Exam 1 Flashcards
integrated study of how biological systems work
- integrates knowledge from all levels of biological organization
animal physiology
what are the 2 main questions physiologists seek out about how an animal works?
- What is the mechanism by which a function is accomplished?
- What is the origin of that function?
components of living organisms that enable animals to perform
mechanism
the evolutionary processes that conspired to produce a mechanism.
- the evolutionary significance of mechanisms
origin
_______ ______ is a key process of evolutionary origin
natural selection
increases in frequency of genes that produce phenotypes that raise the likelihood that animals will survive and reproduce
- occurs within populations. it is not an individual level phenomenon. Individuals don’t evolve, populations do
natural selection
traits (or physiological mechanisms) that are products of evolution by natural selection
adaptation
What are the modes of natural selection?
- directional selection
- stabilizing selection
- disruptive selection
most cells of an organism are exposed to the _______ environment not the _______ environment
- internal
- external
the _____ environment may be permitted to change when the _____ environment changes, or it may be kept constant
- internal
- external
what are the levels of biological organization?
- atom
- molecule
- organelles
- cells
- tissues
- organ
- organ system
- organism
how an animal moves in that environment
biomechanics
______ also depends on how they move and the different capabilities they have
morphology
what are 2 parameters associated with a bell curve?
- mean
- standard deviation (SD)
what mode of natural selection is: certain groups of phenotypes that are favored by natural selection OR a group of phenotypes that are disfavored by natural selection.
- shift in mean phenotype
- thought to be quite common
mean: change variance: no change
directional selection
which mode of selection is: stabilizing the phenotype around the current mean
- mean is maintained, variance decreased
- is fairly common
stabilizing selection
which mode of natural selection is: variance is often increased, and the mean may or may not change
- is rare
disruptive selection
who was the first to recognize the stability of conditions humans maintain in their blood.
Claude Bernard
What was Claude Bernard’s principal area of study?
blood glucose levels
introduced an important term referring to “internal constancy”
Walter Cannon
homeostasis
- internal stability
- the existence of regulatory mechanisms to make adjustments to maintain stability
- internal body temperature of 26-28ºC
What were Walter Cannon’s 3 postulates?
- Nervous system preserves the normal conditioning of the body.
- The tonic activity if a system can be modulated up & down.
- There are factors that have opposing effects=antagonist controls
What area of the brain is there a thermostat that activates cooling/warming mechanisms
Hypothalamus
Negative Feedback
Positive Feedback
snowball effect. Not bringing anything back to homeostasis at all. (Ex. oxytocin signaling during mammalian birth of offspring)
Physiological timescales
timeframes in which physiology changes
- Acute (immediate)
- Chronic (long-term, after a few days or weeks of exposure)
changes in individuals
Evolutionary
changes in populations
Phenotypic plasticity
the ability of an individual animal to express two or more genetically controlled phenotypes
isometric growth
-proportions remain constant
- each dimension is scaled up or down by same amount
allometric growth
-changes in body proportions with changes in body size
- different rates of growth of different parts
- the proportions vary depending on the rates at which SA, volume, & other physical parameters change with size
Scaling
the structural & functional consequences of changes in size of otherwise similar organisms
For geometrically similar objects:
- SA is proportional to LENGTH^2
- V is proportional to LENGTH^3
- SA is proportional to V^2/3
SA:V ratio
Smaller objects have larger SA relative to their volume than larger objects of the same shape (i.e. they have larger SA:V ratios)
- benefit & curse-larger surface area relative to volume means quicker diffusion
- good for something like O2 absorption, bad for water loss
How does the endocrine system communicate?
By endocrine cells into the bloodstream
- much slower but response is prolonged more
Neuron
basic unit (specialized cells) of the nervous system
Nervous system
neurons & their support cells (glial cells)
Sensory (afferent) neurons
conduct signals from receptors to the CNS
Interneurons (associations neurons)
are confined to the CNS
Motor (efferent) neurons
conduct signals from the CNS to effectors’ such as muscles & glands (PNS)
What are the 5 functional regions of the neuron?
- cell body (soma)
- Dendrites
- Axons
- Axon hillock
- Axon Terminal
What are the functions of neuroglia (glial cells)
Protect neurons & help them function
- Insulate neurons from one another
- Supportive framework for nervous tissue
- involved in impulse transmission (communication)
What are the 6 type of glial cells and where are they found?
- Oligodendrocytes (CNS)
- Ependymal cells (CNS)
- Microglia (CNS)
- Astrocytes (CNS)
- Schwann cells (PNS)
- Satellite cells (PNS)
Oligodendrocytes
- forms myelin sheath around axons
- insulates nerve fiber from extracellular fluid
- speeds signal conduction
Astrocytes
- most abundant glial cells…numerous functions
- supportive framework for nervous tissue
- regulate blood flow in brain
- regulate nerve growth
Schwann cells
- found only in PNS
- surround axons of neurons in PNS (form myelin sheath here-similar to oligodendrocytes in CNS)
How is membrane potential measured?
measured outside relative to inside
How do nerve cell function?
Excitable cells
- can change membrane potential
Resting membrane potential (RMP)
- the “unexcited” state
- difference in voltage across the membrane
- membrane potentials first demonstrated in axons of the giant squid ( 1mm diameter)
What does intracellular fluid have?
- low Na+ & Cl-
- high K+ & nonpermeable anions (A-)
What maintains the RMP?
Na+/K+ ATPase pump which moves ions against their concentration gradient
How is a RMP generated within a living cell?
- Na+ & K+ gradients across membrane
- Differential permeability of membrane to Na+ & K+
- Na-K ATPase pumps move ions up concentration gradients
Depolarization
is a decrease in the absolute value of the membrane potential toward zero (becoming less negative inside the cell)
Hyperpolarization
is an increase in the absolute value of the membrane potential away from zero (becoming more negative inside the cell)
Repolarization
goes back to RMP
Graded potentials
- “local” potentials
- produced by stimulus on dendrites or cell body
- amplitude is proportional to stimulus strength
- leads to an AP
weak vs. strong stimulus depends on…
- # of ion channels
- distance current spreads
- threshold
Which ions influence each function?
-Excitatory: stimulus open Na+ channels (depolarized)
-Inhibitory: stimulus opens K+ or Cl- channels (hyperpolarized)
Action Potential (AP) is:
- all or none
- produced by graded potentials
- always excitatory
- propagates over long distance without decrease in amplitude
- goes in one direction
Absolute Refractory Period
No AP can be produced
Relative Refractory Period
AP can be produced by not easily
The speed of the signal on:
- Axon diameter
- myelination
- temperature
In a myelinated axon, the voltage gated channels are located in:
Nodes of Ranvier
In a myelinated axon:
- can travel much farther at a higher level
- salatory conduction
What are the 2 types of synaptic transmission?
- Electrical
- Chemical
doesn’t have a synaptic cleft. pre & post neurons are touching each other by gap junctions
electrical
NT are transmitted to release in synaptic cleft into the post neurons
chemical
Electrical synapse:
-very rapid response
- electrical coupling of cells joined by gap junction
What’s the most common synapse?
Chemical
Ionotropic Receptor
- A single molecule constitutes receptor & ion channel
- The receptor directly alters permeability to ions in post-synaptic cell which causes depolarization
- receptor is also a Na+ channel & a receptor binds to it
Metabotropic receptors:
- trigger a signaling cascade of second messengers.
- have a relatively slow, long lasting effects on synaptic processes.
- GPCR, G protein –> effector
Post-synaptic potentials:
- EPSP: causes depolarization (Na+)
- IPSP: causes hyperpolarization (Cl- & K+)
Temporal Summation:
-1 neuron that’s rapidly firing AP onto post-synaptic neuron
- can be EPSPs or IPSPs
Spatial Summation:
- multiple pre-synaptic neurons acting on one post-synaptic neuron
- can be EPSPs or IPSPs
What happens during a EPSP?
- cell is depolarized (Na+ channels open)
- NT is Ach or Glutamate
What happens during IPSP?
- hyperpolarization (K or Cl- channels open)
- NT is GABA or glycine
What is EPSP summation?
- adding up post-synaptic potentials & responding to their net effect
Neurotransmitters:
- chemical messengers released by a nerve signal into synaptic cleft that bind to receptor on another cell & alters that cell’s physiology
- more than 100 identified
What are the 3 categories of NT:
- Amines
- Amino acids
- Neuropeptides
What is the main type of amine NT and what does it do? What are other types of amine NT?
- found in neuromuscular junction & most synapses of the autonomic nervous system
- Excites skeletal muscle- EPSP (ionotropic)
- Inhibits cardiac muscle - IPSP (metabotropic)
- Other types: epinephrine, norepinephrine, dopamine, & histamine
What are the type of amino acid NT? Are they excitatory or inhibitory?
- GABA (gamma-aminobutyric acid)-IPSP (Ionotropic)
- Glutamate - EPSP (ionotropic)
- Glycine - IPSP (Ionotropic)
Neuropeptides:
small chains of amino acids (2-40 amino acids) - Metabotropic
What 2 NT’s work together (antagonistically) to control overall level of brain excitation
GABA & glutamate
An elevated &/or imbalance of glutamatergic neurotransmission can causes what disorders?
- anxiety disorders
- autism spectrum
High levels of what NT can cause relaxation & sedation?
GABA
What does alcohol do to the effects of GABA?
- Increases GABA/glutamate ratio
- sensations of relaxation, later stages loss of control (slurred speech, unsteady gait, loss of social anxiety)
What’s the most abundant excitatory NT in the brain
Glutamate
What are the 3 major classes of receptors?
- AMPA (ionotropic & excitatory)
- NMDA (Ionotropic & Cl- channels)
- metabotropic receptors
All critically important for cognitive functions (learning & memory)
Synaptic Plasticity:
- synaptic properties change with time & activity
- changes of nervous system function during development or learning are thought to reflect synaptic plasticity
- thought to be mechanism for how nervous system for how nervous system function changes over time.
- often time they change with repeated stimulation
Change in synapse can happen in 2 different ways:
- presynaptically: changing rate of NT synthesis, storage, & release
- postsynaptically: sensitivity to NT can be increased or decreased under different circumstances
- receptor driven
Synaptic Strength:
amplitude of postsynaptic potential in response to presynaptic AP
Facilitation:
successive PSPs increase in amplitude in response to repeated presynaptic action potentials
Antifacilitation:
successive PSPs in a series decrease in amplitude.
Habituation:
decrease in intensity of reflex response to stimulus
Tetanic stimulation:
extremely rapid stimulation
posttetanic potentiation:
extended enhancement of synaptic response
- facilitation pronounced after tetanic stimulation of presynaptic neurons
- process happens in hippocampus & cerebral cortex of vertebrate brain
Sensitization:
- prolonged enhancement of reflex response to stimulus
How does habituation occur?
- Ca2+ channels become inactive & less NT release (presynaptic form of synaptic plasticity)
How does sensitization occur?
- we can restore function of those Ca2+ channels
- they have an effect of repolarization of that membrane by altering K+ channels & it extends the length of the AP therefore
- (presynaptic form of synaptic plasticity) a type of synaptic plasticity that modifies the amount of NT released
Long-term Potentiation (LTP):
- post-synaptic response of synaptic plasticity
- involved in long term memory/response
- Ca2+ functions to recruit and lay down new AMPA receptors. Now, the following presynaptic stimulus, you have more receptors for them to respond. In addition to that, the dendritic spine also gets bigger.
