Nervous System Structure

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Nervous System Structure
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The Nervous System

• Central Nervous System (CNS)
• Peripheral Nervous System (PNS)

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Neuraxis

• Line drawn through the CNS
• From ________
• to ________

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Nervous system directions, in relation to the
neuraxis

• Anterior / Rostral
• Toward the nose
• (rOstral ? nOse)
• Dorsal
• Toward the back
• Superior
• Above
• Lateral
• Away from the midline
• Ipsilateral
• Same side

• Posterior / Caudal
• Toward the tail
• (cAudal ? tAil)
• Ventral
• Toward the belly
• Inferior
• Below
• Medial
• Toward the midline
• Contralateral
• Opposite side

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Nervous system planes

• Transverse
• Sagittal
• Horizontal

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Meninges

• Protective layers surrounding the CNS
• Dura Mater
• Arachnoid membrane
• Pia mater

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Ventricles

• Openings in the brain that contain cerebrospinal
  fluid (CSF)
• Lateral ventricles
• Third ventricle
• Fourth ventricle
• Cerebral aqueduct

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Cerebrospinal fluid

• Made in the choroid plexus
• Flows from the lateral ventricles
• ? 3rd ventricle ? cerebral aqueduct ? 4th
  ventricle
• ? Enters the subarachnoid space surrounding the
  CNS.

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Neural development

• Neural tube
• Hollow tube along the back of the embryonic cell
  mass
• Develops into the CNS
• Forms 3 ventricles at the rostral end
• Tissue surrounding ventricles ventricular zone
• Becomes forebrain, midbrain and hindbrain

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Neural development

• Forebrain
• Telencephalon
• Diencephalon
• Midbrain (Mesencephalon)
• Tectum
• Tegmentum
• Hindbrain
• Metencephalon
• Myelencephalon

See Chart on p. 44!
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Cellular development

• Founder cells
• Initial cells in the ventricular zone
• Pluripotent
• Symmetrical division
• Increases size of the ventricular zone
• Asymmetrical division
• Creates neurons while maintaining ventricular
  zone
• Adult brain stem cells in the ventricular zone

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Cellular development

• Radial glia
• Grow out from the ventricular zone to the surface
  of the cortex
• Guide new neurons to the surface of the cortex
• Ensure development of systematic pathways in the
  brain.

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Cellular development

• Cortical development ends with apoptosis
• Neurons grow into adult form with dendrites,
  axons terminal buttons
• Form connections with other neurons
• No connections neuronal death

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Forebrain - Telencephalon

• Telencephalon
• Cortex
• Limbic system
• Basal ganglia

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Telencephalon

• Cerebral cortex surrounds the cerebral
  hemispheres
• Convoluted in the primate brain, smooth in lower
  brains
• Gyri (singular Gyrus)
• Sulci (Sulcus)
• Fissures
• Cortex consists of densely packed brain cells
  (grey matter)

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Telencephalon - Cortex

• Four lobes of the brain
• Frontal
• Separated from parietal lobe at the central
  sulcus
• Parietal
• Temporal
• Separated from front/parietal lobes at the
  lateral fissure
• Occipital

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Cortex - Frontal lobe

• Prefrontal Cortex
• Rostral end of the brain
• Organization of thought, planning actions, and
  higher cognitive functions.

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Cortex - Frontal lobe

• Primary motor cortex (PMC)
• Located on the precentral gyrus
• Controls motor output
• Contralateral side of the body
• Somatotopic organization
• Motor association cortex
• Anterior to the PMC
• Plans movement

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Cortex - Parietal lobe

• Primary Somatosensory Cortex
• Located on the postcentral gyrus
• Receives contralateral sensory information
• Somatotopic organization
• Somatosensory Association Cortex
• Located posterior to the PSC
• Somatosensory perception and memories

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Cortex - Temporal lobe

• Primary Auditory Cortex
• Located on the upper surface of the temporal lobe
• Receives auditory input
• Auditory Association Cortex
• Surrounds the PAC
• Analyzes auditory information
• Auditory perception and memory storage

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Coretex - Occipital lobe

• Primary Visual Cortex
• Located on the inner surface of the occipital
  lobes
• Input from the contralateral visual field
• Visual Association Cortex
• Located lateral to the PVC
• Extends into the ventral temporal lobe
• Analyzes visual information
• Involved in visual perception

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Cortical connections

• Corpus Callosum thick axon bundle connecting
  corresponding regions of each hemisphere
• Coordinates sensory processing and motor output
  between hemispheres

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Telencephalon Limbic system

• Limbic system
• Located within the telencephalon, surrounded by
  cerebral cortex
• Learning, memory and emotion

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Limbic system

• Cingulate cortex
• Emotion, learning and memory
• Amygdala
• Emotion, learning and memory
• Hippocampus
• Learning and memory
• Mammillary bodies
• Memory
• Fornix
• Connects the hippocampus with the mammillary
  bodies
• Olfactory bulb
• Sense of smell

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Telencephalon Basal ganglia

• Basal ganglia are involved in motivation and
  generation of movement
• Include
• Caudate nucleus
• Putamen
• Globus pallidus

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Forebrain - Diencephalon

• Diencephalon
• Located between the telencephalon and the
  midbrain
• Includes
• Thalamus
• Hypothalamus

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Diencephalon

• Thalamus
• Composed of nuclei that relay information to the
  proper cortical regions
• Lateral geniculate nucleus receives information
  from the _____________, projects it to the
  _____________.
• Medial geniculate nucleus receives information
  from the _____________, projects it to the
  _____________.
• Projection fibers axons that carry information
  from the thalamus to the cortex.

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Diencephalon

• Hypothalamus
• Controls the autonomic nervous system and the
  endocrine system
• Two major structures control endocrine function
• Anterior pituitary gland
• Posterior pituitary gland

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Midbrain (Mesencephalon)

• Structurally and evolutionarily between the
  diencepalon and the hindbrain
• Only two major structures
• Tectum
• Tegmentum

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Midbrain - Tectum

• Located on the dorsal mesencephalon
• Superior colliculi
• Inferior colliculi

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Midbrain - Tegmentum

• Located on the ventral mesencephalon
• Reticular formation
• Periaqueductal grey area
• Red nucleus
• Substantia nigra

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Hindbrain

• Most primitive brain structure responsible for
  basic survival functions
• Surrounds the fourth ventricle
• Consists of the metencephalon and myelencephalon

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Hindbrain - Metencephalon

• Cerebellum (dorsal brainstem)
• Integrates sensory and motor information to
  coordinate movement
• Pons (ventral brainstem)
• Projects information from
• cortex to cerebellum
• Role in sleep and arousal

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Hindbrain - Myelencephalon

• Medulla oblongata
• Caudal-most region of the brain
• Cardiovascular respiratory functions, muscle
  tone, and arousal

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Spinal cord

• Cells of the spinal cord
• Grey matter
• Cell bodies and unmyelinated axons
• Dorsal horns
• Ventral horns
• White matter
• Myelinated axons

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Spinal cord

• Spinal nerves
• 31 pairs of spinal nerves attach to the spinal
  cord
• Each spinal nerve consists of
• Motor efferent (output)
• Sensory afferent (input)
• As each nerve approaches the spinal cord, it
  splits into a dorsal and ventral root

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Spinal cord

• Dorsal root carries the sensory axon
• Cell body in the dorsal root ganglion
• Axon enters the spinal cord and either
• Continues
• Synapses

• Ventral root carries the motor axon
• Cell body in the ventral horn of the spinal cord
• Axon carries motor information out to the
  periphery

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Cranial nerves

• 12 pairs of cranial nerves attach to the ventral
  surface of the brain.
• Some sensory
• Some motor
• Some mixed
• Sensory motor functions of the face, head, neck
  and throat.

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Peripheral Nervous System
Somatic Nervous System
Autonomic Nervous System
Sensory input Motor control
Parasympathetic Nervous System
Sympathetic Nervous System
Fight or Flight Response Utilization of energy
resources
Rest Digest Response Conservation of energy
resources
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Autonomic nervous system

• Autonomic ganglia
• Preganglionic neurons
• Postganglionic neurons
• Sympathetic nervous system
• Sympathetic chain
• Parasympathetic nervous system