Neurons and Neuronal Intergration

Physiology exam 2

describe the three main parts of the neurons

1. the cell body - has the nucleus and the organelles

2. dendrites - projections of the cell body that receive the incoming signals

3. the axon - tubular structure that conducts the action potential away from the cell body and to other cells

describe the events of propagation of an action potential down the axon

describe the neuronal conduction and synapses

explain EPSP and IPSP, neuronal summation

the input zone

the dendrites, receives incoming signals from other neurons

the trigger zone

initiates action potentials at the axon hillock

the conducting zone

conducts the action potentials in undiminishing fashion, over long distances by the axon

the output zone

releases neurotransmitters that influence other cells at the axon terminals

Three main function regions of the neuron:

the receptive region

the dendrites and cell body

Three main function regions of the neuron:

the conducting region

the axon

Three main function regions of the neuron:

the secretory region

axon terminal

the all or nothing principle

AP happen in an all or nothing depending on the strength local potential of the stimulus, once an AP is stimulated it does not need another stimulus

absolute refractory period

the “hump” of the action potential where

1. Na channels are activated and K channels are activating slowly

then

2. Na channels are inactivated and K channels are activated

relative refractory period

the “dip” in the action potential 

Na channels are in a resting state and K channels remain activated

AP velocity depends on

1. myelination of the fiber

2. fiber diameter

contiguous conduction

AP triggers a depolarization in a nearby membrane, then that one does it to another 

domino affect

saltatory conduction

“skipping” the impulse along the nerve (on the myelinated sheaths)

50x faster than unmyelinated

AP does not have to be regenerated at myelinated section

myelin in the myelinated fibers are made by

schwann cells (PNS) and Oligodendrocytes (CNS)

Nodes of ranvier

voltage-gates Na channels concentrated between myelin sheaths 

fiber diameter

influences the velocity of action potential propagation

increased diameter means there is less resistance, which increases the velocity

Synapses

the connection between two neurons (presynaptic, post synaptic, and extracellular space)

where do neurons terminate

either at the 

1. muscle

2. gland

3. neuron

innervate

when a neuron terminates on another tissue

two types of synaptic connection

1. electrical (gap junctions)

2. chemical (neurotransmitters)

chemical synapses

chemical neurotransmitter is released from the presynaptic neuron and acts on the cell body or the dendrites of post synaptic neuron

synaptic knob

bulbous end of a neuron's axon that transmits signals to another cell

the synaptic vesicles

contain the neurotransmitters

the presynaptic neuron conducts the AP towards

the synaptic knob

the synaptic cleft

the space between the synaptic knob and the synaptic vesicles

release of the neurotransmitter from the presynaptic neuron effects

the AP firing of the post synaptic neuron

the neurotransmitters on the postsynaptic terminal

can be EITHER inhibitory or excitatory

Excitatory postsynaptic potential

EPSP

closer to threshold

inhibitory postsynaptic potential

IPSP

further away from threshold

EPSP and IPSP are both what kind of responses

graded responses

neural integration

postsynaptic neuron integrates all incoming information into single effect

can graded potentials summate?

yes

what does summate mean

to add together, unite, or summarize

grades potentials can summate to reach 

threshold, and cause an action potential 

temporal summation

The action of one EPSP makes the next EPSP more likely to elicit an AP

how can a second EPSP push the cell the threshold?

the membrane potential is still elevated from the first EPSP, so a second EPSP can push it from the elevated point

Spatial Summation

the actions of an EPSP or IPSP summating over a space or distance 

the EPSP or IPSP can happen at the exact same time, but if they are not physically close enough together there will be no summation

synaptic cleft

space between the presynaptic neuron and the postsynaptic neuron