Neurophysiology Pt1 Intro Flashcards
Describe the subdivisions of the CNS.
CNS -> brain: receives & processes sensory info, initiate responses, store memories, generate thoughts & feelings
CNS -> spinal cord: conduct signals to & from brain, controls reflex activities
Describe the subdivisions of the PNS.
PNS -> sensory (afferent): brings info to CNS from receptors in peripheral tissues/organs
PNS -> motor (efferent): carries motor commands from CNS to peripheral tissues/systems
Sensory -> visceral sensory: provides info about organs (visceral receptors & sensory neurons)
Sensory -> somatic sensory: provides info about position, touch, pressure, pain, temp (somatic receptors & sensory neurons)
Motor -> visceral motor: provides autonomic regulation of smooth muscle, cardiac muscle, glands, adipose tissue (involuntary)
Motor -> somatic motor: controls skeletal muscle contractions (voluntary)
Visceral motor -> sympathetic: fight/flight
Visceral motor -> parasympathetic: rest/digest
*PNS= connect CNS to limbs/organs & contain receptors, nerves, ganglia outside CNS
What are the 7 parts that make up a neuron?
- Dendrites = info receiving area of cell membrane
- Cell body, soma, pericaryon = contain organelles
- Axon = info carrying extension of cell membrane
- Axon hillock/trigger zone = axon & AP origin
- Presynaptic terminal = end of axon; transmit info
- Myelin sheath = enhance speed of info transfer
- Node of ranvier = gaps in myelin sheath
Describe a neuron.
neurons + neuroglia = nervous system
Neuron aka “nerve cells”:
-info processing
-don’t divide when mature
-neuronal death injury = change structure/function
Describe a synapse.
Synapses:
-communicate with neurons, muscle fibers, and glands via synapses
-AP travels along axon
Describe a myelin sheath.
Myelin sheath:
-modified PM
-wrapped around axon (spiraled)
-originate & part of = schwann cells [cytoplasm forms rings on sheath] & oligodendrites in CNS
-periodic interruptions = nodes of ranvier (imp for function of myelin)
-facilitates conduction (electrical conduction)
-allows saltatory conduction of impulses (AP jumps from node to node) therefore depol is more rapid than in unmyelinated
-conduction velocity is proportional to diameter
-lg axons = long internodes & faster conduction velocities
-sm axons = <1um diameter not myelinated (slower than lg ones)
-conserve space & energy
-if nerves not myelinated = huge spinal cord
Describe the 4 structures of neurons.
- Multipolar
-most common
-1 axon & many dendrites
-length & arrangement vary - Bipolar
-2 processes
-1 axon & 1 dendrite - Pseudo-unipolar
-single stem process that bifurcates into 2
-1 goes to PNS & other to CNS - Unipolar
-common in insects
Describe the functions of neurons (3).
- Sensory/afferent
-send info from receptors in sensory organs to CNS
-most are pseudo-unipolar - Inter neurons/association
-found in CNS
-connects motor & sensory neurons
-usually multipolar or bipolar - Motor/efferent
-send info from CNS to effector organs (muscle/glands)
-multipolar
Where are glial cells located?
- CNS
-microglial
-Astrocytes
-oligodendrites
-ependymal - PNS
-Schwann cells
What are glial cells?
-smaller than neurons
-NO axons, dendrites, AP, synaptic interactions, electrical signaling
-fills space in NS not occupied by neurons/blood vessels
-more numerous than neurons in nervous tissue
-can divide
-produce myelin sheath & synapses
-modulate growth of developing/damaged neurons
-buffer extracellular conc. Of K+ & neurotransmitters
-immune responses of NS
What are the 5 types of glial cells?
Schwann cells, Astrocytes, microglia, oligodendrocytes, ependymal cells
Describe oligodendrocytes.
-hold more than 1 axon at a time
-provide support to axons & neurons in CNS
-numerous processes that extend to adjacent axons to form myelin
-myelinate axons >1um in diameter
-myelin sheath = white matter in brain
-gray matter = increased # of soma
(Ex. Cerebral cortex)
Describe ependymal cells.
-cover ventricles of brain, central canal of CNS, & choroid process in 4th ventricle of medulla oblongata
-create CSE
Describe Schwann cells.
-arranged side by side along axon
-each cell forms internodes of myelin sheath of various lengths
-support to axons of PNS
-similar to oligodendrocytes
-produce myelin in axons >1um
Describe microglia.
-brain immune cells
>macrophages = phagocytosis to clear debris
>release NO to prevent viral replication
-protect brain against injury/infection
-develop brain -> destroy unnecessary synapses
