Structure And Function of Animals

Question 1

What is a neuron?

Answer 1

the transmitters of the nervous system

• made of dendrites, thin branches extending from cell body
• cell body, contains nucleus and cell organelles
• axon, which can be much larger than rest of cell, and ends in several branches called axon terminals

Question 2

how does an electrical impulse move through a neuron?

Answer 2

1. begins in dendrites
2. passes through cell body to axon
   - At the end of an axon, there is a space called a synapse that separates it from the dendrite of the next neuron.
3. when impulse reaches synapse at end of axon, specialized chemicals called neurotransmitters get released
4. Neurotransmitters carry the signal across the synapse to the dendrites of the next neuron.

Question 3

What is the resting potential of a neuron?

Answer 3

When no charge is going through a neuron, it is at its resting potential

A protein called Na+/K+ ATPase uses one ATP molecule to pump three positively charged sodium atoms out of the neuron, and two positively charged potassium atoms into the neuron.

The difference in ion concentration between the potassium on the inside and sodium on the outside creates a net potential difference across the cell membrane of about -70 millivolts.

-70 millivolts is thus the resting potential of a neuron.

Question 4

What is the action potential of a neuron?

Answer 4

Neurons contain protons that respond to changes in the membrane potential by opening to allow certain ions to cross that would not normally be able to. The neuron has voltage gated sodium channels, and potassium channels.

1. chemical signals from another neuron make the potential of the cell membrane of dendrites less negative.
2. the voltage gated sodium channel in that region opens. The channel opens at whats called the threshold potential, which is -50 millivolts.
3. As positive sodium ions rush in, the cell membrane potential gets as high as +35 millivolts.
4. the sodium channels close, and voltage gated potassium channels open. Potassium ions rush out of the neuron, decreasing the cell membrane to its negative resting potential.
5. At -90mV, the potassium channels close. Then, Na+/K+ ATPase restores the membrane potential to its original -70mV

Question 5

What happens at the end of an Action potential?

Answer 5

sodium channels stay shut as the neuron becomes negatively charged to prevent the action potential from going backward.

Question 6

What is the myelin sheath?

Answer 6

a structure that surrounds neurons.

• made of Schwann cells with wrap around the axon of the neuron, leaving gaps in between called the nodes of Ranvier
• sodium and potassium ions only cross the cell membrane at these nodes
• when action potential is triggered at one node, the sodium ions that enter the neuron trigger an action potential at the next node
• this jumping of the potential from nerve to nerve is called saltatory conduction

Question 7

What is multiple sclerosis?

Answer 7

A disease that damages the myelin sheath, impeding conduction of impulses along neurons.

Question 8

What causes an action potential to be stronger?

Answer 8

When, for example, you touch lukewarm water versus a burning iron, the action potential is NOT stronger. However, action potentials are fired more rapidly.

-An action potential never changes strength.

Question 9

What are neurotransmitters?

Answer 9

chemical signals encased in vesicles that communicate a neurons action potential to the next neuron by binding to the receptors in the dendrites of the adjacent neuron.

• excitatory neurotransmitters cause the target neuron to allow positive ions to enter, supporting an action potential.
• inhibitory neurotransmitters cause the target neuron to allow negative ions, blocking an action potential.

-one neuron forms a synapse with many others, meaning that the effect of multiple neurons neurotransmitters are added up to determine wether or not an action potential will fire.

Question 10

What happens to a neurotransmitter after it effects its target?

Answer 10

it is usually absorbed by surrounding cells or deactivated by enzymes in the snyapse

Question 11

What are the nervous systems of the different animal phylum?

Answer 11

Cnidarions: Simple, unorganized
Annelids/Molusks: Organized clusters called ganglia, that fuse in the head region to form a simple brain
Arthropods: complex nerve system including sensory organs
vertebrates: highly centralized with large brain, specialized sensory organs

Question 12

What is the Central Nervous System? What is the Peripheral Nervous System?

Answer 12

the CNS is the central command structure. It controls breathing, digestion, complex behavior, and consciousness
the PNS is the pathways through which the CNS communicates with the rest of the body

Question 13

What are Sensory, Motor, and InterNeurons

Answer 13

Sensory Neurons send stimuli to the Central Nervous System
Motor Neurons carry information away from the CNS to organs and muscles
InterNeurons connect sensory and motor neurons

Question 14

What makes up the CNS?

Answer 14

A spinal cord, which is a long cylinder of nervous tissue extending from the head to the lower back, and the brain.

• the cerebrum is the seat of a brains consciousness
• The cerebellum coordinates movement
• The brainstem, and specifically the medulla, controls involuntary functions like breathing and cardiovascular regulation
• The hypothalamus maintains homeostasis, regulates temperature, controls hunger/thirst, and generates emotion

Question 15

What are the somatic and autonomic nervous system?

Answer 15

Parts of the peripheral nervous system

The somatic nervous system controls conscious movement, and has neurons that only target skeletal muscles. These neurons release acetylcholine, an excitatory neurotransmitter that contracts skeletal muscles. None of these neurons have an inhibitory effect.

The autonomic system controls every other tissue besides skeletal muscles, like smooth/cardiac muscle, glands, and organs. It controls processes that animals have no voluntary control of. Autonomic neurons can excite or inhibit their target. Autonomic neurons can be subdivided into the sympathetic and parasympathetic division.

Question 16

What is the sympathetic division? What is the parasympathetic division?

Answer 16

The sympathetic division preps the body for emergencies; it increases heart and breathing rate, diverts blood from the digestive system, and stimulates the medulla to release epinephrine and norepinephrine, hormones that reinforce the effect of the neurons. It produces what is known as the fight or flight response
The parasympathetic works when the body is at rest; it slows the heart rate/breath, increases digestion. Acetylcholine, an inhibitor, is most associated with the division.

Question 17

Discuss vision

Answer 17

-eyes can determine intensity, color, and frequency of light. The retina contains photoreceptors called rods and cones which sense the different types of light that hit them
-rods are very sensitive/respond to low level illumination
-cones respond to bright light/responsible for color vision
pigments in these cells change their shape when stimulated by light, triggering an action potential to fire in a neuron, which passes along the optic nerve to the occipital lobe of the brain, and is processed.
-The lens of the eye is what focuses light onto the retina, and can change shape to ensure sharpness.
-the pupil is the hole in the eye that regulates the flow of the light. The iris is a muscle that adjusts the pupil
- the cornea is the outer layer of the eye, and bends light through the pupil into the lens

Question 18

Discuss hearing

Answer 18

sound energy causes the tympanic membrane (or eardrum) to vibrate at the same frequency as the sound

• the vibration is conducted through the three auditory ossicle bones, which amplify and direct the sound into the cochlea
• hair cells in the cochlea convert the vibrations into action potentials
• action potentials are transmitted down the auditory nerve into the brain

Question 19

Discuss Balance

Answer 19

The ear actually helps maintain balance!

• three canals in each ear contain hair cells and a specialized fluid
• when the head moves, the fluid position moves
• changing pressure on the hair cells affects how they fire action potentials, which go into the brain through the vestibular nerve.

Question 20

Discuss Taste And Smell

Answer 20

Chemoreceptors respond to taste, and are located on the surface of the tongue in taste buds.
these taste buds create action potentials based on the taste that travel along the facial and glossopharyngeal nerves into the brain.
Smell originates when the molecules of a substance pass along the olfactory epithelium. The molecule then dissolves in mucus which coats the epithelium, and binds to surface receptors. There are 1000+ receptor types in the nose, and when one is activated, it transmits its signal through the olfactory nerve.

Question 21

What is the Endocrine System? What are the two major types of Hormones?

Answer 21

The endocrine system works with the nervous system to control/coordinate other organ systems. It is made up of endocrine glands which communicate with the body by releasing hormones into the bloodstream

• these hormones target a specific organ in the body, and binds only to that organ.
• hormones can affect cells for minutes to years

Peptide hormones are composed of small amino acid chains which cannot cross cell membranes, so must be transported through vesicles. They generally work quickly.

Steroid hormones are ring shaped lipids made from cholesterol. They are hydrophobic, and can pass directly into their target cells. The receptors for steroid hormones are on the interior of the target cells.
Steroids change the rate of protein synthesis, and act more slowly than peptide hormones.

Question 22

What is the pituitary gland?

Answer 22

A tiny gland at the base of the brain. The hormones it produces control the secretion of of hormones in other endocrine organs. The pituitary itself is controlled by the hypothalamus.

• The anterior pituitary gland produces six hormones, and the hypothalamus produces a releasing factor that stimulates the anterior pituitary gland to make those hormones.
• the two hormones released by the posterior pituitary gland are actually produced in the hypothalamus, and merely stored by the pituitary gland until release into the blood.

Question 23

What are the six hormones produced by the anterior pituitary gland?

Answer 23

Growth Hormone: which stimulates growth in many body tissues. It is important for growing children, and affects the rate that older cells are replaced in adults

Follicle-Stimulation Hormone: stimulates the maturation of ova in the ovaries and sperm in the testes

Lutenizing hormone: triggers ovulation in woman, and testosterone in males.

Prolactin: released after pregnancy and stimulates milk production in the female mammary glands

Thyroid-stimulation Hormone: stimulates the thyroid to release its hormone, thyroxine.

Adrenocorticotrophic Hormone: stimulates the adrenal cortex to release its corticoid hormone.

Question 24

What are the two hormones stores in the posterior pituitary?

Answer 24

Antidiuretic Hormone: regulates kidneys to conserve water

Oxytocin: stimulates uterine contraction during childbirth.

Question 25

What is the Thyroid Gland?

Answer 25

produces the hormone thyroxine, which increases metabolism of most body cells.

• too little can cause hypothyroidism, which is lower metabolism, obesity, and sluggishness
• too much can cause hyperthyroidism, which leads to excessive perspiration, high temperature, weight loss, and a fast heart rate

Question 26

What are Parathyroid Glands?

Answer 26

four small glands embedded on the thyroid gland. They produce parathyroid hormone, which regulates calcium in the bloodstream.

Question 27

What is the Pancreas?

Answer 27

A large organ behind the stomach that releases digestive enzymes into the small intestine, and releases insulin and glucagon hormones into the bloodstream through cells called islets of Langerhan

• Insulin stimulates cells to absorb glucose from the bloodstream when glucose levels are high. It also stimulates the liver to remove glucose from the blood and store it as glycogen.
• Glucagon is released when blood glucose levels are low, and stimulates the liver to break down glycogen into glucose and release it into the bloodstream, raising blood sugar levels.

Question 28

What are the Adrenal Glands?

Answer 28

• located on the kidney
• made of the adrenal medulla, the interior portion, and the adrenal cortex, the exterior portion
• The sympathetic nervous system causes the adrenal medulla to release norepinephrine and epinephrine into the bloodstream, which ready the body for stress
• the only difference between adrenal medulla and the sympathetic nervous system is that hormones stay in bloodstream for a much longer time.
• The adrenal Cortex releases three steroid hormones; glucocorticoids, which affect glucose levels. Mineralocorticoids, which affect mineral absorbation by the kidneys. and sex steroids, which affect sexual processes

Question 29

What are the Gonads?

Answer 29

• sex organs that produce gametes
• in males, produce testosterone, which is necessary for sperm production and development of sex characteristics
• in females, the ovaries produce estrogen and progesterone, which maintain female sex characteristics, stimulates growth of the uterine lining for pregnancy, and prep the uterus for embryo implantation

Question 30

What are the circulatory systems of cnidarians, annelids and arthropods?

Answer 30

cnidarians have no circulatory system because all cells are in contact with the external environment
annelids have a simple closed circuit of blood vessels with five small hearts, which are pulsating vessels.
arthropods have an open circulatory system that bathes the internal organs. They have one dorsal vessel that pulsates to keep blood moving

Question 31

What is the circulatory system of vertebrates?

Answer 31

an intricate system consisting of the heart and three types of blood vessels; arteries, capillaries, and veins

• arteries are elastic and muscular. They carry blood from the heart. Arterial blood pressure tends to be high, and blood tends to be oxygenated.(with the exception of the pulmonary artery, which carries blood to the lung)
• capillaries are one cell thick vessels that diffuse nutrients and waste from the blood to the surrounding tissue.
• veins carry blood toward the heart, and are pushed along by skeletal muscle contractions. they are oxygen poor, with the exception of the pulmonary vein which carries bllod from the lung.

Question 32

What is the circulatory system in fish like?

Answer 32

It is one closed loop. Blood goes from the heart to the gill capillaries, where oxygen is picked up. Then it goes to body tissues, become capillaries again, and deoxygenated blood is returned to the heart and pumped back into the gills. oving to capillaries in the gills slows the blod down a lot when it continues on to body tissue

Question 33

What is the circulatory system of amphibians, reptiles, birds, and mammals?

Answer 33

they have a pulmonary circuit that returns oxygenated blood to the heart before being pumped to the sorrounding tissue, leading to a sustained pressure.

Question 34

how do two chambered hearts work? What is their downfall?

Answer 34

Two chambered hearts like those in reptiles and amphibians have one section for taking in blood from both the heart AND lungs, and one section for pumping blood to the rest of the body AND lungs. Its problem is that it mixes oxygen poor blood from the body and oxygen rich blood from the lungs, lowering the quality of oxygenated blood.

Question 35

How does the four-chambered mammalian/avian heart work?

Answer 35

• consists of two halves, one for oxygenated blood and one for deoxygenated blood
• each half has one atrium, one ventricle
• atrium is where blood returns to heart, ventricle is chamber where blood is pumped out.
• oxygen poor blood from the body enters the right atrium, then enters the right ventricle, is oxygenated in the lungs, returns to the left atrium, then moves into the left ventricle and goes into the body

Question 36

What is the pulmonary vein/artery? Aorta? Superior/inferior vena cava?

Answer 36

The pulmonary artery is the artery from the heart to the lungs. The pulmonary veins runs from the lungs to the heart. the Aorta is the largest artery in the body that pumps blood to the rest of the arteries. The superior/inferior vena cava are the two large veins that flow to the heart

Question 37

What causes the heart to move?

Answer 37

The sinatrial node generates an electric pulse, it is located in the heart. This pulse first stimulates the atria to contract, pushing blood into the ventricles. Then the ventricles contract, forcing blood out of the heart.

Question 38

What is the plasma of blood?

Answer 38

• heavily water based, allowing it to contain many dissolved substances
• also contains proteins that assist in blood clotting

Question 39

What are red blood cells?

Answer 39

• have no nucleus or major organelles
• transport oxygen through the blood
• hemoglobin is a protein that binds to oxygen molecules when oxygen concentration is high, and gives it up when concentration is very low

Question 40

what are white blood cells?

Answer 40

• contains phagocytes and lymphocytes that fend off infectious disease
• phagocytes ingest foreign invaders
• lymphocytes target specific invaders
• B cells identify pathogens by producing antibodies that recognize the protein coats of specific viruses or bacteria
• Helper T cells coordinate the immune system by activating other immune system cells
• Killer T cells kill infected cells

Question 41

What are platelets?

Answer 41

• packets of cytoplasm that release the enzyme thromboplastin when in contact with a foreign body
• thromboplastin converts fibrinogen (a soluble protein in blood plasma) into fibrin (a tough, insoluble protein that forms blood clots)

Question 42

What is the lymphatic system?

Answer 42

• The pressure inside capillaries often forces some plasma from the blood into the sorrounding tissue
• the lymphatic system returns this fluid into the circulatory stsem via lymph capillaries, which converge into larger lymph vessels, and then ultimately the subclavian vein
• the spleen, tonsils, and many white blood cells fight off invaders that often come in through the lymphatic system.

Question 43

How do different orders respirate?

Answer 43

• simple cnidarians exchange gas through simple diffusion
• annelids also have diffusion, but the skin must always be moist
• insects and arthropods have trachae (hollow, branched tubes) that penetrate deep tissue.
• vertebrates are more complex. Fish have gills that maximize surface area
• terresterial vetebrates have lungs. In amphibians, lungs are one large sac
• in mammals, lungs have milllions of tiny alveoli which increase surface area and absorptive power.
• birds have air sacs that maintain a constant, unidrectional flow of air accross lung surfaces.

Question 44

How is PH regulated

Answer 44

the respiratory system regulates it

• breathing faster will increase PH by getting rid of acidic carbon dioxide. Breathing slow will do opposite
• the carotid artery has a receptor that transmits ph information to the medulla oblongata of the brain, which corrects breathing

Question 45

What is the Nephron

Answer 45

a tubule that consists of a cluster of capillaries (called glomerulus), sorrounded by the bowmans capsule.

• the bowmans capsule leads into a long tubule that ends in a collecting duct, which emptys into the central kidney cavity (the renal pelvis) which connects to the ureter, which carries urine to the bladder.
• a kidney is made of millions of nephrons

Question 46

How do nephrons filter blood?

Answer 46

• blood is squeezed through cappillaries, and pressure is so high that the liquid portion goes through a sieve into the Bowmans capsule
• From Bowmans capsule, liquid enters proximal tubule. Important molecules are pumped back into the blood, since they don’t need to be excreted
• liquid enters loop of Henle, which filters out water and salt, leaving mainly urea and waste
• distal tubule takes in hydrogen/potassium inos from blood for excretion, and does more filtering of water/salt
• collecting duct controls water filtration. If body has little water, antidiuretic hormone makes collecting duct walls permeable to water, and water goes back to blood.

Question 47

How do different orders move?

Answer 47

• simples animals propelled by cilia
• cnidarians have contractile fibres that propel them
• earthworms have a hydrostatic skeleton (muscules in circular rings that can get bigger, moving a segment of warm, or smaler)
• arthropods have muscles that connect to exoskeleton
• vertebrates have hard endoskeleton, made of bones (calcium, phosphate salts, and collagen fibers), that allow nerves/blood vessels to pass through in a central canal to embedded cells. Store calcium+produce bloood
• and cartilage, which is firm but flexible. Has no blood vessels or nerves, and takes a very long time to heal.

Question 48

What is the muscular system?

Answer 48

• skeletal muscles are involved in voluntary movement
• smooth muscle is found in internal organs like intestine, involuntary
• cardiac muscle is involuntary, make up heart

Question 49

How does a muscle contract?

Answer 49

• actin protein and myosin are arranged in units called sarcomeres
• long actin filament extends from end of sarcomere to middle, not quite touching
• myosin are in between actin
• sarcomere end where actin is attached is called Z line
• When muscle is stimulated to contract, myosin pulls on actin filaments, which pulls z line together and contracts sarcomere