Nervous System: Divisions, Function + Muscle Contraction (w4) Flashcards
What does the somatic nervous system control ?
It controls the movement of skeletal muscles.
What two divisions are in the autonomic nervous system ?
- parasympathetic division
-sympathetic division
What are the two control centres is the brain (cortex) ?
- Somatosensory cortex
- Motor cortex
What do ascending tracts do ?
They relay information from the spinal cord to the sensory cortex.
What do descending tracts do ?
They relay information from the motor cortex to the spinal cord.
What are sensory neurones, and what do they do ?
They are myelinated neurones which relay information to the spinal cord and the brain.
They sense touch, stretch and pain.
What are motor neurones and what do they do ?
They are multipolar and myelinated neurones which relay nerve impulses from the spine to trigger contraction of the skeletal muscle.
What is a unipolar neurone ?
A neurone which has a cell body at dorsal root ganglion.
For example; Sensory neurone
What makes up a neuromuscular junction (NMJ) ?
A synapse somatic motor neurone and a muscle fibre.
What neurotransmitter is at the skeletal muscle neuromuscular junctions ?
Acetylcholine
What is the motor end plate (MEP) and what do you find here ?
The MEP is the post synaptic membrane and you find the chollinergic receptors.
Describe the function of skeletal (striated) muscle and how it is connected to bones ?
- It enables the movement of limbs and other parts of the skeleton and is connected to bone via tendons (origin) or via tendons (insertion).
Describe the function of cardiac (striated) muscle ?
Cardiac muscle is the pump in the circulation system (heart). It has intrinsic pacemaker activity and is myotonic.
Where is smooth muscle found ?
Around many hollow internal organs.
What is the cytoplasm of a muscle fibre called ?
Sarcoplasm
List the 4 key proteins involved in contraction;
- Myosin
- Actin
- Troponin
- Tropomyosin
What makes up a single thick filament ?
Many myosin molecules
Which is the thick filament and which is the thin filament ?
Thick filament = myosin
Think filament = actin
What is the A band ?
The length of the myosin filament.
Describe the 4 main steps to the cross bridge cycle;
1) ATP binds to Myosin causing it to release the actin.
2) Myosin the hydrolyses ATP. This energy released from the ATP rotates the myosin head to the cocked position where it weakly binds to the actin.
3) The power stroke then begins when the tropomyosin moves off the binding site.
4) Myosin then releases ADP at the end of the power stroke.
-ADP released = the myosin head is tightly bound to the actin (rigor state) the cycle is ready to begin once more as a new ATP molecule binds to myosin.
What does it mean when tight binding is in rigor state ?
It’s when there is tight binding between the myosin head and the actin.
What does an action potential trigger the release of ?
Calcium ions
What are the 4 main events which occur at the neuromuscular junction ?
1) resting state
2) AP ( action potential ) arrival - cause release of Ach and depolarisation of pre-synapse.
3) Depolarisation of MEP -wave of depolarisation passes down the fibre causing the pre-synapse to re-polarised.
4) Contraction of muscle - MEP repolarises and muscle fibre depolarises (contraction)
Muscle fibre then repolarises and process repeats.
Which portion of the nervous system is considered involuntary ?
Autonomic nervous system
