final Flashcards
what are the 5 iono and osmotic regulation categories
- osmoconformers
- marine elasmobranchs
- marine teleosts and chondrosteans
- freshwater fishes and elasmobranchs
- euryhaline and diadromous species
how do osmoconformers regulate
- live in stable environments so dont need to regulate
- are stenohaline
- ionic concentration close to seawater (isosmotic)
- some regulation through urine and slime
how do marine elasmobranchs regulate
- concentration of ions ~1/2 of SW
- osmolality slightly hyperosmotic
- increase osmolality by increasing concentration of organic solutes in the extracellular fluids (urea and TMAO)
why dont marine elasmobranchs need to drink water
osmolality is slightly hyperosmotic so water diffuses into body
how are urea concentrations maintained in marine elasmobranchs
- low gill permeability for this solute (phospholipid concentration)
- presence of a urea transporter for active re-uptake at gills
- special kidney tubules to reabsorb urea
what is the function of TMAO in marine elasmobranchs
- increases osmolality
- counteracts the damage urea does to proteins
how do marine elasmobranchs eliminate ions
- divalent ions removed in urine (urine production very low)
- Na+ and Cl- not eliminated at gills but at specialized organ called rectal gland
- ion concentration in secretion twice that of body fluids
- gills pH regulation
how do marine teleosts and chondrosteans regulate
- ion concentration of plasma and ECF 1/3 of SW (hyposmotic)
- gain ions and lose water
- have to actively drink SW and use active ion transport to take up water (water follows ion movement)
how do marine teleosts and chondrosteans get rid of ions
- gills and opercular epithelial tissues and sometimes skin of head have chloride cells
- efflux of Na+ and Cl- occurs here
- glomerular or aglomerular kidneys excrete divalent ions Mg2+ and SO42-
properties of chloride cells
- mitochondria rich
- on gills, opercular tissue, sometimes skin of head
- basolateral membrane that is highly folded
- tubule system similar to endoplasmic reticulum
summary of osmotic and ionic regulation in seawater teleosts
- water loss over gills and skin
- drink sea water
- active excretion of monovalent ions via Cl- cells on gills
- divalent ions lost in feces and urine
how do freshwater fish and elasmobranchs regulate
- operate hyperosmotically
- constantly gain water osmotically and lose ions by diffusion
- lost ions replaced by food and uptake across the gills
two types of chloride cells in freshwater teleosts
- alpha chloride cells
- beta chloride cells
- third type of mitochondrial rich cell now identified, thought to be a modified pavement cell
what are alpha chloride cells
- found at the junction between primary and secondary lamellae
- thought to undergo differentiation when FW fish migrate to SW
what are beta chloride cells
- found in the open area between secondary lamellae and sometimes on secondary lamellae especially if water is soft
what are peanut agglutinin cells
- or - (move different ions)
- currently debate on which cells are which
- function in Cl- uptake/bicarbonate excretion
- function in Na+ uptake/acid excretion
important difference between freshwater and saltwater fish regulation
- in freshwater fish the same cells are involved in regulating pH and ions
- FW fish have a much higher urine flow to eliminate water
- must ensure they lose as few ions as possible in urine
how do FW fish prevent ion loss through urine
- glomerular filtration
- water enters proximal tubule then distal tubule
- ions are able to leave distal tubule and re enter body but water can’t follow bc its impermeable
- water goes to bladder
how do euryhaline fish regulate
- live in estuarine and intertidal environments
- have ability to cover over their CC with pavement cells to minimize ion loss in hypotonic mediums
- hormone prolactin plays a role in minimizing Na+ loss when salinity drops
what are diadromous fish and the types
- spend part of their life cycle in FW and part in SW
- catadromous: live primarily in FW but migrate to SW to breed
- anadromous: migrate from SW to breed in FW
how do catadromous species regulate
- hormone cortisol upregulates mechanisms that allow adults to survive in a hypertonic environment
- increase in gill chloride cell density, size, and Na+K+ATPase activity
- enhanced capacity to take up ions across the gut to allow water uptake
- increased permeability of the urinary bladder for water retention
how do anadromous species regulate
- adult salmon get a decrease in Na+K+ATPase activity and a change in isoform from alpha1a to alpha1b
- young salmon must return to the sea and transform from a parr to a smolt
- hormones in smoltification process: thyroxine, cortisol, growth hormone
gill functions
- ionic regulation
- pH regulation
- nitrogen excretion
- gas exchange
- in most fish nitrogen excreted in form of ammonia
how is nitrogen excreted across the gills
- form of ammonia as a consequence of protein metabolism
- rapidly diffuses because cell membranes in gills are permeable to ammonia gas
- to maintain gradient for diffusion NH3 is protonated to form NH4+
how is the vertebrate nervous system divided
- central nervous system: brain and spinal cord
- peripheral nervous system: afferent/sensory nerve tracts, motor/efferent nerve tracts, autonomic nervous system
three regions of the brain
- prosencephalon (forebrain)
- mesencephalon (midbrain)
- rhombencephalon (hindbrain)
3 main parts of prosencephalon
- olfactory bulbs
- olfactory lobes (telencephalon)
- diencephalon
olfactory bulbs
primary olfactory centres
olfactory lobes
- integrate/process olfactory information
- cerebrum: decision making
diencephalon regions
- epithalamus
- thalamus
- hypothalamus
epithalamus
- has nervous connections with the pineal gland
- receives sensory inputs from the olfactory region and telencephalon
hypothalamus
- major integratory system of the brain
- controls pituitary function
- major link between nervous and endocrine systems
optic lobe (tectum)
- centre for the integration of visual inputs and other sensory information
- memory/learning
cerebellum
- integrates sensory information and coordinates
- posture, swimming/movements, balance
- most variable brain region
medulla oblongata
- contains nerve fibres from all regions of the cns
- receives sensory inputs/transmits efferent motor impulses
- closely associated with nerves carrying info to and from skin, lateral line, gustary system, and viscera
PNS cranial nerves
0 - terminal
I - olfactory
II - optic
III - oculomotor
IV - trochlear
VI - abducens
V - trigemial
VII - facial
VIII - auditory
IX - glossopharyngeal
X - vagus
types of facial nerves
- superficial
- ophthalmic
- deep
- maxillary
- mandibular
- hyomandibular
0) terminal nerve fibre type
sensory
I) olfactory nerve fibre type
sensory
II) optic nerve fibre type
sensory
III) oculomotor nerve fibre type
sensory and motor
IV) trochlear nerve fibre type
sensory and motor
VI) abducens nerve fibre type
sensory and motor
V) trigeminal nerve fibre type
sensory
VII) facial nerve fibre type
sensory and motor
VIII) auditory nerve fibre type
sensory
IX) glossopharyngeal nerve fibre type
sensory and motor
X) vagus nerve fibre type
sensory and motor
spinal cord
- continuous with the medulla oblangata
- extends down the vertebral column
- has a central canal with grey matter composed of unmyelinated nerve fibres
where do paired spinal nerves arise from
grey matter along the length of the spinal cord
purpose of dorsal branches/roots in spinal cord
carry somatic and visceral afferent (sensory) fibres and some visceral efferent fibres
purpose of ventral branches
- carry somatic (motor) nerves and visceral efferent nerve fibres contributing to the autonomic nervous system
what is the autonomic nervous system composed of
- sympathetic and parasympathetic components
- involved in the control of smooth muscle, heart, and certain glands
types of nerves in the ANS
- pre-ganglionic and post-ganglionic nerves
- final neurotransmitter released can be acetylcholine (parasympathetic) or catecholamines noradrenaline or adrenaline (sympathetic)
- role often antagonistic
what are hormones
chemical compounds released by one tissue that travel in the blood stream before stimulating other tissues
what is autocrine
compound chemical released by a cell which influences that cell’s physiology
what is paracrine
compound chemical released by a cell which influences adjacent cell’s physiology
what is endocrine
compound chemical released by a cell which influences physiology of cells in other organs/tissues ie hormones
what is the pineal gland
- located on dorsal surface of diencephalon
- sensory function: photosensitive
- secretes melatonin (circadian rhythm)
importance of melatonin
- provides the link between photoperiod and hypothalamic-pituitary function and between photoperiod and seasonal gonadal development
what is the pituitary gland
- under hypothalamus
- controls secretory activity of other endocrine glands
- produces hormones that stimulate target tissues
- most complex endocrine organ
- primary link between nervous and endocrine systems
- controlled by hypothalamus
parts of the pituitary gland
- neurohypophysis (Pars Nervosa)
- adenohypophysis
parts of adenohypophysis
- pars intermedia
- pars distalis
parts of pars distralis
- rostral
- distal
difference between adenohypophysis and neurohypophysis
- adeno: produce and release hormones when stimulated by hormones from hypothalamus
- neuro: don’t produce its own hormones but releases ones from the hypothalamus
hormones released from the hypothalamus
- CRH: corticotropin releasing hormone
- AVT: arginine vasotocin
- TRH: thyrotropin releasing hormone
- GnRH: gonadotropin releasing hormone
- GHRH: growth hormone releasing hormone
- GHIH: growth hormone inhibitory hormone (somatostatin)
- PRH: prolactin releasing hormone
hormones released from the neurophypophisis (pars nervosa)
- MCH: melanin concentrating hormone
- AVT: arginine vasotocin
- isotocin (analogous to oxytocin)
hormones released from the adenohypophysis
- ACTH: adrenocorticotropic hormone
- TSH: thyroid stimulation hormone (thyrotopin)
- GTH: gonadotropins I and II (FSH and LH)
- GH: growth hormone
- PRL: prolactin
- SL: somatolactin
- MSH: melanophore stimulating hormone
hormones released by pars distalis
- ACTH: adrenocorticotropic hormone
- TSH: thyroid stimulation hormone
- GTH: gonadotropins I and II
- GH: growth hormone
- PRL: prolactin
hormones released by pars intermedia
- SL: somatolactin
- MSH: melanophore stimulating hormone
why doesn’t the pars nervosa make its own hormones
- it is where nerves from the hypothalamus terminate
- hormones isotocin, arginine vasotocin, and melanin concentrating hormone are released from hypothalamus then enter hypophyseal artery then circulation
purpose of isotocin
- reproductive
- renal
- cardiovascular
- metabolic
- hydroosmotic
purpose of arginine vasotocin
- salt and water balance
- mediates renal water retention
- promotes gill Na and Cl extrusion
- constrictor of vascular and other smooth muscles
purpose of melanin concentrating hormone
- concentrates melanin granules in melanophores
- lightens body colour
purpose of melanophore stimulating hormone
- acts on melanophores to cause pigment dispersal
- fish gets darker
- stimulates melanin production
antagonistic melanin hormones
melanin concentrating hormone and melanophore stimulating hormone
purpose of somatolactin
- maturation/reproduction
- acid-base balance
- control of ion levels
how does the pars distalis release hormones
- produces 6 hormones in response to release of hormones from hypothalamus
- trigger hormones arrive mainly through portal circulation
- most hormones have effects on other endocrine organs - only prolactin has direct effects
purposes of prolactin
- released in response to prolactin releasing hormone from hypothalamus
- wide range of actions such as lipid metabolism and gonadal steroidogenesis
- main role is regulation of water and ion permeability of gills, kidney, and bladder
- decrease in permeability of water, increase ion uptake across gills
anatagonistic hormones regarding ion regulation
prolactin and arginine vasotocin
hormones that work together to regulate Ca
prolactin and somatolactin
thyroid
a diffuse gland scattered around blood vessels in the region ventral to the pharynx
functional unit of the thyroid gland
- follicle
- single layer of epithelial cells that enclose a fluid filled space (colloid)
what do thyroid cells do
- take up iodide and synthesize T3 (tri-iodothyrosine) and T4 (thyroxine) from amino acid tyrosine
- T4 prominent hormone produced
- both stored prior to release
how are T3 and T4 released
- released in colloid bound to glycoprotein thyroglobulin
- secretion and release controlled by TSH (thyrotropin) which is controlled by TRH from the hypothalamus
T4 and T3 function
- T4 is main hormone in circulation
- T4 converted to active form (T3) in peripheral tissues
- growth and development
- metamorphosis
- osmoregulation
- metabolism?
where are interrenal cells located
in the head kidney in close association with veins
main hormones produced by interrenal cells
- teleosts: cortisol, some cortisone and corticosterone
- elasmobranchs: 1alpha-hydroxycorticosterone
how does production of cortisol work
- not stored
- synthesized when interrenal cells are stimulated by ACTH which is controlled by CRH
characteristics of cortisol
- member of the steroid family
- synthesized from cholesterol
- released in response to stress
- primary effects mediated by changes in gene expression
purposes of cortisol
- mineralocorticoid (Na/Cl regulation, chloride cell proliferation)
- mobilization of energy stores (glucose, FFA, protein)
consequences of cortisol
- immunosuppression
- decreased growth
- impaired reproduction
where are catecholamines produced
- chomaffin tissue
- located in head kidney
what are catecholamines
- adrenaline and noradrenaline synthesized from the amino acid tyrosine
- stored prior to release
purpose of catecholamines
- fight or flight response
- released directly into circulation in response to cholinergic parasympathetic nervous stimulation
how do catecholamines work
- bind to receptors on cell surface
- mediate short-term effects aimed at increasing circulating energy substrates and blood oxygen delivery
- rapidly cleared from blood due to costs
effects of catecholamines
- increased ventilation and gill perfusion
- stimulation of Na/H exchange on red blood cells
- release of erthyrocytes from spleen
- increased heart rate and strength of contraction
- increase Ca entry
- increase in blood pressure, vasoconstriction
- release of glucose and fatty acids, increases energy substrates
what is the caudal neurosecretory system
- exclusive to fish
- located in posterior segment of spinal cord
- composed of enlarged neurosecretory cells (Dahlgren cells) that originate in the spinal cord and have swollen nerve terminals that terminate in the urophysis
- urophysis composed of axons and nerve terminal of Dahlgren cells and a network of blood vessels that receive hormones produced
peptide hormones produced in caudal neurosecretory system
- urotensin I
- urotensin II
purpose of urotensin I
- involved in stress responses
- vasorelaxation
- osmoregulation
purpose of urotensin II
- stimulates the smooth muscle of the reproductive tracts
- Na exchange
main hormones involved in calcium homeostasis
- stanniocalcin
- calcitonin
properties of stanniocalcin
- glycopeptide
- produced in corpuscles of stannius (spherical bodies on or in kidney)
- inhibits active uptake of calcium across gills
- inhibits intestinal calcium absorption and promotes accumulation of Ca in bones and scales
properties of calcitonin
- peptide
- produced by ultimobranchial gland (ventral to esophagus)
- minor regulator of Ca levels
- inhibits gill Ca influx
stimulates osteoblast development (bone growth)
properties of stanniocalcin and calcitonin
- hypocalcaemic
- antagonistic to effects of prolactin and somatolactin
how is fish blood volume controlled
- renin-angiotensin system
- natriurectic peptides
what is the renin-angiotensin system
- activated by hypotension, hypovolemia, and osmotic pertubations
- involved in maintenance of ion and fluid balance
renin-angiotensin system hormones
- angiotensinogen
- renin (enzyme)
- ACE (angiotensin converting enzyme
where is angiotensinogen produced
liver
where is renin produced
- kidney tissue
- corpuscles of stannius
- rectal gland of elasmobranchs
where is ACE (angiotension converting enzyme) produced
- gill
- kidney
- number of other tissues
renin-angiotensin system process
- angiotensinogen produced in liver
- renin converts angiotensinogen to angiotensin I
- ACE converts angiotensin I to angiotensin II
- angiotensinase deactivates angiotensin II to angiotensin III
actions of angiotensin II
- increase in blood pressure
- increase in drinking
- changes in renal function
- overall increase in blood volume
what are natriurectic peptides antagonistic to
angiotensin II
what are the natriurectic peptides
- ANP
- CNP
- VNP
where are natriurectic peptides produced
chambers of the heart in response to stretch
effects of natriurectic peptides
- decreased drinking and drinking-coupled salt uptake by gut
- increase extrusion of excess salt at gills and rectal gland
- relaxation of smooth muscle, decrease in blood pressure
- overall decrease in blood volume
pancreas
- exocrine and endocrine
- in some fish large lumps of endocrine pancreatic tissue (brockman bodies) are present
- in other species endocrine pancreas is more diffuse and scattered around the gall bladder, pyloric caecae, and foregut
hormones produced by pancreas
- all peptides
- insulin
- glucagon
- somatostatin
properties of insulin
- produced by B cells
- promotes glucose uptake by tissues
- gluconeogenesis
- fatty acid uptake by liver and lipogenesis
- anabolic - building
properties of glucagon
- produced by A cells
- largely oppose insulin actions
- glycogenolysis
- lipolysis
- catabolic - breaking down
properties of somatostatin
- produced by D cells
- inhibits release of glucagon and insulin
- promotes lipolysis and hyperglycemia
which pancreas hormones are antagonistic
insulin and glucagon, somatostatin and insulin
purpose of polypeptides released from the gut
- control digestive processes
- enzyme secretion
- GI motility
- appetite control
hormones released by the gut
- ghrelin
- secretin
- gastrin
- CCK
properties of ghrelin
- produced by stomach
- stimulates GH release
- stimulates appetite
properties of secretin
- secreted by stomach
- stimulates pancreatic HCO3 secretion into intestine –> raises pH of intestines to receive acidic food
properties of gastrin
- synthesized by stomach epithelium
- stimulates gastric gland secretions and gastric motility
properties of CCK
- synthesized by intestinal epithelium
- stimulates pancreatic enzyme secretion and gall bladder contraction (lipid digestion)
- decreases appetite
why is growth well studied
- good indicator of the health of individuals and populations
- needed metric in aquaculture and fisheries modelling/management
growth characteristics
- net result of anabolic and catabolic processes occurring in an organism over time
- determinate in mammals and birds
- indeterminate in most fish
- fish growth determined by genetic potential
- doesnt happen at a constant rate
- a change in length, or mass, over time
common equation for calculating growth
SGR (%BM/day) = 100(ln final mass - ln initial mass) / days
von bertalanaffy equation
Lt = Lmax (1-e^kt)
- Lt = length at point in time
- Lmax = max length attained by a species
- e = base of natural logarithms
- t = point in time
- k = growth rate coefficient