SBI 4UO LESSON PLANS

Ontario Curriculum objectives: U=understanding concepts (U1-U4) D=developing skills (D1-D3) R=relating science (R1-R3)

Text: Biology 12, Nelson

Homeostasis is the processes of maintaing a balance in body
One organ involved in homeostasis is the kidney

Humans have two kidneys
Functions:
-remove wastes from blood (e.g. urea, ammonia from deamination of proteins in liver and uric acid from nucleic acid breakdown)
-maintain water balance (2L lost daily due to urine, perspiration, exhaled air) as loss of 1% water results in thirst, 5% in pain, 10% in death

Structure:
-capsule surrounds kidney
-cortex is outer region
-medulla is middle region
-pelvis is inner region
-ureter carries urine out of kidney
-renal artery enters kidney with unfiltered blood
-renal vein leaves kidney with filtered blood

-kidney empties contents of blood into tubules, then reabsorbs material needed by body
-these tubules are called nephrons …there are 1.25 million nephrons per kidney

-afferent arteriole carries unfiltered blood from the renal artery into glomerulus
-glomerulus receives blood under high pressure and water, salts, urea, glucose and amino acids diffuse into the Bowman’s capsule as “filtrate”

-blood cells and blood proteins stay in the blood as they are too large, and blood moves off through the efferent arteriole into a bed of capillaries around the tubules which will end up leaving the kidney as the renal vein

-filtrate leaves the Bowman’s capsule via the proximal segment, where nutrients are reabsorbed into the blood by diffusion and active transport

-as filtrate moves descends down the loop of Henle it is impermeable to salts but water is able to move into the blood by osmosis…this results in the salt concentration of the filtrate increasing

-as the loop of Henle turns and ascends  it is permeable to salts and salt diffuses into the blood

-in the distal tubule secretion occurs as some material (ammonia, drugs) move back into the urine from the blood by active transport

-the remaining urine passes into the collecting duct…here some urea diffuses into the surrounding tissue drawing more water out of the urine and into the blood
-reabsorption of nutrients in the nephron occurs until material into the blood has reached the “threshold level” and no more nutrients may be absorbed

-urine now passes from the collecting ducts into the pelvis and empties into the ureter
-the two ureters carry urine to a common urinary bladder and through the urethra, out the body

The neuroendocrine system is responsible for most homeostasis…it is comprised of two systems
Endocrine System: glands secrete hormones (chemical messages in blood)
Nervous System: Electrical impulses cause nerves to fire

Neurons are cells that transmit messages in this system (a group of neurons is a nerve)
Neuroglia are protective cells in this system

Two main parts of the nervous system are the:
Central Nervous System (CNS) consists of brain and spinal column

Peripheral Nervous System (PNS) consists of nervous tissue outside the brain and spinal column
-autonomic paripheral nervous system is involuntary, controlling visceral and cardiac muscles (breathing, digesting, heart)
-sensory somatic peripheral nervous system is voluntary, controlling skeletal muscles

Draw and label a motor neuron, including dendrite, axon, Schwann cells, myelin sheath, node of Ranvier, terminal end plates and brushes

Parts of Motor Neuron:
Dendrite: receives messages from other neurons
Axon: transmits message from one part of neuron to the next
Schwann cells: fatty neuroglia  (protective cells) around the axon (appear white)
Myelin Sheath: a layer of Schwann cells acting as an insulator around the axon
Nodes of Ranvier: unprotected gaps between Schwann cells in the myelin sheath
Terminal End Plate: release chemical message from neuron to next cell (axon branches into these via terminal end brushes)

Video on “The Brain”

Work on middle questions from Homeostasis questions

-quiz next class on motor neuron

A reflex is a quick message in which the decision in the spinal column to increase the speed (no brains involved…c’est moi)

Receptor Cells: detect messages, pass these on to sensory neurons
e.g. mechanoreceptors detect movement, photoreceptors detect light, thermoreceptors detect temperature

Neurons: cells which carry messages in the nervous system
Sensory/Afferent neurons: relay information from a receptor to spinal column
Association neurons: about 50 billion of these, in brain and spinal column
 -join afferent and efferent neurons and decide what to do with messages
Motor/Efferent neurons: relay information from central nervous system to effectors

Effectors: cells which respond to stimuli (e.g. muscle, gland)

Nerves: collection of neurons together
Sensory/Afferent nerves: carry afferent neurons to CNS (enters back through dorsal/back side of vertebrae)…cell bodies are outside spine in groups called dorsal root ganglion
Motor/Efferent nerves: carry efferent neurons from CNS (leaves through ventral/front side of vertebrae)
Mixed nerves: carry afferent and efferent neurons going opposite directions

Spinal cord contains cerebrospinal fluid surrounded by grey matter (association neurons) which are in turn surrounded by a layer of Schwann cells called white matter. A bone vertebrae surrounds this for extra protection.

Label the diagram of the reflex arc and the three different neurons.

-nervous impulse is a self-propagated wave of electro-negativity that travels along the surface of the neurolemma (neuron membrane)
-the neuron uses its own energy for impuse transmission

Polarized State:
-the membrane of the “resting” neuron is found to be electrically polarized
-the neuron has a charge distribution across the membrane of –70 mV inside relative to outside
-the –70 mV is called resting action potential
-the resting action potential is due to the unequal distribution of sodium and potassium ions as a result of the action of the sodium and potassium pumps through the transmembrane proteins
-three sodium ions are pumped out of the neuron for every two potassium ions pumped in at the expense of ATP (active transport)…This results in an increase in the positive charge outside the neuron (+1 each time)
-potassium ions may diffuse by facilitated diffusion through proteins back outside the neuron resulting in a further increase in positive charge
-sodium is unable to diffuse into the neuron, resulting in a polarized state where the neuron has positive outsides relative to negative insides

Initiation of an Impulse:
-a neuron is stimulated by pressure or chemicals
-a minimum amount of stimulus (the threshold level) must be reached to fire the neuron (more than this is wasted as neuron will either fire or not fire)
-this stimulus results in the alteration of shape of the proteins in the membrane resulting in facilitated diffusion of sodium ions into the neuron through sodium ion channels
-this influx of positive charge results in a depolarized state, or charge reversal
-the inside of the membrane becomes positively charged (+40 mV relative to outside the membrane)
-the overall change in charge (+110 mV) from polarized to depolarized is called the action potential
-this channel then closes and the sodium-potassium pump reestablishes the polarized state
-this recovery period (called the refractory period) takes approximately 5 ms  during which the neuron cannot fire
-as one sodium channel opens, the one next to it does likewise
-this results in a wave of depolarization followed by a wave of polarization all the way down the neuron
-if the impulse hits a Schwann cell in the peripheral nervous system it will jump to the next node of Ranvier (these are 500X more permeable to ions as well) allowing the impulse to be transmitted quicker outside the central nervous system (and cheaper metabolically)
-movement of the impulse from node to node is called saltatory conduction
-as impulses require ATP for the sodium potassium pumps to repolaraize, cellular respiration occurs in neurons to produce this ATP as neurons fire

Other Notes:
-a neuron will continue to fire unless stimulus is removed, but is protected from damage by the refractory period (effector cells are not protected this way)
-energy for impulse conduction comes from ATP provided by the cell, not the initial impulse
-there are 0.6 ms delays in messages at synapses (gaps between one cell and the next) that must be crossed by chemical messages (neurotransmitters)
-neurons only carry messages in one direction

-a synaptic cleft is a 10-20 nm gap between one neuron and the next cell
-neurotransmitters are chemicals released from the pre-synaptic membrane into the synapse and affect the post-synaptic membrane
-neurotransmitters bind to receptors on the post-synaptic membrane resulting in a depolarization or repolarization of the next membrane

Some common examples of neurotransmitters are acetylcholine (Ach), dopamine, serotonin, endorphins

How a message is transmitted across a synapse:
-action potential arrives at a synapse
-a neurotransmitter is released from vesicles at the end of a neuron (pre-synaptic membrane) and moves into the synapse
-the neurotransmitter binds to receptors on the post-synaptic membrane and may cause excitation of this membrane when the threshold level is reached
-when the post-synaptic neuron membrane is depolarized, action potential moves down the next neuron
-an enzyme now breaks down the neurotransmitter and returns it to the pre-synaptic membrane
-the neurotransmitter is repackaged

Types of synapses:
neuron to neuron synapse: a neurolemma (neuron membrane) is depolarized by a neurotransmitter
-an excitatory synapse: the neurotransmitter causes the post-synaptic membrane to depolarize by decreasing the resting potential
-an inhibitory synapse: the neurotransmitter reduces the ability of the post-synaptic membrane to depolarize by increasing the resting potential
-the summation of these two types of synapses determines if the next neuron will depolarize or not

neuron to muscle synapse: the sarcolemma (muscle membrane) is depolarized by the release of a neurotransmitter (usually acetylcholine)
-this results in the release of calcium ions form sacs in the sarcomere (actin and myosin unit that contracts in muscles)
-this results in the contraction of the muscle
-an enzyme must now break down the neurotransmitter (Acetylcholinesterase or AchE in the case of the neurotransmitter acetylcholine) or the muscle will stay contracted
-many insecticides such as malathion (or nerve gases) inhibit the action of acetylcholinesterase resulting in organisms convulsing and then dying of heart attacks.

Another neurotransmitter:
Dopamine:
-produced in neurons in the frontal cortex of the brain, results in feelings of euphoria and satisfaction
-broken down by enzyme MAO
Effects of drugs on dopamine synapses:
-cocaine blocks reabsorption of dopamine allowing the neurotransmitter to accumulate in the synapse and fire the neuron repeatedly
-amphetamines stimulate the release of large amounts of dopamine (faster than the body can break it down)
-cigarettes…nicotine stimulates release of dopamine while other chemicals in cigarettes block the action of MAO resulting in continued firing of the next neuron
Addiction: addicts become used to high levels of dopamine. Excessive use of these drugs causes the brain to reduce the number of dopamine receptors, requiring more drugs for the same affect.

The Brain: 50 billion association neurons make up the human brain

(I) Prosencephalon (front/top of brain):

(a) Telencephalon:
-contains the cerebrum, two large hemispheres which occupy 5/6 of the human brain
-the exterior of the cerebrum is called the cerebral cortex and contains the association neurons
-each hemisphere is divided into four lobes: frontal, parietal, occipital and temporal
-each hemisphere is connected to the other hemisphere by the corpus collasum

(b) Diencephalon:

(II) Mesencephalon (middle of brain):

(III) Rhombencephalon (rear of brain):

Label the diagram of the brain

Brain: organ composed of 50 billion association neurons (grey colour as it contains no myelin…skull provides protection)
Protective Layers: 3 membranes called meninges lie within the skull
Skull, then dura mater, arachnoid, cerebral fluid, pia mater and then the cerebral cortex (outer 3 mm of cerebrum)
-an infection of these three membranes is called meningitis
-cerebral fluid is protected by phagocytic neuroglia called microglia

Sulcus: folds in the brain
Fissures: Big grooves in the brain
Central Fissure separates the two hemispheres of the brain
The left hemisphere of the brain controls speech, logic and math
The right hemisphere of the brain controls pictures, music and creativity
You use both sides of the brain

Short term memory is lost in a minute or so and thought to be chemically stored
Long term memory lasts forever and is stored by a physical change in the neurons

Describe effects of cutting corpus collasum ( left brain rationalizes things done by the right brain)
Do right brain/left brain activity
Label brain diagram , view sheep brain if possible

-the endocrine system consists of all tissues/chemicals involved in controlling/coordinating body with hormones in blood and lymph
Glands: organs that make hormones, metabolic chemicals
Endocrine glands: release chemicals into blood, lymph
Exocrine glands: release chemicals to outside of body or digestive tract (e.g. salivary glands)

Hormone Composition:
1. Peptide Hormones
(a) molecule made of one amino acid…e.g. adrenaline
(b) enkalphins: 5 a.a. long…painkillers
(c) endorphins: 32 a.a. long…painkillers as well
(d) longer proteins: e.g. insulin
These hormones land on receptors on the surface of cells without actually entering the target cell themselves

2. Steroid hormones: lipids made of 3 6-carbon chains and 1 5-carbon chain
e.g. cortisone, testosterone, estrogen
These hormones cross the target cell membranes to join receptors in the nucleus

Hormones may work antagonistically (opposite each other) or with biofeedback (controlling each other)

Pituitary:
-master gland below the hypothalamus consisting of two lobes

(a) Anterior Lobe of Pituitary:

-also produces diabetogenic, glycotrophic, ketogenic , parathyrotrophic and pancreatrophic hormones which control blood sugar, insulin and fat production levels

(b) Posterior Lobe of Pituitary: