Download The Nervous System - OCPS TeacherPress

Purpose of nervous system




maintaining homeostasis using rapid nerve
impulses (action potentials)
movement
memories
behavior
functions:



Sensory function: afferent (sensory) neurons
detect internal and external stimuli and carry
message to brain
Integrative function: processes sensory
information
Motor function: produces a motor response after
processing sensory information. Efferent (motor)
neurons carry information to effectors (muscles
and glands)
Organization of nervous system

2 main subdivisions: central (CNS) – brain
and spinal cord - and peripheral (PNS) –
nervous tissue outside CNS.
Further subdivisions




PNS: somatic (voluntary) nervous system and
autonomic (involuntary) nervous system
Somatic: sensory neurons (to the brain) and
motor neurons (from the brain – cranial and spinal
nerves - to skeletal muscles)
Autonomic: sensory neurons (to brain from
visceral organs) and motor neurons (from brain to
smooth muscle, cardiac muscle, and glands)
Motor part of ANS: sympathetic (“fight or flight”)
and parasympathetic (“rest and digest”)
Peripheral Nervous System
A look at its two branches: somatic
and autonomic
Somatic nervous system

Controls skeletal muscles


Cranial nerves
Spinal nerves/plexuses
Cranial nerves



12 pairs
Assigned roman
numeral (indicate
order from anterior to
posterior) and a name
(designate nerve’s
distribution or function)

Ex: Olfactory (I)
nerve
and
Optic (II) nerve
Spinal nerves/plexuses 


31 pairs
form complex
network of nerves
serving the limbs =
plexus
Important plexuses:
cervical, brachial,
lumbar and sacral

Cervical plexus
Brachial plexus

Important nerves:




Axillary
Median
Ulnar
Radial

Lumbar plexus

Originates L1-L4

Important nerves:



Femoral
Obdurator
Sacral plexus

Originates L4-L5;S1S4

Important nerve:

sciatic
ASSIGNMENT

CREATE A CHART (TREE) THAT
CLASSIFIES ALL THE DIVISIONS OF THE
NERVOUS SYSTEM
Neuron physiology
Neuron physiology

Background:



inactive neuron – polarized (more + in
extracellular space).
Extracellular: mainly Na+
Intracellular: mainly K+

Inactive until excited by stimulus (threshold
= generator potential)



EX. 1: light, sound, touch
EX. 2: neurotransmitters
stimulus causes:



Open Na+ gates
Diffusion of Na+
Charge (polarity) changes – depolarization. A
situation called a graded potential (inside more
positive)



Neuron transmits an action potential (nerve
impulse) – a long distance signal.
Na+ gates close; K+ diffuses out: Returns cells to
beginning electrical conditions (repolarization)
Activation of sodium-potassium pump (uses
ATP)
Propagation of action potential in
neurons with myelin sheaths:

Impulses jump from node to node
Myelin sheath: covering on some neurons that
increases the speed of nerve impulse conductions
Neuron speed related to its
anatomy

Myelin sheath: covering on some neurons
that increases the speed of nerve impulse
conductions


Amount increases from birth to maturity. (a baby
is not as coordinated as adult)
Nodes of Ranvier: gaps in myelin sheath
How neurons transmit a message



Neurotransmitters
Extracellular space: Synaptic cleft
(synapse)
Repeat in subsequent neurons
Reflexes




Rapid, predictable, and involuntary
responses
Occur over neural pathways called reflex
arcs
Types: somatic (stimulate sk. muscles) and
autonomic (smooth muscles, heart, glands)
Indicate health of nervous system
Parts: reflex arc
1.
2.
3.
4.
5.
Sensory receptor –
reacts to stimulus
Sensory neurons:
Integration center:
synapse between
sensory/motor neurons
Motor neurons:
Effector organ –
muscle/gland that
responds (the reflex)
Neurotransmitters





Acetylcholine: excitatory at NMJ
Dopamine: active in emotional responses,
addictive behaviors, pleasurable experiences,
contraction of some sk. muscle
Serotonin: control of mood, appetite, and the
induction of sleep.
Nitric oxide: causes vasodilation. Lowers bp and
causes erection in penis. (viagra enhances the
effect of NO)
Endorphins: natural painkillers, feelings of
euphoria
Modifying the effects of
neurotransmitters

Stimulated or inhibited by drugs.


EX: Parkinson patients take a drug to boost
dopamine production in brain
Botulinum toxin blocks release of acetylcholine

Neurotransmitter receptors can be
activated or blocked.


EX: Isuprel- drug to treat asthma attack – it
binds to receptor and mimics/enhances natural
neurotransmitter effect
Neurotransmitter removal can be
stimulated or inhibited.

EX: cocaine blocks dopamine reuptake

Parkinson's disease: degeneration of
neurons that release dopamine causing
involuntary skeletal muscle contractions