ANS Chapter 14
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describe the motor neurons in the somatic nervous system
- single neurone from the CNS to the effector organ
- heavily myelinated axon
- Neurotransmitter = ACh
- effector organs: skeletal muscle
- Effects: stimulatory
describe the motor neurons in the Autonomic nervous system
- 2 types: sympathetic and parasympathetic
- Sympathetic: a two-neuron chain. Lightly myelinated preganglionic axons use ACh to act on either the adrenal medulla or a non-myelinated ganglion. The effector releases NE and acts on smooth muscle. The effect is either stimulatory or inhibitory.
- Parasympathetic: a lightly myelinated preganglionic axon releases ACh to a non-myelinated ganglion. The non-myelinated post ganglion releases ACh on smooth muscles to have stimulatory or inhibitory effects on the effector organ (smooth muscle)
Define the role of the parasympathetic division
promotes maintenance activities and conserves body energy during "rest and digest" activities
Define the role of the sympathetic division
- mobilize the body during exercise, excitement, emergency, or embarrassment
- fight-or-flight responses
Contrast the origin of the parasympathetic division vs the sympathetic division.
- Parasympathetic: craniosacral part
- Sympathetic: thoracolumbar part.
Parasympathetic preganglionic fibers are ______; postganglionic fibbers are ______
Sympathetic preganglionic fibers are ______; postganglionic fibbers are ______
Contrast the degree of branching pre- and post ganglionic fibers in parasympathetic and sympathetic systems
- parasympathetic: minimal
- Sympathetic: extensive
Contrast the function of the sympathetic and parasympathetic nervous systems.
- Sympathetic: prepares the body for activity
- Parasympathetic: maintenance functions. "rest and digest"
In the parasympathetic nervous system, all preganglionic and postganglionic fibers release ______ neurotransmitters.
In the sympathetic nervous system, all preganglionic release ______ neurotransmitters, all post ganglionic fibers release ________ neurotransmitters
- ACh (preganglionic)
- Norepinephrine (postganglionic)
Name the neurotransmitters released by pre and postganglionic sympathetic and parasympathetic neurons and by somatic motor neurons.
- Sympathetic: preganglionic = ACh; post = NE
- Parasympathetic: ACh in both
- Somatic: ACh
ACh binds to _______ receptors. NE and epinephrine bine to _______ receptors.
- adrenergic receptors
Nicotinic receptors bind ___. Describe where they are found. Are they stimulatory or inhibitory.
- Sarcolemma of skeletal muscle cells at the NMJ
- all postganglionic neurons
- ALWAYS STIMULATORY
What is the affects of ACh at the nicotinic receptor?
- always stimulatory
- opens ion channels --> depolarizing the post synaptic cell
Muscarinic receptors bind ___. Describe where they are found. Are they stimulatory or inhibitory.
- Binds: ACh
- found:all effector cells stimulated by postganglionic cholinergic fibers
- Effect: can be inhibitory or excitatory
Two major classes of adrenergic receptors. What do these receptors bind?
- alpha receptors
- beta receptors
- bind: ACh
State the effects of the parasympathetic and sympathetic nervous system on the adrenal medulla
- Parasympathetic: none
- Sympathetic: stimulates medulla cells to release NE and epinephrine
State the effects of the parasympathetic and sympathetic nervous system on the Heart (muscle)
- Para: decrease rate, slow heart
- Sympathetic: increase rate and force of heart beat
State the effects of the parasympathetic and sympathetic nervous system on the Heart (blood vessels)
- Para: no effect
- Sympathetic: vasodilation
State the effects of the parasympathetic and sympathetic nervous system on the Urinary bladder/ urethra
- contracts smooth muscle of the bladder wall
- relax urethral sphincter
- promotes voiding
- relaxes smooth muscle of the bladder wall
- constrict urethral sphincter
- inhibits voiding
State the effects of the parasympathetic and sympathetic nervous system on the lungs
- Para: constricts bronchioles
- sympathetic: dilates bronchioles
State the effects of the parasympathetic and sympathetic nervous system on the digestive tract
- increase peristalsis
- increase secretion by organs
- relax sphincters to allow food movement
- decrease activity of glands and muscles
- constrict sphincters
State the effects of the parasympathetic and sympathetic nervous system on the penis
- para: erection
- sympathetic: ejaculation
State the effects of the parasympathetic and sympathetic nervous system on the vagina
- erection of the clitoris
- increase vaginal lubrication
- Sympathetic: vagina constricts
State the effects of the parasympathetic and sympathetic nervous system on the blood vessels
- para: little to no effect
- sympathetic: constricts most
- increases BP
- constricts abdominal and skin vessels to divert blood to the heart, muscles and brain
- epinephrine weakly dilates vessels of skeletal muscles
Explain how the adrenal medulla can affect receptors on various effector organs despite the fact that its cells have no axons.
Explain the statement "the adrenal medulla is a modified sympathetic ganglion"
- The adrenal medulla is stimulated by preganglion via ACh. ACh binding causes the adrenal medulla to release NE and epinephrine hormones into the blood stream. When blood flows through the effector organ, the hormone causes an effect on the organ.
- the statement means that it causes similar effects on the target organ, but uses a different mechanism.
define "sympathetic tone"
- keeps blood vessels in a continual state of partial constriction
- controls blood pressure, even at rest
sympathetic fibers fire ____ rapidly to _____ blood vessels and cause blood pressure to rise
sympathetic fibers fire _____ rapidly to prompt vessels to _____ to decrease blood pressure
Define "parasympathetic tone"
- The parasympathetic division normally dominates
- heart activity
- the activities of smooth muscle in digestive and urinary tract organs
- it activates most glands (except for adrenal and sweat glands)
The main integrative centre of ANS activity
Describe what the brain stem is responsible for in regulating the ANS
- pupil size
- blood pressure
Describe what role the spinal cord plays in regulating the ANS
- relaxes for urination
- erection and ejaculation
Control over urination, defecation and erotic thoughts
the cardiac centre and respiratory centre for the ANS
State some controls of the hypothalamus on the ANS
- heart activity
- blood pressure
- body temperature
- water balance
- endocrine activity
- emotional states
- biological drives
- reaction to fear
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