animal control systems Flashcards
Hormone
in multicellular organisms, one of many types of SECRETED CHEMICALS, that are formed in specialized cells, TRAVEL in body fluids, & ACT on specific target cells’ functioning
- are thus important in long-distance signalling
Steroid
a type of LIPID characterized by a CARBON skeleton consisting of 4 fused rings with various CHEMICAL GROUPS attached
Autocrine system
- when a cell is signally itself (in the nearby vacinity where a cell can shut down or limit its own ability)
and/or - when a cell is signally cells that are communicating with nearby cells of the same type
Paracrine system
like the endocrine system but on a SMALLER level, only cells LISTENING for it NEAR BY can receive it (have a RECEPTOR for it)
- like a smaller radio station
Endocrine system
some gland in body will broadcast signal to every cell BUT only the cells that are LISTENING for it receive it (have to have RECEPTOR for it)
Neuroendocrine
are cells that receive neuronal input (neurotransmitters released by nerve cells or neurosecretory cells) and, as a consequence of this input, release message molecules (hormones) into the blood. … Hormonal effects can last up to ten times longer than those of neurotransmitters.
Neurohormone
a molecule that is SECRETED BY A NEURON, travels in body fluids, & acts on specific target cells, changing their functioning
Receptor
are chemical structures, composed of protein, that RECEIVE and TRANSDUCE signals that may be integrated into biological systems.
Signal transduction
the CONVERSION of STIMULUS ENERGY to a CHANGE IN THE MEMBRANE POTENTIAL of a SENSORY RECEPTOR CELL
Negative Feedback
for many hormones, the response pathway involves NFB:
- a loop in which the response REDUCES the initial stimulus
- AMPLIFIES both stimulus & response
Positive Feedback
REINFORCES a stimulus, leading to an even greater response
- helps RESTORE a preexisting state
Homeostasis
the steady-state physiology condition of the body
Tropic hormone
a hormone that has an ENDOCRINE GLAND or CELLS as a target
Nontropic hormone
are hormones that DIRECTLY stimulate TARGET CELLS to induce effects.
Hormone cascade
1 hormone triggers the production of another hormone, that triggers the production of another hormone
Parathyroid hormone (PTH)
a hormone secreted by the parathyroid glands that raises blood calcium level by promoting calcium release from bone & calcium retention by the kidneys
Oxytocin
a hormone PRODUCED by the HYPOTHALAMUS & RELEASED from the POSTERIOR pituitary
- it induces contractions of the uterine muscles during labour & causes the mammary glands to eject milk during nursing
Insulin
a hormone secreted by pancreatic beta cells that lowers blood glucose levels
- it promotes the uptake of glucose by most body cells & the synthesis & storage of glycogen in the liver & also stimulates protein & fat synthesis
Glucagon
a hormone secreted by pancreatic alpha cells that raises blood glucose levels
- it promotes glycogen breakdown & release of glucose by the liver
Neuron
an impulse-conducting cell in the nervous system
- excitable
- processes input produces output
Sensory Neuron
any neuron that detects a stimulus & communicates it to the nervous system
Interneuron
any neuron that connects 2 other neurons
Motor Neuron
a nerve cell that transmits signals from the brain or spinal cord to muscles or glands
Soma
cell body
Dendrites
input end
- bunch of RECEPTOR molecules on it that detect some kind of input
- sensory receptors for the cell itself, either receive info from ANOTHER NEURON or info from a SENSORY CELL
Axon hillcock
where voltage is summed (& axon potential may or may not form) & sent down axon
The axon hillock acts as something of a manager, summing the total inhibitory and excitatory signals. If the sum of these signals exceeds a certain threshold, the action potential will be triggered and an electrical signal will then be transmitted down the axon away from the cell body.
Axon
a typically LONG extension, or process, of a neuron that carries nerve impulses AWAY from the cell body TOWARD TARGET CELL
- is insulated with myelin sheath
Ion pumps
a transporter is a transmembrane protein that moves ions across a membrane to accomplish many different functions including, cellular communication, maintaining homeostasis, energy production, etc.
Ion channels
a transmembrane protein channel that allows a specific ion to diffuse across the membrane down its concentration or electrochemical gradient
Gated ion channels
- changes in the membrane potential occur b/c neurons contain these
- ion channels that open or close in response to stimuli
Resting membrane potential
the membrane of an INactive neuron - one that is NOT sending a signal
- (-60mv–80mv)
is the voltage across the cell’s membrane when it is at rest (i.e. there’s no graded potential or action potential going on)
- it depends on ALL the equilibrium potentials for all the ions present
Threshold
the potential that an excitable cell membrane must reach for an action potential to be initiated
Action Potential
an action potential is the signal that neurons produce & send
- typically, they are formed when enough Na+ channels open
- different events open these channels on different neurons
- if a depolarization shifts the membrane potential sufficiently, the result is a massive change in membrane voltage (an action potential)
Depolarization
a change in a cell’s membrane potential such that the inside of the membrane is made less negative relative to the outside
EX: a neuron membrane is depolarized if a stimulus decreases its voltage from the RMP (70mV) in the direction of zero voltage
Repolarization
refers to the change in membrane potential that returns it to a negative value just after the depolarization phase of an action potential which has changed the membrane potential to a positive value.
Hyperpolarization
a change in a cell’s membrane potential such that the inside of the membrane becomes more negative relative to the outside
- reduces the chance that a neuron will transmit a nerve impulse
Refractory
the “down time” when a 2nd action potential cannot be initiated
Schwann cells
a type of GLIAL CELL that forms insulating myelin sheath around the axons of neurons in the PNS
Myelin sheath
wrapped around the axons of a neuron, an insulating coat of membrane from Schwann cells or oligodendrocytes
- it is interrupted by nodes of Ranvier, where action potentials are generated
Saltatory conduction
rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of ranvier to another, skipping the myelin-sheathed regions of membrane
Presynaptic cell
The cell that delivers the signal to the synapse
Postsynaptic cell
The cell that will receive the signal once it crosses the synapse
Neurotransmitter definition
a molecule that is released from the synaptic terminal of a neuron at a CHEMICAL synapse, diffuses across the synaptic cleft, & binds to the POSTsynaptic cell, triggering a response
EPSP (excitatory postsynaptic potential)
an electrical charge (DEpolarization) in the membrane of a postsynaptic cell caused by binding of an excitatory neurotransmitter from a presynaptic cell to a postsynaptic receptor; makes it more likely for a postsynaptic cell to generate an action potential
IPSP (inhibitory postsynaptic potential)
an electrical charge (HYPERpolarization) in the membrane of a postsynaptic neuron caused by the binding of an inhibitory neurotransmitter from the presynaptic cell to a postsynaptic receptor; makes it more difficult for a postsynaptic neuron to generate an action
Temporal summation
a phenomenon of neural integration in which the membrane potential of the postsynaptic cell in a chemical synapse is determined by the combined effect of EPSPs or IPSPs produced in rapid succession
Spatial summation
a phenomenon of neural integration in which the membrane potential of the postsynaptic cell is determined by the combined effect of EPSPs or IPSPs produced nearly simultaneously by different synapses
Cephalization
the concentration of sense organs, nervous control, etc., at the anterior end of the body, forming a head and brain, both during evolution and in the course of an embryo’s development.
Ganglion/Brain
- clusters (functional groups) of nerve cell bodies in a centralized nervous system
- organ of the CNS where info is processed & integrated
- in more complex animals
Nerve
a fibre composed primarily of the bundled axons of PNS neurons
Nerve net
a weblike system of neurons, characteristic of radially symmetrical animals, such as hydra
Integration
Stimuli that are received by sensory structures are communicated to the nervous system where that information is processed. This is called integration. Stimuli are compared with, or integrated with, other stimuli, memories of previous stimuli, or the state of a person at a particular time.
Define tropic and non-tropic hormones
Non-tropic hormones are hormones that directly stimulate target cells to induce effects. This differs from the tropic hormones, which act on another endocrine gland. Non-tropic hormones are those that act directly on targeted tissues or cells, and not on other endocrine gland to stimulate release of other hormones.
Compare the basic structure of sensory neurons, interneurons, and motor neurons
sensory neurons: transmit info about external stimuli such as light, touch, or smell, or internal conditions such as blood pressure or muscle tension
interneurons: the vast majority of neurons in the brain are interneurons, which form the local circuits connecting neurons in the brain
motor neurons: neurons that extend out of the processing centres trigger output in the form of muscle or gland activity
- ex: transmit signals to muscle cells, causing them to contract
Explain what an excitable cell is
meaning their voltages can change
- neuron & muscle cells are “excitable”
Compare ion pumps and ion channels
ion pumps: a transporter is a transmembrane protein that moves ions across a membrane to accomplish many different functions including, cellular communication, maintaining homeostasis, energy production, etc.
ion channels: a transmembrane protein channel that allows a specific ion to diffuse across the membrane down its concentration or electrochemical gradient
Discriminate between the three types of ion channels
voltage-gated ion channels open with changes in the membrane potential; ligand gated channels open in response to changes in the concentration of specific signalling molecules; stretch-activated ion channels open in response to changes in cell shape
Explain how action potentials are first generated in neurones
The action potential is an explosion of electrical activity that is created by a depolarizing current. This means that some event (a stimulus) causes the resting potential to move toward 0 mV. … Action potentials are caused when different ions cross the neuron membrane. A stimulus first causes sodium channels to open.
Describe the purpose and mechanism of refractory period
- the “down time” when a 2nd action potential cannot be initiated
- this interval sets a limit on the max frequency at which action potentials can be generated
- also ensures that all signals in an axon travel in 1 direction, from the cell body to the axon terminal
Compare a postsynaptic cell’s responses to excitatory and inhibitory neurotransmitters
if acetylcholine (ACh) binds to an EXCITATORY receptor, it might open Na+ channels on postsynaptic cells - this RAISES the neurons voltage TOWARD threshold
if ACh binds to an INHIBITORY receptor, it might open K+ or Cl- channels
- this LOWERS the neuron’s voltage, making it HARDER to fire
Explain how the central nervous system integrates sensory information and elicits a motor response
- sensory receptor (of some kind)
- sensory input (brought into the black box (brain) - PNS doing connection)
- integration
- motor output - PNS doing connection
- effector cells
*PNS connects the outside world to CNS
Explain the mechanism and purpose of the withdrawal reflex
The withdrawal reflex is a spinal reflex intended to protect the body from damaging stimuli. The reflex rapidly coordinates the contractions of all the flexor muscles and the relaxations of the extensors in that limb causing sudden withdrawal from the potentially damaging stimulus.
Nervous system
has to be a DIRECT LINE in order for 2 cells to communicate (like a telephone)
- opposite of endocrine system
What are the 2 broad classes of hormones?
- Water Soluble
2. Lipid Soluble
What is the WATER soluble class of hormones?
- typically modified peptides or amino acids
- MOST hormones are water-soluble
- water-soluble molecules CAN’T pass through lipid bilayer membrane - b/c they are POLAR
- (ex: cell or nuclear membranes)
- (CAN be stored in vesicles - b/c they can’t pass through a membrane)
- NEED a RECEPTOR molecule
- CAN float freely through the interstitual tissue & through blood (b/c mostly water)
What are examples of WATER soluble hormones?
- growth hormone
- insulin
- leptin
- oxytocin
What is the LIPID soluble class of hormones?
- steriod hormones
- many peptide hormones, most amine (made of amino acids) hormones, all lipid hormones
- lipid-soluble molecules CAN pass through lipid-bilayer cell membrane (& nuclear membrane) (CANNOT be stored in vesicles)
What are examples of LIPID soluble hormones?
- androgens
- estrogens
- progestogens
= sex hormones
In order for hormone delivery…
a gland “broadcasts” a chemical message (ex: secretes hormone)
What is the hormone delivery process for WATER soluble hormones?
- actively removed from secretory cells
- must bind to surface receptor molecule on target cells
What is the hormone delivery process for LIPID soluble hormones?
- hormone just floats out of secretory cell
- MUST be bound to carrier protein to become water-soluble
- just floats into target cell
Lipid-soluble hormones don’t have to be actively exported into the interstitial fluid because…
they just flow through following concentration gradients out of the cell & into the interstitial fluids, can leak into blood but need transport proteins (carrier proteins)
- b/c they are not water soluble (can’t dissolve any blood so attach to carrier molecules that makes it water soluble, then it can dissolve in blood & flow in blood like water-soluble)
What makes the WATER soluble hormone go from interstitial fluid into the bloodstream for instance?
it’s following the CONCENTRATION GRADIENT!!!
- when it is dumped into the interstitial fluid there is a bunch of hormone there & not in the blood so it will leak into the blood vessel
- it will flow the concentration gradient down into the blood vessel
- & other places in the body they follow the concentration gradient out of the blood & into the interstitial fluid & find receptor molecule
What is the signal transduction process for WATER soluble hormones?
- receptor molecules are typically GPCRs (G protein-coupled receptor)
- do secondary messenger system, bind to the receptor molecule which sends a G protein along the cell membrane to activate other membrane receptor molecules that sends secondary messenger molecules into the cell to do various things like gene expression, modify proteins etc.
ex: stress response
- do secondary messenger system, bind to the receptor molecule which sends a G protein along the cell membrane to activate other membrane receptor molecules that sends secondary messenger molecules into the cell to do various things like gene expression, modify proteins etc.
What is the signal transduction process for LIPID soluble hormones?
- NO receptor molecule on target cell membrane (b/c flows right through)
- hormone typically binds to free-floating receptor in cytoplasm
- hormone-receptro complex floats into nucleus
- acts as transcription factor
ex: vitellogenin upregulation
Why are brains described as a “black box”?
produces specific output for specific input
ex: when a mosquito lands on you, you sqat it, and don’t have to know what is going on in your brain in order to know what will happen
The PNS & the CNS are both ectoderm but…
arise from different parts
- CNS comes from neural tube
- PNS comes from neural crest cells (develop independently)
Sensory input
stimulus observed
Motor output
any nervous system output (muscle movement, gland secretion, etc)
Effector cell
any neuron that produces motor output (including muscle cells)
Central Nervous System
the brain & spinal cord; information processing occurs here
Peripheral Nervous System
all other neurons; the PNS connects the CNS to the sensory & effector cells (& thus to the outside world)
- connects brain to outside world
A reflex arc
ex of a black box (an input-output circuit)
- something happens & you reflexively produce an output (no thought, no mediation, no learning, can’t control it, automatic)
WHOLE PROCESS IN SPINAL CORD (not in brain)
What is the process for the reflex arc?
- your tendon is pulled, stretching the quadriceps above
- stretch receptors in your quadriceps are activated & send a signal to a ganglion in the spinal cord
- “thinking” your lower leg just moved inward, the cell activates 2 other cells
- the 1st is a motor neuron that causes the quadriceps to contract
- the 2nd is an inhibitory interneuron
- the motor neuron controlling the hamstring is thus inhibited
- with the quadriceps activated & the hamstring inhibited, the lower leg suddenly extends
- b/c the tendon is stretched only briefly, the action ends as quickly as it began