Biology 11.1

structures and processes of the nervous system

movement of an impulse across a synapse

1. action potential arrives at presynaptic neuron
2. synaptic vesicles fuse to membrane of the axon
3. neurotransmitters are released into synaptic cleft and defuse across synapse
4. dendrites of cell membrane of the effector react
5. neurotransmitters bind to receptor proteins with trigger channels to open depolarizing postsynaptic membrane

nervous system

sends electrochemical messages throughout the body to maintain homeostasis. fast acting.

Homeostasis

a state of relative equilibrium within the body

Central Nervous System (CNS)

brain, spinal cord, (interneurons)

Peripheral Nervous System (PNS)

the sensory and motor neurons that connect the central nervous system (CNS) to the rest of the body.

stomatic nervous system

voluntary actions, Effectors skeletal muscles

autonomic nervous system

involuntary movements, smooth and cardiac muscles

sympathetic nervous system

fight or flight: releases epinephrine

parasympathetic nervous system

rest and digest, returns body to state of rest

Ephinephrine

increases heart rate
oxygen goes to skeletal muscles
raises blood glucose levels
dilates airways, (increased oxygen)

neurons

basic structural and functional unit of the nervous system
- responds to stimuli, conducts and sends electrochemical signals

Shwann cells

glial cell that forms myelin around the axon of neurons.
- protects, and speeds up rate of reaction

glial cell

nourish neurons, remove their waste and defend against infection
- surround, nourish, support, protect

Nerves

bundled axons that form neural "cables" connecting the central nervous system with muscles, glands, and sense organs

sensory receptors

receive stimuli and form a nerve impulse

sensory neurons

transmit impulses to interneurons in spinal cord and brain

Interneurons

Central nervous system neurons transmit impulses between the sensory inputs and motor outputs

motor neurons

neurons that carry outgoing information from the brain and spinal cord to effectors

Effectors

muscles, glands and or organs that respond to impulse from motor neurons

reflex arc

sensory receptor, sensory neuron, interneuron (in spine) motor neuron, and effector
is involved in a quick response to a stimulus

normal neuropathways

sensory receptor, sensory neuron, interneuron (in spine), interneuron (in brain) motor neuron, and effector
slower then reflex arc

Dentrites

Branches that reach out from the cell body and receive signals from surrounding neurons

cell body

contains nucleus and processes input from dendrites (if the input reaches threshold relays it to the axon)

Axon

the extension of a neuron, ending in branching terminal fibers, through which messages pass to other neurons or to muscles or glands

Axon bulb

The axon bulb is the area at the end of the axon, where signal transmission to the next neutron occurs.

Nodes of Ranvier

unmyelinated sections of a myelinated neuron that impulses "jump" between

all-or-none response

if threshold is not reached axon does not fire at all
if threshold is reached the cell fires entire length of the axon

threshold potential

minimum amount if stimulus needed to make a neuron fire

membrane potential

voltage across a membrane

resting membrane potential

the electrical charge of a neuron when it is not active

Neuron at rest

has Na+ on the outside and K+ on inside. is negative

sodium-potassium pump

uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell

membrane depolarization

sodium gates open and all sodium outside rushes in creating a reversal of charge (happens at nodes of ranvie)

hyper polarization

Refractory period
cell is more negative then it is a resting potential.Sodium potassium pump kicks on transporting sodium out and potassium in. returning cell resting potentail

membrane repolarization

Refractory period
Potassium channels open causing K+ to leave the cell and repolarize it. resulting in hyperpolarization

Synapse

the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron

neuromuscular junction

the synapse between a motor neuron and a skeletal muscle cell

action potential

a neural impulse; a brief electrical charge that travels down an axon

Neurotransmitters

chemical messengers that cross the synaptic gaps between neurons

summation

the combination of two or more excitatory neurotransmitters that reach the threshold of the other neuron

excitatory neurotransmitter

neurotransmitter that causes the receiving cell to fire, by depolarizing it (lowering threshold level)

inhibatory neurotransmitters

inhibit the next neuron from firing by triggering the opening of potassium gates resulting in hyperpolarization ( raising threshold level)

Actylcholine

One of the most common neurotransmitters in a neuromuscular junction

Norepinephrine

A neurotransmitter used by brian and some autonomic neurons . complements epinephrine
lack of: exhaustion
excess of: anxiety

Acetylcholinesterase

the enzyme that breaks down acetylcholine in the synaptic cleft

two was neurotransmitters are removed from the synapse

enzymes
reabsorption into the axon bulb