EFFERENT PNS HLSC MT#2

what is the anatomical arrangement of the ANS

• a preganglionic neuron communicates via synapses with a postganglionic neuron in the autonomic ganglia prior to innervating the effector organ or tissue

where does the sympathetic nervous system originate

• sympathetic nervous system originates in the thoracolumbar regions of the spinal cord, characterized by short cholinergic preganglionic fibres and long adrenergic postganglionic fibres

• cholinergic fibres release acetylcholine

• adrenergic fibres release norepinephrine

differentiate between acetylcholine and norepinephrine

• acetylcholine is an organic compound and neurotransmitter that is released by cholinergic fibres

• norepinephrine is a neurotransmitter and hormone that is released by adrenergic fibres

where do the preganglionic neurons of the sympathetic nervous system originate from

• preganglionic neurons originate from the thoracic and lumbar regions of the spinal cord

• they are generally short, and synapse onto long postganglionic neurons in. the sympathetic chain exception: in adrenal medulla and collateral ganglia (both located outside of sympathetic chain)

• preganglionic neurons exit ventral root of spinal cord then enter spinal nerves

what is the adrenal medulla

• secretes catecholamine hormones

• is a modified postganglionic neuron of sympathetic nervous system originates

• secretes 20% norepinephrine and 80% epinephrine

• also secretes some dopamine

• hormones are secreted directly into the blood and therefore have widespread effects

what are the layers of the adrenal medulla (top to bottom)

1. connective tissue capsule on top

2. zone glomerulosa

3. zone fasciculata

4. zone reticularis

5. medulla

compare the origins of the preganglionic neurons of the sympathetic and parasympathetic nervous systems and compare the corresponding length of the pre and post ganglionic neurons of each system (hint: apparent by their physiology)

• SYMPATHETIC: preganglionic neurons originate in the spinal cord (thoracic and lumbar regions) and are short in length so that there is a fast connection to the spinal cord (CNS) in times of fight or flight

-exceptions to this are adrenal medulla and collateral ganglia, which are outside of the sympathetic chain

• PARASYMPATHETIC: preganglionic neurons originate in from the brain stem and sacral region of the spinal cord (think para means ABOVE AND BELOW SYMPATHETIC). pre are long in length and synapse onto short post in ganglia close to effector organ or tissue. think: they have more time because no near death situation, so they can be long

which cranial nerves are associated with the parasympathetic nervous system

• neurons are long and synapse onto short postganglionic neurons in ganglia close to the effector organ or tissue

• include those of cranial nerves III (oculomotor), VII (facial), IX (glossopharyngeal), and X (vagus) as well as the pelvic spinal nerves

which neurotransmitters are found in the ANS synapses

• acetylcholine: released from cholinergic neurons and binds to cholinergic receptors

• norepinephrine: released from adrenergic neurons and binds to adrenergic receptors

in the ANS, which neurons are cholinergic and which neurons are adrenergic

• all preganglionic neurons are cholinergic in ANS (sympathetic and parasympathetic)

• postganglionic neurons in sympathetic are adrenergic

• postganglionic neurons in parasympathetic are cholinergic

what are the two kinds of cholinergic receptors

• nicotinic receptors:

• muscarinic receptors