Structures within a synapse

Summation

refers to the algebraic addition of the excitatory and inhibitory effects of many stimuli applied to a nerve cell body

synaptic end bulbs

1. axodendritic: from axon to dendrite 2. axosomatic : from axon to soma 3. axoaxonic : from axon to axon

Sequential Synaptic Events

1.Depolarization of pre-synaptic neuron at the axon terminal 2.opening of voltage sensitive Ca+ channels 3.Infrux of Ca into the axon terminal area 4.Increase in Ca cause fusion of synaptic vesicles to plasma membranme & release NT into synaptn cleft

Neural Stem Cells

-Experimentally, adult neural cells can be derived from these primitive cells. Preliminary stem cell transplantation have been completed in Ptes. with motor neuron disease ALS. Neurons survive and proliferate only if they are immature stem cells.

GABA (gamma-aminobutyric acid)

-Found in CNS; inhibitory; 20% of synapses in brain release GABA; decreas.anxiety; some anti-anxiety drugs work to enhance its effects; not enough GABA produced may lead to neural over-activity and seizures

Neural Stem Cells

-Nervous System has limited ability to repair itself post injury. Mature neurons cannot reproduce. Hard to obtain neural stem c.fm brain. Neural stem are immature and undifferenciated; can develop into both neurons and glial cells

Synapse

-contact point b/t neurons Presynaptic & Postsynaptic neurons

Synaptic end bulbs

-enlarged area at the end of the axon terminal; consists of membrane enclosed sacs, (synaptic vesicle) which contain molecules of neurotransmitter.

Synaptic Junction

-has 3 main parts: 1.synaptic end bulb 2.synaptic cleft 3.postsynaptic membrane

Acetylcholine

-major conveyor of information in the PNS; all motor neurons use Ach at neuromuscular junction; may excite or inhibit at ANS synapses in PNS; also found CNS and involved in control movement.

Synapses

-refers to the contact point b/t a neuron & another neuron, muscle or gland

Dopamine

-released in many areas of the brain; in the midbrain inhibits basal nuclei activity; if decrease inproduction of dopamine, basal nuclei become +active & increase in muscle tone characteristic of Parkinson disease. Dopamine release is excitatory and creates a sense of well-being

Norepinephrine

-widely found in brain and portions of the ANS; typically excitatory, creating a sense of well-being; essential in producing fight or flight reaction to stress; low levels may lead to depression

3. motor end plate

. The portion of the muscle fiber which corresponds with the post synaptic membrane of the nerve fiber (a part of the muscular system)

Chemical synapse

. stimulation of the neuron is caused by the release of a chemical by the presynaptic neuron . synaptic end bulbs contain chemicals referred to as neurotransmitters.

2. neuroglandular junction

. the contact point b/t a motor neuron and a gland

1. neuromuscular/myoneural junction

. the contact point b/t a motor neuron and skeletal muscle

Inhibitory postsynaptic potential (IPSP)

.ref.to an increase in the internal negativity of the cellular membrane that results in voltage moving further away from threshold value .Due to opening of chemically gated CI- and K+ channel opening; CI- enters while K+ leaves the cell. Decrease the likelihood for an AP to occur.

Excitatory postsynaptic potential (EPSP)

.refs to a slight decrease in negative voltage of post synaptic membrane when stimulated by pre synaptic terminal. .Due to opening of chemical gated channels allowing intracellular infrux of positive ions .A local event that decrease in strength from the point of excitation .Increases the likelihood that a AP will occur

cont. Sequential Synaptic Events

5.chemically gated channels of post synaptic membrane open 6.post-synaptic potential graded as inhibitory or excitatory depending upon ion flow Innhibitory: net flow - ions in Excitatory : net flow + ions in 7. if reaches threshold, all or none AP will occur.

Characteristics of Neurotransmitter

a.chemicals b.usually amino acids c.stored in synaptic vesicles d. calcium ions enter in from the opening of voltage gated calcium channels e. exocytosisof synaptic vesicles. i.e. increase in Ca+ causes the vesicles to fuse with plasma membrane f.release of NT into the synaptic cleft

Postsynaptic Neurons

conduct impulses or electrical signal away from a synapse

Presynaptic Neurons

conduct impulses or electrical signal towards a synapse

temporal

the sum of inhibitory and excitatory effects of stimuli arriving at different times from the environmen. (many coming in the road, one after the other)

spatial

the sum of inhibitory and excitatory effects of stimuli converging from many different conditions in the environment. (at one time/all at once)