nervous system - neurons Flashcards
what are neurons?
specialised cells to send and receive nerve impulses
what are neuroglia?
cells that have a support function
provide insulation and nutrients
may send and receive impulses
how are all the organs in the human body formed?
four types of tissue combine
what does nervous tissue do?
allow you to sense and respond to things
what do nervous tissue cells do?
they are specialised for receiving and sending information
where is the central nervous system?
made up of the brain and spinal cord
where is the peripheral nervous system
cranial nerves, spinal nerves, ganglia, peripheral nerves, and neuromuscular junctions
what is the function of the cns?
awareness, movement, speech, receiving, processing, responding to sensory information
what is the function of the pns?
sending information from different areas of the body back to the brain, and carrying out commands from the brain to various parts of the body.
how is the peripheral nervous system further subdivided?
into an afferent sensory division and efferent motor division
what are the peripheral organs
nerves and ganglia
how does the sensory division of the pns transmit impulses?
from the peripheral organs to the cns
how does the motor division of the pns transmit impulses?
from the cns to the peripheral organs
how is the motor division further subdivided
into a somatic motor division and an autonomic motor division
what does the somatic motor division do?
serves skeletal muscle
what does the autonomic motor division do?
serves smooth muscle, cardiac muscle and glands
what does the nervous system do?
contains sensory receptors which detect changes in the internal and external environment of the body
how does the nervous system send information?
via impulses
what are impulses?
a network of cells that use electrical signals
what happens when impulses are used?
responses are initiated to changes in the body, allowing the nervous system to maintain homeostasis
what does motor function do?
carries out effect
what does the integrative function?
decides response
what does the sensory function do?
detects stimulus / informs cns
what are the effectors of the somatic nervous system?
skeletal muscles
what are the effectors of the autonomic nervous system?
cardiac muscles, smooth muscle, glands
types of neuroglia
astrocytes
ependymal cells
microglia
oligodendrocytes
what is the function of astrocytes
found between neurouns and blood vessels (blood brain barrier)
regulate ion concentration in nervous tissue
multifunctional
what is the function of ependymal cells
cover the choroid plexus
line spaces in the brain (ventricles)
produce csf
what is the function of microglia
function as phagocytes
supportive function
what is the function of oligodendrocytes
form myelin in central nervous system
what is csf
cerebrospinal fluid: flows in and around the hollow spaces of the brain and spinal cord, and between two of the meninges
what is the node of ranvier?
exposed area of axon between myelin
gaps between neighbourign segments of the myselin sheath
what is the myelin sheath
a coating formed by schwann cells wrapped around the axon
what is an axon?
thin extension that carries impulse
what cells are axons of the peripheral nervous system associated with
neuroglia cells - schwann cells
what does the myelin sheath consist of
multiple layers of the cell membrane of neuroglia cells
what happens when schwann cells wrap around the axon
cytoplasm becomes the outermost wrapping of the cell
what is the neurilemma
the outermost wrapping of the axon containing organelled and nucleus
what are myelinated axons
axons with myelin sheaths
what are unmyelinated axons
axons without myelin sheaths
what is the cell body of a neuron
region that contains the nucleus
what is the dendrite of the neuron
branched receptive processes
what is the synaptic knob
enlarged structures that store and release neurotransmitters
what is myelin
multilayered lipid covering of axon
what type of nervous system tissue is formed by bundles of myelinated axons?
white matter
what is found within gray matter in the nervous system tissue?
unmyelinated axons, dendrites, neuron cell bodies, and synapses
what happens when an action potential arrives at the synaptic terminal
voltage gated calcium channels are opened
what neurotransmitter is released from the synaptic vesicles?
acetylcholine
When do ligand-gated sodium channels open?
When their ligand (acetylcholine) binds
what happens when sodium enters the sodium channels?
the membrane potential becomes more positive.
when will an action potential be produced?
if the membrane potential reaches threshold
What structure releases neurotransmitter molecules?
synaptic vesicles
how do nerve impulses occur?
ions moving through voltage gated ion channels in the plasma membrane
The interior of the cell membrane is more__________ than the outside of the cell membrane.
negative
What direction does the sodium-potassium pump move ions?
Sodium out of the cell and potassium into the cell
Following stimulation, what are the first channels to open?
sodium channels
what happens when sodium enters the cell membrane at the location of the sodium channel?
depolarisation
When potassium channels open, which way do potassium ions flow?
out of the cell
during an action potential what happens when potassium channels are opened?
repolarisation of the cell membrane
Following an action potential, activity of the __________ reestablishes the sodium and potassium ion distribution across the cell membrane.
sodium potassium pump
what does an action potential involve?
depolarisation
repolarisation
what is the steps of synaptic transmission?
- nerve impulse at axon terminal
- calcium ions enter
- exocytosis of neurotransmitter
- diffusion through synaptic cleft
- binding to receptor on post synaptic membrane
what happens during hyperpolarisation?
potassium channels are open
membrane potential actually dips lower than -70mV because the potassium channels do not close quickly enough.
how can the cell membrane of a resting neuron be described?
polarised
what is depolarisation?
the membrane potential becomes less negative than the resting membrane potential
when will the action potential only occur?
the membrane potential at the trigger zone reaches threshold level
what happens when threshold is reached?
voltage-gated sodium channels of the initial segment open briefly, allowing sodium to diffuse into the cell.
what happens when sodium ions enter the cell?
the cell membrane undergoes depolarization, with the membrane potential increasing to a peak of approximately +30mV.
what happens when the peak of the action potential is reached?
sodium channels close, and the voltage-gated potassium channels open, allowing these ions to diffuse out of the cell.
what happens when potassium ions leave the cell?
the membrane potential at that part of the membrane is reestablishing resting membrane potential. repolarization occurs
features of myelinated axon
faster impulse conduction
saltatory conduction
only nodes depolarise
features of unmyelinated axon
slower impulse conduction
entire surface depolarises
what is an excitatory neurotransmitter?
A neurotransmitter that causes the opening of sodium channels
brings the postsynaptic membrane closer to the threshold
what is an inhibitory neurotransmitter?
A neurotransmitter that causes the opening of potassium channels
causes membrane potential to move away from the threshold
What are examples of a neuropeptide?
Enkephalins and substance P
what are neuropeptides?
small proteinaceous substances produced and released by neurons through the regulated secretory route and acting on neural substrates.
how do neurons communicate chemically with eachother?
using neurotransmitters at a synapse
the release of neurotransmitters by the ________ is triggered by nerve impulses
presynaptic neuron
what happens when the neurotransmitter binds to the post synaptic neuron?
causes electrical changes in the membrane
