Nervous Tissue Ch 11 Flashcards
How is the nervous system organize ?
The cns ( brain and spinal cord, control center)
The pns ( cranial and spinal nerves , communication life for the rest of of body )!
List the functional division of pns
Sensory (afferet)
Visceral sensory ( skin, skeletal muscle, joints)
Somatic sensory division- visceral organs
Motor (effert) cns effectors
Visceral motor division- automatic nervous system
What are the types of effectors?
Sympathetic- fight /flight
Parasympathetic- resting/ digesting
Somatic motor division
Effector - skeletal muscle
What are the two types of cells found in the nervous system ?
Neurons - excitability nerve that transmit electrical nerve
Neurogial (glial) cell - supportive cell, sorruounds neurons
What are the 6 types of neurologial cell ?
Oligodendrocytes
Astrocytes -( most abundant)
Sclensis - damage neurons replace by harden mass of atroscytes
Ependymal cell- lines cavity and provides CSf
Microglia- formed by monocytes , concentrate in infection, trauma and stroke
What is oligodendrocytes?
Have processes that form myelin sheaths around cns nerve fibers
What are the fundamental properties of neurons
Excitability- response to change in body/environment call stimuli
Conductivity- produce traveling electric signals
Secretion- when signal reaches end of nerve fiber, a chemical neurotransmitter is secreted
What is the structure of a neuron?
Vast # of short dendrites ( receiving signals)
Cell body - soma
Rough ert ribosomes, no centrioles
Single axon arising from axon hillock ( trigger zone )
Axoplasm and axolemme
What is axonal transport
Many proteins made in soma, must be transported to axon and axon terminal
First anterograde ( express train) : axon up to 400 mm/day for organelles, enzymes, vesicles and small molecules Soma for recycled materials and pathogens ( herpes)
Slow transport ( local train) Moves cytoskeletal protein and new axoplasm at 10mm/day during repair in damage axon
Fundamentals types of neurons
Sensory: receptors detect change in environment/body
Info transmitted into brain or spinal cord
Interneurons( association neurons)
Between sensory and motor pathways in cns
90% are interneurons
Process and retrieve information
Motor efferent neuron : send signal out of muscle and gland cells,
Organs carry out responses called effectors
What is the myelin sheath ?
Insulating layer around nerve fiber
Formed from wrapping of plasmas membrane 20% proteins 80% lipid ( looks white)
In pns 100’s of layers wrap axon , outter most coil is Schwann cells
In cns : no neurilemma or endometrium
Gaps between myelin segments - nodes of ranvier
Speed of nerve impulses
Speed depends on diameter fiber and presence of myelin
Small Unmyelinated for - 0.5-2.0 m/sec
Small myelinated - 3-15.0 m/sec
Large myelinated- up to 120 m/sec
Functions of nerve impulses
Slow signals -supply the stomach and dilate pupil
Fast signals - supply skeletal muscles and transport sensory signals for vision and balance
Synapses between 2 neurons
First : released neurotransmitters onto 2nd neuron that responds to cl -( presynaptic)
2nd:synapses maybe be axodentric, axosomatic or axocixonic ( postsynaptic)
800 on spinal motor neuron
100,000 on neuron In cerebellum
Resting membrane potentials
Potential difference across the membrane if resting cell
Approximately -70 mv
Cytoplasmic side negatively charged relative to outside
Generated by
Difference in ionic make up of ICF and ECF
Depolarization vs hyperpolarization
Membrane potential move towards omv, inside becomes more positive ( less neg)
Membrane potential increases inside becoming more negative
Excitability postsynaptic potentials
Local depolarization of postsynaptic membrane, brings neuron closer to ap
threshold neurotransmitter binding open chemically gated ions , allowing stimultaneous passage of na+ and cl -
Inhibitory postsynaptic potentials
Local hyper polarization drives neuron away from ap threshold binding open k+ and cl-
Summation vs no summation
Excitability and excitatory and inhibitory synapses added together
No summation : 2 stimili separated in time cause Epsps that do not add together
Temporal summation vs spatial
Excitatory stimuli close in tune cause epsps that add together
2 simultaneous stimuli at different location cause rose thst add together spatial summation of epsp and iPsp
Change can cancel each other out
3 kinds of synaptic transmission
Excitability cholinergic
Inhibitory gaba ergic
Excitatory adrenergic
Synapses delay .5 m/sec
Excitatory cholinergic
Nerve signal opens voltage gated calcium channel
Trigger release of ach which cross synapse
Ach receptors trigger open na channel producing local potential
When recahsea threshold ( -55 nvm) triggers Ap
Inhibitory gaba
Nerve signal triggers release of gaba ( y aminobutyric acid which cross synapses
Gaba receptors triggers open of cl channel producing hyper polarization
Postsynaptic is less likely to reach threshold
Excitatory adrenergic snypanse
Neurotransmitter in norepinephrine ( n e)
Acts through second messenger system ( amp)
Receptor in intergral membrane proteins
Amp multiple effects
Synthesis of new enzymes
Activating enzymes
Opening I gland gated or produce a postsynaptic potential
Excitatory adrenergic
Cessation r modification of the signals
Mechanism to turn off stimulation
Synaptic knobs reabsorbs amino acids and monomers by eadocytes and break them down
Neural integration
The more synapses, the greater it’s information processing capability
Cell in cerebral cortex
Cerebral cortex estimate to contain 100 trillion synapses
Chemical synapses are decision making components of nervous system
Ability to process store and recall info
-base on types of postsynaptic potentials produce by neurotransmitters
Neural coding qualitative vs quantitative
Qualitative - salty/sweet depends on which neurons tried
Quantitative - strong stimuli excite different neurons ( different threshold)
Strong stimuli cause faster rate
Cns judges stimulus strength from firing frequent sensory neurons
Neuron circuiate vs converging
Diverging circuit - 1 cell synapses on another that each synapses on another ( ex motor unit )
Input from many fibers on one neuron ( respiratory center , balance )
Memory and synaptic plasticity
Memoirs not stored in individual cell
Physical basis of memory is a pathways of cell
- memory trace or engram
New synapses or exsisting synapses has been modified to make transmission easier
