Cells of the Nervous System Flashcards
Molecules
two or more atoms held together by a chemical bond
4 families of molecules
- simple sugars
- fatty acids
- amino acids
- nucleotides
Neurons
responsible for sending and receiving neurotransmitters
Classification of neurons
- shapes/number of appendages
- function (afferent/efferent)
- direction of action potential
afferent communication
Sensory signals from PNS to CNS
bottom-up
from body to brain
efferent communication
Motor signals from CNS to PNS
top-down
from brain to body
Motor/Efferent Neurons
from the CNS to PNS
- final neurons in action sequence
- 2 types are alpha and gamma
Afferent/Sensory
from sensory receptors in body towards the CNS
- first neurons in sensory sequence
- “arriving”
Interneurons
transmit impulses between other neurons
- determine place & time of response
Components of neuron (also study diagram)
- cell body/soma with nucleus
- axon
- axon terminal
- dendrite
Cell body (SOMA)
- contains genetic info
- maintains neuron integrity/structure
- regulates production of proteins/lipids
- holds nucleus
- ER, Golgi apparatus, mitochondria
Axon
- long, thin, spindly (susceptible to damage)
- action potentials generated here
- covered in myelin
Axon Region includes
Axon Hillocks
Axon telodendria
Axon terminals
Axon Hillocks (initial segment)
the ‘manager’ summing total inhibitory/excitatory signals to determine if action potentials release
Axon telodendria
end branches of an axon
Axon terminals
swollen end of telodendra, transmits message to other cells via neurotransmitters
Dendrites
- receives data from other neurons
- collects/stores incoming info from axon terminals
Cytoplasm
jelly like fluid found within cell body - but outside the nucleolus
- function in transport
- maintain cell shape
- protect/host metabolic process
Similarities of Neurons to other cells
- membrane
- nucleus
- cytoplasm, mitochondria, organelles
Differences of Neurons to other cells
- specialized projections
- communicate with each other thru electrochemical process
- can be long (several feet)
2 phases of communication
Electrical and Chemical
Electrical phase
dendrites and axons
Chemical phase
neurotransmitters and synaptic cleft
Impulses of neurons
Electric currents/action potentials
- excitatory (go)
- inhibitory (no go)
Synapses
tiny gaps where specialized parts of 2 neurons allow for chemical communication
- electric signals within neuron
- chemical signals between neurons
Neuronal Communication
presynaptic neuron sends the info
postsynaptic neuron receives info
Action potential
created electrical signal during neuronal communication
- triggers release of neurotransmitter
- chemical moves into synaptic cleft
Neurotransmitter binds to..
receptor on postsynaptic neuron, causes ion channels to open
Opening of ion channels allows
charged particles to cross membrane of that neuron causing electrical charge to form in postsynaptic neuron
Polarization
different electrical charges inside vs. outside of neurons
- inside (at rest) about -65 aka resting membrane potential
- outside is neutral (zero)
Hyper polarized
- resting membrane potential becomes more negative
- less likely to generate/send a signal
Depolarized
- resting membrane potential becomes better heading toward positive (still negative numbers)
- more likely to generate/send signal
Two different gradients of membrane potential
- Electrical gradient
- ion concentration
Electrical gradient
ions want to decrease their concentration gradients
- positives move towards negatives to make the ‘area’ more positive
Ion concentration
move down concentration gradient from high to low
3 ions to understand
Sodium (Na+)
Potassium (K+)
Calcium (Ca2+)
Inside cell more K
Outside cell more Na and Ca
Passive transport
When ion channels open, ions move freely based on their tendency for concentration gradient
Ionotropic (Ligand-gated)
opens in response to neurotransmitters, binds to receptor in CNS & PNS
Mechanically gated
opens to mechanical displacement of cell membrane
Voltage gated
opens when electrical charge reaches threshold
Excitatory Postsynaptic Potential
neurotransmitter opens sodium channel, sodium moves into neuron
- potential to cause depolarization
Inhibitory Postsynaptic Potential
neurotransmitter opens potassium channel, potassium moves out of neuron
- beings to hyperpolarize
Battle between EPSP and IPSP
summation: if enough Na+ channels are opened and threshold reached -50, action potential is created, signal sent down axon
- if threshold not met, neuron doesn’t fire
Exocytosis
- release from presynaptic neuron axon terminals
- neurotransmitter spills into synaptic cleft and binds to receptors of postsynaptic neuron
- either inhibitory or excitatory
Resting potential
electrical difference between inside and outside membrane when neuron is not excited
Action potential
rapid rise (depolarization) in potential follows by return to resting state
graded potential
localized, small depolarizations could AP if meet threshold
Saltatory conduction
rapid method where nerve impulses move down myelinated axon
- exception occurs at nodes of ranvier
- jumping of current from node to node
- nodes contain Na&K channels
- myelin allows rapid movement of signal
What happens at the synapse
- action potential reaches bouton terminal
- release of chemical transmitter substance from synaptic vesicles
- causes next neuron to change charge
Intellectual Disability
formerly known as mental retard.
- IQ under 70
- occurs before 18
- substantial limitations in funciton
- dendritic spine differences (long, thin)
Brain tumors
Benign (non-cancer) 44%
Malignant (cancer) 56%
origin is primary brain tumors or metastatic brain tumors
Types of malignant brain tumors
Neuromas (neurons)
Gliomas (glial cells)
- astrocytoma
- oligodendroglioma
- schwannoma
Amyotrophic Lateral Sclerosis (ALS)
Lou Gehrig’s Disease
- Motor neuron disorder (MND)
- Withering of upper & lower M.N
- onset 40-60 y/o
no cure
Multiple Sclerosis (MS)
“multiple scarring”
- Autoimmune disorder (unkown)
- Myelin around axon is damages
No cure
Myasthenia Gravis (MG)
“grave muscle weakness”
- Neurological disease of neuromuscular junction
- Affects women in 30s men in 50s
- Weakness and fatigue
NO CURE
Guillain-Barre Syndrome
- rapid, progressive demyelinating PNS
- most common is autoimmune
- progressive paralysis then recover
- most experience complete recovery
No cure
