Animal Physiology Exam 1 Flashcards
Animal Physiology
Integrated study of how biological systems work; Integrates knowledge from all levels of biological organization; Integrates multiple disciplines like biology, chemistry, physics, and evolution
Levels of Biological Organization
atoms, molecules, organelles, cells, tissues, organs, organ systems, organisms
Core of Anatomical Wheel
Nervous and Endocrine System
Outside of Anatomical Wheel; Connects everything
Bloodstream
Other components of Anatomical Wheel
Renal, Cardiovascular, Skeletal muscle, Respiration, Digestion
Two Main Questions in Animal Physiology
- What is the mechanism by which a function is accomplished?
- What is the origin of that function?
Mechanism
Components of living organisms that enable animals to perform
Origin
The evolutionary process that conspired to produce a mechanism; The evolutionary significance of mechanisms; Natural selection is the key process of evolutionary origin
Natural Selection
Increase in frequency of genes that produce phenotypes that raise the likelihood that animals will survive and reproduce
Adaptation
Traits (or physiological mechanisms) that are products of evolution by natural selection
Modes of Natural Selection
Directional, Stabilizing, Disruptive
Directional Selection
Selection favors one of the extreme phenotypes; Mean shifts but the SD/Variance stays the same
Stabilizing Selection
Selection favors the intermediate phenotype; SD/variance changes but the mean stays the same
Disruptive Selection
Bimodal; Selection favors the two extreme phenotypes
What indicates modes of natural selection?
Changes in mean and/or SD
Cells in the internal environment respond to
the external environment to maintain suitable conditions
Conformer
Internal and external conditions are relatively equal (change with each other)
Conformer Benefits
Use less energy
Conformer Costs
Less habitats are suitable for life; lack of optimal functionality
Regulator
Maintains internal constancy regardless of external conditions
Regulator Benefites
Can survive in extreme conditions; More viable habitat options
Regulators Costs
Uses more energy
Salmon Migration
They show temperature conformity when entering a river from the sea. Their body temp changes if the river temp is different than the ocean. They show chloride regulation. The maintain a constant chloride concentrations regardless of the dilute Cl- concentration in the river and high Cl- concentration in the ocean.
Physiological regulation implies that
function occurs best over a specified range of conditions
Claude Bernard
Studied blood glucose levels; 1st to recognize that stability of conditions humans maintain in their blood
Walter Cannon
“Internal Constancy” (Homeostasis); Meaning there is internal stability AND regulatory mechanisms to make adjustments to maintain stability
Homeostasis
Coordinated physiological process which maintain most of the constant states in an organism; Homeostasis is dynamic
Walter Cannon 3 Postulates
- The nervous system preserves the normal conditioning of the body
- The tonic activity of a system can be modulated up and down
- There are factors that have opposing effects = antagonistic controls
Hormone
Endocrine System
Nerves
Nervous System
Negative Feedback Loop
An upstream product or signal of a pathway inhibits and earlier step in the same pathway (Ex: Blood Glucose Control)
Positive Feedback Loop
An upstream stimulus amplifies an earlier response (Ex: Oxytocin)
Physiological Timescales
Time frames in which physiology changes
Response to external environments
Physiological trait changes in response to the external environment; Acute, Chronic, Evolutionary
Changes in Individuals (Often reversible)
Acute and Chronic
Changes in populations (Irreversible)
Evolutionary
Acute
Immediate response; Ectotherm response to temp
Ex: First exposure to hot environment = lower level of energy and endurance
Chronic
Response after long term exposure; Organism experiences an environment for a long period (seasonal changes/variation); Phenotypic plasticity (acclimation (lab) and acclimatization(nature))
Ex: High elevation for a week = increased hemotacrit –> increase in O2 binding affinity
Evolutionary
Longest time scale; Natural selection; Occurs in populations across generations; Adaptations; Irreversible changes in genotype and phenotype
Physics and Chemistry
- Physical properties are linked to function
- Chemical laws govern molecular interactions
- Electrical laws describe membrane function
- Body size influences biochemical and physical patterns
Body size and scaling
More often than not there is a (+) relation between the size and physiological trait; Many traits scale in a systematic way with body size
Isometric Growth
Proportions remain constant; Each dimension is scaled up or down by the same amount (Ex: salamander picture on slides); best seen in terms of anatomical size; 1:1 growth)
Allometric growth
Changes in body proportion with changes in body size; Different rates of growth of different parts; The proportions vary depending on rates at which SA, V, and other physical parameters changes with size (Ex: Best seen in human head size)
Size and SA/V impacts
Thermoregulation, Respiration, Water Balance, Bone and Muscle Structure, etc.
Volume helps determine the weight of an organisms; SA helps determine rate of exchange across surfaces
Larger size
Smaller SA/V Ratio –> slower exchange
Smaller size
Larger SA/V Ratio –> faster exchange
What constrains organisms to certain environements?
SA/V ratio
Allometric Equation
Y=aX^b
Y= variable being measure in relation to size
a= initial growth index (size of Y when M=1)
X= size (mass)
b= scaling exponent
b=1
isometry; no differential growth (Ex: Liver v. Body Mass)
b>1
positive allometry; Y increases at a rate faster than X (Ex: Forelimb v. Body Length)
b<1
negative allometry; Y increases at a rate slower than X (Ex: Head length v. Body Length)
The scaling exponent (b) is only true when
Comparing like dimensions (length v length)
Isometry of head length v. body length
m1/m1, b=1/1= 1
Isometry of head length v. body mass
m1/m3, b=1/3= 0.33
Isometry of surface area v. body mass
m2/m3, b=2/3= 0.67
Scaling
The structural and functional consequences of changes in size in otherwise similar organisms
SA is proportional to
Length^2 and V^2/3
As SA increase, V increases by 2/3 of SA
V is proportional to
Length^3
SA/V Ratio
Smaller objects have larger SA relative to their V than larger objects of the same shape (Smaller objects have larger SA/V ratios)
Larger SA/V ratio means quicker diffusion; Good for O2 absorption, bad for water loss
V increases more rapidly with size than SA
So as size increases the SA/V ration decreases
Logarithmic v. Arithmetic Plots
Looks like smaller differences of log plots; Looks like larger differences on arithmetic plots
Arithmetic scale: 1, 10, 100
Log scale: 0, 1, 2
By plotting a log scale we can asses two important aspects of the scaling relationship
- The slope of the relationship (b): Rate of change in a trait relative to body size
- The proportionality coefficient (a): The y-intercept
Secondary Signal
Substantial deviation from an otherwise reliable regression
Kleibers Law
Metabolic rate scales to the 3/4 power of body mass; Varies with scale of study (Individual vs across species)
Nervous and Endocrine Systems integrate and
coordinate all other functional systems
Basic unit (specialized cells) of the nervous system
Neuron
Neuron Anatomy
Dendrites (synaptic input), Cell Body (integration), Axon (conduction), Pre-Synaptic Terminals (Output)
Nerves
Bundle of neuron axons
Neurons and glial cells make up the
Nervous System
General Neuron Function
Signal –> Action potential travels along axon –> Releases neurotransmitter into Synaptic cleft/gap –> NT bind to receptors on post synaptic cell –> Response
Endocrine Cells
Longer lasting effect; Endocrine cells synthesize and secret hormones into the bloodstream and travels to target cell to evoke a response
Response Loop
Stimulus, Receptor, Afferent Pathway (Sensory), Integrating Center (CNS), Efferent Pathway (Motor), Effector, Response
Functional Classes of Neurons
Sensory Neurons (afferent; PNS), Interneurons (CNS), Motor Neurons (efferent, PNS)
4 Functional Regions of a Neuron
Dendrites
Soma Cell Body
Axon Hillock
Axon Terminal
Neuroglia (Glial Cells; Accessory Nervous Cells)
Protect neurons and help them function; Insulate neurons from one another; Supportive framework for nervous tissue; Involved in impulse transmission (communication)
Types of Neuroglia
Oligodendrocytes (CNS)
Ependymal Cells (CNS)
Astrocytes (CNS)
Microglia (CNS)
Schwann Cells (PNS)
Satellite Cells (PNS)
Oligodendrocytes
CNS, Forms myelin sheath around axons, insulates nerve fiber from extracellular fluid, speeds signal conduction
Astrocytes
Gives CNS its structure, most abundant glial cell, supportive framework for nervous tissue, regulate blood flow in the brain, regulates nerve growth
Schwann Cells
Oligodendrocytes of the PNS, surrounds axons of neurons in the PNS, forms myeline sheaths, unlike oligodendrocytes the entire cell wraps around the axon, not just the arms
Excitable Cells
Nerve cells and muscle cell; can change membrane potential
Resting membrane potential
Unexcited state (about 70mV), difference in voltage across the membrane, membrane potentials first demonstrated in axons of the giant squid
Current
Flow of electrical charge (driving force for ion movement)
Voltage
Difference in charge; declines with distance from site of stimulation because leaky channels get rid of Na+
Voltmeter
Measures voltage
Reference electrode of the voltmeter is in the
Extracellular fluid
What generates membrane potential?
Selective permeability to ions
What is the membrane most permeable to?
K+
The intracellular fluid has what in respect to ion concentration?
High K+ and Anions
Low Na+ and Cl-
The extracellular fluid has what in respect to ion concentration?
High Na+ and Cl-
Low K+ and Anions
Channels allow
ions to move around based on membrane potential
Anions are
nonpermable
Ions want to move in what direction
from high to low concentrations
Ion pumps help maintain
concentrations of major ions via active transport by counteracting the tendency of Na+ to diffuse in and K+ to diffuse out of the cell (Counteracts leaky channels)
Ex: Na+/K+ ATPase Pump
Membrane potential is proportional to
equilibrium potential of ion with greatest permeability
How is resting membrane potential generated within a living cell?
- Sodium and Potassium gradient across membrane
- Differential permeability of membrane to Na+ and K+
- Na+/K+ ATPase pumps move ions up concentration gradients
Changes in Membrane Potential in response to stimulus
Resting, Depolarization (Increase in Na+), Repolarization, Hyperpolarization(Cl- and K+ moving in), Resting
Graded Potentials
“local potentials”; they can vary in strength/magnitude, produces by stimulus on dendrites or cell body, amplitude proportional to stimulus strength,
Weak v. Strong graded potential determined by
- Number of ion channels
- Distance the current spreads
- Threshold
Excitatory Electrical Change
Stimulus opens Na+ channels (depolarization); Takes it closer to threshold
Inhibitory Change
Stimulus opens Cl- or K+ channels (hyperpolarization); further from threshold
Action Potentials
- All of none
- Produced by graded potentials
- Always excitatory (depolarization)
- Propagates over long distance without decrease in amplitude
What happens at threshold?
Depolarization (Excitation); Voltage gates Na+ channels open up (Quick to open and close)
What happens at the peak of the AP?
Repolarization; Voltage gated K+ channels open (Slow to open and close) and Na+ channels close
Voltage gates K+ channels
They are slow to open (Causing repolarization) and slow to close (causing hyperpolarization)
Action Potential Stages
Resting Potential, Graded Potentials, Threshold (Voltage Gated Na+ open), Depolarization (Voltage Gated K+ Channels open), Peak Depolarization (Voltage Gated Na+ channels close), Repolarization, Hyperpolarization (Voltage gated K+ channels close), Resting Potential
Refractory Period Phases
Absolute and Relative
Absolute Refractory Period
No AP can be produced because it is above threshold already
Relative Refractory Period
AP can be produced but it is much harder due to hyperpolarization
Conduction Veloctiy
Depends on axon diameter, myelination, temp
Ex: Bigger axon = Bigger conduction velocity; Unmyelinated = Decrease Conduction Velocity
Myelinated Axons conduct
faster
Warmer neurons conduct
faster
Axons with bigger diameters conduct
faster
Myelin sheath does what?
Prevents ion leakage and maintains AP more efficiently
Synaptic transmission can be
electrical or chemical
Myelinated Axons
Saltatory Conduction: AP jumps from 1 node to the next and has no leak channels in myelin sheath
Pre Synaptic Cell
Sending Cell
Post Synaptic Cell
Receiving Cell
Electrical Synaptic Transmission
Rapid response; Rare in humans and mammals; Electrical coupling of cells joined by gap junction
Ex: Crayfish
Electrical Synaptic Transmission
Rapid response; Rare in humans and mammals; Electrical coupling of cells joined by gap junction
Ex: Crayfish
Chemical Synaptic Transmission
Takes longer; most common type; releases secondary messenger; synaptic vesicles
Ex: Common in reflex responses
Function of Chemical Synapse
Pre synaptic action potential opens up VG Ca2+ channels. Ca2+ enter the pre synaptic terminal and trigger vesicles to travel and release neurotransmitters via exocytosis into the synaptic cleft. NT will bind to receptors on the post synaptic cell. Will bind to ionotropic receptors OR metabotropic receptors
Ionotropic Receptors
A single molecule constitutes receptor and ion channel; the receptor directly alters permeability to ions in the post synaptic cell causing depolarization. Binding to the ligand gated channel opens it.
More receptors = greater response
Metabotropic Receptors
Triggers a signaling cascade of second messengers; Have relatively slow and long lasting effects on synaptic processes
NT will bind to G protein coupled receptors that will activate a G protein to produce a second messenger
Excitatory Post Synaptic Potential (ESPS)
Causes depolarization (influx of Na+) and repolarization
Neurotransmitter is acetylcholine (Skeletal muscle cell synapses (PNS)) and glutamate (CNS, Excitatory effect)
Inhibitory Post Synaptic Potential (IPSP)
Causes hyperpolarization (Influx of Cl- of efflux of K+) (making AP harder to achieve)
Neurotransmitter is GABA or glycine
Summation Types
Temporal, Spacial
EPSP Temporal Summation
Adding up post synaptic potentials and responding to their net effect; Intense stimulation by ONE presynaptic neuron
EPSP Spacial Summation
Simultaneous stimulation by SEVERAL pre synaptic neurons
What limits the grades potentials?
Number of receptors and amount of NT released
Neurotransmitters
Chemical messengers released by a nerve signal into the synaptic cleft that bind to the receptor on another cell and alters that cells physiology
3 Categories of NT
- Amines
- Amino Acides
- Neuropeptides
Amines
Acetylcholine (Found in neuromuscular junctions and most synapses of the autonomic nervous systems; Excites skeletal muscle (ESPS ionotropic) and inhibits cardiac muscle (ISPS metabotropic)
More Ex: Epinephrine, norepinephrine, dopamine, histamine
Amino Acids
GABA (IPSP ionotropic)
Glutamate (EPSP ionotropic)
Glycine (IPSP ionotropic)
Neuropeptides
Small chains of amino acids (2-40 aa) (metabotropic)
Model System for Understanding Chemical Synapses
Vertebrate Neuromuscular Junction (Between a motor neuron and skeletal muscle neuron)
Purpose of Junctional Folds
Increase SA to increase the response
What works together (antagonistically) to control overall level of brain excitation?
GABA (IPSP) and Glutamate (EPSP)
An imbalance of GABA and Glutamate can be found in those with
Autism and anxiety disorders (Elevated gluametergic neurotransmission)
Alcohol potentiates sedentary effects of
GABA; Increases GABA/Glu ratio; Sensations of relaxation and at later stages loss of control (slurred speech, unsteady gait, loss of social anxiety)
High levels of GABAergic
Relaxation and sedation
Synaptic Plasticity
Synaptic properties change with time and activity
Thought to be mechanism for how the nervous system function changes over time (memory and learning)
Presynaptically
Changing rate of NT synthesis, storage, and release
Postsynaptically
Sensitivity to NT can be increased or decreased under different circumstances
Synaptic potentials are
short lived (millisecond to second)
Synaptic Strenght
Amplitude of postsynaptic potential in response to presynaptic AP
Facilitation
More sensitive with stimulation; Successive post synaptic potentials increase in amplitude in response to repeated pre synaptic action potentials
Antifacilitation
Dampened with stimulation; Successive post synaptic potential in a series decrease with amplitude
Posttetanic potentiation
extended enhancement of synaptic response
Tetanic stimulation
Very rapid firing of action potentials
Facilitation is pronounced after
tetanic stimulation of pre synaptic neurons
What regions of the brain are associated with learning and memory function?
Hippocampus and Cerebral Cortex
Habituation
Decrease in intensity of reflex response to stimulus
Ex: Getting used to loud noises near house over time
Sensitization
Prolonged enhancement of reflex response to stimulus
Ex: Smell of grandmas house
How does habituation and sensitization occur?
Repeated stimulation causes less NT to be released (Pattern in pre synaptic plasticity)
Resensitivity via 2nd messenger system and serotonin (additional Ca2+ channels)
Long Term Potentiation in Hippocampus
LTP is post synaptic
Tetonic stimulation depolarized the post synaptic cell and casued Mg2+ to be released allowing Ca2+ to enter.
More channels = greater response
Chemical signals act over
short and long distances in the body
Types of signals that travel short and long distances
Neurons, Non neural endocrine cells (Outside of the NS, contained within endocrine glands), Neurosecretory cells (Neural cells that secrete into the bloodstream; Soma cell body stays in the CNS), Local paracrine and autocrine signals
3 Chemical classes of hormones
- Steroid hormones (sex and stress)
- Peptide (protein) hormones
- Amine hormones
Steroid Hormones
Synthesized from cholesterol, sex and stress hormones, lipid soluble (can permeate through lipid bilayer; carrier protein required to travel in bloodstream), receptors located inside target cells (cytoplasm or nucleus; intracellular receptors)
in vertebrate secreted by gonads, adrenal cortex, skin, and placenta
in antropods molting hormone (Ex: ecdysone): regulates exoskeleton shedding
Peptide Hormone
Water soluble (cant easily pass through lipid bilayer, interact through membrane bound receptors), vary in molecular size
in vertebrates: include antidiuretic hormones, insulin, and GH
in invertebrates: gamete shedding hormones (sesastars) and diuretic hormones (insects)
Amine Hormones (modified aa)
Catecholamines (Tyrosine derivative): Dopamine, Norepinephrine, Epinephrine –> H2O soluble
Iodothyronines (Tyrosine derivative): Thyroxine and Triiodothyronine (Thyroid hormones) –> lipid soluble
Melatonin (Tryptophan derivative) –> H2O soluble
Hormones Produce
biochemical changes in target cells
Ex: alter gene expression by altering rates of transcription and translation
3 Receptor types mediate hormone action
- intracellular receptors
- G-Protein cascade membrane receptors
- Enzyme linked membrane receptors
Lipid soluble hormones (steroids and iodothyronines) bind to
intracellular receptors and form hormone receptors complexes
Hormone Receptor Complex
act as transcription factor and interact directly with the cells DNA to alter gene expression –> directly influences protein synthesis of target cell
Process requires time (delay between hormone binding and cellular response)
Water soluble hormones (peptides and catecholamines) bind to
membrane receptors to mediate action by changing membrane permeability or activating second messengers vis G proteins
Control of Endocrine Secretion
Vertebrate Pituitary Gland
2 Major Controls of Hormone Secretion
- Neural control of secretion by neurosecretory cells
- Neurosecretory control of secretion by endocrine cells
Anterior Pituitary
Endocrine Tissue and Non Neural Tissue and endocrine cells provide control of secretion
Posterior Pituitary
Neural Tissue and Neurosecretory Cells provide neural control of secretion
Hypothalamus
Endocrine system control center; CNS is the initial site for control
In most mammals two peptide hormones are released by the Posterior Pituitary
Oxytocin and Vasopressin
Oxytocin
Causes contraction of uterus during birth and ejection of milk from mammary glands
Vasopressin
Anti diuretic hormone; limits the production of urine and constricts arterioles
Water stressed = Increased ADH = Increased H2O retention = Increased Blood Volume
Wounded = Decreased Blood Volume = Increased ADH = Increased Blood Volume via Increased H2O Retention
Hormones of the Anterior Pituitary are synthesized and secreted by
cells in its tissues; all hormones from this site are peptides
Hormones are categorized into 2 groups according to target tissue
- influence non-endocrine tissues
- influence endocrine tissues (topins)
All are secreted by the anterior pituitary in response to signals from the hypothalamus
Hormones influencing non endocrine tissues
TSH (Thyroid), ACTH (Adrenal Cortex), LH (Gonads), FSH (Gonads)
Hormones influencing endocrine tissues (tropins)
MSH (Skin), Prolactin (Mammary Glands), GH (Liver, Muscle, Fat)
Endocrine Control Axis
HPT Axis (Hypothalamus Anterior Pituitary Thyroid Axis)
Ex: TRH –> TSH –> Thyroid Hormones
Secretions of one endocrine gland act on another
HPA Axis
Hypothalamus Pituitary Adrenal Cortex Axis
Illustrates hormone modulation
Modulation of Endocrine Control Pathways
Adrenal Cortex secretes several hormones (Ex: Glucocorticoids)
Glucocorticoids
Steroid hormone secreted by adrenal cortex
They increase glucose concentrations in the blood and are critical for homeostasis
Cortisone, Cortisol, Corticosterone
What activated the release of glucocorticoids
Stress or challenging conditions
Main Glucocorticoid in Primate and Fish
Cortisol
Main Glucocorticoid in Others (Birds, Reptiles, Rodents, Amphibians)
Corticosterone
Modulation of Endocrine Control Pathway
HPA Axis; Pathway modulated by negative feedback
Stress is the stimulus/neural input. Stress increases CRH secretion from the hypothalamus. The anterior pituitary secretes ACTH then the adrenal cortex secretes glucocorticoids. Glucocorticoids exert a negative feedback loop on the anterior pituitary and the hypothalamus to stop secreting ACTH and CRH.
