Transcript Human Nervous System - Valhalla High School

Human Regulation
Coordination and Control
Regulation in Humans
• Controlled by 2 systems
– Nervous System - electrical
– Endocrine System – chemical
• Both systems respond to and send
messages throughout the body
Human Nervous System
Central and
Peripheral
A General
Sense…
An Overview of the
Nervous System:
Peripheral Nervous
System
Central Nervous
System
-Brain
-Spinal Cord
Sensory Neurons
-carry messages
towards spinal cord
from sensory receptors
Somatic System:
Voluntary Nerves
--neurons control
skeletal muscles
Sympathetic Division
--“fight or flight”
--activated by stress
Motor Neurons
-carry signals
away from CNS
Autonomic System:
Visceral, Involuntary
--heart, blood vessels,
digestive organs,
smooth muscle
Parasympathetic
Division:
--Routine
Nervous System Cells
• Called neurons
• Neurons have long axons that enable
them to transmit signals. Many neurons
together are called a nerve.
• Each nerve has a dorsal root (info coming
into the CNS) and a ventral root (info
going out from CNS to body).
Anatomy of a Neuron
• Cell body – main part
• Dendrite – receives stimulus from other neurons
• Axon – branches from cell body, sends the signal
out
• Myelin sheath – lipid layer for protection over
neurons that allows for increase in speed of
signal transmission
• Synapse – gap between neurons; between the
axon terminal of 1 neuron and the dendrite of a
2nd neuron
Anatomy of a Neuron
Central Nervous System (CNS)
BRAIN
• About 1.4 kg, 2% of body weight
• About 100 billion neurons
• 12 pairs of cranial nerves are connected to
the human brain
– Example: Pupil reflex in response to bright
light, to avoid damage to retina. Nerves that
control this reflex are connected to the brain.
• Starts at the
medulla oblongata
(in the brain)
• 31 pairs of spinal
nerves branch out
to the body
• Spinal Reflexes:
these don’t go to
the brain, instead
they go to the
spinal cord—
– Ex. patellar reflex
Spinal Cord
Reflexes
• An automatic reaction to some sense
message, like pain
– Don’t need to think or make decisions about
something
• The information gets processed in your
spinal cord
– Your muscles begin to react immediately even
before your brain gets the news of what’s
happening.
– This is called a reflex arc
Reflex Arc
• Begins at a receptor
– Sensory neurons in the skin receive a
stimulus
• Travels to the reflex center (spinal cord)
• Ends at an effector
– A muscle or gland that reacts to the stimulus
Reflex Arc
A pathway of nerve impulses
1. Stimulus – a change in the environment that causes
a change in the body
2. Receptor – specialized organ that receives the
stimulus
3. Sensory neuron – brings the stimulus to the spinal
cord
4. Synapse – space between neurons
5. Interneuron – neurons in the spinal cord
6. Motor neuron – brings the stimulus from the spinal
cord to the correct part of the body
7. Effector – muscle or gland that reacts to the
stimulus
The Patellar Reflex
Peripheral Nervous System
(Motor and Sensory)
Motor Division: signals away from CNS
• Somatic nervous system is for voluntary
muscle control. These neurons control the
skeletal muscles….
• Autonomic nervous system is automatic or
involuntary
– Control of heart rate, respiration, blood
pressure, smooth muscle, etc.
– This has 2 separate divisions: sympathetic
and parasympathetic
Autonomic: Sympathetic Division &
Parasympathetic Division
• Sympathetic: Shunting of blood from one
part of body (ex = stomach to heart) to
another. Activated by physical or
emotional stress. “Fight or Flight”
response.
• Parasympathetic: Routine life, conserves
energy, heart rate lowers, digestive organs
back to normal. “Rest and Ruminate”
response.
Autonomic NS: Parasympathetic and Sympathetic Controls
Peripheral Nervous System
Sensory Division
• Sensory neurons carry messages toward
the CNS from sensory receptors all over
body.
• Sensory receptors are in sense organs,
such as eyes, ears, mouth, nose, skin…
and different regions of the brain respond
to different signals.
Transmission of neural signals:
How it Works…
• In general, the signaling activity of the
nervous system is composed of electrical
activity within neurons and chemical flow
between neurons. Quite a complex
network!
• 200 years ago… found out that a recently
dead animal will still contract muscles if an
electrical stimulation is sent through.
The Endocrine
System
Endocrine System
• A set of glands that produce
hormones-- chemical messengers
that circulate in the blood
Hormone
• Chemical messengers produced by
the endocrine glands and circulated
in the blood
• Similar to neurotransmitters in that
they are also messengers
• Slower communication system, but
with longer lasting effects
Endocrine System
Hypothalamus
• Brain region that controls the
pituitary gland
• Controls homeostasis – the
bodies ability to remain at a status
quo level
Pituitary Gland
• The endocrine system’s gland that controls the other
endocrine glands
• Called the “master gland”
• Located at the base of the brain and connects to the
hypothalamus
• Controls thirst by controlling the amount of water in
the body’s cells
• Controls female contractions, and tells the mammary
glands to produce milk for newborns
• May control grooming habits, companionship, and
sexual behavior
• Controls the flow of the human growth hormones –
dwarfism and gigantism
Thyroid Gland
• Endocrine gland that helps regulate the energy level
in the body
• Located in the neck
• controls body temperature
• Controls metabolism – our body’s ability to
transform the food we eat into usable energy
• Overactive- Behaviors may include excitability,
insomnia, ADD, agitation, difficulty focusing
• Reduced Activity- Behaviors may include
sleepiness, reduced muscle tone, overweight
Adrenal Gland
• Endocrine glands that help to arouse
the body in times of stress
• Located just above the kidneys
• Release epinephrine (adrenaline)
and norepinephrine (noradrenaline)
• Increase heart rate, blood pressure,
and blood sugar
Pancreatic Gland
• Regulates the level of blood sugar
(insulin) in the blood
• Insulin is needed in the body to break
down sugars in the body
• Too much insulin in the body devours
all of the sugar in the blood. Behaviors
exhibited include sluggishness and
inattentiveness.
• Too little insulin causes a buildup of
sugar in the blood and makes the
kidneys use a lot more water to flush
it out of the body. The extra water
needed to flush the sugar comes from
surrounding cells, which in turn
dehydrates them and leaves them
vulnerable to infection and poisons.
Sex Glands
• Ovaries (females) and testes (males) are
the glands that influence emotion and
physical development.
• Testosterone – primary male hormone
• Estrogen – primary female hormone
• Males and females have both estrogen
and testosterone in their systems.
Gonads
• Testicles – release androgens (male
hormones)
• Ovaries – release estrogens (female
hormones)
• The presence of these chemicals
influence male and female
reproductive characteristics.
Maintaining Homeostasis
• Homeostasis is the maintenance of a
stable internal state within an organism.
• Organisms detect changes in their
environment and respond to these
changes in a variety of ways.
• A feedback mechanism occurs when the
level of one substance influences the level
of another substance or activity of another
organ.
Feedback Mechanisms
Three parts of the mechanism
– Sensor – something that can detect a change
• Ex. Structures in the brain detect change in CO2 levels
– Control Unit – something that knows what the correct
level should be
• Ex. Information in the brain is preset for the correct CO2 level
– Effector – something to take the instructions and
make changes
• Ex. Muscles in the chest used for breathing
Feedback Mechanisms
• Positive feedback - designed to accelerate or enhance
the output created by a stimulus that has already been
activated.
• Designed to push levels out of normal ranges.
• Example is the release of oxytocin to intensify the
contractions that take place during childbirth.
– The more oxytocin, the greater and more frequent the
contractions, which in turn produces more oxytocin
Feedback Mechanisms
• Negative feedback – process in which a stimulus produces a
response that opposes the original stimulus.
• Ex. Blood sugar regulation
– An increase in blood sugar level triggers the release of the hormone
insulin by the pancreas
– the hormone insulin lowers blood sugar level restoring the body to its
original blood glucose level in two major ways:
• it increases the ability of body cells to take in glucose from the blood
• it converts blood glucose to the compound glycogen -- this compound is
also called animal starch and is stored in our liver and muscles
– A decrease in blood sugar levels triggers the release of the hormone
glucagon by the pancreas
• It causes the liver to release glucose into the blood to regulate blood sugar
levels
Regulation Disorders
• Nervous System
– Cerebral Palsy – affect the ability to control body
movements
– Alzheimer’s – progressive degenerative disease;
lose memory and ability to think, speak, etc.
– Multiple Sclerosis – cells in the brain and spinal
cord do not function normally.
• Wide variety of symptoms
Regulation Disorders
• Endocrine System
– Diabetes – interruption of the feedback
system that controls blood sugar.
– Type I – born with it
• Controlled by insulin injections
– Type II – acquired
• Usually occurs in older people
• May be controlled with diet