Wk 4: Nervous System Flashcards
The central nervous system includes:
the brain and spinal cord
The peripheral nervous system includes:
nerves (cranial + spinal) and autonomic ganglia
What does the central nervous system do?
The control uni, performing integration and analysis of info and then signal/command as a response
What does the Peripheral nervous system do?
Relays information from internal environement and external environment to CNS then includes efferent responses from brain to target cells/organs
What are the 2 categories of the autonomic nervous system?
- Parasympathetic
- Sympathetic
Neurons
Excitable cells able to transmit nervous message-function will vary according to the type of neurons
Sensory neurons
Pseudo-unipolar, bipolar
transmit impulses towards CNS for processing
Interneurons
multipolar
Lie between motor & sensory neurons and shuttle signals through CNS pathways (99% of body’s neurons)
Motor neurons
Multipolar
carry impulses from CNS to effectors for action
Afferent nerves
sensory neurons (sensory organs i.e skin-part of the CNS)
Efferent nerves
motor neurons (control muscles i.e contraction muscles-part of the PNS)
Neuroglia
Specialised cells found only in close association with neurons, don’t participate directly in info transfer-there are 4 types of neuroglia
Oligodendrocytes (CNS)
make myelin on many axons (1 olgio=60 axons)
Astrocytes role and function (CNS)
Most abundant type of glia in CNS.
roles are:
1. structural support
2. provides nutrients/neuron homeostasis
3. maintains/regulates synaptic connections
4. reacts to injuries (astrogliosis)
Microglia (CNS)
resident macrophages in brain-“brain immune system”
Increase in phagocytosis after injury causes cells to move to injured area
Ependymal cells (CNS)
provide lining in ventricles (involved in cerebro spinal fluid production)
Shwann Cells
Similar function to oligodentroncytes, but divide more myelinate faster and are more resistant to injury
Satellie cells
similar function to astrocytes, meaning they support neurons and enhance their function
What are action potentials?
electrical signals that propagate along axons, through rapid, transient depolarisation of the cell membrane
What happens in action potential when the neuron is activiated?
When there is a change in the resting membrane potential (RMP) that reaches a certain threshold (-55mV), an action potential will be induced
What happens in depolarisation?
The voltage gated Na+ channels in the neuronal membrane open and sodium flows INTO the cells, bringing +ve electrical charge, increasing membrane potential
What happens in repolarisation?
When the membrane reaches a certain potential of approx 30-40mV, the voltage gated K+ channels open, leading to the exit of potassium ions out of the cell
What happens in hyperpolarisation?
K+ ions continue to leave the neuron, as the voltage gated k+ channels tkae time to close, which causes the membrane potential to drop below the RMP (-70mV), until it reaches around -90mV.
What are the 2 methods of propagating action potentials?
- Continuous propagation (unmyelinated axons)
- Saltatory propagation (myelinated neurons)