1. Organization of the NERVOUS System
Notes Time!
Organization of the
NERVOUS System

2. Nervous System 3 Basic Functions:
SENSORY Functions: detect stimuli both within and outside of the body. Nerve cells which carry sensory information are called afferent neurons
INTEGRATIVE Functions: analyze info and determine the appropriate response. Nerve cells which carry out this function are called interneurons or association neurons
MOTOR Functions: respond to output from interneurons. Nerve cells which carry out this function are called efferent neurons 2

3. .

4. Nervous System Two main subsystems: CENTRAL NERVOUS SYSTEM (CNS)
Brain & spinal cord
PERIPHERAL NERVOUS SYSTEM (PNS)
All other nervous tissue that is further subdivided:
Somatic nervous system (SNS): motor neurons carry info from CNS to skeletal muscles; axons are well myelinated and conduct impulses rapidly
Enteric nervous system (ENS): “brain of the gut”: control contraction of smooth muscle in GI tract
Autonomic nervous system (ANS): motor neurons carry info from CNS to smooth & cardiac muscle 4

5. Components of AUTONOMIC NERVOUS SYSTEM:
Chain of two motor neurons
Preganglionic neuron
Postganglionic neuron
Conduction is slower due to thinly or
unmyelinated axons
MYELIN: an insulating lipid and protein covering produced by Schwann cells in PNS and Oligodendrocytes (Greek for cells with few branches) in CNS

7. GANGLION: group of nerve cell bodies located outside of the CNS
Tract: bundle of nerve cells inside the CNS

8. Two divisions of AUTONOMIC NERVOUS SYSTEM:
SYMPATHETIC and PARASYMPATHETIC
These two divisions typically work in opposition to one another
Ex: the sympathetic nervous system would increase heart rate in times of stress, and the parasympathetic nervous system would decrease it 8

9. fight-or-flight response Pupils dilate Heart rate increases
SYMPATHETIC activities include body reactions in time of physical or emotional stress
fight-or-flight response
Pupils dilate
Heart rate increases
Airways dilate
Blood is routed away from non-essential organs
Greater blood flow to skeletal muscle
Non-essential processes are inhibited (digestion) 9

10. PARASYMPATHETIC activities include normal body functioning
“rest and digest” functions
“SLUDD”:
Salivation
Lacrimation
(tear production)
Urination
Digestion
Defecation 10

11. Anatomical Differences in Sympathetic and Parasympathetic Divisions
Arise from different regions of the CNS
Sympathetic –
also called the thoracolumbar division
Parasympathetic –
also called the craniosacral division

12. Anatomical Differences in Sympathetic and Parasympathetic Divisions
Length of postganglionic fibers
Sympathetic – long postganglionic fibers
Parasympathetic – short postganglionic fibers
Branching of axons
Sympathetic axons – highly branched
Influences many organs
Parasympathetic axons – few branches
Localized effect

13. Nervous Tissue Two cells types NEURONS: nerve cells
Amitotic- do not divide
Responsible for releasing neurotransmitters and conducting nerve impulses 13

14. Nervous Tissue three parts of a NEURON
cell body: contains nucleus surrounded by cytoplasm with cellular organelles
dendrites: receiving
portion of the neuron. Short and highly branched, arising from the cell body
axon: conducts nerve impulses towards another neuron, muscle cell or gland cell. Long and thin 14

15. Nervous Tissue Neuroglia: 2nd nervous system cell type
support and protect neurons
Much smaller than neurons, but 5-50 times more numerous
Able to divide 15

16. Neuron Function – Nerve Impulses
Some new, some review physiology information in WINGERD questions
(#’s 48 – 72)
Pages 245 – 251 Wingerd text
Pages 222 – 227 your Tortora Text

17. Spinal Reflexes SPINAL REFLEXES
fast, automatic responses to sensory impulses
Autonomic reflexes: involving smooth muscle, cardiac muscle, glands
ex: swallowing
Somatic reflexes: (somatic means body)
involve skeletal muscles
ex: patellar reflex (knee jerk) 17

18. Spinal Reflexes
The pathway followed by nerve impulses producing reflexes is called the REFLEX ARC: 18

19. COMPONENTS OF REFLEX ARC:
Receptor: the distal end of the sensory neuron that responds to a stimulus and generates nerve impulse(s)
Sensory (afferent) neuron: conduct impulse from sensory receptor to the axon terminals
Integrating center: within the spinal cord: synapse between sensory & motor neuron; interneuron/association neuron
Motor (efferent) neuron: carries impulse triggered by integrating center out of the spinal cord and to body
Effector: part of the body responding to the motor nerve impulse; action of the effector is called the reflex 19