Basic Plan of the Nervous System Flashcards
(25 cards)
What are the main functions of the NS?
sensory input
integration
motor output
How is the NS structured?
CNS - brain and spinal cord
PNS - sensory - efferent, motor - afferent
How is the motor section of the PNS split up?
somatic - voluntary
autonomic - involuntary
How is the autonomic section of the PNS split up?
sympathetic - ‘fight or flight’ response, ACh and Epinephrine
parasymapthetic - the house keeping and homeostasis, ACh
What are some of the regions of the brain?
cerebral hemispheres
diencephalon (thalamus) - relay station for sensory impulses
brain stem
cerebellum
What are some specialised regions of the cerebrum?
motor, sensory, visual, gustatory, olfactory, auditory
What kinds of glial cells might you find in the CNS and PNS?
CNS - ogliodendricytes(myelin sheaths)
astrocytes (absorb K+, NT and form blood-brain barrier),
microglia (clear debris, are scavengers),
ependymal cells (source of stem cells, barrier between compartments)
PNS - schwann cells (myelin sheaths),
satellite cells
What is significant about neuroglia?
they outnumber neurones by 5-10 fold and divide, they are the formation of most brain tumours
What is the function of astrocytes?
form a barrier between capillaries and neurones and control the chemical environment i.e. removing excess K+ and neurotransmitter, remove excess glutamate and convert it to glutamine to be re-used
What are the NS support cells and their features?
microglia(CNS) - spider like phagocytes disposing of debris
ependymal cells (CNS) - lines brain cavities, have cilia, aid circulation of cerebrospinal fluid
oligodendrocytes (CNS) - produce myelin sheath
Satellite cells (PNS) - protect the cell bodies
Schwann cells (PNS) - produce myelin sheath
What is special about the myelin sheath produced by schwann cells?
It is formed in a jelly roll form with nodes of ranvier to increase signal transduction. K+ and Na+ channels are concentrated here and this is where APs are regenerated
How does MS affect the nervous system?
it causes demyelination in the CNS targeting myelin or oligodendrocytes slowing or stopping signal transduction
How does Landry-Guillain-Barre syndrome affect the nervous system?
the most common PNS demyelinating disease causing segmental demyelination due to lymphatic infiltration of schwann cells
What can happen in demyelinating diseases where two neurones are close together?
cross talk between neurones can occur causing ectopically generated APs
Where is the trigger zone for APs in the neurone?
in the axon hillock
Where is the movement of APs in a neurone?
dendrites -> cell body -> axon hillock -> axon
What is the evidence for neurotransmission?
When two frog hearts are placed in solution and one is stimulated by the vagus nerve, transfer of that heart’s solution to the other heart, will stimulate the beating of that heart. the same effect is observed when using the vagus nerve on its own.
What is the typical movement of ions during neurotransmission?
Na+, Ca2+ inwards - causing depolarisaton
K+ outwards, Cl- inwards causing hyperpolarisation
What is the basis of neurotransmission?
depolarisation in neurones leads to transmitter release so neurones regulate the timing and location of transmitter discharge by invoking mechanisms of excitation and inhibition
What are some possible drug actions on neurotransmission?
agonists - i.e. Na+ agonist -> opens Na+ channel -> excitation
antagonists - i.e. Na+ antagonist -> closes channel -> inhibition such as local anaesthetics
What is the order of movement of ions during an AP?
All or nothing
Na+ comes into the cell generating the AP and depolarising the membrane
K+ goes out of the cell depolarising the membrane
The Na/K pump restores the configuration using ATP
How might neurotransmitter be removed from the synaptic cleft?
returned to the axon terminals or into glial cells - astrocytes
enzymes inactivate them - cholinesterases
diffuse out of the synaptic cleft
Give some examples of classes of neurotransmitters
amino acids - glutamic acid, glycine, GABA
monoamines - ACh, 5-HT, Serotonin, Histamine
catecholamines - dopamine, noradrenaline, adrenaline
How might a neurotransmitter exert its post-synaptic effects?
directly - gating the ionotropic receptors
indirectly - gating the metabotropic receptors
