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Flashcards in introduction to nervous system Deck (21):

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

1. action potential arrives at axon terminal of pre-synaptic cell, depolarising the presynaptic membrane
2. depolarisation opens voltage gated channels, triggering an influx of Ca2+ ions
3. the elevated Ca2+ concentration causes synaptic vessels to migrate towards and fuse with the presynaptic membrane
4. vesicles release neurotransmitter into the synaptic cleft via exocytosis (chemical messenger)
5. neurotransmitter diffuses across synaptic cleft
6. 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)


what is a satellite cell

- similar to astrocytes, PNS, surround neuron cell bodies


what is an oligodendrocyte

- provide same functionality as insulation on household electrical wire
- form myelin sheath around axons in CNS (insulation, protection), shorter processes


what is a Schwann cell

- forms myelin, surround peripheral nerve fibres
- not attached to one another (nodes of ranvier
- enhance / speed up signal)


describe the function / importance of the myelin sheath

- segmented protein-lipid sheath around long / large diameter axons
- protect and electrically insulate axon, increase speed or nerve impulse transmission
- schwann / oligodendrocytes: wrap around axon many times, concentric layers
- nodes of ranvier: gaps in between myelin sheath, speed up action potential


what is multiple sclerosis

- auto immune disease (destroys myelin sheath in CNS)
- difficulty walking, loss of coordination, visual / speech disturbances, weakness, loss of muscular control, urinary incontinence
- myelin sheath = nonfunctional sclerosis, shunting / short circuiting of nerve impulses, impulse conduction slows / ceases


what is an astrocyte

- support and brace neurons, help determine capillary permeability
- important for BBB, guide migration of young neurons, - collect nutrients in blood and send to neurons, most abundant