introduction to nervous system Flashcards
what are the functions of the nervous system
- sensory: gather information by sensory receptors about internal / external change
- integration: interpretation of sensory, CNS, determine response based on stimuli
- motor: activation of effector organs, produce response, release of hormones
what is the central nervous system
- F: integrative and control centre of NS, giant ‘switchboard’, interpretation / analysis of stimuli, collect information
- S: brain and spinal cord (encased in bony structures)
what is the structure and function of the peripheral nervous system
- S: all nervous structures outside of CNS, spinal nerves (31) and cranial nerves (12)
- F: nerves with relay responses between outlying regions of body and CNS
what are the divisions of the peripheral nervous system
sensory (afferent): somatic (impulses from skin, skeletal muscles, joints), visceral (impulses from visceral organs, intestine, BV)
motor (efferent): transmits impulses from CNS to effector organs
- somatic: voluntary, external environment, single neuron, releases ACh at effector (skeletal), stimulatory (+), heavily myelinated axons
- autonomic: involuntary, internal environment, two neurons, releases ACh or NE at effector (smooth / cardiac, glands), stimulatory (+) / inhibitory (-) (dependent on neurotransmitter), lightly myelinated pre-ganglionic axons, synapse at ganglion, un-myelinated post-ganglionic axon OR attach to adrenal medulla / BV
describe in depth the autonomic nervous system and its divisions
- innervate smooth / cardiac / glands, ensure optimal support for bodies activities (homeostasis)
- dual innervation: all visceral organs served by both sympathetic / parasympathetic - opposite
- S: fight or flight, mobilises the body during activity
- PS: rest and digest, promotes maintenance of activities, conserves bodies energy
describe the histology of nervous tissue
- neurons, excitable, transmit signals, basic / structural units of NS
- gray: cell bodies, un-myelinated fibres
- white: myelinated
- neuroglia: supporting cells, CNS (astrocytes, microglia, ependymal, oligodendrocytes), PNS (satellite cells, schwann cells)
describe the structure and special characteristics of nerve cells
- long lived (100+ years)
- amitotic (dont divide)
- high metabolic rate
- plasma membrane (cel to cell interactions, electrical signalling)
- dendrites (communication, receive messages, carry to cell body)
- axons (long, unbranched, carry away from cell body)
- axon hillock (generate current, spread to axon terminals)
- myelin sheath (fatty white, surround axon, schwann cells and nodes of ranvier)
what are the functional classification of neurons
- sensory (afferent / receptor): transmit impulses from sensory receptors toward the CNS
- motor (efferent / effector): carry impulses from the CNS to effectors (muscle / gland)
- interneurons (association / relay): shuttle signals through CNS pathways; most are entirely within the CNS, link between sensory and motor
what are the structural classification of neurons
- multipolar: more than two prominences arising from body of cell (interneurons / motor neuron)
- bipolar: two prominences arising from body of cell (eyes, ears, nose)
- unipolar: one prominence arising from body of cell, (sensory neuron)
describe the two different pathways motor neurons take
- direct: pyramidal, precise and voluntary movements
- simplest: two sets of neurons, upper motor and lower motor, extend from CNS to PNS to supply skeletal muscles
what is / are the 3 locations a synapse can occur
- neuronal junction, electrical and chemical, junction, mediates info transfer
- axosomatic: axon terminals / cell body
- axodendritic: axon terminals / dendrites
- axoaxonic: axon terminals / axon hillock
describe the steps in a synapse
- action potential arrives at axon terminal of pre-synaptic cell, depolarising the presynaptic membrane
- depolarisation opens voltage gated channels, triggering an influx of Ca2+ ions
- the elevated Ca2+ concentration causes synaptic vessels to migrate towards and fuse with the presynaptic membrane
- vesicles release neurotransmitter into the synaptic cleft via exocytosis (chemical messenger)
- neurotransmitter diffuses across synaptic cleft
- neurotransmitters bind to ligand gated ion channels in the postsynaptic membrane and generate an electric current to depolarise the postsynaptic neuron
what are neuroglia cells
- CNS (astrocytes, microglia, ependymal cells, oligodendrocytes)
- PNS (satellite cells and schwann cells)
what is a microglia cell
- differentiate into phagocytic cells
- mesodermal origin, proliferate and differentiate into phagocytic cells in instance of tissue damage
- derived from cell line (rise to monocytes), defensive
what is an ependymal cell
- ventricles of the brain and central canal lining
- cuboidal, tight junctions, cilia on top
- filtrate and promote / control exchange of substances between CSF and CNS (nervous tissue)