Cells of the Nervous System Flashcards
What are the four functional regions of the cerebral hemispheres?
frontal, parietal, temporal and occipital
Whis the function of the frontal lobe?
emotions, feelings etc
What are the functions of the parietal lobe?
motor and sensory processing
What are the functions of the temporal lobe?
sound and hearing
What are the functions of the occipital lobe?
visual processing
What are the three main parts of the brain stem in descending order?
midbrain, pons, medulla
What is special about the midbrain in terms of cranial nerves?
it is the target/ source of all cranial nerves and numerous functions
What does the cerebellum control?
motor coordination, balance and posture
What is the cerebellum?
hindbrain structure attached to the brainstem
What is the spinal cord?
nerve cells (protected by the vertebrae) which are projected out to areas of the peripheral nervous system. (It is a conduit for neural transmission and co-ordinates some reflex actions)
Where does the spinal cord extend from?
medulla
Name and describe types of neuron
- unipolar (1 axonal projection from cell body) 2. Psuedo-unipolar (one projection that divides into two) 3. Bipolar (2 projections from the cell body) 4. multipolar (numerous projections from cell body (100s to 1000s)
What are the three types of multipolar neuron?
pyramidal (pyramid shaped cell body), purkinje cells (GABA neurons found in cerebellum), golgi cells (GABA neurons found in the cerebellum
What are 3 features of neurons?
excitable cells of CNS, heterogeneous morphology, non-dividing cells
What is the Soma and what does it contain?
(cell body; perikaryon), contains nucleus and ribosomes, neurofilaments for structure and transport.
What is the axon and what are some features?
long process (nerve fibre) originates from soma at axon hillock, can branch into collaterals, usually covered in myelin
what are the dendrites and what are their features?
highly branched cell body not covered in myelin, receive signals from other cells
what is the most abundant cell type of the CNS?
astrocytes
astrocyte 3 functions
- structural cells (of blood-brain barrier, and holding neurons together)
- cell repair (produce neurotropic factors for growth and maintenance of neuronal cells)
- homeostasis (neurotransmitter removal and reuptake)
oligodendrocyte function
produce myelin
oligodendrocyte description
CNS - numerous projections that form internodes of myelin. One oligodendrocyte myelinates many axons.
schwann cell
produce myelin for peripheral nerves (not CNS), one schwann cell myelates one axon segment (wraps around the axon).
microglial cells
specialised cells similar to macrophages that perform immune function in CNS
ependymal cell
epithelial cells that line fluid filled ventricles, regulating production and movement of cerebrospinal fluid
list the types of neuroglia
how do the CNS cells all fit together?
which are the four major ions of the resting membrane potential
K+, Na+, Cl-, Ca2+
What are the relative concentrations of Na+ and Cl- extracellularly to neurons?
high
what is the relative concentration of potassium outside of neurons
low extracellular K+
why does myelin prevent action potentials from spreading?
high resistance and low capacitance
where do sodium and potassium pumps accumulate in the membrane?
nodes of ranvier (between myelin sheaths)
what is a node of ranvier?
small gap of myelin intermittently along axon
what happens during the propagation of an action potential?
- propagated by VG Na+ channels opening
- Na+ influx
- Membrane depolarisation
- AP moves along neuron
- VG K+ channels open and K+ efflux from axon
- Repolarisation
What happens when the action potential reaches the voltage gated Calcium channels at the presynaptic terminal?
Ca2+ influx –> vesicle exocytosis, neurotransmitter released from vesicle
What happens after neurotransmitter is released into synaptic cleft?
binds to receptors on post synaptic membrane, then dissociates from the receptor
how is neurotransmitter reuptaken?
- metabolised by enzymes in post synaptic cleft
- recycled by transporter proteins
types of synapse
- axodendritic synapse - connection between presynaptic terminal and neuronal dendrite
- axosomatic synapse - presynaptic terminal terminates on cell body
- axoaxonic synapse - presynaptic terminal terminates on axon of another neuron
what is the muscle membrane known as?
sarcolemma
After Ca2+ enters the presynaptic membrane at the neuromuscular junction, which neurotransmitter is released?
acetylcholine (ACh)
What is the cytoplasm of a muscle cell known as?
sarcoplasm
which receptors does ACh bind to when it reaches the sarcolemma at the neuromuscular junction?
nicotinic ACh receptors
What happens when ACh binds to nicotinic ACh receptors on the sarcolemma?
Depolarisation - Na+ influx and change in end-plate potential (EPP) (same as membrane potential)
how does the action potential at the sarcolemma spread to the rest of the muscle
T-tubule membrane
what is a minature EPP?
one molecule of ACh released - causes minature end plate potential, not enough to cause entire action potential. To depolarise the muscle, you need a summation of mini EPPs.
What is the location, function and effect of sarcoplasmic reticulum?
- surrounds each myofibril - contractile units of muscle
- Stores Ca2+ ions for Ca2+ release following sarcolemma depolarisation
- Ca2+ release causes myofibril contraction and muscle contraction
what does Ca2+ release do to the myofibril?
activates actin and myosin
what does the botulinum toxin do?
acts on area of cell membrane and prevents release of ACh by preventing vesicle fusion to the membrane
what happens in myasthenia gravis?
- autoimmune disorder forming antibodies to the nicotinic ACh receptor (specifically the muscle type receptors)
- causes muscle weakness
what happens in lambert-eaton myastenic syndrome?
- antibodies directed at voltage gated calcium channels on pre sysnaptic terminal
- causes muscle fatigue
What causes AP to spread?
Slight depolarisation of adjacent segment of axon causes influx of sodium ions
