Download The Brain - Midlands State University

The Brain, Spinal Cord,
Meninges, Cerebro-Spinal Fluid,
& Nerves
Obert Tada
Department of Livestock & Wildlife Management
Midlands State University
Introduction
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As vertebrates evolved, the structure of their
brains became more complex.
The complexity is evident in the latter stages
of brain development of higher vertebrates.
Contents
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Cerebrum
Interbrain
Brain Stem
Spinal Cord
Meninges
Cerebral Spinal Fluid
Nerves (Spinal, Cranial, Autonomic)
CNS Metabolism
Structure & Function of the
Vertebrate Brain
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The vertebrate brain develops from three anterior bulges
of the spinal cord
These bulges give rise to the:
 Forebrain
 Telencephalon
 Diencephalon
 Midbrain
 Mesencephalon
 Hindbrain
 Metencephalon
 Myelencephalon
Cerebrum (Cerebral
Hemispheres)
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Cortex (Gray)
 High Area
 Low Area or Groove
 Fissure (Deep Groove), Sulcus (Shallow Groove)
 Acquired late in vertebrate evolution
 Higher Order Functions:
 Consciousness/Awareness, Association/Intelligence, Learning
 Possesses Motor Areas (Movement)
 Contralateral control
 Size of motor area directly related to number and complexity
of skeletal muscle movements
 Contains Sensory Areas
 Somesthetic, Visual, Auditory, Olfactory
Cerebrum (Cerebral
Hemispheres)
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Medullary Substance (White)
 Myelinated nerve fibers beneath the cerebral cortex
 Association fibers
 Connect different parts of cortex
 Commissural fibers
 Connect two hemispheres of cerebrum
 Projection fibers
 Connect Cortex with other parts of the brain and spinal
chord
Basal Ganglia
 Controls basic movement (not sophisticated)
 --Walking, eating, fighting, sex
 Well developed in birds where it controls all movements
Cerebellum
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Makes adjustments to motor signals from the
cerebrum
Receives signals from:
 Tactile & Propioception
 Equilibrium apparatus of inner ear
 Visual cortex
 Motor cortex
Ipsilateral control
Interbrain (Diencephalon)
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Pituitary/Hypophysis
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Hypothalamus
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Endocrine Gland
Integration of functions of the ANS (rage & anger)
Homeostasis
 Temperature regulation, & Hunger and Thirst
Thalamus
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Endocrine Gland
Relay center from body to Cerebral Cortex
Relay center of impulses within the brain
Epithalamus
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Olfactory correlation center
Pineal gland (Produces Melatonin)
 Seasonal Breeding, & Daily Rhythms
Brain Stem
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Midbrain
 Visual Reflex Center
 Auditory Reflex Center
 Nuclei (2 Cranial Nerves) and fiber tracts
Pons and Medulla Oblongata
 Contain many ascending and descending tracts
 Nuclei for rest of cranial nerves
 Postural reflexes
 Other reflex centers
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heart rate
vasomotor tone
respiration
motor & secretory activity of digestive tract
The Spinal Chord
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Caudal continuation of the medulla
Segmented with vertebral segments
 Each segment gives rise to a pair of spinal nerves
Centrally located Gray Matter
 "Gray H“
 Cell bodies and processes
Peripheral White Matter
 Contains sensory and motor tracts
Narrows as you move caudally
Terminal end--Cauda equina
The Meninges
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Meninges of the Brain
 Coverings of Brain (and spinal chord)
 Dura Mater, Arachnoidea, & Pia Mater
 Subarachnoid Space contains Cerebral Spinal Fluid
 Pia Mater lines follows all fissures and grooves into the brain
 Lies between brain and blood vessels
Meninges of the Spinal Chord
 Same make-up
 Epidural Space
 Fatty area outside Dura Mater
 Innervated by Spinal Nerve Projections (Roots)
 Used in local anesthesia
Ventricles of the Brain
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Four Cavities in the Brain
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Two lateral right and left (1st and 2nd)
3rd Ventricle
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4th Ventricle
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Surrounds Interbrain
Lies beneath Cerebellum
connects subarachnoid space through foramina
Contain Choroid Plexus
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Tufts of Capillaries
Secrete Cerebral Spinal Fluid
Cerebral Spinal Fluid
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Circulation
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Ventricles to Subarachnoid Space to Venous Blood
Pressure Driven
Function
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Derived from Blood Plasma
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Principle Function
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--Thin and Watery
--No cells except for a few lymphocytes
--Brain Cushion
Some Lymphatic Function
Nerves (PNS)
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Spinal Nerves
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A left/right pair is derived from between
every vertebra, except the coccygeal
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Cervical (one extra at cranial end)
Thoracic
Lumbar
Sacral
Coccygeal
Spinal Nerves
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Organization
 i. Dorsal Root
 Afferent impulses (Sensory)
 ii. Dorsal Root Ganglion
 Afferent neuron cell bodies
 iii. Ventral Root (Motor)
 Efferent impulses
 iv. Roots join to form mixed nerve
 Afferent and Efferent pathways
Spinal nerves supply innervations to areas dorsal and ventral to
transverse process of vertebra
Appendages innervated by ventral branches of several spinal
nerves
 Join to become plexuses
Cranial Nerves
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12 pairs
Usually innervate structures in head and
neck
Exception is Vagus Nerve (X)
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Pharynx and larynx
Visceral structures of thorax and abdomen
Mixed, motor, or sensory
Autonomic Nerves
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Innervate Smooth muscle, Cardiac muscle and Glands
Divisions
 Sympathetic
 Parasympathetic
 Generally have opposite responses
 Each consists of two neurons
 preganglionic, postganglionic
Sympathetic
 Usually involved in "Fight, Fright, Flight" response
 Originate from thoracic and lumbar segments
 Short preganglionic, Long postganglionic
 Ganglionic connections form paired nerve trunk that is parallel
to the spinal chord
 Sympathetic trunk
Autonomic Nerves
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Parasympathetic
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Usually involved in tranquil or restful
situations
Originate from brain and sacral segments
Long preganglionic, Short postganglionic
Brain originators follow cranial nerves
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III, VII, IX, X
Sacral originators follow pelvic spinal
nerves
Autonomic Neurotransmitter
Receptors
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Sympathetic
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Norepinephrine
Adrenergic Receptors
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Alpha 1 >>Blood vessels
Beta 1 >>Heart
Beta 2 >>Bronchioles
Parasympathetic
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Acetylcholine
Cholenergic Receptors
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Nicotinic >>Muscles
 Also found in Spinal, Cranial nerves and Sympathetic
Nerves
Muscarinic >>Organs and Tissues
Autonomic Nerves
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Autonomic Reflex
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Afferent/Efferent Mechanisms
Impulses do not reach conscious level
Examples
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Blood Pressure
Heart Rate
Digestive and Urinary Activity
Central Nervous System
Metabolism
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Metabolism
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Energy from CHOs, primarily glucose
Insulin not required
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Very high oxygen need
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Simple Diffusion of Glucose
20% of whole body
Gray needs 3-4X more than White Matter
Blood-Brain Barrier
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Many substance in blood can't enter cells of CNS
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Tight Junctions rather than Slit Pores in Endothelium
Central Nervous System
Metabolism
Astrocytes
 Lie between CNS cells and Endothelium
 Selective to the Materials they transport
 Choroid Plexus Cells
 Also Selective
Blood Requirements
 Higher brain can't go more than 5-10 minutes without blood
 Medulla -- cardiovascular and respiratory can go longer
 Babies can go longer without oxygen than Adults
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