CHAPTER 11 - efferent division, autonomic and somatic motor control

what are the 2 divisions of the nervous system

1. autonomic

2. somatic

what is autonomic division

processes occuring automatically

what is somatic division

processes with conscious control

what are the 2 divisions of the autonomic division

• sympathetic

• parasympathetic

what are antagonistic branches

opposing actions to cause homeostasis

i.e: parasympathetic and sympathetic

what is parasympathetic

• rest and digest

• restore body functions

• inhibitory

what is sympathetic

• fight or flight

• energetic rection

• excitatory

how does behavioural coordination work

1. autonomic (parasympathetic or sympathetic)

2. endocrine (hormone released)

3. behaviour (action)

what are the things controlled by autonomic centers in the brain

• water balance

• temperature

• hunger

• respiration

• cardiac

• vomiting

• swallowing

where do sympathetic pathways originate

thoracic and lumbar section of the spinal cord

length of pre and post ganglion in sympathetic pathways

pre ganglion - short

post ganglion - long (to reach target)

where do parasympathetic pathways originate

brain stem, sacral region of spinal cord

length of pre and post ganglion in parasympathetic pathways

pre ganglion - long

post ganglion - short

what neurotransmitter do sympathetic pre ganglion neurons release

acetylcholine

what neurotransmitter do parasympathetic pre ganglion neurons release

acetylcholine

what neurotransmitter do sympathetic post ganglion neurons release

norepinephrine “fight or flight”

what neurotransmitter do parasympathetic post ganglion neurons release

acetylcholine “rest and digest”

what do receptor does pre ganglion acetylcholine bind to
(both parasympathetic and sympathetic)

nicotinic receptors

what receptor does norepinephrine bind to in sympathetic post ganglion

adrenergic receptors

what receptor does acetylcholine bind to in parasympathetic post ganglion

muscarinic receptors

what division is responsible for fight or flight

sympathetic

what division is responsible for rest and digest

parasympathetic

what is a ganglion

cluster of nerve cell bodies outside of the CNS

what is a neuroeffector junction

a synapse between post ganglion and its target

what are varicosities

swollen regions along axon terminals of autonomic neurons

• contain vesicles filled with neurotransmitters

what are the autonomic target cells

• smooth muscle

• cardiac muscle

• exocrine glands

• endocrine glands

• lymphoid tissue

• adipose tissue

where does neurotransmitter synthesis occur

in varicosities

Eight steps of norepinephrine release at a varicosity of a sympathetic neuron

1. action potential arrives at varicosity

2. depolarization opens voltage-gated Ca2+ channels

3. Ca2+ triggers exocytosis of synaptic vesicles (norepinephrine)

4. Norepinephrine binds to adrenergic receptors on target

5. receptor activation ceases when norepinephrine diffuses away from the synapse

6. norepinephrine is removed form the synapse

7. norepinephrine can be recycled into synaptic vesicles

8. norepinephrine is metabolized by monoamine oxidase

2 key parts of adrenal glands

• adrenal cortex - true endocrine gland

• adrenal medulla - modified synaptic ganglion

primary hormone of adrenal glands

norepinephrine

how do adrenal glands secrete neurotransmitters

• long preganglionic sympathetic neuron transmit a signal from spinal cord to adrenal medulla

• sympathetic nerves release ACh onto adrenal medulla cells

• Acetylcholine binds to receptors on adrenal cells, causing them to become excited.

• excitement opens channels that let calcium ions into the cells

• The calcium triggers the adrenal cells to release adrenaline (epinephrine) and noradrenaline (norepinephrine) into the bloodstream.

CNS origin of sympathetic neurons

1st - 2nd thoracic lumbar segments

CNS origin of parasympathetic neurons

midbrain, medulla, 2nd- 4th sacral segments

location of peripheral ganglia (sympathetic)

vertebrae (3 of them are located on aorta)

location of peripheral ganglia (parasympathetic)

on/near target cells

what releases nerurotransmitters for sympathetic and parasympathetic

varicsosities

what neurotransmitter is released at sympathetic target cells

norepinephrine (adrenergic neurons

what neurotransmitter is released at parasympathetic target cells

acetylcholine ( cholinergic neurons)

what happens after inactivation of neurotransmitters in sympathetic pathway

recycle back into varicosities or diffusion

what happens after inactivation of neurotransmitters in parasympathetic pathway

enzyme breakdown or diffusion

receptor on both sympathetic and parasympathetic target cells

adrenergic

pre ganglion synapse on both parasympathetic and sympathetic pathways

ACh on nicotinic receptors

post ganglion synapse on sympathetic pathways

norepinephrone on alpha or beta adrenergic receptors

post ganglion synapse on parasympathetic pathways

ACh on muscarinic receptor

what is a neuromuscular junction

connection between a neuron and a muscle where signals from neuron tell the muscle to contract

4 components of a neuromuscular junction

1. motor neuron: neuron carries signal from spinal cord to muscle

2. synaptic cleft: tiny gap between neuron and muscle fiber

3. motor end plate: part of muscle fibers that contain the receptors

4. acetylcholine: neurotransmitter that triggers action

6 steps in somatic neurotransmitter release

1. action potential arrives: neuron signal reaches the presynaptic membrane

2. calcium channels open: voltage-gated calcium channels allow Ca2+ to enter neuron ending

3. release of ACh: Ca2+ trigger ACh release

4. ACh binds to receptor: ACh travels across synaptic cleft, binds to nicotinic receptors on motor end plate

5. muscle contraction: binding causes ion channels in muscle to open ending in muscle contraction

6. ACh breakdown: acetylcholine breaks down ACh into acetyl and choline, allows muscle to relax

number of neurons in efferent path (somatic)

1 long neuron

number of neurons in efferent path (autonomic)

2 (preganglion and post ganglion)

neurotransmitter/receptor at neuron target synapse (somatic)

ACh/ nicotinic

neurotransmitter/receptor at neuron target synapse (autonomic)

ACh/ muscarinic OR norepinephrine/ alpha or beta adrenergenic

target tissue of somatic motor pathway

skeletal muscle

target tissue of autonomic pathway

smooth, cardiac muscle; some endocrine, exocrine glands; some adipose tissue

neurotransmitters are released from (somatic)

axon terminals

neurotransmitters are released from (autonomic)

varicosities and axon terminals

effects on target tissue (somatic)

excitatory (muscle contraction)

effects on target tissue (autonomic)

excitatory (sympathetic) or inhibitory (parasympathetic)

function of somatic systems

posture and movement

function of autonomic systems

visceral function, movement of internal organs, secretion, controls metabolism