nervous system organization-lecture 19

cell body

holds nucleus and most organelles

dendrites

numerous, highly branched, and recieves/transmits signals to cell body

axon

transmits signals to other neurons or effector cells and unbranched besides at ends

somatosensory axis 

sensory afferent information is obtained from sensory receptors

peripheral nerves carry info to cns spinal cord —> then up systems (medulla, pons, midbrain, etc)

integrative function of nervous system

processes info—>excites the mind —→channeled into proper integrative and motor regions of brain—→desired response

spinal cord level

walking movements, withdraws from painful objects, stiffen legs, etc

lower brain level

subconscious activities

arterial blood pressure

controlled by medulla and pons

respiration and equilibrium 

controlled by Cerebellum and medullary reticular nuclei

higher brain level

integrative centers, thought processes, memory, and converts lower brain functions

presynaptic terminals synonyms

terminal knobs, terminal buttons, terminal end-feet, and synaptic knobs

receptor protein functions

binding component (protrudes outward into cleft) and ionophore (post-synaptic to interior of post-synaptic neuron)

cation channel excitatory transmitter

Na decreases & K/Ca increases

anion channel inhibitory channels

Cl decreases

secondary messenger system

1. potassium channel is open for prolonged time 

2. cAMP and cGMP activates highly specifif metabolic machinery in neuron

3. alters long-term excitiabilty

4. intracellualr enzymes are active

5. gene transcription is active and forms new proteins (important in long-term memory processes)

resting membrane potential of neuronal soma

-65 mV 

• the less negative= more excitable 

depolarization

-45 mV and begins action potential sequence

sodium channels

opens and na rishes in down electrical/chemical gradient then closes

repolarization

-k channels open 45-65mv then close

chemical synapse

• releases neurotransmitters into synaptic cleft

• one-way conduction

• ex: acetylcholine, morepinephrine, histamine, GABA, and glutamate

electrical synapse

• has gap junctions 

• free movement of ions

• smooth and cardiac muscle

• transmitted in either direction