halliwell: lec 5

autonomic nervous system

autonomic nervous system

• operates slowly over time & entire body

• not under conscious control

• heart rate, Gi, etc

• involuntary or vegetative nervous system

what does ANS control in hypothalamus

nuclei

how do para and sympathic divisions work

• in opposite

• both are always on but may differe in activity

• continuously regulate internal state (autonomic tone)

where do parasympathetic preganglionic fibers originate

• cranial outflow (brainstem)

• sacral outflow (spinal cord)

Cranial Outflow (Brainstem)

• : Originates in the midbrain, pons, and medulla.

• 4 cranial nerves

  • CN3: ocularmotor

  • CN 7: facial

  • CN9: glosspharyngeal nerve

  • CN 10: vagus nerve

• 
  

Sacral Outflow (Spinal Cord)

• Originates in the lateral horn of the sacral region (S2–S4)

• exit via pelvic nerves

parasympathetic neuronal pathway & fiber lengths

• preganglionic neurons:

  • cell bodies brain stem nuclei & lateral horn of sacral spinal cord (side)

  • hypothalamus sends signals to neurons → autonomic response

  • long axons innervate terminal ganglia

• Terminal Ganglia:

  • synapse occurs

  • close/directly within wall of target organ

  • short

• Postganglionic Neurons:

  • receive signal from pre, directly innervate target organs

  • short, close to target

does parasympathetic innervate blood vessels

NOOO

where do terminal ganglia innervate

• eyes, tear & salivary gland, heart, bronchi, lungs, stomach, liver, pancreas, intestines, rectum, bladder, ureter

where are sympathetic pre-ganglionic cell bodies located

in intermediolateral column of spinal cord

where do pre-ganglionic fibers leave

• spinal cord between T1& L2

• thoracolumbar division

3 locations sym pre-ganglionic fibers synapse on

• sympathetic chain ganglia

• collateral ganglia

• adrenal medullae

where are sympathetic chain ganglia lie

bilateral to vertebral column

where are collateral ganglia found

midline of abdomen & pelvis

what are the centers of adrenal gland

adrenal medullae

on top of kidneys

where do sympathetic chain innervate

• eye, tear & salivary glands, blood vessels in neck & head, sweat glands

• piloerector muscles (goosebumps on skin)

• heart, bronchi, lungs

where do collateral ganglia innervate

• diaphragm, liver, stomach oancreas

• instestines, rectum, bladder, ureter

what are adrenal medullae

• modified post-ganglion (chromaffin) cells

• no axons

• secrete transmitter directly into bloodstream

• secrete hormones: adrenaline (epinephrine), nonadrenaline (nonepinephrine)

• effect: inc heart rate, ince BP, dilate pupils, stop digestion

neurotransmitter in sympathetic pathway

• Preganglionic Fiber

  • lightly myelinated axon (classified as a B-type fiber)

  • releases Acetylcholine (ACh) at the ganglion

• Postganglionic Fiber

  • unmyelinated axon that extends to the target organ

  • releases Norepinephrine (NE / noradrenaline) @ target

  • digestive and cardiovascular structures

neurotransmitter in parasympathetic pathway

• ACh exclusively

• Preganglionic Fiber

  • lightly myelinated axon (classified as a B-type fiber)

  • releases Acetylcholine (ACh) at the ganglion

• Postganglionic Fiber

  • unmyelinated axon that travels to the target

  • releases Acetylcholine (ACh) at the effector organs

  • smooth muscle in the gut, glands, and cardiac muscle

Adarenal Medulla pathway in sympathetic nervous system

Direct Preganglionic Innervation:

• lightly myelinated preganglionic axon synapse directly on adrenal medulla

• rel ACh to neuroendocrine (chromaffin) cells

adrenal medulla:

• secretes epinephrine and norepinephrine directly into adjacent blood vessels

parasympathetic vs sympathetic pathway

• sympathetic pathway

  • uses norepinephrine

  • rel Ach to nicotinic receptor (Na+/K+ ligand- gated)

  • rel norepinephrine to adrenergic receptor (GPCR)

• parasympathetic pathway

  • uses Ach

  • rel Ach to nicotinic receptor (Na+/K+ ligand- gated)

  • rel Ach to muscarinic receptor (GPCR)

effects of parasympathetic

• constrict pupils

• inc saliva prodction

• reduces heart rate

• constricts bronchia

• stim digestive organs, pancreas, gall bladder

• constricts urinary bladder → pee

• stim erection in sex organs

effects of sympathetic

• dilates pupils

• inh saliva production

• dilates bronchia

• rise heartrate

• inhibit: digestive organs, gallbladder, pancreas

• stim adrenal medulla → rel adrenaline & noradrenaline

• relaxes urinary bladder

• stim orgasm