Lecture 3 Flashcards
What impairs/blocks nerve conduction?
cold pressure impairs impulse conduction = interrupts blood circ = no o2
sedatives and anaesthetics block nerve impulses by altering membrane permeability = no Na+ entry = no AP
Why do fibers with myelin sheaths transmit signals faster?
nerve impulses jump from node to node
What is an example of a poison that blocks nerve impulse?
tetrodoxin - produced by pufferfish
What is a synapse?
neurotransmitter chemical crosses gap to transmit signal from one neuron to the next
neurotransmitter binds to receptor on the next neuron
What are the two types of synapses?
most neurons communicate via chemical synapses
there are also physical synapses
What are the steps to a chemical synapse?
- AP reaches axon terminal
- electrical change opens Ca2+ channels
- vesicles containing neurotransmitter fuse with axon membrane and release transmitter
- neurotransmitter diffuses across synapse to bind to receptors on next neuron
- series of events from before occurs
After a synapse what happens to the neurotransmitter?
neurotransmitter is removed from synapse either by diffusion away by reuptake into the axon terminal or by enzymatic break down
What are the four classes of neurotransmitters?
AA: glutamate, aspartate, glycine, GABA
Monoamines: catecholamines like dopamine, adrenalin and noradrenalin, seratonin
Acetylcholine
Neuroactive peptides: endogenous opioids, peptides from hypothal/pit gland
Where does acetylcholine work?
crosses the neuromuscular junctions
ACh excites the muscle-cell membrane, causing depolarization and contraction of the muscle fibre
What happens if ACh is not released?
muscle cannot contract
What does cholinesterase do?
breaks down Ach
Draw out table of neurotransmitters
slide 14
What is the function of serotinin/5-hydroxytryptamine (5-HT)
involved in eating, circadian rhythmicity, neuroendocrine, function sleep, mood, anxiety
What is 5-HT synthesized from?
tryptophan
What is 5-HT an intermediate of?
transformation of tryptophan to serotonin
What is the action of a serotonergic drug?
selective serotonin reuptake inhibitor prolongs the action of 5-HT in the synapse by preventing its uptake
What is mucosal 5-HT present in?
entero-chromaffin ccells of the mucosal epithelium triggers persitaltic and secretory reflexes through the activation of enteric and sensory neurons
What occurs in birds with lower levels of 5-HT?
feather pecking
How many cranial nerves are there?
12 cranial nerves
What are the 12 cranial nerves?
- olfactory
- optic
- oculomotor
- trochlear
- trigeminal
- abducens
- facial
- auditory
- glossopharyngeal
- vagus
- spinal accessory
- hypoglossal
What are some characteristics of spinal nerves?
leave vertebral column and travel to muscles/sensory receptors they innervate, branching repeatedly as they go
What is the difference between afferent and efferent axons?
afferent axons bring information inward, toward CNS
efferent axons send information outward
What are the steps of a neural reflex?
receptor neuron receives sensory input, which it sends to the brain for processing, the brain analyzes information and determines the appropriate output:
reflex - sensory input -> integration -> motor output
What are reflexes?
rapid, predictable, involuntary responses
What parts of the NS are reflexes involved in?
CNS and PNS
What is the difference between a somatic and autonomic reflex?
somatic - skeletal muscles activated
autonomic - regulate body function = smooth muscles, glands etc.
What are the 5 elements of a two neuron reflex arc?
- sensory receptor
- effector organ
- sensory neuron
- motor neuron
- integration center: spinal cord and or interneurons between sensory and motor neurons
What are the steps to a patellar reflex in cats and dogs?
- sensory fiber is stimulated by the tendon hammer
- impulse travels via the sensory nerve to the ventral horn in the grey matter of the spinal cord
- it synapses with the motor neuron whcih affects a muscular contraction
What is a withdrawal reflex?
three neuron reflex - limb withdrawn from painful stimuli, interneuron involved
Do all withdrawal reflexes result in pain?
no
How can electronic feeders be used for cognitive enrichment in pigs?
pigs trained to learn the link between sound given by electronic feeder and a feed reward, can reduce aggression
What are the components of the cerebral hemisphere?
cortex and basal nuclei
What is the function of the cortex?
gray matter, cerebrums outer layer, localizes and interprets sensory inputs, control voluntary and skilled skeletal muscle activity, acts in intellectual and emotional processing
What is the function of the basal nuclei?
islands of grey matter, buried deep within the white matter of the cerebral hemispheres, subcortical motor centers help control skeletal muscle movements
What is the result of malfunction of basal nuclei?
huntington or parkinsons disease
What is the function of the thalamus?
relays sensory impulses to the cortex, relays impulses between the cortex and lower motor systems, involved in memory
What is the function of the hypothalamus?
integration of the ANS, regulates body temperature, food intake, water balance, thirst, regulates hormonal output
What is the function of the limbic system?
Includes cerebral and diecephalon structures, mediates emotional responses, memory processing
What is the limbic system comprised of?
functional group of integrating centres in cerebral cortex, thalamus and hypothalamus
hippocampus and amyglada
How do smells trigger strong emotions/memories?
olfactory brain parts in the cranial portion of cerebrum, direct connection to areas that are strongly implicated in emotion and memory
What are the various structures of the brain stem?
mid brain, pons, medulla oblongata, reticular
What is the function of the mid brain?
contains visual and auditory reflex centers, subcortical motor centers, nuclei for cranial nerves
What is the function of the pons?
cooperates with medulla to control respiration, relays info from cerebrum to cerebellum
What is the function of the medulla oblongata?
relays ascending pathways from skin and proprioceptors, contains nuclei controlling heart and respiratory rate, vomiting etc.
What is the function of the reticular formation?
maintans alertness, filters out repetitive stimuli, helps regulate skeletal and visceral muscle activity
What is the function of the cerebellum?
processes information from the cerebral cortex, proprioceptors, visual and equilibrium pathways, responsible for proper balance and posture
What are the meninges?
three tissue membranes that cover and protect the CNS
dura mater
arachnoid mater
pia mater
What is the dura mater?
the outermost layer - is a double layered membrane around the brain and single layered around spinal cord
What is the arachnoid mater?
the middle layer, has web like features
What is the pia mater?
innermost membrane - delicate and clings tightly to the surface of the brain and spinal cord
What is CSF?
watery liquid similar to blood plasma in its content, contains less protein and more vitamin C and different ion composition, forms cushion around the brain and spinal cord and protects against physical blows and other trauma
What does the blood brain barrier do?
neurons kept separated from bloodborne substances
composed of least permeable capilalries in the whole body
bound together by tight junctions all around
What can pass through the blood brain barrier?
only water, glucose, and essential AA can pass easily through
