The nervous system and endocrine system work together how?
The nervous system is made up of what
The nervous system is organized to detect what
(Stimuli) in the internal and external environment, evaluate that information and respond by initiating changes in muscles or glands
Central nervous system
Brain
Spinal cord
Peripheral nervous system
Cranial nerves
Spinal nerves
Afferent and efferent division
Peripheral nervous system
Autonomic nervous system
The two main types of cells that compose the nervous system
Neurons: excitable cells that conduct the impulses that make possible all nervous system
- “wiring of the nervous system”
Glia: do not usually conduct information but support the function of neurons
- supporting cells
Types of neuroglia
Astrocytes: provide metabolic (feeding) and structural (BBB) to neurons
Microglia: phagocytic cells that help remove bacteria and debris
Ependymal cells: form thin sheets that line fluid-filled cavities in the brain and spinal cord
Oligodendrocytes: produce the fatty myelin sheath around nerve fibers in the CNS
Schwann cells: produce myelin sheath around nerve fibers in the PNS
The three parts of a neuron
Cell body (soma): main part of the cell, has the nucleus and most of the cytoplasm and organelles
Dendrites: small, slender extensions of the cell body, which receive incoming information
Axon: long, slender extension, specialized to conduct electrical impulses away from the cell body
Physiology of a neuron
Membrane potential - all living cells, maintain a a difference in the concentration of ions across their membranes
Functions of Na+/K+ pump
Resting potential
Resting potential: measurable difference in voltage across the cell membrane in a resting cell
-> -70 mV
-> interior of cell is negative relative to the exterior
Graded potential
Summation
An action potential is a sudden reversal of membrane voltage
Depolarization
Repolarization
Reestablishment of the resting potential
Steps of the mechanism of action potential
1) when adequate stimulus is applied to the neuron, stimulus - gates Na+ channels open
- causing rapid Na+ diffuse into the cell
2) Threshold potential: the minimum magnitude a voltage fluctuation in the condition zone must have to trigger the opening of a voltage-gated ions channels
- -55mV = threshold
- More, rapid Na+ diffuse into the cell
3) as more Na+ rushes into the cell, the membrane moves rapidly toward 0mV
- continuing, is a positive directly until it reaches + 30mV
4) Na+ gates close automatically (Na+ channels open for the same amount of time and magnitude each action potential
- All-or-none response
5) K+ voltage gated ions channels open (these gates are stimulate at the same time as the Na+ but are slow
- K+ rapidly diffuses out of the cell, returning the cell to RMP
6) Hyperpolarization occurs while the K+ gates close
- at which point the sodium-potassium pump returns the cell to its RMP
All-or-none action potential
Self-propagating
The number of action potential/unit time encodes the strength of the stimulus
Saltitory glands
Synapse