L20, 21 & 22: Organisation of the nervous system Flashcards
What are the two components of the central nervous system?
Brain and spinal cord
What are the to neuron types that make up the peripheral nervous system?
Motor neurons and sensory neurons
Which part of the nervous system controls voluntary movements?
Somatic
Which part of the nervous system controls involuntary responses?
Autonomic nervous system
Which division of the autonomic nervous system controls “rest and digest” functions?
Parasympathetic
Which division of the autonomic nervous system controls “fight or flight” functions?
Sympathetic
What areas are innervated by cervical nerves (C1-C8)?
Head, neck, upper limb, diaphragm
What areas are innervated by thoracic nerves (T1-T12)?
Chest muscles and abdominal muscles
What areas are innervated by lumbar nerves (L1-L5)?
Leg muscles
What areas are innervated by sacral nerves (S1-S5)?
Bowel, bladder, sexual function
What is cranial nerve (I)? What does it innervate?
(I) Olfactory
Sensory: Nose
What is cranial nerve (II)? What does it innervate?
(II) Optic
Sensory: Eye
What is cranial nerve (III)? What does it innervate?
(III) Occulomotor
Motor: Most eye muscles
What is cranial nerve (IV)? What does it innervate?
(IV) Trochlear
Motor: Superior oblique muscle
What is cranial nerve (V)? What does it innervate?
(V) Trigeminal
Sensory: Face, teeth, sinuses, etc.
Motor: Muscles of mastication
What is cranial nerve (VI)? What does it innervate?
(VI) Abducent
Motor: External muscle
What is cranial nerve (VII)? What does it innervate?
(VII) Facial
Motor: Muscles of the face
What is cranial nerve (VIII)? What does it innervate?
(VIII) Vestibulocochlear
Sensory: Inner ear
What is cranial nerve (IX)? What does it innervate?
(IX) Glossopharyngeal
Motor: Pharyngeal musculature
Sensory: Posterior part of tongue, tonsil, pharynx
What is cranial nerve (X)? What does it innervate?
(X) Vagus
Motor: Heart, lungs, bronchi, GI tract
What is cranial nerve (XI)? What does it innervate?
(XI) Accessory
Motor: Sterno-cleidomastoid and trapezius muscles
What is cranial nerve (XII)? What does it innervate?
(XII) Hypoglossal
Motor: Muscles of the tongue
Fill in the gap:
Somatic (voluntary) efferent nerves carry impulses from CNS to __1__ only.
skeletal muscles
True or false:
There is a third division of the peripheral nervous system (in addition to SNS and ANS) called the enteric nervous system.
True
Which of the following is/are true of somatic motor neurons?
A. Effector is striated muscle
B. Usually 2 neurons with synapse (ganglion) between
C. Neurotransmitter is always stimulatory
D. Ach and noradrenaline released at synapses
E. No firing at rest
F. Effector at rest is flaccid
A. Effector is striated muscle
C. Neurotransmitter is always stimulatory
E. No firing at rest
F. Effector at rest is flaccid
(B is incorrect because somatic motor pathways use a single motor neuron from spinal cord to target organ; D is incorrect because somatic motor neurons only use Ach)
How many neurons are involved in an autonomic motor pathway?
Usually 2 neurons with a synapse (ganglion) between
Are neurotransmitters on an autonomic motor pathway stimulatory or inhibitory? Is this the same for somatic?
Autonomic: NTs can be stimulatory or inhibitory (NT’s will be either ACh or noradrenaline)
Somatic: NT’s always stimulatory (and always ACh)
Which motor pathway has baseline firing?
Autonomic.
While the somatic has no firing at rest, the autonomic has baseline firing which speeds up when stimulated.
If an effector has an intrinsic resting tone, which motor pathway is it on?
Autonomic
What are the names of the two motor neurons used in ANS pathways?
Preganglionic and postganglionic
Where is the cell body and axon of a preganglionic ANS motor neuron located?
Cell body (soma) is in the brain or the spinal cord (lateral horns). The axon exits the CNS as part of a cranial or spinal nerve (small diameter type B fibre)
Where does a preganglionic ANS motor neurone synapse?
It synapses with a postganglionic neuron at the autonomic ganglion
Where is the cell body and axon of a postganglionic ANS motor neuron located?
Whole neuron lies outside the CNS. Cell body is in the autonomic ganglion, axon leaves as a type C fibre, relaying information to visceral effectors
Where in the spinal cord would you find preganglionic cell bodies?
Lateral horns of grey matter in the thoracolumbar division (12 thoracic segments and first 3 lumbar segments)
In the sympathetic division of the ANS, what are the types of ganglia (synapse regions)?
Two types: Sympathetic trunk ganglia (innervate above the diaphragm) and prevertebral ganglia (innervate below the diaphragm)
In the sympathetic division, preganglionic nerves can synapse with how many postganglionic neurones?
20+ (divergence, many sympathetic responses are whole body)
In the parasympathetic division of the ANS, what are the types of ganglia (synapse regions)?
Just 1 type: Terminal ganglia (close to effector)
In the parasympathetic division, preganglionic nerves can synapse with how many postganglionic neurones?
Only synapse with 4-5 postganglionic neurons, all in the same visceral organ
In the parasympathetic division, where do preganglionic neurons originate?
Cell bodies in nuclei of 4 cranial nerves: III (oculomotor), VII (facial motor), IX (glossopharyngeal), X (valgus).
And S2, S3, S4
Why is the parasympathetic division very targeted and not controlled by hormones?
You don’t want to start switching off organ systems in mass!
Which ANS division’s preganglionic neurons originate from T1-L2?
Sympathetic
Which ANS division’s preganglionic neurons originate from cranial nerves III, VII, IX, X and spinal cord segments S2-S4?
Parasympathetic
Which ANS division is associated with sympathetic root ganglia and prevertebral ganglia?
Sympathetic
Which ANS division is associated with terminal ganglia?
Parasympathetic
Which ANS division is associated with ganglia that are close to the CNS and distant from visceral effectors?
Sympathetic (sympathetic trunk ganglia and prevertebral ganglia)
Which ANS division is associated with ganglia that are typically near or within wall of visceral effectors?
Parasympathetic (terminal ganglia)
Which ANS division is associated with short preganglionic neuron axons, and long postganglionic neuron axons?
Sympathetic
Which ANS division is associated with long preganglionic axons and short postganglionic axons?
Parasympathetic
Which ANS division is associated with the presence of rami communicantes?
Sympathetic
Which ANS division is associated with the absence of rami communicantes?
Parasympathetic
Which ANS division is associated with the neurotransmitter acetylcholine?
Both sympathetic and parasympathetic
Which ANS division is associated with the neurotransmitter noradrenaline?
Sympathetic
Describe the locations of the sympathetic trunk ganglia, prevertebral ganglia and terminal ganglia. Which type of autonomic neurones synapse in each type of ganglion?
Terminal ganglia (parasymp.) are locate near or within their visceral effector. Sympathetic trunk ganglia (symp.) are above the diaphragm. Prevertebral (symp.)are below the diaphragm.
Which neurotransmitter would be used by a postganglionic neuron that was stimulating cardiac muscle?
Noradrenaline
True or false: A single preganglionic neuron can cause sympathetic innervation of the adrenal medulla
True
What neurotransmitter is used by postganglionic neurons in the somatic system?
Trick question! Somatic system only uses one neuron, so there isn’t a postganglionic neuron. The somatic neuron use ACh with a nicotinic receptor on the effector.
What is the neurotransmitter and receptor used in the ganglia of the autonomic systems?
Sympathetic: ACh, nicotinic receptor
Parasympathetic: ACh, nicotinic receptor
In each ANS division, what is the neurotransmitter and receptor used by postganglionic neurons and their effectors?
Sympathetic: Ach for sweat gland innervation; NA for all others (adrenergic receptor).
Parasympathetic: ACh only, with a muscarinic receptor
Which receptor is found on all postganglionic cell bodies and the adrenal medulla?
Nicotinic
Which receptor is found on all effectors of parasympathetic and sweat glands of sympathetic?
Muscarinic