Nervous tissue Flashcards
overview of nervous system:
network of specialised cells for communication btw host and environment
- regulates body functions
- maintains homeostasis (helped by endocrine system)
- responsible for all behaviours, memories, movement
list basic functions:
sensory, integrative, motor
sensory:
sense changes in internal/external environments through sensory receptors
- sensory (afferent) neurons
integrative:
process/ store sensory info, make decisions regarding appropriate responses
- association/ interneurons
motor:
responds to stimuli by initiating action
- motor (efferent) neurons
list parts of CNS
central nervous system:
- brain
- spinal cord
list parts of PNS
peripheral nervous system:
- cranial nerves
- spinal nerves
- ganglia
- plexuses
- receptors
3 types of PNS
- somatic nervous system
- autonomic nervous system
- enteric nervous system
list two categories of cells in nervous system:
neurons, neuroglia (glial cells)
general features/ function: neurons
functional unit of nervous sytem
- propagates electrical impulses
- 3 main types: multipolar, bipolar, unipolar
features/ function: neuroglia
supportive cells
- 6 major types
(4 in CNS, 2 in PNS)
main parts of neurons:
dendrites (afferent)
cell body (integration)
axon (efferent)
features/ function: dendrites
RECEIVING signals from other neurons (less: intergrating)
- typically many dendrites with numerous branches
- diameter tapers away from cell body
- not myelinated
- passively conduct graded potentials from synapses -> towards cell body
features/ function: cell body
soma or perikaryon
- variable in size/ shape
- INTERGRATING signals
- cytoplasm has many organelles
organelles of cell body:
nucleus, nissl bodies (ER), golgi apparatus, mitochondria, microtubules
features/ function: axons
PROPAGATING signals from neuron-neuron
- 1 axon per neuron, relatively few branches (exc. near terminal end)
- uniform diameter entire way
- often myelinated, increase conduction velocity
- propagates action potentials away -> cell body toward -> synapses at axon terminal
features/ function: synapse
junction btw two neurons/ neuron and effector organ
- electrical
- chemical
postsynaptic potentials in other neuron/ organ:
- excitatory
- inhibitory
list different classifications of neurons: and why?
based on no. of structures directly attached to cell body:
unipolar
bipolar
multipolar
features: multipolar neuron
most common
- cell body btw many dendrites
- axon
features: bipolar neuron
- cell body middle
- dendrite, axon
features: unipolar neuron
sensory neuron
- one structure (axon)
trigger zone:
needs to be activated from multiple dendrites of same signal to then pass stronger signal down axon
list glial cells in PNS:
schwann cells
satellite cells
similar functions to glial cells in CNS
list glial cells in CNS
oligodendrocytes
astrocytes
microglia
ependymal cells
similar functions to glial cells in PNS
features/ function: Oligodendrocytes
found in CNS
- produces myelin
- 1 cell has many processes, wraps myelin around multiple axons
features/ function: Schwann cells
found in PNS
- produces myelin
- 1 cell forms myelin around 1 segment of 1 axon
features/ function: myelin
80% lipid, 20% protein
- electrical insulation of axon
- increases velocity of impulse propagation
- larger diameter axons have thicker/ more effective myelin sheaths (up to 100s of layers)
- provides track for regrowth to occur
features/ function: astrocytes
found in CNS
- most abundant cell in CNS
- structural/ metabolic support
- maintains extracellular chemical balance
- principal role in nervous system repair
features/ function: satellite cells
found in PNS
- flattened cells surrounding neuron cell bodies within ganglia
- similar role to astrocytes (metabolic/ structural support)
aka: mantle cells, amphicytes
features/ function: ependymal cells
found in CNS
- lines ventricles of brain/ central canal of spinal cord
- columnar/ cuboidal epithelium
- ependymocytes: in choroid plexuses produce CSF
- ciliated ependymocytes: help circulate CSF
features/ function: microglia
found in CNS
- from precursor cells in bone marrow (monocyte)
- similar to macrophages elsewhere in body
main active immune defence in the CNS:
- scavenging
- phagocytosis
- cytotoxicity
- antigen presentation
- promotes repair
list layers of cerebral cortex:
I: molecular layer II: outer granular layer III: outer pyramidal layer IV: inner granular layer V: inner pyramidal layer VI: layer of pleiomorphic cells
distinguish layers: cerebral cortex
no boundaries, hard to distinguish
list layers of cerebellar cortex:
I: molecular layer
II: Purkinje cell layer
III: granular cell layer
list connective tissue associated with peripheral nerves:
endoneurium, perineurium, epineurium
endoneurium:
surrounds each axon
perineurium:
forms complete sleeve around bundle of axons
epineurium:
dense sheath covering entire peripheral nerve
features in molecular layer (cerebral cortex):
contains relatively few nerve cell bodies
- composed largely of dendrites, axon terminals, neuroglia
features in outer granular layer (cerebral cortex):
typically contains very small cells (granule cells)
features in outer pyramidal layer:
contains cell bodies of small pyramidal cells
features in inner granular layer (cerebral cortex):
-
features in inner pyramidal layer:
contains cell bodies of large pyramidal cells
features in layer of pleiomorphic cells:
contains cells of assorted size and shape
features in molecular layer (cerebellar cortex):
dendrites of Purkinje cells, axons of granule cells, neuroglia
features in Purkinje cell layer:
-
features in granular cell layer (cerebellar cortex):
packed with nuclei of many cerebellar granule cells
