Chapter 11… Continued!

Review from last week…

• How do we control our muscles?– (How do we use the nervous system to make our

muscles contract?)

• Brain spinal cord motor nerve motor neuron effector (muscle)

Antagonistic Pairs of Muscles

• Pairs of muscles that work in opposite directions on the same body part– Circular and radial muscles in iris (eye)– Biceps and triceps muscles on elbow joint

• Biceps = flexor muscle– Flexes (bends) the arm

• Triceps = extensor muscle– Extends (straightens) the arm

Let’s Work Our Muscles!

• Flexion of elbow– Biceps contracts, pulling radius toward scapula– Triceps relaxes

• Extension of elbow– Triceps contracts, pulling ulna toward

scapula/humerus– Biceps relaxes

Reflexes in Simple Animal Behavior

• Taxis = a movement in response to a stimulus– The direction of movement is determined by the

direction of stimulus

• Phototaxis = response to light– Positive = toward the light = moth– Negative = away from light = cockroach

• Geotaxis = response to gravity• Chemotaxis = response to chemicals

Drugs that Affect the Brain

• Stimulants = increase alertness– Caffeine – found in coffee, tea, cola, chocolate,

etc

• Depressants = slow down the brain– Alcohol – slows down the conduction of nerve

impulses – slows reflexes, voluntary movements, and sensory perceptions

• Narcotics = relieve pain, produce sleep– Codeine, morphine, and heroin

Movie Time!

Endocrine Control: Systems in Balance

The Endocrine System

• Hormones = chemicals that are used to pass information around the body– (In the NS it was electrical signals; now it’s

chemical signals)

• Endocrine Glands = organs that make and secrete the hormones

• Blood Capillaries = run through the gland and pick up the secreted hormones, then carry them through the bloodstream

Hormones

• Hormones travel all through the body (in blood), but only affect target organs.

• Insulin’s target organ is the liver– (but it’s made and secreted by the pancreas!)

• Hormones eventually get broken down by enzymes and excreted by the kidneys.

Endocrine Glands

From Page 170…

Endocrine Gland

Hormone Function of Hormone

Adrenal Gland Adrenaline Prepares body for “fight or flight”

Pancreas InsulinGlucagon

Reduces blood glucoseIncreases blood glucose

Testis Testosterone Produces male secondary sexual characteristics

Ovary Estrogen Produces female secondary sexual characteristics

Ovary Progesterone Involved in controlling menstrual cycle and pregnancy

Chemical Analogs

• Chemicals with similar properties.• They function in similar ways in the body.– Artificial flavors in foods…

Remember the Seagulls?

• A chemical analog of Estrogen in the water (from pollution) caused “testicular feminization” in male birds.

• The males became so feminine that they wouldn’t mate with the females or help raise the chicks!

• So females paired up together…

Adrenaline

• Adrenaline = a hormone that increases your metabolic rate – Prepares your body for “fight or flight”

• Comes from the adrenal gland– Just above your kidneys– (notice the word part “renal” in there?)

• Your brain sends a nerve signal to adrenal glands, stimulating them to secrete adrenaline into the blood.

Adrenal Glands

Fight or Flight

Adrenaline’s Functions

• Increases heart rate • Increases blood glucose – (T.O. = Liver)

• Restricts blood to digestive system; increases blood to muscles– (T.O. = Arteries/arterioles)

• Increases width of lung passages– (T.O. = Bronchii/bronchioles)

Adrenaline…

• What is its function?• What endocrine gland does it come from?• What is its target organ?

Let’s Compare…

Nervous System Endocrine System

Type of Signal Electrical Chemical

Speed of Signal several meters per second ~ speed of blood

Where the Signal Travels In neurons and nerves In blood vessels

Where the Signal is Delivered

To a specific part of the body

Throughout the body (but only affects T.O.’s)

How Long the Signal Lasts Seconds or less Minutes/Hours/Days

Questions for Homework

• Why is it important that we have our Nervous and Endocrine Systems? What could happen if either one were to malfunction?

• Why do the Nervous and Endocrine System work in the different ways that they do? Why it is important that each System works in the ways that it does?

Plants have Hormones, Too!

• Plant hormones are chemicals (just like ours).– But plants do NOT have endocrine glands.

• Plant hormones travel through the veins of the plant.

• They are broken down by plant enzymes.

How do Plants Grow?

• Plants grow by making new cells at the tips of their roots and shoots.

• At the same time, older cells on the roots and shoots grow by getting longer.

But how do the cells know to get longer?

Auxin

• Auxin = a plant hormone / growth substance that stimulates plant cells to lengthen.

• It’s made by cells at the tips of roots and shoots.

• Then it diffuses back along the roots/shoots and makes the older cells grow longer.

But how does a plant grow towards the light?

Phototropism

• In order to change direction, a plant shoot must grow longer on one side than the other.

• If light shines on the plant from one direction, Auxin accumulates on the shady side of the shoot.

• The shoot lengthens on the shady side, bending the plant toward the light!

Tropisms• Tropism = a plant’s growth response to a stimulus– The direction of growth is determined by the direction

of the stimulus

• Phototropism = ?– Do plants show positive or negative phototropism?

• Geotropism = ?– Do plant roots show (+) or (-) geotropism?– What about plant shoots?

Use of Plant Hormones

• Auxin as a selective weedkiller…– (makes weeds grow too fast and die!)

• Auxin’s use in rooting cuttings…– (makes plant cuttings take root after being dipped

in ‘hormone rooting powder’)