A+P: neuro study guide

how does Acetylcholinesterase works at the synaptic cleft?

breaks down acetylcholine into choline and acetate

what occurs when the voltage-gated K channels open on the conductive segment of a neuron?

K+ exits cell, causing negative membrane potential

what is the order of refractory periods?

absolute then refractory

what happens when a nerve impulse reaches the transmissive segment of a neuron?

-arrival of action potential opens voltage-gated Ca2+ channels

-Ca2+ diffuses into knob

-Ca2+ binds to proteins associated with synaptic vesicles and triggers exocytosis

-vesicles fuse with membrane, neurotransmitter release

-neurotransmitter binds to ligand receptors

What allows for the fastest nerve impulse to occur?

thick and myelinated

How is acetylcholine cleared from a synapse?

acetylcholinesterase

chronological order of the events involved in synaptic transmission

-neurotransmitter molecules released from vesicles of synaptic knob into cleft

-neurotransmitter diffuses across cleft and binds to postsynaptic receptors

-binding of neurotransmitter to receptor initiates post synaptic potential

-synaptic delay

converging circuit

input converges at a single postsynaptic neuron

ex: salivation, sights, sounds

diverging circuit

spreads information from one presynaptic neuron to several postsynaptic neurons

ex: walking

reverberating circuit

-use feedback to produce repeated, cyclical activity-once started, it stays active until there is an inhibitory stimulus or synaptic fatigue

ex: breathing

parallel after discharge circuit

-input transmitted simultaneously along several paths to a postsynaptic cell-since paths vary in number of synapses, signal arrives at postsynaptic cell at various times-believed to be involved in higher-order thinking

what is a graded potential?

small, short-lived changes in the RMP

What happens when depolarization occurs and how does it differ from the resting membrane potential?

Na+ enters the cell, becomes more positive

What would happen to the resting membrane potential if there were no Na leak channels?

if K+ were the only ion that leaked, RMP would be where the K+ concentration and electrical gradients are at equilibrium

Ohm's law

I= V/R

Where does potassium have the greatest concentration?

cytosol

which division of the nervous system has the potential for regeneration?

PNS

what conditions are necessary for regeneration to occur?

-neuron cell body is intact

-enough neurilemma remains

function of myelin

insulates

function of oligodendrocytes

-large cells with slender extensions

-extensions wrap around axons of neurons forming myelin sheath

astrocytes

Have processes that end in perivascular feet

- Most abundant glial cell in CNS

- Help form blood-brain barrier by wrapping feet around brain capillaries

- Controls which substances have access to brain

- Regulate tissue fluid composition (chemical environment around

neurons)

ependymal cells

-Line cavities in brain and spinal cord

- Part of choroid plexus, which produces cerebrospinal fluid

microglia

- Small cells that wander CNS and replicate in infection

- Phagocytic cells of immune system

- Engulf infectious agents and remove debris

oligodendrocytes

- Large cells with slender extensions

- Extensions wrap around axons of neurons forming myelin sheath PNS Glial Cells:

satellite cells

- Arranged around neuronal cell bodies in a ganglion

- Electrically insulate and regulate the exchange of nutrients and wastes

neurolemmocytes

- Elongated, flat cells that ensheath PNS axons with myelin

- Allows for faster action potential propagation

what is a mixed nerve?

contain both sensory and motor neurons

multipolar neuron

many dendrites, one axon

bipolar neurons

one dendrite and one axon

unipolar neurons

one process extends from cell body

structure of neuron

cell body (soma), dendrites, axon

what is located in cell body?

- Plasma membrane encloses cytoplasm (perikaryon)

- Contains nucleus

- Initiates some graded potentials, receives others from dendrites;

conducts these potentials to axon

- Contains chromatophilic substance (Nissl bodies) made of

ribosomes (free and bound)\

what does axon contain?

- Attaches to cell body at axon hillock (triangular region of soma)

- Cytoplasm called axoplasm; membrane called axolemma

- Splits into branches called axon collaterals

- Ends in several telodendria (axon terminals)

- Tips of telodendria are synaptic knobs (terminal boutons)

- Synaptic knobs house synaptic vesicles containing

neurotransmitter

- Axons function to conduct action potentials and then release

neurotransmitter at synaptic knobs

what does cytoskeleton contain?

- Composed of microfilaments, intermediate filaments, microtubules

- Intermediate filaments, termed neurofilaments

characteristics of neuron

-structural unit of nervous system

-excitability

-conductivity

-secretion

-extreme longevity

-amitotic

excitability

-responsiveness to a stimulus

- Stimulus causes change in cell's membrane potential

conductivity

-ability to propagate electrical signal

- Voltage-gated channels along membrane open sequentially

secretion

-release of neurotransmitter in response to conductive activity

- Messenger is released from vesicle to influence target cell

extreme longevity

cell can live throughout person's lifetime

amitotic

After fetal development, mitotic activity is lost in most neurons

autonomic motor neuron

(visceral motor) sends involuntary commands to heart, smooth muscle, and glands

somatic motor neuron

sends voluntary signals to skeletal muscles

somatic sensory

-detects stimuli we consciously perceive

- tactile receptors of skin and mucous membranes; proprioceptors of joints, muscles, and tendons

visceral sensory

-detects stimuli we do not perceive

- for example: signals from heart or kidneys

- found in walls of internal organs, monitor stretch, chemical

environment, temperature, pain

somatic motor system function

sends voluntary signals to skeletal muscles

autonomic motor system

-(visceral motor) sends involuntary commands to heart, smooth muscle, and glands

- has sympathetic and parasympathetic divisions

sensory nervous system=

afferent nervous system

motor nervous system=

efferent nervous system (e for exit)

what is the name of the tissue that wraps the entire nerve?

epineurium

motor nerve

contain motor neurons sending signals from CNS

sensory nerve

contain sensory neurons sending signals to CNS

mixed nerves

contain both sensory and motor neurons

which neurons are "association" neurons in the CNS?

interneurons

what is the term for the cytoplasm within the cell body of a neuron?

perikaryon

what is the term for the plasma membrane of an axon?

axolemma

what occurs after action potentials arrive at the presynaptic terminal (aka synaptic knob) and cause the voltage-gated calcium channels to open?

Ca+ binds to proteins associated with synaptic vesicles and triggers exocytosis!!!! (KNOW)

- vesicles fuse with membrane, neurotransmitter release

- neurotransmitter binds to ligand receptors

What kind of neuron can only produce local potentials?

A neuron that has graded potentials

repolarization

-the return to negative potential as K+ exits through

voltage-gated K+ channels.

- occurs when threshold is +30mV, during absolute refractory period

depolarization

-the gain of positive charge as Na+ enters through voltage-gated Na+ channels.

- occurs when threshold -55mV is reached, during absolute refractory period

value of the typical resting membrane potential

-70 mV