01/23/26 - Nervous Tissue part a

the nervous system

various nervous organs throughout the body

• the brain, the spinal cord, the receptors in complex sense organs - such as the eyes and the ears

• the nerves that line it, with the other body systems.

neurons

the basic functional unit of the nervous system, that are specialized for intercellular communication

neuroglia

supporting cells of the nervous tissue

• essential to survival and functionality of neurons and preserving nervous tissue

two divisions of the nervous system

1. the central nervous system (CNS)

2. the peripheral nervous system (PNS)

the central nervous system (CNS)

• consists of brain and spinal cord

• integrating, processing, and coordination sensory data and motor commands

sensory data

convey information about conditions inside or outside the body

motor commands

control or adjust peripheral organs, such as skeletal, cardiac, and smooth muscles, glands, etc

the peripheral nervous system (PNS)

• includes all of the nervous tissue outside the CNS and the ENS (enteric nervous system)

• delivers sensory information to the CNS and carries motor commands to peripheral tissues and systems

nerve fibers

(bundles of axons)

• carry sensory information and motor commands in the PNS

peripheral nerves (or simply nerves)

nerve fibers with associated blood vessels and connective tissues

the functional division (separated functional divisions)

only the PNS has this; the CNS does NOT

afferent division (of the PNS)

brings sensory division to the CNS from receptors in peripheral tissues and organs

receptors

sensory structures that detect changes in the environment

• range from small neurons to organs like the eye/ear

efferent division (of the PNS)

carries commands from the CNS to peripheral tissues such as muscles, glands, and adipose tissue

• has two divisions: somatic and autonomic

the somatic nervous system (SNS)

controls skeletal muscle contractions (voluntary/involuntary)

the autonomic nervous system (ANS)

automatically regulates smooth muscle, cardiac muscle, granular secretions, and adipose tissue at the subconscious level

• includes a parasympathetic division (PANS) and a sympathetic division (SANS)

• also known as visceral motor system

PANS - parasympathetic autonomic nervous system

slows the heart rate

SANS - sympathetic nervous system

accelerates the heart rate

special features of neurons

• having a variety of shapes

• generally long-lined

• generally cannot divide

• high metabolic rate

• an excitable plasma membrane

a typical CNS neuron

has four regions

• a large cell body

• several short, branched dendrites

• a single long axon

• terminal branches of the axon, known as telodendria