Excitable Cells: Nerve and Muscle

Saltatory Conduction in Myelinated Fibers: Impulse seems to_____from node to node.

"jump"

Relaxation (step 16)

-Active transport pumps calcium back into SR where it binds to calsequestrin -ATP is needed for muscle relaxation as well as muscle contraction

What do we mean by "excitable cells"?: The concentration of ____is higher inside the cell and potassium constantly "leaks out" down its concentration gradient. These helps keep the cell ________.

-K+ -electronegative.

What do we mean by "excitable cells"?: The concentration of ___ is higher outside the cell and very little Na+ moves down the concentration gradient into the cell.

-Na+

Cessation & Modification of the Signal:Mechanisms to turn off stimulation-__________degrades ACh in the synaptic cleft.______reabsorbed & recycled

-acetylcholinesterase -choline

Stimulation of Nerves: Neurons are stimulated at ______by a number of types of stimuli such as

-dendrites

Speed of signal transmission along nerve fibers depends on _____ ____ _____& ______ _____ ______

-diameter of fiber -presence of myelin

Characteristics of action potential

-follows an all-or-none law and thus are not graded -are nondecremental (do not get weaker with distance) -are irreversible (once started goes to completion and can not be stopped)

Skeletal Muscle Fibers: _______ for stored energy & ______ binding oxygen

-glycogen -myoglobin

What do we mean by "excitable cells"?: Both _____and ______cells are excitable cells.

-muscle -nerve

Speed of Nerve Signal: Neurons communicate with

-other neurons. -glands. -muscle cells.

Speed of Nerve Signal: The functional area of contact is the _______. The electrical signal cannot cross the synapse and is converted into a chemical signal.

-synapse

Neuromuscular Junctions: Components of synapse

-synaptic knob is swollen end of nerve fiber -motor end plate is region of muscle cell surface

Chemical Synapse Structure: Presynaptic neurons have ______ _______with neurotransmitter and postsynaptic have _______

-synaptic vesicles - receptors

Stimulation of Nerves: Neurons are stimulated at dendrites by a number of types of stimuli such as

-the binding of a ligand (chemical messengers). -mechanical distortion (pressure). light and sound.

Thick Filaments look like

2 entwined golf clubs

Postsynaptic Potentials: _______ & _______ vary depending on cell

ACh & norepinephrine

Neuromuscular Junctions:Components of synapse= motor end plate is region of muscle cell surface and has

ACh receptors which bind ACh released from nerve

-as long as Na+ gates are open -no stimulus will trigger AP

Absolute refractory period

______ is a rest period where a neuron cannot respond to another stimulus no matter how strong the stimulus.

Absolute refractory period

Types of Neurotransmitters: st neurotransmitter

Acetylcholine

Excitation-Contraction Coupling(steps 6&7)

Action potential spreading over sarcolemma reaches T tubules -- voltage-gated channels open in T tubules causing calcium gates to open in SR

Types of Neurotransmitters: 2nd neurotransmitter

Amino acid neurotransmitters

Excitation (steps 3 & 4)

Binding of ACh opens Na+ and K+ channels resulting in an end-plate potential (EPP)

Excitation-Contraction Coupling(steps 8&9)

Calcium release causes binding of myosin to active sites on actin

Postsynaptic Potentials: Inhibitory postsynaptic potentials (IPSP) results from

Cl- flowing into the cell or K+ leaving the cell

Neuromuscular Toxins & Paralysis: Tetanus or lockjaw is spastic paralysis caused by toxin of______ bacteria

Clostridium

Postsynaptic Potentials: a positive voltage change causing postsynaptic cell to be more likely to fire

Excitatory postsynaptic potentials (EPSP)

Neuromuscular Toxins & Paralysis: _____ ______ with limp muscles unable to contract caused by curare that competes with A

Flaccid paralysis

Postsynaptic Potentials:a negative voltage change causing postsynaptic cell to be less likely to fire (hyperpolarize)

Inhibitory postsynaptic potentials (IPSP)

more concentrated inside the cell (ICF)

K+

Relaxation (steps 17 & 18)

Loss of calcium from sarcoplasm results in hiding of active sites and cessation of the production or maintenance of tension

is more concentrated outside of cell (ECF)

Na+

Action Potentials: Voltage-gated Na+ channels open and

Na+ enters for depolarization

Postsynaptic Potentials:Excitatory postsynaptic potentials (EPSP) results from

Na+ flowing into the cell

How skeletal muscle contraction begins: Excitation (steps 1 & 2

Nerve signal stimulates voltage-gated calcium channels that result in exocytosis of synaptic vesicles containing ACh

Modify actions of neurotransmitters

Neuropeptide Classification

Saltatory Conduction in Myelinated Fibers: Voltage-gated Na+ and K+ channels are concentrated at the

Nodes of Ranvier.

Contraction (steps 12 & 13)

Power stroke shows myosin head releasing the ADP & phosphate and flexing as it pulls thin filament along -- binding of more ATP releases head from the thin filament

-as long as K+ gates are open -only especially strong stimulus will trigger new AP

Relative refractory period

Stiffening of the body

Rigor Mortis

Relaxation (steps 14 & 15)

Stimulation ceases and acetylcholinesterase removes ACh from receptors so stimulation of the muscle cell ceases

Period of resistance to stimulation

The Refractory Period

Excitation (step 5)

Voltage change in end-plate region (EPP) opens nearby voltage-gated channels in plasma membrane producing an action potential

Is there a difference in how the signal is transmitted in unmyelinated vs. myelinated fibers?

Yes

Neuromuscular Junctions: is enzyme that breaks down ACh & causes relaxation

acetylcholinesterase

Thin Filaments:Two strands of fibrous (F) ___ (contractile proteins) intertwined

actin

Chemical Excitation:If the sodium influx is great enough at the trigger zone, a long-distance signal that travels down the axon will be initiated. This is is an

action potential or nerve impulse

Chemial Excitation:If the stimulus is strong enough the depolarization will reach the area of the neuron called the

axon hillock or trigger zone

Thick Filaments are arranged in a

bundle with heads directed outward in a spiral array around the bundled tails

Rigor Mortis:Deteriorating sarcoplasmic reticulum releases

calcium

Skeletal Muscle Fibers: Sarcoplasmic reticulum is series of dilated

calcium storage sacs

Skeletal Muscle Fibers: Sarcolemma has tunnel-like infoldings or transverse (T) tubules that penetrate the cell and carry

carry electric current to cell interior

Epinephrine, norepinephrine and dopamine are classified as

catecholamines

Types of Neurotransmitters: Monoamines

catecholamines (epinephrine, norepinephrine & dopamine) indolamines (serotonin & histamine)

Impulse Conduction in Unmyelinated Fibers: Action potential in trigger zone begins ______ _______that travels to end of axon

chain reaction

Neuromuscular Toxins & Paralysis: Pesticides contain _____ _______ that bind to acetylcholinesterase & prevent it from degrading ACh

cholinesterase inhibitors

Action Potentials: Passes 0 mV & Na+ channels

close

Saltatory Conduction in Myelinated Fibers: Faster than the continuous or "chain reaction" type of

conduction

Thick Filaments: Made of 200 to 500 myosin molecules which are

contractile proteins

Metabotrophic Synapse Transmission: Neurotransmitter uses 2nd messenger such as ____ _____to alter metabolism of postsynaptic cell

cyclic AMP

Chemial Excitation: Na+ ions diffuse rapidly from the ECF into the cell. This makes the outside of the less positive and the inside of the cell more positive. The area of cell membrane is

depolarized.

Cessation & Modification of the Signal:Mechanisms to turn off stimulation-_______ of neurotransmitter away from synapse into ECF where astrocytes return it to the neuron

diffusion

What do we mean by "excitable cells"?:These are cells that self-generate ______ ________ and transmit signals along their membrane.

electrochemical impulses

catecholamines are

epinephrine, norepinephrine & dopamine

In order for skeletal muscle to contract it must be

excited but a motor neuron.

gut-brain peptides cause

food cravings

Thin Filaments: each subunit is a _____ ___ _____with an active s

globular (G) actin

Postsynaptic Potentials:excitatory neurotransmitters

glutamate & aspartate

Postsynaptic Potentials:inhibitory neurotransmitters

glycine & GABA

Action Potentials: More dramatic change in membrane produced where

high density of voltage-gated channels occur

Action Potentials: Negative overshoot produces

hyperpolarization

-nerve signal opens voltage-gated calcium channels -triggers release of ACh which crosses synapse -ACh receptors trigger opening of Na+ channels producing local potential (postsynaptic potential)

ionotropic effect

Cholinergic synapse produces

ionotropic effect

Chemical Excitation:The stimulus received at the dendrite changes the permeability of the local membrane to

ions

Action Potentials: once started goes to completion and can not be stopped

irreversible

Speed of Nerve Signal: ______ fibers have more surface area for signals

large

Cessation & Modification of the Signal:Mechanisms to turn off stimulation-synaptic knob reabsorbs amino acids and monoamines by endocytosis & breaks them down with ____ ______

monoamine oxidase

Neuromuscular Junctions: Neurotransmitter released from nerve fiber causes stimulation of

muscle cell (acetylcholine)

Skeletal Muscle Fibers: Sarcoplasm is filled with _____(bundles of parallel protein microfilaments called myofilaments)

myofibrils

Rigor Mortis: Activates ____ ____cross bridging & muscle contraction

myosin-actin

Stimulation of Nerves:The conducting cell of the nervous system is the

neuron.

Speed of Nerve Signal: The chemical signal is carried by ____________released by the presynaptic neuron.

neurotransmitters

Types of Neurotransmitters: Gases such as _____ _____can also function as neurotransmitters.

nitric oxide

Action Potentials: do not get weaker with distance

nondecremental

What do we mean by "excitable cells"?: Because there is a "+" charge on the ECF and a "-" charge on the ICF, at rest the membrane is

polarized.

Action Potentials: K+ gates fully open (K+ leaves) produces

repolarization

What do we mean by "excitable cells"?: All cells have a _____ ______ _______ that is due to an unequal distribution of ions.

resting membrane potential (RMP)

Relaxed versus Contracted Sarcomere: Their overlap changes as _____ shorten

sarcomeres

indolamines are

serotonin & histamine

Relaxed versus Contracted Sarcomere: Muscle cells shorten because their sarcomeres

shorten

Relaxed versus Contracted Sarcomere: Notice neither thick nor thin filaments change length during

shortening

Neuromuscular Toxins & Paralysis: Pesticides contain cholinesterase inhibitors that bind to acetylcholinesterase & prevent it from degrading ACh and causes

spastic paralysis & possible suffocation

Action Potentials: Called a

spike

In nerve and muscle cells, the resting membrane potential changes when the cells receive a

stimulus.

Neuromuscular Junctions: Synapse is region where nerve fiber makes a functional contact with its

target cell (NMJ)

Skeletal Muscle Fibers: Sarcolemma has tunnel-like infoldings or ______ ___ _____that penetrate the cell

transverse (T) tubules

Thin Filaments: Groove holds ________(regulatory protein) molecules blocking the active sites

tropomyosin

Thin Filaments:smaller, calcium-binding ______ (regulatory protein) molecules stuck to tropomyosin

troponin

Neuromuscular Junctions:Components of synapse= synaptic knob is swollen end of nerve fiber and contains

vesicles filled with ACh