W6 Somatic nervous system and skeletal muscular contraction Flashcards
What is the Somatic nervous system?
- Part of the peripheral nervous system
- Controls movement of skeletal muscles (voluntary muscles)
What are Ascending tracts?
They relay information from the spinal cord to the sensory cortex
What are Descending tracts?
They relay information from the motor cortex to the spinal cord
What do Sensory neurones detect?
Where do they relay info to?
Where do they enter the spine?
Where is their cell body located?
- Sense touch, stretch, pain etc.
- Relay information to spinal cord and brain via ascending tracts to the somatosensory cortex (reflex arc)
- Enter spine at the dorsal horn, via dorsal root
- Unipolar neurones – cell body is at dorsal root ganglion
- Myelinated
What are the function of Motor Neurones in the somatic NS?
How do they exit the spine?
Features?
- Relay nerve impulses from the spine to trigger contraction of skeletal muscle
- Exit spine via ventral root
- ONE Alpha motor neurone in somatic NS
- Multipolar and myelinated
What is an alpha motor neurone?
-Neurone that extends from the spinal cord all the way to the muscle (only ONE in somatic NS)
-It is myelinated
Differences between SNS and ANS
SNS has one neurone which stretches from spinal cord to muscle and is myelinated (alpha)
Whereas ANS has 2 neurones and are non-myelinated
Neuromuscular Junction
What is the neurotransmitter here and what does it bind to?
- Synapse where somatic motor neurone and a muscle fibre meet (NMJ)
- Nerve impulse communicates with muscle
- Acetylcholine is the neurotransmitter at skeletal muscle NMJs
- Binds to and activates Nicotinic Acetylcholine Receptor
Which is ionotropic (ligand-gated channel) - Post synaptic membrane termed Motor End Plate (MEP)
Structure of a NMJ in SNS
Pre synaptic cell= Alpha motor neurone
Synaptic cleft
Post-synaptic membrane= Motor End Plate (MEP) where cholinergic receptors found called NiAch Receptors
Post-synaptic cell= Muscle
Schwann cell surrounds synapse
What is always the neurotransmitter at a neuromuscular junction
Acetycholine (Ach)
What does a Schwann cell do?
Generate myelin
What is the Motor end plate?
Where cholinergic receptors are found (on the post-synaptic membrane at a NMJ)
e.g. Nicotinic Ach Receptors
Ach Binds to and activates Nicotinic Acetylcholine Receptors, what happens next?
When Ach binds to them, they will open and allow (sodium) ions to flow into the post-synaptic membrane
What is Skeletal muscle? (striated) (3)
- Part of the SNS
- Enables movement of limbs and other parts of the skeleton
- Connected to bone via tendons (origin) or via tendons (insertion)
-Stripy
Contain myofibrils, sarcolemma, sarcoplasm, T-Tubule etc
What is the structute of a muscle fibre? (5)
Myofibril:
Sarcolemma
T-tubule
Sarcoplasmic reticulum
