Lecture 3 Flashcards
primitive nerve nets
-radially symmetric animals (cnidarian: jellyfish, hydra, anemones)
-neurons not specialized (can function as sensory, interneurons, or efferent)
-little preference for conductance direction (impulse radiates in every direction)
-propulsive movements
-no obvious integrating center (still have complex behaviours)
ganglia
-clusters of neuronal cell bodies, small independent integrating centers
-first seen in more complex cnidarians
connectives and commissures
-in segmented, bilaterally symmetrical animals
-connections between ganglia for more rapid transmission (e.g. L/R coordination)
-connected ganglia ultimately form longitudinal nerve cords
cephalization
-fusion of anterior ganglia in more complex animals
-sensory receptors abundant in head
-brain plays larger role in integration
echinoderms
-radially symmetrical
-descended from bilaterally symmetrical ancestor that likely had some cephalization
-bilaterally symmetrical larvae
-exception of increasing cephalization trend
cephalopods
-large brain: intelligence?
-can distinguish objects, can learn
-can change skin pattern, colour and texture
structure of a vertebrate nerve
-groups of axons from many neurons
-enclosed in successive layers of connective tissues
-most nerves contain axons of both afferent and efferent neurons (mixed nerves)
-some are purely afferent or efferent
CNS
brain and spinal cord
PNS
nerves, sensors and effectors
white matter
myelinated axons
gray matter
cell bodies and dendrites
vertebrate central nervous system
-dorsal and ventral horns and roots
-dorsal: afferent (cell bodies outside)
-ventral: efferent (cell bodies inside)
Oligodendrocytes
conduction speed (myelin sheath) in CNS
astrocytes
transport of nutrients, debris, neuroinflammation
microglia
maintenance, remove debris and dead cells, neuroinflammation
ependymal cells
line fluid-filled cavities (e.g. ventricles), often have cilia to circulate CSF
hindbrain
-medulla, Pons, cerebellum
-basic functions
midbrain
-mesencephalon
-tectum and tegmentum
-coordination of visual, auditory and sensory info (in mammals, main function is to connect forebrain with hindbrain)
forebrain
-telencephalon
-cerebrum (cerebral cortex, basal ganglia, amygdala, hippocampus), olfactory bulbs
-diencephalon
-hypothalamus/pituitary, thalamus, epithalamus
-complex integration of info
evolution of the CNS
-conservation of structure and function
-midbrain greatly reduced in mammals, big forebrain
-bony fish and birds: large midbrain and cerebellum (interpretation of sensory signal and coordination of movements)
cerebrum
processing of information, two hemispheres that are functionally unique
left brain
control of speech
right brain
perception and spatial relationships
human cerebral cortex
-cortex = outer layer of cerebrum - gray matter
-extensive, convergence and divergence across neural networks
-complicated cortical organization allows for complexity in cognitive function and flexibility in response
-involved in cognition, ability to concentrate, reason and think, etc
cortical folding
-increasing surface area, functional complexity of forebrain (correlates with intelligence)
-sulcus (sulci): groove
-gyrus (gyri): fold
frontal lobe
reasoning, planning, speech
parietal lobe
recognition, orientation, sensory
temporal lobe
auditory processing, memory, speech
occipital lobe
visual processing
cortical areas
specific areas correspond to particular functions
vertebrate CNS and PNS
-CNS and PNS communicate extensively
-CNS receives sensory/afferent inputs from PNS
-CNS integrates signals to generate a response
-sends efferent signals to PNS
divisions of the PNS
-skeletal muscles (motor or somatic)
-smooth muscles, cardiac muscles, and glands (automatic)
motor neurons
-innervate skeletal muscles
-longest neuron in body
-induce contraction and relaxation patterns for different movements (antagonistic muscle group)
Neurotransmitter at neuromuscular junction (NMJ)
-acetylcholine (ACh)(or glutamate in many inverts)
-effects always excitatory
effectors
-cardiac muscles
-smooth muscles
-glands
-organs
autonomic branch
-consists of two opposing systems
-tight regulation of physiological systems
antagonistic effects
-stimulatory vs inhibitory
-homeostatic regulation of most physiological processes
sympathetic (SNS)
-dominates during stress, physical activity
-“fight or flight” response
parasympathetic (PSNS)
-dominates at rest
-maintenance functions
-digestion
basal tone
-balance at rest
-organs receive inputs from branches under resting condition
SNS and PSNS structural organization - similarities
-2 neurons in series
-preganglionic and postganglionic neurons
-synapse at peripheral autonomic ganglion
-preganglionic cell body in CNS
-terminals in peripheral autonomic ganglion
-postganglionic cell body in peripheral autonomic ganglion
-terminals on effector organ
sympathetic
-short preganglionic neuron
-long postganglionic neuron
-many synapses per preganglionic neuron
-ACh (cholinergic synapse), norepinephrine (Adrenergenic synapse)
parasympathetic
-long preganglionic neuron
-short postganglionic neuron
-few synapses per preganglionic neuron
-ACh X2
sympathetic anatomical organization
-thoracic and Lumbar region (thoracolumnar)
-sympathetic chain ganglia next to spinal cord
parasympathetic anatomical organization
-cranial and sacral regions (craniosacral)
-ganglia close to effector organ (terminal ganglia)
structural differences between sympathetic NS vs parasympathetic
-location of cell bodies of preganglionic neuron in spinal cord
-location of ganglia (neuron length)
-number of connections (synapses) made by preganglionic neuron
