29.1 How Organ Systems Communicate
KEY CONCEPT The nervous system and the endocrine system provide the means by which organ systems communicate.
29.1 How Organ Systems Communicate
The body’s communication systems help maintain homeostasis.
• A stimulus causes a response.– Responses can be chemical, cellular, or behavioral. – The nervous and endocrine systems respond to stimuli.
29.1 How Organ Systems Communicate
• The nervous system controls thoughts, movement, and emotion.
• The endocrine system controls growth, development, and digestion.
29.1 How Organ Systems Communicate
The nervous and endocrine systems have different methods and rates of communication.
• The nervous system works quickly, using chemical and electrical signals.
spinal chord
nerves
– interconnected network of cells– signals move through cells – divided into central nervous system (CNS) and peripheral nervous system (PNS)
29.1 How Organ Systems Communicate
• The endocrine system works more slowly.
– only chemical signals– signals move through bloodstream – physically unconnected organs
receptor
target cell
not a target cell
bloodstream
hormone
29.1 How Organ Systems Communicate
KEY CONCEPT 29.2The nervous system is composed of highly specialized cells.
29.1 How Organ Systems Communicate
Neurons are highly specialized cells.
• A neuron has three parts.– cell body has nucleus and organelles
1 Cell body
29.1 How Organ Systems Communicate
– dendrites receive impulses
Neurons are highly specialized cells.
• A neuron has three parts.– cell body has nucleus and organelles
2 dendrites
29.1 How Organ Systems Communicate
– axon carries impulses
3 axon
– dendrites receive impulses
Neurons are highly specialized cells.
• A neuron has three parts.– cell body has nucleus and organelles
29.1 How Organ Systems Communicate
• Neurons have other structures to transmit signals.
– Schwann cell
29.1 How Organ Systems Communicate
– synapse
synapse
• Neurons have other structures to transmit signals.
– Schwann cell
29.1 How Organ Systems Communicate
– terminal
– synapse
• Neurons have other structures to transmit signals.
– Schwann cell
axon terminal
29.1 How Organ Systems Communicate
Neurons receive and transmit signals.
• Resting potential means no signal is being transmitted. – more Na+ outside of cell – more K+ inside of cell
29.1 How Organ Systems Communicate
• An action potential is a moving electrical impulse.
– It is generated by a stimulus.– Na+ enters, and cell becomes
positively charged.– K+ leaves, and area of positive
charge moves.
area of detail
29.1 How Organ Systems Communicate
• A chemical signal passes between neurons.
– Impulse reaches terminal.
impulse
29.1 How Organ Systems Communicate
• A chemical signal passes between neurons.
– Impulse reaches terminal.
impulse
29.1 How Organ Systems Communicate
• A chemical signal passes between neurons.
– Impulse reaches terminal.
synapse
receptorvesicles
impulse
neurotransmitter
– Neurotransmitters released into synapse.
29.1 How Organ Systems Communicate
• A chemical signal passes between neurons.
– Impulse reaches terminal.– Neurotransmitters released into synapse.
impulse
synapse
receptorvesicles
neurotransmitter
– Neurotransmitters stimulate next cell.
29.1 How Organ Systems Communicate
KEY CONCEPT 29.3The senses detect the internal and external environments.
29.1 How Organ Systems Communicate
The senses help to maintain homeostasis.
• Senses gather stimuli, and send it to the nervous system.
• Nervous system responds to stimuli.– Pupils shrink when too much
light enters the eyes.– Goose bumps when cold air
touches skin.
29.1 How Organ Systems Communicate
The senses detect physical and chemical stimuli.
• The eye contributes to vision. – Photoreceptors sense light.– Two photoreceptors work
together: rod cells and cone cells.
29.1 How Organ Systems Communicate
• The ear contributes to hearing.
– mechanoreceptors called hair cells – bend in response to vibrations
29.1 How Organ Systems Communicate
• Taste and smell use chemoreceptors.
– Taste uses tongue, and smell uses nose.– Chemoreceptors detect chemicals dissolved in fluid.
29.1 How Organ Systems Communicate
• The skin senses touch.
– Mechanoreceptors detect pressure.
pain receptor
light pressure receptor
hair follicle
heavy pressure receptor
– Pain receptors detect damaged tissue.
– Thermoreceptors detect temperature.
29.1 How Organ Systems Communicate
KEY CONCEPT 29.4The central nervous system interprets information, and the peripheral nervous system gathers and transmits information.
29.1 How Organ Systems Communicate
The nervous system’s two parts work together.
• The CNS includes the brain, brain stem, and spinal cord.• The PNS includes four systems of nerves.
29.1 How Organ Systems Communicate
• The CNS and PNS pass signals between one another.
– Sensory receptor generates impulse. – PNS passes impulse to CNS. – CNS interprets impulse.– CNS passes impulse to PNS. – PNS stimulates a response.
29.1 How Organ Systems Communicate
The CNS processes information.
• The brain has three parts. – cerebrum controls
thought, movement, emotion
– cerebellum allows for balance
midbrainpons
medulla oblongata
– brain stem controls basic life functions
Brainstem
29.1 How Organ Systems Communicate
• The brain stem has three parts.
– midbrain controls some reflexes
– pons regulates breathing – medulla oblongata
controls heart function, swallowing, coughing
midbrain
medulla oblongata
pons
29.1 How Organ Systems Communicate
• The spinal cord controls reflexes.
– sensory neuron sends impulse to spinal cord– spinal cord directs impulse to motor neuron – does not involve the brain
interneuron
motor neurons
sensory neuron
29.1 How Organ Systems Communicate
The PNS links the CNS to muscles and other organs.
• The somatic nervous system regulates voluntary movements.
• The autonomic nervous system controls involuntary, functions
– sympathetic nervous system: “fight vs. flight”
– parasympathetic nervous system: calms the body, conserves energy
29.1 How Organ Systems Communicate
KEY CONCEPT 29.5Scientists study the functions and chemistry of the brain.
29.1 How Organ Systems Communicate
New techniques improve our understanding of the brain.
• Today, scientists study the brain without surgery.
29.1 How Organ Systems Communicate
• There are three common technologies.
– CT uses x-rays to view structure.
– PET detects activity, where glucose is used, in the brain.
– MRI uses magnetic fields and radio waves to view structure.
29.1 How Organ Systems Communicate
Changes in brain chemistry can cause illness.
• Different neurotransmitters relate to different functions.
– some stimulate impulses– some prevent impulses
synapse
Normal
neurotransmitter
receptor
29.1 How Organ Systems Communicate
• Abnormal levels of neurotransmitter can cause illness.
– schizophrenia– depression
Normal Schizophrenic Depressed
29.1 How Organ Systems Communicate
Drugs alter brain chemistry.
• Addiction is the physiological need for a substance.
• Tolerance occurs when more drug is needed to produce an effect.
• Drugs might cause desensitization or sensitization.– desensitization: more
neurotransmitter leads to fewer receptors
– sensitization: less neurotransmitter leads to more receptors.
When the amount of neurotransmitter becomes abnormal, the adjacent neuron adapts.
29.1 How Organ Systems Communicate
• Stimulants cause more action potentials– may increase neurotransmitter in synapse– may decrease removal of neurotransmitter in
synapse cocaine
neurotransmitter
synapse
29.1 How Organ Systems Communicate
• Depressants cause fewer action potentials.– may produce neurotransmitter that prevent impulses – may slow release of neurotransmitter that generates
impulses
29.1 How Organ Systems Communicate
KEY CONCEPT 29.6The endocrine system produces hormones that affect growth, development, and homeostasis.
29.1 How Organ Systems Communicate
Hormones influence a cell’s activities by entering the cell or binding to its membrane.
• Glands are organs of the endocrine system.
29.1 How Organ Systems Communicate
• Hormones are chemical signals that influence cell’s activities.– produced by glands– travel through the circulatory system– affects cells with matching receptors
target cell
hormone
receptornot a target cell
bloodstream
29.1 How Organ Systems Communicate
• There are steroid hormones and nonsteroid hormones.– Steroid hormones enter the cell. – Nonsteroid hormones do not enter the cell.
Steroid hormone diffuses through the cell membrane
Steroid hormone binds to a receptor within the cell.
The hormone and receptor enter the nucleus and bind to DNA
Steroid hormone causes DNA to make proteins.
Nonsteroid hormone binds to receptor on the cell membrane.
Receptor stimulates a second messenger with in the cell.
Second messenger starts a series of chemical reactions in the cytoplasm.
Second messenger reactions activate enzymes.
Steroid hormone
receptor
nucleus
DNA
proteins
Non-steroid hormone
receptor
second messenger
Chemical reactions
activated enzymes
29.1 How Organ Systems Communicate
Endocrine glands secrete hormones that act throughout the body.
• There are many glands located throughout the body.
– Hormones travel through the bloodstream to cells with matching receptors.
HYPOTHALAMUS
PITUITARY
THYROID
THYMUS
ADRENAL GLANDSPANCREASFEMALE GONADS :OVARIES
MALE GONADS : TESTES
29.1 How Organ Systems Communicate
The hypothalamus interacts with the nervous and endocrine systems.
– a structure of both the nervous andendocrine systems
– produces releasing hormones,sent to pituitary gland
• The pituitary gland is found below the hypothalamus in the brain.– controls growth and water
levels in blood – produces releasing hormones
sent throughout the body
• The hypothalamus is a gland found in the brain.
29.1 How Organ Systems Communicate
• Releasing hormones stimulate other glands to produce hormones.– allow glands to
communicate with one another
– are used in temperature regulation
29.1 How Organ Systems Communicate
Hormonal imbalances can cause severe illness.
• Abnormal hormone levels affect homeostasis.• Hormonal imbalances might be treated with surgery or
medicine.• Steroids, a pituitary tumor, or some prescription drugs can
make the pituitary overactive and indirectly cause problems.
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