biology, great explanation, Schemes and Mind Maps of Remedial Biology

Download biology, great explanation and more Schemes and Mind Maps Remedial Biology in PDF only on Docsity!

BSC 2085 Lab 9

NERVOUS SYSTEM

Hernan Aviles

 ORGANIZATION

 central nervous system (CNS)

 brain and spinal cord  integration and command center

 peripheral nervous system (PNS)

 cranial and spinal nerves  somatic and autonomic  carries messages to and from the spinal cord and brain

 DEVELOPMENT

 begins as a tube (neural

tube)

 cephalic portion: brain

 caudal portion: spinal cord

 Forebrain

 telencephalon (olfactory bulbs, cerebrum, ventricles I, II)  diencephalon (thalamus, hypothalamus, pineal and pituitary glands, optic nerves, III ventricle)

 Midbrain

 mesencephalon

 Hindbrain

 metencephalon (cerebellum, IV ventricle)  myelencephalon (medulla oblongata

 AXONS

 covered by lipid material

( myelin ), myelin is formed by

oligodendrocytes in the CNS and

Schwann cells in the PNS

 Schwann cell spirals repeatedly

around a single nerve fiber (

layers), these layers are the

myelin sheath.

 neurilemma : outermost layer of

a Schwann cell

 endoneurium : thin sleeve

ofconnective tissue surrounded

the schwann cell

 nodes of Ranvier : gaps between

the segments of axons not

covered by myelin

Neuron Model

 NEURON FUNCTIONAL CATEGORIES

 sensory (afferent) neurons : conduct impulses from sensory

receptors to the CNS.

 motor (efferent) neurons : conduct impulses from CNS to effectors

 association neurons (interneurons) : conducts impulses from one

area of CNS to another

 motor and association are multipolar neurons (one axon and

several dendrites)

 sensory are unipolar (one fiber that serves as axon and dendrite)

 bipolar (one axon and one dendrite)

 anaxonic (many dendrites but no axon)

1 Receptor

2 3 4

Sensory neuron Integration center

5 Effector

Motor neuron

Stimulus

Skin

Spinal cord (in cross-section)

Interneuron

 MYELINATED AND UNMYIELINATED NEURONS

 myelinated : organized into bundles called nerve tracts in the

CNS and nerves in the PNS

 myelinated axons form the white matter (myelin is white) and

unmyelinated axons appear gray in color

 sensory nerves contain sensory neurons , motor nerves contain

motor neurons and mixed nerves contain both