sympetatic innervation of GI

via postganglionic adrenergic fibers

has three parts

1- celiac

2-superior and inferior mesenteric

3-hypogastric plexses

where do sympetatic fibers end on GI?

sypetatic fibers do not directly innervate the GI

terminate on neurons in intermural plexuses

Vasoconstrictor sympethatic fibers?

2-other sympetatic fibers?

where do they innervate the GI?

1-Directly innervate blood vessels of GI

2-Glandular structures 

Stimulation of sympetatic input

what does it do to GI ?

2-inhibits motor activity of muscularis externa

3- stimulates muscularis mucosae

MUSCULARIS MUCOSA

this layer of smooth muscle fibers and elastic connective tissue is located immediately beneath the lamina propria.

MUSCULARIS EXTERNA:

This layer is usually composed of two smooth muscle layers: an inner layer with the smooth muscle fibers arranged circularly around the alimentary canal, and an outer layer with the smooth muscle fibers arranged longitudinally with the long axis of the alimentary canal.

Do sympetatic nerves inhibit the contraction of muscularis DIRECTLY?

if not how do they do that.?

NO. they don't inhibit contraction of muscularis directly.

sympetatic nerves influence neuranal circuits

in ENTERIC nervous sys.

and they input to smooth muscle cells

Sympetatic nerves ---------blood

to muscularis externa and -----------

1-reduce blood flow

2- inhibit motor activity of muscularis extrena

Activation of sympetatic Nervous system

---------- secretory activity of gastrointestinal tract.

(sympetatic)

Reduces

Secretion

Sympetatic nerve fibers can be

both :1---------------

2------------------

Cholinergic :produce Ach

and adrenergic : Norepinephrine

Sympetatic nerve fibers are mostly

Adrenergic!!!!!!!!!!

Sympetatic NS (adrenergic neurons=produce NE)

------------------smooth muscle?

----------------------Sphincters?

Relax smooth muscle in wall

Contract Sphincter

Contract Mucosa

Incresae salivation

Parasympathetic Nerves of GI

are /?????????

1- Vegus: upper intestinal tract

(up to transverse colon)

2- pelvic nerves: lower intestinal tract

(remainder of colon,rectum,anus)

Most of the parasympethatic nerves are?

Cholinergic :

Produce Ach

Preganglionic fibers of sympetatic NS

are ----------

and synapse in ganglia -----  GI.

Sympetatic preganglionic fibers are

 short and

synapse outside the GI tract

Preganglionic fibers of parasympathetic fibres

are ---------

and synapse in ganglia -------------wall of GI tract.

parasympathetic preganglionic fibers

LONG

INSIDE

parasympetatic fibers terminate

on the ganglion cells in the intermural plexsus.

ganglion directly touches sectretory cells of GI

Parasympethatic ------------size or amplitute of slow wave

Parasympethatic 

Incresaes

amplitute of slow wave

The ------------ of Slow wave is MAINLY modulated by hormones and intrinsic and extrinsic nerves.

AMPLITUTE is manily modulated

The frequency is not(less modulated)=is characteristic of wave.

Action potential cant occure until slow wave brings

the action potential to threshhold.

TRUE? or FALSE?

TRUEEEEEEEEEEE

Contraction occures when depolarization exceeds

threshold for contraction

TRUE? OR FALSE?

TruE:)

DEPOLARIZATION caused by slow wave 

>>>>>>>>>>>>>> 

Threshold for contraction

OSCILATION OF RESTING MEMBRANE POTENTIAL

ARE CALLED?-------------

SLOW WAVES

BASIC ELECTRICAL RHYTHM

SLOW WAVES ARE GENERATED BY?

INTERSTITIAL CELLS OF CAJAL

(HAVE PROPERTIES OF FIBROBLASTS AND SMOOTH MUSCLE CELLS)

• if the peak of slow wave is above threshohold for action potential

one or more action potential may be triggered during the peak of the slow wave

Resting membrane potential of smooth muscle is

-------------than skeletal muscle

smaller

ranges from -40 to -80 mV

Why is resting membane potential in GI lower than skeletal muscle?

because of Na/K ATPase

RESTING membane potential in other excitable tissue is------------

but --------------in GI smooth muscle ----------

• in other excitable tissues is constant 
• but varies in smooth muscle