Rutgers Functional Human Anatomy Lec 9 (Autonomic Nervous System)

The autonomic nervous system (ANS) functions.......?

outside of our conscious awareness

the ANS works hard to maintain....?

homestasis

the ANS controls?

body temp and internal systems (respiratory, digestive, reproductive, cardiovascular, excretory)

Neurons of autonomic nervous system

efferent axons: innervate visceral organs

afferent axons: originate in visceral sensory

receptors

Neurons in somatic nervous system

efferent axons: innervate skeletal muscles

afferent axons: originate in the skeletal

muscles, joints, and skin

subdivisions of ANS

sympathetic and parasympathetic

sympathetic divison

- also known as thoracolumbar division

- fight or flight system

- most active during time of stress, excitement, emergency

preganglionic neuron (sympathetic)

- located in lateral horns of spinal segments (T1-L2)

- release acetylcholine (ACh) which stimulates ganglionic neurons

ganglionic neurons

located in:

sympathetic chain ganglia - near spinal cord/thoracic cavity (paired)

collateral ganglia - run to the organs of abdominal cavity (unpaired

adrenal medulla - to organs of the body

postganglionic fibers (sympathetic)

- release norepinephrine

organs during sympathetic (fight or flight)

-heart/respiratory rate increases

- digestive system, urination system & reproductive system inhibited

- pupils dilate

Adrenal medulla

-releases epinephrine (adrenaline) and norepinephrine (noradrenaline)

- circulating blood distributes these hormones throughout the body

parasympathetic division

- also known as craniosacral division (rest & digest)

- more active during resting conditions

preganglionic neuron of parasympathetic division

-located in brainstem and lateral portion of anterior horns of spinal segments (S2-S4)

-release ACh, excite & stimulates ganglionic neurons

- form distinct pelvic nerves

ganglionic neurons of parasympathetic

located in peripheral ganglia within or adjacent to the target organs

Enteric Nervous System (ENS)

- 3rd division of autonomic nervous system

- neurons located in walls of digestive tracts

- many visceral reflexes are initiated by ENS, but receive input from ANS

effects of sympathetic stimulation

-increase alertness (pupil dilation)

- feeling of energy & euphoria (excitement, high adrenaline)

- increased cardiovascular activity (faster Hr, more blood to muscles)

- increased respiratory activity (more O2 in)

- elevation in muscle tone

- mobilization of energy reserves ( fuel muscles, getting body ready for action)

effects of parasympathetic stimulation

- constrict pupils

- secretion of digestive glands

- secretion of hormones promoting nutrient absorption

- increased smooth muscle activity along digestive tract

- stimulate and coordination of defecation

- contracting urinary bladder during urination

- reduction of Hr

- constrict respiratory passageway

- sexual arousal

relationship between sympathetic and parasympathetic divisions

-duals innervation: most vital organs are innervated by both divisions

-both divisions often have opposite/ antagonistic effects

-part of maintaining homeostasis

release of ACh

sympathetic - preganglionic release ACh, postganglionic release noreepinephrine

parasympathetic - both pre- & postganglionic release ACh