Nervous System

jellyfish hydras, and sea anemone have what type of nervous system

a nerve net

structure of a nerve net nervous system

spread out but in contact with one another

what type of nervous system do planarians have

a ladder like nervous system

do ladder like nervous systems have cephalization

yes

what is cephalization in planarians

a concentration of ganglia and sensory receptors in head

annelids, arthropods, and mollusks are considered complex animals and have what type of nervous system

true nervous systems

human nervous system is made up of what two parts

the CNS and PNS

what is the central nervous system made up of

brain and spinal cord

what is the peripheral nervous system made up of

the somatic and autonomic nervous systems

the PNS is everything but

the brain and spinal cord

where does the cns lie in the body

the midline of the body

peripheral nervous system contains ___ nerves and ____ nerves

cranial and spinal

where do cranial nerves connect

the brain

where do spinal nerves connect

the spinal cord

pns gathers info from

sensors

pns conducts decisions to

effectors

nervou system functions

receive sensory input, performing integration, generating motor output

what are the two main types of nervous tissue

neurons and glial cells

__ of a neuron contains the nucleus

cell body

__ of a neuron receive signals from sensory receptors (other neurons)

dendrites

__ of neuron conducts nerve impulse

axon

axon is covered by __

myelin sheath

any long axon is also called a __

nerve fiber

true of false: neurons do not also contain organelles common to many other cells such as mitochondria and a nucleus

false, neurons do contain mitochondria and a nucleus

true or false: along with the common organelles like nuclei and mitochondria neurons also have more specialized structures

true, neurons contain more specialized structures like dendrites and axons

what do sensory neurons do

accept impulses from sensory receptors and transmit them to the CNS

what do motor neurons do

accept nerve impulses from the CNS and transmit them to muscles or glands

what do interneurons do

convey nerve impulses between various parts of the CNS

neurons have diversity in ___ and ___

size and shape

true of false cells structure and function are linked

true

role of glial cells

support, protect and nourish neruons

glial cell to neuron ratio in the brain

10 to 1

most brain tumors are caused by mutations in ___

glial cells

glial cells in the CNS include

oligodendrocytes, astrocytes, ependymal cells, microglia

function of oligodendrocytes

form myelin sheath around axons

function of astrocytes

provide nutrients and structural support

function of ependymal cells

produce cerebrospinal fluid that cushions neurons

function of microglia

scavenge pathogens and dead cells

glial cells in the PNS include

Schwann cells and satellite cells

function of Schwann cells

form the myelin sheath

function of satellite cells

provide nutrients and structural support to neurons

signals are possible because each neuron has a charged ____

cellular membrane

what does having a charged cellular membrane mean

there is a voltage difference between the inside and outside of the membrame

the charge of the cellular membrane can change in response to

neurotransmitter molecules released from other neurons and environmental stimuli

sodium potassium pump: animals cells use ATP to pump ___ out of the cells and ___ into the cells against their concentration gradients

NA+ out, K+ in

the concentration of __is higher inside the cell- meaning must use energy to pump it into the cell

K+

the concentration of NA + is higher outside the cell meaning must use __ to pump NA+ out of the cell

energy

the sodium potassium pump moves 3 positively charged ions out of the cell and only 2 positively charged ions into the cell this leads to there being a net ___ charge outside the cell

positive

the membrane potential is used to do ___ for the cell

work

membrane potential=

difference in electrical charge (voltage) across a cell membrane due to the differential distribution of ions

resting membrane potential of a neuron

about -70 mV

how is resting membrane potential created and maintained

by increasing the concentration of cations outside the cell (in the extracellular fluid) relative to inside the cell (in the cytoplasm).

__-gated ion channels regulate the relative concentration of diff ions inside and outside the cell

voltage

action potential: the stimulus causes what specific ion channel to open

NA+

action potential: what happens when the NA+ channels open

NA+ outside of the cell diffuse into the cell not only down its concentration gradient but also because it’s attracted to the negative charge on the inside of the cell (electro chemical gradient)

action potential: what happens when K+ specific channels open

K+ diffuses down its gradient (out)

after the action potential the sodium potassium pump does what

re-polarizes the membrane in anticipation of another stimulus

step one of action potential:

a stimulus from a sensory cell or another neuron depolarizes the target neuron to its threshold potential

step two of an action potential

NA+ channels in the axon hillock open, allowing positive ions to enter the cell

during an action potential, once the sodium channels open the neuron completely

depolarizes to a membrane potential of about 40mV

action potentials are considered a __ event

all or nothing

once the threshold potential is reached the neuron always completely __

depolarizes

once depolarization is complete the cell must now “reset“ its membrane voltage back to its

resting potential

an action potential moves like a ___ down a___

wave down an axon

what are nodes of ranvier

gaps in myelin coverage along axons

action potentials travel down axon by jumping from one ___ to the next

node

nodes of ranvier contain voltage gated ___ and ___ channels

K+ and Na+

chemical synapse: depolarization along axon causes voltage gated _ channels to open

Ca2+

at the synapse, calcium ions initiate a signaling cascade that causes ___

synaptic vesicles containing neurotransmitter molecules, to fuse with the presynaptic membrane

fusion of a vesicle containing neurotransmitter with the presynaptic membrane causes what

neurotransmitter to be released into the synaptic cleft

once neurotransmission has occurred, the neurotransmitter must be _____

removed from the synaptic cleft so the postsynaptic membrane can “reset“ and be ready to receive another signal

spinal cord and brain are wrapped in three protective layers called what

meninges

brain is covered by three layers of meninges:

the dura, arachnoid, and pia mater

spaces between meninges are filled with __

cerebrospinal fluid

cerebrospinal fluid found between meninges is __

continuous with that of central canal of spinal cord and the brain

spinal cord is the center for many __ actions

reflex

what is the means of communication between the brain and spinal nerves

the spinal cord

what is the spinal cord composed of

grey matter and white matter

what give grey matter its color

cell bodies and unmyelinated fibers

what gives white matter its color

myelinated long fibers of interneurons running in tracts

somatic nervous system functions

transmits sensory and motor signal to an from the central nervous system, controls skeletal muscles

is somatic nervous system for actions we are conscious of or not conscious of

conscious of

autonomic nervous system functions

controls smooth muscle, cardiac muscle, organs, and glands

divisions of the autonomic nervous system

sympathetic and parasympathetic

is autonomic nervous system for actions we are conscious of or not conscious of

not conscious of

sympathetic activation-

prepares us for fight or flight

parasympathetic activation-

associated with normal conditions under relaxed conditions (rest and digest)

what are neurodegenerative disorders

illness characterized by a loss of nervous system functioning

what are neurodegenerative disorders caused by

neuronal death