Download Divisions of the Nervous System

Human Biology: Nervous System
Lesson 2: Divisions of the Nervous System
(Inquiry into Life pg. 326-337)
Today’s Objectives

Analyse the functional inter-relationships of the divisions of the
nervous system, including:
 Compare the locations and functions of the CNS and PNS
 Identify and give functions for the following parts of the brain:
medulla oblongata, cerebrum, thalamus, cerebellum,
hypothalamus, pituitary gland, corpus callosum, meninges
 Explain how the hypothalamus and pituitary gland interact as the
neuroendocrine control center
 Differentiate between functions of the autonomic and somatic
nervous systems
 Describe the inter-related functions of the sympathetic and
parasympathetic divisions of the autonomic nervous system
 Identify the source gland for adrenalin (adrenal medulla) and
explain its role in the “fight or flight” response
Nervous System
Central Nervous System
Brain
Peripheral Nervous System
Spinal Cord
Autonomic Nervous System
Somatic Nervous System
To skeletal Muscles,
exterior sensory
organs
Parasympathetic Nervous System
To Smooth muscles
Sympathetic Nervous System
Fight or flight
Nonemergency
situations
Central Nervous System
Spinal Cord Contains:
1. Central canal filled with cerebrospinal fluid
2. Gray matter made up of cell bodies
3. White matter made of long fibers of interneurons.
They are white because they are
covered by myelin sheath.
The dorsal (back)
part of the cord is
specialized to carry
sensory information
to the brain.
The ventral (front)
part of the cord
sends messages from
the brain to the
body.
Interneuron fibers run together in parallel bundles called
tracts.
Left and right tracts crossover prior to entering the brain.
Therefore, left side of the brain controls right side of the
body and vice versa.
Brain:
Medulla Oblongata
-Brain Stem (bottom of the brain)
-Pathway between brain and spinal cord
-Controls involuntary reactions:Vomiting,
coughing, sneezing,hiccuping, swallowing.
-Controls: Heartbeat rate, breathing, and
blood pressure.
Cerebellum
-Butterfly shaped
-Rear, lower portion of the brain
-Second largest portion of the brain
-Controls: Muscle co-ordination (smooth
graceful motions) muscle tone, balance and
posture.
Hypothalamus
-Located just above the pituitary gland.
-Controls: The pituitary gland and production of hormones,
hunger, thirst, sleep, body temp, water balance
Maintains homeostasis (balanced equilibrium) by controlling
endocrine system: system of glands which release hormones
Thalamus
-Above the hypothalamus
-Controls: Relay station for information going
to the cerebrum. (like a circuit board for the brain)
Channels info to appropriate place and prevents sensory
overload.
Cerebrum
-Largest part of the brain
-Controls: Conscious thought
Perceives sensory information
Initiates movements
-Contains 2 hemispheres (Right and left)
-Memory
Parts:
1.
2.
3.
4.
Frontal Lobe- Conscious thought
Temporal Lobe – Hearing and smelling
Parietal Lobe – Temperature,Touch and Pain
Occipital Lobe – Vision
** See Diagram In student Notes**
Corpus Callosum
-Holds the hemispheres of the
Cerebrum together
-Conducts impulses from one side of
the brain to the other.
The CNS is comprised of the brain and the spinal cord.
Nervous System
Central Nervous System
Brain
Spinal Cord
Peripheral Nervous System
Somatic
Autonomic
Parasympathetic Sympathetic
Peripheral Nervous System (PNS)

The PNS is made up of nerves, which are either part of the
Somatic or the Autonomic Nervous System.

Somatic:


contains nerves that control skeletal muscles, joints, and
skin. They receive and act on external stimuli.
Voluntary Control
Autonomic:



contains nerves that control the smooth muscles of the
internal organs and the glands.
Automatic, usually without the need for conscious
thought.
Peripheral Nervous System

Consists of all nerves projecting from the brain and
spinal cord.

Nerves are bundles of neuron fibers






Sensory Nerves: Bundles of dendrites from sensory neurons.
Motor Nerves: Bundles of axons from motor neurons.
Mixed Nerves: Dendrites of sensory neurons and axons of
motor neurons running together.
Cranial Nerves: Arise from Brain
Spinal Nerves: Arise from the spinal cord
Ganglion: A collection of cell bodies from many neurons.
Appears as an enlarged portion of the nerve.
Divisions of the Autonomic Nervous System
Two Divisions:
1. Sympathetic
2. Parasympathetic
Both: Function automatically (involuntary)
Serve all internal organs
Have two motor neurons with a ganglion between
Differences
Parasympathetic
Sympathetic
-Normal activity (“Rest and Digest”)
-”Fight or flight”
Decrease blood flow to the
digestive system
-Neurotransmitter is Acetylcholine
-Neurotransmitter is Noradrenalin
-Long preganglionic fiber, short
postganglionic fiber
- Short preganglionic fiber,
long postaganglionic fiber
-Ganglion near organ
-Ganglion near spinal cord
-Nerves arise from top and bottom of
spinal cord
-Nerves arise from middle
of spinal cord.
Use pages 336 and 337 to help!
Bases of
Comparison
Sympathetic
Neurons
Parasympathetic Neurons
Effect
Active body function
“fight or flight”
Normal activity
“rest and digest”
Spinal origin
Thoracic and lumbar
Cranial (cervical) and sacral
Neurotransmitter
Noradrenalin
Acetylcholine
Restoring enzyme
Monoamine oxidase
Acetylcholinesterase
Location of motor ganglion
Closer to CNS
Farther from the CNS
Fight or Flight
Adrenal Glands
 Sudden simultaneous release
of noradrenalin from all the
sympathetic neurons (as in
times of fright) has a critical
effect.
It causes the release of the hormone
adrenalin from the interior of the adrenal
glands located on top of the kidneys.
The noradrenalin and the adrenalin
initiate and sustain what is known as the
‘Fight or Flight” response.
They prepare the body to respond to danger
in the following ways:
2.
3.
4.
5.
6.
7.
Increase heart rate so that more blood is supplied to the
body more quickly.
Widen air passageways so that more air can be exchanged
with each breath.
Sudden contraction of some muscles to tense the body up
for action. Included in this is the contraction of the
diaphragm. A scared person will gasp, inhaling suddenly.
The iris of the eye contracts thus widening the pupil to
maximize visual alertness.
Increased blood flow to the skeletal muscles so they are
more able to act.
Decreased digestive activity, circulation and control.
Neuroendocrine Control




There is an association between nerve tissue and the body’s
hormones (endocrine = hormonal).
This association is between the hypothalamus and the
pituitary gland.
It can be seen that there are two lobes of the pituitary gland:
an anterior and a posterior lobe.
Both of these extend down from the hypothalamus.
As blood passes through the hypothalamus , its
composition and temperature stimulate various
homeostatic responses.
Those responses involve the release of hormones.
The anterior pituitary releases six major hormones that
range in effect from bringing about reproductive changes to
skeletal growth.
The posterior pituitary releases two hormones.

The mechanism of action is slightly different for the
release of the anterior pituitary hormones than it is for
the posterior pituitary hormones.

In the case where the hypothalamus detects that the
effect of one of the hormones from the anterior
pituitary is required, it releases a hormone-like
substance called a releasing factor that travels through
the very short blood vessel that is connected with the
anterior pituitary.
The effect of this is to cause the release of the required hormone.
In the case of the hormones released by the posterior pituitary,
the hypothalamus actually makes these hormones which it
releases into a nerve tract that conducts them to the posterior
pituitary gland.
Regardless of the mechanism all the hormones are released into
the circulatory system and they travel about the body affecting
the specific target organs for which they were designed.

Quick Review Questions
C
D
B
A
B
B
D
D
Hypothalamus would NOT make ADH (antidiuretic hormone) and would
NOT send it to the posterior pituitary gland. ADH would NOT be released
which would cause the collecting duct in the nephron in the kidneys to be
relatively impermeable to water. The urine would be more dilute and less
water would be taken back into the body.
Did I trick anyone? … haha? 