Download REGULATION

REGULATION
Part I
Nervous Regulation
(the nervous system)
I. Regulation
is the life function by which organisms coordinate and
control of their own life activities to maintain life.
Regulation includes both nerve control (animals only) &
chemical control (all organisms).
A. Nerve controlnerve control depends mainly on the functioning of the
neurons (nerve cells).
1. Stimulus
is any change that occurs in the external or internal
environment of an organism that initiates an impulse.
Ex) light, sound & chemical change
2. Impulse
an electro-chemical charge generated along a neuron
3. Response is a reaction to a stimulus
a. Receptors
- structures specialized to detect only 1 type of stimuli
ex.) Eye for light, ears for sound, skin for touch, nose for
smell, tongue for taste
b. Effectors
- organs of response such as muscles or glands
Basic Sequence of Events
1. Stimulus activates a receptor
2. Receptor triggers impulse in a nerve pathway
3. Impulse is received by effector that responds
B. Structure of NEURON
A cell specialized for the transmission of nerve impulses from
place to place in the body. It is composed of:
1) DENDRITES
fibers that detect the stimulus and generate impulses
toward the cyton.
2) CYTON
cell body containing the nucleus.
3) AXON- a fiber that transmits the impulse away from the cyton
toward the terminal branches
4) MYELIN SHEATH
layers of white, fatty substances produced by Schwann
cells that surround some axons
5) TERMINAL BRANCHES
- ends of the axons which secrete neurotransmitters (consists
of synaptic knobs)
C. Synapse
is a junction between adjacent neurons or between neuron and
effector
D. Neurotransmitters
are special chemicals, produced and secreted by the neuron's
synaptic knob (located at a terminal branch) that serves to
carry impulses from 1 neuron to the next.
ex) acetylcholine
E. Types of Neurons
(nerve cells) nerves are bundles of axons or dendrites that are
bound together by connective tissue.
1. Sensory Neurons
carry impulses from receptors toward the spinal cord
and brain (longest)
2. Interneurons
-(also called associative neurons) carry impulses from
one neuron to another in the brain and spinal cord
(short)
3. Motor Neurons
- carry impulses from the brain and spinal cord to the
effectors.
How a Nerve Impulse is sent through a neuron...
II. Resting Neuron
A. Transmission of nerve impulse is made possible by a
difference in electrical charge between the outer (+) and
inner (-) nerve cell membrane.
III. Nerve Impulse
A. As an impulse is carried in a neuron, there is a reversal of
polarity (the outside becomes negative and the inside becomes
positive.)
B. This reversal of polarity occurs in a small area of the
membrane where the impulse is.
C. Once the impulse passes, ions pass from the inside back to
the outside and the polarity is returned back to that of the
resting neuron.
IV. Transmission at the synapse
A. During impulse (electrical energy), a neurotransmitter,
acetylcholine and norepinephrine, is released into the
synaptic cleft (space between 2 neurons).
B. The electrical impulse is now converted into a
chemical response that stimulates the adjoining neuron
to receive the transmitted impulse.
C. Once the impulse has been transmitted, cholinesterase
break down the acetylcholine to clear the way for new signals.
Human- the human central nervous system consists of a
highly developed brain and dorsal nerve cord (found in
all chordates) that permit impulses to travel over definite
pathways.
There is also many highly developed receptors.
One disease (caused by a virus) associated with the destruction
of nerve cells is polio.
I. CENTRAL NERVOUS SYSTEM (CNS):
-made up of brain & spinal cord which are protected by
cranium & vertebrae
-also protected by:
1) meninges- 3 tough membranes that enclose & protect
brain + spinal cord
2) cerebral spinal fluid- liquid that cushions nervous tissue
from shock and fills space between meninges, in ventricles (4
spaces with in brain),& in spinal canal of spinal cord
A. BRAIN
1. receives 20% of blood from the heart (glucose is the
major energy source)
2. has 3 divisions, each having specialized functions
a. Cerebrum- largest part (2/3 of brain); center of
intelligence & awareness; controls thought, memory,
learning, emotions, seeing, hearing, taste, smell, touch
-these are examples of voluntary movements
b. Cerebellum- controls balance & muscular behavior
c. Medulla- controls breathing, heartbeat, digestive tract
movements; gland secretions, coughing, sneezing,
swallowing, vomiting
-these are examples of involuntary movements
CEREBRAL CORTEX(outermost layer) has 3 functions
1. sensory areas
-receives and interprets impulses from sense receptors
2. motor areas- initiates impulses for all voluntary movement
3. associative areas
- responsible for memory, learning, and thought
B. SPINAL CORD
1. lies within the column of the vertebrae that is
continuous with the brain.
2. inner layer of cord has "H" shaped gray matter and
white matter surrounding it
3. it has two main functions
a. connecting brain to the peripheral nerves
b. controls reflexes
Receptor
-->
Sensory
-->
Interneuron
-->
motor
a. Reflexes- involuntary, automatic responses to a given
stimulus (no brain involvement) ex.) knee jerk,
withdrawal reflexes
b. instincts- complex inborn behavior patterns consisting of
senses or a chain of reflexes ex.) building a nest, spinning a
web
II. PERIPHERAL NERVOUS SYSTEM
{located outside CNS}
-cranial nerves (nerves connect to the brain; 12 pairs)
-spinal nerves (nerves that connect to the spinal cord; 31
pairs)
-it consists of 2 specialized nervous systems
A. Somatic Nervous System
controls voluntary muscles
1. consists of sensory & motor neurons
B. Autonomic Nervous System
made of nerves that control cardiac muscle, glands &
smooth muscle. It coordinates involuntary actions.
-consists of motor neurons
1) Parasympathetic Nervous System
2) Sympathetic Nervous System
-both parts of the autonomic nervous. system. are
antagonistic to each other
III. Some ANOMALIES of the Nervous System
A. Cerebral Palsy
A congenial (existing at birth but not hereditary) disease characterized by
a disturbance of the motor functions.
B. Meningitis
- inflammation of the membranes surrounding the brain & the spinal
cord.
C. StrokeA disease resulting from a cerebral hemorrhage or a blood clot in the
cerebral vessel which may result in brain damage.
D. Polio
- A viral disease of the CNS which may result in Paralysis and is
preventable through immunization.
E. Rabies- A contagious infection of the CNS, caused by specific virus
that enters the body through the bite of an animal.