final

neurons

Cells that are responsible for the working of the brain and the rest of the nervous system

electrical signals

Neurons conduct information in the form of __?_ __?_ from point to point

sponges

what is the only animal without neurons + muscle cells

nerve net, central nervous system (CNS)

what are the 2 basic types of nervous systems?

nerve net

type of nervous system: Found in cnidarians (jellyfishes, hydra, and anemones) and ctenophores (comb jellies)

ganglia

central nervous system (CNS) includes large numbers of neurons aggregated into clusters called __?_

sensory cells

–Respond to light, sound, touch, or other stimuli

–In the skin, eyes, ears, and nose, transmit streams of data about the environment

\-Inside the body, monitor conditions that are important in homeostasis, such as blood pH and oxygen levels

sensory neurons

sensory cells that carry information to the central nervous system (CNS)

interneurons

__?_ pass signals from one neuron to another

motor neurons

Nerve cells that send signals to effector cells in glands or muscles

nerves

Motor neurons and sensory neurons are bundled together into long strands called **__?_**

peripheral nervous system (PNS)

All neurons and other components of nervous system outside the CNS are part of the __?_

reflex

An involuntary response to an environmental stimulus

sensory neurons, interneurons, motor neurons

pricking finger example motor neuron pathway in order (explain in head)

cell body/soma

part of neuron that includes the nucleus

dendrites

part of neuron that is a highly branched group of relatively short projections

axons

part of neuron that is one or more relatively long projections

dendrites, axon, axon, dendrites

__?_ receive signals from the __?_ of other neurons, and a neuron’s __?_ sends signals to the __?_ and cell bodies of other neurons

ions

__?_ carry an electrical charge

electrical potential, membrane potential

–Cytoplasm and extracellular fluids adjacent to the plasma membrane of cells contain electrically unequal distributions of ions

•This difference in charge creates an __?_ __?_ across the plasma membrane, known as a **__?_** **__?_**

membrane potential

a separation of charge immediately adjacent to the plasma membrane

millivolts

Membrane potentials measured in units called __?_ (**1/1000 of a volt)**

inside, outside

By convention, membrane potentials are expressed in terms of __?_ relative to __?_

inside, outside, negative

Generally, more negative ions are on the __?_ surface of the plasma membrane than the __?_. Thus, membrane potentials are usually __?_

potential energy

Membrane potential are a form of __?_ __?_

electric current

a flow of electric charge

electrochemical gradient

The combination of an electric gradient and a concentration gradient is an __?_ __?_

resting potential

The difference in charge across membrane when neuron is not communicating with other cells

Na+, Cl-, K+, anions

the interior side of a cell membrane has low concentrations of __?_ and __?_ ions. it has high concentrations of __?_ and __?_

Na+, Cl-

in the extracellular fluid outside of the cell membrane __?_ and __?_ are predominant

primary active transport (against gradient), secondary active transport (against gradient), diffusion (along gradient)

what are the 3 ways the ions on either side of the plasma membrane can cross it?

ion channel

a protein that forms a pore in the membrane through which specific ions can diffuse

Na+, K+

**N a+/K+ -ATPase** pump actively pumps __?_ out of cell and __?_ into cell

K+, Na+

Active transport via **N a+/K+ -ATPase** pump ensures the Concentration gradient of __?_ is higher on inside of plasma membrane while concentration of __?_ is lower on the inside

cations

At rest, plasma membrane of a neuron is relatively impermeable to most __?_

leak channels

K+ channels

concentration, electrical

equilibrium exists between the __?_ gradient that favors movement of K+ out of cell, and the __?_ gradient that favors movement of K+ into cell

equilibrium potential

the membrane potential at which there is no net movement of a particular ion into or out of a cell (K+ example)

negative

Neuron has a __?_ resting membrane potential

action potential

rapid, temporary change in a membrane potential

depolarization, repolarization, hyperpolarization

what are the 3 phases of action potential (in order)

depolarization

phase of action potential in which the membrane becomes less negative and moves toward a positive charge

repolarization

phase of action potential that changes membrane back to a negative charge

hyperpolarization

phase of action potential in which the membrane becomes more negative than it was during the resting potential

threshold potential

the membrane potential that will trigger an action potential

axon, into, negative, positive

if threshold potential is reached certain channels in the __?_ membrane open, allowing ions to rush __?_ the axon

–Causing the inside of the membrane to become less __?_  and then __?_ with respect to the outside of the neuron

repolarization

When the membrane potential reaches about +40 milliVolts, the __?_ phase begins

excitable membranes

neurons have __?_, plasma membranes that are capable of generating an action potential

actions potentials

In nervous system, information is coded in the form of __?_ __?_ that travel along axons

Na+

action potential begins when __?_ flows into the neuron

K+

there is a strong flow of __?_ out of the cell during repolarization

Na+, K+

The action potential consists of a strong inward flow of __?_ ions followed by a strong outward flow of __?_ ions

voltage gated channels

Membrane proteins that open and close in response to changes in membrane voltage

closed, open

at resting potential the voltage gated Na+ channels are __?_. When the membrane is depolarized the voltage gated Na+ channels are __?_

voltage clamping

Hodgkin and Huxley confirmed that voltage-gated channels exist using a technique called **__?_ __?_**

patch clamping

•Erwin Neher and Bert Sakmann perfected a technique known as __?_ __?_:

–Allows the isolation of a single channel using a microelectrode to suction a single ion channel

positive

what type of feedback loop?:

* initial depolarization leads to the opening of more N a+ channels, which depolarizes the membrane further, which leads to the opening of more N a+ channels, etc.

neurotoxins

poisons that affect nerve function

depolarize

As cations are pushed farther from the initial sodium channels, they __?_ adjacent “downstream” portions of the membrane

refractory

•Once Na+ channels have opened and closed, they are less likely to open again for a short period of time:

–Known as the __?_ state

large, small

__?_ -diameter axons transmit action potentials much more quickly than __?_ axons

oligodendrocytes

membranes of specialized accessory cells that wrap around axons of vertebrate neurons in the central nervous system (CNS)

schwann cells

membranes of specialized accessory cells that wrap around axons of vertebrate neurons in the peripheral nervous system (PNS)

myelin sheath

When oligodendrocytes or Schwann cells wrap around an axon, they form a __?_ __?_

myelin sheath

Acts as electrical insulation, preventing ions from leaking out across the plasma membrane during the propagation of an action potential

node of ranvier

gap in myelin sheath

Na+, K+, action potentials

node of ranvier has dense concentration of voltage gated __?_ and __?_ channels, so new __?_ __?_ can be generated

unmyelinated

In an **__?_ axon**, voltage-gated Na+ and K+ channels are found along its entire length, and action potentials propagate continuously down the axon

multiple sclerosis

autoimmune disease that develops when the immune system targets oligodendrocytes, destroying myelin in the CNS

synapse/ synaptic cleft

most neurons are separated from one another by tiny spaced called __?_

neurotransmitters

Chemical messengers that transmit information from one neuron to another neuron, muscle, or gland

synaptic vesicles

store neurotransmitters at the end of the axon

presynaptic neuron, postsynaptic cell

at synapse, the neuron that transmits the signal is the __?_ __?_ and the cell that receives the signal is the __?_ __?_

Ca2+

when action potential arrives at the end of the axon it causes __?_ channels to open near the synapse of the presynaptic neuron

synaptic vesicles

as Ca2+ enters the presynaptic neuron it causes __?_ __?_ to fuse with the axon membrane

neurotransmitters

ion channels in postsynaptic membrane open when __?_ bind to receptors

ligand

Molecules that bind to a specific site on a receptor molecule

membrane potential

Neurotransmitter-receptor binding causes ion channels in the postsynaptic membrane to open, leading to a change in the __?_ __?_ of the cell

action potential

The combined effect on membrane potential of many neurotransmitters binding may trigger an __?_ ___?_ in the postsynaptic cell

ligand-gated ion channels

Many neurotransmitters bind to receptors called __?_

enzymes, second messenger

Some neurotransmitters bind to receptors that activate __?_ 

–Action leads to production of **__?_ __?_** in postsynaptic cell

synapse

Ligand-gated sodium channels on membranes of dendrites are particularly high in concentration near __?_

Na+, depolarization

when neurotransmitters bind to ligand-gated sodium channels, these channels open and allow __?_ to enter the cell, causing __?_

excitatory postsynaptic potentials (EPSPs)

Changes in the membrane potential of a postsynaptic cell that make the cell more likely to produce an action potential (exp: Na+ entering cell)

inhibitory postsynaptic potentials (IPSPs)

If neurotransmitter-receptor binding leads to an outflow of potassium ions or an inflow of chloride ions or other anions in the postsynaptic cell, the postsynaptic membrane hyperpolarizes—making action potentials less likely to occur in the postsynaptic cell

neurotransmitter

The magnitude of an EPSP or IPSP depends on the amount of __?_ that is released at the synapse at a given time

EPSPs, summation

If several __?_ occur close together, they sum and make the neuron likely to fire an action potential

–The additive nature of postsynaptic potentials is called  __?_

axon hillock

The sodium channels that trigger action potentials in the postsynaptic cell are located at the **__?_ __?_**

axon hillock

place where the axon emerges from the cell body

central nervous system (CNS)

made up of brain and spinal cord

afferent division, efferent division

what are the 2 division of the peripheral nervous system (PNS)

afferent division

which division of PNS? transmits sensory information to the CNS. the neurons monitor conditions inside and outside the body

efferent division

which division of PNS? carries signals that allow the body to respond to the changed conditions in an appropriate way

somatic nervous system, autonomic nervous system

what are 2 systems of the efferent division of the PNS?

somatic nervous system

which system of efferent division of PNS? carries out voluntary responses, which are under conscious control (skeletal muscle serves as the effectors)

autonomic nervous system

which system of efferent division of PNS? carries out involuntary responses, which are not under conscious control (smooth muscle, cardiac muscle, and several glands serve as the effectors)

sympathetic nervous system, parasympathetic nervous system

2 types of autonomic nervous system?

parasympathetic nervous system

type of autonomic nervous system? promotes “rest and digest” functions that conserve or restore energy

sympathetic nervous system

type of autonomic nervous system? prepares organs for stressful situations—“fight or flight”

sympathetic, parasympathetic

During exercise, **__?_ neurons** are activated while **__?_ neurons** are inhibited