THE CENTRAL NERVOUS SYSTEM Chapter 10

 

 

·       CNS begins as a hollow tube- brain and spinal cord-

hollow; cavities in brain = ventricles 265-270

 

·       Embryonic development:

          Five regions:  telencephalon, diencephalon,

          mesencephalon, metencephalon, myelencephalon

 

1.    Forebrain:  telencephalon and diencephalon

2.    Midbrain:  mesencephalon

3.    Hindbrain:  metencephalon and myelencephalon

 

·       Cerebrum:

          2 hemispheres, outer gray matter- c. Cortex

          inner white

 

          Synaptic potentials within the c. Cortex produce

          the electrical activity= EEG

 

          Specialization of function- cerebral lateralization

 

·       Left hemisphere - dominant in language, and analytical ability

·       Right hemisphere- pattern recognition,

                             musical creation, singing, recognizing faces

·       Communication between the hemisphere-

                             corpus callosum

 

·       Limbic system and hypothalamus- emotion

 

·       Memory- short term vs long term

 

 

 

·       Diencephalon- region of forebrain- thalamus, epithalamus,  hypothalamus and pituitary gland

 

·       Thalamus- relay center for sensory info

·       Epithalamus-  contains choroid plexus- csf

·       Hypothalmus- control of visceral functions;

                   contains centers for thirst, eating, Tb, emotion

                   Also control ant. Pituitary by hormones

 

·       Midbrain- colliculi- involves in auditory and visual reflexes

 

·       Hindbrain- pons and cerebellum, medulla oblongata

 

          Pons- site of origination of some cranial nerves

 

          Cerebellum- control of muscular movement- fine

          motor movement and equilibrium

 

          Medulla oblongata- center for regulation of vital

          functions- breathing, and cardiovascular system

 

 

BRAIN FUNCTIONS

 

·       CEREBRUM - TELENCEPHALON

 

1.  Conscious thought process; intellectual functions

2.  Memory storage and processing

3.  Control of voluntary somatic motor activity

 

·       DIENCEPHLON; THALAMUS

 

Relay and processing center for sensory information

           

·       HYPOTHALAMUS

 

Centers controlling emotions, autonomic functions,

     and hormone production

 

·       MESENCEPHALON; MIDBRAIN

 

1.  Processing of visual and auditory data and control

     of reflexive responses

2.  Maintenance of consciousness

 

·       PONS ;METENCEPHALON

 

1.  Relays sensory information to cerebellum and thalamus

2.  Somatic and visceral motor centers

 

·       MEDULLA OBLONGATA; MYELENCEPHALON

 

1.  Relays sensory information to thalamus

2.  Autonomic centers for regulation of visceral functions such as cardiovascular and digestive activities

                    

·       Spinal cord:

 

Ascending tracts- carry sensory info from sensory organs to the spinal cord, and to the brain

 

Descending tracts- motor tracts

 

·       Cranial nerves- 12 pairs; most are mixed

31 pairs of spinal nerves

 

Dorsal root- sensory fibers; cell bodies -in dorsal root ganglion

 

Ventral root- motor fibers

 

Reflex arc- involves a sensory neuron and a motor neuron.  One or association neurons may be involved

 

Autonomic nervous system 271-274

 

·       Sympathetic Vs parasympathetic- 273

·       Functions

1.    Sympathetic- fight or flight- release of norepinephrine from

 postganglionic fibers, and epinephrine- adrenal medulla

 

2.    Parasympathetic- Ach from postganglionic fibers

                  

·       Action of both- must be balanced to maintain homeostasis

 

·       Organs with dual innervation

         

·       Antagonistic effects-

          1.      pacemaker region of the heart

Adrenergic stimulation- Increases HR ,

Ach- decreases HR

 

2.  GI tract- sympathetic - inhibit intestinal movement and secretion

Parasympathetic-- stimulates movement and secretion

 

·       Complementary- sym and parasym produce similar effects

          e.g. salivary gland secretion; exocrine gland

                   secretion of the digestive tract= parasym

                   Sym- stimulate constriction of blood vessels;

                             the decrease in blood flow to the salivary

                             glands- produce thicker saliva

 

·       Cooperative- synergistic- produce two different

          effects that cooperate to promote a single action

          e.g. urinary and reproductive systems

                   parasympathetic - erection

                   sympathetic - ejaculation

 

·       Organs without dual innervation:

Receive only sympathetic innervation:

          Adrenal medulla

          Arrector pili muscles

          Sweat glands, and

          Most blood vessels

 

·       Control of the autonomic N.S.- by higher brain center

         

          Medulla oblongata of the brain stem directly

                   controls the activity of the ANS

 

·       The medulla is itself responsive to the regulation by

          the hypothalamus - and limbic system