Nervous System Organization Flashcards
what is the big picture of the nervous system?
enable organisms to sense and react to the environment.
- has been evolving for billions of years
- increase survival and reproduction in changing environments
cnidarians
- simplest animals with NS
- nerve net: interconnected neurons for movement
- NO CENTRAL CONTROL ORGAN
echinoderms
- nerve ring: central control structure
- signal radial nerve (signals muscles)
bilateria
- lots of variation
- Platyhelminthes (Planarians)
- anterior end; eyespots for detecting light and brain
- ladder-type NS; 2 longitudinal nerve cords and transverse nerves (“rungs”)
Annelids and Arthopods
- more complex brain
- ganglia: segmentally arranged clusters of neurons
vertebrates (NS)
CNS- brain and spinal cord
PNS - nerves and ganglia
chiton
slowing moving -> simple
squid
fast moving -> complex
what is special about chiton and squid?
they are both molluscs, but they live different lifestyles
neuron
basic functional unity of NS
-conduct electrical signals, integrate info
neuron anatomy
- cell body: contains organells and nucleus
- dendrites (=”trees”); cytoplasmic extension from cell body - usually many and short, receive info
axons
- also cytoplasmic extensions from cell body - but usually one and long
- send info
- axon hillock: base of axon - where signals are generated
- synaptic terminals: end of axon - often branched
glia
- non-neuron cells of the NS
- MANY functions; neuron support, protections, maintenance, embryonic NS development
myelin sheath
bundles of insulation around axons - faster signaling
- in CNS: produced by oligodendrocytes
- in PNS: produced by Schwann Cells
radial glia
form tracks in developing embryos; help newly formed neurons migrate from neural tube
CNS
- contains interneurons -responsible for integration and process of info
- gray matter - mostly neuron cell bodies
- white matter - mostly bundled axons
brain
- ventricles with cerebrospinal fluid
- white matter (axons) inside
- gray matter (cell bodies) outside
spinal cord
- within spine
- links brain and rest of NS
spinal cord structure
- small central canal with cerebrospinal fluid
- gray matter surround canal - inside
- white matter surrounds gray - outside
spinal cord functions
- transmit impulses to/from brain
- reflex actions: rapid, involuntary response to stimulus
- ex: knee-jerk reflex; quad stretched unexpectedly -> helps you stay upright
PNS
- all remaining nervous tissue not part of CNS
- transmit info to/from CNS
- includes nerves: axons of many neurons held together with connective tissue`
what do sensory receptors do?
they detect stimuli
afferent neurons
send info from sensory receptor -> CNS
what are the two types of senses
visceral and somatic
visceral
not aware of - BP, thyroid hormone levels
somatic
are aware of - vision
efferent neurons
CNS -> effectors: no receptors
what are the two target systems of efferent neurons?
motor system and autonomic nervous system
motor system
- efferent neurons -> skeletal muscle
- voluntary and reflexes
- no receptors
autonomic nervous system
- efferent neurons -> glands, heart, smooth muscle
- what CNS controls that we are not aware of
what are the three divisions of the autonomic nervous system
- enteric: controls digestive tract, pancreas, gall bladder
- parasympathetic: “rest and digest”
- sympathetic: “fight or flight”
what are the three broad regions/categories of the vertebrate brain
forebrain, midbrain, and hindbrain
forebrain
sensory input, learning, complex processing
midbrain
coordinates routing on sensory input
hindbrain
involuntary activities
cerebrum
- derived from forebrain
- most prominent part of brain
- voluntary movement
- learning, emotion, memory, perception
divisions of the cerebrum
- right/left hemisphere
- left/right reversed perception/control
- corpus callosum: thick band of axons, connects 2 halves
cerebellum
- from hindbrain
- movement. balance, motor skills/coordination
diencephalon
- from forebrain
- thalamus: routes sensory info to correct part of cerebrum
- hypothalamus: regulates HS
brainstem
- basic life functions - respiration, heartbreat, BP
- 3 components: midbrain, pons, and medulla oblangata
pons
from hindbrain; respiratory and sleep centers
medulla oblongata
from hindbrain; continuous with spinal cord
