unit 29 endocrine system

29.1 How Organ Systems Communicate

KEY CONCEPT The nervous system and the endocrine system provide the means by which 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.


• The nervous system controls thoughts, movement, and emotion.

• The endocrine system controls growth, development, and digestion.


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)


• 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

29.2 Neurons

KEY CONCEPT The nervous system is composed of highly specialized cells.

29.2 Neurons

Neurons are highly specialized cells.

• A neuron has three parts.– cell body has nucleus and organelles

1 Cell body

29.2 Neurons

– dendrites receive impulses



2 dendrites

29.2 Neurons

– axon carries impulses

3 axon

– dendrites receive impulses



29.2 Neurons

• Neurons have other structures to transmit signals.

– Schwann cell

29.2 Neurons

– synapse

synapse


– Schwann cell

29.2 Neurons

– terminal

– synapse


– Schwann cell

axon terminal

29.2 Neurons

Neurons receive and transmit signals.

• Resting potential means no signal is being transmitted. – more Na+ outside of cell – more K+ inside of cell

29.2 Neurons

• 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

29.2 Neurons

• A chemical signal passes between neurons.

– Impulse reaches terminal.

impulse

29.2 Neurons


– Impulse reaches terminal.

synapse

receptorvesicles

impulse

neurotransmitter

– Neurotransmitters released into synapse.

29.2 Neurons


– Impulse reaches terminal.– Neurotransmitters released into synapse.

impulse

synapse

receptorvesicles

neurotransmitter

– Neurotransmitters stimulate next cell.

29.3 The Senses

KEY CONCEPT The senses detect the internal and external environments.

29.3 The Senses

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.

29.3 The Senses

The senses detect physical and chemical stimuli.

• The eye contributes to vision. – Photoreceptors sense light.– Two photoreceptors work

together: rod cells and cone cells.

29.3 The Senses

• The ear contributes to hearing.

– mechanoreceptors called hair cells – bend in response to vibrations

29.3 The Senses

• Taste and smell use chemoreceptors.

– Taste uses tongue, and smell uses nose.– Chemoreceptors detect chemicals dissolved in fluid.

29.3 The Senses

• 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.

29.4 Central and Peripheral Nervous Systems

KEY CONCEPT The central nervous system interprets information, and the peripheral nervous system gathers and transmits information.


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.


• 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.


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


• The brain stem has three parts.– midbrain controls some reflexes– pons regulates breathing – medulla oblongata controls heart function,

swallowing, coughingmidbrain

medulla oblongata

pons


• 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


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

29.5 Brain Function and Chemistry

KEY CONCEPT Scientists study the functions and chemistry of the brain.


New techniques improve our understanding of the brain.

• Today, scientists study the brain without surgery.


• 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.


Changes in brain chemistry can cause illness.

• Different neurotransmitters relate to different functions.

– some stimulate impulses– some prevent impulses

synapse

Normal

neurotransmitter

receptor


• Abnormal levels of neurotransmitter can cause illness.– schizophrenia– depression

Normal Schizophrenic Depressed


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.


• Stimulants cause more action potentials– may increase neurotransmitter in synapse– may decrease removal of neurotransmitter in synapse

cocaine

neurotransmitter

synapse


• Depressants cause fewer action potentials.– may produce neurotransmitter that prevent impulses – may slow release of neurotransmitter that generates impulses

29.6 The Endocrine System and Hormones

KEY CONCEPT The endocrine system produces hormones that affect growth, development, and homeostasis.


Hormones influence a cell’s activities by entering the cell or binding to its membrane.

• Glands are organs of the endocrine system.


• 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


• 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


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


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.


• Releasing hormones stimulate other glands to produce hormones.

– allow glands to communicate with one another

– are used in temperature regulation


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.

unit 29 endocrine system

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