Nervous System Flashcards
What does the nervous system look like?
a network
What are the two functions of the nervous system?
communication and control
What are the nervous system processes?
- collects information
- processes information
- Initiates response
The nervous system uses what to collect information?
receptors
Where does the nervous system process information?
in the control center
Where are responses/commands sent in the nervous system?
to the effectors
What are the only kinds of effectors?
muscles and glands
What is the organization of the nervous system?
the central and peripheral nervous system
What is the function of the central nervous system?
process information
What components make up the central nervous system?
the brain and spinal cord
What is the function of the peripheral nervous system?
transmit information
What are the components of the peripheral nervous system?
nerves and ganglia
What kind of nerves come from the peripheral nervous
system?
sensory and motor nerves
What are the two types of cells in the nervous system?
neurons and glial
Neurons
- basic functional units of the nervous system
- excitable calls that transmit signals
Glial
non-excitable cells
Glial functions
protect and support neurons
Neurons have extreme longevity but are what kinds of cells?
amitotic
Amitotic
lost the ability to divide
Nerves
bundles of neurons
Ganglia
cluster of neuron bodies
What glial cells are in the central nervous system?
- astrocytes
- ependymal
- microglia
- oligodendrocytes
Astrocytes
star-shaped cells that connect capillary walls with neurons
Astrocytes functions
- establish blood-brain barrier
- form supporting networks
- assist neuronal development and repair processes
- communicate with neurons and adjust their activities
Ependymal cells
- ciliated epithelial cell that line internal cavities
Ependymal cell function
involved in the production and movement of cerebrospinal fluid (CSF)
Microglia
small cells with slender branches that wander the CNS
Microglia function
phagocytize (engulf) infectious agents and debris
Oligodendrocytes
large cells with slender extensions that wrap around the axons
Oligodendrocyte function
insulation of axons in a myelin sheath that speeds up the movement of signals
What cells are in the peripheral nervous system?
satellite cells and neurolemmocytes
Satellite cells
surround neuronal cell bodies in a ganglion
Satellite cell functions
regulate the exchange of nutrients and waste products
Neurolemmocytes (Schwann cells)
wrap around axons to form myelin sheath for faster signal propagation
Myelination
is the process by which parts of an axon become wrapped in the myelin sheaths composed of repeating layers if glial cell plasma membrane with proportions of lipids.
The lipids in myelin sheath does what?
gives glossy white appearance and insulates axon
Myelinated axons perform what?
saltatory conduction
Saltatory conduction
nerve impulse/signal skips myelinated areas
Myelinated axon nerve impulses speed up to what?
150 m/c
Unmyelinated axons transmit nerve impulse through what process?
continuous conduction
Unmyelinated axon nerve impulses speed up to what?
2 m/c
What are the three parts of a neuron?
- dendrites
- body
- axon
Dendrites
short branches attached to the body
Dendrites functions
membrane receives stimuli
Body =
soma
Body characteristics
- unnucleated
- many ribosomes (gray)
Body function
membrane receives stimuli
Axon characteristics
- long branch
- axon hillock
- axon terminals
Axon fucntion
passes signals to nervous system, muscular system, or glands
Axon: nerve
a bundle of axons enclosed in 3 layers of CT:
- endoneurium
- perineurium
- epineurium
What are the two neuron classifications?
structural and functional
What are the four structural classifications of a neuron?
- multipolar
- bipolar
- unipolar
- anaxonic
What are the three functional classifications of a neuron?
- sensory
- motor
- interneurons
Sensory neuron pathway
receptors to CNS
Motor neuron pathway
CNS to effectors
What is another name for sensory neurons?
afferent
What is another name for motor neurons?
efferent
What is another name for interneurons?
association
What are neuron membranes capable of?
initiating, processing, and transmitting signals
What is the resting membrane potential of neurons?
-70 mV
What three channels are responsible for the RMP of neurons?
- Na-K pump
- K+ channels
- Na+ leak channel
The Na+ leak channel is only present in what kind of structure?
neurons
Depolarization
cell with a less negative charge than the outside
Hyperpolarization
cell with a more negative charge than the outside
What are the properties of a neuron?
- lipid bilayer +( lipid and carb)
- semi-permeable
- at rest the membrane is polarized = -70mV
- Concentration gradient for Na+, Cl-, and K+
- neurons use their membranes to establish synapses
What happens if gated ion channels open?
ions diffuse (H to L) causes intentionally altered RMP
What happens when Na+ channels open?
- sodium diffuses in
- the cell becomes less negative causing depolarization
What happens when K+ channels open?
- potassium diffuses out
- the cell becomes more negative causing hyperpolarization
What happens when Cl- channels open?
- chloride diffuses in
- the cell becomes more negative causing hyperpolarization
Synapse
is a site across the which neuron passes a signal to another neuron, muscle cell, or gland cell
What are the characteristics of a chemical synapse?
- uses neurotransmitters
- slow but common
- may excite or inhibit the postsynaptic cell
What are neurotransmitters?
organic compounds (=100) produced by neurons in order to transmit a signal
What are two types of neurotransmitters?
acetylcholine and norepinephrine
Acetylcholine effect
- excites skeletal muscles
- inhibits cardiac muscle
Norepinephrine effect
- excites cardiac muscle
- inhibits digestive system
What are the two methods used in the elimination of the neurotransmitter?
Degradation and reuptake
Degradation is done by what?
enzymes
Reuptake is done by what?
transporters
What are the 4 functional segments of a neuron?
- receptive
- initial
- conductive
- transmissive
Receptive: part of neuron
dendrites and cell body
Initial: part of neuron
axon hillock
Conductive: part of neuron
axon and terminals
Transmissive: part of neuron
synaptic knobs
Receptive: function
receives stimuli (input)
Initial: function
action potential may be initiated
Conductive: function
conducts action potential
What is another word for conducts?
propagates
Transmissive: function
neurotransmitter excites or inhibits a postsynaptic cell
What is the most common stimulus?
neurotransmitters released from another neuron
What events occur in response to neurotransmitters release?
- NT binds to the specific receptor
- chemically gated ion channels open temporarily
- ions diffuse (H to L)
- RMP is slightly altered
Graded potential
a small, short- lived deviation from RMP
What happens to the membrane during graded potential?
membrane becomes slightly depolarized or hyperpolarized
The degree or grade of graded potential is dependent on what?
the strength of the stimulation
What is another name for graded potential?
postsynaptic potential
What are the two kinds of postsynaptic potential?
EPSP and IPSP
Excitatory PSP
- a neurotransmitter opens a Na+ channel
- Causes slight depolarization
- closer to the threshold
Inhibitory PSP
- a neurotransmitter opens K+ and Cl- channel
- causes slight hyperpolarization
- away from the threshold
Where are EPSPs and IPSPs generated?
receptive segment
Where does summation/processing of EPSPs and IPSPs happen?
Initial segment
What law does summation follow?
all or none law
What happens if numerous excitatory stimuli arrive to the receptive segment?
- large amount of Na+ enters the cytoplasm and reach the axon hillock
What happens if the threshold is reached in the axon hillock?
voltage-gated channels are triggered to open in the axon hillock
What is initiated in the initial segment?
action potential
What happens if the threshold is not reached?
no action potential
What happens in once action potential is initiated?
once initiated, action potential needs to be conduction (propagation) along the axon.
What happens in the conductive segment?
axon membrane undergoes a wave of depolarization, followed by repolarization.
What is the goal of depolarization?
to spread the action potential
What structure does depolarization?
voltage-gated Na+ channel
What is the value of action potential?
+30 mV
Nerve impulse
the consecutive opening of voltage gated Na+ channels
What is the goal of repolarization?
to return the membrane to RMP after the AP passes
Repolarization is done by what structure?
voltage-gated K+ channels
What is the process of repolarization?
- threshold is reached -55mV
- voltage-gated K+ channels open slowly
- K+ diffuses out
- membrane becomes more negative
- channels close too slowly
- membrane becomes hyperpolarized
- RMP is reestablished by Na+/K+ pumps
What happens when AP arrives to the synaptic knob?
- voltage-gated Ca2+ channels open
- Ca2+ diffuses in
- synaptic vesicles release neurotransmitter into the synaptic cleft
- neurotransmitter diffuses and binds to the receptors on the postsynaptic cell
- postsynaptic cell is activated or inhibited