Nervous Tissue Flashcards
what is the structural and function unit of the nervous system
a neuron
what is the function of a neuron
to relay signals from internal and external environment
where are most neuron cell bodies located
the CNS
what parts of neurons can divide
regeneration of axons are possible. neurons in olfactory areas and hippocampus can divide
what are the basic cell types of nervous tisxue
neurons and supporting cells
what is the function of supporting cells
provide physical support and protection, electrical insulation and metabolic exchange
what are the 3 categories of supporting cells
neuroglia in CNS, Schwann cells in PNS, satellite cells in ganglia
what is a soma and what does it contain
it is the cell body of the nucleus and it contains the nucleus and cytoplasm
what is another word for the cytoplasm of the soma of a neuron
perikaryon
what is the nissal substance in a neuron made of
rough ER
what is the neurilemma
plasma membrane surrounding the neuron cell
what are the contents of a neuron
soma, nissl substance, neurilemma, melanin, lipofusin
what are the characteristics of a neuron
1 or more dendrites and a single axon
what is the function of dendrites
receive stimuli from other neurons or environment (AFFERENT)
what is the function of an axon
transmits stimuli to other neurons or effector cells (EFFERENT)
what does the axon arise from
the axon hillock
what is the axon hillock
terminates in distal swelling called the terminal bouton
what is axonal transport
movement of products down the axon
what are the types of axonal transport and what do they carry
-slow axonal transport: cytoskeletal elements
-fast axonal transport: membrane bound organelles
what is anterograde transport and what protein does it use
transport from cell body down axon uses kinesin
what is retrograde transport and what protein does it use
transport from axon to cell body uses dynein
what is a mutli polar neuron
several dendrites surrounding cell body located at the end , single axon, most common
what is a bipolar neuron
single dendrite opposite the axon. cell body is in the middle of the axon, dendrites are at the end
what is a unipolar axon
no dendrites on cell body, axon only
what is a pseudounipolar axon
single dendrite and axon fuse, cell body is off to one side
where are sodium and chloride concentrations high
outside the cell
where is potassium concentration high
inside the cell
describe the steps of depolarization of a membrane
- AP arises in cell body as a result of an afferent stimulus
-causes regions of plasma membrane to depolarize - voltage gated Na channels open and Na rushes into the cell
- voltage gated K leak channels open and K rapidly leaks out of the cell
-membrane potential gets closer to zero
what happens inthe absolute refractory period
Na channels close and cant reopen, nerves are unresponsive to stimuli
what happens in the relative refractory period
only a strong stimulus can initiate depolarization
what marks the end of the refractory period
when Na channels close and voltage gated K channels also close
what are synapses
specialized junctions between neurons
what are neuromuscular junctions
specialized junction between neuron and effector cell
what is entrainment
“muscle memory”, the more a pathway is used, the easier it is to access
what is the terminal bouton separated from the effector cell by
the synaptic cleft
what does the terminal bouton contain
mitochondria and synaptic vesicles containing neurotransmitters
what are signaling molecules released from
presynaptic membrnae
what 2 neurotransmitters are used in the PNS
acetylcholine and norepinephrine
what does the sympathetic nervous system use as a neurotransmitter
noradrenaline (norepinephrine)
what are sympathetic neurons called
adrenergic neurons
what are parasympathetic neurons called
cholinergic neurons
what do parasympathetic neurons use as a neurotransmitter
acetylcholine
what do vesicles on the post synaptic membrane contain
hydrolytic and oxidative enzymes
what do hydrolytic and oxidative enzymes do in the post synaptic membrane
degrade NT after binding to postsynaptic membrane and thus inactivate it during consecutive impulses to prevent continuous stimulation
what types of axons does peripheral nervous tissue have
afferent and efferent axons of somatic or autonomic nerves
where are cell bodies of peripheral nerves located
in CNS or ganglia
what do peripheral nerves contain
fasicles
what are fascicles
a bundle of axons
what are schwann cells derived from
neural crest
what do schwann cells do
provide metabolic support and electrical insulation
describe non myelinated nerve axons
several axons lie in channels within a schwann cell surrounded by a single layer of neurilemma
describe a myelinated nerve axon
insulated by many concentric layers of plasma membrane from many schwann cells
what forms the myelin sheath
the multiple layers of plasma membrane
what are nodes of ranvier
gaps in myelin sheath between adjacent schwann cells. responsible for saltatory conduction
where does membrane depolarization occur
only at nodes, not beneath schwann cells
why is it helpful to the cell that membrane depolarization only occurs at nodes
it is faster, conserves electrolytes and is energy efficient
what are myelinated nerves in the CNS surrounded by
oligodendrocytes
describe a myelinated neuron in the CNS
surrounded by an oligodendrocyte. surrounds several nerves with more than one layer of plasma membrane
describe the relationship between rate of conduction and the diameter of the axon
the larger the axon the faster the conduction rate
what does the endoneurium surround
individual axon and schwann cells
what does the perineum surround
fasicles
what does the epineurium surround
several fasicles
what do blood vessels follow
the epineurium and perineurium
where are preganglionic and postganglionic neurons found
in ANS connecting CNS to viscera
where are the cell bodies of preganglionic neurons found
grey matter of brain and cord in CNS
where are the cell bodies of postganglionic axons found
ganglia
what are satellite cells and what do they do
surround soma, derived from neural crest and provide structural and metabolic support
where are sympathetic ganglia located
vertebral column
where are parasympathetic ganglia located
in or near the effector organ
what makes up a sympathetic ganglia
prevertebral and paravertebral ganglia
where are prevertebral ganglia located
anterior to spine
where are paravertebral ganglia located
sympathetic trunk
