Why is the nervous system important
- Wired communication
- Short term regulation
Nervous system definition
The nervous system is a complex network of nerve cells and fibres which transmit nerve impulses between parts of the body
What are the 2 parts of the nervous system
- Central nervous system
- Autonomic nervous system
What are the main functions of the nervous system (3)
- To sense changes internal and external to the body
- To process this sensory information
- To initiate a response
What are the 2 main cell types of. the nervous systems
- Neurons (nerve cell)
- Glial cells
Glial cells
- 90% nervous system cells
- Support neurons
- Various types of support
What are the 2 parts of the peripheral nervous system
- Somatic nervous system
- Autonomic nervous system
Somatic nervous system
- Voluntary nervous system
- Provides information from the periphery to the CNS along afferent sensory nerves, and responses travel directly to skeletal muscles along effector motor nerves
Autonomic nervous system
- Involuntary nervous system
- Containing sensory and motor components, the ANS sends information from the CNS to smooth muscles, cardiac muscles and glands a 2 neuron efferent pathway
2 functional subdivisions of PNS
- Sensory or effernet are nerves carrying information towards the CNS
- Motor or efferent division are nerves carrying information away from the CNS to skeletal muscle fibres
Physiological structures of the motor and sensory communication at the spinal cord
- Dorsal ganglion
- Ventral horn
- Cell body of sensory neurone
- Cell body of motor neurone
Functions of the Motor and sensory communication at the spinal cord
- To skeletal muscle
- To brain
- Sensory information
Resting membrane potential
Sodium potassium pump
Action potential definition
Is a rapid and substantial depolarisation of the neurone’s membrane
Values of action potential
Lasting typically 1ms, the potential changes from the RMP of about –70mV to a value of about +30mV and the rapidly returns to its resting value
How does depolarisation and repolarisation occur (5 steps)
- Resting membrane potential, maintained by sodium-potassium pumps
- Depolarisation - Na+ channels open and Na+ moves into the cell, depolarising it
- Repolarisation - K+ moves out of the cell
- Hyperpolarisation - Additional K+ moves out of the cell, hyperpolarising it
- Cells return to resting membrane potential
Depolarisation theshold
- To achieve an action potential the membrane voltage must be greater than the depolarisation threshold
- Any depolarisation below this threshold will not result in an action potential (graded potential)
2 types of Refractory period
- Absolute refractory period
- Relative refractory period
Absolute refractory period
When a segment of an axon’s sodium gates is open and in the process of generating an action potential, it is unable to respond to another stimulus
Relative refractory period
Sodium gates are closed; potassium gates are open; causes repolarisation
Myelination
The axons of many neurones, particularly large neurones, are myelinated, meaning they’re covered with a sheath formed by myelin
Myelin
Is a fatty substance that insulates the cell membrane
Nodes of ranvier
Are gaps between each myelin sheath which leave the axon uninsulated
