Peripheral Nervous System II

Question 1

autonomic nervous system (ANS)

Answer 1

• involuntary branch of PNS

- innervates cardiac and smooth muscles, glands and organs

Question 2

somatic nervous system

Answer 2

• subject to voluntary movement

- innervates skeletal muscle

Question 3

ANS sympathetic system

Answer 3

• dominates in emergency or stressful situations
• “flight-or-flight”
• promotes response that prepare body for strenuous physical activity
• everything increases except digestion

Question 4

ANS parasympathetic system

Answer 4

• dominates in quiet, relaxed situations
• “rest-and-digest”
• promotes body maintenance activities like digestion
• everything slows except digestion

Question 5

sympathetic anatomy

Answer 5

• preganglionic nerve fibers originate in the thoracic and lumbar regions of the spinal cord
• they synapse with postganglionic cells in the sympathetic ganglion chain (sympathetic trunk)
• long post fibers originate in the ganglion chain and end on effector organ

Question 6

parasympathetic anatomy

Answer 6

• preganglionic fibers arise from the cranial and sacral areas of CNS
• synapse on postganglionic cells found in the terminal ganglia
• terminal ganglia lie in or near the effector organ
• short postganglionic fibers end on the cells of the organ itself

Question 7

ANS neurotransmitters

Answer 7

• all preganglionic and parasympathetic post release acetylcholine (ACh)
• sympathetic post fibers release norepinephrine (NE)

Question 8

cholinergic

Answer 8

cells that release ACh

Question 9

adrenergic

Answer 9

cells that release norepinephrine

Question 10

dual innervation

Answer 10

• most organs are innervated by both ANS divisions
• usually produce opposite effects in an organ
• allow for precise control over organ’s activity

Question 11

exceptions to dual innervation

Answer 11

• most arterioles and veins (sympathetic)
• most sweat glands (sympathetic)
• salivary glands are stimulated by both but each stimulates different forms of saliva

Question 12

adrenal medulla

Answer 12

• modified sympathetic ganglion
• secretes 80% of epinephrine and 20% of norepinephrine in response to sympathetic stimulation
• reinforce sympathetic activity

Question 13

ANS receptors

Answer 13

-tissues innervated by the ANS possess one or more of several different receptors types for ACh and NE

Question 14

ANS receptors: cholinergic

Answer 14

• nicotinic

- muscarinic

Question 15

ANS receptors: adrenergic

Answer 15

• alpha 1 and 2

- beta 1 and 2

Question 16

CNS control of autonomic function

Answer 16

• ANS is tied to emotional states by connection to prefrontal association areas
• hypothalamus: integrating autonomic, somatic and endocrine response
• medulla: directly responsible for autonomic output
• autonomic reflexes: (urination, defecation, penile erection) are integrated at the spinal cord

Question 17

somatic nervous system

Answer 17

• axons for motor neurons originate in spinal cord and end on skeletal muscle
• motor neuron releases ACh to stimulate muscle contraction
• motor neurons are final common pathway by which the CNS controls muscle/skeletal activity

Question 18

neuromuscular junction

Answer 18

• axon terminal of motor neuron forms with a muscle cell
• motor neuron releases +ACh to stimulate muscle contraction
• ACh binds to special receptor-channels on the motor end plate
• ACh binding triggers the opening of non-specific cation channels
• ion depolarize the otor end plate producing the end-plate potential (EPP)
• current depolarizes adjacent membrane and triggers an action potential
• stimulates contraction

Question 19

acetylcholinesterase (AChE)

Answer 19

• an enzyme in the motor end plate
• inactivates ACh
• ending the EPP and contraction

Question 20

chemical agents and diseases that affect neuromuscular junctions

Answer 20

1. black widow venom causes and explosive release of ACh.Leads to respiratory failure because the diaphragm can’t relax to take in air.
2. Botulinum toxin blocks release of ACh from motor neuron. Muscles cant contract leading to respiratory failure.
3. Curare blocks the ACh receptors preventing action potentials from occurring. Causes paralysis and respiratory failure.
4. Organophosphates irreversibly inhibit AChE. Muscles are stuck in depolarized state because the enzyme AChE isn’t produced to break down ACh.
5. Myasthenis Gravis causes the body to produce antibodies that attack the motor endplate causing poor muscle contraction.