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 Peripheral Nervous System

Brain Spinal Cord

Autonomic Nervous System Somatic Nervous System

Sympathetic Nervous System

Parasympathetic Nervous System

To Smooth muscles

Fight or flight

Non-emergency situations

To skeletal Muscles, exterior sensory organs

Central Nervous SystemCentral Nervous System

Spinal Cord Contains:

1. Central canal filled with cerebrospinal fluid2. Gray matter made up of cell bodies3. 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. Frontal Lobe- Conscious thought 2.  Temporal Lobe – Hearing and smelling 3.  Parietal Lobe – Temperature,Touch and Pain 4.  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 Peripheral Nervous System  Brain Spinal Cord 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 SystemTwo Divisions:

1. Sympathetic2. Parasympathetic

Both: Function automatically (involuntary) Serve all internal organsHave 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 - Short preganglionic fiber,postganglionic fiber long postaganglionic fiber -Ganglion near organ -Ganglion near spinal cord -Nerves arise from top and bottom of -Nerves arise from middle spinal cord of spinal cord.

Use pages 336 and 337 to help!

Bases ofComparison

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 

Location of motor ganglion

Monoamine oxidase 

Closer to CNS

Acetylcholinesterase 

Farther from the CNS

Fight or FlightAdrenal 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. Increase heart rate so that more blood is

supplied to the body more quickly.

3. Widen air passageways so that more air can be exchanged with each breath.

4. 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.

5. The iris of the eye contracts thus widening the pupil to maximize visual alertness.

6. Increased blood flow to the skeletal muscles so they are more able to act.

7. 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

DHypothalamus 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?