Nervous Sytem 2 - PNS Flashcards
What 2 neurons make up the PNS ?
- afferent/sensory neurons = signals from the periphery to CNS
- efferent/motor neurons =CNS to the muscles/skin
What is the somatic nervous system ?
- mainly controls voluntary movement
- specifically refers to spinal nerves which control skeletal muscles
What do visceral sensory neurons monitor?
- Temperature, pain, irritation, chemical changes, and stretch in the visceral organs
How does the brain interpret signals from visceral sensory neurons?
- as hunger, fullness, pain, nausea, or well-being.
How are receptors spread in visceral sensory neurons ?
- receptors widely scattered
What do visceral sensory fibres conduct ?
- conduct sensory impulses from internal organs, glands, and blood vessels to CNS
What is a visceral reflex ?
- the reflex arc of the autonomic nervous system, produces a glandular or non-skeletal muscular response in internal organs (heart, GI tract organs)
What are the 2 types of visceral reflexes and what are the differences ?
- spinal reflexes - e.g. defecation + micturition reflexes
- peripheral neurons - only involves peripheral not spinal cord e.g. enteric nervous system = 3 neuron reflex arc within gut wall - called second brain
What is the function of the autonomic nervous system ?
- maintains internal environment
- mostly involuntary
- controls visceral functions (digestion, excretion, circulation)
- modulates endocrine function
What is the ANS input ?
- sensory neurones from peripheral organs send signal to hypothalamus + medulla
What are the 2 divisions of the ANS output ?
- sympathetic or parasympathetic neurons
- have opposing actions
What do ANS nerves control ?
- smooth muscle ( bronchioles , digestive system)
- cardiac muscle ( control heart rate + contractile force)
- secretory glands (adrenal medulla + salivary + sweat glands )
What is the function of the sympathetic nervous system ?
- fight or flight
- short term survival
- increases energy availability
- increase heart rate
- increase lung capacity
- increase blood flow to muscles
- increase blood glucose
What is the function of the parasympathetic nervous system ?
- rest + digest
- long term survival
- reduces energy availability
- Decrease heart rate
– Decrease lung capacity
– Increase blood flow to digestive system
– Increase fat/glycogen stores
What are the 3 differences between parasympathetic and sympathetic nervous systems ?
- where the nerves originate = sympathetic in thoracolumbarvs parasympathetic in craniosacral
- differences in neurotransmitters + receptor sub types
- sympathetic releases noradrenaline (excitatory) vs parasympathetic releases acetylcholine (inhibitory)
- location of ganglia (where 1st neuron meets the 2nd neuron )
- parasympathetic = ganglia closer to target organ vs sympathetic closer to spinal cord
What are the structural differences between motor neurons and ANS neurons ?
- motor has only 1 neurone (allows for faster response as ganglia slows down response)
- ANS has 2 neurons
- preganglionic neurone = from spinal cord to ganglia
- postganglionic neurone = from ganglia to target/effector
What are the functional differences between motor and ANS neurons ?
- motor = part of somatic NS - controls voluntary movement
- releases Ach causes contraction of skeletal muscles
- ANS = preganglionic release Ach in both parasympathetic and sympathetic closer
- whereas postganglionic = parasympathetic releases Ach and sympathetic release noradrenaline
What neurotransmitters and involved in the sympathetic system, involving the adrenal pathway ?
- pre-ganglionic releases Ach
- post-ganglionic releases noradrenaline
Adrenal pathway : - only has 1 neuron which is preganglionic = always releases Ach
- release of Ach causes adrenal medulla to release hormone adrenaline
What neurotransmitters are involved in the parasympathetic system ?
- pre-ganglionic releases Ach onto nicotinic Ach receptors on ganglion
- this activates post-ganglionic neuron
- post-ganglionic releases Ach onto musacrinic Ach receptors on target organ
What are the key features + locations of nicotinic acetylcholine receptors ?
- 5 subunits
- 2 Ach binding sites
- located in skeletal muscle + ganglia + adrenal medulla
- no second messenger
- rapid response
What are the key features of muscarinic receptors ?
- 7-TM GPCR
- 3 subtypes
- M1- brain + parietal cells (excitatory)
- M2- heart (inhibitory)
- M3 - smooth muscle / glands (excitatory)
- 1 and 3 coupled to Gq protein (PLC—> IP3+ DAG increased levels of ca2+)
- M2 coupled up to Gi protein
- uses 2nd messenger / GPCR
Effects of the fight or flight response - sympathetic on body ?
• Pupil dilation
• Increased heart rate
• Bronchodilation
• Decreased salivation
• Decreased digestion
• Decreased urination
• Decreased defecation
• Vasoconstriction near non-essential organs
• Vasodilation near muscles
• Inhibition of insulin secretion
• Glycogenolysis
Which neurons are adrenergic vs cholinergic in the sympathetic nervous system ?
- preganglionic = cholinergic (release Ach)
- postganglionic = adrenergic (release ND/NE)
Effects of rest + digest - parasympathetic on body?
- Pupil constriction
• Decreased heart rate
• Bronchoconstriction
• Increased salivation
• Increased digestion
• Increased urination
• Increased defecation
• Stimulation of insulin
secretion
Are the neurons in the parasympathetic nervous system adrenergic or cholinergic ?
- both cholinergic
What are the key features of adrenoreceptors ?
- G-protein coupled (metabotropic)
- alpha (α) and beta (β)
• Respond to adrenaline, nor-
adenaline
• Adrenaline: Diverse actions
depending on target
• Depending on the downstream
molecules that they activate
What are the 5 main types of adrenergic receptors and what proteins are they coupled up to ?
- α1 - coupled to Gq = activates PLC cleaves PiP2 into IP3 + DAG - inc Ca2+ conc
- α2 - coupled to Gi = inhibits adenyl cyclase = reduces cAMP
- β1, β2 , β3 coupled to Gs = activates adenyl cyclase = increases cAMP
What are the functions of the 5 types of adrenergic receptors?
- α1 - Stimulates smooth muscle contraction in blood vessels = increase blood pressure
- α2: Inhibits NE release
- β1: Increases heart rate and contractility
- β2: Relaxes smooth muscle (e.g., bronchodilation, vasodilation).
- β3: Stimulates lipolysis (found in adipose tissue).
