BIOL 225 Lecture 49: Ch 49 Notes
14 May 2018
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Chapter 49→ Notes
The Nervous system
49.1 Nervous system consists of circuits of neurons and supporting cells
• Ability to sense and react originated billions of years ago with prokaryotes →
detect change sin their environment and respond to these changes that
enhanced their chances of survival and reproductive success.
• Cnidarians → Hydras, jellies= radically symmetrical bodies organized around
a digestive compartment, the gastrovascular cavity → interconnected nerve
cells form a diffuse nerve net (controls expansions and contraction of
gastrovascular cavity) but lack clusters of neurons that perform specialized
functions
• Complex animals multiple nerve cells→ nerves (organize info flow toward
specific routes through NS)
• Sea stars (echinoderm)→ radial nerve =linked to a nerve net (receives input
n sends signals)
• Flatworms (Planarian) nerve cords and transvers nerves. Small brain and
longitudinal nerve cords → apart of CNS
• Non-segmented worms (nematode)→ 302 neurons → adult worm
• Annelids and arthropods → have many more neuron→ regulated by
complicated brain and by ventral nerve cords that contain ganglia
(segmentally arranged clusters of neurons)
• Molluscs→ slow-moving like clams and chitons… little or no cephalization
• Molluscs→ like octopuses and squids→ most sophisticated NS→ millions of
neurons
• Invertebrates→ brain and the spinal cord form the CNS; nerves and ganglia
from PNS.
Organization of the Vertebrate Nervous System
• CNS → brain and spinal cord work together
• Brain= integrative center → underlies the behaviour
• Spinal cord= runs lengthwise inside the vertebral column (spine)= conveys
info to and from brain and generates the patterns of locomotion
• Spinal cord→ acts also independently of brain as part of simple nerve circuits
that produce reflexes (body’s automatic responses to certain stimuli
• Reflex helps you pull your hand off stove before the message of pain is
processed in brain
• Embryotic development, CNS develops form the hollow dorsal nerve cord→
hallmark of chordates
• The cavity of the nerve vord gives rise to the narrow central canal of the
spinal cord as well as the ventricles of the brain
• Both canal and ventricles fill with cerebrospinal fluid → formed by the brain
by filtration of arterial blood
• CSF eventually drains into veins from ventricles and central canal→ supplies
brain with nutrients and hormones and wastes away
• Mammals→ CSF cushions brain n spinal cord by circulating b/w connective
tissue that surround the CNS
• Grey matter= neuron cell bodies, dendrites, unmyelinated axons, glia
• White matter= myelin sheaths
• White matter in spinal cord lies on the outside→ consistent with its function
in linking the CNS to sensory and motor neurons of the PNS
• White matter in brain is on the inside→ role in signalling b/w neurons in
brain in learning, feeling emotions, processing sensory info…
Glia
• Found in brain and spinal cord
• Play a role in the development of the NS
The Peripheral Nervous System
• Transmits info to and from the CNS and plays a large role in regulating an
animal’s movement and internal environment
• Sensory info reaches CNS along PNS neurons designated as afferent
• Following info processing within CNS, instructions then travel to muscles,
glands and endocrine cells along PNS neurons designated as efferent
• Olfactory nerves→ conveys only sensory info from nose to brain
• PNS has two efferent components: the somatic and autonomic nervous
system
• Somatic nervous System= includes the motor nerves (carry signals from the
CNS to skeletal muscles, and sensory nevrs, which carry signal from
periphery to the CNS)→ this control of skeletal muscles can be voluntary or
involuntary
• Autonomic Nervous System= involuntary → smooth and cardiac muscle
regulation
• Autonomic Nervous System→ 3 divisions = sympathetic, parasympathetic
and enteric→ together control digestive, cardiovascular, excretory and
endocrine systems
• Sympathetic and Parasympathetic are antagonistic (opposite) function in
regulating organ function
• Sympathetic→ fight-or-flight→ heart beats faster
• Liver converts glycogen to glucose and adrenal medulla increases secretion
of epinephrine
• Parasympathetic division→ causes opp. Responses to that of sympathetic→
promotes calming and self-maintenance “rest and digest”
Document Summary
Sea stars (echinoderm) radial nerve =linked to a nerve net (receives input n sends signals: flatworms (planarian) nerve cords and transvers nerves. Invertebrates brain and the spinal cord form the cns; nerves and ganglia from pns. Glia: found in brain and spinal cord, play a role in the development of the ns. Liver converts glycogen to glucose and adrenal medulla increases secretion of epinephrine: parasympathetic division causes opp. 49. 2 the vertebrate brain is regionally specialized: reticular formation a diffuse network of neurons in the core of the brainstem. The organization of the human brain: the cerebrum =controls skeletal muscle contraction, centre for learning, emotion, memory and perception. Divided into right and left cerebral hemispheres. Cerebral cortex (divided into right and left as well) vital for perception, voluntary movement and learning. Left side receives info and controls right side of body and right side of vice versa: cerebellum= movement and balance, helps in learning and rememebering motor skills.
