nervous system

neurons

nerve cells

soma

cell body of neurons

dendrites and axons

processes extending from the soma of neurons

how many dendrites and axons are in a neuron?

one axon only but several dendrites

what do neurons do?

It receives impulses at its dendrites and transmits the impulse through the cell body and down the axon

When a neuron is polarized, it is_________

resting. The inside is negatively charged compared to the outside of the neuron

the resting membrane potential is ____mV and its definition is__________

-70mV
it is the difference in charge between the outside and the inside of the neuron

what are the 2 membrane proteins?

sodium-potassium pump and the leak channels

What does the sodium-potassium pump do?

It uses one molecule of ATP to move 3 sodium ions out of the cell while simultaneously moving 2 potassium ions into the cell

Are the sodium and potassium ions negative or positive?

positive

What do the leak channels do?

They let potassium ions leak out from the inside of the cell according to its gradient

Why does a neuron have a resting membrane potential of -70mV?

because the sodium-potassium pump and the leak channels let a lot of positive ions leave and cell and so a lot of negative stuff (DNA, RNA and proteins) are left behind.

What are voltage gated channels?

channels that open when the cell membrane reaches a particular voltage

The potential at which the voltage-gated channels open is ________

threshold potential

2 types of voltage-gated channels are:

sodium and potassium voltage-gated channels

The membrane potential moves in the postive direction

depolarization

The membrane potential returns to its negative value

repolarization

What is an impulse?

a traveling action potential

action potential travels in what direction?

down the axon

What are the steps in an action potential?

1) A neuron is polarized (-70mV) and depolarizes slightly to -50mV. The sodium and potassium voltage-gated channels then opens.

2) sodium v-g channel opens first and sodium ions enter according to its concentration gradient previously established by the Na+K+ ATPase pump

3) The sodium ions depolarizes the cell until it reaches the maxium of +35mV. The Na+ v-g channel then closes

4) the K+ v-g channel opens and K+ exits the cell according to its concentration gradient

5) The cell is repolarized to -90mV before the K+ channels close

6) the Na+ K+ ATPase and leak channels return the cell to its resting polarized state.

sometimes the axon is wrapped with special cells called ________. This entire wrapping is a _____________

schwann cells

myelin sheath

Node of Ranvier

spaces between the Schwann cells

What is saltatory conduction?

a jumping type of conduction where the impulse jumps from nodes to nodes. This increases the speed in which the impulse can travel down the axon

What is a refractory period?

the period after firing an action potential where the portion of the membrane is unable to fire another action potential. This ensures that the action potential will only travel in one direction

What is a synapse?

an neuron to neuron junction or a neuron to organ junction

What is a neurotransmitter?

a chemical that passes an impulse from one neuro to the next

The gap between the axon and the dendrite of another neuron

synaptic cleft

The neurotransmitter is in vesicles and it is released into hte synaptic cleft by _______

exocytosis

When a cell is ________it depolarizes toward the threshold

stimulated

When a cell is _________it moves away from the threshold

inhibited

What is summation?

A neuron taking all of the stimulatory input and inhibitory input and adding them up to determine if it will fire an action potential

The most common neurotransmitter in the body

acetylcholine

The brain and the spinal chord are part of the _____________ system

central nervous

neurons completey within the brain and the spinal chord and connect sensory and motor neurons

interneurons

neurons that send info to the CNS from the sensory organs

sensory neurons

neurons that send info from the CNS to muscles and glands

motor neurons

motor and sensory neurons are part of the

peripheral nervous system

interneurons are part of the

CNS

the 2 divisions of the PNS are:

the somatic nervous system and the autonomic nervous syste

The skeletal muscles are controlled by the _______ nervous system

somatic

acetylcholine is used by the ________ system and the ______ division as a neurotransmitter

somatic nervous, parasympathetic

the autonomic nervous system is divided into:

sympathetic division and parasympthatic division

What is the fight or flight system?

sympathetic division

What is the resting and digesting system?

parasympathetic division

This is where voluntary actions such as movement, speech etc. occur

cerebrum

this part of the brain coordinates balance and muscle movement

cerebellum

this primitive part of the brain regulates breathing and blood pressure

medulla

this part of the brain monitors hormone levels, temperature and electrolyte balance

hypothalamus