Nervous Sytem: Basics

Summer BIO 211

nervous system role

help all parts of the body communicate with each other

nervous system parts

central nervous & peripheral nervous

central nervous system

brain & spinal cord

central nervous resides

vertebral cavity

peripheral nervous system

everything else beyond the CNS

basic functions parts

somatic nervous & autonomic nervous

somatic nervous system

responsible for conscious perception and voluntary movement

autonomic nervous system

responsible for involuntary control of the body

cell types

glial cells, neurons

glial cells

supporting cells for neurons

glial cell types are considered

the connective substance for the nervous system

what are the types of glial cells

astrocyte, oligodenrocyte/Schwann cell, microglia, ependymal cells, satellite cells

astrocyte

interact with blood brain barrier & pull nutrients

what do astrocytes anchor neurons to

nutrient supplies

what is the most abundant glial cells

astrocyte

another name for a oligodenrocyte

Schwann cell

Schwann cell

creates myelin sheath to insulate the axons

microglia

immune surveillance for the nervous system

microglia (shape)

small oviod with spiny processes

ependymal cells (shapes)

squamous to columnar

ependymal cells

lines cavities of brain and spinal column

satellite cells

surround neuron cells bodies with ganglia

what does satellite cells have multiple of

cell bodies

neurons

functional part of the nervous system that can send electrical impulses

what are the parts of a neuron

dendrites, cell body (soma) , axon hillock, axon

dendrites

accepting end for neural signaling

cell body other name

soma

soma

contains cell body and common cell components

axon hillock

area where axon impulses originate

axon

sending end for neural signaling

do neurons have different types depending on the situation

yes

what are the neurons that work send signals to CNS

sensory (afferent)

THINK: Afferent → Arrive

another name for sensory neurons

afferent

what are the neurons that carry impulses away from the CNS

motor (efferent)

THINK: Efferent → Exit

another motor neuron

efferent

interneurons another name

association

interneurons

shuttle signals through CNS pathways

how are neurons classified

by the structure, the number of processes extending from the cell body

what are the structural classifications of neurons

multipolar, bipolar, unipolar (pseudopolar)

multipolar

many processes extending form the soma, & all are dendrites except for a single axon

bipolar

two processes extending from the soma & 1 is a fused dendrite & the other an axon

unipolar

one process extends from the cell body & forms central & peripheral processes, which together comprise an axon

what are the 3 regions of a neuron

receptive region, conducting region, secretory region

receptive region

receives signal

conducting region

generates/transmits action potential

secretory region

axon terminals release neurotransmitter

where is multipolar neuron located in the body

major neuron in the CNS

what is the most abundant neuron

multipolar

where are bipolar neurons found in the body

some special sensory organs (olfactory mucosa, eye, ear)

are bipolar neurons rare or common

rare

where are unipolar neurons found

mainly in the PNS

where are unipolar neurons common

in dorsal root ganglia of the spinal cord & sensory ganglia of cranial nerves

what are the function class of multipolar neurons based on the impulse conduction

most → interneurons

some → motor neurons

what are the function class of bipolar neurons based on the impulse conduction

essentially all → sensory

what are the function class of unipolar neurons based on the impulse conduction

most → sensory

signal relays

signal needs to be perceived, sent to the brain, interpreted, then sent back to be responded

parts of signals relays

afferent, efferent neurons & autonomic division

afferent neurons

carry the signal from the PNS to CNS

THINK: Afferent → Arrive

efferent neuron

carry motor info from the CNS to the PNS for response

THINK: Efferent → Exit

autonomic division

regulates involuntary responses

Action potential

the fluctuation of membrane charge

what is important to note about the fluctuations in action potential

they are always the same regardless of the stimulus

where do action potentials occur in the body

muscles and neurons

what are the parts of action potential

depolarization, repolarization, refractory period

depolarization

potential raises towards zero

repolarization

the drop in the potential back towards resting

refractory period

the inhibition of another action potential firing when one is in progress

voltage (V)

measured of potential energy generated by separate charge

potential difference

voltage measured bwtn 2 points

current (I)

flow of electrical charge flow

resistance (R)

hinderance to change flow

insulator

substance with high electrical resistance

conductor

substance with low electrical resistance

what is the resting membrane potential

-70mV

what does -70mV mean about a neuron

it’s the charge of the neuron when it’s at rest

how many steps are there for action potential

5 steps

what is step 1 of action potential

excitation stimulus is received

what is step 2 of action potential

depolarization results in an increase of membrane charge

when does a neuron fire

passes the threshold

what is the threshold the action potential needs to exceed

-50mV to -55mV

what is step 3 of action potential

rapid depolarization to +30mV sends the signal down the axon of then neuron

what is step 4 of action potential

quick repolarization results in over shooting the resting membrane potential

when does rapid repolarization occur

in hyperpolarization

what is step 5 in action potential

return to resting potential

what is important to note about step 5

neuron cannot fire again until the refractory period is over and resets

what period can the neuron fire again due to a strong stimuli

relative refractory period

does the absolute refractory period have a additional signal

No

what is important to remember about action potentials

weak stimuli do not relay a signal if it doesn’t cause depolarization past the threshold

what does the idea of the threshold create

All or None principle

Ion channels types

passive/leakage, chemically gated, voltage gated, mechanically gated

passive/leakage channels

always open

chemically gated channels

open when specific substances binds

voltage gated channels

open in response to membrane potential

mechanically gated channels

open in response to physcial deformation or receptors

Chemical vs Electrical gradient

ions will flow based on concentration (chemical) and towards the an opposite charge (electrical)

what does chemical vs electrical gradient creates

electrochemical gradient

what are the ions that drive action potentials

sodium potassium pump, sodium, potassium, and calcium channels

what do pumps create that allow the channels to fuel the process

electrical potential

how does action potentials move down the axon

like waves