Outline-2, BIO 3220, Nervous System


A. General function

1. Sensory/receptors

2. Integration – memory

3. Response, motor/effectors

B. Classification

1. Central Nervous System – Brain & Spinal Cord

2. Peripheral Nervous System

a. Afferent – Sensory information from periphery towards CNS

1. Somatic

2. Visceral

b. Efferent – Motor information from CNS to periphery

1. Somatic

2. Visceral = Autonomic Nervous System

a- Sympathetic Nervous System (fight or flight)

b-Parasympathetic Nervous System (rest & relaxation)

C. Neuron

1. Cell body– Organelle-containing part of cell

a. Ganglion – Group of cell bodies in PNS

b. Nucleus – Group of cell bodies in CNS

2. Cytoplasmic process

a. Axon= Fiber

1. Fiber tracts – CNS

2. Nerve – PNS

3. Sensory vs Motor vs Mixed

b. Dendrite – Receptor

3. Synapse – Junction between neurons

a. Telodendria – Ends of axon entering synapse

b. Neurotransmitters – Chemicals bridging synapse

D. Neuroglia – Provide mechanical and nutritive support to neurons

1. Ependymal cells – Line the neurocoel

2. Oligodendroglia – Produce Myelin in CNS; Myelin (white matter) speeds up nerve impulse transmission

3. Astrocytes – Maintain blood-brain-barrier

4. Microglia – Phagocytes

5. Schwann Cells – Produce myelin in PNS

E. Development

1. Neurulation

2. Neural tube

a. Germinal layer

b. Mantle layer – gray

c. Marginal layer – white – Cytoplasmic extensions, lack nuclei

3. Neuroblasts – Form neurons

4. Spongioblasts – Form neuroglia

5. Alar vs Basal plate – Dorsal and ventral gray matter

6. Neural crest cells

a. First order sensory neuron – Has cell bodies in sensory ganglia

b. Second order sensory neuron = association neuron – Within the CNS

c. Exceptions of the typical cell body of sensory neurons being in ganglia:

1. Cranial nerves I, II

2. Proprioception pathways of cranial nerves I – X


1. Location & Function

2. Meninges

a. Meninx Primitiva – In fish

b. Leptomeninx – Inner membrane in higher vertebrates

c. Dura mater – Outer membrane in higher vertebrates

d. Pia mater – Mammals only, inner splitting of leptomeninx

e. Arachnoid & Subarachnoid space – Mammals only, outer layer splitting from leptomeninx. Subarachnoid space contains cerebrospinal Fluid, or CSF.

3. Gray matter – Contains nuclei, nonmyelinated neurons, center of spinal cord

4. White matter – Myelinated ascending and descending tracts in peripheral spinal cord

5. Spinal nerves

a. Metamerism

b. Cauda equina – Caudal-most set of spinal nerves resembling a horse’s tail

c. Occipitospinal nerves – Anamniote nerves innervating hypobranchial muscles

d. Spinal Nerves are Mixed nerves: Dorsal and Ventral root – Dorsal root containing sensory information/ Ventral root containing motor information

e. Dorsal and ventral ramus – After exiting the vertebrae, spinal nerves branch into a dorsal branch supplying epaxial muscles and a ventral branch supplying hypaxial muscles and the autonomic nervous system.

f. Plexuses – Networks of successive spinal nerves supplying limbs


1. Prosencephalon – “Forebrain”, embryonic

a. Telencephalon

1. Rhinencephalon

a. Olfactory bulbs

b. Olfactory tract

c. Olfactory lobe

2. Cerebral hemispheres

a. Paleostriatum – Primary region in fish, responsible for olfactory reflexes

b. Neostriatum – Beginning with reptiles, more nuclei, tracts, and neuroglia

c. Hyperstriatum – Primarily in birds for stereotypical behavior

d. Corpus striatum = basal nuclei – Remnants of Paleostriatum and neostriatum buried in mammalian brain, responsible for repetitive and stereotyped movements

e. Cortex – Starting in reptiles but up to billions of neurons that must be folded in skull to fit in mammals

1. Motor & Sensory – Responsible for voluntary movement and conscious sensations

2. Memory & Integration

3. 4 lobes – In mammals, named according to skull bones

3. Lateral ventricles – Ventricles are cavities in brain

a. CSF – Cerebrospinal Fluid

1.  Formation – from blood vessels called choroid plexus

2. Function – Cushion, protection, nutrients

b. Diencephalon

1. Epithalamus

a. Pineal body – Light receptor in agnathans, endocrine (hormone producer) in gnathostomes.

b. Parapineal = parietal eye – Monitors photoperiods in some fish, lampreys, some tadpoles

c. Habenula – Olfactory reflexes in blood hounds, sharks

2. Thalamus

a. Sensory relay

b. Intermediate mass = interthalamic adhesion

3. Hypothalamus

a. Optic chiasma

b. Infundibular stalk/Posterior Pituitary

c. Function – Endocrine, regulates ANS, emotions, water balance, thermostat, hunger & satiety

4. Third ventricle

a. Interventricular foramen

b. Cerebral aqueduct

2. Mesencephalon – Midbrain of embryo, term used in adult as well

a. Optic lobes – Especially well developed in many birds

b. Auditory lobes – Auditory reflexes such as jumping when hearing loud sound

-Corpora Quadrigemina

c. Cerebral peduncles – Descending motor tracts from cortex

d. Cerebral aqueduct

3. Rhombencephalon – Embryonic hindbrain

a. Myelencephalon

1. Medulla oblongata

a. Pyramids – Crossing of motor and sensory tracts

b. Function – Vital reflexes such as breathing, connection between brain and spinal cord for ascending and descending pathways

b. Metencephalon

1. Cerebellum – Coordination and balance; quite large in birds and mammals

2. Pons – “Bridge” between different parts of brain

c. Fourth ventricle – Containing CSF

H. CRANIAL NERVES– see Cranial Nerves page


1. Visceral efferent to smooth & cardiac muscle and glands

2. Involuntary

3. Sympathetic vs Parasympathetic

a. Functional differences – Sympathetic is “fight or flight” response; Parasympathetic is “rest and relaxation” response

b. Structural differences – Sympathetic nerves travel with spinal nerves in thoracolumbar region; Parasympathetic nerves travel independent of spinal nerves in sacral region and along with cranial nerves III, VII, IX, X

4. Preganglionic neurons – Exit CNS and synapse in peripheral ganglion

5. Postganglionic neurons – Travel from ganglion to effector

6. Autonomic ganglia

a. Paravertebral

1. Sympathetic trunk – Interconnecting chain of sympathetic ganglia traveling parallel to spinal cord allowing for divergence of pathways

2. White ramus communicans – Branching of preganglionic neuron away from spinal nerve in SNS

3. Gray ramus communicans – Branching of postganglionic neuron to rejoin spinal nerve in SNS

b. Collateral

1. Splanchnic nerve

2. Cardiac nerve

3. Head and abdomen

c. Terminal ganglia

7. Cholinergic – Releasing acetylcholine as neurotransmitter

8. Adrenergic – Releasing norepinephrine as neurotransmitter

9. Adrenal medulla – Is part of SNS and releases epinephrine and norepinephrine to prolong and exaggerate the fight or flight response