Autonomic Nervous System Flashcards
What comprises the ANS? (3)
- the Sympathetic NS
- the Parasympathetic NS
- the Enteric NS
Autonomic sensory neurons. Where are receptors located? What is there function?
the main input
- sensory receptors are located in blood vessels, organs and muscles
- function is to monitor internal environment e.g. chemoreceptors
Autonomic motor neurons. What do they regulate? Where are effectors located? What are they controlled by?
Regulate visceral function
- Can produce exciting or inhibiting activities in the tissues
- effectors are in smooth muscle, cardiac muscle and glands
- controlled by the hypothalamus and spinal cord
Autonomic motor responses.
Most are not voluntarily controlled
e. g.
- pupil dilation/constriction
- rate and force of contraction of heart
Autonomic motor neurons… 2 motor neurons consist in a unit.. Which NT’s are involved?
- pre-ganglionic: cell bodies in CNS > autonomic ganglion
- post-ganglionic: autonomic ganglion > effectors
- NE & ACh
IN CONTRAST Somatic motor neurons… only have 1 motor neuron in the unit
extend from the CNS > straight to the skeletal system
There are 2 different ganglia in the ANS..
- sympathetic ganglia
- which are close to the spine and have many posganglionic neurons > stimulating many effectors - parasympathetic ganglia
- which are close to the target organ and have only ONE posganglionic neuron > stimulating ONE effector
Define ganglia
a cluster of neuronal cell bodies located in the PNS
= are the autonomic NS relay stations
craniosacral
= parasympathetic
thoracolumbar
= sympathetic
The ANS has 2 output divisions
the SNS and the PNS
- SNS is also called the thoracolumbar division
- F or F
- increases alertness and metabolic activities - PNS is also called the cranial sacral division
- R and D
- conserve/restore energy during times of rest
- directed to smooth muscle and glandular tissue
Which division are our organs supplied by?
most organs are innervated by both
What are some structures that only receive on SNS?
sweat glands, muscles attached to hair follicles, kidney, adrenal medulla, spleen, most blood vessels
How are autonomic neurons classified?
by the NT’s that are released by them
Cholinergic Neurons. What do they release? Which neurons in the ANS are cholinergic?
Ach
- all sympathetic and parasympathetic pre-ganglionic neurons
- all sympathetic post ganglionic neurons that innervate the sweat glands
- all parasympathetic post ganglionic neurons
Cholinergic neurons have two different receptors….
- nicotinic
2. muscarinic
Nicotinic receptors are found where? What happens when these receptors are activated by Ach?
Are found:
- in dendrites and cell bodies of sympathetic and parasympathetic post-ganglionic neurons
- in chromatin cells of the adrenal medulla
- at the motor end plate of the NMJ
When activated by ACh
- causes DEPOLARIZATION i.e. excitations of post synaptic cell (post ganglion neuron, autonomic effect and skeletal muscle)
ARE NAMES NICOTONIC because nicotine mimics the action of ACH by binding to these receptors
Muscarinic receptors are found where? What happens when these receptors are activated by Ach?
are found:
- in membranes of effector organs (those innervated by parasympathetic post-ganglionic neurons)
- sweat glands
When activated by Ach
- causes DEPOLARIZATION and HYPERPOLARIZATION»_space; just depends on which cell possesses these receptors…
e.g. GI tract cell > inhibits/relaxes (hyperpolarizes) smooth muscle
Eye cell > excites/contracts (depolarizes) iris
ARE NAMES MUSCARINIC because muscarine mimics the action of ACH by binding to these receptors
Adrenergic Neurons what do they release? WHich neurons in the ANS are adrenergic? What do their receptors do?
NE
- are most sympathetic post ganglionic neurons
There receptors bind NE and EP
(NE is released as either a NT or a hormone, EP is released as a hormone)
Adrenergic neurons have two types of receptors
- Alpha
2. Beta
Alpha & beta receptors
a1 and a2
b1, b2 and b3
Most effectors contain both
- are found on effectors innervated by sympathetic postganglionic neurons
- generally a1 and b1 EXCITED effectors
-generally a2 and b2 INHIBIT effectors
- b3 are present on cells of brown adipose tissue > activation causes thermogenesis (heat)
NE- stimulates more a than b
EP stimulates both equally
Define autonomic tone
= balance between sympathetic and parasympathetic
- regulated by the hypothalamus»_space; turns one up and the other down
Sympathetic system STIMULI
- fear
- exercise
- embarrassment
- emergency
Sympathetic system RESPONSE
- pupil dilation
- increase in HR
- increase in force of contraction of heart
- airway dilation
- constriction of vessels to kidney and GI tract
