Resumen

I . OVERVIEW OF THE NERVOUS SYSTEM


nervous system = controls and integrates the functional activities of the organs and organ systems


anatomical division of nervous system:

a) central nervous system ( CNS ) = brain (in cranial cavity) and spinal cord ( in spinal canal )


b) peripheral nervous system ( PNS)1. cranial, spinal and peripheral nerves – conduct impulses from ( efferent or motor nerves ) and to (afferent or sensory nerves ) the CNS
2. ganglia - nerve cell bodies outside the CNS
3. specialized nerve endings



* Not protected by organs or by blood-brain barrier leaving it exposed to toxins and mechanical injuries
* *afferent nerves = nerves that conduct signals from sensory neurons to CNS
* efferent nerves = conduct signals from the CNS along motor neurons to their target muscle and glands



Functional division of nervous system:


a) somatic nervous system (SNS)– somatic parts of the CNS and PNS that provides sensory and motor innervations to allparts of the body except: viscera, smooth muscle and glands

* consist of efferent nerves responsible of stimulating muscle contraction including all the non-sensory neurons connected with skeletal muscles and skin
* associated with voluntary control of body movements via skeletal muscles

b) autonomic nervous system (ANS) – autonomic parts of CNS and PNS thatregulate functions of internal organs.
* Acts as control system, functioning largely below the level of consciousness and control visceral functions
* Affects : heart rate, digestion, respiratory rate, salivation, perspiration, pupilary dilation, sexual arousal, mieturium(urination)


1. There is cooperation between nervous and endocrine system2. It provides efferent involuntary motor innervations to

Smooth muscle – can change diameter & shape of tubular and hollow viscera: blood vessels, gut, gall bladder, urinary bladder
Cardiac conducting cell (Purkinje cells)
Glands

3. it provides afferent sensory innervation from : viscera ( pain andautonomic reflexes)
4. divided as:
Symphatetic
* Function in actions which require quick responses
* General action is to mobilize body’s nervous system fight-or-flight response
Parasymphatetic
* Usually work to promote mainteinance of body at rest
*Function in actions that don’t requireimmediate action
*Responsible for stimulation of rest and digest activities: salivation, sexual arousal, lacrimation,urination, defecation, digestion

Enteric (serves alimentary canal)
* Can be independent of the other two



II. COMPOSITION OF NERVE TISSUE



2 types of cells innerve tissue : Neuron (nerve cell)
Supporting cells

Neuron : cell body
processes ( axon and dendrites )
synapses

a) structural and functional unit of nervous system

b) specialized to receive stimuli from other cells and to conduct electrical impulses to other partsof the system via the processes

c) in human – about 10 billion neuron
d) neuron = nerve ( enclosed cable-like bundle of peripheral axons in the PNS)
* Many neurons do not form nerves and nerves include non-neuronal cells





Supporting cells – non conducting cells in intimate apposition with...