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CENTRAL NERVOUS SYSTEM

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KEY CONCEPTSThe nervous system consists of NEURONS which communicate information and GLIA which support and protect the neurons in various ways.

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Nervous System

CNS

PNS

Brain

Spinal CordAfferent

Efferent

AfferentSympathetic

Parasympathetic

Somatic NS

Autonomic NS

Efferent

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THE NERVOUS SYSTEM

A. CENTRAL NERVOUS SYSTEM, consisting of the brain and spinal cord which are responsible for integration.

B. PERIPHERAL NERVOUS SYSTEM which transmits sensory input and executes central commands.

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THE NERVOUS SYSTEM PROTECTION

The central nervous system is PROTECTED by the skull, meninges, and fluid filled cavities containing cerebrospinal fluid.

This fluid originates in the ventricular system of the brain.

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ORGANIZATION OF THE BRAIN

The brain is highly organized with regard to function.

Specific areas of the cerebrum are involved with processing sensory information and motor output.

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ORGANIZATION OF THE BRAIN

Many aspects of the cerebral cortex are mapped for function in a precise manner.

Other parts of the cerebrum modulate motor output from the cerebral cortex while others, such as the limbic system, are involved in mediation of behavior and memory.

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ORGANIZATION OF THE BRAIN

Integration of sensory input and motor output occurs in the brain stem as well.

For example, the midbrain integrates auditory input and motor responses in the eye.

The brain stem also contains specific pathways which move information from the spinal up to the brain and other descending pathways from the brain.

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THE CEREBELLUM

Although THE CEREBELLUM does not initiate motor commands, it is involved in modifying motor commands which arise from the motor cortices of the cerebrum.

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THE SPINAL CORD

THE SPINAL CORD also consists of specific ascending and descending nerve pathways which communicate information between the body and the brain.

This structure is also involved in reflexes which are simple behaviors, such as the withdrawal reflex.

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THE NERVOUS SYSTEM

Some functions of the Nervous System

a. Regulation of physiology b. Sensory input and motor

output c. Emotions, memory,

reasoning, perceptions, etc. 11

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ORGANIZATION OF THE NERVOUS SYSTEM

I. Central Nervous System (CNS)

II. Peripheral Nervous System (PNS)

a. Afferents, interneurons, and efferents.

Tissue Types in the Nervous System 1. Neurons--communication of

information via action potentials 2. Glia--nutrition, support, insulation,

phagocytosis, CSF production, and neural development 12

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PROTECTION AND NOURISHMENT OF THE CNS

CNS is well-protected from internal/external change

1. Blood brain barrier (BBB)--protection from toxins, etc.

2. Skull and vertebrae--protection from physical insults

3. Meninges--nourishment from blood and protection

4. Cerebrospinal Fluid (CSF)13

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FUNCTIONAL ORGANIZATION OF THE BRAIN AND SPINAL CORD

The CNS regulates physiology and is responsible for behavior.

General brain organization. The major division are:

the forebrain, midbrain, and hindbrain 14

11

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FUNCTION

I-CEREBRUM Spatial relationships reflect functional

interaction, e.g.: a) Broca's area is projects to the

premotor cortex b) Wernicke's area receives sensory input

from visual and auditory cortices as well as other brain areas

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The Brain: Form and Function

II- DIENCEPHALON

(THALAMUS AND HYPOTHALAMUS) A. Thalamus is a relay point (ascending

paths) B. Hypothalamus is important in

homeostasis, reproduction, and various behaviors

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The Brain: Form and Function

III-CEREBELLUM Functional organization

1)Vestibulocerebellum (important in balance and eye/ head movements)

2) Spinocerebellum (adjustment of voluntary behaviors, such as walking)

3) Cerebrocerebellum (voluntary behavior; assists in planned movements via the premotor cortex; behaviors that work or don't work)

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The Brain: Form and Function

IV-BRAINSTEM (MIDBRAIN, PONS, AND MEDULLA OBLONGATA)

a. Site of Reticular Activating System (RAS) 1) Affects state of arousal (sleep-wake cycle, hibernation cycle).

b. Midbrain acts as a relay station, as a point of integration for sensory input (=tectum),

and in perception of pain . 18

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The Brain: Form and Function

c. Pons and Medulla -- relay station; site of regulatory centers

d. Cranial nerves *Convey sensory inputs to and motor outputs from the brain

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General organization: Spinal Cord

Spinal cord is also involved in various reflexes

1) Example 1: Withdrawal reflex . 2) Example 2: Crossed-extensor reflex .3) Example 3: Micturition reflex involves control from

higher centers

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