Somatic nervous system skeletal and muscular contaction Flashcards
what doses peripheral nervous system control?
Controls movement of skeletal muscles
- Voluntary movement
Ascending tracts
relay information from the spinal cord to the somatosensory cortex
Descending tracts
relay information from the motor cortex to the spinal cord
Sensory neurone
- Sense touch, stretch, pain etc.
- Relay information to spinal cord and brain
- Enter spine at the dorsal horn, via dorsal root
- Unipolar neurones – cell body is at dorsal root ganglion
- Myelinated - speed action potential
Motor Neurones
- Relay nerve impulses from the spine to trigger
- Contraction of skeletal muscle
- Exit spine via ventral root
- ONE Alpha motor neurone
- Multipolar and myelinated
Neuromuscular junction
- Acetylcholine is the neurotransmitter at skeletal muscle NMJs
- Shwann cell surrounds the presynaptic cleft ensure transmission
- Binds to and activates Nicotinic Acetylcholine receptor which is Ionotropic ligand gated reponds quick
- Post synaptic membrane termed Motor End Plate (MEP)
skeletal striated
- Enables movement of limbs and other parts of the skeleton
- Connected to bone
- via tendons (origin)
- via tendons (insertion)
Cardiac striated
- The pump in the circulation (heart)
- Functional syncytium
- Intrinsic pacemaker activity
Smooth muscle
- Functional syncytium
Around many hollow internal organs
Structure of muscle fibre
- Muscle belly
- Fasciculus
- Sarcolemma
- Sarcoplasm & sarcoplasmic reticulum
- Myofibrils
Protiens involved in contraction
- Myosin
- Actin
- Troponin
- Tropomyosin
I band
- Contains only actin filiments
A I zone
- Consists of both the A and the I band
H zone
Just contains the mysoin filiments
Z discs
- At the terminal ends of the sarcomere
- 1 sarcomere holds the actin filiments
Cross bridge cycling
- ATP binds to myosin
Myosin releases actin - Myosin hydrolyzes ATP and energy from ATP rotates the myosin head to the cocked position. Myosin binds weakly to actin.
- Power stroke begins when tropomyosin moves off the binding site. Ca2+ binds to troponin
- Myosin releases ADP at the end of the power stroke.
- ADP released - the myosin head tightly bound to actin, cycle is ready to begin once
more as a new ATP binds to myosin.
Excitation-Contraction- Coupling
- Need ATP & Calcium
- Triggers calcium release action potential
Contration and sliding filiment theory
- Sliding of myosin over actin filements and the H-zone disappers
Events at NMJ
- Action potential acytyl choline relase bind receptor
- cause muscle end plate potential
- muscle action potential
- T-tubules deploarise open Ca2+ channel of sarcoplasmic reticulum
- Sarcoplasmic Ca2+ increases
- muscle fibre contracts
- Ca2+ pumped back into SR
- Muscle fibre relaxes
acetylcholinergic movement in the presynaptic cleft
- ACh formed in the synaptic terminal
- Generated by ChAT
- Packaged into vesicles
- Calcium entry causes fusion of synaptic vesicles
- Released into the synaptic cleft
- some nicotinic ACh receptors
- Broken down by Ach- esterase
- Choline taken up reusing
pharmacological
interference
- Prevent packaging to synaptic vesicles and the transporting
Botox and vescular release
- Botulinum toxin from clostridium botulinum bacteria
Inihibitor of vesicular fusion: - Alters proteins required for vesicular fusion with the presynaptic membrane
Medical uses of botox
Severe muscular spasms - Blepharospasm
Children with cerebral palsy, motor neuron disease
Speech deficits following throat cancer
