Nervous System Flashcards
What is temporal summation?
When excitatory and inhibitory inputs summate with respect to time of arrival at the cell body or dendrite
What is input summation?
When various types of neurones act together to receive most of the impulses converging on the nerve
What are the functions of the axons?
Summate inputs, initiate action potentials, conduct action potentials away from the cell body to terminals, depolarisation of terminals, communication with follower cell
Where do peripheral nerves originate?
Either spinal cord or cranium
Describe sensory neurones
Pseudo-unipolar, transduce energy into electrical impulses, receptor - acts as a transducer between forms of energy.
What direction do sensory neurones relay electrical impulses?
Cell body - spinal cord - brain (Afferent)
Describe interneurones
Multi-polar, smallest neurones, within brain or spinal cord, relay information between sensory and motor neurones, most complex neurones in the nervous system
What are the characteristics of the membranes of neurones?
Bi-lipid - selectively permeable. Ionic concentration gradient - electrochemical gradient therefore neurones are electrically charged
What is the function of astrocytes?
Transfer of nutrients and waste products between neurones and blood, BBB, phagocytic. Offer physical support.
Describe motor neurones
Multipolar, largest neurones in the NS
What direction do motor neurones relay electrical impulses?
Brain - muscles (Efferents)
What are the functions of neuroglia?
Support neurones in CNS/PNS and insulate neurones in CNS/PNS
What are oligodendrocytes?
Neuroglia which provide myelination
What do ependyma cells do?
Line ventricles and central canal of spinal cord for circulation of CSF
What do microglia do?
Provide immunity and phagocytic effects at sites of damage in neurones
What do schwann cells do?
Main function is insulation of peripheral nerve axons thereefore speeding up the conduction of action potentials
What do satellite cells do?
Physical support of neurones in peripheral nervous system
What are the results of an over active parasympathetic nervous system?
Dilated blood vessels, infections, less substrate available for the brain
What are the results of an over active sympathetic nervous system?
Constriction of blood vessels, shortage of supply to tissues which can results in gangrenous peripheries
Describe the structure of the neurones in the parasympathetic nervous system
Messages from brain and spinal cord, cranial - sacral division, pre-ganglion is long and cholingeric. Post-ganglion express nicotinic receptors and are cholingeric.
Describe the structure of neurones in the sympathetic nervous system
Pre-ganglionic are cholingeric, post-ganglionic are noradrenegenic. Pre-ganglions express nicotinic receptors. Some synapses are cholingeric - sweat and ejaculation pathways
What outflow does the sympathetic nervous system have?
Thoraco-lumbar outflow.
What outflow does the parasympathetic nervous system have?
Cranio-sacral
Which part of adrenal gland is under nervous control?
Medulla
Describe somatic efferents
Simplest, efferent neurone terminates directly on effector organ - active to carry out a specific task, inactive the rest of the time, inactive during REM. Fully developed by puberty.
What are the functions of the autonomic nervous system?
Life functions: homeostasis, active along with organogenesis, changing continuous output between two ‘opposing’ systems. Intermittent - promotes excretory mechanisms of the body
Describe the structure of a peripheral nerve
Single cell axon - endoneureum
Nerve fascicle - perineureum
Entire nerve - endoneureum
What do excitatory neurones release?
Glutamate/aspartate neurotransmitters
What do inhibitory neurones release?
Glycine/GABA neurotransmitter
Where would you find myelinated neurones?
Both the autonomic (CNS) and somatic nervous systems
Where would you find unmyelinated neurones?
The autonomic nervous system (Parasymp)
Explain the function of the nodes of Ranvier
Allow for saltatory conduction thus making conduction faster.
Where is white matter found in a nerve?
Peripherally
Where is grey matter found in a nerve?
Peripherally in the shape of a butterfly or figure of H
Where are astrocytes found?
Central NS
Where are oligodendrocytes found?
Central NS
Where are microglia found?
Both the central and peripheral nervous systems
Where are Schwann cells found?
PNS
