Download The Nervous and Endocrine Systems

Module C: Unit 1, Lesson 5 – The Nervous and Endocrine Systems
What is the function of the nervous system?
• The nervous system is made up of the structures that control actions and
reactions of the body in response to stimuli in the environment.
• The nervous system has two parts: the central nervous system (CNS) and the
peripheral nervous system (PNS).
• The CNS is made up of the brain and spinal cord.
• The brain is the body’s central command organ.
• The spinal cord allows the brain to communicate with the rest of the body.
• The PNS connects the CNS to the rest of the body.
• Involuntary processes are those you have no control over, such as your heart
beating.
• Voluntary processes are actions your brain can control, such as moving an arm or
a leg.
What are the parts of the CNS?
• The CNS is made up of the brain and the spinal cord.
• The cerebrum is the largest part of the brain. It is where you think, solve
problems, and store memories.
• The cerebrum controls voluntary movements and processes information from
your senses.
• The cerebellum processes information from your body, keeps track of body
position, and coordinates movements.
• The brain stem connects your brain to the spinal cord.
• A part of the brain stem called the medulla controls involuntary processes in the
body.
• The spinal cord is a bundle of nerves protected by bones called vertebrae.
• Nerves are a collection of nerve-cell extensions bundled together with blood
vessels and connective tissue.
• The spinal cord carries messages to and from the brain.
How do signals move through the nervous system?
• The nervous system translates environmental information into electrical signals.
• A neuron is a special cell that moves messages in the form of fast-moving
electrical energy.
• These messages are called impulses.
• Signals move through the CNS and PNS with the help of glial cells that protect
and support neurons.
• Sensory neurons gather information from in and around your body and move it to
the brain.
• Motor neurons move impulses from the brain and spinal cord to other parts of the
body.
What are the parts of a neuron?
• The cell body of a neuron has a nucleus and organelles.
• A dendrite is a typically short, branched extension of the cell body.
• The cell body gathers information from dendrites and creates an impulse.
• An axon is an extension of the neuron that carries impulses away from the cell
body.
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A neuron has only one axon.
At the end of the axon is the axon terminal that changes the electrical signal to a
chemical signal, or neurotransmitter.
What are the main senses?
• The sensory organs sense the environment around you.
• Sight allows you to see objects, motion, and light.
• The front of the eye is protected by a membrane called the cornea.
• Light passes through an opening called the pupil.
• Light-sensitive receptor cells, called rods and cones, in the retina change light
into electrical impulses that are sent to the brain.
• Impulses travel to your brain, creating an awareness of touch called a sensation.
• The skin has different kinds of receptors that detect pressure, temperature, pain,
and vibration.
• Hearing happens when sound-wave vibrations are turned into electrical impulses
in the ear.
• Sound is funnelled through the outer ear, making the eardrum vibrate.
• Tiny bones in the ear vibrate, causing the fluid in the cochlea to move in waves.
• Hair cells in the fluid cause neurons to send electrical impulses to the brain via
the auditory nerve.
• The tongue is covered with taste buds that contain taste cells. They respond to
signals in dissolved molecules in food.
• Olfactory cells react to chemicals in the air that dissolve in the lining of the nasel
cavity, triggering signals.
• The nose sends signals to the brain for processing taste and smell.
What is the function of the endocrine system?
• The endocrine system controls body functions and helps maintain homeostasis
by using hormones.
• A hormone is a chemical messenger made in one cell or tissue that causes a
change in another cell or tissue elsewhere in the body.
How do hormones work?
• Hormones are produced by endocrine glands or tissues and travel through the
bloodstream.
• A gland is a group of cells that make special chemicals in your body.
• Hormones only affect specific target cells that have a specific receptor to that
hormone.
What glands make up the endocrine system?
• The pituitary gland secretes hormones that control other glands.
• The hypothalamus controls the release of hormones from the pituitary gland.
• The pineal gland makes hormones that control sleep, aging, reproduction, and
body temperature.
• The thyroid gland controls metabolism.
• The parathyroid gland controls calcium in the blood.
• Reproductive hormones control reproduction.
• The pancreas regulates blood-sugar levels.
How are hormone levels controlled?
• The endocrine system helps maintain homeostasis by increasing or decreasing
hormone levels.
• The endocrine system uses feedback to maintain homeostasis.
• A feedback mechanism is a cycle of events in which information from one step
controls or affects a previous step.
• In negative feedback, the effects of a hormone cause the release of that hormone
to be turned down.
• In positive feedback, the effects of a hormone stimulate the release of more of that
hormone.
What are disorders of the endocrine and nervous systems?
• Hormone imbalances can happen when the endocrine system makes too much or
too little of a hormone.
• Type 1 diabetes is caused by a hormone imbalance.
• Parkinson’s disease, multiple sclerosis, and spinal-cord injuries are disorders of
the nervous system.