Nervous System 2 Flashcards
Describe the somatic nervous system.
- Mainly controls voluntary movement
- Specifically refers to spinal nerves which control skeletal muscles
What do visceral sensory neurones monitor?
Monitor temperature, pain, irritation, chemical changes and stretch in the
visceral organs
State the function of visceral sensory fibres?
Conduct sensory impulses (usually pain or reflex
sensations) from the internal organs, glands, and blood vessels to the
central nervous system
Describe the visceral reflex.
- It is the reflex arc of the autonomic nervous system which produces a glandular or non-skeletal muscular
response in internal organs like the heart, blood vessels, organs in the gastrointestinal tract - Many are spinal reflexes such as defecation and micturition reflexes
- Some only involve peripheral neurones: spinal cord not involved
Describe the functions of the autonomic nervous system.
- Maintains internal environment
- Mostly involuntary
- Controls visceral functions
- circulation
- digestion
- excretion
- Modulates endocrine function
What do ANS nerves control?
Mainly smooth muscle, cardiac muscle and secretory glands.
What are the smooth muscles?
- Bronchioles
- iris
- Digestive system
- Bladder
- Vascular system
What are the secretory glands?
- Adrenal medulla
- Pancreatic islets
- Salivary glands
- Sweat
What is the function of cardiac muscle?
- Control heart rate
- Control contractile force
What is the ANS divided into?
- Sympathetic
- Parasympathetic
Describe the sympathetic division.
- ‘Fight or flight’
- Short term survival
- Generally increases energy availability/
capacity and usage
– Increase heart rate
– Increase lung capacity
– Increase blood flow to muscles
– Increase blood glucose - GI tract relaxation
- Increase adrenaline secretion from adrenal medulla
- Vasoconstriction in skin
- Pupil dilation
- Bronchiolar dilation
Describe the parasympathetic division.
- ‘Rest and digest’
- Long term survival
- Generally reduces energy availability/ capacity and usage
– Decrease heart rate
– Decrease lung capacity
– Increase blood flow to digestive system
– Increase fat/glycogen stores
What are the differences between the parasympathetic division and sympathetic.
- Where nerves originate
(leave CNS) - Differences in
neurotransmitters and
receptor subtypes - Where the ganglia (cell
bodies) are, ie where 2
neurons synapse
Where is the adrenal gland located?
On top of kidneys
Describe the role of the adrenal medulla.
- A major organ of the sympathetic nervous system
- Can cause body-wide release of epinephrine/adrenaline
State the physical changes to the body as a result of the parasympathetic system.
- constriction of pupil
- bronchiolar constriction
- increased GI motility + secretion
- inhibitory effects on heart
What are the two acetylcholine receptors?
- Nicotinic
- Muscarinic
Which receptors mediate the actions of acetylcholine in the ANS?
- Nicotinic receptor
- M1 muscarinic couples to Gq
- M2 muscarinic couples to Gi
- M3 muscarinic coupled to Gq
Describe nicotinic receptor.
- Ligand-gated ion channel
- Rapid, short-lived postsynaptic response
- Main receptor on postganglionic ANS neurons
Describe M1 muscarinic coupled to Gq.
- Expressed by smooth muscles and glands of the gut
- Smooth muscle contraction, glandular secretion
Describe M2 muscarinic coupled to Gi
- Expressed by cardiac muscle of cardiovascular system
- Reduction in heart rate Ach release inhibition
Describe M3 muscarinic coupled to Gq
- Expressed by smooth muscle and glands of many parasympathetic targets
- Smooth muscle contraction, glandular secretion
Describe adrenoreceptors.
- G-protein coupled (metabotropic)
- 2 types: 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 five main adrenergic receptor types?
- alpha 1 coupled to Gq
- alpha 2 coupled to Gi
- Beta1 1 coupled to Gs
- beta 2 coupled to Gs
- beta 3 coupled to Gs
