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Chordate characteristics
Dorsal hollow nerve chord
post anal tail
gill slits
Dorsal hollow nerve cord
allows for increased size of complex nervous system
provides rigidity for muscles to attach - turns into centrum
Replaced by bone in all verts except for lampreys and hagfishes
Gill slits
serve as respiratory function - become lungs or gills
Thyroid gland near pharynx. controls metabolic rate
Subphylum Urochordata
Most aer sea squirts as adults. Have an outer tunic and endostyle and gill slits.
As larvae they have 5 chordate characteristics - but metamorphose when adults
Subphylum Cephalochordata
Amphioxus is the most common
Filter feeders, closed circ. system, segmented muscles
Ancestral to all other species of fishes
Subphylum Vertebrata
carnium of either cartilage or bone
growing endoskeleton
anterior end of nerve cord becomes tripartite brain
when the larvae form a tunicate and develops into a fish
Hagfishes and lampreys
Lack a jaw
Round mouth fishes
feed on dead material
Lampreys are ectoparasites (SW or FW)
Class Chondrichthyes
Cartilagenous fish (Sharks and rays)
Ancestors had bone
Mostly internal fertilization
Oviparous, ovoviviparous, and viviparous species
Isosmotic with SW because of high urea in blood
Big sharks and tuna are warm blooded - why?
will have higher muscle contraction and can swim faster - makes them better predators
Osteichthyes: Bony Fish
Gills usually under operculum
Gills involved in osmoreguation
Blood flow counter to water flow
Sex reversal is common - most are dioecious with external fert. and development
Ray finned fish class
Counter blood flow
Have an operculum which has bony plates attached to a series of muscles - increased resp. efficiency because outward rotation of op. allowed water to be drawn across the gills.
Neutral bouancy attained by:
Swim bladders - gas filled derivative of esophagus - additional means of gas exchange as well
Anadromous vs. catadromous
an-spend adults lives in the sea but return to freshwater to spawn (salmon)
cat-spend lives in freshwater but return to sea to spawn (eels)
Lateral line system
touch reception for detecting wave vibrations in water
Receptor cells: are on the body surface or on canals beneath the dermis
Class Amphibia
use both legs and lungs for gas exchange
require water for reproduction
400MYA started to dry up, many air breathers evolved - needed lungs and double circ. system
legless amphibians
Order Apoda
Tailed salamanders
Order urodela
Frogs and toads
order anura
Amphibia Heart
Have 2 atria and a single ventricle
O2 blood from L. atrium and de. O2 from R. atrium
Spongy ventricle keeps oxygenated blood to head and body and deox. blood to lungs and skin
Spiral valve and low pressure in PC artery helps separate the blood
Class Reptilia
Amniotic egg - to free animals from H20
Snakes, lizzards, turtles crocidiles
Dry scaley skin resists desiccation
4 chambered heart - 2 A, 2V - allows for shunting when animals dive
Many release toxins when biting - neurotoxins or hemorrhagic toxins
Crotalid snakes have pit organs which are heat sensors
Most are oviparous but some are viviparous
Neurotoxin vs. hemorrhagin
Neuro - acts on the nervous sytsem
Hemorrhagin - breaks down red blood cells and blood vessels
have remained unchange for 200M years
Secondary palate that enables breathing and eating at same time
Only reptile that has a completely divided ventricle
Class Aves
Endotherms - warmblooded
Feathers - bird feathers and reptile scales are homologous, aerofoil provides lift
Contour, filoplume, down
countour - provides shape that gives wing it's look
filoplume - inside between contour and skin
down - when insulation is needed
Respiratory system of birds
Central lung with air sacs attached - tubules called parabonchii
air sacs allow for unidirectional flow of air through lungs
Blood flows counter to air so extraction is very efficient (O2 extracted in inhalation and exhalation)
Excretory system of birds
excrete uric acid - cuts down on water loss and is non-toxic inside the egg
Orbital salt glands - enable marine birds to drink sea water and eliminate excess salt
Flight of birds
Shape of wings eveolved for different types of flying
Lift provided by aerofoil shape of wing
Daily torpor (Hummingbird)
Process of cooling down body temperature at night to conserve energy - because they are so small and lose heat through body (highest metabolic rate, body temp -42)
Bird Migration
Driven by abundence of food and lack of predators
Navigation by sun, stars, and internal magnetic compass
Stimulus for gonadal development is usually day length - shrivel up when not in breeding season
Class Mamalia
Hair and mammary glands are common feature
Pelage (fur coat) - 1. soft underhair for insulation, 2. gaurd hair for protection against wear and colouration
Endotherms - warm blooded, maintain a constant body temp by trapping produced heat inside*
Sebaceous glands - water proofing
Arrecotor pilli muscles
True horns found in family
Bovidae - hollow sheaths with keratinized epidermis
Used for fighting and protection
Antlers found in family
Cervidae - shed annualy
Scent glands
produce pheromones to mark territories or to let the opposite sex know that they are in "heat" which is estrus
all endothermic, but some hibernate (sqirrels,bats) some undergo torpor (bears)
Flight and echoocation
Bats have skin between their digits and no feathers - navigate by echolocation (can hear 150,000 cucles/min (we only hear 20,000) - use this to hone in on where prey is and increase rate as get closer
Bat order
Reproduction of Mammals
three paterns: montremes, marsupials and placentals
egg layers (like palatypus)
have a marsupium
have a pouch and can have three kids on the go at a time - one on "high test milk" on outside, young kangaroo is born at the size of a bumble bee - migrates through fur into pouch and fuses onto nipple and grows on low test milk -
As soon as it gets into pouch signals mother to get pregnant again but this new one does develop - survival mechanism
have placenta to nourish developing young
Either have estrus cycle or menstrual cycle
long gestation period
Estrus cycle
female fertility restricted to a specific time during a periodic cycle
Menstrual cycle
Only old world monkeys and humans menstruate
Heart of mammals
like birds have a 4 chambered heart - complete double circulation
2 kidneys and excrete urea as the N-waste produce
Monkeys Apes Lemurs and Humans
order primates
Order cetacea
Beavers, mice
Order rodentia
Order chiroptera
Dogs, wolves, bears, cats
Order carnivora
Humans and ovulations
there is no visible external indication of when females are ovulating - this is because it is very dangerous to the woman and don't always want to get pregnatn
Maintaining constant internal body conditions (constant temp, pH, Calcium, glucose levels)
Marine invertebrates are in osmotic equilibrium with their environment (conform to osmotic potential around them)- live in stenohaline environments (constant salt conc.)
show some degree of regulation - live in euryhaline habitats (variable salt conc.)
Fish osmotic regulation
FW are hyperosmotic (higher conc. than surroundings) - actively take up salts by gills and produce dilute urine
SW are hypoosmotic to SW - drink SW and excrete salts and save H2O
are isosmotic with their environment - obtains urea in blood which functions liek osmotic particle to retain osmotic potential - osmoconformers
Amphibian osmoregulation
water enters through skin - produce copius amounts of dilute urine and actively take up H2O across skin
All amphibians live around FW
Kidney nephron designed to filter lots of water - many glomeruli
Osmotic concentrations
Human urine
Rodent urine
salt water
Fresh water
Fresh water - 0
Fish - 250
Humans - 300
SW - 900
Human urine - 1200
Rodent urine - 6000
Terrestrial animals
face the problem of desiccation
lose water through respiration, urine, evaporation and through urine and feces
Gain water by drinking or by metabolic water (kangaroo rat)
Kidney adapted to conserve water
Kangaroo rat vs. humans
Kangaroo - no water from drinking, 90% from metabolic water
Human - half water from drinking and half from food
Kangaroo - lose most from evaporation
Humans - lose most from urine
Vertebrate kidney functions
Kidney filters the blood of almost everything but large molecules (red blood cells and proteins) and reabsorbs the good stuff and excretes the unwanted material
Also functions to conserve water so we can produce urine 4x as concentrated as blood
filter, where urine formation begins
Kidney sequence
Filtration - reabsorbtion - secretion - excretion
Most important structure in regulation blood pressure
Kidney - by regulating how much water is excreted
Number of nephrons in kidneys
1.25 in each, 2.5 mill in total
In proximal convaluted tubule - where 80% of filtrate is reabsorbed
Produce 180L of glomerular filtrate per day, excrete 1.5L
most of filtrate is reabsorbed back into the kidney tubule
some substances (H+) are secreted from the blood into the tubules to be excreted
Secretion = the movement of a substance from one part of the body to another part
Going from the body to the outside
Loop of Henle
Water reabsorbtion from the collecting duct is the function
only birds and mammals have have loop so only they can produce urine more concentrated than blood
vasa recta = pores
Water conservation
water passing through colecting duct is reabsorbed by salt in blood and transported away by vasa recta
Pores are opened by the hormone ADH
Open pores - water conserved
anti diuretic hormone
release is inhibited by ETOH and caffeine
Ectotherms and Endotherms
Ectotherms - Body temp determined by the environment
Endotherms - maintain constant body temp by using internal heat from metabolism
Adaptations to heat and cold
Shivering - thermogenesis
Hibernation and torpor
Muscular movement
contractile proteins can change form to elongate or contract
composed of microfibrils that contract with ATP
Skeletal muscle
striated muscle
organized into budles
contract quickly - fatigue rapidly
Smooth muscle
not stiated
contracts slowly, resistant to fatigue
involuntary - autonomic nervous system
Cardiac muscle
only in heart
striated, involuntary control
Structure of filaments
Each myosin filament has many myosin molecules
Each actin filament has two strands of actin, tropomyosin and troponin
Sliding filament hypothesis
during contraction, actin and myosin filaments come together by cross bridges - act as levels to pull filaments past each other
Z-lines are pulled closer together as contraction continues
Control of contraction
in response to nerve stimulation
motor nuerons - located in spinal cord
Each neuron has an acton which subdivides into terminal nerve branches - goes to a sinlge muscle fiber
Unstimulated muscle vs. stimulated muscle
un - tropomyosin surrounding actin filaments prevents myosic heads from attaching
stimulated - upon electrical depolorization, Ca released from SR which bind to troponin
Excitation contraction coupling
Ca binds to troponin
active sites exposed
myosid heads bind to active site - CB formed
Energy causes myosin head to move - CB detached
release of ATP releases myosin head and allows another to bind
some inverts have a cuticle (exoskeleton) covering the epidermis. Verts have an epidermis covering the dermis
has blood vesels and bony bits (like scales)
Claws, beaks, and horns are all epidermal bits that have been keratinized
Keratinized cells
resistant to abrasion and water loss - important for reptiles
Epidermis functions:
gas exchange surface
ion exchange surface
Active transport
use energy to obtain something AGAINST a concentration barrier - ATP
Structural colours
pigments that reflect certain wavelengths (beetles, butterflies)
Chromatophore cells
pigment in center of cell which expands. Most often filled with melanins and carotenoids - when want to change colour lets pigmetn spread throughout cells
What controls expanding of pigments?
1) when sees visual background sends signals (nervous system)
2) hormones - takes longer, melanocyte stimulating hormone
Skeletal systems
Hydrostatic skeletons of earthworms
Rigid skeletons have two types - endo and exo
endoskeleton vs. exoskeleton
endo - provides support from the inside - allows growth without molting (vert)
exo - cuticle on the outside, the only way to grow is to shed (mollusks)
hyaline cartilage is made up of chondrocytes
Very little blood supply and that is why it takes so long to heal
living tissue
Ca laid down in extracellular matrix
highly vascularized
osteoclasts and osteoblasts (PTH and calcitonin)
Osteoclasts and osteoblsts
blasts - build bone matrix
clasts - breaks down bone
PTH - increases Ca in blood
cacitonin - decrease Ca in blood
Circulation and respiration
as animals become large - simple diffusion cannot supply the O2/CO2 exchange or nutrient/waste exchange
therefore developed a circ. system
Open vs. closed circ system
Invertebrates - open circ system - annelids are the exception with closed
Verts - closed circ. system
Mammal vs. Amphibian heart
Amphibians have a single ventricle but have a pulmonary circut and systemic circuit - incomplete b/c have a 3 chamerbered heart
mammals - have both cuirts and in the adult they are separate
The SA node and AV node control heart rate
Impulses are conducted down bundle of his and through Purkinje fibers
Rate of node firing is inherent but modified by nerves that act on nodes
Heart has...
inherent rhythmicity - will keep beating without neural stimulation because of pacemaker
O2/CO2 exchange
Air contains 20x more O2 thand oes water, and O2 decreases when temp of air increases
O2 availability is high on terrestrial env. but can dessicate an animal - tracheal systems eliminate this by delivering O2 directly to cells
decrease H2O loss
Small division increase surface area for gas exchange (alveoli)
Breathing rate controlled by PCO2 and not PO2 - main sensor is medulla
CO2 increase stimulates drop in pH
Disadvantage of lungs
gas is exchanged between blood and air only in alveoli and alveolar ducts - air must enter and exit at the same channel - very inefficient
Carbon dioxide and pH
carbon dioxide + water forms carbonic acid which realses hydrogen ions, making the spinal fluid more acidic and stimulating resp. receptors in the medulla
Pressures and altitudes
Percentages of gases remain virtually unchanged with altitude
total atmospheric pressure changes and therefore partial pressure changes
PO2 and PCO2 delivery
gases are moved by simple diffusion down a partial pressure gradient
PO2 highest in lungs and lowest in the veins
PCO2 is highst in veins and lowest in lungs
Gas Transport
O2 and CO2 transported on respiratory pigments
Vertebrates use haemoglobin which is in the membrane of the red blood cells
Haeme is a matalloporphyrin and globin is a protein
Heme has great affintiy for O2 - amount of O2 affected by shape of molecule
Hb saturation curves
O2 is releases from Hb when in an area with a lower PO2
CO2 and H+ ions shift the curve to the right enhancing delivery to tissues
CO2 uptake and delivery
In the presence of carbonic anhydrase (CA) CO2 is converted to H+ ions and HCO3 ions. CA on the RBC plus in the kidneys, lungs and gills
Most CO2 carried in teh blood has HCO3 ions, and 25% a HBCO2, small amounts of CO2 in solution
control animals activities
rapid, short term communication by nueral mech.
slower, long term by hormonal mech
- they are chemicals released into the body and transported to target cells
Endocrine vs. exocrine
Endo - ductless glands, well vascularized
Exo - release secretions into ducts onto free surface
Mechanism of hormone action
action of hormones on specific cells depends on presence of receptor molecules
hormone will bind to, and activate, only those cellst hat have receptor
Two kinds of receptors
membrane bound - for protein hormones
nuclear - for steroid and thyroid hormones
Membrane bound receptors
Protein hormones bing to receptors on target cell to form complex - which triggers cascade of events in cytoplasm - cAMP is second messenger which influences enzymes
Nuclear receptors
hormones diffuse through membranes and bind to receptors - complex activates or inhibits genes - transcription of enzymes is altered
Invertebrate hormones
in insects, moulting and metamorphosis is controlled by interaction of ecdysone and juvenile hormone
Ecdysone vs. juvenile
acts directly on chromosomes to stimulate a moult
juv - favours retention of larval characteristics - when production hormone ceases then moult
contains neurosecretory cells which secrete releasing hormones - neurohormones leave neurons and enter capillaries to stimulate or inhibit release of hormones from pituitary gland
Anterior pituitary gland
tropic and nontropic hormones
Regulate other endocrine glands
Thyroid stimulating hormones
ACTH stimulates production of steroid hormone
act directly on target tissues
Prolactin prepares mammary glands for milk
Growht hormone affects mitosis, mRNA, metabolism
Posterior Pituitary gland
Two hormones are formed in hypothalamus and are stored in PPG until:
release of oxytocin and vasopressin
Oxytocin release
contraction of uterine muscles during childbirth
Vasopressin release
increase water reabsorbtion in collecting ducts of kidney
Thyroid gland
epithelial cells of gland trap iodine from teh blood and combine it with tyrosine to form:
which promotes grow and development
T3 and T4 in birds and mammals
stimulates metabolic rate by controlled oxygen consumption and heat production
Parathyroid glands
PTH is essential for Calcium
Importance of calcium in the body
formation of healthy bone
required for neurotransmitter release
required for muscle contraction
Adrenal gland
double gland on kidneys
cortex produces: cortisol, adolsterone
medulla produces: epinephrine and norepinephrine
Cortisol and Adolsterone
Cortisol - food metabolism, synthesis of glucose
adolsterone - reabsorbtion of Na from kidneys, secretion of K from kidneys
Epinephrine and Norephinephrine
produced in response to emergencies or strong emotional stress
Exocrine portion: pancreatic juice
Endocrine portion: islets of Langherans
Produces insulin and glucagon
essential for uptake of glucose cells
lowers blood glucose levels
alpha cells
raises blood glucose level
converts liver glycagon to glucose
produced by ovary
development of sex structures
stimulate reproductive activity
with progesterone prepares uterus to receive developing embryo
produced by testis
growth and development of penis, sperm ducts
development of secondary sex characteristics
Types of nutrition
required to maintain complex structures of animals
chemical bond energy released by transforming complex compounds to simpler ones
plants, algae, cyanobacteria
use light energy to fix inorganic compounds
animals, fungi, protozoa
depend on previously synthesized organic compounds
microspheres, ciliate, dinoflagellate
Interplay of organ systems in nutrition
Food is ingested into body - digested into soluble materials - soluble molecules absorbed into circulation - transported to body tissues - assimilated to body tissues - oxygen is transported to body tissues - food is oxidized - excess molecules are stored - unsuitable foods are egested
Feeding on particulate:
Suspension feeding
bivalves: ciliated surfaces of gills draws drifting food particles into siphon
barnacles: cirri snares food particles
copepods: appendages capture particles
sponges: collar cells with flagella
Filter feeding
herring: gill rakers strain plankton
baleen whales: baleen filters out fish
Deposit feeding:
sedentary and tube dwelling polychaetes: tentacles gather detritus that accumulates on substrate
dominant feeding mode of macroscopic animals on the sea floor
important for biotrubation of sedements
Feeding on food masses
predators must locate, hold, and swallow prey
adaptations of molluscs, crustaceans, and insects
molluscs have a radula for scraping food off hard surfaces
crustaceans have mouthparts that enable shredding of food
insects have three mouhtparts to crush, grasp and probe (jaws, long tounges, and sucking tubes)
FAR, bids and mammals adaptations
FAR - use teeth to grip prey, swallow it whole
birds - beaks have serrated edges
mammals - chew food using four different types of teeth (incisors, canines, premolars, molars)
Feeding on fluids of other animals (ectoparasites)
annelids (leeches)
chelicerates (ticks)
crustaceans (ectoparasites)
insects (bed bugs, lice)
chordates (lampreys)
Feeding by direct absorbtion of organic molecules through body:
protozoa (Trypanosoma)
flatworms (tapeworms)
acanthocephalans (endoparasite worms)
Feeding by phagocytosis of particles across cell membranes:
protozoa (amoebae, ciliates)
Intracellular digestion:
Protozoa, sponges
only small particles can be ingested
every cell must be capable of digestion, absorbtion ad assimilation
Extracellular digestion:
alimentary canal
higher animals
digestion of food by radiates and flatworms practice both intra and extracellular digestion
Action of digestive enzymes
enzymes chemically digest food into absorbable units
specific enzymes break down specific classes of organic compounds
Proteins, cabs, lipids
proteins broken down into amino acids
carbs broken down into simple sugars
lipids reduced to glycerol, fatty acids, monoglycerids
Orginization of alimentary canals
reception (mouth)
Conduction (esophogus)
storage and early digestion (stomach-mammals, crop-birds)
grinding (gizzard-birds)
Terminal digestion and absorbtion (small intestine-verts, midgut-insects)
Water absorbtion and concentration of solids (large instestine-verts, hindgut-insects)
Recieving region:
mouthparts, buccal cavity, pharynx, salivary glads, tongue
Salivary glands and tongue
salivary - leech saliva contains anaesthetics, anticoagulants, connective tissue proteases
saliva of herbivores contains amylase
tongue - assists in food manipulation, swallowing, tasting
transfers food from mouth to digestive region (peristalis)
annelids, insects, birds
stores, softens, or ferments food before digestion
Grinding and early digestion
stomach and gizzard
stomach of herbivorous animals contain microbes that help digest cellulose cell walls of plants
Stomach and Gizzard
stomach - provides initial digestion, storage, and mixing
gizzard - action is assisted by stones and grit
Arthropod stomachs
have a hardened lining of chitin or calcium carbonate
Vertebrate stomach
Ushaped tube with glands that secrete proteolytic enzymes
mucous coats and protects the stomach mucosa
Gastric juices are composed of pepsinogen and HCl
Cardiac sphinctor
opens to allow food from esophagus; closes to prevent regurgitation
converts to pepsin at high acidity
enzyme that splits large proteins into smaller polypeptides; present in all verts
caused by the break down of mucous in stomach lining
Digestion in Small intestine
food is released from a churning stomach into duodenum through pyloric sphinctor
pancreatic juice and bile are secreted into duodenum
Pacreatic juice and bile
high bicarbonate so neutralizes gastric acids
- essential because all intestinal enzymes are only effective if contents are of neutral pH
secretes bile into bile duct; drains into duodenum
Gall bladder
stores bile between meals
Bile contains
bile salts that breaks up fat globules for digestion
bile pigments - contain break down products of haemoglobin
salivary glands - saliva
stomach - gastric juice
liver and gall bladder - bile
pancreas - pancreatic juice
small intestine - membrane enzyme
Region of terminal digestion and absorbtion
Verts increase SA for absorbtion by:
increased length (mammals)
spiral folds (sharks)
elaborate intestinal folds (tetrapods)
villi (birds and mammmals)
stomach absorbs only water, alcohol and drugs
food is absorbed in small intestine
simple sugars and amino acids passively or actively are transported into epithelial cells and then into blood capilaries
fatty acids and monoglycerids transported into ER
Large intestine
indigestable food is concentrated by removal of water by epethelial cells
bacteria degrade organic wastes and synthesize some vitamins such as VK
Carbs and Fats
required as fuel for energy
required for synthesis of substances and structures
amino acids are required for specific proteins and other N containing compounds
solvent for body chemistry
major component of all fluids in body
form important structural and physiological components
needed as aninonic and cationic ions
not needed in high abundance
function as coenzymes
required, but in smallamounts in diet
associated with activity of enzymes
Amino acids
8 cannot be synthesized by body and are needed in the diet
diet of grain and legume covers all amino acids
prevalent in diet with high amounts of saturated lipids and low amounts of unsaturated lipids
fatty substances are deposited in artery linings
causes narrowing of passageways
Steps of atherosclerosis
1: tear in artery wall
2: fatty material is deposited in vessel wall
3: narrowed artery becomes blocked by blood clot
3 Basic functions of nervous system
Recieve sensory info (sensory nerves)
Integrate input (brain or spinal cord)
respond to stimuli (motor nerves)
Single vs. multicellular animals
protozoa do not have a nervous system - respond with a single cell
multicell require complex communication mechanisms
Rapid vs long term communication
rapid - occurs by neural mechanisms
long term - controlled by hormonal mechansims
2 Cell types
Neurons and Glial cells
transmit nerve msgs via an electrochemical process
humans have 100 billion in brain
3 parts of neuron
dendrites - recieve info from another cell
cell body - contains nucleus, mitochondria
Axon - conducts msgs
Glial cells
form myelin sheath which surrounds axons of some neurons
basic functional unit of the nervous system
3 Neuron types
afferent (sensory)
efferent (motor)
interneurons (connects neuron to neuron)
Sensory neurons
long dendrites, short axon
connected to sensory receptors: convert stimuli to nerve impulses
Motor neurons
short dendrites, long axon
carry nerve signals from CNS to muscles or glands
Vert. Nerve
nerves are bundles of neurons
How a nerve works
When a neuron is stimulated it begins to generate an electrical pulse - the electrical and chemical change that results travels down the axon - at the end it triggers the release of chemicals (neurotransmitters) that carry the pulse to the next cell
nerve signal
action potential
an electrochemical msg, behaves in the same way in all animals
nerve fiber either conducts the impulse or it does not
signal is varied only by changing the frequency of impulse coduction
the language of the nerve
the higher the frequency, the greater the level of excitiation
Resting membrane potential
Polarized membrane (-ve inside, +ve outside)
inside: high in K+ and protein
Outside: high in Na, Cl
At rest neuron membrane is selectively permeable to K ions, not permeable to Na
resting mem. potential usually aroudn -70 mV
Na-K exchange pump
neuron membrane has low permeability to Na, but some Na leaks through into axon in the resting condition
to maintain negative resting potential -70, Na are pumped out of the cell by Na pumps
Na pumps also move K into axon when Na is expelled, to restore ion gradients
Action potential
a change in electrical membrane potential
very rapid and brief depolarization of the membrane
When an action potential arrives...
Na gates int he membrane open, and Na rushes into the cell, reversing membrane polarity - membrane is depolarized
High speed conduction
conduction speed is +vely correlated with diameter of axon in invertebrates
Vertebrates recieve high speed conduction by interactions of axons with myelin sheaths
Without myelin at the nodes
action potentials would continuously depolarize the axon
Synapses: junctions between nerve cells
neurotransmitters required to cross synaptic cleft (space between to cells)
Development of centralized nervouos systems:
unicellular organisms lack nerves
simplest pattern= nerves of radiates (lack head, impulses spread via epidermis in all directions)
CNS (bilateral organisms)
a concentration of cell bodies that coordinate everything
nerve cord and brain
PNS (bilateral animals)
communication network extending to all parts of the body
sensory and motor nerves
Flatworms, annelids, and verts
flatworms - have ganglia which forms a small brain
Annelids and arthropods - have a ganglion in each segment to control segment muscles
verts - have spinal cord and a highly developed brain
Vert Brains
progressive increase in size of cerebrum
cerebellum is largest in animals whose motor movements are well developed
Sense organs
are specialized receptors that detect environmental status and change
1st level of environmental perception
some form of energy (electrical, mechanical, chemical or radient)
sense organs transform energy into nerve impulses
Types of receptors
classified by location and form of energy
light, thermal
keep animals informed of external environments
recieve stimulus from internal sources
receptors in muscles, tendons and joints: sensitive to cahnges in muscle tension and body position
chemical recpetors
pheromones, taste, smell
mechanical receptors
touch, pain, lateral line, hearing, equilibrium
Chemoreception in unicellular animals
contact chemical receptors (locate food, avoid toxins)
chemotaxis (orientation behaviour)
Chemoreception in metazoans
contact chemical receptors (taste)
distance chemical receptors (smell of olfaction)
highly developed in mammals
guides feeding behaviour
location and selection of sexual partners
synchronization of menstrual cycles
found in mouth, on tongue
taste papilla and taste bud
chemicals interract with microvilli of receptor cells
action potentials are transmitted across synapses to neurons
neurons relay msgs to specific part of brain
Taste bud
clusters of receptor and supporting cells
olfactory endings are in nasal epithelium
nasal epithelium is covered in mucous
olfactory neurons have several cilia portruding into nasal cavity
Smell time line
odour molecules enter nose - bind to receptr proteins located in cilia - binding generates electrical signal - action potential is sent by axons to brain for processing
mechanoreceptors respond to motion - required for feeding, walking, flying, etc
Inverts have tactile hairs
Pacinian corpuscles
mammalian skin pressure receptors
cosist of nerve surrounded by layers of connective tissue
pressure at any point on connective tissue of capsule distorts nerve ending producing an electrical current
strong pressure intitiates an action potential in a sensory nerve fiber
Pain receptors
unspecialized nerve fiber endings
respond to mechanical movement of tissue
respond to damage of tissue and temperature changes
Fast pain
pin prick, hot or cold
direct response of nerve ending to mechanical or thermal stimuli
Slow pain
injured cells release small peptides that trigger pain receptors to initiate an action potential
CNS responds by...
releasing endorphins and enkaphalins to cope with pain
most inverts cannot hear - only crustaceans,spiders and insects can
Outer ea
detects sound waves
funnels them into auditory canal to eardrum
Bones in the middle ear
conduct and amplify sound waves
Inner ear
contains hair cells with fine rows of microvilli
energy of sound waves causes fluid in cochlea to stimulate microvilli of hair cells
microvilli connect with auditory nerve
organ of equilibrium in most vertebrates is in the labrynth (vestibular organ)
3 semicircular canals are filled with fluid - endolymph
when head tilts or moves, fluid moves opposite to direction of acceleration
movement of fluid triggers hair cells in canals to initiate action potential
Acoustico lateralis system of fishes
senses sounds, vibrations, and other displacements of water
2 components: inner ear, outer ear
Inner ear:
sound detection and balance
have a pair of ear stones
hair cells with sensory endings in gelatinous mass (capula)
any disturbance in water bends capula and initiates action potential
crayfish with statolith
balance organ found in animals ranging from radiates to arthropods
monitors gravity and low frequency vibrations
light sensitive receptors = photoreceptors

Deck Info