ lang marami sa intracellular, the rest outside

Protein anions

(negative charge), because these are only present in the intracellular, it gives the inside an inherently negative bias already.

water

Brain has the most \___ out of all parts of our body

concentration gradients

Different concentrations create

Law of diffusion

Greater concentration goes to lesser concentration environment

electric impulse

Movement of electrically charged particles

inside

greater to lower concentration, greater concentration of Na outside the cell, so it should flow to the

channels and pumps

PROTEINS: Ions can't pass through the middle layer because it is hydrophobic, they will need a passageway, this is through channels and pumps

Channels and pumps

Maintain ionic concentration across the membrane, Allows ions to move back and forth

CHANNELS

Completely open, Selective to one ion only

Non-gated

Channels: Always gonna be open

Gated

Channels: Open in certain conditions

Ligand-Sensitive

Types of Gated Channels: Will open and close due to certain chemical/ligand, "Lock and key"

Voltage-Gated

Types of Gated Channels: Open and close at specific membrane potentials/electrical charge of the environment, Operated by a voltage/electrical sensor, Allows the channel to change its shape and open & close, "Remote care key"

Mechanically-gated

Types of Gated Channels: Change is brought about by some mechanical pressure, Found in sensory neurons, responsible for sensory inputs

Voltage-gated Ligand-sensitive

Combines ligand and voltage, Responds in changes of the membrane potentiation, because of changes of electrical environment, thus causing the gate to open, Membrane impulse and electrical impulses in the environment causes the gate to open before chemical can actually affect the opening of that channel, Opens before the neurotransmitter can affect that channel

Pumps

Open on one side at a time, Actively pump or move ions against the concentration gradient, Need metabolic energy

sodium-potassium pump

One of the most important pumps is the

adenosine triphosphate (ATP)

sodium-potassium pump Fueled by

"3 Na+ out, 1 K+ in"

sodium-potassium pump (what and how many in and out)

phosphate

a \___ ion of atp will bind with the pump, resulting in driving out 3 sodium ions, in exchange may 2 potassium ions na papasok.

sodium-potassium pump

Helps maintain the extra and intracellular fluid composition

SEMI-PERMEABLE

Only allows passing back and forth of certain substances Permeability of the cell membrane

K+, Na+

SEMI-PERMEABLE: Contains more \__ channels than \__ channels

K+, Na+

At rest: greater permeability to \__ than __

efflux, influx

Greater \_____ of K+ than \___ of Na+

MEMBRANE POTENTIAL

Degree of positive and negative charge separation across a neuron's cell membrane

voltage

MEMBRANE POTENTIAL Synonymous with

neuronal signaling

Changes in membrane potential result in all forms of

RESTING MEMBRANE POTENTIAL

Ionic difference across the membrane at a steady state, Neuron is NOT firing an impulse (Stable lang)

-70 mV

RESTING MEMBRANE POTENTIAL: Intracellular fluid \=

Diffusion of Na+ and K+ thru passive ion channels, Na-K pump

RESTING MEMBRANE POTENTIAL: Maintained by:

stimuli

RESTING MEMBRANE POTENTIAL: Adequate \__ changes resting potential, to generate an electrical message/neural impulse

stimulus

GENERATION OF THE NEURAL IMPULSE (ACTION POTENTIAL): Need adequate \___ to change action potential

Apply the stimulus -\> Opens certain ion channels to open -\> resulting in some kind of polarization -\> relative charge across the membrane

GENERATION OF THE NEURAL IMPULSE (ACTION POTENTIAL): process

Depolarization

GENERATION OF THE NEURAL IMPULSE (ACTION POTENTIAL): EVENTS: Voltage-gated Na+ channels open rapidly, Influx of Na+ ions, Since it opened, sodium ions will move along concentration gradient and go inside the cells, Intracellular becomes less negative

Graded potential

GENERATION OF THE NEURAL IMPULSE (ACTION POTENTIAL): EVENTS: Not fully propagated along the axonal membrane → Restricted to that area of neuron

depolarization or hyperpolarization

Graded potential Caused by either

size of the stimulus

The depolarization amount depends on the

Spatial summation

To generate AP: Number of graded potential occurring in the membrane all occurring at the same point, Summate in space, Same place nangyayari yung graded potential

Temporal summation

To generate AP: Summate in time, Doesn't necessarily occur in the same place, Number of graded potential occurring in the membrane, all occurring at the exact same time

Action potential

GENERATION OF THE NEURAL IMPULSE (ACTION POTENTIAL): EVENTS: All or nothing, Each can last less than 1 millisecond, Threshold is achieved, Start of axon, propagated down the axon towards its terminal, once you reach the threshold it will continue to be, Uniform size and duration

-55 mV

Action potential: Intracellular:

axon hillock

Action potential: Initiated at

Repolarization

GENERATION OF THE NEURAL IMPULSE (ACTION POTENTIAL): EVENTS: Voltage-gated Na + channels close, Voltage-gated K+ channels fully open, Both happen simultaneously, however Na+ is slower after starting at the same time, Efflux of K+ ions, potassium ions will go out of the cell, becolmes negative

Hyperpolarization

GENERATION OF THE NEURAL IMPULSE (ACTION POTENTIAL): EVENTS: Even lower than whatever it was at rest, Influx of Cl- ions or efflux of K+, Intracellular becomes even more negative than at rest, It closes very slowly, too many potassium ions go out, which becomes even more negative than at rest, It goes back to its resting state

second AP

Hyperpolarization Prevents \___ \___ from being generated

Refractory Period

GENERATION OF THE NEURAL IMPULSE (ACTION POTENTIAL): Absolute & Relative