Week 5 - nervous system (ANS) (somatic system) Flashcards
What is the autonomic nervous system
Regulates body when not paying attention to it
Overview of NS
- CNS: brain and spinal cord (surrounded by dura), memory cognition, emotion
- PNS: everything outside CNS, afferent/efferent: afferent division is sensory/ visceral stimuli; efferent divides into somatic (running skeletal muscles); autonomic (divides into sympathetic and parasympathetic effecting smooth muscle/cardiac muscle/oxocrine/some endocrine)
Sympathetic
Fight or light
Parasympathetic
Rest and digest
What does the ANS regulate
Activity of Organs - eg. Heart beat faster/slower
Maintian hormeostasis
Regulates activity of glands
What is the ANS a part of?
PNS
How can the ANS operate?
Atuonomically eg. Reflex and central contorl, or stimulate it using a conscious mind (eg. Bringing heart rate down by thinking about it)
What does the sympathetic division control?
- dilates pupil
- inhibits salvation
- accelerates heart
- fascilitates breathing
- inhibits digestion
- stimulates release of glucose
- secretes eponephrine
- relaxes bladder
- inhibits sex organ
What nerves does the sympathetic nerves activate?
Cervical nerves and thoraxic and lumbar nerves
Where do nerves from parasympathetic divsion reach?
Cranial nerves
Sacral nerves
Why does the heart sitll beat if you are paralised from head downwards eg. When breaking neck
Myogenic - tend to have lower heart rate as sympathetic division is no longer engaged
What funcitons can the parasympatehtic impact?
- constrict pupil
- stimulates salvation
- slows heart
- constricts breathing
- stimulates digestion
- stimulates gallbladder
- contracts bladder
- stimulates sex organs
How is the neuron structures in the ANS
Preganglionic neurons (from CNS)
Autonomic ganglion
Postganglionic neurons
Whatr is a autonomic ganglion?
Cluster of neurons
Are preganglionic fibres myelinated?
Yes
Are postganglionic fibres myelinated?
No
Where are sympathetic ganglia usually located?
Close to the CNS
Where are parasympatehtic ganglia usually located to?
Closer to target organ, if not embedded in it
Is there a 1:1 ratio of pre to post ganglionic fibres?
No
How many cellbodies in the ganglia + postganglionic fibres do sympathetic preganglionic axons tent to innervate?
More than 20 cell bodies in the ganglia
Many postganglionic fibres
How many cell bodies in ganglia + postganglionic fibres are innervated by parasympathetic axons?
Smaller extent
- less than 4 cell bodies/ axon
Does sympathetic divisions speeding everything up?
No - does prepare bdy for flight/ flight and shuts of other divisions which are no longer necessary for survival
What are paravertebral ganglia?
Sympathetic ganglia tend to align in a row on each side of the spinal cord
What are prevertebral ganglia?
Located further away from spinal cord.
what is confusing about prevertebral ganglia
- its further away rom the spinal cord
- Transmits efferent information
What do ganglions do?
- amplify
- give complexity and order
- allow us to interfere, consciously think about it
What neurotransmitter is used for pregangionic neurons of BOTH divisions?
Acetylcholine (ACh)
What is the neurotransmitter used for postganglionic neurons of BOTH divisions?
Sympathetic: norepinephrine
paraympathetic:
Acetylcholine
Descirbe a ACh synapse of a cholinergic receptor
- ACh made form choline and acetly CoA
(Transported in vesicles) - In the synaptoc cleft ACh is rapidly broken down by enymes ACETYLCHOLINESTERASE
- Choline is transported back inot axon terminal and is used to make more ACh
name the two types od cholinergic receptors
Nicotinic
muscarinic
What are nicotinic receptors?
ACh or nicotine binds, they open to allow positive ions to flow (usually Na+ and K+)
-> ionotropic effect: channel alters directly when ligand binds to alter permeability of channel
What causes a nicotinic receptor?
often causes fast synaptic transmission and is stimulatory
What are muscarinic ACh receptors?
When ACh or muscarine binds, they release G porteins, which bebing a cascade of information
-> metabotropic effect: channel altered indirectly when ligand binds to channel
Can muscarinic receptors be stimulatory or inhibitory?
Both
How do adrenoreceptors work?
When epinephrine or norepinephrine binds, they release G proteins, begin a cascade of information
Name the subtypes of adrenoreceptors?
Alpha and beta
Are alpha and beta metabotropic or ionotropic?
Both metabotropic
Sensitivity?
Alpha 1
Alpha 2
Beta 1
Beta 2
NE>E
NE>E
NE=E
E>NE
General recap about receptors and where they are in the way of neurons
Ganglion is always nicotinic, target organ: sympathetic: adrenoreceptors (G protein), Parasympathetic: muscarinic (G-protein)
What is the somatic nervous system?
Drives skeletal muscles
- 2nd branch of efferent besides ANS
Motor control
- starts in CNS (upper motor neuons: motor cortex - planning; down to brianstem centers - coordination of movement)
-splits of into local cricuit neurons, ultimately though motor enuron pools
into skeletal muscle
(PNS too) - with sensory input
Ganglia in CNS is called
Nuclei
Describe the corticospinal tract
Spinal cord has lots of diff types of neurons,
What are upper motor neurons?
Neurons that control muscels and the internourons that affect them
In the somatic nervous system what kind or colinergic receptors in the skeletal muscle receives ACh?
Niconitic - as they include the nueomuscular junctions
How many juncitons are there in LOWER motor neuons reaching skeletal muscles
None - think about giraffe - very long, might be in bundles but continuous
What is a reflex?
Involuntary movements, doesnt go via consciousness
Name the 5 steps of the somatic refelx arc
- Sensory or receptor
- Afferent pathway, to the spinal cord or brainstem
- A integrating centre, the grey matter of spinal cord or brainstem synpase
- Efferent pathway to the muscles
- Effector msucle gives response
Proprioception
- Sense length of muscles and force
patellar reflex
Afferent fibres -> spinal cord -> right back to muscle itself via efferent fibres (monosynaptic reflex) -> squeeze knee
- but antagonist neets to relax, in this case hamstring muscle
What is the patellar reflex an example of?
Negative reflex arc
What is the Jendrassik Manoevre ?
Patient clenches their teeth and tries to pull-a;part their interlocked fingres - occupied enough of CNS that it does not interfere with patellar reglex
What are the two types of proprioception
Muscle spindle and golgi tedon organ
Explain muscel spindle
- sensory neurons fire action potental in muscleʻs relaced state
CONTRACTION get wider- stretches nerve fibres- causing them to fire fewer axon potentials
STRETCH
Loads of action potential, lean muscle
How do spindles work?
- separate motoneurons
- axons interacting with motor neurons
- group of afferent
:. Input going up afferent fibres - processed in spine - reflex arc going out to reflex arc for skeletal muscels - gamma causing intrafusal fibres to react in order for sensory information to br generated - so we know whats going on - FOR LENGTH
How do I know how much force is on something?
Golgi tendon organs
How many fibres are connected to each golgi tendon organ?
Approx 10 - 15
How do golgi tendon organs work?
- semspry dendrites of afferent nerve of the golgi tendon organ are interwoven with collagen fibres - like finger trap
PURPOSE: hearder to split apart tendon
What happens to the golgi tendon organs when the msucle contract?
- collagen fibris are pulled tright, whcih activates the golgi tendon organ afferent nerve
what connection do golgi organs have to its own motor neuon?
- disynaptic
- inter neuron is glycergic inhibitory neuron
What is the funciton of golgi organs?
Protection mechanism against excessive tension in a muscle
- if msucle is subject to tension sufficient to damage, golgi organ porduces a powerful activation of inhibitoy interneuron that stops the lower motor neuron firing
Is it not wasteful to have neurons constantly firing when relaxed?
- Small change in x - stimulus intensity gives a large change in frquency of APs impulses
- if in the middle of the log graph
- but if you overlap wiht multiple receptors, (log graph ) it will be relatively low as its also on less steap areas of 1 and 3 when happening in 2
