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195 Cards in this Set

  • Front
  • Back
Diffusion rate relationship with distance
Diffusion rate across a given distance is proportional to the square of the distance
Evolutionary solutions to slow diffusion rate
1) small and/or thin bodies
2) internal circulatory systems, transporting fluid
3 basic components of circulatory systems
Circulatory fluid
Set of tubes
Muscular pump
Functions of circulatory system
-transpo respiratory gases, nutrients, metabolic wastes, hormones and heat
-body defense and repair
-hydrostatic skeleton
Open circulatory systems
-vessels open into cavity
-hemolymph, blood + intercellular fluid
-hemolymph pumped through sinuses surrounding organs, by heart
-hemolymph drawn back into circulatory sys through ostia
-arthropods and molluscs
Close circulatory systems
-blood confined in vessels
-vessel hierarchy
-unidirectional blood flow
-in some invertebrates, all vertebrates
Types of pump
1) simple collapsible, surrounded by muscles
2) peristaltic pump, vessels have contractive property
3) chamber pumps, hearts
Invertebrate circulation
Direct diffusion
-simple body plan
-gastrovascular cavity
-cells bathed in fluid
Active transpo
-many cell layers
-circulatory fluid
-set of tubes
-pump
-open or closed
Vertebrate circulation
-closed cardiovascular sys
-2, 3, or 4-chambered heart: 1 or 2 atria receives blood, 1 or 2 ventricles pump blood out of heart
-arteries carry ox blood away from the heart, send deox blood to gills/lungs
-veins return blood from tissues to heart, carry ox blood to heart from lungs
-capillaries, thin-walled vessels, site of diffusion of materials
-single or double circuit
Evolutionary trends in vertebrate cardiovascular sys
-# of heart chambers, separation of ox and deox blood
-heart contractile power
-blood pressure increase
-single to double circuit
-efficiency of flow and diffusion
-complexity
-represent more active lifestyles and larger body size
Fishes circulatory system
-2-chambered heart
-single circuit
-high P @ gills, low P @ tissues
-low blood P & slow blood flow @ capillaries for diffusion
Double circulation
-double pump heart, more pressure
-O-poor and O-rich blood pumped separately
-amphibians, reptiles, and mammals
Amphibians circulatory system
-3-chambered heart (2A+1V)
-double circulation (pulmocutaneous and systemic)
-ventricle ridge, ~10% mixing
-underwater, blood flow to lungs nearly shut off, most of blood flows to skin
Reptiles circulatory system (x birds)
-3-chambered heart (2A-1V)
-4 in crocodiles, underwater blood diverted from pulmonary circuit to systemic
-double circulation (pulmonary and systemic)
-partial septum, less mixing
Birds and mammals circulatory system
-4-chambered heart (2A+2V)
-full septum
-double circulation
-high blood P and V and flow rate to tissues
-endothermy permitted (enhanced O2 delivery and waste removal, higher E capacity)
-convergently evolved
-deox blood into RA->RV->lungs->oxblood to LA->LV->body
Cardiac cycle
Rhythmic cycle of heart contractions and relaxation
DIASTOLE: relaxation
SYSTOLE: contraction
-lasts 0.8 sec for typical human at rest, 72 bpm
Cardiac valves
Prevent backflow and mixing of blood
ATRIVOENTRICULAR: between A & V
SEMILUNAR: output of V
Control of heart rhythm
-cluster of AUTORHYTMIC cells generate rhytmic heart beat, set rate and timing of contraction
-electrical cell cluster, SINOATRIAL node/pacemaker, in wall of RA
Veins and arteries, tissue layers
Arteries and veins, 3 tissue layers
-outer layer: connective tissue with elastic fibers
-mid layer: smooth muscle, elastic fibers
-inner layer: smooth epithelium
-lumen
Arteries: thick and elastic to resist and maintain blood P
Veins: thinner, under lower pressure
Capillaries
-inner endothelial layer
-facilitates diffusion
-unidirectional flow
-beds in brain, heart, kidneys and liver always full of blood
-blood supply in other tissues varies
Blood pressure
Systolic pressure > Diastolic blood pressure
Exchange of materials and gases in capillary beds, differential pressure
-fluid containing solutes moves in and out via clefts between epithelial cells as result of differential between blood P and osmotic P of interstitial fluid
-differential between blood P and osmotic P of interstitial fluids favours loss from inflow of capillary and fluid recovery @ end
Fluid not recovered by capillaries...
...is returned to the circulatory system as lymph via the lymphatic system
Composition of mammalian blood
55%PLASMA
-water
-ions
-proteins
-substances transported by blood
45%CELLULAR CMPNTS
-erthyrocytes (O and CO2 transpo) R
-leukocytes (immunity) W
-platelets (blood clotting)
4 steps of gas exchange
Ventilation
Gas exchange
Circulation
Cellular respiration
Components of respiratory systems
Specialized ventilatory structures: carry air or water over gas exchange surfaces
Specialized respiratory (gas exchange) surfaces: large moist SAs, well vascularized
Fick's law of diffusion
Rate of diffusion =
[K*SA*(P1-P2)]/D
PARTIAL PRESSURE
The pressure exerted by a particular gas in a mixture of several gases
Diffusion of respiratory gases
O2 higher in enviro than in cells, tends to move into cells
CO2 opposite
Composition of the atmosphere
21% oxygen
78% nitrogen
0.03% carbon dioxide
0.93% argon
Behaviour of oxygen in air
-relative O2 content of air remains constant at all altitudes
-fewer O2 molecules at higher altitudes
-atm P decreases with increasing altitude--> O2 availability decreases
-partial pressure of O2 decreases with altitude--> rate of O2 diffusion into body decreases
Behaviour of oxygen in water
-solubility of O2 in water < in air
-water holds 30X less O2 than air
-respiration more energetically expensive in water
Factors affecting gas diffusion into water
-basic solubility: less in water than air
-temperature of water: cold water holds more O2
-presence of other solutes: sea water, more solutes--> less O2
-partial pressure: high atm P increases diffusion of gas from air to water
-surface area of water
-turbulence of water surface
Gills in invertebrates
Outfoldings of the body surface in direct contact with water
-increase respiratory SA
-thin epithelium
Gills in fishes
-evolved independently from (analogous) gills of invertebrates
-water pumped through mouth and over gills by coordinated movements of jaws and opercula (one-way flow)
-4 gill arches (filaments and lamellae) with capillary beds
-counter-current exchange: water flow over lamellae and blood flow in capillaries in opposite directions, diff in partial P remains high--> max rate of gas diffusion
Tracheal system
Network of air sacs and branching air tubes
-terrestrial arthropods
-spiracle openings lead to tracheae to interior tracheoles to cell surfaces
-spiracles close to stop water loss
-gas diffusion and ventilation
-separate from open circulatory system carrying nutrients and wastes
Pulmonary vein vs. artery
-pulmonary vein carries O2
-pulmonary artery carries CO2
Ventilation in amphibians vs. mammals
Amphibians
-positive P
-PUSH air into lungs with floor of mouth
Mammals
-negative P
-PULL in air and PUSH out by changing lung V
-inhalation: diaphragm contracts down, chest expands (V increases)
-exhalation: diaphragm relaxes up, chest contracts (V decreases)
Ventilation in birds
-lungs + 8-9 air sacs
-unidirectional air flow
-gas exchange on inhalation and exhalation
-chest and air sacs don't compress at the same time
Control of breathing in humans
-involuntary, brain stem control
-increases during exercise and at higher altitudes
Respiratory pigments and gas transpo
-O2 not very soluble in blood, needs carrier molecule for transpo
-hemocyanin: molluscs and arthropods
-hemoglobin: most vertebrates, carries 4O2
-most COs dissolved in blood plasma
OSMOREGULATION
Homeostatic process regulating solute concentrations and balances gain and loss of water in body
Marine organism osmoregulation challenges
-lower internal [solute] than enviro
-lose H2O by osmosis, gain salts when drink seawater
-tend to shrink/shrivel
Freshwater organism osmoregulation challenges
-higher internal [solute] than enviro
-gain H2O by osmosis and lose salts by diffusion
-tend to swell
Terrestrial organism osmoregulation challenges
-lose H2O by dessication/evaporation
OSMOLARITY
Solute concentration of a solution
Osmotic strategies
OSMOCONFORMER
-body fluids isoosmotic with enviro
-regulation of particular ions
-marine habitats
OSMOREGULATOR
-osmolarity of body independent of enviro
-E investment
-all freshwater and terrestrial animals
Types of osmoregulators
Hypo-osmotic regulators
-lower body fluid osmolarity compared to enviro
-face dehydration
-actively take in ions and H2O
-marine bony fishes and air-breathing marine vertebrates
Hyper-osmotic regulators
-osmolarity of body fluids higher than that of enviro
-problems: H2O gain and ion loss
-discharge excess H2O and retain ions
-freshwater fishes, freshwater invertebrates, amphibians
Marine invertebrate osmoregulatory strategy
-osmoconformers
-some active transpo of ions
Marine vertebrate osmoregulatory strategy
-hypo-osmotic regulators
-lose H2O, need to take in more than is lost
Marine bony fish osmoregulation
-osmotic water loss through gills
-drink seawater
-excrete excess salt through gills and urine
-small amnts of urine
Marine shark osmoregulatory strategy
-high [urea] and [trimethyl-amine oxide], protects proteins from urea damage
-urea and TMAO raise osmolarity of body fluids to slightly higher than that of seawater
-functionally osmoconformers
-don't drink seawater
-small amnt of seawater enters by osmosis and eating
-excess salt excreted by kidneys and rectal glands
Freshwater animal osmoregulatory strategy
-lower [solute] than marine animals
-hyper-osmotic regulators
-gain H2O by osmosis, lose salts by diffusion
-drink little H2O
-large amnts of dilute urine
-salts obtained in food and active uptake across gills
Euryhaline aquatic animal osmoregulatory strategy
Can survive large fluctuations in external osmolarity
-osmoconformers OR osmoregulators
-ex. migratory fishes, inter-tidal animals
Stenohaline animals
Can't tolerate substantial changes in external osmolarity (opposite: Euryhaline animals)
Animals in temporary waters osmoregulatory strategy
ANHYDROBIOSIS: entering a dormant stage when habitats dry up
-ex. TARDIGRADES
Terrestrial animal osmoregulatory strategy
Avoiding risk of dehydration
-body coverings
-behaviour: nocturnal, eating H2O-laden foods
-metabolism: use water from CR, reduced urine
Transport epithelium
One or more layers of specialized epithelial cells that regulate solute movement
-typically function as counter-current exchangers
-gills, nasal salt glands
Ammonia
Primary nitrogenous waste product from breakdown of proteins and nucleic acids
-very toxic to cells, must be removed
-excretion requires a lot of water
-can be converted to less toxic forms to conserve water
-excreted across body surface by diffusion, or through gills, to enviro
Forms of nitrogenous waste products
Ammonia-ammonotelic animals
Urea-ureotelic animals
Uric acid-uricotelic animals
Urea
-energetically expensive to convert ammonia to urea in liver
-soluble in water, 100,000 times less toxic than ammonia
-excretion requires less water
-urea carried in blood to kidneys, then excreted in urine
-mammals, adult amphibians, elasmobranch fishes, some molluscs
Uric acid
-largely insoluble in water
-least toxic
-adaptation for life on land
-more energy required to produce
-terrestrial insects, land snails, reptiles
Basic excretory process
Produce filtrate by pressure-filtering body fluids and modifying filtrate before excreted
Key functions of most excretory systems
Filtration
Reabsorption
Secretion
Excretion
Protonephridia
Network of branching internal dead-end tubules connected to external openings
-flame bulbs cap branches of each, cilia draw H2O and solutes from interstitial fluid into the tubules
-filtrate moves down tubule, most solutes reabsorbed
-tubules empty via nephridiopores
-very dilute urine
-osmoregulation
-ammonia diffuses across body surface
-mainly in flatworms
Metanephridia
-pair in each segment, immersed in coelomic fluid, open internally to coelom via nephrostome
-capillary network surrounds
-ciliated funnel draws in coelomic fluid into collecting tubule then bladder
-filtrate through tubule, transport epithelia reabsorb most solutes into circulate blood
-nitrogenous waste remain in tubule, excreted to outside
-dilute urine excreted via nephridiopore
-osmoregulation and excretion
-in most annelids
Malpighian tubules
Dead-end tips immersed in hemolymph to openings into digestive tract
-transport epithelium lining secretes solutes from hemolymph into tubule lumen
-water follows solutes, fluid to rectum
-most H2O and solutes recovered by transpo epithelia
-nitrogenous waste (uric acid) eliminated with nearly-dry feces
-H2O highly conserved
-osmoregulation and excretion
-terrestrial arthropods
Vertebrate kidneys
-supplied with blood by renal artery, drained by renal vein
-ureter=collector duct for urine, both drain into urinary bladder
-urine expelled from bladder to outside via urethra
-2 distinct regions: outer renal cortex, inner renal medulla- jointly contain the nephron
-excretion and osmoregulation
Nephron
-span renal cortex and medulla
-Glomerulus, proximal tube, loop of Henle, distal tube
-types: cortical, short loop in cortex (85%), juxta-medullary, long loop in both regions (15%)
-collecting duct carries filtrate (urine) to renal pelvis, drained by ureter
-1 million/kidney
Counter-current exchange in nephron
-loop of Henle, collecting ducts, and blood capillaries
-osmotic gradient between filtrate, interstitial fluid, and blood
-maximizes urea excretion and reabsorption of water
5 steps from blood to urine
1) proximal tube reabsorbs salt and water
2) descending loop permeable to water, water out of tubules by osmoses
3) ascending loop, permeable to salt- salt diffuses out in lower loop, actively transported out in upper loop
4) distal tube regulates pH and K+ and salt []
5) collecting duct permeable to water, in upper duct NaCl removed from filtrate by active transpo and in lower duct some urea diffuses out of filtrate--> osmotic gradient --> H2O loss from filtrate by osmosis --> highly concentrated urine
Homeostatic regulation of urine volume
-V and O of urine depend on external conditions
-ADH produced by hypothalamus, stored in pituitary gland- counters water loss
-osmoreceptor cells in the hypothalamus monitor blood osmolarity and regulate ADH release
-increased blood osmolarity--> increased release of ADH--> increased permeability of membranes to water
-more water reabsorbed, less urine, blood osmolarity reduced
Marine bony fish kidney adaptations
-hypoosmotic bodies
-small glomeruli for low filtration rates--> little urine and little H2O loss
Freshwater bony fish kidney adaptations
-hyperosmotic bodies
-high density of nephrons for high filtration rates-->large amnts of dilute urine
Amphibian kidney adaptations
On land, reabsorb water from urinary bladder to conserve water
-underwater, kidney function like freshwater fishes
Birds and reptiles kidney adaptations
Birds: short loops of Henle BUT uric acid excretion
Reptiles: cortical nephrons only, uric acid
-avoid dehydration
Mammals in arid habitats kidney adaptations
-long loops of Henle--> low volume, highly concentrated urine
Aquatic mammals kidney adaptations
-don't face dehydration
-for intentional copious water excretion
-short loops of Henle--> high V dilute urine
Functions that need to be regulated
Moulting
Metamorphosis
Growth
Reproduction
Activity
Metabolism
Behaviour
Homeostasis
Systems of communication and regulation
Endocrine system, chemical signals, slow but long-lasting responses
Nervous system, electrical signals, fast but short-lasting responses
ENDOCRINE GLAND
Ductless gland of endocrine cells that secrete a specific hormone into extracellular fluid then to the circulatory system
-circulating hormone reaches target cell via bloodstream or hemolymph
-hormone elicits specific physiological response in target cells
Endocrine hormones
-chem signals, small amnts, regulatory messages
-specific actions, only target cells respond
-slow but prolonged responses
Nervous system (components, speed, organisms)
-sensory, electrical, and motor neurons
-fast response, short duration
-in all animals
Endocrine system (components, speed, organisms)
-endocrine glands and hormones, circulatory system, target tissues
-slow but pronged responses
-in vertebrates and some invertebrates (annelids, molluscs, insects, crustaceans)
How nervous system and endocrine system are linked
Neurosecretory cells: specialized neurons which secrete neurohormones that diffuse from nerve cell endings to bloodstream to target cells
-ex. ADH
Hormone classes
Water soluble
-peptides and amines
-can't pass through membranes
-receptors on plasma membranes
Lipid soluble
-steroids and amines
-can pass through membranes
-receptors within the cell
Endocrine hormone pathway
stimulus --> endocrine secretes specific hormone --> target cell via blood stream, interacts with receptors--> signal transduction --> physiological response
Neurohormone pathway
sensory neuron receives stimulus --> stimulates neurosecretory cell --> secretes neurohormone --> travels to endocrine target cell via blood stream, interacts with receptors--> endocrine cell secretes endocrine hormone--> blood stream and target cells--> signal transduction--> physiological response
Homeostasis and glucose levels
High glucose levels
-pancreas beta cells release insulin
-body takes up more glucose, liver takes up glucose and stores as glycogen
-glucose levels decline
Glucose level falls
-pancrease alpha cells release glucagon
-liver breaks down stored glycogen and releases glucose
-blood glucose levels rise

-islets of Langerhans: regions of pancreas with endocrine cells
HORMONE CASCADE PATHWAY
Hormone can stimulate release of series of other hormones, last one actives non-endocrine target cell
-usually regulated by negative feedback
-ex. thyroid hormone release- hypothalamus--> anterior pituitary--> thyroid gland
Insect moulting and metamorphosis
-INSTARS: growth stages, separated by moults
-when metamorphosis occurs, moults stop
-energy channeled into gamete production
-moulting and metamorphosis under hormonal control
Moult process
-old cuticle loosens
-soft cuticle forms beneath
-old cuticle shed
-body grows
-cuticle hardens and growth temporarily stops
Moulting and metamorphosis hormones
Prothoracicotropic hormone (PTTH)
-stored in corpus callosum
-secreted by 4 neurosecretory cells in brain
Ecdysone
-secreted by prothoracic glands in thorax, response to PTTH
-triggers moult with PTTH
Juvenile hormone (JH)
-secreted by corpus allatum
-interacts with Ecdysone to control developmental stages
CNS vs PNS
CNS:
-brain/cephalic ganglia
-dorsal spinal cord (vertebrates)
-ventral nerve cord (invertebrates)
PNS:
-nerves and ganglia outside, but connected to, the CNS
Glial cell types
Oligodendrocytes: in the CNS
Schwann cells: in the PNS
-form myelin sheath around axons for lipid barrier, electrical insulation, improve transmission
Information processing within nervous system
1) Sensory input, sensory neurons
2) Integration of info, interneurons
3) Motor response, motor neurons
Reflex arc
Spinal cord can produce reflexes independently of the brain
-REFLEX: body's automatic response to stimulus
-skipping the interneurons in the brain
-predator escape
Electrical properties of the neuron
-all cells have membrane potential (voltage diff across membrane), the membrane is polarized
-interior of neuron more negative
-resting membrane potential ~70mV
Resting membrane potential
-caused by concentration gradients of K+ and Na+
[K+in] > [K+out]
[Na+in]<[Na+out]
-ionic concentration gradients=potential chemical energy
-net negative charge inside
Maintaining resting potential
-Na+-K+ pumps actively maintain gradients, K+ in and Na+ out
-2K+/3Na+
-Ion channels let ions diffuse in and out
Ion channels
-clusters of specialized proteins
-selectively permeable, only K+ or only Na+
-resting neuron membrane: more K+ channels open--> net K+ outflow
-anions not allowed through
Gated ion channel types
Involved in nervous signal generation and transmission
Stretch-gated channels
-open or close depending on mechanical deformation from stretching in muscles detected by sensory neurons
Ligand-gated channels
-in terminal axon end
-open or close depending on neurotransmitter binding
Voltage-gated channels
-open or close depending on electrical charge across membrane
Graded potentials
Changes in membrane potential whose magnitude vary with magnitude of the stimulus, determines how many gated ion channels are open
Hyperpolarization vs. Depolarization of the membrane
H:
-stimulus causes more K+ channels to open--> K+ out
-inside becomes more negative
-decreased likelihood of signal production
D:
-Na+ channels open--> Na+ in
-inside less negative
-increased likelihood of signal production (approach threshold)
Action potentials
-threshold voltage -55mV exceeded by depolarization
-electrical signal travels along axon at constant amplitude and speed
-all-or-none response
-frequency can reflect stimulus strength
5-phase mechanism of an action potential
1) resting potential
2) stimulus causes depolarization beyond threshold
3) ascending AP
4) descending AP
5) hyperpolarization
6) resting potential
AP resting state
-resting potential maintained by ungated channels
-most voltage-gated channels closed
-Na+ inactivation gates are open but closed activated gates don't let Na+ through
AP depolarization phase
-stimulus
-some voltage-gated Na+ activation channels open--> Na+ in and membrane depolarizes
-Na+ inactivation gates stay open and K+ activated gates stay closed
-if depolarization reaches -55mV threshold--> AP
AP rising phase
-increasing depolarization opens more Na+ voltage-gated channels while K+ gates stay closed
-inactivation gates stay open
-more Na+ in, inside more positive
AP falling phase
-AP peaks at ~+35mV
-voltage-gated Na+ channels become inactivated
-voltage-gated K+ channels open, K+ out
AP undershoot
-very high membrane permeability to K+, lots of K+ out
-Na+ activation gates close
-slight hyperpolarization of membrane--> refractory period
-most voltage-gated K+ channels close, resting potential restored
Speed of AP conduction
-increases with axon diameter
-increases with myelination, SALTATORY CONDUCTION: signals jump from node to node where gated channels are
Electrical synapses
-gap junctions, pre- and postsynaptic neurons in contact
-direct flow of electrical current
-rapid stereotypical behaviour
Chemical synapses
-neurotransmitters synthesized and packaged in synaptic vessels @ terminal ends
-neurotransmitters released into cleft as result of AP @ pre-synaptic terminal
-chemical signals=most common signal between neurons
Neurotransmitter action
1) voltage-gated Ca++ channels open--> Ca++ into cell and bind to vesicles
2) vesicles fuse with membrane
3) release neutrotransmitter
4) neurotransmitter binds to ligand-gated channel receptors, Na+ in and K+ out
5) neurotransmitter released from receptors, channels close
Neurotransmitter fate
1) diffuse out of cleft
2) re-uptake
3) destruction
Acetylcholine
-@ neuro-muscular functions in vertebrates
-stimulates skeletal muscles
-may control release of other neurotransmitters
Serotonin and dopamine
Mood, attn, and learning
Endorphins
Relieve pain, sense of pleasure
Effects of drugs on the brain
-can enhance or inhibit mechanism of neurotransmission
-can reduce Ca++ movement
-delay neurotransmitter uptake
-affect dopamine dynamics (mood)
Evolutionary trends in the nervous system
-more interneurons
-more interconnections
-centralization and cephalization
-regional specialization
-more info exchanged
-more efficient exchange of info
Hydra nervous system
Nerve net: series of interconnected neurons
-no centralization
-control over expansion and contraction of gastrovascular cavity
-simple reflex arcs
-sensory and motor neurons, no interneurons
Jellyfish nervous system
-2 nerve nets, one for tentacles, one for locomotion
-motor, sensory and interneurons
-coordination possible
Echinoderm nervous system
-nerves: bundled neurons
-centralization
-nerve ring around mouth
-radial nerves in arms
-mouth and arms operate independently
Platyhelminthes nervous system
-cephalization, superganglia=brain
-longitudinal nerve cords, earliest CNS
-basic pattern for invertebrates
Annelids and arthropods nervous system
-greater cephalization: anterior ganglia fused to form brain
-paired ventral nerve cord
-segmented ganglia off nerve cords at body segments
-CNS connected to body via nerves
-more neurons
Cephalopods nervous system
-most sophisticated invertebrate nervous system
-large brain
-complex, image-forming eyes
-large nerves
-learning and memory
-active predators
Chordates nervous system
-Brain: proliferation and concentration of interneurons at anterior end of nerve cord
-single dorsal hollow nerve cord
-CNS and PNS distinct
-segmented ganglia outside spinal cord (PNS)
-regional specialization in CNS and PNS
-overall complexity increased
Evolution of the vertebrate brain
-relative size of different parts
-in fish, hindbrain is prominent
-forebrain larger in amphibians and reptiles
-pronounced cerebrum in birds
-cerebrum dominates in mammals
-shift of importance from hindbrain to forebrain
Vertebrate brain size scales with body mass
More complex lifestyles--> more complex/larger brains
Brain size and ecology
Species with brains outside expected size based on body mass live in complex societies with well-developed cognitive abilities
CNS of vertebrates
-the brain and spinal cord, both derived from the nerve cord
-nerve cord cavity transform into central canal of spinal cord and brain ventricles
-central canal and 4 ventricles filled with cerebrospinal fluid
-gray matter: cell bodies, dendrites, unmyelinated axons
-white matter: myelinated axons
The brain
-3 embryonic regions: forebrain, midbrain, hindbrain
-regions develop from neural bulges
-regions further divided in more evolved vertebrates
Embryonic brain development
Forebrain
-telecephalon (cerebrum + cerebral cortex)
-diencephalon (thalamus, hypothalamus, epithalamus)
Midbrain
-mesencephalon
Hindbrain
-metencephalon (pons + cerebellum)
-myencelphalon (medulla oblongata)
-from 3 embryonic brain regions to 5
Brainstem
-control of autonomic, homeostatic functions
-coordination
-conduction of info between higher brain centres
-midbrain: receipt and integrating sensory info
-pons: regulates medulla breathing centers
-medulla oblongata: control centers for homeostatic functions
-pons and medulla: coordination
Cerebellum
-body balance and movement coordination
-hand-eye coordination
-learning and remembering motor skills
Diencephalon
Thalamus:
-sensory input to cerebrum
-output for motor info from cerebrum
Hypothalamus
-body homeostasis
-mammal biological clock
-important behaviours
-neurohormone and stimulating hormone production
Epithalamus/pituitary gland
-capillaries generate cerebrospinal fluid
Cerebrum
-2 hemispheres each with gray matter outer covering, internal white matter, and basal nuclei deep inside white matter
-L hemi controls R body vice versa
-hemispheres communicate via corpus callosum
Lateralization
Hemisphere specialization
L: math, geometry, language, logic
R: emotion, creativity, pattern recognition, spatial relationships, non-verbal thinking
Cerebral cortex
-largest most complex part of cerebrum
-high convolution in mammals
-sensory perception, voluntary movement, language, learning, cognition
Cerebral cortex info processing and lobes
Primary sensory areas and association areas
Frontal lobe:
-motor, speech, frontal association area, motor cortex
Temporal lobe:
-smell, hearing, auditory association area
Parietal lobe: taste, speech, somatosensory association area
Occipital lobe: vision, visual association area
Learning and memory
L: modification of behaviour after acquiring new info
M: retention of info in cerebral cortex
-STM: stored info accessed via temporary links between neurons in hippocampus
-LTM: temporary neuronal links replaced with permanent connections within cerebral cortex
PNS
Transmits info to and from CNS and enviro
-12 cranial nerve pairs
-31 spinal nerve pairs
-ganglion at dorsal root of each spinal nerve
-afferent/sensory pathways and efferent/motor pathways
PNS nervous systems
Somatic nervous system
-motor neurons carry signals to and from CNS to skeletal muscles
-voluntary
Autonomic nervous system
-regulates internal enviro
-involuntary
-3 divisions: sympathetic (arousal, spinal nerves), parasympathetic (conservation, cranial and sacral nerves), enteric (digestion)
Functional components of the PNS
Somatic nervous sys: limbs and muscles
Autonomic nervous sys:
-sym&para: lungs, heart, pancreas
-enteric: intestines
Sensation
Converting energy into a change in membrane potential of sensory receptors
-action potentials that reach the brain via sensory neurons
-brain interprets sensations giving the perception of stimuli
The senses
Visiom, hearing, olfaction, gustation, touch
Balance
Detection of temperature and pain
Detection of electromagnetic fields
Sensory receptors
A) specialized neurons that directly detect stimuli and generate action potentials
B) specialized cells that detect stimuli and secrete a neurotransmitter stimulating nearby sensory neurons, generating APs
Sensory pathway
1) perception
2) transduction
3) transmission
4) perception
Sensory transduction
-conversion of stimulus E into another form of E
-opening ion channels in receptor cell
-graded receptor potentials
Sensory transmission
-receptor potential reaches axon hillock, AP generated
-AP may result from sum of receptor potentials for depolarization
-stimulus magnitude proportionate to AP frequency or neurotransmitter amount
Sensory perception/integration
-specialized areas for stimulus integration in brain, sensory association areas
-integration results in perception
Sensory amplification
-transduction of stimuli subject to modification
-stimulus can be strengthened in the receptor cell or in accessory structures
Categories of sensory receptors (5)
1) mechanoreceptors
2) chemoreceptors
3) electromagnetic receptors
4) thermoreceptors
5) nociceptors
Mechanoreceptors
-stimulated by physical deformation by mechanical energy
-bending of cilia increases membrane permability to cations--> hyper or depolarization
-statocysts
-ex. whisker bases
Chemoreceptors
-detect chemicals in external and internal enviro
-General: changes in solute concentrations
-Specific: specific kinds of molecules
-ex. antennae and pheromones
Electromagnetic receptors (4)
-detect various forms of electromagnetic energy
Photoreceptors: stimulated by photons of light
Infrared receptors: detect infrared radiation, body heat of prey
UV photoreceptors: detect UV light
Electroreceptors: local changes in electrical fields, located in dermis
Magnetoreceptors: intensity and polarity of Earth's magnetic field, navigation, magnetite component
Thermoreceptors
-changes in ambient temperature
-heat and cold receptors
-skin and hypothalamus (thermostat)
Nociceptors
-pain receptors, detect noxious stimuli which can damage tissues
-most body areas
-diff groups specialize in detecting pain caused by diff things
-respond to damaged tissue by releasing prostaglandin--> inflammation and more sensitivity to pain
Audition and body equilibrium
Both involve mechanoreceptors that detect motion of particles or moving fluid
Audition
Ability to detect sounds
-sounds= acoustic waves created by fluctuations in pressure in an external medium, cause molecules to vibrate which travel through air or water
Proprioception
Body equilibrium, the ability to detect the position, orientation and movement of the body
-proprioceptors/mechanoreceptors are sensitive to changes with respect to gravity
Audition in invertebrates
Detect sounds with:
Body hairs
Tympanic membrane, vibrations stimulate receptor cells connected to the membrane
Proprioception in invertebrates
Use statocysts with proprioceptors that detect movement of statoliths, located throughout the body
Hearing and body equilibrium in fishes
Controlled by the acoustico-lateralis system comprising of the inner ear/labyrinth and the lateral line
Inner ear:
-fluid-filled canals and sacs with otoliths and neuromasts (no membrane)
-internal
-receives vibrations from the bladder via a series of bones
-far-field sound and body eqbr
Lateral line
-fluid-filled canal below epidermis
-opened to enviro via pores
-containts neuromast hairs that detect changes in water movement
-near-field sound and movement nearby
Amphibians, audition and body equilibrium
Adult phase:
-inner ear similar to fishes
-tympanic membrane
-eardrum vibrations transmitted to body rod causing inner ear fluid and hair cell movement
-ear for sound detection and body eqbr
Larval phase:
-acoustico-lateralis system
-sound detection and body eqbr
Birds, audition and body equilibrium
-complex and highly evolved inner ear, sound detection and body eqbr, structure similar to mammals
-tympanic membrane connected to single bone
-coiled cochlea and semi-circular canals (like mammals)
-importance of bird song
Mammals, hearing and body equilibrium
-most complex ear
-outer ear: pinna, auditory canal
-inner hear, tympanic membrane, 3 bones, oval and round windows, eustachian tube
-inner ear: cochlea, organ of Corti, 2 chambers, 3 semi-circular canals
Sound transduction in the cochlea
-vibration of stages against oval window--> P waves in cochlea fluid
-fluid waves down vestibular canal, back down tympanic canal
-fluid waves vibrate basilar membrane, hair cells stimulated
-neural signals from sensory neurons transmitted to brain via auditory nerve
Mammal body equilibrium mechanisms
-fluid-filled chambers and semi-circular canals involved
-otoliths and hair cells in the chambers
-saccule: detects gravity
-utricle: opening into semi-circular canals, detects fwd and bkwd movement
-semi-circular canals: on 3 planes, neuromasts detect rotation and angular movements
Chemosensory systems
Gustation and olfaction, rely on chemoreceptors whose neural signals are transmitted to olfactory bulb and somatosensory cortex
Chemosensory systems in terrestrial animals, insects, and aquatic animals
TA:
-gustation dependent on tastants
-olfaction dependent on odorants
TI:
-taste chemoreceptors are sensilla hairs on feet and mouthparts
-smell chemoreceptors on antennae
AA:
-no distinction between taste and smell
Gustation in mammals
-chemoreceptor cells: epithelial cells in tastebuds in mouth and throat and on tongue papillae
-5 taste perceptions: sweet, salty, sour, bitter, savoury
-receptor cells specific to flavour molecules
Olfaction in mammals
-receptors are neurons lining upper nasal cavity
-binding of odorant molecules to receptors--> signal transduction--> APs to olfactory bulb
-each neuron has one type of odor-receptor
-neurons of same type communicate with same brain area
Invertebrate simple light-sensitive eyespots
-ocellus in planarians, located in head region
-photoreceptor cells detect light intensity and direction but doesn't form images
-planarians a photonegative
Invertebrate compound eyes
-image-forming organ
-in Arthropoda and some Annelida
-consists of many ommatidia light detectors each with its own lens
-ommatidium sensitive to visible light and UV light
-forms mosaic images
-effective in detecting movement
Invertebrate single-lens eyes
-form images and can focus on objects at different distances
-in spiders, molluscs, some polychaete worms
-camera-like with adjustable pupil
-contractile iris adjusts pupil diameter
-movable lens focuses light on photoreceptor layer
Vertebrate image-forming eyes
-detects visible light and colour and is a single-lens image-forming organ
-broad range of light enviros
-detects light and sends APs to brain visual centres for perception
Vertebrate eye structure
-SCLERA: white outer layer of connective tissue
-CORNEA: transparent sclera part at front, fixed lens
-CHOROID: middle, vascular layer
-RETINA: innermost layer of photoreceptors
-FOVEA: center of visual field, concentration of cones
-LENS: transparent protein disk, focuses light on retina
-IRIS: smooth muscle, controls amnt of light entering
-PUPIL: opening to eye
-CILIARY BODIES: smooth muscles attached to lens by ligaments, makes aqueous humour
-AQUEOUS HUMOUR: water fluid in anterior cavity, nutrients
-VITREOUS HUMOUR: jelly filling posterior cavity, form/volume for eye
Photoreceptors in vertebrate eye
Rods and cones
-each contain visual pigments with a light-absorbing molecule (retinal) bound to a protein (opsin)
Rods
-more numerous
-sensitive to low-intensity light, nighttime vision
-no distinction between colours
-concentrated outside of fovea and retina periphery
-visual pigment: rhodopsin, changes shape when absorbs light
Cones
-less abundant
-distinguish colours, less sensitive to light
-daytime vision
-concentrated @ fovea
-red, green and blue, each have different photopsin visual pigment
-each photopsin has distinct opsin with diff optimal wavelengths for absorption
Processing visual information
Pigmented epithelium protects photoreceptors from light
Photoreceptor cells respond to light photons
Bipolar cells receive neural impulses from rods and cones
Horizontal and Amacrine cells integrate visual info, inhibit distant photoreceptors, before it's sent to the brain
Ganglion cells synapse with bipolar cells, send APs to brain
Neural pathway from receptors to optic nerves
-bipolar neurons synapse with multiple rods and cones (outnumbered)
-bp neurons synapse with ganglion cells with axons travelling to the brain in optic nerve fibres
Neural pathway for vision
Optic nerves carry axons from the retina and cross over at the optic chiasm
Lateral geniculate nuclei on the L and R are integration centres, signals from L visual field to R LGN, signals from R visual field to L LGN
Primary visual cortex integrates neural info and formulates images
Light-dark adaptations
Involves retinomotor changes in the retina
-pigment layer thickness decreases in dark
-cones and rods move away from the pigment layer in the dark, rods come out of the pigment layer
Nocturnal vision adaptations
-large eyes to max amnt of dim light entering
-light-reflecting layer behind retina, increased amnt of light within
-pupil diameter increases, more light entering
Foveal adaptations
-falcons: 2 fovea, for wide-angled vision & depth perception+acuity
-diurnal animals have higher cone concentration than nocturnal animals
Eye placement
Monocular vision: eyes on sides, wide visual field, prey species
Binocular vision: eyes in front, depth perception and visual acuity, predators
3 mechanisms of asexual reproduction
Fission
Budding
Fragmentation
Advantages of asexual reproduction
-don't have to find a mate
-rapid colonization
-in stable environments, locally- adapted genotypes perpetuated
Parthogenesis
Producing offspring from unfertilized eggs
-in invertebrates, haploid offspring but not necessarily clones
-in vertebrates, diploid parthogenic offspring, chromosomes double after MEI
Hermaphroditism
Both sexual functions found in the same individual
-simultaneous or sequential
Disadvantages of sexual reproduction
-sexual females produce half as many daughters, two-fold meiosis cost
-time and energy cost
-risky
Advantages of sexual reproduction
-increased genetic variability
-deleterious alleles masked or removed
-rapid adaptation to variable enviro's