Introduction to Nervous System - Nervous Tissue etc.

Co-Ordination

• the way the organs and systems of the body are made to work together to respond to any change detected inside or outside the body

common factors between endocrine system and nervous system

both start off with a stimulus and produce a response

differentiating factors between nervous and endocrine system

NERVOUS SYSTEM	ENDOCRINE SYSTEM
messages - electrical signals	hormones
fast acting	slow acting
localized response	response may affect several target organs at once
response is immediate	response is delayed
response produces a short-term change	Reponses produce a long term change

neurons

• carry messages by electrical impulses

glial cells

non-neuronal cells that provide support and protection for the neurons

3 types of neurons

• sensory/Afferent

• intermediate

• motor / Efferent

Sensory Neuron

• carry impulses from receptor towards central nervous system

• long dendron and short axon

• cell body is always located in the dorsal root ganglion

Relay Neuron

• connects sensory and motor neuron

Motor Neuron

• carries impulses away from the CNS to an effector which brings about a response

• short dendrites as it would be receiving signals from close neurons in the CNS, then has a long axon to transmit them to nearby effector muscles

each neuron consists of

• cell body

• dendrons

• axon

cell body

• contains nucleus and other organelles

• controls cells metabolic activity

• many cell bodies for a ganglion

dendron

• carry signal towards cell body

• many branches of dendrites which increase surface area to receive signals more efficiently

axon

• carries signals away from cell body

• synaptic knob - terminal region of axon.

• communicates via synapses

myelinated nerve fibers

• made of lipids

• formed by Schwann cells

• neurilemma which is a tough inelastic membrane surround the myelin sheath

• allows for fast transmission of impulses

Nodes of Ranvier

• where the myelin sheath is constricted

• impulses are generated here

  • only present in myelinated cells

Non-myelinated nerve fibres

• slower rate of conduction

• no nodes of ranvier

• autonomic nerves